|This article does not cite any references or sources. (July 2011)|
Radio fingerprinting is a process that identifies a cellular phone or any other radio transmitter by the unique "fingerprint" that characterizes its signal transmission. An electronic fingerprint makes it possible to identify a wireless device by its unique radio transmission characteristics. Radio fingerprinting is commonly used by cellular operators to prevent cloning of cell phones. A cloned cell phone will have a same numeric equipment identity but a different radio fingerprint.
Essentially, each transmitter (cell phones are just one type of radio transmitter) has unique rise time signature when first keyed caused by the slight variations of component values during manufacture. Once the rise time signature is captured and assigned to a callsign, the use of a different transmitter using the same callsign is easily detected. Such systems are used in military signals intelligence and by radio regulatory agencies such as the U.S. Federal Communications Commission (FCC) for identifying illegal transmitters. They are also used for assessing usage for billing purposes in Subscriber Mobile Radio (SMR) systems.