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International Journal of Antennas and Propagation
Volume 2014, Article ID 614876, 8 pages
Research Article

Comparison of Semidefinite Relaxation Detectors for High-Order Modulation MIMO Systems

1School of Mechanical & Electric Engineering, Guangzhou University, Guangzhou Higher Education Mega Center, Guangzhou 510006, China
2Department of Electrical & Electronic Engineering, University of Hong Kong, Pokfulam Road, Hong Kong

Received 30 June 2014; Revised 26 October 2014; Accepted 30 October 2014; Published 27 November 2014

Academic Editor: Stefano Selleri

Copyright © 2014 Z. Y. Shao et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Multiple-input multiple-output (MIMO) system is considered to be one of the key technologies of LTE since it achieves requirements of high throughput and spectral efficiency. The semidefinite relaxation (SDR) detection for MIMO systems is an attractive alternative to the optimum maximum likelihood (ML) decoding because it is very computationally efficient. We propose a new SDR detector for 256-QAM MIMO system and compare its performance with two other SDR detectors, namely, BC-SDR detector and VA-SDR detector. The tightness and complexity of these three SDR detectors are analyzed. Both theoretical analysis and simulation results demonstrate that the proposed SDR can provide the best BLER performance among the three detectors, while the BC-SDR detector and the VA-SDR detector provide identical BLER performance. Moreover, the BC-SDR has the lowest computational complexity and the VA-SDR has the highest computational complexity, while the proposed SDR is in between.