Browsing by Author "Liu, Jui-Hsiang"

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Efficient Resource Allocation for Energy Conservation in Uplink Transmissions of IEEE 802.16j Transparent Relay Networks
(2010)
Liang, Jia-Ming
;
Wang, You-Chiun
;
Chen, Jen-Jee
;
Liu, Jui-Hsiang
;
Tseng, Yu-Chee
By introducing the relay capability, the IEEE 802.16j standard is developed to improve the WiMAX performance. Under the transparent mode, existing studies aim at improving network throughput by increasing the transmission rates of mobile stations (MSs). However, we show that using higher rates will let MSs consume more energy. In the paper, we define an energy-conserved uplink resource allocation (EURA) problem in 802.16j networks under the transparent mode, which asks how to arrange the uplink resource to 1) satisfy MSs' requests and 2) minimize their energy consumption. Objective 1 is necessary while objective 2 should be achieved when objective 1 is met. The above bi-objective problem is especially important when the network is non-saturated. The EURA problem is NP-hard and we propose a heuristic with two key designs. First, we exploit relay stations to allow more concurrent uplink transmissions to fully use the frame space. Second, we reduce MSs' transmission powers by adjusting their rates and paths. Simulation results show that our heuristic can save up to 80% of MSs' energy as compared with existing work.
Energy-efficient uplink resource allocation for IEEE 802.16j transparent-relay networks
(2011-11-10)
Liang, Jia-Ming
;
Wang, You-Chiun
;
Chen, Jen-Jee
;
Liu, Jui-Hsiang
;
Tseng, Yu-Chee
The IEEE 802.16j standard is defined to enhance WiMAX networks with relay capacity. Under the transparent mode, existing studies only target improving network throughput by increasing the transmission rates of mobile stations (MSs) and maximizing concurrent transmissions. However, using a higher transmission rate or allowing more concurrent transmissions could harm MSs in terms of their energy consumption, especially when they are battery-powered. In this paper, we consider the energy-conserved resource allocation problem in the uplink direction of an IEEE 802.16j network under the transparent mode. This problem asks how to arrange the frame usage with satisfying MSs' demands as the constraint and minimizing their total energy consumption as the objective. We prove this problem to be NP-complete and develop two energy-efficient heuristics, called demand-first allocation (DFA) and energy-first allocation (EFA) schemes. These heuristics employ a gradient-like search method to approximate the optimal solution. Specifically, DFA tries to satisfy MSs' demands first by using as less frame space as possible. Then, with the remaining frame space. DFA tries to save MSs' energy by lowering their transmission rates or adjusting their transmission paths. Viewed from a different perspective. EFA first allocates the frame space to MSs to consume the least energy. Since the total allocation may exceed the frame space. EFA then exploits spatial reuse and rate adjustment to pack all demands into one frame. simulation results show that our heuristics can approximate the ideal performance bounds and save up to 90% of MSs' energy as compared to existing results. (C) 2011 Elsevier B.V. All rights reserved.