| Summary: | 碩士 === 國立清華大學 === 通訊工程研究所 === 92 === For the downlink of third-generation (3G) mobile communication system, the orthogonal variable spreading factor (OVSF) codes are used as channelisation codes to support applications with different bandwidth requirements. Two important issues in the utilization of OVSF codes are code assignment problem and code reassignment problem. Previous studies about these two problems do not consider the phenomenon in actual wireless communication environment, which are path loss variation with distance, slow log-normal shadowing and fast multipath fading. In this thesis, we take path loss and shadowing into account and present a rate transition model. We also propose three new assignment strategies, which are sparse-first, sparse-first and rightmost and modified sparse-first and rightmost. These strategies are compared with those proposed in the previous works under the model which is more realistic.
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