Downlink Performance Analysis of Cognitive Radio based Cellular Relay Networks

In this paper, we propose two operating scenarios of employing cognitive radio to downlink of relay networks. The first scenario uses ISM band while the second scenario exploits opportunity of channel use at UHF spectrum. The capacity gain over conventional relay is investigated in terms of the normalized system capacity. We first statistically model the spectrum usage pattern in those bands and derive the achievable data rate and outage probability in order to analyze performance gain in the view of practical system establishment. Then, we define system capacity by normalizing the effect of bandwidth so that a fair comparison of performance is accomplished. Through our analysis and simulations, it is shown that the proposed scenarios are able to achieve significant gains over a conventional cellular relay system in terms of the normalized system capacity. As a result, relay combined with cognitive radio can be considered as a viable solution to get higher downlink capacity.