TULIP - A Location Services Module (LSM) Prototype

Right information, to the right place, for the right object, at the right time

Basic Idea - Vision of deployment

In mobile computing, location becomes a fundamental contextual parameter in many important user and system applications. The ability to automatically obtain the location of a user or device in a wireless networked environment is stimulating the development of many new applications such as tour-guide systems, object tracking inventory management, healthcare, area monitoring for and digital shopping assistants. By including location as a key part of the users context, the systems can determine spatial locality relationships, provide directional guidance and deliver locally-relevant information. It becomes possible to automatically determine answers to queries of the form: Where am I?, Where are you?, What objects are near to me? The E911 requirements (by the U. S. Federal Communications Commission) in which cellular telephone carriers are required to implement a system for location determination of a wireless telephone that is used to dial an emergency 911 call, to a specified accuracy, is one prominent example of a location-aware service [ref E911].

There are many methods of automatically determining the location of an object. These methods range from Global Positioning System (GPS)- solutions, acoustic, infrared or radio-frequency sensors to inertial navigation systems. Each method has advantages and disadvantages in various environments (e.g., indoors, outdoors), yielding differences in metrics such as accuracy, repeatability, computational complexity, power consumption ease of use, cost and infrastructure requirements. In addition, different methods have advantages or disadvantages in supporting requirements for client privacy and control of location information. Since there is no one technology that can address all environments and requirements, it is likely that multiple determination methods will be needed to support most location aware applications.

A particular location determination method may or may not depend on the communications infrastructure as an integral part. Some location-aware applications can be fully implemented in an isolated client device, such as a GPS navigation device. However, many others use the communication network to transport location information for determination or for interaction with the remote location-aware applications. In many applications of interest, ease of use and deployment are more important than high degrees of accuracy. For example, we have developed a basic location-determination method, called mini-beacons, that operate indoors and can determine room-level accuracy. Mini-beacons are small devices based on the IEEE 802.11b Access Point protocol that are placed in areas of interest. Clients use the RF signal strength reported from a standard IEEE 802.11b wireless LAN adapter to identify the closest beacon, and thus the location.

In the current world wide web environment, user-oriented applications are now being offered as web services using standard interfaces, yielding advantages in universal access from many types of devices through now common-place Internet protocols. Location-based applications can also benefit from being formulated as web services. At the same time, many important network system services, such as service discovery or service access can themselves be extended to have a spatial aspect (e.g., Find the closest printer) by incorporating location data.

In order to address two important issues: 1) providing a standard, secure interface to location information, and 2) concurrently and transparently handling multiple location determination methods, we have designed and developed the Location Services Module (LSM) [ref Aero paper]. The LSM is a middleware solution that produces location information locally on a client device and makes this information available to other applications as a web service. The LSM also supports multiple technologies such as GPS, RF signal Strength, and IR, providing the location information in a common standard format.

An architecture for location-aware services has been designed and several example applications have been developed to demonstrate the effectiveness of the LSM as middleware. These are included as part of an office guide system, InfoGuide, that provides information based on the clients location. The InfoGuide system consists of several components: 1) client devices equipped with a browser interface, wireless communications and one or more location determination methods, 2) The Time-User-Location Information Processing (TULIP) server that provides web pages and other location-based information using the clients position, and 3) the Tracking server that maintains and displays the location of all registered clients.