The effect of signal quantization on the performance of DS/SS-CDMA demodulators

The dramatic performance improvements lately experienced by application-specific integrated circuits (ASICs) let us envisage a single-chip all-digital implementation of a data modem for direct-sequence spread spectrum (DS/SS) code-division multiple access (CDMA) systems. In this respect, it is of interest to represent the signals in the digital domain with a small number of bits. On the other hand, it is known that coarse signal quantization may cause a significant bit error rate (BER) performance degradation. This paper investigates on the impact of signal quantization on the BER performance of a DS/SS CDMA receiver in the presence of Gaussian noise and cochannel interference. Based on a general theoretical analysis, a few multiple access strategies are taken into consideration, and some simple design hints are derived and verified by computer simulation.