Multistage quasi-orthogonal minimum output energy multiuser detector analysis for turbo coded CDMA systems in frequency-selective fading

The paper presents the performance analysis of the multistage quasi-orthogonal minimum output energy (QOMOE) detector for a turbo coded synchronous CDMA systems in frequency selective fading environment. The QOMOE detector minimizes the output variance with respect to the component equivalent to the quasi-orthogonal component to the desired user´s signature waveform, then the solution is the linear minimum mean square error (LMMSE) transformation. The QOMOE receiver employs maximal-ratio combiner (MRC) for detecting the desired user. A comparison is made among multistage detectors, namely; QOMOE-MRC, matched filter (MF-MRC), decorrelator-MRC, LMMSE-MRC and blind adaptive-MRC receivers, in a frequency selective fading channel. Analysis and simulation results show that the multistage QOMOE-MRC can obtain better performance than that of other considered detectors.