Can they hear me now?: a case for a client-assisted approach to monitoring wide-area wireless networks

We present WiScape, a framework for measuring and understanding the behavior of wide-area wireless networks, e.g., city-wide or nation-wide cellular data networks using active participation from clients. The goal of WiScape is to provide a coarse-grained view of a wide-area wireless landscape that allows operators and users to understand broad performance characteristics of the network. In this approach a centralized controller instructs clients to collect measurement samples over time and space in an opportunistic manner. To limit the overheads of this measurement framework, WiScape partitions the world into zones, contiguous areas with relatively similar user experiences, and partitions time into zone-specific epochs over which network statistics are relatively stable. For each epoch in each zone, WiScape takes a minimalistic view --- it attempts to collect a small number of measurement samples to adequately characterize the client experience in that zone and epoch, thereby limiting the bandwidth and energy overheads at client devices. For this effort, we have collected ground truth measurements for up to three different commercial cellular wireless networks across (i) an area of more than 155 square kilometer in and around Madison, WI, in the USA, (ii) a road stretch of more than 240 kilometers between Madison and Chicago, and (iii) locations in New Brunswick and Princeton, New Jersey, USA, for a period of more than 1 year. We justify various design choices of WiScape through this data, demonstrate that WiScape can provide an accurate performance characterization of these networks over a wide area (within 4% error for more than 70% of instances) with a low overhead on the clients, and illustrate multiple applications of this framework through a sustained and ongoing measurement study.