Code Placement and Replacement Strategies for Wideband CDMA OVSF Code Tree Management
IEEE Transactions on Mobile Computing
MSWIM '03 Proceedings of the 6th ACM international workshop on Modeling analysis and simulation of wireless and mobile systems
A block-based OFDM decode-and-forward relaying scheme for cooperative wireless networks
ISCIT'09 Proceedings of the 9th international conference on Communications and information technologies
Wideband DS-CDMA for next-generation mobile communications systems
IEEE Communications Magazine
UMTS/IMT-2000 based on wideband CDMA
IEEE Communications Magazine
Dynamic assignment of orthogonal variable-spreading-factor codes in W-CDMA
IEEE Journal on Selected Areas in Communications
IEEE Journal on Selected Areas in Communications
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This work focuses on the efficient management of orthogonal-variable-spreading-factor (OVSF) codes for multimedia communications in the W-CDMA systems. Because these systems must assign only OVSF codes that are mutually orthogonal, even if they have sufficient transmission capacity they block connections for which no orthogonal OVSF codes are available. This code blocking can, with extra overhead, be eliminated by reassigning codes, but in this paper we propose an OVSF code management scheme designed to not reassign codes. This scheme, called Region Division Assignment, cannot eliminate code blocking but can reduce the overhead for code assignment. Computer simulations based on the multiple access protocol in UMTS/IMT-2000 show that the proposed scheme can efficiently provide variable-rate services as well as low-rate services.