Low complexity sphere decoding algorithms

The complex sphere decoding algorithm has optimal bit error ratio performance for uncoded multiple-input multiple-output (MIMO) systems. The computational and hardware complexities of this algorithm increase significantly for detection of 64-QAM modulated signal streams. In this paper two modifications to the original sphere decoding algorithm are proposed that reduce both computational complexity and required hardware resources compared to the original sphere decoding algorithm. The improvements are achieved using a new definition for sphere radius and changing the symbol search strategy. Simulation results show the new algorithms have a small bit error ratio (BER) degradation compare to the original sphere decoding algorithm.