| Summary: | 碩士 === 國立臺灣大學 === 電信工程學研究所 === 99 === In the thesis, we investigate a distortion-optimized resource allocation scheme for downlink video transmission over multiuser Orthogonal Frequency-Division Multiple Access (OFDMA) networks. Video distortion in wireless networks is mostly caused by rate-controlled source coding and transmission errors due to packet losses. Both distortions are results from the selection of modulation and coding schemes (MCSs), each providing different throughput and reliability levels. Therefore, it is important to select appropriate MCS to determine the optimal resource allocation among users. To proceed, we formulate the resource allocation problem as a distortion minimization problem by joint consideration of sub-channel assignment and MCS selection, subject to the constraints of limited system resources. To solve the formulated problem, MCS for each user on each sub-channel is first determined that induces the least distortion. We then apply the Hungarian algorithm to optimally assign the subchannels for users with their channel conditions accordingly. As a result, the proposed algorithm distributes the remnant sub-channels sequentially to the user with the most reduction in distortion. During the process of remnant sub-channels allocation, the MCS selected initially may become unsuitable and is dynamically switched to a more appropriate one to meet the designated distortion threshold. Simulation results show that with at most 1.3% increase in the computational cost, the proposed algorithm achieves performance gain by 3%-13% in general and 16%-55% for users with SNRs which a better solution is obtained by joint consideration, compared to the resource allocation scheme without joint consideration of MCS.
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