| Summary: | 碩士 === 國立中央大學 === 通訊工程研究所 === 95 === In the OFDMA system, the channel condition shall be considered as the basic requirement of resource allocation for the provisioning of QoS services. In addition, the size of MAP, resulting from the increase of the number of traffic bursts, shall also be well considered to reduce its overhead so that the valuable bandwidth of wireless can be effectively utilized. It was illustrated in the reference [2] that the MAP overhead of OFDMA system will exhaust 20%-60% bandwidth of down link and it also pointed out that this is a critical problem of bandwidth utilization in OFDMA system. As this issue has not been well discussed before, a noval traffic burst allocation algorithm, which considers the channel quality, coding and modulation, is proposed in this thesis to reduce the influence of the extra bandwidth burden in MAP.
The proposed burst mapping algorithm considers not only the bandwidth requirements of Subscriber Stations (SS) and applicable channel modulation, but also the time complexity. And, in order to map the traffic bursts in rectangle blocks more effectively, the concept of “Target Site” with flexible boundary adaptation is applied. Besides, if a traffic burst can not be fit into a rectangle block, an appropriate degradation of the coding and modulation level is derived by considering the optimal throughput. The simulation results show that, under the QoS constraints, our algorithm can effectively improve the extra bandwidth burden caused in OFDMA system. When Comparing to the existing normal mapping algorithm, the simulation result shows that our algorithm can improve about 16.5% of the system performance.
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