Multi-Layer Protocol Tracing in a GPRS Network

Andrei Gurtov
Matti Passoja
Olli Aalto
Mika Raitola

In Proceedings of the IEEE Vehicular Technology Conference (Fall VTC2002), Vancouver, Canada, Sepember 2002.

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This paper presents a performance evaluation of GPRS accomplished by combination of measurement at the end hosts and tracing inside the network. The multi-layer tracing approach allows not only observing, but also understanding the network performance. With end-to-end measurements we assess data rates, latency, and buffering experienced by users in a live GPRS network. Comparing the results to our previous measurements shows a notable improvement in the network and terminals over past two years. Mobility tests while driving in the urban environment quantify the interval, duration and data loss caused by cell reselections. In the test lab, multi-layer tracing of radio, link and transport protocols gives a closer picture of GPRS performance. For instance, TCP interacts inefficiently with resource allocation at the RLC layer and fragmentation at the LLC layer. Finally, we illustrate delay spikes and data losses during a cell reselection by tracing of signaling messages during a cell update and routing area update procedures.