Limiting UMTS Dropping Rate with Control-Based CAC Algorithm

The resource consumption of mobile users within a UMTS communication system fluctuates over time due to their communication behavior and the link quality. Due to the limited resources of UMTS systems congestion may occur. The rising needs for resources may even force the system to drop active calls. In order to prevent such dropping events, permission requests for new calls may by rejected, if the system load is high or is expected to be high in the future. In this paper we present a control theory approach for adjusting the UMTS RRC call admission control threshold according to the current traffic situation in a UMTS cell. This algorithm prevents the dropping rate to exceed a predefined limit, as shown by our simulation results