More Information on ABng

Active Badge next generation (ABng) is a system which allows to locate people and equipment within a building. ABng is a new, CORBA-compliant implementation of the Active Badge System developed at Olivetti & Oracle Research Laboratory (ORL) in Cambridge, UK. Both ABng and ORL's Active Badge System use the same hardware infrastructure whose key components are infra-red sensors, installed in fixed positions within offices of the building, and infra-red emitters, called Active Badges, which are small devices worn by personnel or attached to equipment. Sensors are connected by a wired network which provides a communication path to the controlling device, called poller, and distributes low-voltage power. The poller is implemented as a PC or a workstation with a sensor control software active on it. An Active Badge periodically transmits an infra-red message containing a globally unique code (a badge identifier) using the defined data link layer protocol. Messages are received and queued by sensors. A poller periodically polls sensors and retrieves badge messages from sensor queues. Each badge message as well as an identifier of the sensor which received the message is forwarded to the software layer of the system. The software layer maintains a database that maps sensors to places in which sensors are installed and badges to users wearing these badges and to pieces of equipment which badges are attached to. Using these data the system can infer where users or pieces of equipment are currently located. The information about the current location of personnel and equipment can be provided to various applications, such as presentation tools which display location data or applications which use location data to control users' environment.

The software part of the original Active Badge System developed at ORL uses ANSAWare distributed programming environment. The ABng project aims at development of a new software layer that fulfils the following assumptions:

• is flexible and reconfigurable;
• separates the details of gathering of location data from the application layer;
• provides location data filtering;
• ensures privacy of location data and security;
• enables to build systems making a user's environment location-aware.

To satisfy the first requirement, ABng uses a modern component and object-oriented technology. The system is developed in object-oriented distributed programming environments: Orbix and OrbixWeb from Iona Technologies which are compliant with the widely accepted CORBA (Common Object Request Broker Architecture) standard for distributed systems. ABng is based on the object model in which all abstract and physical system elements (users, locations, sensors, badges, etc.) are represented as CORBA objects. Hence, for a typical installation consisting of about 100 badges and 100 sensors installed in 50 rooms, the ABng system consists of over 600 distributed CORBA objects. This makes ABng a good case study system for research on scalability of CORBA-based applications.

The system has a layered architecture which hides details of location data gathering. This makes it possible to replace a localisation method based on infra-red sensors and emitters by another one. In ABng location data are presented using abstract notions of location and locatable objects rather than in terms of sensors and badges. A location is a part of an environment obtained as a result of partition of the space according to an arbitrary, user-defined rule. Typically, an office space can be divided into buildings, floors, rooms, etc. A locatable is an object which can be observed by the system and whose location changes within the environment space can be monitored. A locatable can be a person or a piece of equipment, such as a computer, a printer or a book.

The basic ABng concept is View which is a collection of some location and locatable objects, i.e. it represents a part of the environment space and a subset of objects that can be localised within this part. The precision of localisation of view's locatables is equal to the size of locations belonging to the view. Within a system a number of view objects can exist, each of which can hold information concerning current locations of users of equipment belonging to different groups and provided at different levels of abstraction with different precision.

The concepts of locations, locatables and views are crucial for data filtering and protection of privacy of location data. Every application can individually decide which view and which locations or locatables contained in the view it is willing to observe. It can subscribe to interesting objects and, as a consequence, receive the required data related to these objects. With every view existing in the system a list of users who can access this view is associated. Thus only those users have access to location data as well to other attributes of locations and locatables contained in the view.

The ABng incorporates development of the Wonder Room - a location-aware users' environment. This environment consists of a number of applications which control various elements of the users' equipment. Examples of such applications are redirection of phone calls to the currently nearest phone or setting parameters of various home appliances, such as air-conditioning, TV sets, VCR-s, light, according to the preferences of users located in the neighbourhood of these appliances, period of time, etc. Such applications may be used for personalisation of user's equipment. Systems of this type are examples of, so called, ubiquitous computing.