Research On Radio Resource Management In Heterogeneous Wireless Networks

With the fast developing of advanced wireless communication technologies, the deployment of various wireless access networks give mobile users abundant wireless services, together with wider band-width and faster data transmitting rate. At the same time, the diversity of wireless networks and the following non-compatible problem bring mobile users and communication operation enterprises more troubles. Because of the respective features of these wireless access networks such as cover-range, resource management mechanism and service support, the integration of heterogeneous wireless networks has become the inevitable trend. Through the integration of heterogeneous networks with different types and characteristics, mobile users could enjoy ubiquitous, synthetical and QoS-guaranteed services, so as to realize the communication goal of "whoever, whenever, wherever, however, whatever".The integration of heterogeneous wireless network is very complex, in which the key issue is to realize JRRM (joint radio resource management). The performance of integrated system is decided by JRRM, to realize JRRM in heterogeneous wireless networks, several key technologies have to be improved first, such as spectrum sharing, joint call admission control, and joint bandwidth allocation strategy. Some research institutions and project organizations have done relative investigations with plenty of results. However, several problems are still under discussion.To solve above problems, this thesis aims to improve the performance and efficiency of JRRM in heterogeneous networks, emphasizing on joint call admission control, spectrum borrowing, and joint channel allocation schemes. Some improved mechanisms and schemes are proposed, and the performance of these schemes is analyzed through constructing mathematical models and simulations. The major contribution of this thesis is listed as follows:1) Proposing a spectrum borrowing scheme in heterogeneous wireless networks. This scheme takes idle channels into a spectrum pool, with unified management of these channels. All users share them in non-transparent way, and the PRM (Proxy re-configuration management) takes charge in resource allocation and recovery. The proposed scheme designs a spectrum borrowing selection method by the best overall performance criterion, in which spectrum utility is maximized by setting different borrowing levels. Simulation results show that, proposed scheme gets higher spectrum utilization ratio and decreased session blocking probability especially in case of high-loaded environment.2) Designing a joint call admission control mechanism for heterogeneous networks. Based on semi-Markov decision process, this scheme takes overall network throughput as optimal purpose, and gains good expansibility and independency with QoS guaranteed. Simulation results show that, proposed scheme efficiently solves the conflict between unbalanced network load and QoS demand of users. As a result, session blocking probability is decreased and the throughput of networks is promoted.3) Proposing a joint channel allocation scheme in heterogeneous wireless networks. The scheme establishes an optimized model with multiple constraints based on the theory of non-cooperative game, aiming to maximize the overall channel utilization. The fairy and rationality issues are taken into consideration. Simulation results show that, the proposed scheme gets higher bandwidth utility, with better fairness in channel allocation.