Research On Power Allocation Strategy Based On Effective Capacity In Cognitive Wireless Networks

In recent years,the rapid advancement of wireless communication and the explosive growth of services have made available spectrum resources increasingly scarce.Therefore,it has become an urgent problem to make full use of limited spectrum resources.Cognitive radio is such a technology which can intelligently sensing the current environment,then changes according to the result of sensing,thus it allows cognitive users timely access authorization band without affecting the normal communication of primary users,improves the system performance,it is one of the most popular research.At the same time,there are more and more services under the wireless communication network,many of them are extremely sensitive to the delay in the process of network transmission,and the demand for the Quality of Service(QoS)is getting higher and higher.Therefore,meeting the delay QoS requirements of different wireless communication services has become a research hotspot.Based on the above situation,it is necessary to discuss the power control strategy considering the time delay in the study of cognitive network.To sum up,this paper mainly does the following work:1)First,in cognitive wireless network,the single power strategy with time-delay constraint under traditional frame structure is studied to maximize the average effective capacity that cognitive users can obtain,and the optimal effective capacity under this strategy is obtained.The single-power strategy assumes that the primary user continues to occupy the channel,so when the primary user does not occupy the channel,it will cause a waste of resources.To solve this problem,two power strategies are proposed.The two-state and two-power strategy assumes that the state of the main user does not change within a frame,while in the actual scenario,the state of the main user may change at any time within a frame.To solve this problem,a new four-state and twopower allocation strategy is proposed.Simulation results show that two-power strategy can significantly improve the effective capacity of cognitive users compared with single-power strategy.2)In the traditional frame structure,a frame is divided into the perception stage and transmission stage.The state information of primary user and channel is acquired in the perception stage,and data transmission is conducted in the transmission stage for cognitive users.However,when the frame length is fixed,the balance between the two needs to be considered.At the same time,using the two-power strategy,when the primary user occupies the authorized frequency band,it will cause a waste of resources if cognitive user recognizes that then uses low-power to access and the primary user withdraws later.When the primary user does not occupy the authorized frequency band,it will affect the normal communication of the primary user if the cognitive user uses high-power to access and the primary user suddenly returns.In order to solve these problems,this paper proposes a four-state and three-power model based on the sensing/transmission frame structure,so that both the sensing time and the transmission time can reach the theoretical maximum value,so as to maximize the effective capacity.Simulation was carried out to verify the feasibility of the new strategy.The results showed that compared with the single power strategy and the two power strategy,the effective capacity obtained by the three-power strategy was significantly improved.In addition,other factors affecting the effective capacity were analyzed.