Shown here are the BER curves for the various families of M-ary
systems discussed in this chapter. The QAM formats evidently get us closest to the Shannon capacity limit when we are looking for high spectral
efficiency.
Care should be taken when comparing these systems in terms of their bit error probability
as this will depend on whether Gray coding has been
used and how many errors are restricted to adjacent Gray-coded symbols only. Assuming that
only one bit error occurs per symbol, the bit error rate
= symbol error rate / k (where k is the number of bits per symbol).
Further information on the practical design and
performance of multi-level modulation formats is
available on the
Wireless Systems International website.
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