Content Distribution Technology Research In Heterogeneous Cellular Networks

Nowadays, the demand for data services is gradually increasing. The initially form of web browsing have been transformed to large file transmission, such as videos. Besides, mobile users tend to pursue higher quality of service. These factors bring greater challenges for the future cellular network. In the future mobile communication network, D2 D communication is considered as a key technology to further improve the system capacity, without extra stations and new spectrum resources. So, this paper firstly studies a new content distribution mechanism for mobile users, and then, studies the content distribution for deadline constrained traffic.D2D communication based content distribution could make users in proximity directly transmit data without forwarding by base station. This kind of data transmission can work well when users are static. However, when user moves, the data transmission process would be interrupted if the distance between users exceeding the D2 D communication range. As the movement of users is uncertainly, the transmission failure probability caused by movement is relatively large. Concerning to this problem, our paper proposes a method that multiple users simultaneously help one user for content distribution based on 3GPP protocol. It also gives the specific transmission scheme under the support of protocol. Our scheme not only can alleviate the burden of base station by using D2 D, but also can ensure the complete receiving when users are mobile.Besides, our paper studies the content distribution process for deadline constrained traffic. Base station first multicasts the content to a certain set of users. Then, users who have received the content can further multicast the content to the other users in D2 D multicast mode. D2 D multicast makes the throughput of system improved. We analyze the problem from theoretical aspect with the objective of obtaining the system capacity. Our paper formulates the problem as a linear programming model with several constraints and discusses the content distribution for single rate case and multi-rate case. Concerning to these two cases, we respectively derive the optimal scheduling policy by using different algorithm in MDP theory. Besides, as the algorithm complexity is relatively high, a sub-optimal low complexity scheduling method is proposed. Simulation results show that the proposed MDP optimal scheduling policy can effectively improve the throughput of system, compared with the existing scheduling method.