On Robust Estimation of Network-Wide Packet Loss in 3G Cellular Networks

In this work we address the problem of estimating the network-wide packet loss rate across the radio access section of a 3G cellular network. The reference scenario consists of a passive monitoring probe located in the core network. The probe counts the number of TCP packets directed to each individual mobile terminal and, from the analysis of (un)acknowledged packets, infers the loss ratio for each individual terminal. The problem is then to derive a synthetic indicator representative of the network-wide packet loss, which can be used to detect largescale performance drifts and network anomalies. We show that common simplistic indicators like the total rate of lost packets (across all terminals) and the average per-terminal loss rate do not work well in the general case. The key problem is the large disparity of traffic volume across individual terminals. In this contribution we formulate the problem in terms of optimal statistical inference and provide a set of robust near-optimum estimators that are relatively simple to implement. We validate the proposed estimators with simulations in synthetic scenarios and provide results from a real operational 3G network.