Performance of the Space-Time Block Coded DS-CDMA Uplink Employing Soft-Output ACO-Aided Multiuser Space-Time Detection and Iterative Decoding

In this treatise we propose a three-stage twin-transmit-antenna assisted Multiuser (MU) Direct Sequence Code-Division Multiple Access (DS-CDMA) system employing both a Unitary Rate Code (URC) and a Recursive Systematic Code (RSC) to carry out iterative turbo detection. A Space-Time Block Code (STBC) is used to provide second-order diversity gain in conjunction with a novel soft-output (SO) ant-colony-optimization (ACO) based space-time multiuser detection (ST/MUD) algorithm, which is capable of carrying out STBC decoding, while mitigating the Multiuser Interference (MUI) and generating the Log-Likelihood Ratios (LLR) for facilitating the iterative exchange of extrinsic information between the URC and RSC decoders of each user. With aid of the above mentioned state-of-the-art techniques, the proposed system becomes capable of approaching the performance of the single-user system within about 0.5dB, when K = 32 users are supported with the aid of 31-chip Gold-codes.