A Very Low Complexity QRD-M Algorithm Based on Limited Tree Search for MIMO Systems

The authors present a very low complexity QRD-M algorithm for MIMO systems. The original QRD-M algorithm decomposes the MIMO channel matrix into upper triangular matrix and applies a limited tree search. To accomplish near-MLD (Maximum Likelihood Detection) performance for QRD-M algorithm, number of search points at each layer must be the modulation size. In the proposed scheme, each of survival branches are extended only to the corresponding QR Decomposition (QRD)-based detection symbol in the next layer and its neighboring symbols in the constellation. Using this approach, they can significantly decrease the complexity of conventional QRD-M algorithm. Simulation results show that the proposed algorithm scheme achieves the detection performance near to that of the MLD with negligibly low complexity.