Low-Complexity Soft-Output Sphere Decoding with Modified Repeated Tree Search Strategy

Many solutions for detecting signals transmitted over flat-faded multiple input multiple output (MIMO) channels have been proposed, e.g., the zero-forcing (ZF), minimum mean squared error (MMSE), sphere decoding (SD) algorithms, to name a few. These approaches however suffer from either unsatisfactory performance or high complexity. In this paper, we focus on the soft-output SD algorithm and propose a modification on the repeated tree search (RTS) strategy. It is shown that our modification can maintain a fixed upper limit in decoding complexity and results in a good performance-complexity tradeoff.