Research On Power Control In Cognitive Heterogeneous Network

With the rapid development of information technology, the diversity demand of data service continuously increases. Multiple networks service for users of different demand, and then the heterogeneous networks appear. Heterogeneous networks have wide application prospects which can solve the problem of uneven distribution of users. But interference exists between different networks. Cognitive radio has the character of sensing and intelligent allocating the spectrum which can effectively control and reduce the interference. Recently, researchers from different countries make further researches in cognitive radio technology and the standards are raised continuously. Power control technology is able to reduce interference under the premise of improving the spectrum efficiency. It becomes a research hotspot and one of the key technologies.Network selection and cross-layer interference are the main problems faced by heterogeneous networks. Based on the literature and research situation in recent years, we make further research on the problems. Specific research works and innovations are described as follows:(1)In a heterogeneous network consists of two networks, an access control algorithm based on association probability is proposed. The access probability function is put forward and the effect of cognitive users transmission power on the access probability is discussed. Cognitive users can access better network through controlling the transmission power of femtocell base station. The transmission rate can also increase under the premise of not interfering the primary users. The existence of optimal power is proved through rigorous mathematical derivation. The simulation results show the algorithm in this paper can make cognitive users access better network, so as to improve the system capacity effectively.(2)In order to control the cross-layer interference in two-tier networks, a hierarchical power control algorithm is proposed. Transmission power of macro users and femtocell users are controlled respectively to reduce the cross-layer interference in the system consists of macro cellular network and femtocell network. Macro base station determine the transmission power of macro users according to the aver uplink power budget. Then macro base station imposes a fee for the uplink interference from femtocell users, so as to achieve the target of controlling the interference of femtocell users. The simulation results show that the capacity of both the macro users and the femtocell users improved.(3) An uplink power control algorithm is put forward to address the uplink interference management problem based on dynamic interference temperature in heterogeneous networks where the underlay femtocell users share the same licensed spectrum with the macro users. In the algorithm, interference temperature dynamically adjusts according to the channel status and the number of femtocell users. We show that our proposed power-update function has one fixed-point. Simulation results show that the algorithm increased the number of femtocell users supported and has a better outage ratio for macro users.