This paper describes a wireless mesh network testbed for research in rapid deployment and auto-configuration of mesh nodes. Motivated by the needs of first responders and military personnel arriving to an incident area, we developed and tested an automated deployment algorithm that indicates when a mesh node needs to be deployed as the coverage area grows. Conventional radios can experience severe coverage limitations inside structures such as hi-rise buildings, subterranean buildings, caves, and underground mines. The approach examined here is to deploy wireless relays that extend coverage through multihop communication using a deployment algorithm that employs physical layer measurements. A flexible platform based on IEEE 802.11 radios has been implemented and tested in a subterranean laboratory complex where conventional public safety radios have no coverage. Applications tested include two-way voice, data, and location information. This paper describes the testbed, presents experimental results, and recommends areas for further study and development in rapidly-deployable multihop networks.

This paper investigates methods for link quality measurement of an indoor, time-varying wireless link. Link quality estimates are used for a number of higher-layer functions, including rate adaptation, routing, and topology control. The objective is to rapidly and efficiently estimate the current reliability of an RF link in terms of its packet success probability in the presence of a time-varying channel. We compare various approaches to estimating the current packet success rate (PSR), including packet counting and several methods employing physical layer signal-to-noise ratio (SNR) measurements. Among the SNR-based estimators, we consider those using a simple moving average, an exponential moving average, and a Yule-Walker predictor of the current SNR. The analysis shows that the SNR-based estimators are more efficient than packet counting methods in terms of the number of measurements needed, are more accurate when link quality variability increases, and are more flexible in terms of predicting the PSR for various bit rates and packet sizes. An important requirement, however, of the SNR-based estimators is a priori knowledge of the SNR-PSR relationship, which is environment- and radio-dependent. An efficient methodology for obtaining this mapping is presented.

This demonstration shows how to use external databases to provide an efficient implementation of a timetravel service. The timetravel semantics are defined using snapshot isolation. The system presented not only allows to retrieve older snapshots but also to identify snapshots of interest.