Edge-caching assisted underlay spectrum sharing in large-scale cognitive radio networks

Edge-caching and spectrum sharing are promising techniques to meet the fast-growing wireless transmission requirements. In this paper, we propose an edge-caching based underlay spectrum sharing scheme for a large-scale cognitive radio network. In the primary system, primary users (PUs) request files from their associated base stations. In the secondary system, secondary transmitters (STs) intend to communicate with their receivers by sharing the spectrum, and secondary helpers (SHs) actively cache the files of primary system. In the device-to-device (D2D) communication range around each PU, the SH that has cached the file requested by the PU and has the shortest distance to the PU is selected for the cooperative file transfer. With the cooperation from SHs, the transmission quality towards PUs can be greatly improved, and STs can achieve more opportunities for the spectrum sharing. An optimization problem is formulated to maximize the area throughput of secondary system under the performance constraint of primary system. We propose a low-complexity CVX-SA algorithm by decomposing the original problem into two subproblems to jointly determine the file caching policy and system critical parameters. Numerical results show that, compared with the benchmark schemes, our proposed scheme can significantly improve the area throughput of the secondary system.