Towards Anomaly Detection in One-Way Delay Measurements for 3G Mobile Networks: A Preliminary Study

In this paper we investigate the dynamics of one-way delays in an operational mobile core network. Our ultimate motivation is to develop anomaly detection schemes for the packet delay process in order to reveal network and equipment problems. This requires an online measurement system capable of collecting and processing delay statistics in real-time. We present an experimental deployment of such a measurement system in an operational General Packet Radio System (GPRS) /Universal Mobile Telecommunications System (UMTS) network and elaborate on some practical implementation issues. We present some measurement results for the Serving GPRS Support Nodes (SGSN) of UNITS and GPRS. We find that the delay at a UMTS-SGSN is moderately influenced by user mobility, while flow control and user mobility are considerably impacting the delay process at a GPRS-SGSN. We show that simple summary indicators can be extracted from the delay statistics, as a combination of percentiles and threshold-crossing probabilities. Such indicators can be used for the purpose of detecting abnormal delay deviations, pointing to problems in the network equipments.