This paper proposes an efficient beamforming scheme which attains optimality as singular value decomposition (SVD) based systems with low complexity utilizing transmit maximum-ratio combining (TMRC) techniques. The TMRC scheme is the optimum structure for single beamforming systems in terms of received signal-to-noise ratio (SNR) in multiple-input single-output (MISO) channels. In this paper, we generalize the TMRC scheme to multiple beamforming multiple-input multipleoutput (MIMO) systems which support more than one data stream in coded systems. We express each beamforming vector as a linear combination of TMRC vectors whose coefficients are optimized in a successive manner. Optimization of the beamforming vector is followed by the decorrelation process. All TMRC vectors used as a basis of the remaining beamforming vectors are made orthogonal to previously computed beamforming vectors. Exploiting the concept of the gradient ascent algorithm, we propose a simple non-iterative method of computing the precoder which obtains the near optimal performance. Also we derive a closed form expression of the output SNR distribution for the proposed scheme. Simulation results demonstrate that the proposed scheme achieves the almost identical link performance as the SVD-based system for arbitrary configurations with reduced complexity.
Bibliographical noteFunding Information:
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). Digital Object Identifier 10.1109/TCOMM.2009.06.070520
- Closed-loop multiple-input multiple-output (MIMO) systems
- Transmit beamforming
ASJC Scopus subject areas
- Electrical and Electronic Engineering