The NIST Distributed
Testbed for First Responders (DTFR) is a project to examine the role future
technologies could play in first responder communications. Instead of being a
dedicated radio, each node in the testbed is a handheld computing device. We
chose to use Hewlett Packet Ipaqs because of their battery life and ability
to run the Linux OS. The Ipaqs communicate with each other using 802.11b
radios. While we do not see these radios being powerful enough for real world
use, they provide a good research platform.
Instead of communicating through an access point, the nodes in the testbed communicate directly with each other. This ad-hoc form of communication allows for more dynamic configurations. Each node also runs specialized routing software that turns them into routers in addition to communication devices. This allows each node to serve as a repeater. Now nodes that are out of range can communicate through a node that is in the middle. The routing software finds an optimal route between the two nodes in order to make the best use of the bandwidth and provide the best quality of service.
There are three major components to the DTFR:
The DTFR provides first responders with digital Voice-Over-IP communication capabilities. This means that traditional radio traffic is digitized and turned into IP packets and then sent out over the network formed by the devices. Since packets are used it is not limited to the traditional channel model of radio communication. You don't have to worry about a radio channel becoming too crowded; instead, you can create a dynamic group of people you want to talk to and only send packets to them. You can still talk to everyone at once by broadcasting your packets.
Since communication gets turned into packets, you are able to take advantage of some of the advanced routing capabilities built into every node. Instead of having your communication range limited by the range of your radio, you are able to have other nodes repeat your message. This helps eliminate radio dead spots and ensures that everyone in the group remains in contact. Each node sends out a small status packet which informs you who you can currently communicate with and the status of that person. Using this feature you can monitor statistics such as heart rate or temperature.
There are many instances where current localization technologies, such as GPS, do not function. Urban environments and inside of buildings are two environments where GPS has trouble working. We have developed a system to overcome this and allow first responders to find their position along with the position of other members in the area. In order to calculate a first responder's location, fixed reference nodes must be distributed in the area. The first responders then calculate their locations using the signal strength of these reference nodes. Our system allows first responders to find their locations within 1 to 3 meters. This is invaluable in smoky environments where visibility is low.
Our system also distributes each node's location to all the other nodes. This allows better management of personnel and helps in case of an incident. It displays a user's current location along with other members' locations on a map of the floor. In our testbed the map is preprogrammed; however, in a deployed system the map could be provided by a GIS system or created on site.
The DTFR allows for offsite communication. This could be used to communicate with a regional headquarters or an expert in a field. Communication is established through a gateway with an internet connection. This is enabled by using the Session Initiation Protocol (SIP) that establishes calls into or out of the system. SIP allows for a dynamic forwarding of calls, so as a user moves from using one device to another, external calls will be correctly forwarded. Using SIP and the correct gateway, a node can communicate with a regular telephone or a SIP-enabled application like Microsoft Messenger.
Contact: Luke Klein-Berndt
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Date Created: May 2001
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Last updated: March 21, 2002