During times of calamity, such as an earthquake or tsunami, rescue and recovery efforts are usually hampered by communications failure as the incumbent communications infrastructure has most likely been damaged or destroyed during the disaster. An ad-hoc communications infrastructure, with support for multimedia traffic such as Voice over IP and videostreaming, must be quickly put in place to support the command, control and communication needs of the rescue and recovery operations. Such applications require relatively fast and robust communications links, and broadband wireless technologies appear to be a viable solution. This paper examines two hierarchical network solutions which allow the delivery of such mission-critical multimedia data between rescue teams and their headquarters over extremely long distances using a combination of wireless network technologies (namely, WiFi, WiMax and GEO Satellite) and multimedia software applications (in particular, Voice-over-IP) to meet the requirements of disaster rescue communication scenarios. The proposed system has been validated experimentally in the field as well as using simulations to demonstrate the scalability of the design.Keywords-ad hoc networks, wireless broadband networks, multimedia communications, disaster recovery.

Abstract. Ultra Wide Band (UWB)impulse radio is a promising technology for future short-range, low-power, low cost and high data ratead hoc networks.The technology isbeing explored in a number of research projects. While most UWB research for this class of networksisconcentrating on the physicall ayer, little researchh as been published on link layer protocols which exploit the specifics of UWB impulse r adio. In t his paper, w e focus on t he selforganization concept and the peculiarities of UWB technology from aphysical and a link layer point of view. Anovel self-organizing link layerprotocol based on time hopping spread spectrum is proposed in thispaper.This protocol promisest obean efficient and collision-free mechanism t hat enables the devices tod iscover neighbornodes and arrange the access to communication resources shared among the nodes. The adjustable parameters of the protocol enable the network to adapt to a dynamic environment. 1IntroductionArange of services supporting future mobile applications are expected to require high data rates, high communicationquality and efficient network access. A case in point is mobile interactive gaming, where fast transmission of image and voice in dynamic environments is a prerequisite.Wireless networks that meet these expectations will have a hybrid character, consisting mainly of ad hoc networks with occasional access to infrastructures, in order to reachremote nodes or infrastructure-based servers. They will have tooperate completely automatically without t he interventiono f s ystem administrators, and therefore will haveto be self-organizing. Self-organization in this context implies the automatic finding of neighbor nodes, the creation of connections, the scheduling of transmissions and the determining of routes. This should be performed in a distributed manner sothat all nodes in t he network are able t o exchange information and reconfigure the network when nodes join or leave, or when radio linksare broken or established.A promising but, because of implementation difficulties, notw ell explored radio technology is UWB impulse radio. This technology has a lot of potentialf or high-* This researchi spart of the AIRLINK project funded by the Dutch Ministry of Economic Affairs under the Freeband Impulse Program.

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Ultra Wide Band (UWB) impulse radio, promises to be suitable for short-range, low-power, low cost and high data rate applications. While most UWB research is concentrating on the physical layer, little research has been published on the link layer. The fundamental operations in the link layer need to take into account the specifics of impulse radio and also the particular features of ad hoc networks. A novel self-organizing link layer protocol based on time hopping impulse radio, called SDD, was proposed by the authors. This protocol is a collisionfree mechanism that enables the devices to discover neighboring nodes and arrange the access to communication resources shared among the nodes. In this paper, some issues related to the self-organizing link layer based on UWB impulse radio are investigated and addressed. The SDD protocol is further developed and specified in detail. The simulations are carried out using GloMoSim simulation environment. An SDD module has been developed and embedded in the simulator. Results show that the SDD protocol can work properly and efficiently in a single-hop ad hoc network.