Study On Joint Radio Resource Management Technologies For Heterogeneous Wireless Networks

In order to meet the growing diversification of wireless application requirements, various types of wireless networks are integrated together to provide users with heterogeneous network environment. Taking into account the heterogeneous wireless network is very different from single wireless network environment in access technology, network architecture and user mobility, it is necessary for the joint management of heterogeneous wireless network resources to achieve optimal use of radio resources. Many of the key technical issues should be addressed, such as handoff, power control, admission control, etc. This dissertation selectes vertical handoff and joint call admission control techniques for the study and analyzes the key issues involved in the selection of optimal access from different angles. The corresponding algorithms are proposed with their performance analysis by constructing mathematical models and simulations. The main work and contributions of this dissertation are as follows:1. In order to improve accuracy of vertical handoff and to decrease connection dropping, this dissertation improves the RSS-based handoff trigger mechanism and adopts the fuzzy logic-based normalized quantitative decision algorithm to determine the optimal handoff target network from all available access networks. Simulation results demonstrate that this approach outperforms other ones in the number of vertical handoff and handoff dropping rate while choosing effectively the optimum network through making trade-off among the user preference, network condition, and system performance.2. MADM-based vertical handoff decision algorithm is improved. On one hand, the combinational weights are determined by using AHP and entropy methods and on the other hand, different utility functions are used to obtain utility of various services’QoS and power consumption. In addition, the heavy-loaded network is chosen with the reduced possibility by introducing the network load balancing factor. Finally, the utility-based TOPSIS method is adopted to sort the candidate handoff target networks and selects the optimal access network. Simulation results show that the proposed algorithm achieves a balance between the QoS performance and the power consumption while improving the accuracy and stability of network selection.3. An access network selection algorithm which combines distributed selection mechanism and centralized control is used. This algorithm is based on the cost function and integrates the network selection mechanism on the terminal side and the adjustment strategy, so that the heterogeneous wireless system can dynamically changes the network adjustment factor in accordance with the optimal as well as the actual user distribution, thus the network selection process can be guided reasonably. The simulation results show that this algorithm reduces the total cost of the heterogeneous system while meeting the users’ requirements.4. There are various types of services and calls in heterogeneous wireless networks. A joint call admission control algorithm differentiating service and call types is adopted to meet service requirements and improve the utilization of system wireless resources. This algorithm sets multi-level access bandwidth thresholds to determine the priority of various types of services and calls, and takes the bandwidth adjustment mechanism to control whether or not to accept the connection request and the target access network. Simulation results show that the proposed algorithm not only improves the performance of the new call blocking rates and the handoff call dropping rates, but also increases the system resource utilization.