Achieving maximum bit rate in a cognitive radio network with physical layer network coding

In this paper, the power allocation problem in a relay‐assisted cognitive radio network (CRN) is considered where the secondary users exchange information in an interweave mode on the basis of physical layer network coding. In order to enhance the capacity of CRN, using multiple‐input multiple‐output and orthogonal frequency division multiplexing has become very popular in the literature. This paper goes one step further to improve the throughput of secondary users using physical layer network coding by drawing off the transmission time. The main goal is to maximize the capacity of CRN, while keeping the total interference imposed on the primary users under a certain threshold. An optimal solution to this power allocation problem with limited relay power constraint, due to the limited budget, is derived; however, because of the high complexity of this method, an efficient suboptimal solution is also proposed.