Optimal Location of the Secondary Base Station for Broadcasting Cognitive Radio Networks with Spectrum Underlay

This paper focuses on where to place the secondary base station (SBS) so as to obtain the maximum coverage area for a broadcasting cognitive radio network with spectrum underlay. Aiming to solve this problem, the coverage area is first obtained, considering the interference constraints for the primary user (PU) and quality of service constraints for the secondary user. It is found that the location of the SBS takes an important role in the coverage area determination. Then, an optimal location of the SBS is derived to maximize the coverage area in the broadcasting cognitive radio network. Further, considering the local environment can largely determine the characteristics of radio propagation in practice, a typical scenario with an obstacle located between the PU and SBS is analyzed. Numerical results show that the optimal location of the SBS is different with different locations of the obstacle, and will converge to a fixed point as the distance between the PU and the obstacle increases when the obstacle is assumed to be a hill, which is exactly the optimal location of the SBS without the obstacle.