Proportional fair scheduling with superposition coding in a cellular cooperative relay system
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Proportional fair scheduling with superposition coding in a cellular cooperative relay system Invited paper Megumi Kaneko · Kazunori Hayashi · Petar Popovski · Hideaki Sakai
Received: 13 April 2012 / Accepted: 10 October 2012 © Institut Mines-T´el´ecom and Springer-Verlag France 2012
Abstract Many works have tackled on the problem of throughput and fairness optimization in cellular cooperative relaying systems. Considering firstly a two-user relay broadcast channel, we design a scheme based on superposition coding (SC) which maximizes the achievable sum-rate under a proportional fairness constraint. Unlike most relaying schemes where users are allocated orthogonally, our scheme serves the two users simultaneously on the same time-frequency resource unit by superposing their messages into three SC layers. The optimal power allocation parameters of each SC layer are derived by analysis. Next, we consider the general multi-user case in a cellular relay system, for which we design resource allocation algorithms based on proportional fair scheduling exploiting the proposed SC-based scheme. Numerical results show that the proposed algorithms allowing simultaneous user allocation outperform conventional schedulers based on orthogonal user allocation, both in terms of throughput and proportional
M. Kaneko () · K. Hayashi · H. Sakai Graduate School of Informatics, Kyoto University, Yoshida Honmachi, Sakyo-ku, Kyoto, 606-8501, Japan e-mail: [email protected] K. Hayashi e-mail: [email protected] H. Sakai e-mail: [email protected] P. Popovski Department of Electronic Systems, Aalborg University, Niels Jernes Vej 12, Aalborg, 9220, Denmark e-mail: [email protected]
fairness. These results indicate promising new directions for the design of future radio resource allocation and scheduling algorithms. Keywords Cellular relay system · Cooperative communication · Superposition coding · Proportional fair scheduling
1 Introduction Intensive research has been devoted to the study of relaying theory and techniques recently, given their large potential for improving the rate and coverage performance of wireless systems [1, 2]. Relays are mainly classified as amplifyand-forward, where the relay forwards the received signal after amplification but without decoding, or decode-andforward (DF), where the signal is decoded and re-encoded at the relay prior to retransmission. Well-known relaying schemes for the relay channel include the multi-hop (MH) transmission, where the destination ignores the signal from the direct link, and the cooperative diversity (CD) transmission, where the direct and relayed signals are combined based on maximum ratio combining (MRC) at the destination. In particular, many works among which [1, 3, 4] have shown the benefits of cooperative diversity where significant diversity gain can be obtained by combining the direct and relayed signals at the end node. Recently, [5] introduced a wireless relaying scheme based on superposition coding (SC) that outperformed conventional CD schemes in terms of ac
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