Orthogonalized spatial multiplexing for closed-loop MIMO systems

Heunchul Lee, Seokhwan Park, Inkyu Lee

Research output: Contribution to journalArticlepeer-review

47 Citations (Scopus)


In this paper, we propose a novel spatial multiplexing (SM) scheme for transmission over flat-fading multiple-input multiple-output (MIMO) channels, which allows simple maximum- likelihood decoding at the receiver with small feedback information. We begin with a real-valued representation of the complex-valued system model, and show that we can achieve orthogonality between transmitted signals by applying a proper rotation to transmitted symbols. Compared with other closed-loop methods, the proposed scheme significantly reduces the processing complexity at both transmitter and receiver as well as the feedback overhead. We also combine the proposed orthogonalization method with antenna-selection techniques, and then discuss a criterion based on the minimum Euclidean distance between received vectors for selecting the optimal subset of multiple transmit antennas. Using geometrical properties of the receive constellations, we also present a simple antenna-selection metric for the proposed SM systems. Simulation results demonstrate that our SM system performs close to the optimum closed-loop system with much-reduced complexity.

Original languageEnglish
Pages (from-to)1044-1052
Number of pages9
JournalIEEE Transactions on Communications
Issue number5
Publication statusPublished - 2007 May

Bibliographical note

Funding Information:
Paper approved by D. L. Goeckel, the Editor for Wireless Communications of the IEEE Communications Society. Manuscript received December 26, 2005; revised May 1, 2006. This work was supported in part by the Ministry of Information and Communication (MIC), Korea, under the Information Technology Research Center (ITRC) support program, supervised by the Institute of Information Technology Assessment (IITA), and in part by Basic Research Program of the Korea Science and Engineering Foundation under Grant R01-2006-000-11112-0. This paper was presented in part at the IEEE Vehicular Technology Conference, Montreal, QC, Canada, September 2006.


  • Closed-loop multiple-input multiple-output (MIMO) systems
  • Maximum-likelihood decoding (MLD)
  • Spatial multiplexing (SM)
  • Transmit-antenna selection

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


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