Cognitive routing with the ETX metric

The emergence of cognitive radio network technology provides network nodes with abundant licensed and unlicensed channels to select for routing. Traditional routing methods that minimize hop count often do not leverage the full capabilities of cognitive radio users. They may select high lossy links or choose arbitrarily among the different paths of the same minimum length, regardless of the often large differences in throughput among those paths. In this paper, we propose a routing algorithm that incorporates the expected transmission count metric (ETX) to select high-quality channels for routing on a hop-by-hop basis. The ETX metric incorporates the effects of link loss ratios, and interference among the successive links of a path, as well as interference caused by licensed users' activity. Our routing algorithm utilizes all the available channels and selects channels with the best ETX value, allowing us to find paths with higher stability and higher throughput. Simulation in the NS-3 environment shows that our routing protocol has high packet delivery ratio, low end-to-end delay and low hop count in the presence of interference caused by licensed users.