Title: WiFiNetMon: Interference Measurement in Long Distance WiFi Mesh Networks
Abstract:
Over the past few years long distance WiFi links have emerged as a viable option to provide connectivity to rural regions. Its cost effectiveness compared to wired networks has been particularly attractive. However, networks consisting of such links has been a topic of research only recently. As a result, although several long distance WiFi deployments exist, little has been done in the area of network monitoring and management for such networks. WiFiNetMon is an initiative taken at IIT Kanpur to deal with this dimension of long distance WiFi links. This thesis forms an integral part of this initiative.
In this thesis we focus on measurement of interference experienced by the links of a long distance WiFi network. We measure (a) the link signal strength for each link in the network, (b) the interference experienced by each link in the operational network, (c) the interference experienced by a link if all other links were running on the same channel (same channel interference), and (d) the interference experienced by a link if all other links were running on a non-overlapping adjacent channel (adjacent channel interference). We handle the problem of the interference range of a node being larger than it's trans- mission range by clever use of transmit power and transmit rate during measurements. The tool developed as a part of the thesis is able to deal with temporary unavailability of some links of the network. It performs the above measurements with minimal overheads, rendering the parts of the network non-functional for less than 1 second per experiment per- formed. Our solution incurs an estimated bandwidth overhead for measuring interference of only about 3% of the available throughput, for the Ashwini network, which is a deployment of 21 nodes in West Godavari district, Andhra Pradesh, India. The measurements obtained through the tool are intended to act as primary information to study the health of a network and also form the source of information for a network management tool.