Research On Stable-throughput Of SWIPT Cooperative Cognitive Radio Networks

With the development of wireless communications, the lack of spectrum and high energy consumption have become the two important factors which restrict the development of wireless communications. By using spectrum sensing and power controlling, cognitive radio networks can sharing the spectrum with primary networks which can effectively improve spectral efficiency. In Cooperative Cognitive Radio Network, cognitive node dynamically shares the spectrum with primary node by the way of acting as the relay of primary node, which is a win-win technology. SWIPT provides a new method to prolong the lifetime of the energy-constrained networks. In the SWIPT based Cooperative Cognitive Radio Network, when cognitive user senses the primary signal, it can also collect energy from the RF band at the same time. It can realize the simultaneously information and power transfer, which is an effective way to further improve spectral efficiency.In an SWIPT Cooperative Cognitive Radio Network, there is not something to transmit for both primary user and cognitive user at all the time. That is to say, the moment of a packet arriving and the duration of packets transmission are uncertain, thus the packets in the buffer are not backlogged. According to the unsaturated data traffic, we use stable-throughput to describe the long-term performance of the system. Firstly, the stable-throughput region has been characterized in order to reflect the interaction between PUs and SUs by using Queuing Theory. Then a probabilistic cooperation scheme has been proposed, and by deriving the optimal value of the relaying probability, the stable-throughput of secondary users can be maximized under the constraint of the primary queue stability. Finally, Simulation results and theoretical analysis show that the probabilistic cooperation scheme can achieve maximal stable-throughputs for SUs compared to both the full- cooperative case and non- cooperative case, meanwhile PUs can also have a better performance compared to the non- cooperative case.