Abstract: With the emergence of cognitive radios, the open spectrum access paradigm that is proposed to overcome the shortcomings of the traditional spectrum allocation paradigm became viable. Researchers have been accumulating efforts to verify the validity of existing networking schemes and protocols as well as designing new ones for this new paradigm. As link failures, due to the activity of primary users, are common in cognitive radio networks, it is essential not to overlook their effect when developing networking solutions including those for multicasting. In this paper, we study the problem of provisioning a multicast session via a tree that has the maximum achievable immunity against any single spectrum failure. The immunity is measured as the minimum percentage of multicast receivers that remain connected with the root of the multicast tree upon the occurrence of a single spectrum failure. The problem is formulated an Integer Linear Program. We also propose a suboptimal algorithm to solve the problem and compare its performance to the optimal performance obtained using the ILP. Results proved the good performance of our algorithm which was always within ≈10% from the optimal solution. Experiments were also conducted to understand how different network parameters affect the achievable immunity.
Keywords: Multicasting, fault tolerance, spectrum failure, Cognitive Radio Networks
