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Cayley differential unitary space-time codes

Hassibi, Babak and Hochwald, Bertrand M. (2002) Cayley differential unitary space-time codes. IEEE Transactions on Information Theory, 48 (6). pp. 1485-1503. ISSN 0018–9448. doi:10.1109/TIT.2002.1003836.

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One method for communicating with multiple antennas is to encode the transmitted data differentially using unitary matrices at the transmitter, and to decode differentially without knowing the channel coefficients at the receiver. Since channel knowledge is not required at the receiver, differential schemes are ideal for use on wireless links where channel tracking is undesirable or infeasible, either because of rapid changes in the channel characteristics or because of limited system resources. Although this basic principle is well understood, it is not known how to generate good-performing constellations of unitary matrices, for any number of transmit and receive antennas and for any rate. This is especially true at high rates where the constellations must be rapidly encoded and decoded. We propose a class of Cayley codes that works with any number of antennas, and has efficient encoding and decoding at any rate. The codes are named for their use of the Cayley transform, which maps the highly nonlinear Stiefel manifold of unitary matrices to the linear space of skew-Hermitian matrices. This transformation leads to a simple linear constellation structure in the Cayley transform domain and to an information-theoretic design criterion based on emulating a Cauchy random matrix. Moreover, the resulting Cayley codes allowpolynomial-time near-maximum-likelihood (ML) decoding based on either successive nulling/canceling or sphere decoding. Simulations show that the Cayley codes allow efficient and effective high-rate data transmission in multiantenna communication systems without knowing the channel.

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Additional Information:“©2002 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.” Manuscript received April 27, 2001; revised September 5, 2001. Communicated by S. Shamai, Guest Editor. The authors would like to thank M. Oussama Damen for providing them with a preprint of [36], J. Mazo for helping them prove Theorem 4, and a reviewer for the suggestion that led to the first example in Section III.
Subject Keywords:Bell Labs layered space–time (BLAST), Cauchy random matrices, Cayley transforms, differential modulation, fading channels, receive diversity, transmit diversity, unitary space–time codes, wireless communications
Issue or Number:6
Record Number:CaltechAUTHORS:HASieeetit02c
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1036
Deposited By: Archive Administrator
Deposited On:02 Dec 2005
Last Modified:08 Nov 2021 19:06

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