A novel method for initial radius selection of sphere decoding

Sphere decoding is an effective method for the maximum-likelihood (ML) detection for multiple-input multiple-output (MIMO) systems, but its initial radius selection is still a problem. This paper proposes a novel method for this selection and thus solves the problem. In this method, by making use of the MMSE solution of the received signal, a proper initial radius can be obtained, by which the sphere decoder achieves not only the no-failure decoding but also a low computational complexity. The analysis shows that this proposed initial radius is the statistically shortest one for no-failure sphere decoding. Simulation results indicate that the proposed initial radius achieves both the no-failure decoding of the sphere decoder and a lower computational complexity.