Detection strategies for DS-SS systems employing parity bit selected spreading

In this paper, we examine the bit error rate (BER) performance of direct sequence spread spectrum (DS-SS) systems using the parity bit selected spreading technique. Suboptimum detection is done by determining which spreading waveform is most likely used by the transmitter before attempting to detect the data. The bit error rate performance of such a system is dominated by the probability that the receiver incorrectly identifies the correct spreading sequence employed by the transmitter. We investigate the probability that, when the receiver does not correctly identify the correct spreading waveform as that used by the transmitter, it identifies the correct spreading waveform as the second most likely, third most likely etc. Based on these statistics, we propose a new detection algorithm that improves the BER performance by determining the two most likely employed spreading sequences to identify the transmitted information bits. The performance of this new technique is compared to maximum likelihood detection (MLD).