Research On Spectrum Access Strategies With Two-way Cooperation

With the rapid development of technology, wireless communication plays an important role in people’s daily life, which not only improves people’s work efficiency, also facilitates people’s entertainment. To better guarantee the quality of wireless communication service, constructing a higher transmission rate and spectrum utilization efficiency wireless communication network is an urgent problem to solve currently.Cognitive Radio(CR) can effectively improve the system spectrum utilization efficiency by sharing the wireless spectrum resource. In addition, with its channel diversity gain, the cooperative communication technology can enlarge the wireless capacity and improve the reliability of the signal transmission. The combination of cooperation and CR technology is one of the main research recently. However, due to the half-duplex mode, one-way cooperation exists inherent spectrum loss problem. In this paper, we study the interference problem between the primary user(PU) and secondary user(SU) and SU transmission performance optimization problem by introducing two-way cooperation based on the combination of CR and cooperation technology. The main work and achievement are as follows:1、We propose a two-way cooperative spectrum access strategy based on power allocation in wireless two-way cooperative system. With the decode-and-forward(DF) relay mode, SU uses part of the power to help forward PU signal and uses the remaining power to send its own signal, which maximizes SU’s transmission rate while guaranteeing the PU to achieve its target rate. Simulation results show that by comparing with the direct communication and fixed power allocation, the proposed strategy has better adaptability in improving PU performance. It can help SU achieve larger transmission rate.2、In order to further solve the mutual interference between PU and SU in the two-way cooperative spectrum access strategy based on power allocation. We propose two two-way cooperative spectrum access strategies based on the time and bandwidth allocation, in which, two benefits can be gained through the optimization of time and bandwidth. Firstly, the interference between PU and SU can be eliminated by using different bandwidth to send primary and secondary signals. Secondly, SU can gain more transmission time to transmit its own signal which leads SU achieves larger transmission rate. Simulation results show that the two proposed strategies can overcome the shortage of the two-way spectrum access strategy based on power allocation, and the SU can gain larger spectrum access region and larger transmission rate.