Time-domain transmit beamforming for MIMO-OFDM systems with finite rate feedback

  • Authors:

  • Yang-Wen Liang;Robert Schober;Wolfgang Gerstacker

  • Affiliations:

  • Department of Electrical and Computer Engineering, The University of British Columbia, Vancouver, BC, Canada;Department of Electrical and Computer Engineering, The University of British Columbia, Vancouver, BC, Canada;Institute for Mobile Communications, University of Erlangen-Nuremberg, Erlangen, Germany

  • Venue:
  • IEEE Transactions on Communications
  • Year:
  • 2009

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Abstract

Transmit beamforming (BF) and receive combining are simple and popular methods for performance enhancement in multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. In this paper, we propose a novel single-data stream, time-domain BF (TD-BF) scheme for MIMO-OFDM systems which uses cyclic BF filters (CBFFs). Assuming perfect channel state information (CSI) at the transmitter, the C-BFFs are optimized for two different criteria, namely, maximum average mutual information (AMI) per sub-carrier and minimum average uncoded bit error rate (BER). If the C-BFF length Lg is equal to the number of sub-carriers Nc, closed-form solutions to both optimization problems exist. For the practically relevant case Lg Nc we present numerical methods for calculation of the optimum C-BFFs for both criteria. Using a global vector quantization (GVQ) approach the CBFFs are quantized for practical finite-rate feedback channels. Simulation results for typical IEEE 802.11n channels confirm the excellent performance of the proposed scheme and show that TD-BF has a more favorable performance/feedback rate trade-off than previously proposed frequency-domain BF (FDBF) schemes.