"Cell phones, smuggled in by guards or family members and activated with hard-to-trace prepaid calling plans, are a lifeline for criminals and gang members to order hits, buy drugs and plan escape attempts from behind bars. Correction officials have identified the problem of cell phones in prisons as one of the toughest issues they face. The purpose of this project is to design, implement and test an effective system for the detection and localization of cellular phones in correctional facilities. The key purpose of the proposed effort is to mature the prototype Time Difference Of Arrival (TDOA) and signal strength detection for location system from laboratory to deployment in a correctional facility, and capable of detecting and locating cell phones in real time. Another key purpose is to explicitly use the known building floor plan in the algorithm that processes the received cell phone signals in to the likely location" (p. 10). Sections contained in this report are: introduction and background; hardware receiver system development; cell phone signal transmitter; signal processing and algorithm development; experiments and results; Tartarus—the resultant system of hardware and software; products; participants and other collaborating organizations; impact; changes and problems; budgetary information—system cost ranging from $10,000 to $25,000 depending on facility size; and conclusions and future work. The researchers "have developed a novel technique for locating cellphone use in an indoor environment. A hardware instrument and software package that implements the technique has been developed. A data base containing representative cell phone signals for indoor environments has been established" (p. 68).
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Time Difference of Arrival System for Cell Phone Localization in Correctional Facilities|Final Report
National Institute of Justice (NIJ) (Washington, DC)