# 5.5 Comparison of binary modulation schemes

## Relative BER performance

### Equal average symbol energy

The bit error performance for the major binary modulation schemes is shown here, with the PSK family demonstrating optimum performance as would be expected with antipodal signalling. Coherent FSK with orthogonal signalling is the next best together with coherent ASK, assuming comparison on an average symbol power basis. All of these binary systems exhibit a theoretical maximum bandwidth efficiency of 1 bit/second/Hz. It is interesting to compare these results with the theoretical minimum Es/N0 of only 1 (or 0 dB) required for error-free transmission and 1 bit/s/Hz capacity as given by the Shannon–Hartley capacity theorem. This clearly demonstrates that implicit within the Shannon–Hartley prediction is significant performance improvement over the basic modem design achieved using message data coding techniques. Consequently, Chapter 7 is given over to the discussion of coding for improved digital communications performance. |