Title :
On the performance of orthogonal polyphase sequences in asynchronous CDMA systems
Author :
Alsusa, E. ; ElKalagy, A.
Author_Institution :
MACS Group, Univ. of Manchester, Manchester, UK
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..
Keywords :
channel allocation; code division multiple access; fading channels; interference suppression; mobile radio; multipath channels; orthogonal codes; radiofrequency interference; spread spectrum communication; DCA criteria; DS-CDMA mobile communication system; MAI; OPP sequence code; PN sequence; WH orthogonal code; Walsh-Hadamard orthogonal code; asynchronous transmission; conventional rake-receiver detection; direct sequence code division multiple access system; dynamic code allocation; multipath fading channel condition; multiple access interference minimization; orthogonal polyphase sequence; preraked transmission; pseudorandom sequence; Degradation; Detectors; Direct-sequence code-division multiple access; Downlink; Fading; Maximum likelihood detection; Multiaccess communication; Multiple access interference; Signal to noise ratio; System performance;
Conference_Titel :
Software, Telecommunications & Computer Networks, 2009. SoftCOM 2009. 17th International Conference on
Conference_Location :
Hvar
Print_ISBN :
978-1-4244-4973-6
Electronic_ISBN :
978-953-290-015-6
