Optimization of primary exclusive region in spatial grid-based spectrum database using stochastic Geometry

In database-driven spectrum sharing for 5G mobile networks, a primary user (PU) may experience harmful interference caused by unpredictable propagation paths, even when secondary users (SUs) follow a spectrum sharing policy established on the basis of a database. A framework for determining the optimal radius of a circular primary exclusive region (PER) on the basis of SU's information has been proposed. However, a practical PER can be complex-shaped and should be designed on the basis of the directivity of the PU antenna, and the SU information in each region. In this paper, we present a stochastic geometry analysis in a spatial grid-based spectrum database, and propose a design for an optimal complex-shaped PER. The database determines the transmission probability of the SUs on each divided annular sector. By regarding the SU's locations on each annular sector as an inhomogeneous Poisson point process, we analytically derive a PU's outage probability (OP), where the PU's OP is defined as the probability that the aggregate interference power at a PU from the SUs exceeds a threshold. Using the derived expression, we formulate an optimization problem to maximize the number of transmitting SUs, which optimizes the SU's transmission probability on each annular sector. Then, we numerically evaluate the solution of the optimization problem in various scenarios. The results show that the accuracy of the PER improves as the grid size decreases. In addition, we successfully design a complex-shaped PER with holes in which the SUs are permitted to transmit.