A complex sphere decoder for space-time codes

ln this paper, we present a new sphere decoder for space-time block code (STBC) decoding. Because the decoder is based on complex sphere decoding, it can be applied to STBC decoding of any modulation constellation. In the decoder, we give a method for obtaining an initial decoding solution and the initial sphere radius from the initial decoding solution, the obtained initial radius is relatively small. During the process of decoding, we define a metric for sorting all elements in the candidate symbol set of each component and the elements are searched in the sequence, which speeds up the shrinkage of the sphere and reduces the decoding average computational complexity. Simulation results verify the efficiency of the decoder.