On transmission techniques for multi-antenna W-CDMA systems

In this paper we present and evaluate a new pre-processing scheme for Multiple Input Multiple Output (MIMO) channels. Its performance is compared with other MIMO schemes proposed for the downlink of Wideband-Code Division Multiple Access (W-CDMA) systems, namely a variation of the Beam Forming (BF), entitled Beam-Selective Transmit Diversity (BSTD) or post-processing schemes, such as the Alamouti-like MTMO or the Vertical Bell Laboratories Layered Space-Time (V-BLAST) MIMO scheme. It is assumed that the Base Station (BS) has M >= 2 transmit antennas and the Mobile Station (MS) receiver has space enough to accommodate N = 2 uncorrelated receive antennas. It is shown that the proposed pre-processing scheme allows receivers with very low complexity, contrarily to the case where a post-processing approach is followed, simplifying the MS receiver. Therefore, the proposed M x N MIMO pre-processing scheme can be seen as an alternative to post-processing schemes. It is also shown that the pre-processing scheme for MIMO channels tends to achieve the best performance in most scenarios, being followed by the BSTD, which allows interference cancellation and provides diversity. Copyright (C) 2007 John Wiley & Sons, Ltd.