Error characteristics of CDMA and impact on voice, e-mail, and Web pages

A code division multiple access (CDMA) wireless network is simulated to analyze errors, determine impact on services and provide an upper bound on the number of active channels. The simulation emphasizes the encoder, decoder/correlator, and a threshold detector; but assumes a resultant Gaussian function for the “air interface” noise. Since the characteristics of a wireless environment vary significantly, we examine, as a whole, the errors on the received signal without accounting for specific error contributions from power, fading, propagation, interference from other users, and other factors in such an environment. The CDMA encoder uses the 64 Walsh codes that are specified in the draft Wideband CDMA Air Interface Compatibility Standard for 1.85 to 1.99 GHz PCS Applications. We use a digitized actual speech database to test for the intelligibility of the voice service over such a CDMA air interface. Therefore, we are able to learn about the nature of the errors inherent in such a frequency spreading technique and also determine an upper bound on the simultaneous active channels that would preserve the quality of service (QOS)