National Conference on Synergetic Trends in engineering and Technology (STET-2014)

In a wireless communication system, relaying techniques can offer significant benefits in the throughput enhancement and range extension. On the other hand, cognitive radio is an interesting concept for solving the problem of spectrum availability by reusing the underutilized licensed frequency bands. In a cognitive radio network, relays can be particularly useful for reducing the transmission power at the source and thus reduce the interference to the primary users. In this paper, we study resource allocation problems for cognitive radio networks that employ relays. In this work, the transmission power of the nodes (users and relays) is the resource that we wish to allocate. The power allocation problems are formulated as non-convex non-linear programs and they do not have a structure that could guarantee the quality of the solution. We present a method of transforming the proposed optimization problems to a new formulation so that ε-optimal algorithms can be designed. In general, the transformed problem exhibits certain properties, which enable us to solve the optimization problems to a desirable accuracy by applying known global optimization techniques. We note that the global optimization techniques require significant computations to solve our proposed optimizations. Therefore, we propose low complexity heuristics that provide suboptimal solutions to the given optimization problems. The simulation results show that the performance of the heuristics is close to their respective optimal solutions.