ARTEMIS - Ad Hoc Routing - ISTS

CERT

WIRELESS NETWORKING

In a emergency/disaster environment, a wireless communication network provides an efficient means of communication among first responders. With the possible absence of a permanent network infrastructure, the first responders themselves must act as an ad-hoc wireless network, routing packets between each other dynamically. Limited transmission range means that a responder might not always be within direct transmission range of a destination (e.g. their commander); as a result, packets must be intelligently routed so that they arrive at their destination. Because of the potential for constant movement of individual and groups of responders in the field, the wireless network must maintain a dynamically updated routing system for transmitting messages.

Urban settings, in particular, present a unique challenge to the transmission of data between responders, due to the increased number of obstructions in those environments. Walls and other obstructions within a single building can prevent direct transmission between two responders, highlighting the need for an intelligent routing algorithm that is designed to handle these types of obstacles.

RELIABLE MESSAGING

The ARTEMIS project has selected and implemented the On-demand Multi-cast Routing Protocol (ODMRP). In ODMRP, transmission of routed data is accomplished in an "on-demand" manner. In other words, if no route exists, the transmitted data is concatenated with a "join_request" bearing the sending node's address. The "join_request" floods the network until it reaches the destinations of the transmission. Upon reception of the "join_request", destination nodes reply with a "join_reply", which propagates back to the originating node, which now has a valid route to a multicast group. Through backward-learning, intermediate nodes form a mesh network, which can route any data within the local multicast group, and adaptively compensates for link failure and degradation. This architecture provides reliable, dynamic routing tables, which are highly adaptable in situations with rapidly changing topologies.

ARTEMIS has implemented the ODMRP protocol in C# for the Microsoft Compact Framework. This gives the ARTEMIS medic and casualty handheld applications running on the Pocket PC reliable, mobile networking. ODMRP proxies allow other applications, such as Command Control software, to consume data generated by the sensor system. Network data and statistics are being collected during live emergency response exercises and ODMRP performance will be evaluated and published.