Dissecting 3G Uplink Delay by Measuring in an Operational HSPA Network

Users expect mobile Internet access via 3G technologies to be comparable to wired access in terms of throughput and latency. HSPA achieves this for throughput, whereas delay is significantly higher. In this paper we measure the overall latency introduced by HSUPA and accurately dissect it into contributions of USB-modem (UE), base station (NodeB) and network controller (RNC). We achieve this by combining traces recorded at each interface along the data-path of a public operational UMTS network. The actively generated sample traffic covers real-time applications. Results show the delay to be strongly dependent on the packet size, with random components depending on synchronization issues. We provide models for latency of single network entities as well as accumulated delay. These findings allow to identify optimum settings in terms of low latency, both for application and network parameters.