翻译部分英文原文Coal Face Wireless Sensor Network Physical Layer Design BasedOn UWB TechnologyAbstractIn order to guarantee the safety of coal face production, it is necessary to monitor and surveillance face Shearer, scraper transport planes, hydraulic support, transport machines, broken machines etc . At present, it is difficult for the cable transmission mode to adapt to changes in the work site of the coal face. Transmission lines are often damaged and snapped for various factors, we use wireless sensor network (WSN), which is flexible to be placed and extensible, to resolve this problem. This paper discuss the design of the WSN transceiver for coal face with UWB technology. This kind of transceiver has some useful advantage such as low cost, low power consumption, simple structure, easy to implement the design of the hardware, no need to estimate the coal face Channel characteristics. However, detection efficiency is slightly lower, but the error rate can meet the requirement.1.IntroductionCoal face must face the complicated geological conditions and poor working conditions. In order to ensure the safety of production in the coal face, it is necessary to monitor real-time the face Shearer, scraper transport machine, hydraulic support, reprint machine, broken machines and other large equipments. In addition, we must monitor the ground pressure, gas, carbon monoxide, dust and other environmental parameters. At the same time, mobile voice and image communications is required. At present, the signal monitored and derived from the coal face is transmitted by cable. As the face is moving constantly and the going of the coal mining process, all kinds of large-scale iron and steel equipments in the coal face need to be boosted circularly and continually. The shape of the space is constantly changing with the change of the relative position of the equipments. Correspondingly, communication in cable is difficult to be applicable with the working scene changing, so transmission lines is damaged or snapped frequently ,and the coal face mobile voice and image communication is impossible .All these issues cause many latent trouble to the Safety of theproduction. We think wireless sensor network (WSN) is feasible to implement monitoring and surveillance to the coal face, for it has some useful characters of placing flexibly, expanding simply, moving easily and self-organization.2.WSN architecture in the coal faceThe sensor network system structure of the mining Coal face is shown in Figure 1. In this Figure, the sensor nodes send the information of acquistion through one or more jumps to the cluster node, the base station (sink node) is responsible for the collection of data, and transmit them to task management node through up-slot network, task management Node is responsible for the integrated process the data and also issued instruction to sensor networks. The tunnel of coal face is a limited space. Bracket, shearer, transport and other large metal equipments are layout and coal, rocks and other media is a non-uniform restricted space, which all make the transmission channel more complex, fading and multi-path phenomena more serious in the transmission of wireless sensor nodes signal. These are different from sensor networks on the ground. Therefore,the design of transceiver node of it isparticularly important. At present,there are three main technologies ofthe physical layer in wireless sensornetworks: narrow-band modulationtechnology, spread spectrumtechnology and ultra-wideband(UWB) technology. While UWB technology possesses some attractive advantages such as low power spectrum density, low-complexity system, Low sensitivity to the channel fading, better security and so on. Considering the advantages and the characteristics of coal face naturally, we have adopted Impulse radio ultra-wide band (IR-UWB) technology, and the reasons are followed: 1) UWB technology consumes lower power and has lower power spectrum. Low power consumption, low-cost and small size are the most important feature of wireless sensor network nodes. Narrow-band modulation technology, spread spectrum modulation technology generally use sine carrier , IF and RF circuits exist in the systems, so consuming more power than the UWB technology with no carrier.Transmission medium in the coal face is non-uniform, which leading to more transmission loss than wireless communications systems on the ground. Therefore low power consumption becomes particularly important. In the coal face, as WSN node presents zonal distribution, nodes just need to communicate with neighbor-nodes. The WSN system based on UWB, consuming lower transmission power, can meet the requirements and avoid the interference with each other in the narrow-band communications node. In addition, the low power consumption and high penetrating power help to design safe equipment and transmit disaster relief signal. 2) Strong anti-interference ability. In the coal face, electrical and mechanical equipment has narrow distribution. When equipment starts or stop, electrical sparkle may cause a lot of electromagnetic interference. So good anti-interference capability is strongly required in the wireless communication. 3) Good Anti-interference to multi-path ability. Coal face has some inherent characters, such as narrow space, more types of media, a multi-path intensive channel, while IR-UWB can be applied to this complicated environment with its advantages: narrow Pulse width, small pulse duration ratio, high multi-path resolution, strong anti-multi-path and fading Capacity. 4) Simple structure. The characters of IR-UWB, such as no modulation and up/down conversing frequency, simple transmitter structure, lower power consumption, make it more acceptable. According to the complexity of the node and power consumption into considerations, IR-UWB technology is very applicable to the design of the wireless sensor network physical layer. Therefore, compared to narrow-band modulation technology, spread spectrum technology, the wireless communication system based on the UWB technology present a good performance on the energy consumption, robustness, anti-multi-path and anti-noise, and so on.The modulation of IR-UWB are mainly PAM (OOK), PPM and BPM (Bi-Phase Modulation), but the presence of lines spectrum in PAM and PPM not only make ultra-wideband pulse signal difficult to meet a certain spectrum Requirements, but also reduce the power utilization, thereby it increases energy consumption. Several IR-UWB signals in the frequency spectrum are shown in Figure 2 and Figure 3 . As WSN system requires low power consumption, PAM modulation often use OOK method, which has simple structure. But OOK has poor performance on the BER(Bit Error Rate), anti-noise performance of BPMmodulation such as anti-Jitter noise is better. ISI would be intensified if we adopted PPM under the conditions of intensive multi-path environment in the coal face. Therefore, we use BPM forms in the transceiver system of the coal face.A. The design of transmitting systemThe transmitter which adopts BPM forms is shown in Figure 4. The signal distortion, interference and noise brought by the special environment in coal face need encoded protection through channel coding interweave module. Data rate of the original information is lower, which make it difficult to meet the requirements of FCC in the absence of modulation. We need to use spread spectrum code transform the original information which has a larger duration ratio into a smaller duration ratio (nanosecond). Then we can generate BPM pulse signal through the pulse formation circuit, which can meet the requirement of FCC. Finally use filters to optimize BPM signal further to enlarge the spectrum and send it out from the antenna.The system uses Gaussian pulse to be the form of UWB signal. If a wave transmitted is the first order derivative Rayleigh pulse, the signal after sending out through the antenna is transformed to be the second order derivative of the Gaussian pulse in ideal circumstances. In addition, the lower the order of the Gaussian pulse is, the farther the signal can be sent under the same data rate. Here we select the Gaussian doublet, whose hardware circuit is relatively easy to implement and consume lower energy. Although interference of narrow-band communication system is exist in the ground wireless communications, the higher order of the Gaussian is , the better Gaussian narrow pulse shape. But we do not need to consider interference to the other narrow-band communications in the coal face, for so far, wireless communications systems is basically non-existent in the mine's coal face. A second Gaussian pulse shape can be expressed as:()()222222214t t d t t P e dt παπα-⎛⎫==- ⎪⎝⎭ Here,α is used to express the pulse width, Suppose that the input signal is {}k α , each bit is expressed by i a and its cycle is f T .After the channel encoder, every bit of the sequence {}k α kare repeated by N times. The code durationtime is s T , so each bit is composed by N pulse width. If we suppose thepseudo-random sequence of sensors node k is (){}k j C , the length of thesequence is N, the duration of the code slice is The sequence of (){}k j C can bereplaced by ()()()(){}12,,,,k k k k m N C C C C Λ and the ()1k j C =±.The time coordinate of i-th bit in the frame date stream sent by sensor node k is i t .()f k i s c t =t -i T -j T -τ()()()()()()()()()N *k k k m j s c i =-j =1N k k m j s c i=-j=1St =p t d C δt-iT -jT -τ=d C p t-iT -jT -τ∞∞∞∞∑∑∑∑ 21,m i d a =- when 0,1,i m a d ==-when 1,1i m a d ==.We can thinks f c f T =NT ,T =T in practical application.When N=1, the UWB waves and waveform sent are shown in the Figure 5. Waveform in the Figure from the top to the end is the UWB waveform (the waveform of code “0” and the waveform “1”); the waveform generated whenseveral code are send out; UWB waveform when get through band-pass filter.B. The design of receiver systemThe recerver structure is shown in figure 6. The signal received through the receiving antenna will go through the low noise amplifier and filter. Then the amplitude of the signal will be detected using tunnel diodes peak detector. Then we can get a pulse waveform which own longer code duration time when the signal detected after passing through high-pass filter and pulse stretch circuit. The last step is sample and judge.In this design, we make use of the characters of the negative resistance region of tunnel diode. In this region, the current decreases as the voltage is increased. This negative resistance results in a very fast switching time. After detected by the tunnel and passed through high-pass filter and comparator, the signal can be stretched and delayed by RS latch. We can directly sampling and judge the signal, for the width of the signal we get is wider than we first received .The kind of the receiver is different from the method we previously used. Such as, literature 555 tell the technology about relevant receiver. As we know, the general complexity of the relevant receiver, which own integrator circuit and need precision clock, is much higher. Sometimes, general relevant receiver need matching filter according to channel model parameters, which can be required by channel estimation. Because channel characteristics under the mine well are extremely complex, the possibility to use channel estimation is small. In addition, the receiver does not need ADC conversion devices, for the comparator has fixed the position of the code “0”and”1”.Furthermore, the code stretched has a relative longer duration time, which do not need higher judgment pulse precision. Therefore, in the whole, the receiver does not need complicated channel estimation and ADC conversion devices, which make the energy-consumption and complexity much lower. But we can not ignore the disadvantage of this kindof receiver; it has bigger signal fading, lower detection efficiency.C. Anti-noise performance of BPMThe propagation environment of the coal face belongs to dense multi-path. And the theoretical channel model we referred to is proposed by combining Saleh-Valenzu channel model, which is the foundation, and the characteristic of the coal face under the mine. Suppose the discrete pulse response is()h t, r(t) isir t=s t*h t.the signal received by one node. Then , ()()()iThe distance between receiver and transmitter is about 5-8 meters, which can satisfy the requirement of the distribution of the nodes in the coal face. The code duration time is 25ns, the duration time of GASSION waves is80ps. Under this conditions , we can get the curve, just as shown in the Figure 8.In fact, when we carried out the experiment of BER test, the performance shown in Figure 8 is not easy to be seen because of the complexity of the channel character. According to the research result, the performance of anti-noise became abnormal, such as the fading of the signal is not in proportion to the distance and the amount of the path increase and decrease in a large scale. Because the relevant coefficient of transmitted waves of the BPM is passive relevance when we adopted relevant receiver, the performance of anti-noise ofBPM in relevant receiver is superior to PPM and OOK. Take the structure simplification of the receiver and the special character of the coal face into consideration, BPM is preferable in the whole，ever if the receiver we discussed in this paper is not superior to the relevant receiver on the anti-noise performance.3.ConclusionBecause of the limited space of a non-uniform medium and the complicated channel character in the coal face, the choice of the model we send and receive the signal is extremely important. Taking into account that BPM do not have discrete spectrum when “0” and ”1” emerged in a same probability, if not, the amount of discrete spectrum is small, which is attractive to WSN system, for the low energy consumption is strongly required. Therefore, the communication mode can be used in the coal face. The Gaussian doublet, which can meet the requirement of FCC, is used to send the source signal. Take the complexity of the transmission channels, the receiver use non-coherent receiving method, use tunnel diode to detect signal, execute sampling and judgment after the signal go through the comparator and stretch circuit. This Method does not need channel estimation and ADC circuits, higher pulse sampling accuracy, which together decides the probability to simplify the structure of the receiver greatly. However, the method of receiving has a greater attenuation and bad anti-noise performance than the traditional relevant receiver. But let’s takes every important fac tor into consideration, the receiving method is suitable for the special environment of the coal face.中文译文采煤工作面无线传感器网络物理层设计UWB技术摘要为了保证安全生产的工作面，监测和监视采煤机，刮板运输机，液压支架，运输机械，破碎机等是必要的。
