Joint parameter estimation and detection of DS-CDMA signals in fading channels

In this paper we propose a coherent and a noncoherent receiver structure for asynchronous direct-sequence code-division multiple access (DS-CDMA) communication systems operating over time-varying fading channels. Nontrivial parameters needed for detection, such as propagation delays and fading processes, are estimated, and the receivers therefore require very little side-information. Special attention is given to the near-far problem, and experiments verify that the receivers are near-far resistant. Near-far robustness for synchronization is achieved by using subspace methods and for detection by forming the decision variable as the output of a filter that is designed according to a minimum mean-squared error criterion