الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Primary user activity is a major bottleneck for existing routing protocols in cognitive radio networks. In the scope of cognitive radio networks, typical routing protocols avoid areas that are highly congested with primary users, leaving only a small fragment of available links for secondary route construction. In addition, wireless links are prone to channel impairments such as multipath fading; which renders the quality of the available links highly uctuating. In this work, we investigate using cooperative communication mechanisms to reveal new routing opportunities, enhance route qualities, and enable true coexistence of primary and secondary networks. As a result, we propose Undercover: a cooperative routing protocol that utilizes the available location information to assist in the routing process. Speci cally, our protocol revisits a fundamental assumption taken by the state of the art routing protocols designed for cognitive radio networks. In Undercover, we integrate cooperative communication techniques into the route discovery process where secondary users can transmit in the regions of primary users activity through nulling out transmission at primary receivers via beamforming. In addition, the secondary links qualities are enhanced using cooperative diversity. To account for the excessive levels of interference typically incurred due to cooperative transmissions, we allow our protocol to be interference-aware. Thus, cooperative transmissions are penalized in accordance to the amount of negatively aected secondary ows. We evaluate the performance of our proposed protocol via NS2 simulations which show that the main protocol idea can enhance the network goodput by a ratio reaches up to 250% compared to other popular cognitive routing protocols with minimal added overhead. Then, we propose CSCR, a channel selection scheme for cooperation-based routing protocols in cognitive radio networks. The proposed scheme increases the spectrum utilization through integrating the channels selection in the route discovery phase of Undercover. The best channels, that are less congested with primary users and that lead to minimum switching overhead, are chosen while constructing the cooperative group. Evaluating CSCR via NS2 simulations shows the advantage of choosing wisely the working channel. Undercover, with CRCS added over it, outperforms its counterparts in terms of good put, end-to-end delay, and packet delivery ratio. The proposed scheme can enhance the network good put, in some cases, by more than 150%, as compared to other related protocols.