0 Using a Meeting Channel and Relay Nodes to Interconnect Mobile Robots Nassima Hadid, Alexandre Guitton and Michel Misson LIMOS CNRS / Clermont Université, Campus des Cézeaux, 63 173 Aubiere Cedex France 1. Introduction Mobile robots are increasingly used in industrial applications (generally in order to convey merchandises), in healthcare applications (for example, to transport patients or medicines) or in domotic applications (for instance, to sweep a floor). These robots are often mounted with several sensors and actuators, in order to carry out their tasks (e.g., grabbing an object of interest, and bringing it a destination without colliding with obstacles). To reduce the complexity and weight of the wiring of all these sensors and actuators, these devices can be equipped with wireless capability. A central entity, called the central unit, is usually in charge of collecting the data from the sensors, integrating part of the data in a models, computing a behavioral response and operating the actuators accordingly. Another entity, called the coordinator, is in charge of managing the wireless entities, retrieving data from sensors and sending orders to actuators. The same device can be simultaneously the central unit and the coordinator. In the following, the wireless communications between sensors, actuators and coordinator are called intra-robot communications. Real applications often require the collaboration of mobile robots in order to perform required tasks. For instance, when they are used in airports to transport luggage, mobile robots can cooperate to avoid colliding with each other. In search and rescue operations, mobile robots can inform their neighbors that an area has already been explored (Ferranti & Trigoni, 2008). Robots can also follow tracks on the floor (Hogg et al., 2002) or monitor an area collaboratively (Lambrou & Panayiotou, 2009). An allegorical example is shown on Fig. 1, where the waiter robot Dro has to collaborate with the waitress robot Ide in order to serve hot coffee to customers. These communications used for collaborations are called inter-robots communications. The design of a network architecture that allows mobile robots to cooperate efficiently, without negatively impacting the performance of each intra-robot communication, is a challenging issue, and is the aim of this chapter. The remainder of the chapter is the following. In Section 2, we introduce a multi-channel approach where intra-robot communications are performed on a robot-specific channel, and inter-robot communications are performed on a common meeting channel. In this way, mobile robots can communicate without impacting intra-robot communications. In Section 3, we discuss the protocols that allow mobile robots to communicate directly, when they are 15