IS-95 CDMA and cdma2000: cellular/PCS systems implementations
IS-95 CDMA and cdma2000: cellular/PCS systems implementations
WCDMA for UMTS: Radio Access for Third Generation Mobile Communications
WCDMA for UMTS: Radio Access for Third Generation Mobile Communications
Wireless Communications: Principles and Practice
Wireless Communications: Principles and Practice
Code Placement and Replacement Strategies for Wideband CDMA OVSF Code Tree Management
IEEE Transactions on Mobile Computing
A Mobile Butterfly-Watching Learning System for Supporting Independent Learning
WMTE '04 Proceedings of the 2nd IEEE International Workshop on Wireless and Mobile Technologies in Education (WMTE'04)
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
EURASIP Journal on Wireless Communications and Networking
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Orthogonal variable spreading factor (OVSF) channelization codes are widely used to provide variable data rates for supporting different bandwidth requirements in wideband code division multiple access (WCDMA) systems. Many novel works in the literature have intensively investigated code placement and replacement schemes in OVSF code trees to reduce the code blocking probability and the code reassignment cost. In this paper, we introduce a new code tree structure, namely, a rotated-orthogonal variable spreading factor (ROVSF) code tree, whose code capacity is the same as that of the traditional OVSF code tree. This work addresses both code placement and replacement schemes in the ROVSF code tree system, where ROVSF codes can be used at the forward link of WCDMA systems. Some valuable properties of the developed ROVSF code tree are presented to develop code placement/replacement schemes with lower code blocking probability and less code reassignment cost. The main contribution of our scheme is to identify linear-code chains (LCCs) and nonlinear-code trees (NCTs) in the ROVSF code tree. This work exploits the unsequence property of linear-code chains to design a new code placement and replacement mechanism. Our code placement/replacement schemes initially attempt to allocate request codes on LCCs and, then, to allocate them to NCTs. Using LCCs with the unsequence property allows us to efficiently reduce the code blocking probability and the code reassignment cost. Extensive simulations are conducted to illustrate that our code placement/replacement results based on the ROVSF code tree actually improve the code blocking probability and the code reassignment cost.