Noncoherent detection, adaptive receivers and power control for multiuser communications

The problem of noncoherent detection for nonlinear modulation using multipulse signaling over the Gaussian multiuser Code Division Multiple Access (CDMA) channel is studied. In this work, for the same problem, we first discuss an improved solution by introducing the concept of noncoherent decision feedback, and then study computationally simple stochastic algorithms to adaptively implement noncoherent decorrelation. The sequential decision feedback strategy that we propose enables any user to take advantage of the reduction of uncertainty, resulting from decisions already made for previously decoded users, in the total signal space that its signal lies in. The adaptive noncoherent decorrelator proposed in this work is based on the stochastic approximation (SA) method.; In seeking similar decompositions of known multiuser linear receivers for linear modulation which might lead to improved adaptive implementations, we next consider CDMA based cellular networks and consider coherent communication on the uplink. We introduce a general framework for blind adaptation of the linear Minimum Mean Squared Error (MMSE) multiuser receiver.; In the same cellular network scenario, this work also focuses on a combined power control and multiuser receiver strategy for uplink communication. First we consider the case where the base station in each cell employs linear or decision feedback multiuser receivers which do not change with the user powers. In our work we improve the convergence properties of the conventional stochastic approximation based power control algorithms, once again by using the technique of averaging. Finally, for the problem of minimizing the total transmit power required to achieve SIR QoS objectives, over all linear and decision feedback (DF) multiuser receivers (where the power optimization is done over both feedforward and feedback filter coefficients in the DF case), we present a blind, distributed stochastic algorithm that converges to the jointly optimal pair of power allocations and maximum SIR (MSIR) DF receivers. (Abstract shortened by UMI.)...