Research On Offloading Scheme In Dense Heterogeneous Networks

With the explosive growth of data traffic in recent years, the capacity of current cellular mobile networks is almost pushed to its limit. In order to solve the contradiction between the increasing demands for mobile communication networks capacity and the limited spectrum, the dense heterogeneous networks arises at the historic moment. Dense heterogeneous networks improves the networks capacity to some extent,but the increase of resource dimension also brings enormous challenges to resource management. Therefore, traffic offloading is proposed to realize the adaption between traffic and resource and further improve mobile communication networks capacity by offloading the traffic originally within cellular networks to the complementary networks.Aiming at offloading scheme in dense heterogeneous networks, the main innovations and major work of the thesis are as follows:To solve energy inefficiency problem in heterogeneous networks scenarios with Wireless Local Area Networks (WLAN) and cellular networks, effective capacity based delayed offloading scheme is proposed to maximum the system energy efficiency under the constraint of satisfying user Quality of Service (QoS) requirements. We introduce the effective capacity to model the user QoS requirements and then divide the delayed offloading scheme into two steps. Firstly, we adopt the k-means algorithm to cluster the user with relatively lower service quality in cellular networks as WLAN user, who will be offloaded to WLAN to improve the system energy efficiency. Secondly, the re-allocation in the cellular networks is conduct with dynamic programming solution for further improving the system energy efficiency. Simulation results evaluate the two-step improvements of system energy efficiency achieved by Wi-Fi offloading and resource re-allocation. The conclusion is drawn that looser delay constrains lead to a higher system energy efficiency.To solve the incentive delayed offloading problem in heterogeneous networks scenarios with Wireless Local Area Networks and cellular networks, reward based delayed offloading scheme is proposed to balance the user quality of service and the reward cost of the operator. We formulate the delayed offloading scheme as a two-stage Stackelberg game and investigate under the conditions of complete information and incomplete information, respectively. Considering the position of user,the delay tolerance of traffic, the reward cost of the operator, the networks congestion, the quality of service experienced by user and the throughput of WLAN, we discuss the equilibrium in two cases and then propose the optimal reward based delayed offloading scheme. Simulation results show that larger delay-tolerant factor and more WLAN APs (Access Point)result in smaller reward. Simulation results verify that the proposed scheme can effectively improve the offloading proportion and the overall rate experienced by the users, reduce the operating cost.