Performance Evaluation of Asynchronous Direct-sequence CDMA Systems for Satellite Communications

Spread spectrum communication systems provide good features such as low probability of detection and interception (LPD/LPI), robustness against hostile or nonhostile interference as well as multiple-access capability. Direct sequence spread spectrum (DSSS) is by far the most commonly used form of spread spectrum multiple access. In this work, the performance of direct-sequence code-division multiple access (DS-CDMA) systems used for satellite uplink communication is evaluated. In general, the uplink DS-CDMA system is asynchronous due to the differing distances from the satellite to the user terminals. This imposes a unique challenge to the system designer since the multiple access interference needs to be considered. We extend Pursley's SINR analysis to evaluate the DS-CDMA system performance. Three key design parameters have been studied in this analysis: the spreading sequence, the time synchronization impact, and the chip pulse waveform. Our parametric SINR analysis provides a tool for the system designer to optimize the DS-CDMA design parameters to meet the objective SINR performance.