Research On Spectrum Sharing Protocol Based On Transform Domain Processing

As one of the key technologies in cognitive radio system, spectrum sharing can guarantee the coexistence of primary and secondary users in the licensed frequency band without adversely affecting the primary system, which has attracted more attentions in wireless communication fields. In this paper, transform domain processing technology and cooperation communication technology are introduced to spectrum sharing technology, which can greatly reduce the interference to the primary users and achieve diversity gain through the cooperation between primary users and secondary users to improve spectrum utilization.Firstly, the key technologies in cognitive radio networks are briefly introduced. Spectrum sharing system architecture, technology classification and several cooperation schemes in cooperation spectrum sharing technology are analyzed. Then we study fractional Fourier transform(Fr FT) technology and verified the signal separation property of cosine signals and chirp signals in the Fr FT domain.Then we propose a spectrum sharing protocol based on transform domain processing with the given instantaneous channel gain. In our proposed protocol, we use cosine signal and chirp signals for primary user and secondary users, respectively. Moreover, secondary users can take the initiative to access the spectrum or act as a relay to assist the primary system adaptively according to the channel conditions of the direct transmission link. Moreover, the joint optimization of power allocation and distributed secondary users selection based on instantaneous channel gain is studied to achieve the maximum achievable data rate for the secondary system while guaranteeing the target data rate of primary user. Simulation results show that compared with existing protocols, the interference to the primary users can be greatly reduced, and the outage probability of both primary and secondary systems can be improved. Moreover, a better communication performance of the secondary system can be obtained with the increase of transmit power and the number of secondary users.Finally, in order to solve the problem that a lot of signaling overhead needs to be costed to obtain instantaneous channel gain in actual system, we focus on the spectrum sharing protocol based on transform domain processing with the given statistics of channel gain. In our proposed protocol, secondary user can adaptively select appropriate cooperation scheme according to the channel conditions. Then, the optimization of power allocation scheme based on the statistics of channel gain is analyzed to minimize outage probability of the secondary system while guaranteeing the outage probability constraint of primary system. Then, a secondary user selection algorithm based on the average channel gain is proposed to further improve the performance of spectrum sharing. Simulation results show that compared with existing protocol, the interference to the primary users can be greatly reduced. Lower outage probability and higher achievable data rate of secondary system can be realized while guaranteeing the communication requirements of the primary system in our proposed protocol. Moreover, with the increase of secondary user number, the performance of both outage probability and achievable data rate is significantly improved for the secondary system.