An improved sphere detection algorithm

In the proposed algorithm,we got a threshold according to the cumulative distribution function.We contrasted the accumulated metric with the threshold when reaching a leaf node,and judge whether the maximum likelihood solution was found,the complexity could be reduced accordingly.The value of the threshold had a certain impact on the performance of the sphere detection algorithm.Thus we needed to make a tradeoff between the performance and the complexity in different SNR range at choosing the threshold.As shown in the simulation result,the expanded nodes converge to m in the high SNR range.