An Novel Initial Radius Scheme of Sphere Decoding in MIMO System

Sphere decoding (SD) is an efficient algorithm which has been proposed in Multiple-input Multiple-output(MIMO) digital communications. Sphere decoding can avoids to search for the element like maximum-likelihood (ML) decoder thus reduces the decoding order of complexity effectively. However, SD also has high complexity in some situations. The complexity of the algorithm are controlled by radius and that plays a critical role in identifying the correct point in the lattice. Thus, it is important to choose a fit initial radius for SD which trade-off the performance and complexity. In this paper, we propose a novel scheme to reduce the initial radius in Golden code decoding though average energy of QAM constellation. The simulation results show when BER is below 10_-4, the proposed scheme can achieve about 0~1 coding gains over Rayleigh fading channels.