Outage Capacity Analysis of a Cooperative Relaying Scheme in Interference Limited Cognitive Radio Networks

In this study, we investigate the outage capacity of a cooperative relaying based cognitive radio network in slow fading channel. Our network scenario consists of a primary transmitter (PT) and primary receiver (PR) as well as a group of \(M\) secondary transmitter (ST)–receiver (SR) pairs. We grouped STs into active and inactive. Only one active ST may transmit data at a time in parallel with the PT satisfying a predefined interference threshold \(I_{th}\) to the PR. Due to fading/shadowing or interference caused by ST to the PR, primary user (PU) may fail to achieve its target rate \(R_{{\textit{PT}}}\) over a direct link. To overcome this, we can boost up primary capacity by using inactive STs as cooperative relay (Re) nodes for the PU. In addition, one of the inactive STs that achieves \(R_{{\textit{PT}}}\) will be act as a best decode-and-forward relay to forward the primary information. In this paper, a closed-form expression of the outage capacity is derived. Results show that outage capacity improves with increasing cooperative nodes as well as when the active ST is located farther away from the PR.