Using radio-frequency pattern matching to nab terrorists
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High-accuracy indoor location in the toolkit
The scenarios above make the case for high-accuracy indoor location as part of the national security "toolkit." Countries at the forefront of adopting advanced surveillance techniques to protect the lives of citizens already have begun to deploy this capability. There are numerous location technologies in use today, but most do not provide the level of high accuracy that is required for national-security surveillance applications. Technologies that offer the highest accuracy can be categorized as handset or device-based, such as GPS, or network-based. And of the network-based options, the most widely deployed for surveillance and anti-terrorism is Radio Frequency Pattern Matching (RFPM).
RFPM is the only high-accuracy, software-based, scalable location solution that requires no additional hardware changes or additions to the mobile device or at the base stations. It compares mobile measurements (e.g., signal strengths, signal-to-interference ratios, and time delays) against a geo-referenced database of the mobile operator's radio environment. RFPM works extremely well in non-line-of-sight conditions, such as dense urban and indoor environments, where GPS-based solutions face severe challenges. Because it is independent of line-of-sight conditions, RFPM is highly reliable and is ideal for the mission-critical and life-safety applications that governments increasingly face.
RFPM technology is based on the observation that the radio environment varies from location to location, and each set of measured values will provide an RF signature that uniquely identifies a particular location. Because the control or overhead channels of a wireless network are broadcast at constant power, they provide a signature that is predictable and repeatable. The RFPM "location engine" consists of patented algorithms that estimate the location of the handset by comparing the time series of reported signal-strength measurements to the values stored in a patented database containing a detailed knowledge base of the surrounding terrain — its RF "fingerprint."
These algorithms employ a very complex set of statistical-pattern-matching techniques. RFPM provides a single time-tagged location estimate after a fixed time interval, or it can provide a continuous stream of time-tagged handset location estimates, if such information is required for tracking purposes. When changes are made to the terrain — for example, when a new building is erected or a new cellular tower is installed — the database is updated automatically.
With this state-of-the-art location-and-monitoring technology in place, governments can be a step ahead of tech-savvy terrorists. Once authorities adopt an indoor-location capability, they will be able to prevent terrorist acts and save lives.