Reliable link maintenance in cognitive radio systems

Recently, secondary usage of spectrum has been considered in order to better exploit spectral resources and overcome the under-utilization of licensed spectrum. Since the licensed user still keeps primary access rights to its spectrum in such a secondary usage scenario, potential secondary users (SUs) have to vacate the spectrum in case the licensed user claims it. In order to maintain the quality of the secondary communication nevertheless, efficient mechanisms for link maintenance are needed. In this paper we present a general model for link maintenance in secondary usage scenarios. We state that the traditional way of adding redundancy to improve the communication not necessarily works in secondary usage scenarios. Furthermore we present performance results of a link maintenance approach applied to a secondary usage system based on opportunistic spectrum sharing, which verifies our assumptions