Although the existing sphere decoding algorithm of the spatial modulation systems can greatly reduce the computational complexity of the maximum-likelihood (ML) detection
due to its loose updating radii and slow convergence
the level of computational complexity reduction is still very limited
especially in high-order modulation systems. To solve the problem
the statistical distribution is used in this paper to estimate the redundancy in the updating radii of the existing algorithm
and two improved sphere decoding algorithms are proposed. Theoretical analysis and simulation results show that the improved algorithms can greatly reduce the computational complexity of the traditional sphere decoding while achieving the same performance with ML detection
which have great theoretical and practical significance.