| Summary: | 碩士 === 國立交通大學 === 資訊學院碩士在職專班資訊組 === 99 === The IEEE 802.16j standard is defined to enhance WiMAX networks with relay capacity. Under the transparent mode, existing studies only target at improving network throughput by increasing the transmission rates of mobile stations (MSs). Nevertheless, using a higher transmission rate could harm MSs in term of their energy consumption, especially for those battery-powered devices. In the paper, we consider a bi-objective uplink optimization problem in an 802.16j transparent-relay network to balance between rates and energy costs. In this joint power-and-bandwidth allocation problem, it asks how to arrange the frame space with satisfying MSs’ demands as the first goal and minimizing their total energy consumption as the second goal if the first goal can be met. This bi-objective problem is more meaningful when the network works under a non-saturated condition. We prove this problem to be NPcomplete and develop an energy-efficient heuristic, which has two key designs. First, we exploit relay stations to allow more concurrent uplink communications. Second, when there are remaining resources, we lower down some MSs’ transmission powers by adjusting their transmission rates and paths to save their energy. Simulation results show that our heuristic can save up to 90% of MSs’ energy as compared to existing results.
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