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dc.contributor.authorChao, CMen_US
dc.contributor.authorTseng, YCen_US
dc.contributor.authorWang, LCen_US
dc.date.accessioned2014-12-08T15:18:49Z-
dc.date.available2014-12-08T15:18:49Z-
dc.date.issued2005-07-01en_US
dc.identifier.issn1536-1276en_US
dc.identifier.urihttp://dx.doi.org/10.1109/TWC.2005.850332en_US
dc.identifier.urihttp://hdl.handle.net/11536/13525-
dc.description.abstractIn the third-generation partnership project technical specification, orthogonal variable spreading factor (OVSF) codes are used as channelization codes. The use of OVSF codes can provide variable data. rates,to flexibly support applications with different bandwidth requirements. Most works in the literature assume that only one single OVSF code is used to support one connection. This may sometimes waste the scarce wireless bandwidth since the allocated bandwidth will increase exponentially as the spreading factor decreases, i.e., a user may be "overserved". In this paper, we consider the possibility of using multiple OVSF codes to support a connection. We show how using multiple codes can reduce the internal and external fragmentations of an OVSF code tree. The tradeoff between bandwidth utilization and hardware complexity of a multicode system is analyzed. The result shows that using two or three codes will be quite cost effective. Several multicode assignment and reassignment strategies, namely, random, leftmost, crowded-first-space, and crowded-first-code, are proposed based on such an environment. Our simulation results show significant increase in code tree utilization and significant reduction in code blocking probability by using the crowded-first-space and crowded-first-code schemes.en_US
dc.language.isoen_USen_US
dc.subjectmobile communicationen_US
dc.subjectOVSFen_US
dc.subjectpersonal communication servicesen_US
dc.subjectthird generation (3G)en_US
dc.subjectWCDMAen_US
dc.subjectwireless communicationen_US
dc.titleReducing internal and external fragmentations of OVSF codes in WCDMA systems with multiple codesen_US
dc.typeArticleen_US
dc.identifier.doi10.1109/TWC.2005.850332en_US
dc.identifier.journalIEEE TRANSACTIONS ON WIRELESS COMMUNICATIONSen_US
dc.citation.volume4en_US
dc.citation.issue4en_US
dc.citation.spage1516en_US
dc.citation.epage1526en_US
dc.contributor.department資訊工程學系zh_TW
dc.contributor.department電信工程研究所zh_TW
dc.contributor.departmentDepartment of Computer Scienceen_US
dc.contributor.departmentInstitute of Communications Engineeringen_US
dc.identifier.wosnumberWOS:000232116500035-
dc.citation.woscount27-
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