QoS provisioning in energy-efficient cooperative networks with power assignment and relay deployment planning
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QoS provisioning in energy-efficient cooperative networks with power assignment and relay deployment planning Jane-Hwa Huang1
•
Sz-Yan Hsu2
Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The cooperative network is an energy-efficient technology to provide ubiquitous broadband access and quality-of-service (QoS). This paper investigates the tradeoffs among QoS, capacity, and power consumption in the cooperative networks. By adaptively selecting among the direct, relay, and cooperative transmission (TX) modes for users, we can enhance the capacity with lower transmission power. Furthermore, we determine the proper relay location and transmission powers of base station (BS) and relay station, so that more users can exploit the low-power two-hop TX modes to enhance the capacity and reduce the delay. In the real networks, if the packet queue is empty, the BS can be idle without sending (to save energy). Hence, we also properly increase the link capacity and idle probability to further reduce power consumption. We develop an analytical model to evaluate the delay, variance, capacity, idle probability, and actual power consumption in unsaturated traffic conditions. Then, we apply an optimization approach to analytically determine the optimal relay location and transmission powers, aiming to maximize the overall energy efficiency (EE) subject to the delay requirements. Numerical results show that the adaptive TX-mode selection scheme along with the joint power assignment and relay deployment planning can significantly enhance the capacity and reduce the power consumption. Then, the goal of QoS support can be achieved with higher EE. Keywords Quality-of-service (QoS) Energy efficiency (EE) Transmission-mode adaptation Relay deployment planning Power assignment Optimization design
1 Introduction The cooperative network is an economical solution to enable green wireless networks for a variety of applications [1–5]. Figure 1 illustrates a cooperative network. Without wireline connections, the low-complexity relay stations (RSs) can be rapidly deployed with low costs. Thanks to shorter communication distances, the cooperative networks can extend reliable high-data-rate coverage with low transmission power. Moreover, the mobile station (MS) can & Jane-Hwa Huang [email protected] Sz-Yan Hsu [email protected] 1
Department of Electrical Engineering, National Chi-Nan University, Puli Township, Nantou County 545, Taiwan, ROC
2
MediaTek Inc., Hsinchu 300, Taiwan, ROC
select the direct, relay, or cooperative transmission (TX) mode to communicate with the base station (BS) with higher capacity. However, saving energy and improving quality-of-service (QoS) are usually contradictory goals. Specifically, using two-hop TX modes can reduce power consumption. Nevertheless, the capacity and QoS may be degraded (e.g., longer delay), because of the longer two-phase transmission time. Hence, selecting the proper TX mode is an essential issue. The
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