Optimal resource allocation for multiusers FDMA-based cognitive radio with mutual interference threshold

The performance of a cognitive radio (CR) system depends on how to optimally allocate available resources (e.g., bandwidth, subcarrier and power) of a free frequency band without causing any interference to the primary user (PU). We consider a secondary usage of spectrum scenario with the coexistence of primary and secondary users. For such a system, we study the problem of optimizing subcarrier and power allocation with the objective of maximizing sum capacity of CR users such that the received interference at primary users remain below a threshold level as well as mutual interferences between secondary users are guaranteed to be below a satisfied threshold. The CR coordinator needs to determine the position and power which are assigned to each CR user while considering the interference threshold between CR users and from PU to CR users. The proposed scenario is valid in Broadcast, Unicast and Multicast transmission. The effects of adjacent the number of subcarriers for each CR user, which is to reduce mutual interference between CR users and interference between CR and PU, on the proposed scenario have been presented. Numerical studies are performed to compare the performance of CR system with and without considering of mutual interference.