Energy-Efficiency-Based Power Allocation Scheme in Multi-user Single-DF-Relay Cognitive Networks
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Energy‑Efficiency‑Based Power Allocation Scheme in Multi‑user Single‑DF‑Relay Cognitive Networks Xianru Liu1 · Wenhao Du1
© Springer Science+Business Media, LLC, part of Springer Nature 2020, corrected publication 2020
Abstract Due to the enhancement in both spectral efficiency and energy efficiency, cognitive radio (CR) being combined with relay cooperation technique is deemed as a promising way to realize green-broadband communication in the fifth generation (5G) networks. In this paper, for such CR-relay networks operating in underlay mode, when multiple secondary cognitive users (SUs) share a common cognitive relay in decode-and-forward manner to complete their physical transmissions, system power consumption is investigated. For the scenarios where the co-channel interference to primary users and the peak transmit power of SUs and cognitive relay are constrained, the problem of power allocation in CR-relay network is formulated to minimizing sum-system-consumption. Then, based on the principle that power-consumption minimization is equivalent to energy-efficiency maximization, a novel power allocation scheme is proposed. Further numerical simulation is used to verify the optimality of the proposed power allocation scheme. Keywords 4G mobile communication · Cooperative systems · Energy consumption · Relays · Cognitive radio
1 Introduction Owing to the ever increasing service demand and physical healthy consideration in wireless application, green-broadband is becoming the ultimate aim to pursuit in communication systems. Consequently, spectral efficiency and energy efficiency are deemed as the most important issues to care in the future 5G wireless networks [1–3]. Among the emerging state-of-the-art techniques, cognitive radio (CR) can be used to enhance spectral efficiency through sharing the same spectrum between primary users (PUs) and secondary user (SUs). On the other hand, the technique of relay cooperation can provide the same level of performance with smaller transmit power or can obtain better performance with the same transmit power, and the energy efficiency of communication systems can be improved. * Xianru Liu [email protected] Wenhao Du [email protected] 1
School of Automation, Central South University, Changsha 410083, China
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Therefore, when the techniques of CR and relay cooperation are integrated effectively, not only larger system capacity but also higher energy efficiency can be achieved at the same time. Consequently, they are introduced into the future small-cell wireless networks, and CR-relay network is viewed as a promising paradigm in the 5G networks [4–6]. In the CR-relay networks with underlay mode, for the PUs whose licensed spectrum is shared by SUs, the transmitted signals from SUs and cognitive relay are co-channel interferences. Hence, the transmit power of SUs and cognitive relay not only affects CR-system capacity, but also determines the co-channel interference to PUs, which inherently determines the spectral efficiency and
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