Opportunistic routing based scheme with multi-layer relay sets in cognitive radio networks

Opportunistic routing schemes have their advantages if applied in cognitive radio networks (CRNs), since the reliability is better ensured. However, it is impractical and inefficient to directly use opportunistic routing protocols in CRNs. In this paper, we propose a framework of applying opportunistic routing in CRNs. Our framework builds the multi-layer relay sets for each sender, instead of one general relay set, as seen in other wireless networks. A relay set on one layer refers to the set of nodes that are able to help relay on one channel. Moreover, to select a data transmission channel, each sender considers the channel quality as well as the potential reliability brought by the corresponding relay set. In order to better adjust to the situations when PUs suddenly become active during data transmission, we have each sender maintain one main relay set and one backup relay set. It effectively reduces the channel switching and relay set reselection cost during data transmission. We also give an effective adaptation scheme for each sender when all the relay sets fail. Finally, the simulation results indicate the superior performance of our scheme.