无线通信系统第1章

Course Introduction
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Wireless Communications Principles 32 class hours in all Examination paper is in English
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About the textbook
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Features of Wireless Communications
• Information is transmitted by radio waves Radio channel is not a good transmission channel: – Large path loss, – Multipath, – Time-variant ( Signal Fading) • In complex interference environment Interferences from – Space (cosmic, atmosphere phenomenon) – Industry equipment – Other electronic and communication systems – Themselves
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The proposal of cellular concept
•The disadvantage of a single transmitter on a central •The big breakthrough came when AT&T Labs researchers divided wireless communications into a series of cells
2Mbps in a vehicular environment,,20Mbps in a pedestrian environment Wide Area, high velocity：100Mbps ： Indoor, lower velocity：1Gbps ： Capacity: 5-10 times higher than 3G
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Chapter I
Introduction to Wireless Communication Systems
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At a glance of the history
1894-96 First Transmitter – First Patent 1897 World’s First Wireless Telegraph & Signal Company 1901 Telegraph across the atlantic ocean 1899-1912 Saving Lives 1920 Discovery of short wave(<100m)
3G evolution …but difficult
–to extend to higher data rate with CDMA only technology; –to provide various services with different QoS –to have enough frequency resource to accommodate more subscribers
1974-1978:First field trial for cellular system
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Current Wireless Systems
Cellular Systems Satellite Systems Wireless LAN Wireless MAN Wireless PAN
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Syllabus
1. Introduction to Wireless Communication Systems 2. The Cellular Concept: System Design Fundamentals 3. Mobile Radio Propagation: Large-Scale Path Loss 4. Mobile Radio Propagation: Small-Scale Fading and Multipath 5. Multiple Access Techniques for Wireless Communications 6. Wireless Networking
AMPS US TACS UK
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2nd generation of mobile technology
•Digital cellular systems •Supporting high bit rate voice, limited data communication •Improved quality Include standards
Guglielmo Marconi
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Titanic
"Those who had been saved, had been saved through one man, Mr. Marconi... and his marvellous invention"
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History of wireless communication
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Features of Wireless Communications
Limited radio spectrum, but the demand is increasing Increasing User number, increasing services demand call for: Increasing spectrum efficiency of systems Reasonable spectrum allocation Variety of Networks, complex network management Mobility management (switching, roaming) Security management (Registration, authentication, accounting etc.) Mobile stations are suitable for use in moving Small in size, light in weight, saving power, low cost, reliable
What is wireless communication
Any form of communication that does not require the transmitter and receiver to be in physical contact
Electromagnetic wave propagated through freespace Radar,RF,Microwave,IR,Optical
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WPAN
802.15.1Bluetooth
Cable replacement RF technology (low cost) Short range (10m, extendable to 100m) 2.4 GHz band (crowded) 1 Data (700 Kbps) and 3 voice channels Widely supported by telecommunications, PC, and consumer electronics companies
GSM Europe(By far the dominant one) IS-95 US
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3G
Offers enhancements to current applications including greater data speeds, increased capacity for voice and data and a broader range of services CDMA2000 WCDMA TD_SCDMA Highest data rate(3G)
1920’s: Radio broadcasting became popular 1928:many TV broadcast trials 1930’s:TV broadcasting development 1950’s: Communications satellites launched 1960’s:Bell Labs developed cellular concept Late 1970’s:technology cellular telephone advances enable affordable
–at least 144 Kb/s in a vehicular environment, –384 Kb/s in a pedestrian environment, –2048 Kb/s in an indoor office environment.
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Beyond 3G
BASE STATION
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First generation of mobile technology
•Analog cellular systems(FM) •Only carry voice traffic •Less secure and prone to interference when signal is weak Include standards