A Tree Pruning Algorithm for MIMO Sphere Decoding Based on Path Metric

Tree pruning can significantly reduce the complexity of sphere decoding (SD). How to determine the pruning rule is an open problem of tree pruning. In this paper, we propose a pruning strategy for SD based on path metric. Because only the nearest lattice point is concerned, if the ratio of the metric to the minimum metric is larger than a threshold, the path whose metric is large enough can be pruned. We analyze the influence of the choice of the thresholds on the performance and the complexity. Through analysis and the simulations, we can show that the complexity reduction is significant while maintaining the negligible performance degradation when proper thresholds are chosen. Besides, tradeoff between complexity and performance can be easily achieved by adjusting the thresholds.