A new multiuser detection scheme for DS-CDMA systems

Direct sequence code division multiple access (DS-CDMA) systems have become a popular choice for use in cellular and personal communications. A new family of multistage low complexity linear receivers for DS-CDMA communications is introduced. The objective of the proposed design is to mitigate the effect of multiple access interference (MAI), the most significant limiting factor of user capacity in the conventional DS-CDMA channel. The receivers presented employ joint detection of multiple users, and therefore require knowledge of all the signature codes and their timing. Each stage of the underlying design recreates the overall modulation, noiseless channel, and demodulation process. The outputs of these stages are then linearly combined. The combining weights can be chosen to implement different linear detectors, including the decorrelating and minimum mean square error (MMSE) detectors. We focus on implementing the MMSE detector. Simulation results illustrate that significant performance gains can be achieved in both synchronous and asynchronous systems