Performance of direct-sequence systems with long pseudonoise sequences

A performance analysis of direct-sequence systems with long pseudonoise sequences is presented. The assessment of the symbol error probability in the presence of multiple-access interference is stressed, but other types of interference are also considered for completeness. Both binary and quaternary spreading waveforms are treated. The analysis, which uses a nonstandard Gaussian approximation, makes transparent the answers to a number of technical issues. Approximate error probabilities that are relatively simple computationally are derived. The approximations are accurate to within at least one decibel and, more typically, a few tenths of a decibel