Wireless Multihop Communications for First Responder Connectivity

First responders, using current radio communication technologies, entering a large building can lose radio communications with their incident command due to propagation loss of the radio signal with distance and obstruction. Multihop wireless networks, using intermediate nodes to relay the signal over multiple, shorter hops from source to the destination, have generally been proposed as a means of extending radio coverage. In this thesis we demonstrate real-time deployment of a multihop network to maintain communications between incident command and a first responder entering a building. The system continuously assesses the channel and determines when a new relay needs to be deployed. As the first responder moves deeper into a building, a communications link is automatically configured over which data traffic is transmitted end-to-end. In addition to the deployment algorithm we present how power control of the relay nodes can be used to maintain good radio link quality. To access the network we present a routing protocol, which is particularly adapted for this type of fast changing ad-hoc network. The prototype system of this thesis is implemented on 900 MHz Crossbow mica2 motes supporting periodic transmission of sensor values (e.g., vital signs of the first responder) to the incident command as well as two-way text messaging and Radio Frequency Identification (RFID) information captured by the first responder. We evaluate the prototype system inside a common American five floor office building. The achieved results show that the proposed system is well suited for first responder connectivity.