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II. Modulation & Coding

II. Modulation & Coding. Design Goals of Communication Systems. Maximize transmission bit rate Minimize bit error probability Minimize required transmission power Minimize required system bandwidth Minimize system complexity, computational load & system cost Maximize system utilization.

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II. Modulation & Coding

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  1. II. Modulation & Coding

  2. Design Goals of Communication Systems • Maximize transmission bit rate • Minimize bit error probability • Minimize required transmission power • Minimize required system bandwidth • Minimize system complexity, computational load & system cost • Maximize system utilization

  3. Trades off BER and Energy per Bit Trades off BER and Normalized Rate in b/s/Hz Trades off Normalized Rate in b/s/Hz and Energy per Bit Some Tradeoffs in M-PSK Modulaion 2 1 m=4 m=3 m=1, 2 3

  4. Shannon-Hartley Capacity Theorem System Capacity for communication over of an AWGN Channel is given by: C: System Capacity (bits/s) W: Bandwidth of Communication (Hz) S: Signal Power (Watt) N: Noise Power (Watt)

  5. Shannon-Hartley Capacity Theorem Unattainable Region Practical Systems

  6. Shannon Capacity in terms of Eb/N0 Consider transmission of a symbol over an AWGN channel

  7. Let Shannon Limit

  8. Shannon Limit Shannon Limit=-1.6 dB

  9. Shannon Limit No matter how much/how smart you decrease the rate by using channel coding, it is impossible to achieve communications with very low bit error rate if Eb/N0 falls below -1.6 dB

  10. Shannon Limit Room for improvement by channel coding 16 PSK Uncoded Pb=10-5 8 PSK Uncoded Pb=10-5 QPSK Uncoded Pb = 10-5 Normalized Channel Capacity b/s/Hz BPSK Uncoded Pb = 10-5 Shannon Limit=-1.6 dB Eb/N0 10

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