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lecture20 - Lecture Outline(Week 11 lecture 2 Channel...

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Lecture Outline (Week 11, lecture 2) Channel Coding and Link Power Budget Reading: Focus on these notes. If interested, may read text2 section 7.7 1. Error probability and coding gain Consider antipodal signals (BPSK), orthogonal signals (PPM and FSK), and more complicated signals ( M PSK, M PAM, M QAM). Energy per symbol is s E . Energy per bit is M E E s b 2 log = . Variance of noise variance per dimension in 2 0 2 N m = σ SNR (signal to noise ratio) is 0 / N E b in dB Large M reduces energy per bit. However, larger M reduces distance between signal points, which affect error rate dramatically. For M FSK and M PPM, which are orthogonal signals, distance between signal points is not changed by M . However, the bandwidth used is proportional to M. Use error probability plots to engineer required SNR/bit for a tolerable error rate. 1
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Example: What is the required SNR/bit for error rate= 5 10 - if we use: BPSK QPSK 4FSK 16FSK 16PSK 16QAM 2. Error probability and coding gain (Very briefly speaking) What happen if we use an error correction code?
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