Cross layer optimization for outage minimizing routing in cognitive radio ad hoc networks with primary users' outage protection

Path selection to minimize end-to-end (e2e) outage experience of cognitive users (CUs) in a given communication session is one of the key challenges in multi-hop cognitive radio ad hoc networks, where each CU node experiences a unique spatio-temporal variation of spectrum access opportunity. We study the problem under the constraint of probabilistic interference to primary receivers, in contrast to the popular trend of considering detection probability of primary user (PU) transmissions. This is formulated as a joint transmit power control, spectrum assignment and routing problem and a constrained optimization framework are presented for it. Further, using a standard technique for solving the convex optimization problem, a closed form expression for the transmission power of source as well as relay nodes is derived. Based on this, a centralized solution is proposed for optimal spectrum assignment and route selection. In addition, due to the prohibitive complexity of the optimal solution, a low complexity spectrum aware-outage minimizing opportunistic routing (SA-OMOR) solution is presented, along with its possible distributed implementation. Simulation results are used to validate our analytical results as well as the performance comparison between the proposed SA-OMOR scheme and the optimal one.