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UWB Enhanced Time Difference of Arrival System, Summary

NCJ Number
Date Published
8 pages
This is the summary of the final report on a project whose objective was to design, implement, and test a system for the detection and location of cell phones in correctional facilities.
Such a system is needed because cell phones are being smuggled into prisons by guards or family members and activated with hard-to-trace prepaid calling plans. This enables inmates to order "hits," buy drugs, and plan escapes while in prison. The researchers are developing a prototype Time Difference of Arrival (TDOA) emitter detection and location system. Under testing at Lawrenceville Correctional Center, the system has proven to detect and locate cell phones in real time. The threshold at which the system reliably triggered cell-phone use was at SNR of 20dB SNR; below that there would be either false positive or false negatives. The system triggered on any signal in the 824-849MHz channel, a desirable feature for the final system; however this made testing difficult due to signals from other cell phones. There was cross-talk between the four channels, particularly between adjacent received boards. Changes have remedied each of these issues, and preliminary tests have shown marked improvement in each area. During the project's first year, a channel sounding test was performed at a prison. The test conducted channel sounding measurements across the United States' three popular cell phone frequency bands (GSM, WCDMA, and PCS). The experiments were conducted based on physical layer features, specifically, transmit bandwidth, frame format, modulation scheme, and camp-on procedure. This report also describes the software/scripts used, frequency bands, the test set-up, and the test run. This report also describes the hardware design, cell-phone receiving hardware, and the simulation of CDMA2000 transmission. The determination of time difference and cell-phone location are explained.

Date Published: January 1, 2013