Simplified local search multiuser detection for QPSK S/MIMO MC-CDMA systems

Promising results obtained for a simplified 1-optimum local search multiuser detection (1-opt s-LS-MUD), are extended in this paper to a new scenario, considering quadrature phase shift keying (QPSK) modulation and single/multiple-input multiple-output (S/MIMO) in a multi-carrier code division multiple access (MC-CDMA) system. Furthermore, so as to avoid the complex-valued computation in QPSK formats, the optimization is reformulated as a real-valued problem (also feasible for high-order modulations). Performance is evaluated considering the bit error rate (BER) criterium in order to assure that the proposed algorithm is efficient in accomplishing a good sub-optimum performance, with a relatively low computational complexity. A detailed computational complexity analysis is taken into account, aspiring future implementations.