Multiuser Receivers for Future CDMA Mobile Radio Systems

Download or read book Multiuser Receivers for Future CDMA Mobile Radio Systems written by Homoud M. I. Alkussayer and published by . This book was released on 1997 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis a group of simplified multiuser receivers for a CDMA system are presented and evaluated. The problem of multiuser detection in a synchronous channel is considered where a class of new simplified sub-optimum bear multiuser detectors are suggested, for both the decorrelating and the MMSE detectors. It is shown that by using Gold code as the spreading sequence the complexity of the two new multiuser detectors is independent of the number of users. For an asynchronous CDMA system a one-shot linear decorrelating detector is investigated. A novel improved one-shot detector which outperforms Verdu's one-shot detector with much reduced complexity is proposed. A second new detector using non-orthogonal matching which reduces the complexity even further, with small reduction in performance, is also suggested. A third is the matched filter slicing detector which is a more simplified detector for a special system. For the same channel, a novel CDMA system using dual-signalling with multiuser detection is presented. Using a replicated spreading sequence at the transmitters and halved correlation period plus linear combining at the central station, a one-shot detection is achieved. Two decorrelating algorithms, the direct method and the recursive method, are presented. Theoretical and simulation results showed that this scheme significantly outperforms the conventional detector and its performance approaches that of the single user. Finally, the multiuser detection in a frequency non-selective Rayleigh fading channel is studied. Two novel detectors are proposed.The first uses dual-signalling without interleaving, which results in a greatly simplified near-far resistant detector. The second uses dual-signalling with interleaving which results in a slightly more complex detector. The performance of both detectors is however superior to the conventional detector, and they can outperform the original LDD detector which is far too complex.