Energy allocation optimization for cooperative cognitive network

In this paper, a cognitive radio scenario is proposed, where secondary users are allowed to communicate concurrently with primary users provided that they do not create harmful interference to the licensed users. Here, we aim to improve the unlicensed system performance under power and interfernce constraints. For this aim, we propose to use a cooperative relay to assist the secondary transmission. Moreover, an adaptive modulation is used in order to compensate the throughput loss due to the relaying. The main contribution of this work is to consider a new energy allocation scheme for source and relay nodes to maximize the instantaneous received signal-to-noise ratio under the system constraints. A variety of simulation results reveal that our proposed energy allocation method combined with adaptive modulation offers better performance compared with the classical cooperation scheme where energy resources are equally distributed over all nodes.