Multi-path Fingerprinting (MP)

This technology uses features of the physical environment to locate mobile handsets. A wireless signal bounces off a variety of solid objects on the way to its destination (either a base station antenna or a handset), causing what’s called multipath interference. Essentially, the same signal is received multiple times due to the delay caused by bouncing off objects and taking longer paths to the destination. Multipath Fingerprinting takes advantage of this characteristic (which is normally a nuisance) to characterize signals that are received from certain locations. For instance, a base station can record what a handset signal looks like transmitted from a certain intersection of highways. A block away, the multipath signal “fingerprint” will look different, since the location of buildings, trees, and other obstructions has changed. To employ this system, an operator must send test units around to various locations so the base stations can record the fingerprints and create a database for comparison later on. Of course, if new construction occurs in an area the fingerprint will change and must be re-recorded.