| Summary: | 碩士 === 中華大學 === 資訊工程學系碩士班 === 92 === In the 3G services, OVSF-CDMA systems has offered opportunities to provide variable user data rates and flexibly support applications with different bandwidth requirements. Code-Division Multiple-Access (CDMA) techniques allow many users to transmit simultaneously in the same band without substantial interference by using approximately orthogonal spread-spectrum waveforms. The main issue is Code Blocking in OVSF-CDMA systems. It may have significant impact on the bandwidth utilization of the systems. Most papers proposed code assignment and reassignment schemes to resolve the problem, but they were heuristic. Therefore, we propose the Unified Code Management Schemes (UCMS) to resolve code assignment and reassignment problems simultaneously. According to graph theory, we define a new dominating problem and call it the Constrained Independent Dominating Problem (CIDP). We solve the code blocking problem by means of using Constrained Independent Dominating Problem.
This paper presents the Unified Code Management Schemes to eliminate code blocking completely based on CIDP. On the other hand, we also reduce the cost of reassigned codes as far as possible. Finally, simulation results demonstrate that the number of reassignment codes do not significant increase with traffic load rising.
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