Double layer sphere decoder and its improvement in multiple-antenna systems

We propose a double layer sphere decoder (DLSD) fur under-determined MIMO systems with fewer receive antennas than transmit antennas. This decoder can reach the Maximum-Likelihood decoding performance with less complxtiy. We further propose an adaptive DLSD that adjusts the initial squared search radius C according to the SNR adaptively. Simulation results show that both DLSDs have far less complexity than the existing GSDs.