System design for DS/SSMA communications with random spreading sequences and a matched filter receiver

The problem of selecting the processing gain and the chip waveform of a band-limited, direct-sequence spread-spectrum multiple-access communication system with aperiodic random spreading sequences and conventional matched filter receiver is considered when given the system bandwidth and the symbol transmission rate. The average probability of bit error is used as the objective function of the optimization. The signals are constrained to be strictly band-limited and to produce zero interchip interference. With a technique to characterize a band-limited chip waveform with a finite number of parameters, a sufficient condition for a system to have lower average probability of bit error is found. Some design strategies are derived that are based on the sufficient condition. Design examples are also provided using analytical methods and Monte-Carlo simulations.