It is difficult for users in multiuser multiple-input multiple-output (MU-MIMO) systems to obtain co-channel interference (CCI) statistics without user cooperation. We propose a technique through which each user can effectively obtain the statistics of the interference that it experiences in a precoded MU-MIMO system. This allows true maximum-likelihood detection to be performed in place of minimum-distance detection. Also, we propose a low-complexity perturbation codebook decoder that attempts to mitigate the effects of both CCI and AWGN. The effectiveness of this decoder in reaching near-optimal performance is shown through Monte Carlo simulations.

A Simulink® model for Direct Sequence Spread Spectrum (DSSS) receiver is presented. Using data-path size as an additional parameter in the model blocks made it possible to do the hardware optimization of the receiver on the block-by-block basis. The effect of the round-off errors to the bit-error rate (BER) of the receiver is quantified for each block in the model. Different functional parts of the receiver, such as analog-to-digital converter (ADC), digital down-converter (DDC), matched filter, are shown to have different sensitivity to the data-path size. Using multivariable optimization, one can use the model to minimize the hardware implementation with respect to the BER.

Zero-forcing beamforming (ZFBF) is a promising technique for multiuser MIMO systems. However, such method requires all the users to feed their channel information back to the base station (BS), so the BS can select the users and receive antennas as well as computing the transmit beamforming matrix. The quality of feedback information is crucial to the resultant system throughput. In order to reduce the power expenditure of the mobile stations (MS) while preserving the feedback quality, we propose a new feedback scheme based on the use of infrastructure relay stations (RS). The simulation results show that the scheme generally gives a better average throughput with lower SNR value requirements.

Space-time trellis codes (STTC) have been proposed as the constituent codes of turbo codes (D Cui et al., 1999) (W Firmanto et al., 2001). In this article, we propose a similar scheme, the iteratively decoded space-time trellis codes (ISTTC), and derive the performance upper bound on BER. When the STTC are combined with space-time block codes (STTC-STBC), it provides an improved BER over the system with STTC only. Here, we also propose the iteratively decoded STTC-STBC (ISTTC-STBC) to improve both the performance and the rate. It can compensate the reduced transmission rate caused from the iteratively decoded STTC to combine the STBC having more transmitters than the constituent STTC. This paper presents the details of computing the extrinsic information shared between two constituent decoders, design schemes of ISTTC with or without STBC, and their performance results shown via simulation.