A Novel Initial Radius Selection with Simplify Sphere Decoding Algorithm in MIMO System

Sphere decoding (SD) is an efficient algorithm which has been proposed in Multiple-input Multiple-output(MIMO) digital communications. Sphere decoding has been shown to achieve near-ML performance with low complexity which can avoid searching for the element. However, SD also has high complexity in some situations. The complexity of the algorithm is controlled by radius. Thus, it is important to choose a fit initial radius for SD which trade-off the performance and complexity. Chen-Lee sphere decoding algorithm can increase the size of the search region. In this paper, we propose a novel scheme to reduce the initial radius in Alamouti code decoding though combined with Chen-Lee sphere decoding algorithm and the average energy of qQAM constellation. The simulation results show when BER is below 10-4, the proposed scheme can achieve about 0 similar to 1 coding gains over Rayleigh fading channels.