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Du binary signalling


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Du binary signalling

  1. 1. Pulse Generation Generalized form ofcorrelative-levelcoding(partial response signaling)Figure 7.18 EE 541/451 Fall 2006
  2. 2. Duobinary signaling Duobinary signaling (class I partial response) EE 541/451 Fall 2006
  3. 3. Example Duobinary Pulse – p(nTb)=1, n=0,1 – p(nTb)=1, otherwise Interpretation of received signal – 2: 11 – -2: 00 – 0: 01 or 10 depends on the previous transmission EE 541/451 Fall 2006
  4. 4. Duobinary signal and Nyguist Criteria Nyguist second criteria: but twice the bandwidth EE 541/451 Fall 2006
  5. 5. Differential Coding The response of a pulse is spread over more than one signaling interval. The response is partial in any signaling interval. Detection : – Major drawback : error propagation. To avoid error propagation, need deferential coding (precoding). EE 541/451 Fall 2006
  6. 6. Modified duobinary signaling Modified duobinary signaling – In duobinary signaling, H(f) is nonzero at the origin. – We can correct this deficiency by using the class IV partial response. EE 541/451 Fall 2006
  7. 7. Modified duobinary signaling Spectrum EE 541/451 Fall 2006
  8. 8. Modified duobinary signaling Time Sequency: interpretation of receiving 2, 0, and -2? EE 541/451 Fall 2006
  9. 9. Tradeoffs Binary data transmission over a physical baseband channel can be accomplished at a rate close to the Nyquist rate, using realizable filters with gradual cutoff characteristics. Different spectral shapes can be produced, appropriate for the application at hand. However, these desirable characteristics are achieved at a price : – A large SNR is required to yield the same average probability of symbol error in the presence of noise. EE 541/451 Fall 2006