A Measurement Study on Link Capacity of a High Stress IEEE 802.11b/g Network

The paper presents results from a link capacity measurement study conducted over an IEEE 802.11b/g network with highly stressed radio propagation conditions in a football stadium. Existing capacity studies for IEEE 802.11 networks have considered either stationary or statistical multipath fading channel conditions. In an environment with a high density of people and movement such as in a football stadium or a subway station, the radio characteristics vary much more vibrantly, and their impact on network capacity is not well understood. As a first step to better understand such network characteristics, the study examines the throughput of a mobile terminal over the stadium network in the presence of varying radio conditions due to movement of people and concurrent transmissions by other IEEE 802.11 devices. The study uses a novel approach to quantify network utilization by the experiment terminal as well as other contending terminals, using a recorded packet trace. From the measured utilization, throughput, and signal strengths, key observations made include the fast variations in signal strength due to crowd movement, through put's dependency on signal strength and chosen link rate, and contention with other terminals. Based on the findings, the paper discusses useful insights for performance assessment, protocol enhancements, and improvements in measurement methodology for such networks.