Optimally near-far resistant multiuser detection in differentially coherent synchronous channels

The noncoherent demodulation of differentially phase-shift keyed signals transmitted simultaneously via a synchronous code-division multiple-access (CDMA) channel is studied under the assumption of white Gaussian background noise. A class of noncoherent linear detectors is defined with the objective of obtaining the optimal one. The performance criterion considered is near-far resistance that denotes worst-case multiuser asymptotic efficiency over near-far environments. It is shown that the optimal linear detector is a noncoherent decorrelating detector. The commonality between the properties of the decorrelating detectors for coherent and noncoherent channels is established. In particular, it is shown that no other differential phase-shift keying (DPSK), multiuser detector achieves a higher near-far resistance than does the noncoherent decorrelator