Equalization for 4BOK DS-UWB Systems

Direct-sequence spreading ultra-wideband (DS-UWB) is a strong contender for the standardization of the physical layer of wireless personal area networks (WPANs) by the IEEE 802.15.3a committee. Since long delay spreads in UWB channels cause significant intersymbol interference, equalization is required at the receiver of DS-UWB systems. In this paper, we investigate equalization for DS-UWB with 4-ary bi-orthogonal keying (4BOK), which is one of the two proposed modulation formats. We first derive the corresponding matched-filter bound (MFB), which is the theoretical performance limit. Considering a new equivalent multiple-input multiple-output (MIMO) description of 4BOK DS-UWB, we then devise linear and nonlinear MIMO equalizers. Furthermore, we propose the application of widely linear (WL) processing to these equalizers. Simulation and semi-analytical results show that the proposed MIMO equalizers allow for power-efficient 4BOK DS-UWB transmission close to the theoretical limits with moderate computational complexity.