What is it about?

For relay terminals in wireless communication systems, the difference of the power consumed for relaying signals means unfairness, which may reduce the network lifetime when the system is energy-constrained. Classic opportunistic relay selections always cause unequal power consumption among all relays. In this study, the authors propose a novel distributed relay selection strategy, named the fair opportunistic relay selection (FORS) strategy, for amplify-and-forward (AF) opportunistic cooperative systems. The FORS strategy is designed based on physical-layer fairness that means all available relays cumulatively consume equal power. They use a set of weight coefficients to adjust the channel fading coefficients effectively and then change the selection probabilities for all relays on the basis of proportional fair scheduling. Considering that the ‘optimal’ relay can be selected proactively in quasi-static Rayleigh fading channels based on local channel state information, the overhead of the proposed scheme is small. Then, they analyse the performance of the FORS strategy and provide an exact analytical expression for the outage probability (Pout) and the average symbol error probability. Numerical simulation results validate their analysis. The results show that the FORS strategy approximately achieves the upper bound of physical-layer fairness in the AF relaying system.

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Why is it important?

Fairness is important for wireless relaying systems, especially when the system is energy-constrained. The classic MAXMIN and the BPS criteria always select the ‘best’ relay for opportunistic relaying to achieve best outage probability performance, while these methods may lead to the result that the relays with good channel quality maybe always selected and the relays with poor channel quality maybe rarely selected. In this case, the system fairness is very bad. Some previous work applied the proportional fair scheduling (PFS) strategy to opportunistic relay selection, but the PFS strategy can only achieve equal probability for all relays to be selected, rather than balance of cumulative power consumption. Additionally, the PFS strategy has a large loss of outage probability performance. This paper proposes a novel distributed relay selection strategy, which can resolve the physical-layer fairness for amplify-and-forward relaying systems.

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A Novel Distributed Relay Selection Strategy Based on Physical-Layer Fairness for Amplify-and-Forward Relaying Systems Haifeng Zhao

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This page is a summary of: Distributed relay selection strategy based on physical-layer fairness for amplify-and-forward relaying systems, IET Communications, November 2016, the Institution of Engineering and Technology (the IET),
DOI: 10.1049/iet-com.2016.0268.
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