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Precoding by Pairing Subchannels to Increase MIMO Capacity With Discrete Input Alphabets

Mohammed, Saif Khan and Viterbo, Emanuele and Hong, Yi and Chockalingam, Ananthanarayanan (2011) Precoding by Pairing Subchannels to Increase MIMO Capacity With Discrete Input Alphabets. In: IEEE Transactions on Information Theory, 57 (7). pp. 4156-4169.

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We consider Gaussian multiple-input multiple-output (MIMO) channels with discrete input alphabets. We propose a non-diagonal precoder based on the X-Codes in 1] to increase the mutual information. The MIMO channel is transformed into a set of parallel subchannels using singular value decomposition (SVD) and X-Codes are then used to pair the subchannels. X-Codes are fully characterized by the pairings and a 2 x 2 real rotation matrix for each pair (parameterized with a single angle). This precoding structure enables us to express the total mutual information as a sum of the mutual information of all the pairs. The problem of finding the optimal precoder with the above structure, which maximizes the total mutual information, is solved by: i) optimizing the rotation angle and the power allocation within each pair and ii) finding the optimal pairing and power allocation among the pairs. It is shown that the mutual information achieved with the proposed pairing scheme is very close to that achieved with the optimal precoder by Cruz et al., and is significantly better than Mercury/waterfilling strategy by Lozano et al. Our approach greatly simplifies both the precoder optimization and the detection complexity, making it suitable for practical applications.

Item Type: Journal Article
Publication: IEEE Transactions on Information Theory
Publisher: IEEE
Additional Information: Copyright 2011 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.
Keywords: Condition number;multiple-input multiple-output (MIMO); mutual information;orthogonal frequency division multiplexing (OFDM);precoding;singular value decomposition (SVD)
Department/Centre: Division of Electrical Sciences > Electrical Communication Engineering
Date Deposited: 18 Jul 2011 09:22
Last Modified: 18 Jul 2011 09:22
URI: http://eprints.iisc.ac.in/id/eprint/39102

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