Objective: This work presents the specification and components of a Building Accessibility Service (BASE) that is aimed for providing localization and route planning in unknown indoor environments. This new service will provide goal selection and route descriptions in order to reach the desired destination depending on user's profile. BASE will be most often used in places frequently visited, such as commercial centers, administration buildings, cultural and educative centers, hospitals, and so. One of the possible benefits of this service is to make easier the participation of people with disabilities in social life by increasing their autonomy.

Main content: This Service has several components: in one side, BASE must be created and maintained by a Services Provider; other side of BASE will be resident on the specific building, which must be equipped with some standard wireless communication devices; finally, users must carry with them a suitable communication and processing platform in order to use this service. In the Service Provider side, the Buildings Accessibility Service is based on a set of XML description files that contain all the information needed to access public or private buildings: floor maps, accessibility information, available routes and landmarks. In the building side, two different wireless networks are needed: a Wi-Fi network to connect to BASE through Internet; and a Sensor Network (SN) to provide indoor location. The SN is based on a set of wireless nodes equipped with ZigBee devices; RSSI (Received Signal Strength Indication) from fixed nodes are used to compute an approximate 3D location to reinforce user positioning inside buildings.

Results: A test environment is described using the proposed XML description. According to user's profile, BASE provides the best route between any two points in it. Actual tests have been made using a prototype of an Ambient Assisted Wheelchair (A2W), equipped with a set of computing and communication devices.

Conclusion: BASE is a powerful tool able to provide location and navigation services trough indoor environments. Although it has been tested with and advanced wheelchair prototype, this system can also be used by other kind of users, as its information may also be presented on the screen of a handheld device to provide the best route to users of standard wheelchairs or pedestrians.