| Summary: | 碩士 === 國立清華大學 === 資訊工程學系 === 101 === Recently, Orthogonal Frequency Division Multiple Access (OFDMA) transmission technique is gaining popularity because of its higher transmission capacity. The IEEE 802.16 standard has also adopted the OFDMA as its access technique. The problem of resources allocation in time and frequency is the bottleneck of OFDMA system. Due to the base station has to choose a group of bursts to transfer and decide the using of radio resource, modulation and coding rates by the bursts, it will generate a lot of unnecessary waste when the allocation of radio resource is bad. We show that the resources allocation problem is NP-hard. Therefore, we proposed an approximation downlink bandwidth resource allocation scheme which is called AOBA to improve the downlink bandwidth utilization in this thesis. AOBA allocates every sub-channel one by one to prevent generating wastage. In the resources allocation, we adopted dynamic programming strategy to reduce the wastage which may occur in the allocation process. The simulation results show that compared AOBA with the optimal allocation which is calculated by brute force with branch and bound algorithm, our method is not only having good bandwidth utilization and stability, but also has a lot of superiority in execution time.
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