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Equalization with oversampling in multiuser CDMA systems

Vrcelj, Bojan and Vaidyanathan, P. P. (2005) Equalization with oversampling in multiuser CDMA systems. IEEE Transactions on Signal Processing, 53 (5). pp. 1837-1851. ISSN 1053-587X. http://resolver.caltech.edu/CaltechAUTHORS:VRCieeetsp05

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Abstract

Some of the major challenges in the design of new-generation wireless mobile systems are the suppression of multiuser interference (MUI) and inter-symbol interference (ISI) within a single user created by the multipath propagation. Both of these problems were addressed successfully in a recent design of A Mutually Orthogonal Usercode-Receiver (AMOUR) for asynchronous or quasisynchronous code division multiple access (CDMA) systems. AMOUR converts a multiuser CDMA system into parallel single-user systems regardless of the multipath and guarantees ISI mitigation, irrespective of the channel locations. However, the noise amplification at the receiver can be significant in some multipath channels. In this paper, we propose to oversample the received signal as a way of improving the performance of AMOUR systems. We design Fractionally Spaced AMOUR (FSAMOUR) receivers with integral and rational amounts of oversampling and compare their performance with the conventional method. An important point that is often overlooked in the design of zero-forcing channel equalizers is that sometimes, they are not unique. This becomes especially significant in multiuser applications where, as we will show, the nonuniqueness is practically guaranteed. We exploit this flexibility in the design of AMOUR and FSAMOUR receivers and achieve noticeable improvements in performance.


Item Type:Article
Additional Information:“©2005 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.” Manuscript received May 2, 2003; revised May 12, 2004. This work was supported in part by the United States Office of Naval Research under Grant N00014-99-1-1002. The associate editor coordinating the review of this manuscript and approving it for publication was Dr. Joseph Tabrikian.
Subject Keywords:Code division multiaccess; MIMO systems; fractionally spaced equalizers; multiuser channels
Record Number:CaltechAUTHORS:VRCieeetsp05
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:VRCieeetsp05
Alternative URL:http://dx.doi.org/10.1109/TSP.2005.845494
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:332
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:02 Jun 2005
Last Modified:26 Dec 2012 08:39

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