| Multiple transmit and receive antennas can increase the system capacity, as well as increase reliability in wireless communication. Vertical Bell Laboratories layered spaces-time (V-BLAST) scheme is widely used to achieve high spectral efficiencies in scattering environments. In V-BLAST systems, receiver design is usually based on the nulling-canceling algorithm which offers a good tradeoff between the computational complexity and system performance.;In this thesis, we propose a nulling-canceling based detection algorithm that performs selective maximum-likelihood decoding. We first compare the symbol estimates from two nulling-canceling implementations with different orders. If the symbol estimates do not agree, then maximum-likelihood detection is performed on the discrepant symbols and the rest of the symbols are detected via nulling and canceling. If there is no discrepancy in the comparison, then only nulling and canceling are performed. In our numerical results, 4-QAM (Quadrature Amplitude Modulation) and 16-QAM constellations are considered, and both Minimum Mean Squared Error (MMSE) and Zero-Forcing (ZF) based detections are implemented. We show that our proposed algorithm can achieve a better performance than the nulling-canceling algorithm and requires a relatively small increase in computational complexity, especially at high SNR.;Based on the Bit Error Rate (BER) performance result, we show that our proposed algorithm can achieve a better performance than the nulling-canceling algorithm and requires a relatively small computational complexity increase, especially at high Signal-to-Noise Ratio (SNR) scenario. The BER performances of an unordered system with BPSK (Binary Phase Shift Keying) or 4-QAM modulation and hybrid detection algorithms are given, under the joint consideration of nulling-canceling of several subchannels and block maximum-likelihood detection of several subchannels. |
