The Research Of Access Selection Algorithms For 5G Ultra-dense Networks

With the development of science and technology and the improvement of people's living standard, the demand for communication is increased from the separate voice call business to today's data,multimedia and other real-time business. At the same time, various communication scenarios also involve all aspects of life and work.Mobile data has shown explosive growth. Although existing fourth generation mobile communication systems (4G) technology is becoming more and more mature, it still can not meet the growing demand for data traffic. Therefore, fifth generation mobile communication (5G)technology has been proposed. Ultra-Dense Network (UDN) is an effective way to improve the throughput and resource utilization in 5G network, which is suitable for the typical scene with high traffic density and large number of concurrent connections in the unit area. A variety of heterogeneous access point are deployed indoor and outdoor to achieve intensive deployment, including different kinds of femtocell and micro base stations and so on. This may shorten the distance between the access point and the user, greatly reducing the attenuation of the signal, and ensuring the quality of communication. However, at the same time, the dense deployment of access points has brought a greater challenge to the entire communication system. One of the important issues is access selection strategy. How to select the most appropriate access point according to the needs of users or network among the many access points,is the key direction to be studied to make sure that the users get a better experience and the whole network get better performance. This thesis have researched on this issue, and the main work is as follows:Firstly, an access selection algorithm based on utility function is proposed, which consider the coexistence of heterogeneous access points in ultra-dense networks. By analyzing and comparing the types of traffic and network attributes, a utility function is designed. It can synthetically consider the factors of subjective user selection and objective network attributes. And then the specific access selection algorithm is proposed.Through the simulation results, the proposed access selection algorithm performs well for different types of user service request, according to block specific utility functions values and the overall rate of the network.Secondly, we propose an access selection algorithm based on non-cooperative game theory. Through the non-cooperative game model,the access selection algorithm is designed to improve the overall performance of multiple users in the ultra-dense network. This algorithm considers not only the bandwidth of access selection, but also the blocking performance of each region, which can take into account the overall efficiency of the network and the fairness of the choice. By allocating bandwidth resources to the connected users in each region, it may adjust the number of users, thus ensuring the reliability of the communication. The simulation analysis shows that the bandwidth allocation based on non-cooperative game is effective, and the corresponding access selection algorithm can achieve dynamic adjustment, thus ensuring the efficiency and effectiveness of the overall system.