Sphere Decoding for MIMO OFDM with the Aid of HARQ

In this paper, we proposed a computationally efficient sphere decoding method for MIMO OFDM system with the aid of HARQ. This is a cross layer design scheme which adopt the SNR updating information based on retransmission operation to reduced the search radius of sphere detector, it leads the low complexity of sphere detection. Further more, a modification of sphere decoding is proposed to handle non-rectangular constellations, which is more effective for universal modulation signaling.