Optimal linear dispersion codes for correlated MIMO channels

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

The design of space-time codes for frequency flat, spatially correlated MIMO fading channels is considered. The focus of the paper is on the class of space-time block codes known as Linear Dispersion (LD) codes, introduced by Hassibi and Hochwald. The LD codes are optimized with respect to the mutual information between the inputs to the space-time encoder and the output of the channel. The use of the mutual information as both a design criterion and a performance measure is justified by allowing soft decisions at the output of the space-time decoder. A spatial Fourier (virtual) representation of the channel is exploited to allow for the analysis of MIMO channels with quite general fading statistics. Conditions, known as Generalized Orthogonality Conditions (GOC), are derived for an LD code to achieve an upper bound on the mutual information, with the understanding that LD codes that achieve the upper bound, if they exist, are optimal. Explicit code constructions and properties of the optimal power allocation schemes are also derived. In particular, it is shown that optimal LD codes correspond to beamforming to a single virtual transmit angle at low SNR, and a necessary and sufficient condition for beamforming to be optimal is provided. Finally, numerical results are provided to illustrate the optimal code design for two examples of sparse scattering environments. The performance of the optimal LD codes for these scattering environments is compared with that of LD codes designed assuming the i.i.d. Rayleigh (rich scattering) model, and it is shown that the optimal LD codes perform significantly better. The optimal LD codes are also compared to beamforming LD codes and it is shown that beamforming is nearly optimal over a range of SNR's of interest.

Original languageEnglish (US)
Title of host publication2006 IEEE Conference on Information Sciences and Systems, CISS 2006 - Proceedings
PublisherInstitute of Electrical and Electronics Engineers Inc.
Pages558-563
Number of pages6
ISBN (Print)1424403502, 9781424403509
DOIs
StatePublished - 2006
Event2006 40th Annual Conference on Information Sciences and Systems, CISS 2006 - Princeton, NJ, United States
Duration: Mar 22 2006Mar 24 2006

Publication series

Name2006 IEEE Conference on Information Sciences and Systems, CISS 2006 - Proceedings

Other

Other2006 40th Annual Conference on Information Sciences and Systems, CISS 2006
Country/TerritoryUnited States
CityPrinceton, NJ
Period3/22/063/24/06

Keywords

  • Beamforming
  • Fading channels
  • Multipleantennas
  • Space-time codes
  • Vitual representation

ASJC Scopus subject areas

  • Computer Science(all)

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