Multi-user CDMA detectors for its applications

Abstract

In this thesis, we consider different detectors and compare their performance and complexity when several users are sharing the same frequencies in a synchronous coherent code-division multiple-access (CDMA) system. Practical issues for a possible implementation in ITS applications are considered and modeled. Solutions to the near-far problem and to the degradation of the performance due to an increasing number of users are proposed through various detection algorithms and the introduction of a new multistage detector. Also, less degradation of the performance can be achieved for multipath and fading channels with these new detectors. The choice of spreading sequences, inherent to the spread spectrum CDMA technique, is directly linked to the performance of the receivers and is discussed in detail. Finally, in light of the simulation results, we conclude that some of the CDMA detectors presented in this thesis can possibly be implemented for ITS applications because of their acceptable complexity and overall performance in a multi-user environment.