Research On Multi-access Network Selection Methods In Heterogeneous Wireless Networks

The difference and diversity of heterogeneous wireless networks lead the integration of heterogeneous network to be the developing trend of the next generation wireless networks. Network integration implements a variety of wireless access technology organically, including the existing and the future ones, to meet users’ demand for various traffic classes in the future. As the key technology of heterogeneous network integration and wireless resource management, network selection algorithm aims at providing users with satisfactory quality of service and is becoming a hot research topic in the field of communication.The theory of multiple attribute decision making has been widely used in heterogeneous network selection. Based on the previous multiple attribute decision making algorithms, a new heterogeneous network selection method is proposed in this thesis. The algorithm, which is based on group decision theory, combines weight vectors of multiple attribute decision to obtain a comprehensive weight vector. Then the compatibility of results will be assessed. The judgment matrix should be modified until a comprehensive vector that satisfies compatibility requirements is produced. Then it will be combined with simple weighting method for network selection. By combining multiple weight vectors, the algorithm is capable of giving full consideration to the objective attribute of network, user preferences and traffic classes. The simulation results show that the algorithm can provide users with satisfactory quality of service.Based on access to multiple networks simultaneously, a new heterogeneous network selection method is put forward. From the view of mobile terminal, overall planning is carried on in the multi-access module. According to the received signal strength and access possibilities, the available network set and target network set are determined respectively. The calculation of throughput, access cost, power consumption and load balance parameters is combined with the weight vector to form a new multiple attribute decision making problem. Finally, the grey relation analysis is adopted to solve the problem. The simulation results demonstrate that, comparing to the single network selection and other multi-access method, the proposed algorithm would significantly improve network performance with different weight vectors.To further enhance the system performance of the heterogeneous network selection algorithm, a birth and death process enhanced utility optimization method for multi-access selection in heterogeneous wireless network is put forward in this thesis. The method adopts the birth and death process to analyze the system performance, fully consider users’ mobility and then obtains network joint utility optimization mode. To maximize the joint utility, the proportions of different multi-access selections in heterogeneous wireless network overlapping region should be well arranged. The Subgradient method is adopted for obtaining the best proportions for solving this optimization problem. The simulation results show that the method can maximize system utility, effectively improve throughput and make the radio resource allocation more efficient.