Widely linear design of pre-equalization filters for multiuser pre-rake UWB systems

In this paper we consider the widely linear (WL) design of single and multiuser pre-equalization filters (PEFs) for pre-rake ultra-wideband communication systems that transmit binary phase-shift keying (BPSK) modulated data over multipath multiple-input single-output communication channels. The transmitter applies PEFs before spreading and pre-rake filtering while the receiver structure is very simple with a slicer for detection that follows directly after despreading. for this setting, we propose a modified mean square error criterion for PEF design that takes the real-valued signal constellation into account, i.e., a WL design, derive the closed-form optimum solutions for single and multiuser PEFs, and demonstrate the performance gains that are obtained as a result of this WL design approach.