用於Wimax系統之可適性調變和編碼模式的下鏈路分配演算法

Abstract

本論文提出一個針對正交分頻多重存取WiMAX系統之資料叢集分配的演算法，其載波排列為可適性調變和編碼模式，在WiMAX系統中，若妥善分配二維資源(時間和頻率)給不同用戶則能增加整體的傳輸率，因需要描述所在的位置以及連續的時間和連續的通道，在下鏈路中分配用戶的資源有矩形的限制，而此資源分配問題為一個NP-complete問題，為了減少複雜度，本論文提出一個有效率的方法，且與有效率的下鏈路頻寬分配演算法(EDBA)作比較，由模擬結果可知本論文所提出的方法可以達到較高的通道使用率和傳輸率，結果顯示平均的通道使用率為75%~85%而EDBA為60%~70%。

This thesis proposes an efficient downlink resource allocation scheme for Orthogonal Frequency-Division Multiple Access (OFDMA)-based WiMAX systems using the Adaptive Modulation and Coding (AMC) mode operation. Given a set of user requests, the proposed algorithm determines the modulation scheme and allocates a two-dimensional (time and frequency) burst to each user. It is known that finding the optimal solution for such a resource allocation problem is NP-complete. To reduce the computation complexity, this thesis proposes a heuristic solution. When compared with the Efficient Downlink Bandwidth Allocation (EDBA) algorithm,the proposed scheme achieves higher channel utilization and system throughput with a similar execution time. Simulation results show that the average channel utilization of the proposed scheme is approximately75%–85%,while that of EDBA is approximately 60%–70%.