Improved Connection Quality for Lowest-Priority VoIP Calls in Emergency CAC Method with Waiting Queue

During emergencies, ensuring connection to emergency calls to contact an ambulance or fire brigade is crucial. Telecommunication networks face congestion in emergencies due to increased emergency and safety confirmation calls. Call admission control (CAC) has been proposed to handle these congested network environments. Our previous CAC method categorizes calls into emergency calls, calls from the disaster area, and calls from outside the disaster area in the Voice over Internet Protocol (VoIP) network. As a result, the optimal thresholds are derived that guarantee the quality of high-priority VoIP calls. However, the lowest-priority VoIP calls are also important calls in an emergency. In this paper, we propose a novel emergency CAC method with a waiting queue for lowest-priority VoIP calls that considers early departure. The early departure refers to the process of reneging in a queuing model with customer impatience. We analyze the connection and communication quality. From the analysis results, our proposed CAC method improves the connection quality of lowest-priority VoIP calls while maintaining the connection quality of high-priority VoIP calls and communication quality of all VoIP calls. Moreover, we analyze the characteristics of the proposed CAC method when the rate of early departure and the maximum number of the accommodated lowest-priority VoIP calls in the waiting queue change.