NTIA Report Describes Emission Tests for Jammer in Prison
Monday, June 18, 2018 | Comments

A National Telecommunications and Information Administration (NTIA) report describes emission spectrum and time domain measurements of a contraband wireless device microjammer operated temporarily in four commercial mobile radio service (CMRS) bands at a federal correctional institution (FCI) in Cumberland, Maryland. The four jammed CMRS bands were between 730 MHz and 2.155 GHz.

The microjammer targeted CMRS service indoors in a single medium-security prison cell. Spectrum measurements of the jammer emissions were performed at two places inside the targeted prison cell and at two nontargeted nearby locations outdoors. Jammer emission measurements were performed at each location with multiple measurement bandwidths and detectors across a frequency range of 300 MHz to 4.34 GHz.

At the measurement locations inside the prison cell, measured differences in incident power between when the jammer was on versus off showed that jammer incident power levels were much greater than that of the ambient CMRS power levels. For the outdoor locations where jamming was not intended, the jammer’s incident power was measurable at 100 feet from the building. However, outdoors the incident jammer power levels were lower than the ambient CMRS levels. This was because the jammer signal strength was lower outdoors than indoors, while the ambient CMRS signals were stronger outdoors than indoors.

Variations in jammer designs and emission characteristics, structural and attenuation characteristics of buildings, and site-dependent propagation factors would be expected to produce different results for different jammer installations at Cumberland FCI or other facilities. Analysis of the jammer’s potential for harmful interference to licensed radio services, if any, outside the targeted prison cell is beyond the scope of this report.

The report recommends that quantitative engineering criteria for jammer effectiveness against contraband wireless devices and for harmful interference to nontargeted CMRS receivers need to be developed if jamming technology is to be further developed for application in prison environments. Possible future aggregations of multiple jammer units, as would be required to cover entire prison facilities, would produce higher total levels of aggregate power than were measured for the one jammer device at Cumberland FCI.

Analysis of aggregate jammer emissions at prison facilities is beyond the scope of the report, as aggregate analysis would require detailed knowledge of specific facilities’ physical characteristics, the exact placement of individual jamming transmitters within such facilities, and the exact electronic characteristics of the jamming transmitters.

The full report is here.

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