Math @ Duke

Publications [#235919] of Robert Calderbank
Papers Published
 Tan, CW; Calderbank, AR, Multiuser detection of alamouti signals,
IEEE Transactions on Communications, vol. 57 no. 7
(2009),
pp. 20802089, ISSN 00906778 [doi]
(last updated on 2018/05/22)
Abstract: In a MIMO multipleaccess channel where users employ SpaceTime Block Codes (STBC), interference cancellation can be used to suppress cochannel 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 spacetime diversity gain of Alamouti signaling using our proposed lowcomplexity Alamouti BLASTMMSE (ABLAST) 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 STBC's, 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 QuasiOrthogonal STBC (QOSTBC) into multiuser detection of virtual Alamouti users. Building upon our ABLAST Algorithm, we propose new algorithms for decoding singleuser 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. © 2009 IEEE.


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