Cognitive Relay Networks: A Comprehensive Survey

Cognitive radio is an emerging technology to deal with the scarcity and requirement of radio spectrum by dynamically assigning spectrum to unlicensed user. This revolutionary technology shifts the paradigm in the wireless system design by allowing unlicensed user the ability to sense, adapt and share the dynamic spectrum. Cognitive radio technology applied to different networks and applications ranging from wireless to public safety, smart grid, medical, relay and cellular applications to increase the throughput and spectrum efficiency of network. Among these applications, cognitive relay networks is one of the famous application where cognitive radio technology is applied. Cognitive relay network increases the throughput of network by reducing the complete path loss and also by ensuring cooperation among secondary users and cooperation among primary and secondary users. In this paper, our aim is to provide a survey on cognitive relay network. We also provide a detailed review on existing schemes in cognitive relay networks on the basis of relaying protocol, relay cooperation and channel model. Received on 20 June 2015; accepted on 25 June 2015; published on 16 July 2015