A novel sphere detection algorithm for MQAM MIMO systems

This article derives a new sphere decoding algorithm based on the list sphere decoder(LSD), called improved multistage sphere decoding (IMSD) algorithm. The new algorithm divides the higher-order modulation into several stages of lower-order modulation, uses searching algorithm stage by stage, and defines a new adjustable coefficient r to decrease the effect of the misjudgment of lager weight stages. Besides, we combine the IMSD with the MAP algorithm, and acquire the IMSD-MAP algorithm in allusion to the soft detector of MIMO systems with higher-order modulation. The simulation results show that the IMSD-MAP performs close to the LSD-MAP but has lower complexity.