数据通信 毕业论文外文文献英文翻译

数字通信英文作文英文：As a communication AI, I have a lot to say aboutdigital communication. Digital communication refers to the use of electronic devices and technology to transmit information and messages. It has become an integral part of our daily lives, from sending emails to texting friends and family. There are two main types of digital communication: synchronous and asynchronous.Synchronous communication refers to communication that happens in real-time, such as video conferencing or instant messaging. Asynchronous communication, on the other hand, refers to communication that occurs over a period of time, such as email or social media messaging.One of the benefits of digital communication is its convenience. It allows us to communicate with people from all over the world, anytime and anywhere. It has also madecommunication faster and more efficient, as we can send messages instantly and receive responses quickly.However, digital communication also has its downsides. It can be impersonal and lack the emotional connection that face-to-face communication provides. It can also lead to miscommunication, as tone and context can be misinterpreted in written messages.Overall, digital communication has revolutionized the way we communicate and has made our lives easier in many ways. However, it's important to remember the importance of face-to-face communication and to use digital communication responsibly.中文：作为一名交流型AI，我对数字通信有很多看法。

通信外文翻译外文文献英文文献及译文通信外文翻译外文文献英文文献及译文Communication SystemA generalized communication system has the following components:(a) Information Source. This produces a message which may be written or spoken words, or some form of data.(b) Transmitter. The transmitter converts the message into a signal, the form of which is suitable for transmission over the communication channel.(c) Communication Channel. The communication channel is the medium used transmit the signal, from the transmitter to the receiver. The channel may be a radio link or a direct wire connection.(d) Receiver. The receiver can be thought of as the inverse of the transmitter. Itchanges the received signal back into a message and passes the message on to its destination which may be a loudspeaker，teleprinter or computer data bank.An unfortunate characteristic of all communication channels is that noise is added to the signal. This unwanted noise may cause distorionsof sound in a telephone, or errors in a telegraph message or data.Frequency Diversion MultiplexingFrequency Diversion Multiplexing(FDM) is a one of analog technologies. A speech signal is 0~3 kHz, single sideband amplitude (SSB) modulation can be used to transfer speech signal to new frequency bands,four similar signals, for example, moved by SSB modulationto share the band from 5 to 20 kHz. The gaps between channels are known as guard spaces and these allow for errors in frequency, inadequate filtering, etc in the engineered system.Once this new baseband signal, a "group" of 4 chEmnels, has been foimed it ismoved around the Lrunk network as a single unit. A hierarchy can be set up withseveral channels fonning a "group". several groups a "supergroup" and several"supergraup" eicher a "nmsrergroup" or "hypergroup".Groups or supergroups are moved around as single units by the communicationsequipment and it is not necessary for the radios to know how many channels are involved. A radio can handle a supergroup provided sufficient bandwidth is available. The size of the groups is a compromise as treating each channel individually involves far more equipment because separate filters, modulators and oscillators are required for every channel rather than for each group. However the failure of one module will lose all of the channels associated with a group.Time Diversion MultiplexingIt is possible, with pulse modulation systems, to use the between samples to transmit signals from other circuits. The technique is knownas time diversion multiplexing (TDM). To do this, it is necessary to employ synchronized switches at eachend of the communication links to enable samples to be transmittedin turn, from each of several circuits. Thus several subscribers appear to use the link simultaneously. Although each user onlyhas periodic short time slots, the original analog signals between samples can be reconstituted at the receiver.Pulse Code ModulationIn analog modulation, the signal was used to modulate the amplitude or frequency of a carrier, directly. However, in digital modulation a stream of pulse, representing the original，is created. This stream is then used to modulate a carrier or alternatively is transmitted directly over a cable. Pulse Code Modulation (PCM) is one of the two techniques commonly used.All pulse systems depend on the analog waveform being sampled at regular intervals. The signal created by sampling our analog speech input is known as pulse amplitude modulation. It is not very useful in practice but is used as an intermediate stage towards forming a PCM signal. It will be seen later that most of the advantages of digital modulation come from the transmitted pulses having two levels only, this being known as a binary system. In PCM the height of each sample is converted into a binary number. There are three step in the process of PCM: sampling, quantizing and coding.Optical Fiber CommunicationsCommunication may be broadly defined as the transfer of information from one point to another. When the information is to be conveyed over any distance acommunication system is usually required. Within a communication system the information transfer is frequently achieved by superimposing or modulating the information on to an electromagnetic wave which acts as a carrier for the informationsignal. This modulated carrier is then transmitted to the required destination where it is received and the originalinformation signal is obtained by demodulation. Sophisticated techniques have been developed for this process by using electromagnetic carrier wavesoperating at radio frequencies as well as microwave and millimeter wave frequencies. However，拻 communication?may also be achieved by using an electromagneticcarrier which is selected from the optical range of frequencies.In this case the information source provides an electrical signal to a transmitter comprising an electrical stage which drives an optical source to give modulation of the light-wave carrier. The optical source which provides the electrical-optical conversion may be either a semiconductor laser or light emitting diode (LED). The transmission medium consists of an optical fiber cable and the receiver consists of an optical detector which drives a further electrical stage and hence provides demodulation optical carrier. Photodiodes (P-N, P-I-N or avalanche) and , in some instances,phototransistor and photoconductors are utilized for the detection of the optical signal and the electrical-optical conversion. Thus there is a requirement for electrical interfacing at either end of the optical link and at present the signal processing is usually performed electrically.The optical carrier may be modulated by using either an analog or digital information signal. Analog modulation involves the variation of the light emitted from the optical source in a continuous manner. With digital modulation, however, discrete changes in the light intensity are obtained (i.e. on-off pulses). Although often simpler to implement, analog modulation with an optical fiber communication system is lessefficient, requiring a far higher signal to noise ratio at the receiver than digital modulation. Also, the linearity needed for analog modulation is not always provided by semiconductor optical source, especially at high modulation frequencies. For thesereasons，analog optical fiber communications link are generally limited to shorter distances and lower bandwidths than digital links.Initially, the input digital signal from the information source is suitably encoded for optical transmission. The laser drive circuit directly modulates the intensity of the semiconductor laser with the encoded digital signal. Hence a digital optical signal is launched into the optical fiber cable. The avalanche photodiode detector (APD) is followed by a fronted-end amplifier and equalizer orfilter to provide gain as well as linear signal processing and noise bandwidth reduction. Finally, the signal obtained is decoded to give the original digital information.Mobile CommunicationCordless Telephone SystemsCordless telephone system are full duplex communication systems that use radio to connect a portable handset to a dedicated base station，which is then connected to a dedicated telephone line with a specific telephone number on the public switched telephone network (PSTN) .In first generation cordless telephone systems5(manufactured in the 1980s), the portable unit communications only to the dedicatedbase unit and only over distances of a few tens of meters.Early cordless telephones operate solely as extensiontelephones to a transceiver connected to a subscriber line on the PSTN and are primarily for in-home use.Second generation cordless telephones have recently been introduced which allowsubscribers to use their handsets at many outdoor locations within urban centers such as London or Hong Kong. Modern cordless telephones are sometimes combined with paging receivers so that a subscriber may first be paged and then respond to the pageusing the cordless telephone. Cordless telephone systems provide the user with limited range and mobility, as it is usually not possible to maintain a call if the user travels outside the range of the base station. Typical second generation base stations provide coverage ranges up to a few hundred meters.Cellular Telephone SystemA cellular telephone system provides a wireless connection to the PSTN for any user location within the radio range of the system.Cellular systems accommodate alarge number of users over a large geographic area, within a limited frequency spectrum. Cellular radio systems provide high quality service that is often comparable to that of the landline telephone systems. High capacity is achieved by limiting the coverage of each base station transmitter to a small geographic area called a cell so that the same radio channels may be reused by another base station located some distance away. A sophisticated switching technique called a handoff enables a call to proceeduninterrupted when the user moves from one cell to another.A basic cellular system consists of mobile station, basestations and a mobile switching center (MSC). The Mobile Switching Center is sometimes called a mobiletelephone switching office (MTSO), since it is responsible for connecting all mobiles to the PSTN in a cellular system. Each mobilecommunicates via radio with one of the base stations and may be handed-off to any number of base stations throughout the duration of a call. The mobile station contains a transceiver, an antenna, and control circuitry，and may be mounted in a vehicle or used as a portable hand-held unit. Thebase stations consists of several transmitters and receivers which simultaneously handlefull duplex communications and generally have towers which support several transmitting and receiving antennas. The base station serves as a bridge between all mobile users in the cell and connects the simultaneous mobile calls via telephone lines or microwave links to the MSC. The MSC coordinates the activities of all the base stations and connects the entire cellular system to the PSTN. A typical MSC handles 100000 cellular subscribers and 5000 simultaneous conversations at a time, and accommodates all billing and system maintenance functions, as well. In large cities, several MSCs are used by a single carrier.Broadband CommunicationAs can be inferred from the examples of video phone and HDTV, the evolution offuture communications will be via broadband communication centered around video signals. The associated services make up a diverse set of high-speed and broadband services ranging from video services such as video phone，video conferencing，videosurveillance, cable television (CATV) distribution, and HDTV distribution to the high-speed data services such as high-resolution image transmission, high-speed datatransmission, and color facsimile. The means of standardizing these various broadbandcommunication services so that they can be provided in an integrated manner is no other than the broadband integrated services digital network (B-ISDN). Simple put, therefore, the future communications network can be said to be a broadband telecommunicationsystem based on the B-ISDN.For realization of the B-ISDN, the role of several broadband communicationtechnologies is crucial. Fortunately, the remarkable advances in the field of electronics and fiber optics have led to the maturation of broadband communication technologies.As the B-ISDN becomes possible on the optical communication foundation, the relevant manufacturing technologies for light-source and passive devices and for optical fiberhave advanced to considerable levels. Advances in high-speed device and integratedcircuit technologies for broadband signal processing are also worthy of close attention. There has also been notable progress in software, signal processing, and video equipment technologies. Hence, from the technological standpoint, the B-ISDN hasfinally reached a realizable state.On the other, standardization activities associated with broadband communication have been progressing. TheSynchronous Optical Network (SONET) standardization centered around the T1 committee eventually bore fmit in the form of the Synchronous Digital Hierarchy (SDH) standards of the International Consultative Committee in Telegraphy and Telephony (CCITT), paving the way for synchronous digital transmission based on optical communication. The standardization activities of the 5integrated services digital network (ISDN), which commenced in early 1980s with the objective of integrating narrowband services, expanded in scope with the inclusion of broadband services, leading to the standardization of the B-ISDN in late1980抯and establishing the concept of asynchronous transfer mode (ATM)communication in process. In addition, standardization of various video signals is becoming finalized through the cooperation among such organizations as CCITT, the International Radio-communications Consultative Committee (CCIR), and theInternational Standards Organization (ISO), and reference protocols for high-speedpacket communication are being standardized through ISO, CCITT, and the Institute of Electrical and Electronics Engineer (IEEE).Various factors such as these have made broadband communication realizable.5Therefore, the 1990s is the decade in which matured broadband communicationtechnologies will be used in conjunction with broadband standards to realize broadband communication networks. In the broadband communication network, the fiber opticnetwork will represent the physical medium for implementing broadband communication, while synchronous transmission will make possible the transmission of broadband service signals over the optical medium. Also, the B-ISDN will be essentialas the broadband telecommunication network established on the basis of optical medium and synchronous transmission and ATM is the communication means that enables the realization of the B-ISDN. The most important of the broadband services to be providedthrough the B-ISDN are high-speed data communication services and videocommunication services.Image AcquisitionA TV camera is usually used to take instantaneous images and transform them into electrical signals, which will be further translated into binary numbers for the computer to handle. The TV camera scans oneline at a time. Each line is further divided into hundreds of pixels. The whole frame is divided into hundreds (for example, 625) of lines.The brightness of a pixel can be represented by a binary number with certain bits, for example, 8 bits. The value of the binary number varies from 0 to 255, a range great enough to accommodate all possible contrast levels of images taken from real scene.These binary numbers are sorted in an RAM (it must have a great capacity) ready for processing by the computer.Image ProcessingImage processing is for improving the quality of the imagesobtained. First, it is necessary to improve the signal-to-noise ratio. Here noise refers to any interference flaw or aberation that obscure the objects on the image. Second, it is possible to improve contrast, enhance sharpness of edges between images through various computational means.Image AnalysisIt is for outlining all possible objects that are included in the scene. A computer program checks through the binary visual informationin store for it and identifies specific feature and characteristics of those objects. Edges or boundaries are identifiablebecause of the different brightness levels on either side of them. Usingcertain algorithms, the computer program can outline all possible boundaries of the objects in the scene. Image analysis also looks for textures and shadings between lines.Image ComprehensionImage Comprehension means understanding what is in a scene. Matching the prestored binary visual information with certain templates which represent specific objects in a binary form is technique borrowed from artificial intelligence, commonly referred to as "templeite matching"emplate matching? One by one,the templates are checked against the binary information representing the scene. Once a match occurs, an object is identified. The template matching process continues until all possible objects in the scene have been identified, otherwise it fails.通信系统一般的通信系统由下列部分组成:信源。

Multi-Code TDMA (MC-TDMA) for Multimedia Satellite Communications用于多媒体卫星通信的MC--TDMA（多码时分多址复用）R. Di Girolamo and T. Le-NgocDepartment ofa Electricl and Computer Engineering - Concordia University1455 de Maisonneuve Blvd. West, Montreal, Quebec, Canada, H3G 1M8 ABSTRACT摘要In this paper, we propose a multiple access scheme basedon a hybrid combination of TDMA and CDMA,在这篇文章中，我们提出一种基于把时分多址复用和码分多址复用集合的多址接入方案。

referred toas multi-code TDMA (MC-TDMA). 称作多码—时分多址复用The underlying TDMAframe structure allows for the transmission of variable bitrate (VBR) information,以TDMA技术为基础的帧结构允许传输可变比特率的信息while the CDMA provides inherentstatistical multiplexing.和CDMA提供固有的统计特性多路复用技术The system is studied for a multimediasatellite environment with long-range dependentdata traffic,and VBR real-time voice and video traffic研究这个系统是为了在远程环境下依赖数据传输和可变比特率的语音和视频传输的多媒体卫星通信系统 . Simulationresults show that with MC-TDMA, the data packetdelay and the probability of real-time packet loss can bemaintained low. 仿真结果表明：采用MC-TDMA的多媒体卫星通信，数据包延时和实时数据丢失的可能性可以保持很低。

ABSTRACTIn this paper, we present a system using an Android smartphone that collects, displays sensor data on the screen and streams to the central server simultaneously. Bluetooth and wireless Internet connections are used for data transmissions among the devices. Also, using Near Field Communication (NFC) technology, we have constructed a more efficient and convenient mechanism to achieve an automatic Bluetooth connection and application execution. This system is beneficial on body sensor networks (BSN) developed for medical healthcare applications. For demonstration purposes, an accelerometer, a temperature sensor and electrocardiography (ECG) signal data are used to perform the experiments. Raw sensor data are interpreted to either graphical or text notations to be presented on the smartphone and the central server. Furthermore, a Java-based central server application is used to demonstrate communication with the Android system for data storage and analysis.1INTRODUCTIONMobile communication devices are designed to achieve multiple purposes but mostly are focused on voice and short messaging services. Wireless technology has the benefit of improving data mobility, using different protocols such as Wi- Fi and Bluetooth. In the medical field, many studies introduced body sensor networks (BSN) for healthcare applications. BSN improves the patient’s monitoring system with the help of the modern technology. This can be done by various wearable sensors equipped with wireless capabilities, In addition, as seen in various researches, it is desirable to develop a low power system. Different types of sensors can be used for monitoring movements, temperature changes, heart-beat, blood pressure and more to establish a patient monitoring system. Bluetooth is one of the widely available options for managing wireless networks to simultaneously connect up to 7 ancillary devices.In this paper, we introduce a microcontroller system that communicates via Bluetooth with the smartphone for data collections, and streams data simultaneously to the central server for data storage and analysis via the Internet. This system provides a solution for mobile patients by forming a wireless BSN in Bluetooth and Wi-Fi/cellular Internet connections with a common Android smartphone which can monitor the patient status via wireless data transmission.2SYSTEM DESIGNFigure 1 represents the Mobile Sensor Data Collector that involves Bluetooth, Near Field Communication (NFC) and wireless Internet connections for collecting, streaming, storing and analyzing sensor data in real-time. Three different sensors transfer sampled data to the MSP430BT5190 which communicate with the CC2560 Bluetooth transmitter via UART and sends data to a smartphone using the Android and Bluetooth system. On the phone, it displays received data on the screen and streams to the server for storage and data analysis. The term “real-time” in this paper is used to express that data transfers are achieved without perceivable delays among the devices. Also, since the Android system is capable of running application software in the background mode, the application used in this paper has the ability to transfer data during a phone call.Figure 1Overall Design of Mobile Sensor Data CollectorA Java-based UDP server application is used to collect data sent from the smartphone via the Internet. When receiving data from the smartphone, the server application displays and saves all received data to a text file for later analysis. For experimental purposes, this server was implemented with an ordinary desktop to demonstrate our fundamental idea. Also, UDP protocol was chosen over TCP because UDP usually achieves faster transmission than the TCP protocol by not waiting for an acknowledgment signal back to the origin.3EXPERIMENT RESULTSAs shown in Figure 1, all experiments are initiated using an NFC tagging process to start the Android application and initiate the Bluetooth connection automatically. In this particular smartphone, the NFC tag reader is located on the backside. The user needs to tap on the NFC tag as shown in Figure 2 to run the program. The NFC tag containing theBluetooth MAC address of the CC2560 Bluetooth device is attached to demonstrate where the tag should be located.Figure 2Initiating connection processUp to 7 ancillary sensor nodes can be simultaneously connected to the Android system. However, a single sensor Bluetooth connection was employed for testing purposes.3.1Accelerometer Data CollectionIn this paper, the Android 2.3.3 and 4.0.3 operating systems are tested using Google Nexus S to display collected data and stream data to the server. The design of the new system is achieved first by collecting sensor data from the MSP430BT5190, transferred via the CC2560 Bluetooth transmitter. Then, the Bluetooth transmitter sends data to the smartphone, which displays the collected data in real-time. As an example, Figure 3(a) shows the accelerometer data collected and displayed on the smartphone in text and Figure 3(b) shows the data in the graphical notation.Figure 3Received real-time acceleration data display(a) text notation;(b) graphical notationThese data are being sent to the central server either via Wi-Fi or cellular networks for storage and analysis at the same time. Figure 4 shows the received data from the smartphone displayed on the server. The server also saves data to a text file in the designated directory for data analysis.Figure 4Received real-time acceleration data on server An axis value representation depends on the raw sensor data and this raw data could differ from the sensors. There are 3 axes provided from the sensor and each set of data needs to be interpreted. For this particular device used in this paper, x- axis data between -60 and -50 represents LEFT, between +50 and +60 represents RIGHT. This rule applies similarly to the other two axes. This differs from other sensors where the data output of acceleration is normally represented in terms of m/s2. However, a translation algorithm shares the same idea. Figure 5 is the result of translating the accelerometer data based on accelerometer movements.Figure5Accelerometer data translationThis type of the accelerometer translation was extended to the Snake Game sample provided by Android Developers [9]. The original game uses touch screen inputs to control the snake. The touch screen inputs were replaced by accelerometer movements to provide data in LEFT, RIGHT, UP and DOWN. The data analysis was done on the phone itself for test purposes. Figure 6 shows the movement of the snake on the phone that is controlled by accelerometer data from the MSP430 eZ430-RF2560.Figure 6Remote controlling Snake GameThis example emphasizes that accelerometer data can be adapted for the patientmovement detection system. Multiple accelerometers could be implemented to produce more advanced movement analysis.3.2Temperature Sensor Data CollectionA temperature sensor monitoring the real-time room temperature is used to perform the experiment. The procedure of the experiment resembles the previous section but with the different data interpretation. In this particular experiment, a heat gun was used to heat up or cool down the sensor for testing purposes as shown in Figure 7. Similar to the previous accelerometer application, Figure 8(a) shows the text notation of the received data in real-time and Figure 8(b) shows the graphical notation of the received data in real-time. Particularly in the graphical notation output, we provide a warning message if the temperature exceeds more than 35 degrees Celsius. Also, the graphical notation has a range of between 0 degrees Celsius to 50 degrees Celsius for this demonstration.Figure 9 shows the server displaying the received data from the smartphone. It delivers similar outputs compared to the accelerometer demonstration and also saves it to a text file.Figure 7Testing temperature sensor data transmissionFigure 8Received real-time temperature data display(a) text notation;(b) graphical notationFigure 9Received real-time temperature data on server3.3Electrocardiography (ECG) Data CollectionThe ECG signal is an important part of a patient monitoring system. Currently, ECG machines are dependent on wired connections which limit their data mobility. Our system using the Bluetooth protocol for ECG signal collections greatly enhances the mobility. This ECG signal is also sent simultaneously to the server via a wireless Internet connection through the smartphone in real-time. Figure 10 shows the display of received ECG signal on the smartphone and Figure 11 shows the same result transmitted to the server in the text format.Figure 10Received real-time ECG data in graphical notationFigure 11Received real-time ECG data on serverHeart-beat rate (BPM) can be determined after analysis of the data either on the smartphone or the server. In this particular example, it represents a patient’s stablecondition with a normal heart-beat rate at approximately 72 BPM. This type of data can be diagnostically valuable and easily transmitted for consultations with distant experts.3.4Overall Data Transmission Rate (DTR)The Data Transmission Rate (DTR) is another important part of the system considering the data size. In our system, DTR depends on the microcontroller, the Bluetooth transmitter and the wireless Internet connection speed. An UART connection between the sensor and microcontroller is established at the baud rate of 115200 bps which achieves a communication bandwidth up to 15KB/s. This emphasizes that our system is capable of the data transmission by integrating multiple types of sensors for a body sensor network system that can be important for patient monitoring, real-time data analysis and diagnosis.4CONCLUSIONSIn this paper, we introduced a system using the smartphone for collecting real-time sensor data and simultaneously streaming the data to the server using Bluetooth and Internet connections. This design is the advancement over ordinary wired sensor networks which are restricted to a fixed monitoring location. In the proposed system, an accelerometer, a temperature sensor and ECG signals have been selected for data transmission using Bluetooth and wireless Internet connections. Having the Bluetooth transmitter on the smartphone, the Android system receives and displays the data on the screen in the graphical or text format and streams the collected data to the central server for data analysis, diagnosis and archiving. Taking advantage of the Android system, NFC technology was used to reduce the unnecessary Bluetooth connection process. This system is highly scalable to include more sensors to produce an upgraded patient monitoring system that is both more accurate and responsive. Furthermore, storing history of collected sensor data in the central server is extremely critical for reliable patient diagnosis.摘要在本文中，我们提出了一个使用Android智能手机，收集传感器数据显示在屏幕上并同步到中央服务器的数据流同步系统。

数字通信或面对面通信英语作文Digital Communication vs. Face-to-Face Communication.Communication is the lifeblood of any society, and it has evolved significantly over the years. From the ancient times of oral traditions and smoke signals to the modern era of digital communication, people have found innovative ways to convey messages and share ideas. In this essay, we will delve into the comparison between digital communication and face-to-face communication, discussing their respective advantages, disadvantages, and the impact they have on our lives.Digital Communication.Digital communication, primarily through the internet and various digital devices, has revolutionized the way we interact with each other. It has removed geographical barriers, allowing people from different parts of the world to connect instantly. Emails, social media, messaging apps,and video conferencing tools have made it possible for businesses to operate globally and for families to stay connected despite being far apart.Advantages of Digital Communication.1. Convenience: Digital communication offers unprecedented convenience. You can send messages, make calls, or video chat from anywhere, anytime, as long as you have an internet connection.2. Cost-Effectiveness: Compared to traditional communication methods, digital communication is often more cost-effective. It eliminates the need for physical infrastructure like phone lines or postal services.3. Versatility: Digital communication tools are incredibly versatile, allowing users to share not just text but also images, videos, audio files, and more.4. Accessibility: People with disabilities or special needs can benefit significantly from digital communicationtools that offer features like text-to-speech conversion, captioning, and zoom capabilities.Disadvantages of Digital Communication.1. Lack of Nonverbal Communication: Face-to-face communication involves a range of nonverbal cues likefacial expressions, body language, and tone of voice. Digital communication often fails to capture these important elements, leading to misunderstandings and misinterpretations.2. Digital Divide: Not everyone has access to digital communication tools, creating a digital divide between those who are connected and those who are not.3. Privacy Concerns: With the widespread use of digital communication, there are increasing concerns about privacy and data security.Face-to-Face Communication.Face-to-face communication, on the other hand, is the oldest and perhaps the most natural form of communication. It involves direct interaction between people, where they can see, hear, and respond to each other's cues.Advantages of Face-to-Face Communication.1. Richer Communication: Face-to-face communication allows for a richer exchange of ideas and emotions. It incorporates both verbal and nonverbal cues, leading to a deeper understanding and connection between people.2. Immediate Feedback: When communicating face-to-face, you can immediately see and respond to the reactions of the other person. This feedback loop is crucial for effective communication.3. Building Relationships: Face-to-face communicationis essential for building and maintaining relationships. It fosters trust and understanding, leading to stronger social bonds.Disadvantages of Face-to-Face Communication.1. Limited Reach: Face-to-face communication is limited by physical proximity. It can be challenging to connect with people who are far away.2. Time Constraints: Face-to-face meetings often require scheduling and can be time-consuming, especially when multiple parties are involved.3. Cost: Face-to-face communication can be more costly, especially when it involves travel and accommodation expenses.Conclusion.Digital communication and face-to-face communication each have their unique strengths and weaknesses. The choice between them depends on the context, purpose, and the people involved. In the modern world, where technology is constantly evolving, it is essential to appreciate both forms of communication and use them appropriately toachieve the desired outcomes.Digital communication is invaluable for its convenience, cost-effectiveness, and versatility. It has transformed the way we work, learn, and socialize, making the world more connected and accessible. However, we should also recognize its limitations, particularly in terms of lacking nonverbal cues and potential privacy concerns.Face-to-face communication, on the other hand, is irreplaceable for its ability to convey emotions, build trust, and foster deeper relationships. It remains crucialin settings where a richer, more personal exchange is desired or needed, such as in negotiations, therapy sessions, or simply catching up with friends.Ultimately, the key is to understand the strengths and weaknesses of both communication modes and use them complementarily to achieve the best possible outcomes in different scenarios. By doing so, we can harness the powerof technology while maintaining the humanity and warmth of face-to-face interactions.。

附录一、英文原文：Detecting Anomaly Traffic using Flow Data in the realVoIP networkI. INTRODUCTIONRecently, many SIP[3]/RTP[4]-based VoIP applications and services have appeared and their penetration ratio is gradually increasing due to the free or cheap call charge and the easy subscription method. Thus, some of the subscribers to the PSTN service tend to change their home telephone services to VoIP products. For example, companies in Korea such as LG Dacom, Samsung Net- works, and KT have begun to deploy SIP/RTP-based VoIP services. It is reported that more than five million users have subscribed the commercial VoIP services and 50% of all the users are joined in 2009 in Korea [1]. According to IDC, it is expected that the number of VoIP users in US will increase to 27 millions in 2009 [2]. Hence, as the VoIP service becomes popular, it is not surprising that a lot of VoIP anomaly traffic has been already known [5]. So, Most commercial service such as VoIP services should provide essential security functions regarding privacy, authentication, integrity and non-repudiation for preventing malicious traffic. Particu- larly, most of current SIP/RTP-based VoIP services supply the minimal security function related with authentication. Though secure transport-layer protocols such as Transport Layer Security (TLS) [6] or Secure RTP (SRTP) [7] have been standardized, they have not been fully implemented anddeployed in current VoIP applications because of the overheads of implementation and performance. Thus, un-encrypted VoIP packets could be easily sniffed and forged, especially in wireless LANs. In spite of authentication,the authentication keys such as MD5 in the SIP header could be maliciously exploited, because SIP is a text-based protocol and unencrypted SIP packets are easily decoded. Therefore, VoIP services are very vulnerable to attacks exploiting SIP and RTP. We aim at proposing a VoIP anomaly traffic detection method using the flow-based traffic measurement archi-tecture. We consider three representative VoIP anomalies called CANCEL, BYE Denial of Service (DoS) and RTP flooding attacks in this paper, because we found that malicious users in wireless LAN could easily perform these attacks in the real VoIP network. For monitoring VoIP packets, we employ the IETF IP Flow Information eXport (IPFIX) [9] standard that is based on NetFlow v9. This traffic measurement method provides a flexible and extensible template structure for various protocols, which is useful for observing SIP/RTP flows [10]. In order to capture and export VoIP packets into IPFIX flows, we define two additional IPFIX templates for SIP and RTP flows. Furthermore, we add four IPFIX fields to observe packets which are necessary to detect VoIP source spoofing attacks in WLANs.II. RELATED WORK[8] proposed a flooding detection method by the Hellinger Distance (HD) concept. In [8], they have pre- sented INVITE, SYN and RTP flooding detection meth-ods. The HD is the difference value between a training data set and a testing data set. The training data set collected traffic over n sampling period of duration Δ testing data set collected traffic next the training data set in the same period. If the HD is close to ‘1’, this testing data set is regarded as anomaly traffic. For using this method, they assumed that initial training data set didnot have any anomaly traffic. Since this method was based on packet counts, it might not easily extended to detect other anomaly traffic except flooding. On the other hand, [11] has proposed a VoIP anomaly traffic detection method using Extended Finite State Machine (EFSM). [11] has suggested INVITE flooding, BYE DoS anomaly traffic and media spamming detection methods. However, the state machine required more memory because it had to maintain each flow. [13] has presented NetFlow-based VoIP anomaly detection methods for INVITE, REGIS-TER, RTP flooding, and REGISTER/INVITE scan. How-ever, the VoIP DoS attacks considered in this paper were not considered. In [14], an IDS approach to detect SIP anomalies was developed, but only simulation results are presented. For monitoring VoIP traffic, SIPFIX [10] has been proposed as an IPFIX extension. The key ideas of the SIPFIX are application-layer inspection and SDP analysis for carrying media session information. Yet, this paper presents only the possibility of applying SIPFIX to DoS anomaly traffic detection and prevention. We described the preliminary idea of detecting VoIP anomaly traffic in [15]. This paper elaborates BYE DoS anomaly traffic and RTP flooding anomaly traffic detec-tion method based on IPFIX. Based on [15], we have considered SIP and RTP anomaly traffic generated in wireless LAN. In this case, it is possible to generate the similiar anomaly traffic with normal VoIP traffic, because attackers can easily extract normal user information from unencrypted VoIP packets. In this paper, we have extended the idea with additional SIP detection methods using information of wireless LAN packets. Furthermore, we have shown the real experiment results at the commercial VoIP network.III. THE VOIP ANOMALY TRAFFIC DETECTION METHOD A. CANCEL DoS Anomaly Traffic DetectionAs the SIP INVITE message is not usually encrypted, attackers could extract fields necessary to reproduce the forged SIP CANCEL message by sniffing SIP INVITE packets, especially in wireless LANs. Thus, we cannot tell the difference between the normal SIP CANCEL message and the replicated one, because the faked CANCEL packet includes the normal fields inferred from the SIP INVITE message. The attacker will perform the SIP CANCEL DoS attack at the same wireless LAN, because the purpose of the SIP CANCEL attack is to prevent the normal call estab-lishment when a victim is waiting for calls. Therefore, as soon as the attacker catches a call invitation message for a victim, it will send a SIP CANCEL message, which makes the call establishment failed. We have generated faked SIP CANCEL message using sniffed a SIP INVITE in SIP header of this CANCEL message is the same as normal SIP CANCEL message, because the attacker can obtain the SIP header field from unencrypted normal SIP message in wireless LAN environment. Therefore it is impossible to detect the CANCEL DoS anomaly traffic using SIP headers, we use the different values of the wireless LAN frame. That is, the sequence number in the frame will tell the difference between a victim host and an attacker. We look into source MAC address and sequence number in the MAC frame including a SIP CANCEL message as shown in Algorithm 1. We compare the source MAC address of SIP CANCEL packets with that of the previously saved SIP INVITE flow. If the source MAC address of a SIP CANCEL flow is changed, it will be highly probable that the CANCEL packet is generated by a unknown user. However, the source MAC address could be spoofed. Regarding source spoofing detection, we employ the method in [12] that uses sequence numbers of frames. We calculate the gap between n-th and (n-1)-th frames. As the sequence number field in a MAC header uses 12 bits, it varies from 0 to 4095. When we find that the sequence number gap between a single SIP flow is greater than the threshold value of N that willbe set from the experiments, we determine that the SIP host address as been spoofed for the anomaly traffic.B. BYE DoS Anomaly Traffic DetectionIn commercial VoIP applications, SIP BYE messages use the same authentication field is included in the SIP IN-VITE message for security and accounting purposes. How-ever, attackers can reproduce BYE DoS packets through sniffing normal SIP INVITE packets in wireless faked SIP BYE message is same with the normal SIP BYE. Therefore, it is difficult to detect the BYE DoS anomaly traffic using only SIP header sniffing SIP INVITE message, the attacker at the same or different subnets could terminate the normal in- progress call, because it could succeed in generating a BYE message to the SIP proxy server. In the SIP BYE attack, it is difficult to distinguish from the normal call termination procedure. That is, we apply the timestamp of RTP traffic for detecting the SIP BYE attack. Generally, after normal call termination, the bi-directional RTP flow is terminated in a bref space of time. However, if the call termination procedure is anomaly, we can observe that a directional RTP media flow is still ongoing, whereas an attacked directional RTP flow is broken. Therefore, in order to detect the SIP BYE attack, we decide that we watch a directional RTP flow for a long time threshold of N sec after SIP BYE message. The threshold of N is also set from the 2 explains the procedure to detect BYE DoS anomal traffic using captured timestamp of the RTP packet. We maintain SIP session information between clients with INVITE and OK messages including the same Call-ID and 4-tuple (source/destination IP Address and port number) of the BYE packet. We set a time threshold value by adding Nsec to the timestamp value of the BYE message. The reason why we use the captured timestamp is that a few RTP packets are observed under second. If RTP traffic is observed after the time threshold, this willbe considered as a BYE DoS attack, because the VoIP session will be terminated with normal BYE messages. C. RTP Anomaly Traffic Detection Algorithm 3 describes an RTP flooding detection method that uses SSRC and sequence numbers of the RTP header. During a single RTP session, typically, the same SSRC value is maintained. If SSRC is changed, it is highly probable that anomaly has occurred. In addition, if there is a big sequence number gap between RTP packets, we determine that anomaly RTP traffic has happened. As inspecting every sequence number for a packet is difficult, we calculate the sequence number gap using the first, last, maximum and minimum sequence numbers. In the RTP header, the sequence number field uses 16 bits from 0 to 65535. When we observe a wide sequence number gap in our algorithm, we consider it as an RTP flooding attack.IV. PERFORMANCE EVALUATIONA. Experiment EnvironmentIn order to detect VoIP anomaly traffic, we established an experimental environment as figure 1. In this envi-ronment, we employed two VoIP phones with wireless LANs, one attacker, a wireless access router and an IPFIX flow collector. For the realistic performance evaluation, we directly used one of the working VoIP networks deployed in Korea where an 11-digit telephone number (070-XXXX-XXXX) has been assigned to a SIP wireless SIP phones supporting , we could make calls to/from the PSTN or cellular phones. In the wireless access router, we used two wireless LAN cards- one is to support the AP service, and the other is to monitor packets. Moreover, in order to observe VoIP packets in the wireless access router, we modified nProbe [16], that is an open IPFIX flow generator, to create and export IPFIX flows related with SIP, RTP, and information. As the IPFIX collector, we have modified libipfix so that it could provide the IPFIX flow decoding function for SIP, RTP, and templates. We used MySQL for the flow DB.B. Experimental ResultsIn order to evaluate our proposed algorithms, we gen-erated 1,946 VoIP calls with two commercial SIP phones and a VoIP anomaly traffic generator. Table I showsour experimental results with precision, recall, and F-score that is the harmonic mean of precision and recall. In CANCEL DoS anomaly traffic detection, our algorithm represented a few false negative cases, which was related with the gap threshold of the sequence number in MAC header. The average of the F-score value for detecting the SIP CANCEL anomaly is %.For BYE anomaly tests, we generated 755 BYE mes-sages including 118 BYE DoS anomalies in the exper-iment. The proposed BYE DoS anomaly traffic detec-tion algorithm found 112 anomalies with the F-score of %. If an RTP flow is terminated before the threshold, we regard the anomaly flow as a normal one. In this algorithm, we extract RTP session information from INVITE and OK or session description messages using the same Call-ID of BYE message. It is possible not to capture those packet, resulting in a few false-negative cases. The RTP flooding anomaly traffic detection experiment for 810 RTP sessions resulted in the F score of 98%.The reason of false-positive cases was related with the sequence number in RTP header. If the sequence number of anomaly traffic is overlapped with the range of the normal traffic, our algorithm will consider it as normal traffic.V. CONCLUSIONSWe have proposed a flow-based anomaly traffic detec-tion method against SIP and RTP-based anomaly traffic in this paper. We presented VoIP anomaly traffic detection methods with flow data on the wireless access router. We used the IETF IPFIX standard to monitor SIP/RTP flows passing through wireless access routers, because its template architecture is easily extensible to several protocols. For this purpose, we defined two new IPFIX templates for SIP and RTP traffic and four new IPFIX fields for traffic. Using these IPFIX flow templates,we proposed CANCEL/BYE DoS and RTP flooding traffic detection algorithms. From experimental results on the working VoIP network in Korea, we showed that our method is able to detect three representative VoIP attacks on SIP phones. In CANCEL/BYE DoS anomaly trafficdetection method, we employed threshold values about time and sequence number gap for classfication of normal and abnormal VoIP packets. This paper has not been mentioned the test result about suitable threshold values. For the future work, we will show the experimental result about evaluation of the threshold values for our detection method.二、英文翻译：交通流数据检测异常在真实的世界中使用的VoIP网络一 .介绍最近,许多SIP[3],[4]基于服务器的VoIP应用和服务出现了,并逐渐增加他们的穿透比及由于自由和廉价的通话费且极易订阅的方法。

外文资料和中文翻译外文资料：Review of UMTS1.1 UMTS Network ArchitectureThe European/Japanese 3G standard is referred to as UMTS. UMTS is one of a number of standards ratified by the ITU-T under the umbrella of IMT-2000. It is currently the dominant standard, with the US CDMA2000 standard gaining ground, particularly with operators that have deployed cdmaOne as their 2G technology. At time of writing,Japan is the most advanced in terms of 3G network deployment. The three incumbent operators there have implemented three different technologies: J-Phone is using UMTS,KDDI has a CDMA2000 network, and the largest operator NTT DoCoMo is using a system branded as FOMA (Freedom of Multimedia Access). FOMA is based on the original UMTS proposal, prior to its harmonization and standardization.The UMTS standard is specified as a migration from the second generation GSM standard to UMTS via the General Packet Radio System (GPRS) and Enhanced Data for Global Evolution (EDGE), as shown in Figure. This is a sound rationale since as of April 2003, there were over 847 Million GSM subscribers worldwide1, accounting for68% of the global cellular subscriber figures. The emphasis is on keeping as much ofthe GSM network as possible to operate with the new system.We are now well on the road towards Third Generation (3G), where the network will support all traffic types: voice, video and data, and we should see an eventual explosion in the services available on the mobile device. The driving technology for this is the IP protocol. Many cellular operators are now at a position referred to as 2.5G, with the deployment of GPRS, which introduces an IP backbone into the mobile core network.The diagram below, Figure 2, shows an overview of the key components in a GPRS network, and how it fits into the existing GSM infrastructure.The interface between the SGSN and GGSN is known as the Gn interface and uses the GPRS tunneling protocol (GTP, discussed later). The primary reason for the introduction of this infrastructure is to offer connections to external packet networks, such as the Internet or a corporate Intranet.This brings the IP protocol into the network as a transport between the SGSN and GGSN. This allows data services such as email or web browsing on the mobile device,with users being charged based on volume of data rather than time connected.The dominant standard for delivery of 3G networks and services is the Universal Mobile Telecommunications System, or UMTS. The first deployment of UMTS is the Release ’99 architecture, shown below in Figure 3.In this network, the major change is in the radio access network (RAN) with the introduction of CDMA technology for the air interface, and ATM as a transport in the transmission part. These changes have been introduced principally to support the transport of voice, video and data services on the same network. The core network remains relatively unchanged, with primarily software upgrades. However, the IP protocol pushes further into the network with the RNC now communicating with the 3G SGSN using IP.The next evolution step is the Release 4 architecture, Figure 4. Here, the GSM core is replaced with an IP network infrastructure based around Voice over IP technology.The MSC evolves into two separate components: a Media Gateway (MGW) and an MSC Server (MSS). This essentially breaks apart the roles of connection and connection control. An MSS can handle multiple MGWs, making the network more scaleable.Since there are now a number of IP clouds in the 3G network, it makes sense to merge these together into one IP or IP/ATM backbone (it is likely both options will be available to operators.) This extends IP right across the whole network, all the way to the BTS.This is referred to as the All-IP network, or the Release 5 architecture, as shown in Figure 5. The HLR/VLR/EIR are generalised and referred to as the HLR Subsystem(HSS).Now the last remnants of traditional telecommunications switching are removed, leaving a network operating completely on the IP protocol, and generalised for the transport of many service types. Real-time services are supported through the introduction of a new network domain, the IP Multimedia Subsystem (IMS).Currently the 3GPP are working on Release 6, which purports to cover all aspects not addressed in frozen releases. Some call UMTS Release 6 4G and it includes such issues as interworking of hot spot radio access technologies such as wireless LAN.1.2 UMTS FDD and TDDLike any CDMA system, UMTS needs a wide frequency band in which to operate to effectively spread signals. The defining characteristic of the system is the chip rate, where a chip is the width of one symbol of the CDMA code. UMTS uses a chip rate of 3.84Mchips/s and this converts to a required spectrum carrier of 5MHz wide. Since this is wider than the 1.25MHz needed for the existing cdmaOne system, the UMTS air interface is termed ‘wideband’ CDMA.There are actually two radio technologies under the UMTS umbrella: UMTS FDD and TDD. FDD stands for Frequency Division Duplex, and like GSM, separates traffic in the uplink and downlink by placing them at different frequency channels. Therefore an operator must have a pair of frequencies allocated to allow them to run a network, hence the term ‘paired spectrum’. TDD or Time Division Duplex requires only one frequency channel, and uplink and downlink traffic are separated by sending them at different times. The ITU-T spectrum usage, as shown in Figure 6, for FDD is 1920- 980MHz for uplink traffic, and 2110-2170MHz for downlink. The minimum allocation an operator needs is two paired 5MHz channels, one for uplink and one for downlink, at a separation of 190MHz. However, to provide comprehensive coverage and services, it is recommended that an operator be given three channels. Considering the spectrum allocation, there are 12 paired channels available, and many countries have now completed the licencing process for this spectrum, allocating between two and four channels per licence. This has tended to work out a costly process for operators, since the regulatory authorities in some countries, notably in Europe, have auctioned these licences to the highest bidder. This has resulted in spectrum fees as high as tens of billions of dollars in some countries.The Time Division Duplex (TDD) system, which needs only one 5MHz band in which to operate, often referred to as unpaired spectrum. The differences between UMTS FDD and TDD are only evident at the lower layers, particularly on the radio interface. At higher layers, the bulk of the operation of the two systems is the same. As the name suggests, the TDD system separates uplink and downlink traffic by placing them in different time slots. As will be seen later, UMTS uses a 10ms frame structure which is divided into 15 equal timeslots. TDD can allocate these to be either uplink or downlink,with one or more breakpoints between the two in a frame defined. In this way, it is well suited to packet traffic, since this allows great flexibility in dynamically dimensioning for asymmetry in traffic flow.The TDD system should not really be considered as an independent network, but rather as a supplementfor an FDD system to provide hotspot coverage at higher data rates. It is rather unsuitable for large scale deployment due to interference between sites, since a BTS may be trying to detect a weak signal from a UE, which is blocked out by a relatively strong signal at the same frequency from a nearby BTS. TDD is ideal for indoor coverage over small areas.Since FDD is the main access technology being developed currently, the explanations presented here will focus purely on this system.1.3 UMTS Bearer ModelThe procedures of a mobile device connecting to a UMTS network can be split into two areas: the access stratum (AS) and the non-access stratum (NAS). The access stratum involves all the layers and subsystems that offer general services to the non-access stratum. In UMTS, the access stratum consists of all of the elements in the radio access network, including the underlying ATM transport network, and the various mechanisms such as those to provide reliable information exchange. All of the non-access stratum functions are those between the mobile device and the core network, for example, mobility management. Figure 7 shows the architecture model. The AS interacts with the NAS through the use of service access points (SAPs).UMTS radio access network (UTRAN) provides this separation of NAS and AS functions, and allows for AS functions to be fully controlled and implemented within the UTRAN. The two major UTRAN interfaces are the Uu, which is the interface between the mobile device, or User Equipment (UE) and the UTRAN, and the Iu, which is the interface between the UTRAN and the core network. Both of these interfaces can be divided into control and user planes each with appropriate protocol functions.A Bearer Service is a link between two points, which is defined by a certain set of characteristics. In the case of UMTS, the bearer service is delivered using radio access bearers.A Radio access bearer (RAB) is defined as the service that the access stratum (i.e.UTRAN) provides to the non-access stratum for transfer of user data between the User Equipment and Core Network. A RAB can consist of a number of subflows, which are data streams to the core network within the RAB that have different QoS characteristics,such as different reliabilities. A common example of this is different classes of bits with different bit error rates can be realised as different RAB subflows. RAB subflows are established and released at the time the RAB is established and released, and are delivered together over the same transport bearer.A Radio Link is defined as a logical association between a single User Equipment (UE) and a single UTRAN access point, such as an RNC. It is physically comprised of one or more radio bearers and should not be confused with radio access bearer.Looking within the UTRAN, the general architecture model is as shown in Figure 8 below. Now shown are the Node B or Base Station (BTS) and Radio Network Controller (RNC) components, and their respective internal interfaces. The UTRAN is subdivided into blocks referred to as Radio Network Subsystems (RNS), where each RNS consists of one controlling RNC (CRNC) and all the BTSs under its control. Unique to UMTS is the interface between RNSs, the Iur interface, which plays a key role in handover procedures. The interface between the BTS and RNC is the Iub interface.All the ‘I’ interfaces: Iu, Iur and Iub, currently3 use ATM as a transport layer. In the context of ATM, the BTS is seen as a host accessing an ATM network, within which the RNC is an ATM switch. Therefore, the Iub is a UNI interface, whereas the Iu and Iur interfaces are considered to be NNI, as illustrated in Figure 9.This distinction is because the BTS to RNC link is a point-to-point connection in that a BTS or RNC will only communicate with the RNC or BTS directly connected to it, and will not require communication beyond that element to another network element.For each user connection to the core network, there is only one RNC, which maintains the link between the UE and core network domain, as highlighted in Figure 10. This RNC is referred to as the serving RNC or SRNC. That SRNC plus the BTSs under its control is then referred to as the SRNS. This is a logical definition with reference to that UE only. In an RNS, the RNC that controls a BTS is known as the controlling RNC or CRNC. This is with reference to the BTS, cells under its control and all the common and shared channels within.As the UE moves, it may perform a soft or hard handover to another cell. In the case of a soft handover, the SRNC will activate the new connection to the new BTS. Should the new BTS be under the control of another RNC, the SRNC will also alert this new RNC to activate a connection along the Iur interface. The UE now has two links, one directly to the SRNC, and the second, through the new RNC along the Iur interface. In this case, this new RNC is logically referred to as a drift RNC or DRNC, see Figure 10. It is not involved in any processing of the call and merely relays it to the SRNC for connection to the core. In summary, SRNC and DRNC are usually associated with the UE and the CRNC is associated with the BTS. Since these are logical functions it is normal practice that a single RNC is capable of dealing with all these functions.A situation may arise where a UE is connected to a BTS for which the SRNC is not the CRNC for that BTS. In that situation, the network may invoke the Serving RNC Relocation procedure to move the core network connection. This process is described inSection 3.中文翻译：通用移动通信系统的回顾1.1 UMTS网络架构欧洲/日本的3G标准，被称为UMTS。

红外数据通信技术外文翻译文献(文档含中英文对照即英文原文和中文翻译)Infrared Remote Control SystemAbstractRed outside data correspondence the technique be currently within the scope of world drive extensive usage of a kind of wireless conjunction technique, drive numerous hardware and software platform support. Red outside the transceiver product have cost low, small scaled turn, the baud rate be quick, point to point SSL, be free from electromagnetism thousand Raosetc. characteristics, can realization information at dissimilarity of the product fast, convenience, safely exchange and transmission, at short distance wireless deliver aspect to own very obvious of advantage. Along with red outside the data deliver a technique more and more mature, the cost descend, red outside the transceiver necessarily will get at the short distance communication realm more extensive of application.The purpose that design this system is transmit customer’s operation information with infrared rays for transmit media, then demodulate original signal with receive circuit. It use coding chip to modulate signal and use decoding chip to demodulate signal. The coding chip is PT2262 and decoding chip is PT2272. Both chips are made in Taiwan. Main work principle is that we provide to input the information for the PT2262 with coding keyboard. The input information was coded by PT2262 and loading to high frequent load wave whose frequent is 38 kHz, then modulate infrared transmit dioxide and radiate space outside when it attian enough power. The receive circuit receive the signal and demodulate original information. The original signal was decoded by PT2272, so as to drive some circuit to accomplish customer’s operation demand.Keywords: Infrared dray；Code；Decoding；LM386；Red outside transceiver1 Introduction1.1 research the background and significanceInfrared Data Communication Technology is the world wide use of a wireless connection technology, by the many hardware and software platforms supported. Is a data through electrical pulses and infrared optical pulse switch between the wireless data transceiver technology.Infrared transceiver products with low cost, small, fast transmission rate, the point-to-point transmission security, not subject to electromagnetic interference and other characteristics that can be achieved between the different products, rapid, convenient and safe exchange and transmission, In short distance wireless transmission have a very distinct advantage.Infrared transceiver products in the portable product of a great role. At present, the world's 150 million piece of equipment used infrared technology in electronic products and industrial equipment. medical equipment and other fields widely used. For example, 95% of the notebook computers on the installation of infrared transceiver interface the majority of the cell phone is also the allocation of infrared transceiver interface. With the exchange of quantitative data, infrared data communications will enable cell phone data transmission more convenient. With infrared data transmission technology matures, perfect, low costs, Infrared Transceiver in short distance communications will be more widely applied.This chapter first describes the infrared transceiver IC design issues to the background and significance. then briefed the infrared data communications technology features and applications, and infrared transceiver product characteristics, domestic and international situation and development trend of the last under infrared remote transceiver system in practical application to establish a task of design orientation.1.2 Infrared Remote Control Transceiver SystemInfrared remote control system is divided into single-channel and multi-channel remote control. Only a command signal transmission channel, called single-channel remote control system; with more than two instructions signal transmission channel known as a multi-channel remote control system. Relatively simple single-channel remote control, in general, only a launcher directive Key receivers and only one circuit implementation. While in thereceiving circuit to add more stable memory circuits that can be activated commands to launch a number of key, so that the receiver circuit multi stable memory circuit repeatedly to change the state, to realize many of the functional control, But such a state of change is the order. If we are to achieve an arbitrary control, resort to the use of multi-channel remote control system. Multi-channel remote control can be realized by the object of arbitrary multi-function remote control. As for the choice of several routes and what control methods, according to the actual situation (such as object, operational requirements and cost accounting, etc.) to decide. General infrared remote transceiver system by infrared remote control transmitter signal coding, infrared remote control signal receivers and decoders (or decoder chip MCU) and the external circuit consisting of three parts. Signal transmitter remote control code used to generate pulses of infrared emission-driven output infrared remote control signal, receiver completion of the remote control signal amplification and detection, plastic and demodulation encoding pulse. Infrared remote control coded pulse is going to obtain a continuous serial binary code, and for most of the infrared transceiver system, This serial code as micro-controller of the remote control input signals from the internal CPU completion of the remote control instruction decoder, on the other infrared remote control transceivers, the designers of electronic products, The internal micro-controller of the remote control decoder directive is not accessible. Therefore, people are using infrared encoder / decoder chip and microcontroller developed various generic infrared remote transceiver system, In various equipment infrared signals between the transceiver.Remote transceiver system generally transmitters and receivers is composed of two parts. Launchers from the general direction keys, coded instructions circuit modulation circuit, driving circuit, firing circuit of several parts. When pressed a key, the directive coding circuit, in the correspondinginstructions encoded signal, the encoder signal to the carrier modulation, Driven by the power amplifier circuit after circuit fired from the field after firing instructions coded modulation signals. General receiver by the receiving circuit, the amplifier circuit, demodulation circuits, instruction decoder circuit, driving circuit, circuit implementation of several parts. Receiving Circuit will launch vehicles have been coded modulation signal receiving instructions from, and to enlarge evacuation demodulation circuit. Demodulation circuit will have the coding modulation signal demodulation, namely, reduction of signal coding. The instruction decoder to the encoder signal decoding, Driven by the final circuit to drive the implementation of various instructions circuit to control the operation.1.3 infrared remote control transceiver product profiles 1.3.1 infrared remote control transceiver product structure and typeCurrently infrared transceiver in accordance with the mode of transmission rate and can be divided into four categories : Serial mode, the highest rate of 115.2 Kbps; medium-speed model : the highest rate of 0.567 Mbps and 1.152Mbps; High-speed mode : The maximum rate of 16 Mbps.Also according to the size chip power consumption can be divided into low-power consumption and standard two categories, low-power type normally used 3 V power supply, transmission distance closer to about 0 - 30cm, which is commonly used standard 5V power supply, transmission distance away at least 1m above.1.3.2 infrared remote control transmitters of the status quo at home and abroadInfrared communication technology in the development stage and there are several infrared communication standards, between different standards for infrared equipment can not infrared communication. To have all the infraredequipment to interoperability in 1993 by more than 20 large manufacturers initiated the establishment of an Infrared Data Association (IRDA) unified the infrared communication standards , which is currently widely used in infrared data communication protocols and standards, also known as the IRDA standard.Since 1993 IRDA since the establishment of the Infrared Data Association members have developed to more than 150. IRDA standards of the industry has been widely recognized and supported. Has been developed with the infrared communications equipment have been as many as 100 species. IR module, installed capacity has reached 150 million sets. Although there is also a short distance wireless Bluetooth technology, But in infrared communication technology low cost and broad compatibility advantages, Infrared data communication in the future will still be a very long time inherent short-range wireless data communications fields play an important role.1.3.3 Infrared Transceiver product development trendIn various infrared transceiver products, although the transmission rate, transmission distance and other characteristics, But infrared transceiver products has been towards improving the transmission rate, increase the transmission distance and lower power consumption, expanding launch reception angle of development. In particular, as the technology development and maturity, the means of transmission is moving in the direction of point-to-multipoint. Therefore infrared remote control transceiver products have broader prospects for development.2 Infrared communication of knowledge2.1 infrared ray foundation knowledge2.1.1 infrared outlinedInfrared is actually a kind of electromagnetic wave. From the analysis of various natural component of the electromagnetic wave reflected spectrum is :-ray, x-ray, ultraviolet, visible, infrared, microwave and radio wave. From the viewpoint of form, and they did not seem to, but if the wavelength in descending order, and we will find him all the only visible light spectrum of the entire 0.38 μm - 0.76μm so long little area, and adjacent to the visible light and infrared (including the far infrared, mid-infrared and near infrared foreign) accounts for the spectrum of 0.76 μm - 1000μm of a major. Which micron wavelength range also includes UV, visible, near infrared, mid-infrared and far-infrared, microwave.From the above analysis shows that infrared is a very rich spectrum resources, it currently has in production, life, military, medical, and other aspects have been widely used, such as infrared heating, medical infrared, infrared communication, infrared camera, infrared remote control, and so on. Infrared remote control is the many applications of infrared part of the current household appliances widely used in TV remote control, VCR remote control, VCD remote control, high-fidelity audio remote control, are used infra-red remote control, It allows the control of these appliances have become very easy.2.1.2 infrared propertiesInfrared lies between visible light and microwave a wave, it is with certain clinical characteristics of the wave. In the near-infrared, visible light and its adjacent, it is visible in certain characteristics, such as straight-line transmission, reflection, refraction, scattering, diffraction, can be certainobjects and can be absorbed through the lens of their focusing. In the far-infrared region, owing to its neighboring microwave, it has some characteristics of microwave, If a strong penetrating power and can run through some opaque substances. Since in any object, natural profession, regardless of whether its own luminescence (referring to visible light), as long as the temperature is above absolute zero (-273 °C), moment will be kept around to infrared radiation. Only higher temperature of objects strong infrared radiation, low-temperature objects infrared radiation weaker. Therefore infrared feature is the greatest common in nature, it is called thermal radiation called thermal radiation. Infrared cameras, infrared night market pyroelectric infrared detectors and some other missiles aiming at is the use of this characteristic of infrared work.Infrared and visible light compared to another characteristic of a variety of colors. As the longest wavelength of visible light is a wavelength of the shortest times (780 nm-380 nm), So is called an octave. And infrared wavelength is the longest shortest wavelength of a times, and the longest wavelength infrared is the shortest wavelength of 10 times, that is, 10 octave. Therefore, if visible light can be expressed as seven colors, infrared may performance 70 colors, showing the rich colors. Infrared smoke through the good performance, which is also one of its features.Because not visible to the infrared, it has little effect on the environment. By the wave infrared rays than the long wavelength radio waves, infrared remote control will not affect the nearby radio equipment. Another wavelength of less t han 1.5μm near infrared light, transparent atmosphere in the visible light transmission characteristics much better than, because it close to the visible edge of the red light, linear transmission, reflection, refraction and absorption material and the physical characteristics very similar to visible light. Therefore, it can be used with similar visible focusing lens and other opticaldevices. Because infrared remote control is not as remote as the radio through the barrier to control the object's ability to control, so in the design of household appliances infra-red remote control, wireless remote control as unnecessary, each set (transmitters and receivers) have different frequency or remote coding (Otherwise, wall will control or interference with neighbors household appliances), all similar products in the infrared remote control, The same can control the frequency or coding, and no remote control signal "drop." This universal infrared remote control provides a great convenience. Infrared to visible light, is very subtle and confidentiality, therefore, the security, Alert and other security devices have been widely used. Infrared remote control is simple in structure and easy, low-cost, anti-interference capability, high reliability are a number of advantages, is a close-up remote control, especially in indoor remote control optimized manner.2.1.3 infrared diode characteristicsInfrared is not visible, people here are not aware of. Electronic technology is used infrared light emitting diode (also known as the IR emission diode) to generate infrared. Infrared remote control transceiver is using near-infrared transmission control instructions 0.76μm wavelength of ~ 1. 5μm. Near-infrared remote control as a light source, because there infrared light emitting diodes and infrared receiving device (photo diode. Transistor and PV) and the luminescence peak wavelength of light by the general 0.8μm ~ 0. 94μm. in the near-infrared band, both of the spectrum is the coincidence to a good match, access to higher transmission efficiency and higher reliability. Commonly used infrared diode, and its shape is similar LED light emitting diodes, Its basic circuit shown in figure 2 -2. The triode plans for the switch, when the base added a driving signal, Transistor saturated conduction infrared LED D is also Wizard Link, issued infrared (near infrared about 0.93 μm). D.The pressure drop of about 1.4 V and the current general for 10-20mA. To adapt to the working voltage of the D loop resistance often as a series of infrared diode current limit resistance.When the circuit diagram of the infrared emission control corresponding to the controlled device, the control of the distance and D is proportional to the transmitting power. In order to increase the distance of infrared control, infrared diode D should work on the pulse state that work is the lifeblood of current. Because pulse light (optical modulation) the effective transmission distance and pulse is proportional to the peak current, only maximize peak current Ip, will increase the infrared distance. Ip increase is a way to reduce the pulse duty cycle, that is compressed pulse width τ some TV infrared remote control, its infrared luminescence of the pulse duty cycle of about 1/4-1/3; Some electrical products infrared remote control, its duty cycle of 1 / 10. Decreasing pulse duty cycle also enable low-power infrared LED distance of the greatly increased. Common infrared light emitting diodes, power is divided into small power (1 mW - 10mW). Chinese power (20mW - 50mW) and power (50mW - 100mW more) three categories. Use different power infrared LED, the allocation should be driven by the corresponding power control. Figure 2 -2 by the reflected infrared light-emitting diodes to make produce optical modulation, Drivers only need to add the control of a certain frequency pulse voltage.Infrared transmitter and receiver in the way the two kinds of straight, and the second is reflective. Luminescence pointed straight pipe and tube receiver placed in a relatively controlled and fired on the two ends, a certain distance away from the middle; Reflective means luminescent tube and pipe parallel with the receiving peacetime, without always receiving tube light, luminescence only in possession of the infrared light reflected fromencountered, the receiving tube received from the reflected infrared before work.2.2 infrared communication basic tenets2.2.1 infrared communication PrincipleCommunication is the use of infrared wavelength of 900 nm-infrared waves from 1000 to serve as an information carrier, through infrared technology between the two close communication and confidentiality of information transmitted. Infrared communication system structure include : part launcher, channel, the receiver part.Launcher source letter issued after the binary signal from the high-frequency modulated infrared LED sent, receiving device regard the reception of high-frequency signals from the infrared receiver tube after receiving further demodulation photoelectric conversion of the original information of a mass communication lose way. Afterwards the former Information received after receiving part of the drive circuit connected to the expected completion of the various functions. To which the modulation coding style pulse width modulation (by changing the pulse width modulated signal PWM) and pulse modulation time (through change the pulse train interval time between the modulation signal PPM) two.2.2.2 infrared communication system elements(1) Launches : Currently there is a infrared wireless digital communications system sources of information including voice, data, images. Its methods of work for the launch of the receiver can be divided into different layout LOS way (Light-of-Sight , intracardiac way), diffuse (diffuse) mode. LOS way directional, it has good channel characteristics such advantages, but the existence of a "shadow" effect. difficult to achieve roaming function. Roaming means the main features of non-directional, and easy to implementroaming function, but its channel quality is better sometimes LOS way. Transmission of signals required for a few of (the sampling was quantified), the general need for baseband modulation, transmission, modulation, sometimes signal source coding, the above-driven signals from photoelectric converter complete optical signal transmission. Infrared wireless digital communications system and its scope of work-for-fired power distribution, the quality of the communication. While using various methods to improve optical transmitter power, the other using spatial diversity, holographic films and so on so diffuse light for the launch of space optical power evenly distributed.(2) Channel : infrared wireless digital communication channel refers to the transmitters and receivers in the space between. Due to natural light and artificial light sources such as light signals in the context of intervention, and the source - Electrical Equipment, The optical noise and disturbances, infrared wireless digital communications in some occasions, poor quality, At this point needed to channel coding. Infrared wireless communication system, the optical signal reflection, light scattering and background noise and interference effects, Infrared wireless digital channel presence multi-path interference and noise, This is to improve the quality and access for high-speed applications should be addressed. Infrared wireless digital communication channel often used by the major optical components, optical filter, condenser, their role is : plastic, filter, depending on the field transformation, the band division, the lens can be used as launch-ray focusing, the use of optical filters filter out stray light, the use of optical lenses to expand the field of view receiver, able to make use of optical components for the link frequency division multiplexing, etc.. Infrared wireless communication channel optical noise : the natural noise (sunlight) and anthropogenic interference (fluorescent lighting). can be modulated by the transmission technology such as filters and adding to be addressed.(3) receivers : Channel optical signal from the optical receiver partially photoelectric conversion, In order to remove noise and intersymbol interference and other functions. Infrared wireless digital communications system receiver include optical receiver parts and follow-up sampling, filtering, judgment, quantity, balanced and decoding part. Infrared wireless optical receiver often used amplifier, and called for large-bandwidth, high gain, low noise and low noise, frequency response and channel impulse response matched. To be suppressed by low-frequency noise and human disturbance needs a band-pass filter. To obtain large optical receiver scope and instantaneous field of view, often using spherical optical lens.2.2.3 infrared communications featureWireless communications are a lot of ways, some using infrared communication with the following characteristics :• The high frequency, wave length, and fired the energy concentrated space propagation attenuation coefficient can ensure the effective signal transmission;• infrared is the invisible light, strong confidentiality and use it as an information carrier. device when there is no visual pollution, it does no harm to the human body;• dissemination without limitation, and there is no question of frequency interference with radio-wave pattern, not on the spectrum resources to the relevant authorities for the application and registration, easy to implement;• has a good point, when the transmission equipment and infrared receiver ports line up straight, deviation of not more than about 15 degrees when infrared devices running the best effect;• through infrared or not bypassed and objects, data transmission, optical path can not be blocked;• currently produce and receive infrared signals in the technology is relatively mature, components small size, low cost production of simple, easy to produce and modulation advantages.2.3 infrared communication code based on the knowledgeUsually, infrared remote control transmitters will signal (pulse binary code) modulation at 38 KHz carrier, After buffer amplified sent to the infrared light-emitting diodes, infrared signals into firing away. Pulse binary code in a variety of formats. One of the most commonly used code is PWM (pulse width modulation code) and the PPM code (Pulse Code Modulation). The former said in a pulse width, pulse indicated 0. The latter pulse width, but the width of code-not the same, the codes represent a bit - and the digits represent narrow 0.Remote coding pulse signal (PPM code as an example) are usually guided by the code, the system code, the anti-code system, a feature code, functional anti-code signal components. Guide the code name for the initial code, by the width of 9 ms and the margin width of 4.5 ms to the low-level components (different remote control systems in the low-level high width of a certain distinction), remote coding used to mark the beginning of pulsed signals. System identification code is also called code, which used to indicate the type of remote control system, in order to distinguish other remote-control system, prevent the remote control system malfunction. Functional code is also called scripts, which represents the corresponding control functions, Receiver of the micro-controller functions under the numerical code to complete the various functions operating. Anti-code system and function codes are anti-system code and the functional code against code Anti-code can be joined to the receiver synchronization transmission process leads to errors. In order to improve performance and reduce interference power consumption, The remote control will be coded pulse frequency of 38 KHz (for the cycle of 26.3 ms) of the carrier signal pulse reshuffle system (PAM), and then sentto the buffer amplified infrared LED, the remote control signal transmitter away.Address code and data codes are composed of different pulse width expressed that the two narrow pulse "0"; 2 pulse width "1"; a narrow pulse width and pulse expressed an "F" is the code addresses "vacant."Is the first part of a group a group of code, each code synchronization between separated. The plan is to enlarge the second half of a group code : a code from 12 AD (the address code plus data code For example, eight address code plus four data code), each with two AD-Pulse's : Pulse said the two "0"; 2 pulse width "1"; a narrow pulse width and pulse expressed an "F" is the code addresses "vacant."Realize fired at each fired at least four groups code, PT2272 only twice in a row to detect the same address code plus data code data will be the code "1" is driven The data should be output to drive margin and VT terminal for synchronous serial.红外遥控系统摘要目前红外数据通信技术是在世界范围内被广泛应用的一种无线连接技术，它也可以被许多软硬件平台所支持。

英文资料Ultra-Wideband Systems for Data CommunicationsG. Racherla, J.L. Ellis, D.S. Furuno, S.C. LinGeneral Atomics, Advanced Wireless Group10240 Flanders Ct. San Diego CA 92121WebsitABSTRACTUltra-Widebandt (UWB) is a radio transmission scheme that uses extremely low power pulses of radio energy spread across a wide spectrum of frequencies. UWB has several advantages over conventional continuous wave radio communications including potential support for high data rates, robustness to multipath interference and fading. We present an overview of UWB technology and its use in data communications and networking. We look at design considerations for UWB based networks at various layers of the protocol stack.1.INTRODUCTIONUltra-Wideband [1-6]一also known as baseband or impulse radio一is a carrier-free radio transmission that uses narrow, extremely low power pulses of radio energy spread across a wide spectrum of frequencies. UWB has recently gained a great deal of interest due to the recent Federal Communications Commission (FCC) Report and Order which allocates the UWB band一7.5 GHz of unlicensed spectrum for indoor and outdoor communication applications. UWB communications are required to have a -10 dB fractional bandwidth of more than 20% or a -10 dB bandwidth of more than 500 MHz [7]. It is important to note that the FCC has not defined a specific modulation scheme to be used. UWB systems offer the promise of high data rate, low susceptibilityto multipath fading, high transmission security low prime power requirements, low cost, and simple design [1,2,5,6].UWB has been used in military applications for the past several years for ground-penetrating precision radar applications and secure communications [3,8]. For the past few years, UWB has been developed for commercial applications [1,2,5,6]. With the recent FCC [7] report and order for theuse of UWB technology, there has been an added impetus to this endeavor. Other notable UWB applications include collision avoidance radar, tagging/identification; geolocation [9] and data communications in personal area networks (PAN) and local area network (LAN) environments.There are several future challenges to the wide adoption of UWB for wireless data communications including the infancy of the technology in the commercial arena, lack of reliablechannel models, the early stages of standardization effort and lack of low-cost system on chip (SoC) implementations. In this paper, we look at UWB technology for data communications and inside a UWB physical (PHY) layer characteristics. We also briefly introduce other related wireless standards such as 802.11 [10], 802.15.3 [11-13] Bluetooth [14], HomeRF [15] and HIPERLAN [16] and present a brief synopsis of the regulatory effort worldwide with special emphasis on the FCC. We also present the design considerations for UWB based data networking.2.ULTRA-WIDEBAND TECHNOLOGYThe basic waveform that employed in a UWB system is an approximation to an impulse, such as that shown in Fig. 1. The short duration of the pulse is associated with large inherent bandwidth; hence, the nomenclature "Ultra-Wideband". Typical attributes of UWB waveforms are summarized in Table 1.Fig. 1. UWB waveform example.The high spectral content of the UWB waveform gives rise to one of the primary advantages UWB operation for communications where a UWB system is robust against multipath fading[17] and narrowband interference [18]. In multipath fading, where the transmitted radio frequency (rt) signal can reflect off objects in its transmission path and can cause destructive interferences at the receiver, a loss of reception can occur. ThisTable 1: Characteristics of Typical UWB SystemsFractional Bandwidth > 20%Pulse Width 0.1-2 asPulse Repetition Frequency 1 kHz-2 GHzAverage Transmitted Power<1mWeffect is particularly problematic indoors where there are many reflecting surfaces. In the frequency domain, multipath is shown as frequency selective fading. Because UWB communications systems spreads the transmitted data over a broad frequency band if destructive interference occurs at a specific frequency, whether due to multipath or narrowband interference, the information can still be recovered over the good frequencies.UWB implementations can provide low complexity, low cost solutions [19], thus enabling vast deployments of the technology. A critical component that reaffirms a low cost solution is noting that UWB signals, being carrier-less, have greater simplicity over narrowband transceivers and require smaller silicon die sizes [20]. UWB can be designed to achieve very high bit rates while still achieving low power consumption, a feature set which will be exploited by the consumer electronics industry [21]. UWB schemes can further be designed to be very scalable in terms of complexity, bit rate, power consumption, and range.UWB technology can support many applications. Different UWB modulation schemes offer different advantages for communication, radar, and precisiongeo-location applications. UWB technology, which operates between 3.1 and 10.6 GHz, intrinsically offers an efficient reuse of precious spectrum by operating stealthily at the noise floor [22]. This UWB system operates at low power, to be compliant with operating under FCC Part 15 emissions, across a wide range of frequencies. As a spread spectrum technology, UWB offers a low probability of intercept and a low probability of detection [8]. Thus, it is particularly well suited for covert military or sensitive usage seenarios [8]. Because UWB signals have extremely short bursts in time (e.g., durations of 1 ns or less) they are suited for precision geo-location applications. Though UWB intrinsically offers the above-mentioned features, application optimization and improvements on these characteristics are left to specific designs and implementations, most notably by careful consideration of modulation schemes.2.1. UWB System Design ConsiderationsSeveral considerations are needed when designing a PAN. First, low power design is necessary because the portable devices within the network are battery powered. Second, high data rate transmission is crucial for broadcasting multiple digi\tal audio and video streams: Lastly, low cost is a prerequisite to broadening consumer adoption. In addition to these criteria, the UWB system designer must address synchronization and coexistence. Capturing and locking onto these short pulses make synchronization a non-trivial task. Coexisting peacefully with other wireless systems without interference is important;In particular, one needs to pay attention to the 802.1 la wireless LANs that operate in the 5 GHz ISM bands.At the physical layer, additional challenges lie in the transceiver and antenna design. At the transmitter, pulse shaping is required to produce flat and wideband emission in the desired frequency bands. Although new integrated circuits provide less expensive forms of integration, the pulses can be affected by the parasitics from the component and packaging [23]. To accommodate the high data rates, tradeoffs between high and low pulse repetition frequency (PRF) and modulation schemes must be considered. The low PRF system with higher modulation (more bits per symbol) may require a more complex receiver, while the high PRF system with lower modulation may lead to performance degradation for delay spread in the channel. Finally, traditional antenna designs gear towards narrow band systems. To avoid dispersion at the receiver, the new wideband antennas need phase linearity and a fixed phase center [23].3. UWB STANDARDIZATION ANDREGULATORY EFFORTSThere are several standards bodies presently considering, at some level, UWB technologies. The standards body most advanced in the consideration of UWB is study group "a" of IEEE 802.15.3, which was formed in November 2001 [11-13]. A serious effort is well underway to define a UWB channel model, and numerous UWB tutorials have been given. Many hallway conversations talk to a physical layer standard being ratified in 2004 (though there is no formal knowledge or position on this) and will accompany the soon to be approved 802.15.3 Medium Access Control (MAC) which supports quality of service (QoS) for real-time multimedia applications [12]. The technical requirements presently call for bit rates of 110 to 200 Mbps at ranges up to 10 m, with the option to achieve 480 Mbps possibly at shorter distances. The powerconsumption requirement is presently set at 100 to 250 mW with lOe 5 bit error rate at the top of the physical layer. Complexity/cost are presently expected to be comparable to Bluetooth and the physical layer is required to support four collocated piconets. Coexistence is presently crucial (e.g., IEEE 802.1 la) and the ability to scale the technology is key to a long lasting and widely adopted standard. These technical requirements come from documents that are still being revised; additionally, it is not possible to predict if proposals may fall short of meeting some of the desired requirements.The United States FCC issued a report and order in the early part of 2002. This landmark decision to permit UWB operation in the 3.1 to 10.6 GHz spectrum under Part 15 emis- sion limits, with some additional restrictions, has catalyzed development and standardization processes as is evident by the sheer number of entities (companies, academic and government institutions) associated with UWB and through the serious efforts of the IEEE 802.15.3 group. The FCC carefully chose the frequency band of operation to be above 3.1 GHz to avoid interfering with GPS and other life critical systems. Furthermore, the FCC ruled that emissions below Part 15 would pro-vide for peaceful coexistence, the ability to have narrowband and UWB systems collocated on a non-interfering basis, because unintentional emissions from devicessuch as laptops are also limited to Part 15 rules. This ruling makes it possible to have up to 15 UWB frequency bands in the 7.5 GHz allocated unlicensed spectrum [7]. Extensive efforts are being conducted throughout Europe (CEPT, ETSI, and the European Commission), Korea, and Japan (Association of Radio Industries and Businesses, and the Japanese Ministry of Telecommunications).4. NETWORKING WITH UWB SYSTEMSThere is a significant interest in the ability to perform location determination and tracking of assets and people throughout warehouses, factories, ships, hospita梦，business environments, and other buildings or structures. The ability for UWB technologies to operate within such intense multipath environments in conjunction with the ability for UWB to provide very accurate geo-location capability at low cost and long battery life justifies the increasing technological activity in this market [20].As the rf tags [24] are distributed, it is also recognized tha they can be coordinated and networked. To further reduce the cost of the transceivers, position determination can occur at networked computer terminals. Additionally, it is quite conceivable that tag complexity can be further simplified by installink transmitters that chirp periodically [8]. Just as UWB demonstrates many benefits for rf tags, the technology equally lends itself to distributed sensor networks [9]. Sensor network applications include feedback controls systems and environmental surveillance for commercial, industrial,_ and military applications.In the data communication area, UWB technology may be used to implement ad-hoc networks. An ad-hoc network [25-27] is characterized by a collection of hosts that form a network "on-the-fly". An ad-hoc network is a multi-hop wireless network wherein each host also acts as a router. Mobile TRANSPORT Ad-hoc NETworks (MANETs) [25-27] are ad-hoc networks wherein the wireless hosts have the ability to move. Mobility of hosts in MANETs has a profound impact on the topology of the network and its performance. Figure 2 illustrates how the various layers of the OSI protocol stack have to operate in order to successfully complete a communication session. We look at some of relevant design issues at the different layers for UWB-based sensor networks and MANETs.4.1. Design Issues for Layers of the Protocol StackThere are several design considerations of sensor networks setup (including rftags) [24]. The sensors typically work on batteries and need be low cost, low power, with LPI/LPD and the ability to do geo-location. All of these requirements are satisfied by a UWB PHY.The PHY layer [26,27] is a very complex layer which deals with the medium specification (physical, electrical and mechanical) for data transmission between devices. The PHY layer specifies the operating frequency range, the operating temperature range, modulation scheme, channelization scheme. channel switch time, timing, synchronization, symbol coding, and interference from other systems, carrier-sensing and transmit/receive operations of symbols and power requirements for operations. The PHY layer interacts closely with, the MAC sublayer to ensure smooth performance of the network. The PHY layer for wireless systems (such as MANETs) has special considerations to take into account as the wireless medium is inherently error-prone and prone to interference from other wireless and rf systems in the proximity. Multipath is important to consider when designing wireless PHY layer as the rf propagation environment changes dynamically with time; frequent disconnections may occur. The problem is exacerbated when the devices in the network are mobile because of handoffs and new route establishment. It should be noted that there is a concerted effort by several UWB companies muster supportfor a UWB-based high data rate PITY in the IEEE 802.15.3 working group.The data link layer consists of the Logical Link Control (LLC) and the MAC sub layers. The MAC sublayer is responsible for channel access and the LLC is responsible for link maintenance, framing data unit, synchronization, error detection and possible recovery, and flow control. The MAC sublayer tries to gain access to the shared channel to prevent collision and distortion of transmitted frames with frames sent by the MAC sublayers of other nodes sharing the medium. TheMAC sublayer in sensor networks and MANETs needs to be power-aware, self-organizing and support mobility and handoffs.The network layer of such networks should perform routing so as to minimize power and the number of node hops in the route. In some cases, flooding/gossiping may be required to increase chances of the packets reaching the destination. Data aggregation/fusion may be used for. data-centric routing [24] in the network layer. The network layer needs to allow for route maintenance and updates for fast changing network topology.The transport layer is responsible for the end-to-end integrity of data in thenetwork. The transport layer performs multiplexing, segmenting, blocking, concatenating, error detection and recovery, flow control and expedited data transfer. In the MANET environment, the mobility of the nodes will almost certainly cause packets to be delivered out of order and a significant delay in the acknowledgements is to be expected as a result. Retransmissions are very expensive in terms of the power requirements. Transport protocols for MANETs and sensor networks need to focus on the development of feedback mechanisms that enable the transport layer to recognize the dynamics of the network and adjust its retransmission timer, window size and perform congestion control with more information on the network.Fig. 2. Issues at each layer of the protocol stackThe application layer needs support for location-based services, network management, task assignment, query and data dissemination for sensor networks and possible MANETs.5. RELATED TECHNOLOGIESIn order to better understand UWB-based technologies, we look at some related technology standards. More information on these technologies can be found in Ref. 27.5.1. BluetoothBluetooth [14] is a short-range radio technology standard originallyintended as a wireless cable replacement to connect portable computers, wireless devices, handsets and headsets. Bluetooth devices operate in the 2.4 GHz ISM band. Bluetooth uses the concept of a piconet which is a MANET with a master device controlling one or several slave devices. Bluetooth also allow scatternets wherein a slave device can be part of multiple piconets. Bluetooth has beed designed to handle both voice and data. traffic.5.2. HIPERIANl1 and HIPERIANIlHIPERLAN/I and HIPERLAN/2 [16] are European wireless LAN (WLAN) standards developed by European Telecommunications Standards Institute (ETSI). HIPERLAN/1 is a wireless equivalent of Ethernet while HIPERLAN/2 has architecture based on wireless Asynchronous Transfer Mode (ATM). Both the standards use dedicated frequency spectrum at -5 GHz. HIPERLAN/I provides a gross data rate of 23.5 Mb/s and net data rate of more than 18 Mb/s while HIPERLAN/2 provides gross data rates of 6/16/36154 Mb/s and a maximum of 50 Mb/s net data rate. Both standards use 10/100/1000 mW of transmit power and have a maximum range of 50 m. Also, the standards provide isochronous and asynchronous services with support for QoS. However, they have different channel a-ss and modulation schemes.5.3. IEEE 802]]This IEEE family of wireless Etherdet standards is primarily intended for indoor and in-building WLANs. There are several varities of this standard. The current available versions are the 802.1 la, 802.11b and 802.llg (emerging draft standard) with other versions which are starting to show on the horizon [10]. The 802.11 standards support ad-hoc networking as well as connections using an access point (AP). The standard provides specifications of the PHY and the MAC layers. The MAC specified uses CSMA/CA for access and provides service discovery and scanning, link setup and tear down, data fragmentation, security, power management and roaming facilities. The 802.1 la PHY is similar to the HIPERLAN/2 PHY. The PHY uses OFDM and operates in the 5 GHz UNII band. 802.1 la supports data rates ranging from 6 to 54 Mbps. 802.11 a currently offers much less potential for rf interference than other PHYs (e.g., 802.11b and 802.11g) that utilize the crowded 2.4 GHz ISM band. 802.11 a can support multimedia applications in densely populated user environments.' The 802.11b standard, proposed jointly by Harris and Lucent Technologies, extends the 802.11 Direct Sequence Spread Spectrum (DSSS) PHY to provide 5.5 and 11 Mb/s data rates.5.4. IEEE 802.75.3The emerging draft standard [11-13] defines MAC and PHY (2.4 GHz) layer specifications for a Wireless Personal Area Network (WPAN). The standard is based on the concept of a piconet which is a network confined to a 10 m personal operating space (POS) around a person or object. A WPAN consists of one or more collocated piconets. Each piconet is controlled by a piconet coordinator (PNC) and may consist of devices (DEVs). The 802.15.3 PHY is defined for 2.4 to 2.4835 GHz band and has two defined channel plans. It supports five different data rates (11 to 55 Mb/s). The base uncoded PHY rate is 22 Mb/s5.5. HomeRFHomeRF [15] working group was formed to develop a standard for wireless data communication between personal computers and consumer electronics in a home environment. The HomeRF standard is technically solid, simple, secure, and is easy to use. HomeRF networks provide a range of up to 150 ft typically enough for home networking. HomeRF uses Shared Wireless Access Protocol (SWAP) to provide efficient delivery of voice and data traffic. SWAP uses a transmit power of up to 100 mW and a gross data rate of 2 Mb/s. It can support a maximum of 127 devices per network. A SWAP-based system can work as an ad-hoc network or as a managed network using a connection point6. CONCLUSIONIn this paper, we presented an overview of UWB technology and its characteristics and advantages over conventional, continuous wave transmissions. We presented how UWB is well suited for several applications like sensor networks and MANETs. UWB technology has garnered a lot of interest among vendors who are looking at standardizing the use of the technology in various forums including IEEE.中文翻译超宽带系统的数据通信G. Racherla, J.L. Ellis, D.S. Furuno, S.C. LinGeneral Atomics, Advanced Wireless Group10240 Flanders Ct.San Diego CA 92121E-mail: {gopal.racherla, jason.ellis, susan.lin,超宽带（UWB）是一种在宽频谱范围内使用超低功耗传播无线脉冲能量的无线电传输方案。

数据通信英语作文Nowadays, data communication has become an essential part of our daily lives. Nowadays, data communication has become an essential part of our daily lives. (如今，数据通信已经成为我们日常生活的一个重要组成部分。

The importance of data communication can be seen in various aspects of our lives, from the way we interact with our loved ones to the way businesses operate. 数据通信的重要性在我们生活的各个方面都可以看到，从我们与亲人互动的方式到企业运营的方式。

In our personal lives, data communication allows us to stay connected with our friends and family no matter where they are in the world. 在我们的个人生活中，数据通信让我们能够与朋友和家人保持联系，无论他们身在何处。

Through social media platforms, instant messaging apps, and video calls, we are able to share our experiences, emotions, and memories with the people we care about, bridging the physical distancesbetween us. 通过社交媒体平台、即时通讯应用和视频通话，我们能够与我们关心的人分享我们的经历、情感和回忆，弥合我们之间的物理距离。

CDMA versus TDMATerm Paper :DTEC 6810Submitted by:Sabareeshwar Natarajan.Fall 2006DTEC 6810Communication TechnologyCDMA Vs TDMA in travel:Both GSM and CDMA can be found across United States, which doesn’t mean that it doesn’t matter which technology we choose. When we travel domestically it is possible that we reach areas where digital service is not available. While traveling between places it is possible that we reach certain rural areas were only analog access is offered. CDMA handsets offer analog capabilities which the GSM don’t offer. Another difference between GSM and CDMA is in the data transfer methods. GSM’s high-speed wireless data technology, GPRS (General Packet Radio Service), usually offers a slower data bandwidth for wireless data connection than CDMA’s high-speed technology, which has the capability of providing ISDN (Integrated Services Digital Network) with speeds as much as 144Kbps.GSM’s benefits over the CDMA in domestic purpose are that GSM uses SIM card that identifies a user and stores the information in the handset. The SIM card can be swapped between handsets, which enable to move all the contacts to the new handset with ease. CDMA can have this flexibility with their own service that stores data on the operator’s datab ase. This service allows the user to swap data’s between two handsets with a little trouble, but the advantage is it can be done when the handset is even lost but in GSM technology, when a handset is lost, SIM card is also lost with it.When it comes for international roaming handsets with GSM is far better than CDMA handsets because GSM is used in most the markets across the globe. Users using tri-band or quad-band can travel to Europe, India and most of Asia and still can use their cell phone. CDMA does not have this multiband capability, thus cannot be used multiple countries with ease.Differences between CDMA and TDMA:CDMA technology claims that its bandwidth is thirteen times efficient than TDMA and forty times efficient than analog systems. CDMA also have better security and higher data and voice transmission quality because of the spread spectrum technology it uses, which has increased resistance to multipath distortion. The battery life is higher in TDMA compared to CDMA because CDMA handsets transmit data all the time and TDMA does not require constant transmission. CDMA has greater coverage area when compared to TDMA. Though, when it comes to international roaming TDMA is better than CDMA. CDMA is patented by Qualcomm, so an extra fee is paid to Qualcomm. When it comes to United States and Canada market size for CDMA is larger than GSM’s market size but worldwide the market size for GSM is far bigger both in the number of subscribers and coverage ,than CDMA.Conclusion:From the comparisons made above we cannot say that TDMA is better than CDMA or vice versa. The main advantage of the CDMA is that, in the single detection method it is more flexible than TDMA or joint detection. CDMA is said to have higher capacity than TDMA. But in the future GSM can be extended by an optional CDMA component in order to further increase the capacity. Finally, it does not matter whether which one is better CDMA or TDMA right now. It can be only found out with the evolution of these technologies. When going for a cell phone the user should choose the technology according to where they use it. For users who travel abroad it is better to go with GSM handsets. For the users in United States CDMA is better than TDMA because of the coverage we can get at rural areas where digital signals cannot be transmitted.CDMA与TDMA学期论文：6810 DTEC提交：sabareeshwar纳塔拉詹。

一、英文原文Modern mobile communication technologyIn now highly the information society, the information and the correspondence have become the modern society “the life”. The information exchange mainly relies on the computer correspondence, but corresponds takes the transmission method, with the sensing technology, the computer technology fuses mutually, has become in the 21st century the international society and the world economic development powerful engine. In order to of adapt the time request, the new generation of mobile communication technology seasonable and lives, the new generation of mobile communication technology is the people said that third generation's core characteristic is the wide band addressing turns on non-gap roaming between the rigid network and numerous different communications system's, gains the multimedia communication services.Along with the time progress, the technical innovation, people's life request's enhancement, the mobile communication technology renewal speed is quite astonishing, almost every other ten year mobile communication technology has a transformation update, from the 1980s “the mobile phone” to present's 3G handset, during has had two mobile communication technology transformation, transits from 1G AMPS to 2G GSM, from GSM to IMT-2000 (i.e. 3G technology). Knows modern on me the mobile communication technology to have the following several aspect important technology:1. wideband modulation and multiple access techniqueThe wireless high speed data transmission cannot only depend on the frequency spectrum constantly the expansion, should be higher than the present number magnitude at least in the frequency spectrum efficiency, may use three technologies in the physical level, namely OFDM, UWB and free time modulation code. OFDM with other encoding method's union, nimbly OFDM and TDMA, FDMA, CDMA, SDMA combines the multiple access technique.In the 1960s the OFDM multi-channel data transmission has succeeded uses in complex and the Kathryn high frequency military channels. OFDM has used in 1.6 M bit/s high bit rate digital subscriber line (HDSL), 6 M bit/s asymmetrical digital subscriber line (ADSL), 100 M bit/s really high speed figure subscriber's line (VDSL), digital audio frequency broadcast and digital video broadcast and so on. OFDM applies on 5 GHz provides 54 M bit/s wireless local network IEEE 802.11 a and IEEE 802.11g, high performance this region network Hi per LAN/2 and ETSI-BRAN, but also takes metropolitan area network IEEE 802.16 and the integrated service digit broadcast (ISDB-T) the standard. Compares with the single load frequency modulation system service pattern, the OFDM modulation service pattern needs to solve the relatively big peak even power ratio (PAPR, Peak to Average Power Ratio) and to the frequency shifting and the phase noise sensitive question.High speed mobile communication's another request is under the wide noise bandwidth, must demodulate the signal-to-noise ratio to reduce as far as possible, thus increases the cover area. May adopt the anti-fading the full start power control and the pilot frequency auxiliary fast track demodulation technology, like the frequency range anti-fading's Rake receive and the track technology, the OFDMA technology which declines from the time domain and the frequencyrange resistance time and the frequency selectivity, the link auto-adapted technology, the union coding technique.2. frequency spectrum use factor lift techniqueThe fundamental research pointed out: In the independent Rayleigh scattering channel, the data rate and the antenna several tenth linear relationships, the capacity may reach Shannon 90%. Is launching and the receiving end may obtain the capacity and the frequency spectrum efficiency gain by the multi-antenna development channel space. The MIMO technology mainly includes the spatial multiplying and the space diversity technology, concurrent or the salvo same information enhances the transmission reliability on the independent channel.Receives and dispatches the bilateral space diversity is the high-capacity wireless communication system uses one of technical. Bell Lab free time's opposite angle BLAST (D-BLAST) capacity increase to receive and dispatch the bilateral smallest antenna number in administrative levels the function. The cross time domain which and the air zone expansion signal constitutes using MIMO may also resist the multi-diameter disturbance. V-BLAST system when indoor 24~34 dB, the frequency spectrum use factor is 20~40 bit/s/Hz. But launches and the receiving end uses 16 antennas, when 30 dB, the frequency spectrum use factor increases to 60~70 bit/s/Hz.The smart antenna automatic tracking needs the signal and the auto-adapted free time processing algorithm, produces the dimensional orientation wave beam using the antenna array, causes the main wave beam alignment subscriber signal direction of arrival through the digital signal processing technology, the side lobe or zero falls the alignment unwanted signal direction of arrival. The auto-adapted array antennas (AAA, Adaptive Array Antennas) disturbs the counter-balance balancer (ICE, Interference Canceling Equalizer) to be possible to reduce disturbs and cuts the emissive power.3. software radio technologyThe software radio technology is in the hardware platform through the software edition by a terminal implementation different system in many kinds of communication services. It uses the digital signal processing language description telecommunication part, downloads the digital signal processing hardware by the software routine (DSPH, Digital Signal Processing Hardware). By has the general opening wireless structure (OWA, Open Wireless Architecture), compatible many kinds of patterns between many kinds of technical standards seamless cut.UWB is also called the pulse to be radio, the modulation uses the pulse width in the nanosecond level fast rise and the drop pulse, the pulse cover frequency spectrum from the current to the lucky hertz, does not need in the radio frequency which the convention narrow band frequency modulation needs to transform, after pulse formation, may deliver directly to the antenna launch.4. software radio technologyThe software radio technology is in the hardware platform through the software edition by a terminal implementation different system in many kinds of communication services. It uses the digital signal processing language description telecommunication part, downloads the digital signal processing hardware by the software routine (DSPH, Digital Signal Processing Hardware). By has the general opening wireless structure (OWA, Open Wireless Architecture), compatible many kinds of patterns between many kinds of technical standards seamless cut.5. network security and QoSQoS divides into wireless and the wired side two parts, wireless side's QoS involves theradio resource management and the dispatch, the admission control and the mobility management and so on, the mobility management mainly includes the terminal mobility, individual mobility and service mobility. Wired side's QoS involves based on the IP differ discrimination service and the RSVP end-to-end resources reservation mechanism. Mechanism maps the wireless side IP differ IP the QoS. Network security including network turning on security, core network security, application security, safety mechanism visibility and configurable.In the above modern mobile communication key technologies' foundation, has had the land honeycomb mobile communication, the satellite communication as well as the wireless Internet communication, these mailing address caused the correspondence appearance to have the huge change, used the digital technique the modern wireless communication already to permeate the national economy each domain and people's daily life, for this reason, we needed to care that its trend of development, hoped it developed toward more and more convenient people's life's direction, will let now us have a look at the modern mobile communication the future trend of development.modern mobile communication technological development seven new tendencies :First, mobility management already from terminal management to individual management and intelligent management developmentSecond, network already from synchronized digital circuit to asynchronous digital grouping and asynchronous transfer mode (ATM) development;the three, software's developments actuated from the algorithm to the procedure-oriented and face the goal tendency development;the four, information processing have developed from the voice to the data and the image;five, wireless frequency spectrum processing already from narrow band simulation to the narrow band CDMA development;the six, computers have developed from central processing to the distributional server and intellectualized processing;the seven, semiconductor devices have developed from each chip 16,000,000,000,000 /150MHz speed VLSI to 0.5 /350MHz speed VLSI and 2,000,000,000,000,000 /550MHz speed VLSI.Under this tendency's guidance, the mobile service rapid development, it satisfied the people in any time, any place to carry on the correspondence with any individual the desire. The mobile communication realizes in the future the ideal person-to-person communication service way that must be taken. In the information support technology, the market competition and under the demand combined action, the mobile communication technology's development is progresses by leaps and bounds, presents the following several general trends: work service digitization, grouping; 2. networking wide band; working intellectualization; 4.higher frequency band; 5. more effective use frequency; 6.each kind of network tends the fusion. The understanding, grasps these tendencies has the vital practical significance to the mobile communication operator and the equipment manufacturer.二、英文翻译现代移动通信在当今高度信息化的社会，信息和通信已成为现代社会的“命脉”。

关于数字通讯的英语作文In today's era of rapid technological advancements, digital communication has revolutionized the way we interact, learn, and work. Its influence is felt across all aspects of life, from personal relationships to global businesses. The transformation from analog to digital communication has been nothing short of remarkable, and its impact on society is profound.The advent of digital communication marked asignificant milestone in the history of technology. It began with the early forms of computer-based communication, such as email and file sharing, which enabled people to send and receive information electronically. Over time, digital communication evolved to include more sophisticated technologies like the internet, smartphones, and social media platforms.The internet, in particular, has been a catalyst for the rapid growth of digital communication. It has created a global network of interconnected computers that allows for the exchange of information in real-time. This has made it easier for people to stay connected, regardless of theirlocation. Social media platforms have furthered this connectivity by providing users with a medium to sharetheir thoughts, experiences, and ideas with a wider audience.The rise of digital communication has had a profound impact on the way we communicate. It has made communication more efficient and convenient, allowing us to send messages, share photos and videos, and stay updated with news and events in real-time. Digital communication has also made it easier to build and maintain relationships, as people can stay connected even when they are far apart.However, the rise of digital communication has not been without its challenges. One of the main concerns is the issue of privacy and security. As more and more personal information is shared online, the risk of privacy breaches and cyber-attacks has increased. It is crucial that we are vigilant about protecting our personal information andusing secure communication methods to mitigate these risks. Despite these challenges, the future of digital communication looks bright. With the advent of new technologies like 5G, the internet of things, andartificial intelligence, digital communication is poised to become even more efficient, convenient, and intelligent. These technologies will enable faster data transmission, enhanced connectivity, and more personalized communication experiences.In conclusion, digital communication has revolutionized the way we interact and communicate with each other. It has brought about remarkable changes in the way we live and work, and its impact on society is profound. While we must be mindful of the challenges that come with it, such as privacy and security concerns, the future of digital communication holds great promise for further enhancing our communication capabilities and experiences.**数字通讯的演变和影响**在当今科技飞速发展的时代，数字通讯已经彻底改变了我们互动、学习和工作的方式。

论文附件一、英文原文：Introduction to Wireless Communication SystemsThe ability to communicate with people on the move has evolved remarkably since Guglielmo Marconi first radio's ability to provide continuous contact with ships sailing the English channel. That was in 1897, and since then new wireless communications methods and services have been enthusiastically adopted by people throughout the world. Particularly during the past ten years, the mobile radio communications industry has grown by orders of magnitude, fueled by digital and RF circuit fabrication improvements, new large-scale circuit integration, and other miniaturization technologies which make portable radio equipment smaller, cheaper, and more reliable. Digital switching techniques have facilitated the large scale deployment of affordable, easy-to-use radio communication networks. These trends will continue at an even greater pace during the next decade.1.1 Evolution of Mobile Radio CommunicationsA brief history of the evolution of mobile communications throughout the world is useful in order to appreciate the enormous impact that cellular radio and Personal Communication Services(PCS) will have on all of us over the next several decades. It is also useful for a newcomer to the cellular radio field to understand the tremendous impact that government regulatory agencies and service competitors wield in the evolution of new wireless systems, services, and technologies. While it is not the intent of this text to deal with the techno-political aspects of cellular radio and personal communications, second-politics are a fundamental driver in the evolution of new technology and services, since radio spectrum usage is controlled by governments, not by service technology development manufacturers, entrepreneurs, or researchers. Progressive involvement in technology development is vital for a government if it hopes to keep its own country competitive in the rapidly changing field of wireless personal communications.Wireless communications is enjoying its fastest growth period in history, due to enabling technologies which permit widespread deployment. Historically, growth in the mobile communications field has come slowly, and has been couple closely to technological improvements. The ability to provide wireless communications to an entire population was not even conceived until Bell Laboratories development of cellular concept in the 1960s and 1970s [Nob62], [Mac79], [You79]. With the development of highly reliable, miniature, solid-state radio frequency hardware in the 1970s,the wireless communications era was born. The recent exponential growthin cellular technologies of the 1970s, which are mature today. The future growth of consumer-based mobile and portable communication systems will be tied more closely to radio spectrum allocations and regulatory decisions which affect or support new or extended services, as well as to consumer needs and technology advances in the signal processing, access, and network areas.The following market penetration data show how wireless communications in the consumer sector has grown in popularity. Figure 1.1 illustrates of the 20th century. Figure 1.1 is a bit misleading since the curve labeled "mobile telephone" does not include nontelephone mobile radio applications, such as paging, amateur radio, dispatch, citizens band(CB), public service, cordless phone, or terrestrial microwave radio systems. In fact, in 1990, licensed noncellular radio systems in the U.S. had over 12 million users,more than twice the U.S. cellular users population at that time [FCC91]. With the phenomenal growth of wireless subscribers in the late 1990s, combined with Nextel's novel business approach of purchasing private mobile radio licenses for bundling as a nationwide commercial cellular service, today's subscriber base for cellular and Personal Communication Services(PCS) far outnumbers all noncellular licensed users. Figure 1.1 shows that the first 35 years of mobiletelephony saw little market penetration due to high cost and the technological challenges involved, but how, in the past decade, wireless communications has been accepted by consumers at rates comparable to television and the video cassette recorder.By 1934. 194 municipal police radio systems and 58 state police stations had adopted amplitude modulation(AM) mobile communication systems for public safety in the U.S. It was estimated that 5,000 radios were installed in mobiles in the mid 1930s, and vehicle ignition noise was a major problem for these early mobile uses [Nob62]. In 1935,Edwin Armstrong demonstrated frequency modulation(FM) for the first time, and since the late 1930s, FM has been the primary modulation technique used for mobile communication systems throughout the world. World War II accelerated the improvements of the world's manufacturing and miniaturization and televison systems following the war. The number of U.S. mobile users climbed from several thousand in 1940 to 86,000 by 1948, 695,000 by 1958, and about 1.4 million users in 1962[Nob62]. The vast majority of mobile users in the 1960s were not connected to the public switched telephone network. With the boom in CB radio and cordless appliances such as garage door openers and telephones, the number of users of mobile and portable radio in 1995 was about 100 million, or 37% of the U.S. population. Research in 1991 estimated between 25 and 40 million cordless telephone were in use in the U.S.[Rap91c], and this number is estimated to be over 100 million as of late 2001. The number of worldwide cellular telephone users grew from 25,000 in 1984 to about 25 million in 19993[Kuc91], [Goo91], [ITU94], and since then subscription-based wireless services have been experiencing customer growth rates well in excess of 50% per year. As shown in Chapter 2, the worldwide subscriber base of cellular and PCS subscribers is approximately 630 million as of late 2001, compared with approximately 1 billion wired telephone line. In the first few years of 21st century, it is clear there will be an equal number of wireless andconventional wireline wireless subscriber population had already abandoned wired telephone service for home use, and had begun to rely solely on their cellular service provider for telephone access. Consumers are expected to increasingly use wireless service as their sole telephone access method in the years to come.1.2 Mobile Radiotelephony in the U.S.In 1946, the first public mobile telephone service was introduced in twenty-five major American cities. Each system used a single, high-powered transmitter and large tower in order to cover distances of over 50 km in a particular market. The early FM push-to-talk telephone systems of the late 1940s used 120 kHz of RF bandwidth in a half-duplex mode(only one person on the telephone call could talk at a time), even though the actual telephone-grade speech occupies only 3 kHz of base-band spectrum. The large RF bandwidth was used because of the difficulty in mass-producing tight mobile telephone channels per market, but with no new spectrum allocation. I,proved technology enabled the channel bandwidth to be cut in half to 60 kHz. By the mid 1960s, the FM bandwidth of voice transmissions was cut to 30 kHz. Thus, there was only a factor of four increase in spectrum efficiency due to technology advances from WW II to the mid 1960s. Also in the 1950s and 1960s, automatic channel trunking was introduces and implemented under the label IMTS(Improved Mobile Telephone Service). With IMTS, telephone companies began offering full duplex, auto-dial, auto-trunking phone systems[Cal88]. However, IMTS quickly became saturated in major markets.By 1976, the Bell Mobile Phone service for the NEW York City market(a market of about 10,000,000 people at the time) had only twelve channels and could serve only 543 paying customers. There was a waiting list of over 3,700 people [Cal88], and service was poor due to call blocking and usage over the few channels. IMTS is still in use in the U.S., but is very spectrally inefficient when compared to today's U.S. cellular system.二、英文翻译：无线通信系统介绍自从马可尼在英吉利海峡首先证实了无线电波能保证持续不断的与海上航行的船只保持联系，移动通信便有了显著的发展。

Abstract- With the rapid development of computer network technology, the security of computer network becomes increasingly important. Three main threats facing computer network security include: hackers, computer virus and denial of service attack. Things leading to the safety of the network are mainly: resources sharing, data communication, computer virus and TCP/IP protocol security flaws. A safety network system should include at least three kinds of measures: legal measures, technical measures and review and management measures. The paper analyzes the main threat facing computer network security, discusses network security technology and advances some effective countermeasures in view of the hidden danger of current common network security.Keywords-network security; computer network; information security; security strategy; prevention strategyI.INTRODUCTIONWith the development of Internet technology, computer network gradually changes people's life and way of work. In the process of rapid popularization of computer network, hidden dangers of computer security become increasingly prominent. This requires us take strong measures to ensure the safety of the network. The computer network security refers to the use of network management to control and technical measures to ensure data privacy in a network environment. But as computer network is open, sharing and international, it makes computer network more vulnerable. In order to solve this problem, now people mainly research in the field of data encryption technology, identity authentication, firewall, network management and thatII.CONCEPT OF COMPUTER NETWORK SECURITYThe computer network security refers to the use of network management to control and technical measures to ensure that in a network environment, the data privacy, integrity and availability can be protected. The computer network security includes two aspects: physical security and logic security. The physical security system means that equipment and related facilities are protected from destruction, loss, etc. Logic security includes the integrity of information, secrecy and availability. The meaning of computer network security varies from users to users. Different users have different understanding of network safety requirements. To general users who may just wantindividual privacy or confidential information on the network transmission to be protected and to avoid being eavesdropping, tampering and forge. But for network providers, they not only care about the network information safety, but also consider how to cope with sudden natural disasters, such as a military strike to network hardware damage, as well as how to restore network communication and maintain the continuity of network communication in abnormal situations.Essentially, network security include hardware that compose network system, software and its transfer over a network information safety, which protected it from accidental or malicious attack, network security concerns both technical problems and management issues, which are in complement with each other.III.MAJOR THREATS OF COMPUTER NETWORKA.Internal interception and DestructionThe people inside of network system may become the following possible threats: internal confidential personnel's intentionally or unintentionally leaks, the change of the record information; internal unauthorized personnel's intentionally or not, stealing confidential information, change the network configuration and record information; network system damage from Internal personnel.B.Unauthorized AccessUnauthorized access refers to the unauthorized use of network resources or unauthorized ways to use the network resources. It includes illegal users' hacking into the network or illegal operation system, and legitimate users' unauthorized way of operation.C.Damage the Integrity of InformationAttackers may damage the information integrity from three aspects: changing the order of the information flow, timing, changing the content, the form of information; Deleting news or some of the news; and Inserting some information in the news, making the receiver not able to read or receive the wrong information[2].D.InterceptionThrough the wiretapping or the electromagnetic wave radiation within the scope of the installation, the attacker may intercept confidential information, or through to the information flow, communication frequency and length of6452012 International Conference on Computer Science and Information Processing (CSIP)the parameters find out useful information. It does not damage the transfer information, and it is not easy examinable.E.PretendingThe attacker may pretend to do the following: pretend to be leadership issue orders and read the documents; Pretend to be host deceive legitimate hosts and legitimate users. Pretend to be network control program to show or modify the access to key information, passwords, etc, excessive use of network equipment and resources: take over a legitimate user, cheat the system, take up the resources of the legitimate users.F.Destroy System Availability.The attacker may damage from the following aspects of network system availability: making a legitimate user not able to have normal access to the network resources; Making a strict time required service not able to get the timely response and destroy system.G. Repeat ItselfRepeat itself refers that the attacker intercepted and record information, and then send these information repeatedly when necessary.H.DenialPossible denials are the sender's later denial of sending a piece of news content; the receiver later denied that he had received a message earlier.1.Other ThreatsThe threats of network system also include computer virus, electromagnetic leakage, all kinds of disasters, and the operating error, etc.IV. PROTECTIVE MEASURES OF COMPUTER NETWORK A.Technical Level CountermeasuresFrom technical level computer network security technology mainly include real-time scanning technology, real-time monitoring technology, firewall, completeness inspection protection technology, virus situation analysis report technology and system security management technology. The technical level can take the following measures:1) Establish a system of safety managementImprove the quality of stuff including system administrators and technical personnel professional and users. To the important department and information, strictly inspect virus in computer boot, backup data in time, which is a simple and effective method.2) Network access controlAccess control is the main strategy of network security and protection. Its main task is to guarantee that the network resources are protected from illegal use and access. It is one of the most important strategies of network security. The technology of access control involves many things such asnetwork access control, directory level control and attributes control[3].3) Database backup and recovery.Database backup and recovery is the important operation of database administrators to maintain data security and integrity. Restore database backup is the easiest and can prevent most accident. Recovery refers to the operation of using backup to restore data after accident. There are three main backup strategies: only backing up the database, backing up the database and affairs log and incremental backup.4) Application code technologyApplication code technology is the core technology of information security. Information security password is to provide a reliable guarantee. Based on code of digital signatures and identity authentication to guarantee that the main method of information integrity, one of which include classical code techniques, single key code system, public key code system, digital signature and key management.5) Cuting off the transmission wayCarry on a thorough antivirus examination on affected hard disk and the computer, don't use the unexplained USB disk and the program, don't download SUSpICIOUS information.6) Improve anti-virus technology of networkBy installing virus firewall, real-time filtering IS conducted. The files server on the network should be frequently scanned and monitored, using anti-virus software in the work site, strengthening the network directory and file access settings[4].7) Conduct research and development to improvethe operation of the high quality security system.Research and develop high security operating system, and don't give the virus hotbed to live, which would make computer network safer.B.Management Level CountermeasuresThe computer network security management not only depends on the security technology and preventive measures, but also depends on the management measures it takes and the protection laws and regulations it implements. Only by linking them closely can we make the computer network security really effective.The computer network security management includes educating users of computer safety, and setting up corresponding security management institution, continuous improvement and strengthening the management function, strengthen works on computer and network of the legislation and law enforcement, etc. Strengthen computer security management and enhance the user of the laws, regulations and moral concepts, improve computer users' awareness of safety, to prevent the computer crime and resistance to the hacker attacks and prevent computer virus interference, are all very important measures.This means the ongoing legal education on computer users, including computer security law, code, data and so on, make the right and obligation clearly to computer users and systems management personnel, consciously abide by the legal information system principle, legal principle, the6462012 International Conference on Computer Science and Information Processing (CSIP)principle of public information, information use principle and resource constraints principle. Consciously fight against all the behavior of the illegal crime, maintain the safety of the computer and network system, and the safety of the information system. In addition, we still should educate computer users and the staff, and obey all the rules and regulations set up for maintenance system safety, including personnel management system, operation maintenance and management system, computer processing control and management system, all kinds of material management system, computer room management system, special plane to defend the special division of work and strict management system.C.Physical Security Level CountermeasuresTo ensure the safety of computer network system's reliability we must ensure that there is a security system entity of the physical environment conditions. The safe environment refers to computer room and its facilities, mainly include the following content:1) Computer system environment conditionsThe computer system security environment conditions include temperature, humidity, air cleanliness, corrosion degrees, insect, vibration and impact, electrical disturbance and so on, which all have specific requirement and strict standards.2)Computer room environment selection control to identifY users' identity, and to verifY its validity; Secondly, visitors must define the scope of activities; Thirdly, multilayer safe protection should be set in the center of computer system to prevent illegal invasion of violence; Fourthly, buildings where equipment is located shall have equipment to protect against all kinds of natural disasters.V.CONCLUSIONThe computer network security is a complicated system of engineering, involving technology, equipment, management, system and so on, and security solutions should be set and understood from the whole. Network security solution is a combination of various security technologies in computer network information system, one that combines safe operating system technology, firewall technology, virus protection technology, intrusion detection technology, and security scanning technology, which forms a complete set of network safety protection system. We must make sure that management and technology, safety technology be integrated with safety measures, and strengthen the computer legislation and enforcement of law, establish backup and recovery mechanism, make corresponding safety standards, and strengthen the network security management measures. Only in this way can we ensure the security of the computer network.REFERENCESThe choosing of a suitable installation place for computer system is very important which directly affect the reliability and safety of the system. When choosing a computer room, we should pay attention to its external environment safety, reliability, avoid strong vibration sources and strong noise source, and avoid high buildings and water in the lower equipment or the next door. The management of the entrance should also be noted[5].3) Computer room safety protectionThe computer room security protection is designed for the physical environment and to prevent disaster from unauthorized individuals or group damage, tampering or theft of network facilities, important data and take security measures and countermeasures. In order to manage regional security, first of all, we should consider the physical access摘要——随着计算机网络技术的快速发展,计算机网络的安全变得越来越重要。

数据通信英语作文Data CommunicationData communication is the exchange of information between two or more devices or systems through various means of transmission. In today's digital age, data communication has become an integral part of our daily lives, enabling seamless connectivity and the exchange of information across vast distances. This essay will explore the significance of data communication, its evolution, and its impact on modern society.At the core of data communication lies the transfer of digital data, which can take various forms such as text, images, audio, or video. The process involves the encoding of information into a format that can be transmitted over a communication channel, such as a telephone line, a computer network, or a wireless medium. The receiving device then decodes the incoming data and presents it in a meaningful way to the user.The origins of data communication can be traced back to the development of early telecommunication technologies, such as the telegraph and the telephone. These early systems paved the way forthe emergence of more sophisticated data communication networks, including the internet and various wireless communication protocols. The advent of the internet, in particular, has revolutionized the way we communicate and access information, enabling the rapid and global exchange of data.One of the primary drivers of data communication is the increasing demand for real-time information and the need for efficient and reliable data transfer. In today's fast-paced, technology-driven world, the ability to transmit and receive data quickly and accurately is crucial for a wide range of applications, from business operations and financial transactions to personal communication and entertainment.The importance of data communication can be seen in various sectors, such as healthcare, where the electronic exchange of medical records and real-time monitoring of patient data can significantly improve patient outcomes. Similarly, in the field of transportation, data communication technologies enable the efficient management of traffic flow, real-time tracking of vehicles, and the coordination of logistics and supply chain operations.The evolution of data communication has also had a profound impact on the way we work and collaborate. The rise of remote work and the need for seamless communication between geographicallydispersed teams have made data communication technologies, such as video conferencing and cloud-based collaboration tools, indispensable. These advancements have not only increased productivity but have also introduced new challenges in ensuring the security and privacy of transmitted data.Another significant aspect of data communication is its role in the growth of the internet of things (IoT) and smart devices. The interconnectivity of various devices, from home appliances to industrial equipment, has enabled the collection and exchange of vast amounts of data, leading to the development of innovative applications and services. This data-driven ecosystem has the potential to transform industries, improve efficiency, and enhance the overall quality of life.However, the increasing reliance on data communication also comes with its own set of challenges. Cybersecurity threats, such as hacking, data breaches, and malware attacks, have become more prevalent, highlighting the need for robust security measures and the continuous development of data protection protocols. Additionally, the sheer volume of data being generated and transmitted has led to concerns about data privacy and the responsible management of personal information.In conclusion, data communication has become a fundamentalaspect of modern life, enabling the seamless exchange of information and driving innovation across various sectors. As technology continues to evolve, the importance of data communication will only grow, presenting both opportunities and challenges. It is crucial for individuals, organizations, and policymakers to address the emerging issues related to data communication and work towards ensuring the secure, efficient, and ethical use of these technologies for the benefit of society as a whole.。

英文文献The Application of one point Multiple Access Spread SpectrumCommunication SystemLiu Jiangang, Nan yang City, Henan Province Electric Power Industry Bureau【ABSTRACT】Spread Spectrum Digital Microwave communication as a communication, because their excellent performance have been widely used. The article in Nan yang City Power Industry Bureau one point Multiple Access Spread Spectrum Communication System as an example. briefed the spread spectrum communications, the basic concept and characteristics of the power system communication applications.KEYWORDS：one point multiple access; Spread-spectrum communication; AttenuationNan yang City in the outskirts of Central cloth 35 to 11 kv substation farm terminals, their operation management rights belong to the Council East, Rural Power Company west (the eastern suburb of agricultural management companies -- four, the western suburbs of Rural Power Company Management 7), Scheduling of the various stations of the means of communication to the original M-150 radio and telephone posts. 2002 With the transformation of rural network, the remote station equipment into operation and communication channels to put a higher demand .As PUC Dispatch Communication Building to the east and west of farmers -- the difference between a company linked to fiber, Therefore, if 11 substations and the establishment of a transfer Link Building links Point may be the data and voice were sent to two rural power companies dispatch room, Rural Network scheduling for the implementation of automation to create the necessary conditions.Given the status and power grid substation level, nature, taking into account the carrier and optical-fiber communications to conduct multiple forwarding, increasing the instability factor, considering the cost and conditions of the urban construction, Finallydecided to adopt wireless spread-spectrum technology to establish that 11 farm terminal substation communication system. This paper describes the spread spectrum technology and the current system of the building.1.The basic concept of spread-spectrum communication.Spread Spectrum Communication's basic characteristics, is used to transmit information to the signal bandwidth (W) is far greater than the practical information required minimum (effective) bandwidth (△ F) , as the ratio of processing gain GP .G P = W/△FAs we all know, the ordinary AM, FM, or pulse code modulation communications, GP values in the area more than 10 times, collectively, the "narrow-band communication", and spread-spectrum communications GP values as high as hundreds or even thousands of times, can be called "broadband communications."Due to the spread-spectrum signal, it is very low power transmitters, transmission space mostly drowned in the noise, it is difficult to intercepted by the other receiver, only spreading codes with the same (or random PN code) receiver, Gain can be dealt with, and dispreading resume the original signal.2.The technology superiority of spread-spectrum communication.Strong anti-interference, bit error rate is low. As noted above, the spread spectrum communication system due to the expansion of the transmitter signal spectrum, the receiver dispreading reduction signal produced spreading gain, thereby greatly enhancing its interference tolerance. Under the spreading gain, or even negative in the signal-to-noise ratio conditions, can also signal from the noise drowned out Extraction, in the current business communications systems, spread spectrum communication is only able to work in a negative signal-to-noise ratio under the conditions of communication.Anti-multi-path interference capability, increase the reliability of the system. Spread-spectrum systems as used in the PN has a good correlation, correlation is very weak. different paths to the transmission signal can easily be separated and may in time and re-alignment phase, formation of several superimposed signal power, thereby improving the system's performance to receive increased reliability of the system.Easy to use the same frequency, improving the wireless spectrum utilization.Wireless spectrum is very valuable, although long-wave microwave have to be exploited, and still can not meet the needs of the community. To this end, countries around the world are designed spectrum management, users can only use the frequency applications, rely on the channel to prevent the division between the channel interference.Due to the use of spread-spectrum communication related receive this high-tech, low signal output power ( "a W, as a general-100 mW), and will work in the channel noise and thermal noise in the background, easy to duplicate in the same area using the same frequency, can now all share the same narrow-band frequency communications resources.Spread spectrum communication is digital communications, particularly for digital voice and data transmission while, spread spectrum communication with their own encryption, only in the same PN code communication between users, is good for hiding and confidential in nature, facilitating communications business . Easy to use spread-spectrum CDMA communications, voice compression and many other new technologies, more applicable to computer networks and digitization of voice, image information transmission.Communication is the most digital circuits, equipment, highly integrated, easy installation, easy maintenance, but also very compact and reliable. The average failure rate no time was very long.We have decided to adopt the spread-spectrum communication technology construction of 11 farm terminal substation communications system, Due to the spread-spectrum communication by the line-of-sight transmission distance restrictions, has become unstoppable system design premise.If the PUC scheduling Building and 11 substations have stopped, and the problem becomes more complicated, use spread spectrum system on the feasibility greatly reduced. Therefore, we look at the city Aerial topographical map, initially identified has not stopped to consider systems design, and requests the companies used this equipment Spread Spectrum 11 points transmission routing of the measured and the results have been satisfactory.Then spread spectrum wireless equipment market supply of cash, initially, weselected a series of Spread Spectrum Comlink third generation products. Because most of the point-to-point mode, Merit functions of the spread-spectrum equipment in a point-to-multipoint application environments encountered many problems: First is the issue of frequency resources. Even a minimum of 64 kbit / s data rate radio, space also occupied bandwidth 5 MHz, Because 32 of the PN code isolation is only about 15 dBm, the project had to use frequency division multiple access 35 db to get around the theoretical isolation. 11 stations will use 11 frequencies, frequency greater waste of resources. Comlink and Spread Spectrum products in the same frequency to achieve a point-to-multipoint communications.Second antenna erection problems, point-to-point equipment for the main radio station, the main station need to set up a number of terminal antennas, the vast majority of domestic engineering companies used by the U.S. Conifer 24 dBi parabolic semi-cast magnesium grid directional antenna. vertical polarization - 1 m wide, it is difficult to top the layout and avoid flap and the mutual interference, Although the project can be set up to take stratified, or through cooperation and on the road to one or more Omni directional antenna launch, However, as construction of a road and the signal attenuation, transmission result is not satisfactory.In addition, the RF cable lying, The application of network management software such factors we have also decided to adopt the final 1:00 Comlink Multiple Access Spread Spectrum products. Its system configuration, as shown in Figure 2:3.Routing AnalysisCombining visual distance access and use the radio and antenna gain, cable attenuation and environmental factors, and testing the design is reasonable, determinethe attenuation affluent channel capacity. Spread spectrum microwave link attenuation depends on the reliability margin.Attenuation margin calculation formula : F G= G SG + G ANT - L GL - L PLF G——Attenuation margin ；G SG——System Gain (dB）；G ANT——Antenna Gain (dBi）；L GL——Connectors and cables attenuation (dB)；L pL—— Channel attenuation (dB）。

关于数字通讯的英语作文The Evolution and Significance of Digital CommunicationIn today's fast-paced world, digital communication has become an integral part of our daily lives. It has revolutionized the way we connect, share information, and conduct business. The advent of digital communication has brought about significant changes, not only in the way we communicate but also in the speed and efficiency of the process.The evolution of digital communication can be traced back to the early days of the internet, when email emerged as a new means of communication. Over the years, digital communication has evolved from simple text-based messages to multimedia-rich platforms like social media, video conferencing, and instant messaging. These advancements have made it possible for people to connect with each other regardless of geographical barriers.One of the most significant benefits of digital communication is its speed. Unlike traditional communication methods like letters or phone calls, digital communication allows information to be transmitted instantaneously. Thismeans that messages, documents, and other forms of data can be shared almost immediately, greatly enhancing productivity and efficiency.Moreover, digital communication has made it easier to access and retrieve information. With the advent of search engines and online databases, users can quickly find and retrieve information from the vast amount of data available on the internet. This has revolutionized the way we research, learn, and make decisions.However, digital communication also has its challenges. The proliferation of misinformation and fake news has become a major concern. It is essential to be vigilant and discerning when consuming information from digital sources.In conclusion, digital communication has transformed the way we connect, share information, and conduct business. Its speed, efficiency, and accessibility have made it an indispensable tool in today's world. However, it is important to be mindful of the challenges that digital communication brings and to use it responsibly.。

通信工程专业英语论文外文翻译(原文)The General Situation of AT89C51The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes of Flash Programmable and Erasable Read Only Memory (PEROM) and 128 bytes RAM. The device is manufactured using Atmel’s high density nonvolatilememory technology and is compatible with the industry standard MCS-51?instruction set and pin out. The chip combines a versatile 8-bit CPU with Flash on a monolithic chip; the Atmel AT89C51 is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications.Features:• Compatible with MCS-51? Products• 4K Bytes of In-System Reprogrammable Flash Memory• Endurance: 1,000 Write/Erase Cycles• Fully Static Operatio n: 0 Hz to 24 MHz• Three-Level Program Memory Lock• 128 x 8-Bit Internal RAM• 32 Programmable I/O Lines• Two 16-Bit Timer/Counters• Six Interrupt Sources• Programmable Serial Channel• Low Power Idle and Power Down ModesThe AT89C51 provides the following standard features: 4K bytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bit timer/counters, a five vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator and clock circuitry. In addition, the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. 1外文翻译(原文)The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port and interrupt system to continue functioning. The Power Down Mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset.Block DiagramPin Description:VCC Supply voltage.GND Ground.Port 0:Port 0 is an 8-bit open drain bidirectional I/O port. As an output port eachpin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high impedance inputs. (Sink/flow) Port 0 may also be configured to be the multiplexed low order address/data bus during accesses to external program and data memory. In this mode P0 has 2外文翻译(原文)internal pull-ups.Port 0 also receives the code bytes during Flash programming, and outputs the code bytes during program verification. External pull-ups are required during program verification.Port 1:Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 1 output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled low will source current (IIL) because of the internal pull-ups.Port 1 also receives the low-order address bytes during Flash programming and verification.Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 2 Port 2:output buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled low will source current (IIL) because of the internal pull-ups.Port 2 emits the high-order address byte during fetches fromexternal program memory and during accesses to external data memory that uses 16-bit addresses (MOVX @ DPTR). In this application it uses strong internal pull-ups when emitting 1s. During accesses to external datamemories that use 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special Function Register.Port 2 also receives the high-order address bits and some control signals during Flash programming and verification.Port 3:Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 3 output buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current (IIL) because of the pull-ups.3外文翻译(原文)Port 3 also serves the functions of various special features of the AT89C51 as listed below:Port 3 also receives some control signals for Flash programming and verification.RST:Reset input. A high on this pin for two machine cycles while the oscillator is running resets the device.ALE/PROG:Address Latch Enable output pulse for latching the low byte of theaddress during accesses to external memory. This pin is also the program pulse input (PROG) during Flash programming.In normal operation ALE is emitted at a constant rate of 1/6 the oscillator frequency, and may be used for external timing or clockingpurposes. Note, however, that one ALE pulse is skipped during each access to external Data Memory.If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in externalexecution mode.PSEN:Program Store Enable is the read strobe to external program memory. When the AT89C51 is executing code from external program memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory.4外文翻译(原文)EA/VPP:External Access Enable. EA must be strapped to GND in orderto enable the device to fetch code from external program memorylocations starting at 0000H up to FFFFH. Note, however, that if lock bit 1(LB1) is programmed, EA will be internally latched (fasten with a latch) on reset.EA should be strapped to VCC for internal program executions.This pin also receives the 12-volt programming enable voltage(VPP) during Flashprogramming, for parts that require 12-volt VPP.XTAL1:Input to the inverting oscillator amplifier and input to the internal clock operating circuit.XTAL2:Output from the inverting oscillator amplifier.Oscillator Characteristics:XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier which can be configured for use as an on-chip oscillator, as shown in Figure 1. Either a quartz crystal or ceramic resonator may be used. To drive the device from an external clock source, XTAL2 should be left unconnected while XTAL1 is driven as shown in Figure 2. There are no requirements on the duty cycle of the external clock signal, since the input to the internal clockingcircuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high and low times specifications must be observed.Idle Mode:In idle mode, the CPU puts itself to sleep while all theon chip peripherals remain active. The mode is invoked by software. The content of the on-chip RAM and all the special functions registersremain unchanged during this mode. The idle mode can be terminated byany enabled interrupt or by a hardware reset.It should be noted that when idle is terminated by a hard ware reset, the device normally resumes program execution, from where it left off,up to two machine cycles before the internal reset algorithm takes control. On-chip hardware inhibits access to internal RAM in this event, but access to the port pins is not inhibited. To eliminate thepossibility of an unexpected write to a port pin when Idle is terminated by reset, the instruction following the one that invokes Idle 5 外文翻译(原文)should not be one that writes to a port pin or to external memory.Power Down ModeIn the power down mode the oscillator is stopped, and theinstruction that invokes power down isthe last instruction executed. The on-chip RAM and Special Function Registers retain their values until the power down mode is terminated. The only exit from power down is a hardware reset. Reset redefines the SFRs but does not change the on-chip RAM. The reset should not be activated before VCC is restored to its normal operating level and must be held active long enough to allow the oscillator to restart and stabilize.Program Memory Lock BitsOn the chip are three lock bits which can be left unprogrammed (U)or can be programmed (P) to obtain the additional features listed in the table below:When lock bit 1 is programmed, the logic level at the EA pin is sampled and latched during reset. If the device is powered up without a reset, the latch initializes to a random value, and holds that value until reset is activated. It is6外文翻译(原文)necessary that the latched value of EA be in agreement with the current logic level at that pin in order for the device to function properly.Programming the Flash:The AT89C51 is normally shipped with the on-chip Flashmemory array in the erased state (that is, contents = FFH) and ready to be programmed. The programming interface accepts either a high-voltage (12-volt) or alow-voltage (VCC) program enable signal. The low voltage programming mode provides a convenient way to program the AT89C51 inside the user’s system, whilethe high-voltage programming mode is compatible with conventional third party Flash or EPROM programmers.The AT89C51 is shipped with either the high-voltage or low-voltage programming mode enabled. The respective top-side marking and device signatureThe AT89C51 code memory array is programmed byte-bybyte in either programming mode. To program any nonblank byte in the on-chip Flash Programmable and Erasable Read Only Memory, the entire memory must be erased using the Chip Erase Mode.Programming Algorithm: Before programming the AT89C51, the address, data and control signals should be set up according to the Flash programming mode table and Figures 3 and 4. To program the AT89C51, take the following steps.1. Input the desired memory location on the address lines.2. Input the appropriate data byte on the data lines.3. Activate the correct combination of control signals.4. Raise EA/VPP to 12V for the high-voltage programming mode.7外文翻译(原文)5. Pulse ALE/PROG once to program a byte in the Flash array or thelock bits. The byte-write cycle is self-timed and typically takes nomore than 1.5 ms. Repeat steps 1 through 5, changing the address anddata for the entire array or until the end of the object file is reached.Data Polling: The AT89C51 features Data Polling to indicate the endof a write cycle. During a write cycle, an attempted read of the lastbyte written will result in the complement of the written datum on PO.7. Once the write cycle has been completed, true data are valid on all outputs, and the next cycle may begin. Data Polling may begin any time after a write cycle has been initiated.Ready/Busy: The progress of byte programming can also be monitoredby the RDY/BSY output signal. P3.4 is pulled low after ALE goes high during programming to indicate BUSY. P3.4 is pulled high again when programming is done to indicate READY.Program Verify: If lock bits LB1 and LB2 have not been programmed,the programmed code data can be read back via the address and data lines for verification. The lock bits cannot be verified directly.Verification of the lock bits is achieved by observing that theirfeatures are enabled.Chip Erase: The entire Flash Programmable and Erasable Read Only Memory array is erased electrically by using the proper combination of control signals and byholding ALE/PROG low for 10 ms. The code array is written with all “1”s. The chiperase operation must be executed before the code memory can be re-programmed.Reading the Signature Bytes: The signature bytes are read by the same procedure asa normal verification of locations 030H, 031H, and 032H, except that P3.6 and P3.7must be pulled to a logic low. The values returned are as follows.(030H) = 1EH indicates manufactured by Atmel(031H) = 51H indicates 89C51(032H) = FFH indicates 12V programming(032H) = 05H indicates 5V programming8外文翻译(原文)Programming InterfaceEvery code byte in the Flash array can be written and the entire array can be erasedby using the appropriate combination of control signals. The write operation cycle isselftimed and once initiated, will automatically time itself to completion.9单片机温度控制系统中英文翻译资料AT89C51的概况AT89C51是美国ATMEL公司生产的低电压，高性能CMOS8位单片机，片内含4Kbytes的快速可擦写的只读程序存储器(PEROM)和128 bytes 的随机存取数据存储器(RAM)，器件采用ATMEL公司的高密度、非易失性存储技术生产，兼容标准MCS-51产品指令系统，片内置通用8位中央处理器(CPU)和flish 存储单元，功能强大AT89C51单片机可为您提供许多高性价比的应用场合，可灵活应用于各种控制领域。