Combining Sphere Decoding with M-Algorithm

The sequence detection problem for fading channels in multiple-input multiple-output (MIMO) wireless systems is investigated. The sphere decoding (SD) algorithm provides an exact maximum-likelihood (ML) solution, while has expected worst-case complexity which is exponential in the number of symbols jointly detected. On the other hand, the M-algorithm (MA) is a suboptimal solution. Its complexity is linear in the product of the list number and the number of symbols jointly detected. We combined the sphere-constrained search strategy of SD with the M-constrained search principle of the MA. The resulting algorithms can achieve good performance in term of bit error rate (BER) while lower complexity