This paper focuses on node placement strategy, communication protocols and hardware implementation of a robust mobile multi-hop network. As part of the GUARDIANS project a main disaster scenario of a large industrial warehouse on fire is assumed. In this scenario, black smoke may fill large space of the warehouse which makes it very difficult for the firefighters to locate themselves and orientate in the building. In our approach a multi-hop ad-hoc network communication system is able to provide a robust communication system. Focus of this paper is the distribution of robots to guaranteeing robust communication between the base station outside the scenario area and the fire fighter inside the building. Concerning the first point, the presence of smoke and the indoor nature of our scenario prevent localization using camera and GPS respectively. Therefore the performance and accuracy of other sensors were tested in order to examine their usability and reliability in such a scenario, like ultra-sound, laser and radio signaling. The second point is the evaluation of routing protocols and the development of a mobile communication gateway which is optimized for the mobile usage and therefore supports different techniques for energy saving. Its characteristic was tested in different scenarios like a complex building and a parking garage.

Mobile ad-hoc networks (MANETs) are communication networks that do not rely on fixed, preinstalled communication devices like base stations or predefined communication cells. MANETs are wireless networks consisting of mobile nodes which are characterized by their decentralized organization and the potentially high dynamics of the network structure. Therefore, MANETs are ideally suitable for applications with multi-robot systems. One of the most promising applications of a multi-robot system is to assist humans in urban search and rescue (USAR) scenarios in the aftermath of natural or man-made disasters. We are focusing on an ad-hoc network communication system with the mobile robots being communication nodes offering a robust communication infrastructure. Main disaster scenario covered by our system is a large industrial warehouse in fire, described in the GUARDIANS project funded by the European Union. In this scenario, black smoke may fill large space of the warehouse that makes it very difficult for the firefighters to orientate themselves in the building which in turn will usually limit the action space of the firefighters. In order to increase the coverage area of the fire fighters the ad-hoc network has to provide position data to support localization of the mobile robots and humans, which might be of great importance to guide the humans and robots to specific targets and locations or to quickly exit the search area. In our proposed approach a cell-based network with master nodes in each cell forms the basic structure of the network. Some nodes formed by speciallyequipped robots act as beacons to uniformly span the network. These robots have a role as reference points when positioning other mobile robots or humans and at the same time form the infrastructure to support communication all over the search area. A combination of distance and radio signal quality measurements as well as dedicated swarming behaviors of the robots are capable of maintaining suitable distribution of the robots even in the presence of walls that obstruct the radio signals. Communications standards considered for the ad-hoc network are Wireless LAN, Bluetooth and QigBee. All are integrated on a miniature robot for real experiments. The features of the network are studied analytically, in simulations as well as in experiments to verify the results. Furthermore, frequency and power managements are also taken into consideration to ensure robustness of communication in the network.

The increasing capabilities of robot systems enable new fields of practical applica- tions for individual robots as well as multi-robot systems. But for some applica- tion scenarios like a fire or earthquake disaster current robots are still too limited to act fully autonomously in the disaster area. To overcome these limitations we consider a heterogeneous team of humans and robots complementing each other. Core application considered in this paper is a large burning warehouse with smoke making it difficult for fire fighters to search the building and to orientate them- selves inside the warehouse. Therefore, an assisting team of robots is surrounding the fire fighters searching the proximity, providing orientation data, and establish- ing a wireless communication infrastructure on a basis of a mobile ad-hoc net- work. The adaptation of the robots is achieved by applying principles of self- optimization on different levels of the human-robot system. In this paper, we are considering self-optimization inside an individual robot to optimize its behaviour, within a group of robots, and in the entire system compris- ing of robots and humans. The focus of the optimization is the distribution of ro- bots by applying swarming behaviour for forming a mobile ad-hoc communica- tion network and performing map building.