X WORKSHOP DE AGENTES FÍSICOS, SEPTIEMBRE 2009, CÁCERES 17 Creating wireless coverage maps for mobile robot applications Joaquín López, Manuel Álvarez, Miguel Cacho, Enrique Paz and Diego Pérez Abstract— This paper describes a method to create wireless coverage maps for mobile robots. Most indoor mobile robot applications need some kind of wireless communication in order to receive commands and transmit information to users. However, robots that work in wide areas might not have coverage in all the working area. For example, surveillance robots that move in a building where wifi antennas do not cover all the area leaving some blind spots. Even in the case of autonomous robots that they do not need to be connected all the time because they can do tasks autonomously, the problem arise when one robot mission ends in one of these blind spots. If we do not provide mechanisms to avoid it, the robot will keep waiting for a new command that will never arrive since we can not connect to it. For these cases it comes handy a coverage map in order to avoid the blind spots if possible or to move to a highly coverage point in case the mission ends in a blind spot. In this paper we present different ways to create these wireless coverage maps according to the information that we have about the wireless system. Index Terms— mobile robot, WiFi, coverage map. I. INTRODUCTION URING the last years, the mobile robot industry has grown in investment, research and applications. Different degrees of autonomy are required in different applications but in most of them it is necessary to provide some kind of connection between the user and the robot. The information to be transferred from the user to the robot depends on the application and degree of autonomy. It can go from basic motion commands in robots with remote control to more general and abstract tasks in autonomous robots. On the other direction, most applications also need to transfer information from the robot to the user such as camera images and other on-board sensor data, reports while executing different tasks, etc. Therefore a communication system between user and robot is necessary in most of the applications. Furthermore, a wireless system is required in most of the case while the robots move on their working areas. Joaquín López, Manuel Álvarez, Miguel Cacho, Enrique Paz and Diego Pérez are with the Dep. Ingeniería de Sistemas y automática, University of Vigo, 36200 Vigo, Spain (phone: +34 986 812222; fax: +34 986814014; e- mail: joaquin@uvigo.es, su_manu2003@yahoo.es, (mcacho, epaz, dplosada)@uvigo.es Wireless Local Area Networks (WLANs) provide network services where it is difficult or too expensive to deploy a fixed infrastructure. WLANs can coexist with fixed infrastructure to provide mobility and flexibility to users. The primary WLAN standards are IEEE 802.11 [1]. The standard defines both physical and MAC layer protocols [2] and specifies the Received Signal Strength Indicator (RSSI) that is the measure of the RF energy received by the radio. The 802.11 protocol set, popularly known as Wi-Fi, includes wireless network standards that allow data transmission up to a theoretical 54 Mbps. Wireless communication systems cover areas that depend on parameters of the system selected and the environment where it is installed. For example, the Wi-Fi coverage in a building is going to depend on the devices used but also on the building construction materials, wall distribution, columns, etc. There are two different ways to approach this problem: • Make sure that we have full coverage on the area where the robots can move. This is, remove the coverage blind spots. • Provide the robots with mechanisms to deal with the blind spots. Most of the applications use the first approach providing coverage over the complete area where the robots are going to work. However, we address here the second problem for the following reasons: • We do not want to modify the building facilities. Our goal is to bring the robots and use the communication system already installed. • In some cases developing a system to provide full coverage can be expensive. • It is very difficult to obtain an indoor RF propagation model wave travels to make sure there are not dead spots where no signal can be received. • Even in the case we have full communication coverage, the malfunctioning of an access point might jeopardize the mobile robot application. Several researchers have already addressed the task to create Wireless coverage maps for outdoors [3][4] and also indoors [5][6]. However, since their purpose was not a mobile robot application, they focus their research in using D