Zero-Forcing Based Prefiltering for Multiuser UWB System over Multiple-Input Single-Output Channels

Recently, a lot of attention was paid to UWB IR systems since it is a promising technique for low-complexity low-power short range indoor wireless communications [1-3]. When such transmissions are applied in multiple access system, time-hopping (TH) spreading codes are a plausible choice to separate different users [4-6]. The time-reversal (TR)-based UWB scheme has been extensively investigated recently [7-9]. Attractive features of TR signal processing include: (1) It makes full use of the energy from all the resolvable paths. (2) The TR-based UWB technique shifts the sophisticated channel estimation burden from the mobile receivers to the transmitter at a fixed access point. Most past works of TR UWB scheme focus on the issue of single user transmission and detection, there has been surprising few contributions on the topic of multiuser TR UWB scheme. This paper proposes a prefiltering-based transmission scheme for pulsed UWB system by shifting the signal processing needs from the receiver at the mobile unit to the transmitter at the basestation where power and computational resources are plentiful. We exploit antenna array in the basestation transmitter and take advantage of the spatial and temporal diversities to mitigate the MUI of a TH multiple access UWB communication system. The prefiltering scheme is developed to meet the zero-forcing (ZF) criterion. A simple correlation receiver is proposed at the mobile unit to combine the desired signal stemmed from all the transmitting antennas. The performances under different scenarios are extensively evaluated over multiple-input single-output (MISO) channels. Notation: The boldface letters represent vector and matrix. stand for matrix or vector transpose. We