A system and method for detecting Spatially Multiplexed (SM), Space Time Block Coded (STBC), or Hybrid Space Time Block Coded-Spatially Multiplexed (STBC-SM) Multiple-Input Multiple-Output (MIMO) signals is disclosed. QR decomposition of the MIMO signal is performed. A constellation of symbols present in the MIMO signals is partitioned into subsets of symbols, using a set partitioning technique. A-posteriori probability (APP) of each branch is determined. Log Likelihood Ratios (LLRs) corresponding to the transmitted bits are determined using the a-posteriori probabilities. Successively, transmitted bits are determined by providing the LLRs corresponding to the transmitted bits, to a Viterbi decoder.