Multi-power Allocation Under The Primary User Traffic Based On Cognitive Radio

In recent years, due to the lack and the low utilization of spectrum, the development of communication technology is severely limited, therefore, the study of cognitive radio communication is becoming increasingly important. Cognitive radio communication technology can be used to solve these problems, firstly, the communication device parameters can be changed in real time, so that the secondary user may dynamically access and timely departure of authorized bands, consequently improving the frequency utilization. Secondly, in cognitive radio, according to the sensing results, the transmission power can be flexibly assigned, while meeting the needs of authorized users, the benefits of cognitive communication system can be maximized. Therefore, with the development of cognitive radio technology, the improvement of the quality of the communication service, is significant for everyone, and thus become important research issue.Based on the aforementioned cognitive radio technologies, following work has been done in this paper:Before the cognitive user access the frequency band, it needs to sense the primary user’s state. Sensing results can be generally divided into two states: idle and busy, followed by a power transmission according to the sensing results. However, due to the sensing imperfections, coupled with a high level of activities of the primary user, the performance of the cognitive system will be greatly reduced.To solve the above problems, this paper conducted a simulation and verification. As the primary user’s level of activities increased, the changing states and trends of the second-user’s throughput, optimal sensing time were predicted in this paper. Compared with the traditional models, the correctness of the proposed ideas were analyzed and verified.The above shows that within the time of one frame, the primary user’s status may change at any time, especially when the primary user was in a very busy status or the sensing time was set in a long period. Assuming that in the time of one frame, the primary user status can only jump once, based on the primary user’s status changing during the sensing and transmission slots, this status can be divided into four status, and distribute large, medium or small transmission power for each status. That is, in the sensing period when the main user does not change its state, the transmission is set in middle power. Hoping from high level into low level, the transmission power is set in a small power, hopping from low level into high level, the transmission power is set in a large power. Researches has been put on the performance status based on cognitive systems and multi power states, simulation and verification were conducted in this paper too. Simulation results show that the throughput under the new model of the cognitive system is related to the authorized users active Index. When the authorized user’s activity index is high, the proposed power allocation strategy in this new model is superior to traditional methods. And, Some other factors are analyzed on the objective function, such us interference power.