1. A method for determining a bit error rate (BER) for a communication system conveying a full set of signals, the method comprising: (a) selecting signal subsets from the full set of signals based upon one or more characteristics of the signals; (b) determining a BER for the communication system conveying signals of a particular signal subset; (c) repeating (b) for a multiplicity of particular signal subsets; and (d) combining the BERs determined for the particular signal subsets.