Near-far resistance under multipath: optimum and suboptimum detectors

In a CDMA multiuser communication system, near-far resistance is one of the most important performance measures. The optimum multiuser detector can achieve optimum near-far resistance. Computation of the near-far resistance of the optimum multiuser detector is therefore important since it is the least upper bound on the near-far resistance of any detector, as well as a benchmark for relative performance of any suboptimum detector. In this paper we extend the existing optimum near-far resistance in the asynchronous AWGN and unipath channel case to the asynchronous multipath channel case. We derive the optimum near-far resistance under the assumption of a common identifiability condition in the blind multiuser detection/equalization literature. We also compare the near-far resistance of a subspace method with the calculated optimum near-far resistance.