CSE5345_Lecture6

CSE5345_Lecture6 - Last Class Modulation ASK/PSK/FSK, QAM...

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1 CSE 5345 – Fundamentals of Wireless Networks Yonghe Liu Yonghe@cse.uta.edu 2/2/12 Last Class Modulation ASK/PSK/FSK, QAM Digitization Pulse Code Delta Today Spread Spectrum Spread Spectrum - Transmitter Input is fed into a channel encoder Produces analog signal with narrow bandwidth Signal is further modulated using sequence of digits Spreading code or spreading sequence Pseudonoise, or pseudo-random number Resulting in increased bandwidth of signal
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2 Spread Spectrum - Receiver On receiving end, digit sequence is used to demodulate the spread spectrum signal Signal is fed into a channel decoder to recover data Spread Spectrum Spread Spectrum - Why Resistance to noise and multipath distortion Data hiding and encryption Concurrent transmission for several users Frequency Hoping Spread Spectrum (FHSS) Transmission over seemingly random frequencies A number of channels allocated for the FH signal Width of each channel = bandwidth of input signal Signal hops from frequency to frequency At fixed intervals Transmitter operates in one channel at a time Bits are transmitted using some encoding scheme At each successive interval, a new carrier frequency is selected
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3 Frequency Hoping Spread Spectrum Channel sequence dictated by spreading code Receiver hops in synchronization with transmitter Advantages Eavesdroppers hear only unintelligible blips
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This note was uploaded on 03/22/2012 for the course CSE 5345 taught by Professor Youngheliu during the Spring '12 term at UT Arlington.

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CSE5345_Lecture6 - Last Class Modulation ASK/PSK/FSK, QAM...

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