Abstract
In this paper we derive analytically the optimal set of relays for the maximal destination signal-to-noise ratio (SNR) in a two-hop amplify-and-forward cooperative network with frequency-selective fading channels. Simple rules are derived to determine the optimal relays from all available candidates. Our results show that a node either participates in relaying with full power or does not participate in relaying at all, and that a node is a valid relay if and only if its SNR is higher than the optimal destination SNR. In addition, we develop a simple distributed algorithm for each node to determine whether participating in relaying by comparing its own SNR with the broadcasted destination SNR. This algorithm has extremely low overhead, and is shown to converge to the optimal solution fast and exactly within a finite number of iterations. The extremely high efficiency makes it especially suitable to time-varying mobile networks.
Highlights
Cooperative communication has attracted great attention because it can exploit redundant communication nodes to enhance transmission performance
Our results show that a node either participates in relaying with full power or does not participate in relaying at all, and that a node is a valid relay if and only if its signal-to-noise ratio (SNR) is higher than the optimal destination SNR
We develop a simple distributed algorithm for each node to determine whether participating in relaying by comparing its own SNR with the broadcasted destination SNR
Summary
Cooperative communication has attracted great attention because it can exploit redundant communication nodes to enhance transmission performance. For the issue of implementing relay selection, many existing cooperation schemes are based on centralized optimization algorithms, where all the nodes have to send their information to a central node This may suffer from big overhead, large delay, as well as reliability/security issues, in particular in highly mobile networks [13], or networks with high cost of feedback [16] and synchronization [17]. The optimal relay selection rules developed in [5] and [10] are complex functions involving all the nodes, which mean that all the nodes should share their information through extensive handshaking before relays can be selected This causes severe cooperation overhead and makes the selections not scalable in large networks.
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