Cooperative relaying for idle band integration in spectrum sharing systems

The scarcity of radio spectrum caused the emergence of spectrum sharing systems in which unlicensed users can exploit unused licensed primary bands. Due to unavailability of contiguous unused bands, services requiring large bandwidths can not be supported within unlicensed or cognitive networks. This could be overcome by using few disjoint idle bands and generating a larger bandwidth, also known as spectrum aggregation. In this paper, we analyze idle band integration in a cooperative network using multiple relays between a source-destination pair. We propose a simple protocol which allows some relays in the system to assist the source in aggregating a few idle bands through to the destination. As a whole, this enables the source-destination link to utilize a larger integrated bandwidth. We analyze amplify-and-forward (AF) and decode-and-forward (DF) relaying and derive a generalized closed form expression for the outage probability of the system applicable to both scenarios. We also investigate the system performance under different sets of conditions and discover some important tradeoffs.