Operators of 3G data networks need to distinguish the performance of each geographic area in their 3G networks to detect and resolve local network problems. This is because the quality of the “last mile” radio link between 3G base stations and end-user devices is a crucial factor in the end-to-end performance that each user experiences. It is relatively straightforward to measure the performance of all IP traffic in the 3G network from a small number of vantage points in the core network. However, the location information available about each mobile device (e.g., the cell sector/site that it is in) is often too stale to be accurate because of user mobility. Moreover, very costly infrastructure deployment and maintenance of custom equipment would be required to collect fine-grained location information about all mobile devices on an on-going basis in large 3G networks. Thus, it is a challenge to accurately assign IP performance measurements to fine-grained geographic regions of ...