New Approach To Ad Hoc Networks For First Responders Debuts

On Aug. 5, in conjunction with the 2008 Workshop on Precision Indoor Personnel Location and Tracking for Emergency Responders at Worcester Polytechnic Institute in Massachusetts, NIST information technology experts put their version of a “breadcrumb communication system” through its paces. The system is highly automated so that it can be deployed on the fly. It features “smart” multihop relays—sometimes referred to as “breadcrumbs”—that, in effect, advise first responders when to place the next device so as to extend the communications range.

Assembled from off-the-shelf microprocessors and other standard hardware, the relays incorporate NIST-developed software that monitors the status of radio communication signals. The algorithms embedded in the software rapidly assess the strength of received signals so that the device can automatically alert first responders to lay down the next relay before they walk out of range and lose the radio signal.

Other approaches to setting up ad hoc wireless networks in emergency situations typically instruct first responders to lay down breadcrumb relays, for example, in distance increments, around every corner in corridors, or in every stairwell. “Static rules do not take into account all the environmental variables that affect signal degradation, such as attenuation, fading and interference,” explains NIST’s Nader Moayeri. “The communication range in a commercial building corridor is vastly different from that of a factory floor, which is unlike a coal mine.”

That’s why Moayeri, Michael Souryal and other members of the NIST team developed software that implements an “adaptive strategy” for maintaining connectivity. Their approach builds on NIST’s extensive research on measuring and monitoring radio signals in buildings.

Automated deployment of relays, Moayeri says, is a key performance requirement because it does not divert the attention of emergency personnel. The NIST software also provides advice on placement to improve the robustness of signals. The NIST researchers evaluated their adaptive breadcrumb deployment strategy in computer simulations of a wide variety of emergency scenarios and in several field tests. Tests were conducted with two prototype breadcrumb radio systems developed at NIST, one operating at 900 megahertz and the other at 2.4 gigahertz.

Candidate approaches to maintaining continuous communication links between responders and incident command centers were evaluated on the basis of number of signal packets lost in transmissions, number of relays deployed, and delays in end-to-end communications.

The NIST team is interested in sharing their prototype technology and its underlying concepts with businesses and other organizations working to improve the quality and reliability of first responder communication systems.