Global Positioning System (GPS) Technology allows precise determination of location, velocity, direction, and time. The price of GPS receivers is falling rapidly and the applications are growing. PCMCIA receivers that can be connected to any notebook personal computers are available for /$300-400 to end consumers.
The main goal of this study was to survey current applications of GPS to distributed systems and networks. While GPS is appearing in the computer magazines very often and while many computer companies have announced GPS related efforts, most such efforts are in providing navigational guidance to drivers. Digitized city maps along with a GPS sensor on a mobile computer provide directions to drivers. A number of consortiums have been formed by companies such as IBM, Apple, Toshiba, Sony, and others.
Currently, applications of GPS for distributed computation and networking are limited to measuring delays in Wolter and Golderman's DA-30 network analyzers and in clock synchronization in synchronous optical networks (SONET) used in telecommunication networks.
We have identified twenty new applications of GPS for distributed computing and networking. These applications include circuit switching using synchronized clocks, synchronous slotted systems, clock synchronization in distributed systems, database synchronization, connectionless real-time communication, one-way delay, delay based routing, time to live, resource location, location adaptive protocols, home vs office vs car, electronic fence, handoffs in wireless networks, prescheduled handoffs based on velocity and direction, adaptive transmission power control algorithms, directional antennas, temporary cell partitioning for congestion avoidance, peer-to-peer routing with limited range receivers, email delivery based on geographic location, distributed robot control and navigation, and equipment location marking for maintenance crew.
There two main obstacles to applications of GPS. First is that GPS antennas must point to open sky. They cannot be used directly inside a building. Unless this is avoided by new antenna designs or by rebroadcasting GPS data inside a building, the use of GPS techniques is limited to improving the performance of distributed systems rather than proper operation. This is similar to cache memories in computer systems. Systems can operate without cache but perform better with cache. The second obstacle is the psudo-random noise introduced in the GPS signals by the defense department to disallow other governments from using the full precision of GPS. This is called selective availability. Fortunately, this can be easily overcome by differential GPS techniques.
Detailed lists of GPS products, current applications, addresses of manufacturers, and sources for further information are included in this report.
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