Spring model-based call admission control mechanism for high-speed railway environment

Call admission control in mobility environment is a challenging issue. For high-speed railway environment, call admission control mechanism needs to be designed in order to admit more users when system bandwidth resource becomes scare. In this paper, a call admission control mechanism based on spring model is proposed. Although system bandwidth resource is occupied by existing users, a part of bandwidth resource can still be borrowed from them on condition that their lowest qualities of service could be guaranteed. Therefore, every existing service is regarded as a spring that can be compressed to some extent. Handover users who have higher priority than new users can be admitted by the above bandwidth resource borrowing strategy. Moreover, birth-death process is used to analyze dropping probability and blocking probability. Simulation results show that dropping probability of handover users is lower than blocking probability of new users. In addition, dropping probability of voice service is lower than that of data and video services.