Chapter 11 - Chapter 11 Typical Wireless Protocols and...

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Chapter 11 Typical Wireless Protocols and Examples
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History of Wireless Technology 1864 Maxwell Predict the existence of radio waves; 1887 H. Hertz demonstrated the existence of radio waves; 1894 The first 150m wireless communications demonstrated by Maxwell and Herts; 1901 Marconi developed an apparatus for transmitting radio wave cross Atlantic Ocean (Dec.12, 901). From Cornwall, England, to Newfoundland, Canada A. S. Popoff of Russia did the similar work in the same time. 1906 R. Ressenden made first radio broadcast of music and voice using AM radio 1921 Detroit Police Department used a 2MHz mobile system for voice communications; 1936 Spread spectrum technique was used for encryption of voice communication; Radar came into use 1946 The first public mobile telephone systems were introduced in five USA cities;
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1947 The first microwave relay system with seven towers connected New York and Boston. 2400 Simultaneous conversations can be supported; 1958 The first satellite communications system setup; 1981 The first analog cellular system, Nordic Mobile Telephone (NMT), was introduced in Scandinavia; 1982 The Advanced Mobile Phones Service (AMPS) was launched in USA; 1988 The first digital cellular phone, Global System for Mobile (GSM), was introduced in Europe; 1994 Bluetooth was proposed by Ericsson; 2004 On 14 December 2004, ZigBee specification ratified. 2006 25 April, we are here to review the history of wireless communications.
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Wireless Link Budget Noise Figure for Cascaded Devices: ) 1 ( 2 1 2 1 3 1 2 1 1 1 1 + + + + = n A A A n A A A cas G G G F G G F G F F F L L Minimum Detectable Signal Strength (Sensitivity): ) ( 3 ) ( ) ( log 10 174 ) ( 10 min 0 dB dB F dB G B dBm dB SNR F BG kT P A A mds + + + + = + = k=Boltzman’s constant (1.374×10 -23 J/K); T=The resistor’s physical temperature (in Kelvin); B=The two-port network’s bandwidth; G A =The power gain of the amplifier; F=The noise figure of the amplifier; SNR min = The minimum signal to noise ratio for detecting the signal.
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Wireless Budget (Cont’d) Calculations of antenna gain for communications G = 4 π d λ P r P G =The antenna gain at Tx and Rx d =The distance between the Tx and RX λ =The wavelength of the operating frequency Pr =The minimum detectable power\ Pt =The transmitting power of the transmitter
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An Example Frequency f 10000 MHz Distance between antennas d 75000 m Transmitted power Pt 1 W Received power Pr 1.00E-13 W Antenna gain G 9.93458827 linear 9.97149873 dB 10 lambda limit d > 0.3 m
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Wireless Budget (Cont’d) Calculations of antenna gain for Radars: 4 1 3 2 max ) 4 ( = r r t t P G G P R π σλ Where, P t is the radiating power, which is set to be 1 W; G t is the transmitting antenna gain, which is set to be 10B; G r is the receiving antenna gain, which is set to be 45dB 10dB; σ is the radar scattering cross section, which is set to be 0.3 m 2 ; P r
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This note was uploaded on 05/01/2011 for the course ELECTRICAL EE5602 taught by Professor Xuequan during the Spring '11 term at City University of Hong Kong.

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Chapter 11 - Chapter 11 Typical Wireless Protocols and...

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