Stanford Technology Ventures Program
In recent years, soft iterative decoding techniques have been shown to greatly improve the bit error rate performance of various communication systems. For multi-antenna systems employing space-time codes, however, it is not clear what is the best way to obtain the soft information required of the iterative scheme with low complexity. In this paper, the authors propose a modification of the Fincke-Pohst (sphere decoding) algorithm to estimate the maximum a posteriori probability of the received symbol sequence. The new algorithm solves a nonlinear integer least-squares problem and, over a wide range of rates and signal-to-noise ratios, has polynomial-time complexity.