On the performance of orthogonal polyphase sequences in asynchronous CDMA systems

Authors:
E. AlSusa;A. ElKalagy
Affiliations:
School of Electrical & Electronics Engineering, University of Manchester, Manchester, UK;School of Electrical & Electronics Engineering, University of Manchester, Manchester, UK
Venue:
SoftCOM'09 Proceedings of the 17th international conference on Software, Telecommunications and Computer Networks
Year:
2009

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Abstract

In this paper we study the performance of orthogonal poly-phase (OPP) sequences on the uplink of asynchronous code division multiple access (CDMA) systems. We explore the application of dynamic code allocation (DCA) of OPP sequences with the objective to minimize multiple access interference (MAI), arising due to the asynchronous transmission, and enhance the system's overall performance. Two DCA criteria are analyzed and compared. Finally, for the sake of completeness, the performance of OPP codes with and without DCA is compared to that of Walsh-Hadamard (WH) orthogonal codes and complex pseudorandom (PN) sequences for the cases of conventional rake-receiver detection as well as pre-raked transmission. It will be shown that OPP codes can provide superior performance, especially with pre-rake transmission, to both WH and PN sequences even under sever asynchronous and multipath fading conditions..