MDP routing for multi-rate loss networks
Computer Networks: The International Journal of Computer and Telecommunications Networking
Code Placement and Replacement Strategies for Wideband CDMA OVSF Code Tree Management
IEEE Transactions on Mobile Computing
Information Sciences—Informatics and Computer Science: An International Journal
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
Efficient integration OVSF code management strategies in UMTS
Computer Communications
MDP-based CAC for two-dimension spreading VSF-OFCDM in 4G cellular communications
GLOBECOM'09 Proceedings of the 28th IEEE conference on Global telecommunications
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For the reason of the orthogonal characteristic of the Orthogonal Variable Spreading Factor (OVSF) code tree in Wideband CDMA (WCDMA) systems, code blocking increases as traffic load (i.e. Erlang load) or the required rate increases. This causes inefficient utilization of channelization codes. Hence, how to efficiently manage the resource of channelization codes of the OVSF code tree in WCDMA systems is an important issue and has been studied extensively. There are two aspects to achieve efficiency including code assignment and code reassignment. In the aspect of code assignment, an efficient code assignment scheme reduces code blocking probability significantly. In the aspect of code reassignment, code reassignment results in several drawbacks, such as large overhead of computation, high complexity of codes moving, and long call setup time for a new request call, etc. Therefore, in this paper we focus on the first aspect of how to efficiently assign the channelization codes. Additionally, most researches did not consider the analysis of tree state with dynamic traffic load and their analysis lack of systematic call admission control (CAC) mechanism. Therefore, in this paper, we first propose the Markov decision process (MDP) based analysis to assign channelization codes efficiently. Next, we extend the MDP-based approach as the call admission control mechanism to maximize the system revenue while reducing blocking probability. Furthermore, a bit string masking algorithm is proposed to reduce the time complexity of tree managing and searching for available channelization codes. Numerical results indicate that the proposed MDP approach yields the best fractional reward loss, code blocking reward loss, and code blocking ratio as compared to that of other schemes, including the random, left most, and crowded first schemes.