Combined simplified maximum likelihood and sphere decoding algorithm for MIMO system

In this article, a new system model for sphere decoding (SD) algorithm is introduced. For the 2×2 multiple- input multiple-out (MIMO) system, a simplified maximum likelihood (SML) decoding algorithm is proposed based on the new model. The SML algorithm achieves optimal maximum likelihood (ML) performance, and drastically reduces the complexity as compared to the conventional SD algorithm. The improved algorithm is presented by combining the sphere decoding algorithm based on Schnorr-Euchner strategy (SE-SD) with the SML algorithm when the number of transmit antennas exceeds 2. Compared to conventional SD, the proposed algorithm has low complexity especially at low signal to noise ratio (SNR). It is shown by simulation that the proposed algorithm has performance very close to conventional SD.