Adaptive Widely Linear Reduced-Rank Interference Suppression Based on the Multistage Wiener Filter

We propose a widely linear multistage Wiener filter (WL-MSWF) receiver to suppress inter-/intra-symbol interference, multiuser interference, and narrowband interference in a high data rate direct-sequence ultra wideband (DS-UWB) system. The proposed WL receiver fully exploits the second-order statistics of the received signal, yielding a smaller Minimum Mean Square Error (MMSE) than the linear receiver. The WL-MSWF receiver mainly consists of a low-rank transformation and an adaptive reduced-rank after. The rank-reduction is achieved via a transformation matrix. Based on the linear MSWF concept, two constructions of this rank-reduction matrix, namely total WL (TWL) and quasi WL (QWL), are proposed. We develop stochastic gradient (SG) and recursive least squares (RLS) adaptive versions of the proposed TWL/QWL-MSWF and theoretically analyze their convergence behavior. The comparison of the proposed TWL/QWL-MSWF and the existing algorithms is carried out in terms of the computational complexity and the resulting MMSE performance. Extensive simulation results show that the proposed TWL/QWL-MSWF schemes outperform the existing schemes in both convergence and steady-state performance under various conditions.