Dete tion for Symmetri Multi - A ess
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List Dete tion for Symmetri Multi-A ess Channels Aaron Reid1, Alex Grant Institute for Tele ommuni ations Resear h University of South Australia Mawson Lakes SA 5095 Australia e-mail: areid spri.levels.unisa.edu.au e-mail: alex.grant unisa.edu.au Paul Alexander Southern Poro Communi ations 6A Nelson Street Annandale NSW 2038 Australia e-mail: palex spri.levels.unisa.edu.au Abstra t | We propose a low omplexity multiuser iterative de oder. We perform the multiuser a-posteriori probability al ulation based on the marginalization of probabilities over a subset of the P highest probable sequen es re eived over a K user symmetri hannel whi h may be approximated losely with per-bit omputational omplexity O(K + P + 2K logK). I. Introdu tion A ode-division multiple-a ess (CDMA) system with hannel oding may be viewed as a seriallyon atenated system and many iterative de oders have been proposed for these systems. The main ontribution of this paper is an algorithm that approximates a-posteriori probability (APP) al ulation with low omplexity for symmetri CDMA hannels (in whi h all the rossorrelations are identi al). This algorithm redu es the omplexity required by nding a list of P sequen es with high aposteriori probability and marginalizing only over this list. Numeri al investigations have shown that typi ally the size of the list required is very small ompared to the total number of sequen es. For the symmetri hannel, we give a polynomial omplexity algorithm for nding su h this list. We additionally show how this idea may be applied to any system for whi h there exists a polynomially omplex optimal dete tion algorithm.
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تاریخ انتشار 2007