Spectrum Sharing with Distributed Relay Selection and Clustering

TL;DR

This paper introduces a distributed relay selection and clustering method in spectrum-sharing networks, demonstrating that secondary rates grow logarithmically with relay number while interference to primary users diminishes, and proposes an alternating relay protocol to mitigate half-duplex rate loss.

Contribution

It presents a novel distributed relay selection and clustering framework with closed-form rate expressions, showing how to maximize secondary rate and minimize primary interference.

Findings

Secondary rate increases proportionally to log n.

Primary interference can be reduced to zero asymptotically.

Proposed alternating relay protocol improves rate performance.

Abstract

We consider a spectrum-sharing network where n secondary relays are used to increase secondary rate and also mitigate interference on the primary by reducing the required overall secondary emitted power. We propose a distributed relay selection and clustering framework, obtain closed-form expressions for the secondary rate, and show that secondary rate increases proportionally to log n. Remarkably, this is on the same order as the growth rate obtained in the absence of a primary system and its imposed constraints. Our results show that to maximize the rate, the secondary relays must transmit with power proportional to n^(-1) (thus the sum of relay powers is bounded) and also that the secondary source may not operate at its maximum allowable power. The tradeoff between the secondary rate and the interference on the primary is also characterized, showing that the primary interference can be reduced asymptotically to zero as n increases, while still maintaining a secondary rate that grows proportionally to log n. Finally, to address the rate loss due to half-duplex relaying in the secondary, we propose an alternating relay protocol and investigate its performance.