An improved reduced-complexity scheme to accelerate sphere decoding for MIMO systems

Abstract

The sphere decoding (SD) algorithm based on Schnorr-Euchner (S-E) strategy can reduce the complexity for multiple-input multiple-output (MIMO) systems to find the maximum likelihood (ML) solution by updating the search radius whenever a new lattice point was found. In this paper, we propose an improved scheme to reduce the complexity of sphere decoding. In the new method, a factor was introduced for speeding up contraction of sphere radius in each layer of the searching tree. The contraction factor was controlled by signal to noise ratio (SNR) and thus can reduce the complexity especially in low SNR region. Simulation results show that the proposed SD algorithm based on a contraction factor (SD-CF) can efficiently reduce the complexity with negligible performance degradation contrasting to traditional SD.