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:
Voice Communication:
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.
Indoor Localization:
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.
External Communication:
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
