| Summary: | 碩士 === 國立臺灣海洋大學 === 資訊工程學系 === 94 === Abstract
OVSF (Orthogonal Variable Spreading Factor) codes are used as channelization codes in WCDMA system. OVSF codes are getting popular due to his efficiency and flexibility to allocate variable bite rates for different bandwidth requirement of applications. A core design issue of OVSF code allocation schemes is to deal with code assignment efficiently and to reduce the code reassignment overhead. In literal, there are different OVSF code-allocation schemes have been proposed and evaluated. In this paper, we provide an alternate OVSF code allocation scheme for single and dedicate code allocation in WCDMA systems. The code allocation scheme has two parts: rate allocation and code assignment. First, we decide the rate for each active connection according to user profiles of the connection and available data size in incoming data buffer for the connection. Second, we assign OVSF code for each active connection according to the results of the rate allocation in the first phase. We compared our propose scheme with the other two popular schemes: left-first and crowded-first. Results showed that the proposed scheme outperforms the other two schemes, regarding data throughput and delay.
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