Multiuser detection of alamouti signals

• Published in: IEEE transactions on communications Vol. 57; no. 7; pp. 2080 - 2089
• Main Authors: Tan, Chee Wei, Calderbank, A. Robert
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.07.2009; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: adaptive modulation; Alamouti STBC; Algorithms; Applied sciences; BLAST; Block codes; Channels; code diversity; Codes; Coding, codes; Decoding; decorrelator; Detection, estimation, filtering, equalization, prediction; Diversity methods; Exact sciences and technology; Information, signal and communications theory; Interchannel interference; Interference cancellation; Mathematical analysis; Matrices; Matrix decomposition; Matrix methods; maximum likelihood (ML); MIMO; minimum mean squared error (MMSE); Multiplexing; Multiuser detection; quasi-orthogonal STBC; quaternions; Receivers; Signal and communications theory; Signal detection; Signal, noise; Space-time block code (STBC); Switching and signalling; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Transmitters; Wireless networks; Access control; Performance evaluation; Block code; adaptive modulation; Space-time codes; quaternions; Noise reduction; Cochannel interference; quasi-orthogonal STBC; Transmitter; Space-time block code (STBC); code diversity; Spatial multiplexing; Multiuser channels; Mean square error; Alamouti STBC; Algorithm complexity; Signal reconstruction; decorrelator; Signal detection; Multiuser detection; MIMO system; Multiple access; Space diversity; Space time; Signalling; Algorithm; Interference suppression; interference cancellation, BLAST; Signal processing; minimum mean squared error (MMSE), maximum likelihood (ML); Multiple channel
• ISSN: 0090-6778; 1558-0857
• DOI: 10.1109/TCOMM.2009.07.070592

In a MIMO multiple-access channel where users employ Space-Time Block Codes (STBC), interference cancellation can be used to suppress co-channel interference and recover the desired signal of each user at the receiver. Leveraging the special properties of Alamouti matrices, we first show that spatial multiplexing of Alamouti signals retains the space-time diversity gain of Alamouti signaling using our proposed low-complexity Alamouti BLAST-MMSE (A-BLAST) Algorithm. Next, in contrast to traditional transmit diversity that focuses on STBC construction at the transmitter, this paper looks at transmit diversity from the perspective of the receiver. In other words, the receiver gets to choose the STBCiquests, which are favourable to the channel assuming a fixed BLAST receive algorithm. In a multiuserMAC setting, we first present a systematic methodology to exploit different decomposition structure in Alamouti matrices, each with different tradeoff between performance and decoding complexity using possibly different MIMO receive algorithms. We then demonstrate that the notion of angles (the inner product of two quaternionic vectors) between multiuser channels determines the performance of MIMO receive algorithms. As an application of the general theory, we transform the decoding problem for several types of Quasi-Orthogonal STBC (QOSTBC) into multiuser detection of virtual Alamouti users. Building upon our A-BLAST Algorithm, we propose new algorithms for decoding single-user and multiuser QOSTBC. In particular, we show that bit error probability is a function of the quaternionic angle between virtual users (for a single user) or multiple users. This angle varies with the type of QOSTBC and leads to a new form of adaptive modulation called code diversity, where feedback instructs the transmitter how to choose from a plurality of codes.