Design of Multiuser Pre-Rake Systems for Reliable Ultra-Wideband Communications

We consider the design of ultra-wideband (UWB) systems that provide high capacity communication for short-range wireless applications. The design configuration is a multiuser pre-rake UWB broadcast communication system in which the base station is equipped with multiple antennas to achieve high data rates while each user is equipped with a simple and cost-efficient single antenna receiver. We assume the use of multiuser pre-equalization filters at the base station to mitigate the effect of inter-symbol interference (ISI) and multiuser interference (MUI) at the receivers. For the optimization of these filters we develop an analytical framework that minimizes the total transmission power while satisfying (physical layer) users' quality of service for reliable communications. In particular, the quality of service constraints are expressed in terms of the mean square error (MSE) for each user. We show that the design problem is equivalent to a convex optimization problem that can be solved efficiently. The numerical studies confirm that the proposed design strategy for multiuser pre-equalization filters enables the reduction of the total transmission power to achieve a given set of requested MSE targets.