Dynamic code sharing algorithms for ip quality of service in wideband cdma third-generation wireless networks
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
Efficient OVSF Codes Assignment Strategy and Management Architecture in Wideband CDMA
BROADNETS '04 Proceedings of the First International Conference on Broadband Networks
Efficient OVSF Code Assignment and Reassignment Strategies in UMTS
IEEE Transactions on Mobile Computing
EURASIP Journal on Wireless Communications and Networking
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Orthogonal variable spreading factor (OVSF) codes are employed as channelization codes in wideband CDMA. Any two OVSF codes are orthogonal if and only if one of them is not a parent code of the other. Therefore, when an OVSF code is assigned, it blocks all of its ancestor and descendant codes from assignment because they are not orthogonal to each other. Unfortunately, this code-blocking problem of OVSF codes can cause a substantial spectral efficiency loss of up to 25%. This paper presents non-blocking OVSF (NOVSF) codes to increase substantially the utilization of channelization codes without having the overhead of code reassignments. In addition, an encoding algorithm is presented to increase network capacity and support higher data rates when NOVSF codes are employed.