SNR-dependent radius control sphere detection for MIMO systems and relay networks

A new sphere decoder algorithm for uncoded spatial multiplexing multiple-input multiple-output (MIMO) systems is proposed. It overcomes the drawbacks of traditional sphere decoders: variable complexity and high complexity in low signal-to-noise ratios (SNRs). Its main novelty lies in scaling the search radius by a heuristic SNR-dependent factor. This new SNR-dependent radius control sphere decoder offers near maximum likelihood performance over the entire range of SNRs, while keeping its complexity roughly constant. This algorithm also incorporates channel ordering to save complexity. To quantify the variability of complexity, the normalised variance of the complexity is evaluated. This algorithm is also extended for joint iterative detection and decoding in coded MIMO systems and for MIMO-relay networks. Simulation results and theoretical analysis demonstrate the benefits of the proposed algorithm. Copyright © 2013 John Wiley & Sons, Ltd. *Correspondence C. Tellambura, Department of Electrical and Computer Engineering, University Alberta, Edmonton, AB, Canada T6G 2V4. E-mail: [email protected] This paper was presented in part at the IEEE International Conference on Communications (ICC), June 2011, Kyoto, Japan. Received 31 July 2012; Revised 31 December 2012; Accepted 6 January 2013