Imperfect Code Synchronization Effects on Narrowband Interference Rejection in a DS/DPSK Spread Spectrum Receiver

Abstract

The impact of imperfect synchronization on the performance of prediction-error interference rejection filters in noncoherent direct-sequence (DS) spread spectrum communications is considered. Bit error rate (BER) analysis of binary DPSK data modulation used in conjuction with direct-sequence spread spectrum (DSSS) is used as a performance measure. A first order noncoherent delay-lock loop is used for the pseudonoise code tracking. Conditional BER results for the DS/DPSK system for fixed values of the code tracking error are obtained [1]. The average BER of the system is then evaluated by averaging the conditional BER expressions over the probability density function of the code tracking error. Results include the effects of both a single fading tone and narrowband gaussian interferer on the overall system performance.