Complexity-reduced multistage detection for MIMO systems using sphere decoding

A complexity-reduced iterative algorithm based on multistage detection and soft sphere decoding (SD) for multiple-input multiple-output (MIMO) systems is presented in this paper. As m-QAM constellation can be decomposed into several QPSK constellations, and it´s very efficient for a soft sphere decoder in QPSK systems. Our scheme combines these together for high order modulation iterative detection and decoding (IDD) systems with remarkable reduced complexity and moderate performance degradation. Performance of our scheme is evaluated by simulation and the performance/ complexity trade-off is explained.