Kuklov V. Method of mobile user connection handover for heterogeneous software-defined network

The dissertation is devoted to solving the problem of improving the quality of provided services to mobile subscribers of heterogeneous software-defined networks on the basis of the proposed methodology, which allows taking into account the state of the heterogeneous network at the moment of mobile subscriber call transition taking into account the load of the node and the strength of received signal by the mobile subscriber. With the advent of active technology of high-speed mobile Internet access in Ukraine, the traffic of data in cellular networks is constantly increasing. At the same time, existing network architectures were not designed to meet the needs of operators, modern users and enterprises. Traditional solutions to the problem of seal coverage, the deployment of which requires significant capital costs, do not solve the problems associated with the expansion of data channels from the base stations to the core infrastructure of the network operator. As the demand for mobility and bandwidth increases, and profits are blurred by the growth of capital costs for equipment, there is a problem of the quality of providing multimedia services to mobile subscribers. An alternative to solving these problems is the Wi-Fi Offload method, which is designed to unload mobile operators' networks from data traffic through the use of Wi-Fi technology. In this case, subscriber data traffic is output from the operator's radio network into a separate radio network that runs using its own trunk channels, which allows the user to forward data through various wireless technologies and mobile networks. Until now, one of the obstacles to unload mobile operators' networks from data traffic due to the use of Wi-Fi Offload technology remains the lack of clear methods and criteria for making a decision on the transition between cellular networks and Wi-Fi that take into account load balancing tasks in a heterogeneous environments. The analysis of known mathematical models and methods of service of transition of mobile subscribers generating traffic within the framework of the functioning of heterogeneous, wireless and software-defined networks was made. Based on the analysis, it was shown that there is no explicit methods and criteria for making a decision about the transition between 3G/4G and WI-FI. The method of calculating the rates of user's stay and service in the area of a dedicated cell of a heterogeneous network was improved. The method takes into account the length of the mobile user's delay in the service area, the size of the outgoing call in the dedicated cell, and the duration of the callback. The mathematical model of mobile subscribers connection transmission to heterogeneous wireless network was improved, with the consideration of outgoing call intensity, horizontal and vertical transient calls intensities. A method for transferring the connection of mobile subscribers to heterogeneous software-defined networks was improved. The method takes into account the complementary normalized use of the network and the relative signal strength indicator of the network, which allows take into account the state of the heterogeneous network for the moment of switching mobile subscriber between different types of wireless networks. The probability of blocking outgoing calls in different areas is analysed according to the cases of the highest priority of traffic, the highest priority of the power of the received signal and the parameters obtained from the proposed methodology. Following algorithms were developed: algorithm of an iterative relaxation method for finding balanced equations of states; algorithm of transfering mobile subscribers' connection within heterogeneous software-defined networks. In order to confirm the adequacy of the obtained scientific results, a practical implementation of the improved method of mobile user connection handover for heterogeneous software-defined network has been carried out. A test virtual environment was developed based on the technology of software-defined networks, which tested the developed methodology. The use of the proposed method allows reduce the probability of blocking outgoing calls by 11-15% compared to the known ones. This gives the opportunity to improve the quality of service providing to mobile subscribers of heterogeneous software-defined networks.