Location Pattern Matching (LPM)

The wireless phone’s signal is received at various antenna sites equipped with special gear. The receivers send the caller’s voice call to the mobile switch, where sophisticated equipment analyzes the acoustic radio signal, and then compares it to a database of standard signal characteristics. These characteristics include signal reflections (multipath), echoes and other signal “anomalies”. According to U.S. Wireless, the only supplier of gear for this technique, when a computerized match is made, the location of the caller can be determined within the FCC’s requirements. The technique is effective in urban environments that include tall buildings and other obstructions, where other techniques might not succeed. The caller’s voice call and the latitude and longitude are then sent to the PSAP for use by the dispatcher. LPM works with any phone – digital, analog, TDMA, GSM, CDMA, etc.




Source: http://www.911dispatch.com/911/lpm.gif