Joint Downlink Beamforming and Time-Reversed Matched Filtering for Multiuser UWB Signals

This paper proposes a simple delay-line (DL) downlink beamformer for pulsed ultra-wideband (UWB) systems to compensate for propagation delay, which is detrimental to UWB signals. Moreover, we propose a prefiltering-based transmission scheme at the fixed access point (i.e., base station) by shifting the signal processing needs from the receiver at the mobile unit to the transmitter where power and computational resources are plentiful. The DL transmitter array can steer signals to the direction of the desired mobile user such that the desired signals stemming from each antenna are coherently combined and the multiuser interference (MUI) is averaged out. Furthermore, the prefiltering scheme is composed of a set of time-reversed matched filters (TR MFs) subject to multiple-input single-output (MISO) finite impulse response (FIR) channels. A simple correlation receiver is proposed at the mobile unit to extract the information of the time-hopping (TH) UWB signal. The performances under different scenarios are extensively evaluated.