The Research Behind the Demonstration
A few years ago, the government mandated that all cellular service providers impiment a system to locate
a cell phone user in case of an emergency. Since then, there have been multiple systems launched which claim
the ability to locate a cellular phone user with variable levels of accuracy. However, many of these expensive systems
fail to locate users in highly obstructed areas, especially indoor environments. The Georgia Tech Propagation Group saw
this weakness as a challenge and developed a system for cellular location which maintains its accuracy in a highly obstructed
environment. This method is known as Relative Signal Strength Indication or RSSI. The RSSI method uses the cellular handset
as its own locator beacon. By reading the signal strengnth the cell phone sees at any point on the a map from each surrounding
cell phone tower, a computer can gather data which can be interperated into the users location. A simulation algorithm was devised
to approximate the multiple signal strengths a cell phone would see at any given position on the map. This simulation was
created by evaluating the laws of electromagnetic propagation in an obstructed environment. The computer can then compare
the recieved data to the simulation map, and find the best estimate of the users location. This method has produced results within 100 meters of the user over 60 percent of the time.
Click here for pictures taken
of the team collecting the data
The Demonstration Applet
The applet was created to graphically display the results which the RSSI system produced. A large amount of actual call
data was collected around the city of Atlanta, Georgia. This data was then compared to the simulation results of the same
area. The applet shows how close the algorithm's estimation of location is to a users actual location at any point on the
map. A number of different background layers are offered on the applet so the user can see the composite of all the simulation
data into one final result. For the best results in the applet, click close to the center of the map where Georgia Tech is located.
This area is where the majority of the actual call data was obtained, so the applets performence is most accurate there.
Click here to proceed to the demonstration