Prison Phone Justice

601 Pennsylvania Ave, NW
North Building, Suite 800
Washington DC, 20004
February 2, 2018
VIA ELECTRONIC FILING
Marlene H. Dortch, Secretary
Federal Communications Commission
445 12th Street, SW
Washington, DC 20554
Re:

Promoting Technical Solutions to Combat Contraband Wireless Device Use in
Correctional Facilities, GN Docket No. 13-111
Written Ex Parte Presentation

Dear Ms. Dortch:
T-Mobile USA, Inc. (“T-Mobile”), pursuant to Section 1.1206(b) of the Commission’s
rules, hereby submits the attached study by Roberson and Associates, LLC comparing Managed
Access Systems (“MAS”) and precision jamming systems as potential solutions to prevent
contraband phone use in correctional facilities. The study provides an overview of MAS and
jamming solutions examining both technical and cost considerations. The paper finds that the
cost to deploy and operate the two solutions is roughly equivalent, with the cost for a MAS being
less than a jammer solution in larger prisons and the jammer solution being slightly less than an
MAS solution for smaller prisons. However, the study also details a number of detrimental
impacts of a jammer solution compared to an MAS solution, such as blocking legitimate use of
wireless devices, including use for E911 and FirstNet, jamming other important uses, including
GPS, Bluetooth and Wi-Fi, and creating a significant potential for interference with use of
wireless devices by the general public in surrounding areas. Based on the findings of the study,
any cost/benefit analysis would necessarily have to conclude that a jamming solution is not an
appropriate approach to combating contraband devices in prisons given the availability of
comparably priced, effective solutions that do not include the negative societal impacts
associated with jammers.
1

The study compares MAS and precision jamming solutions, with particular focus on their
coverage footprint requirements, methods of service denial, and impact on local commercial
wireless networks. The document finds that there is little functional difference between network
elements employed within the two systems, except for the core network which is applicable to
MAS systems only. It also highlights that, although both solutions prevent the use of contraband
1

47 C.F.R. § 1.1206.

February 2, 2018
Page 2

devices within correctional facilities, MAS allows officials to permit the operation of authorized
devices within correctional facilities, whereas jamming solutions prevent the operation of all
devices for all purposes, regardless of legitimacy. Furthermore, the report identifies additional
operational benefits available for MAS, e.g., data collection, that are not available with a
jamming deployment.
The study then analyzes the relative financial costs associated with these two solutions
for small, medium, and large correctional facilities. Understanding that correctional institutions
vary widely in function and age, and related to this and other factors, the design and building
materials are quite diverse. The study finds generally that the comparative costs of MAS and
precision jamming systems are similar and that the larger and more complex the facility, the
higher the relative installation and operation cost is predicted to be for a precision jamming
system verses the equivalent costs of a MAS.
Finally, given the importance of 911 calling and the increasing reliance of first
responders on commercial networks (e.g., FirstNet), the study concludes that the impact of
potential solutions on these types of communications should be an important part of any analysis.
If you have any questions, please contact the undersigned.
Respectfully submitted,
/s/ Steve Sharkey
Steve Sharkey
Chief Engineering and Technology Policy,
Federal Regulatory

cc:

Charles Mathias
Mary Claire York
Roger Noel
Lloyd Coward
Meaghan Ryan

C ONTRABAND P HONE S OLUTION
A SSESSMENTS :
C OMPARISON OF THE U SE OF M ANAGED
A CCESS V . P RECISION J AMMING S YSTEMS IN
C ORRECTIONAL F ACILITIES
B. A LBERTH , M. B IRCHLER , N. N ATARAJAN , B.
P AYNE AND D. R OBERSON
2 F EBRUARY 2018
V 5.0

Table of Contents:
1	 EXECUTIVE SUMMARY .................................................................................................3	
2	 INTRODUCTION ...............................................................................................................4	
2.1	 BACKGROUND ...................................................................................................................4	
2.2	 THE CORRECTIONAL FACILITY ENVIRONMENT ..............................................................4	
2.3	 THE RADIO FREQUENCY (R.F.) ENVIRONMENT ...............................................................5	
2.3.1	 SPECTRUM AND TECHNOLOGIES ......................................................................................5	
2.3.2	 R.F. PROPAGATION ISSUES ..............................................................................................6	
3	 SOLUTION ASSESSMENTS .............................................................................................6	
3.1	 MANAGED ACCESS SYSTEMS ............................................................................................7	
3.1.1	 GENERAL CONSIDERATIONS ............................................................................................7	
3.1.1.1	 Coverage Footprint Requirements .................................................................................7	
3.1.1.2	 Denial of Service to Unauthorized Devices ...................................................................7	
3.1.1.3	 Interaction with Local Commercial Wireless Networks .................................................8	
3.1.2	 PRACTICAL EXPERIENCE..................................................................................................8	
3.2	 PRECISION JAMMING SYSTEMS ........................................................................................9	
3.2.1	 GENERAL CONSIDERATIONS .......................................................................................... 10	
3.2.1.1	 Coverage Footprint Requirements ............................................................................... 10	
3.2.1.2	 Denial of Service to All Devices ................................................................................. 10	
3.2.1.3	 Degradation of Local Commercial Wireless Networks ................................................ 10	
3.2.2	 PRACTICAL EXPERIENCE................................................................................................ 11	
3.2.2.1	 NTIA Testing ............................................................................................................. 11	
3.2.2.2	 Other Countries .......................................................................................................... 12	
4	 COST COMPARISON...................................................................................................... 14	
4.1	 CORRECTIONAL FACILITY SIZES AND CHARACTERISTICS ............................................ 14	
4.2	 COST ASSESSMENTS ........................................................................................................ 15	
4.2.1	 COMMON ELEMENTS ..................................................................................................... 15	

Roberson and Associates, LLC ®

4.2.2	 ELEMENT DIFFERENTIATION .......................................................................................... 15	
4.2.2.1	 System Design and Deployment ................................................................................. 15	
4.2.2.2	 Head-End Device........................................................................................................ 16	
4.2.2.3	 Distribution System .................................................................................................... 17	
4.2.2.4	 Core Network (MAS Only)......................................................................................... 18	
4.2.2.5	 Management System................................................................................................... 18	
4.2.2.6	 Operational Expenses ................................................................................................. 20	
4.2.3	 COST / PERFORMANCE TRADEOFFS ................................................................................ 20	
5	 CONCLUSIONS ............................................................................................................... 22	
5.1	 SUMMARY ....................................................................................................................... 22	
5.2	 CONCLUSION ................................................................................................................... 23	
6	 REFERENCES.................................................................................................................. 25	

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1 E XECUTIVE S UMMARY
This paper examines the use of Managed Access Systems (MAS) and precision jamming systems
as alternative methods of effectuating denial of service to contraband devices within correctional
institutions. A description of example correctional facilities is provided, which includes the highly
complex radio frequency (R.F.) environments, multiple cellular spectrum bands, and several
technologies that must be addressed. The Managed Access and precision jamming systems are then
described with particular focus given to their R.F. coverage footprint requirements, methods of
service denial, and impact on local commercial wireless networks. Core networking connectivity
and forensic features are also described.
The concept of precision jamming is introduced as it is required that jamming must not cause any
degradation in service to commercial wireless networks outside of the prison boundary. Jammer
denial of cellular service inside the prison boundary may also become unacceptable due to the
increasing reliance of public safety and first responder service on commercial wireless networks
(i.e., FirstNet). That is, with the introduction of FirstNet, First Responder communications services
will be carried over commercial wireless networks. Thus, it is imperative that R.F. jamming
systems not degrade these critical communications.
It should also be noted that, regardless of the ability to contain jamming within the prison boundary,
jamming is an “all or nothing” approach. It is not possible to limit jamming to contraband devices
while allowing use of legitimate devices. Instead all devices would be jammed, including those
attempting to reach 911 services in an emergency.
It is found that for each system there are common R.F. engineering methods and techniques used
to address these focus areas. It is also found that there is very little functional differentiation
between network elements employed within the two systems, except for the core network which is
applicable to MAS systems only. Small, medium, and large sized facilities are defined and relative
costs are analyzed for all three cases.
The summary of our results is that in a large facility, precision jamming is expected to be costlier
than a MAS due to higher system management and monitoring costs, as well as higher R.F.
jamming head-end costs. In a medium facility, the precision jamming system’s higher management
and head-end costs are expected to be partially offset by the MAS core network costs. In a small
facility, the additional cost of the MAS core network may make it slightly more costly.
Overall there is very little difference in capital and operational costs between Managed Access and
precision jamming systems. Operationally however there is an enormous difference in that a
jamming system is effectively a very “blunt instrument” approach to the problem while the MAS
approach is more of a “versatile tool” that has numerous other diagnostic benefits enabling prison
officials to gain a valuable perspective on the wireless activity in the prison and to use this
information as appropriate to detect and deter not only wireless misuse, but potentially other
contraband and general criminal activities.

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2 I NTRODUCTION
2.1 Background
Unauthorized use of contraband wireless devices in correctional facilities has led a variety of
stakeholders to call for the investigation and implementation of a number of possible solutions, two
of which are Managed Access Systems (MAS) and precision jamming. For several years, MAS
solutions that deny service to contraband devices have been successfully deployed in correctional
facilities. On the other hand, precise jamming systems that deny service to contraband devices
have not been deployed in the U.S. for a variety of reasons [1].
One question that arises in this proceeding is the relative complexity and costs of jamming-based
systems as compared to MAS. This paper examines this question. Per the subsequent sections, it
is found that the complexity of precision jamming is comparable to that of Managed Access.
Furthermore, precision jamming may prove even more technically challenging than a MAS because
of the potential harmful impact on other wireless communications networks.

2.2 The Correctional Facility Environment
Correctional facilities, both publicly and privately managed, vary widely with regard to size,
architectural design, security level and location to name just a few factors. Due to these and other
sources of variation, R.F. systems targeted on these facilities will require custom design,
installation, maintenance and management. The following figure provides information for two
relevant facilities, those being the Federal Correctional Institution, Cumberland Maryland and the
Dallas County Detention Center, Dallas, Texas.

Figure 1.

Federal Correctional Institution (Left) and Dallas County Detention Center (Right)

Note that whereas the Maryland facility is surrounded by a primarily rural environment, the Texas
facility is embedded within an urban environment.
Figure 2 shows selected locations within the Maryland facility.

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Figure 2.

Federal Correctional Institution, Cumberland Maryland: Interior Views

These figures illustrate numerous correctional institutional features, including:
•

Building(s) within a well-defined security perimeter (Figure 1)

•

Highly variable environments directly outside of the security perimeter (Figure 1)

•

Staff areas (Figure 2, Left)

•

Multiple small cells with metal doors and thick walls (Figure 2, Center)
Note that there will be significant variation in cell construction and layout as a function of
prisoner security level.

•

Common areas used by prisoners and staff (Figure 2, Right).

These features create context for the following solution assessments.

2.3 The Radio Frequency (R.F.) Environment
Any contraband phone service denial system must operate in a highly complex R.F. environment.
The following two sections discuss two primary areas that give rise to this complexity and are
applicable to both solutions under consideration.

2.3.1 Spectrum and Technologies
Cellular systems operate in multiple spectrum bands using numerous generations of technology.
Cellular spectrum bands include allocations at: 600, 700, 850, 1700, 1900, 2100, 2300 and 2500
MHz. Cellular technologies in use today are 2G (GSM, CDMA), 3G (UMTS) and 4G (LTE). Each
of these technologies uses a specific channel structure. For example, GSM uses 200 kHz Frequency
Division Duplexing (FDD, separate uplink and downlink channels), while LTE uses multiple
channel bandwidths (i.e., 1.4, 3, 5, 10, 15 and 20 MHz) and both FDD and Time Division Duplexing
(TDD), which utilizes a common uplink and downlink channel.
Cellular phones also generally include non-cellular technologies such as Wi-Fi and Bluetooth. In
addition, satellite phones (e.g., Iridium and Globalstar) may provide wireless access to services
from certain areas within the walls of a prison complex. These technologies can be used to access
wireless services without need for communication with cellular base stations.
Currently, fifth generation (5G) cellular technology is in the early stages of definition and
standardization. 5G technologies will utilize additional spectrum bands with their own specific
propagation characteristics and channel structures. Thus, the current spectrum framework is
already complex and will become more so with the deployment of next generation systems.

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A prison precision jamming system must prevent all of the above cellular and non-cellular
communications with no impact to other mission critical systems such as public safety. Therefore,
high performance filtering will be necessary to achieve this requirement.
This spectrum complexity and evolution creates significant challenges when designing and
managing a precision jamming system. That is, the precision delivery of jamming signals to new
spectrum bands/channels and for new systems may require costly upgrades to jamming devices and
systems. For example, a recent article on jamming systems in India noted that existing prison
jamming systems didn’t work on newer wireless technologies that are used for 3G and 4G
communications [2].
Of course, MAS systems will also require upgrades as new cellular technologies roll-out. However,
a MAS solution is designed to enable efficient evolution since they are constructed using cellular
technology platforms and therefore, may not require as extensive upgrades as precision jamming
systems would.

2.3.2 R.F. Propagation Issues
Although R.F. propagation has been measured, studied and modeled for generations, actual
behavior in specific cases remains difficult to accurately predict. Areas of uncertainty include
equipment (e.g., antenna patterns, non-linarites, and filtering), propagation modes (e.g., diffraction,
reflection, absorption, and scattering) and environment (e.g., building walls, windows, foliage, and
terrain). Therefore, although a powerful body of modeling science is at the disposal of R.F. system
designers, the need remains for substantial testing and validation. Propagation also varies with
frequency. As new spectrum bands are deployed with commercial cellular service the propagation
in the new band needs to be measured and modeled.
Outside of laboratory conditions, it is virtually impossible to constrain the extent of R.F. signal
propagation to well-defined geographic areas. Generally, the power of propagating R.F. signals
falls off with distance from the transmitter. The rate of this power reduction with distance depends
on many factors as referenced above. As a consequence, when designing R.F denial of service
systems such as precision jamming, there is the high likelihood that the R.F. signals will also
propagate into undesired areas.
The difficulties associated with controlling R.F. propagation beyond an outdoor perimeter are well
understood by the wireless engineering community. Precision coverage control requires
sophisticated design and modeling capabilities, directional antennas, complex deployments and
active, continuous validation, testing and management. This issue is of particular sensitivity for
jamming systems, as any R.F. energy leakage beyond the correctional facility perimeter can
significantly degrade or outright block legitimate wireless communication by the general public.

3 S OLUTION A SSESSMENTS
This paper is not intended to provide a comprehensive overview of all potential contraband phone
service denial solutions. Rather, it provides focused assessments for two solutions of current
interest, those being Managed Access and precision jamming systems. As has been discussed
above, precision jamming systems have not been deployed in the U.S. and hence, the following
discussion of jamming systems is generally theoretical in nature.

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3.1 Managed Access Systems
MAS systems use commercial wireless spectrum to capture and prevent contraband phones from
being used inside a prison facility and require wireless carrier consent, including spectrum leases,
prior to deployment. In other words, managed access technology is used to establish a Radio Access
Network (RAN) that serves as a multi-carrier, multi-band cellular network within the prison
facility.

3.1.1 General Considerations
A MAS appears to its users as a standard operating commercial wireless network. Figure 3 shows
a conceptual overview of a MAS. The region inside the red ellipse represents the area of a prison
facility from which legitimate and undesired calls may be attempted to one or more commercial
networks. The figure shows an example with two commercial networks, labeled Network 1 and
Network 2. Note that inside the prison boundary two of the three cell phones are authorized to
communicate while the third is unauthorized. Therefore, the unauthorized phone must be blocked.
Finally, the cell phone outside the prison boundary must be able to communicate without
impairment by the nearby MAS system.

Figure 3.

Conceptual Managed Access System

3.1.1.1 Coverage Footprint Requirements
A key MAS requirement is that the coverage footprint must be very near to 100% for the solution
to be effective. Thus, if the system design is only 99% effective, there could be significant areas
in which prisoners could still make illegal calls. A MAS must coexist with the commercial
networks in the areas immediately surrounding the prison facility. Successful MAS deployments
require accurate control of the footprint of the radio access coverage through a variety of techniques
(e.g., architecture design, power control, distributed antennas, directional antennas, sophisticated
repeaters, and other radio parameters and technologies) such that the commercial coverage is not
impacted outside of the prison facility. An effective MAS is adaptable to the prison facility, whether
it be urban or rural, and the local commercial radio environment.

3.1.1.2 Denial of Service to Unauthorized Devices
A Managed Access network is designed to present the “dominant” network signal within its limited
authorized RAN coverage area (see Figure 3). The MAS signal is intended to overwhelm signals
from nearby commercial network base sites within the boundaries of the correctional institute. A
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MAS appears as an extension of local carriers’ networks and intercepts (or captures) cell phone
signals as calls are attempted from within a prison facility.
Once captured, unique identifying information is compared against a list of known authorized
devices. Only transmissions from devices that are in the authorized list will be redirected to the
commercial system and allowed to connect, while the call attempts from phones not on the
authorized list are held by the MAS system, effectively preventing them from reaching commercial
cellular networks to complete their attempted calls.
SMS and data calls are managed the same way, devices on the authorized list are permitted to
send/receive SMS messages and data. Unknown phones (i.e., those not on the authorized list) are
prevented from accessing the commercial networks and thus cannot surf the web, make/receive
calls or send/receive SMS.
A MAS can also permit completion of 911 calls even if the cell phone is not on the authorized list.
Thus, a MAS provides the appropriate balance between the control of contraband devices and
permitting approved users to continue the use their device in the same restricted coverage area of a
prison facility while still allowing emergency calls to complete properly.
For a MAS system design, as long as any R.F. signal leakage beyond the correctional facility
perimeter is lower in power than that provided by the external cellular network, there will be
minimal chance of service degradation to the general public. This condition can be ensured through
proper design and deployment of the MAS system.

3.1.1.3 Interaction with Local Commercial Wireless Networks
Whereas a jamming system seeks to prevent service to all users in a prison facility, a MAS works
by selectively blocking a group of users from using wireless networks to communicate. A welldesigned MAS system can eliminate the potential for interference to users outside a prison facility
or in adjacent bands. The cost of a MAS is a function of the size and complexity of a prison site as
well as its location (e.g., urban, suburban and rural).

3.1.2 Practical Experience
In a specific urban deployment, wireless service denial was required in a tightly defined area, so
coverage was implemented with a Distributed Antenna System (DAS) [3]. The following list
contains core design tasks necessary for practical implementation of a DAS-based MAS:
1. Fine-tuning the radio signal footprint - prison facilities are constructed using materials that
block and reflect signals in very unpredictable ways resulting in potential MAS network
coverage “holes”.
2. Refining the authorized device list – create and update the list to keep it up-to-date.
3. Hardening MAS hardware and associated infrastructure against environmental factors as
well as to secure against destructive actions by inmates.
4. Addressing location-specific unique characteristics including facility-specific physical
constraints and characteristics of the local commercial wireless network environment.
5. Ensure that the contraband phone cannot gain access to and service from the local
commercial wireless network.

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3.2 Precision Jamming Systems
Interest in the use of “jammers” has been expressed by some correctional organizations due to the
assumption of lower cost and complexity (see [4], [5], [6]). However, these assumptions must be
assessed with respect to the necessary system requirements, wireless engineering realities and
legal/regulatory barriers. A “jamming device” (as opposed to a “jamming system,” which is the
topic of this paper) transmits on the R.F. channels used by cellular base stations to disable the
communication link with their associated cell phones. Note that a “jamming system” uses
“jamming devices” as a key component in an overall system solution.
Our scope excludes readily available, inexpensive, commercial off the shelf (COTS) jammers such
as the example shown in Figure 4.

Figure 4.

Example COTS Jammer

This is because use of COTS jammers will create uncontrolled outputs, leading to unintended
consequences such as significant disruption to other wireless systems. The use of cheap, COTS
jammers distributed throughout a facility cannot provide complete coverage without causing
debilitating interference to wireless systems inside and outside of the facility’s security perimeter.
That is, the uncontrolled R.F. emission of these devices and lack of proper system design will allow
R.F. energy to “leak out” into the surrounding environment, negatively impacting many other
wireless systems, including mission critical wireless systems inside and commercial systems
outside the facility. As a specific example, Monstrol 10, featured in Figure 4, jams not only cellular
channels, but also GPS, Wi-Fi, Bluetooth, Lojack, etc. A COTS jammer could also disrupt mission
critical wireless communication within the prison.
Likewise, small jammers intended to provide very localized disruption will not be effective at
blocking use of contraband devices. As discussed above, the complex structural and RF prison
environment would mean that localized jammers could be easily avoided by a prisoner moving
away from the device – likely only a few feet or around a corner. Accordingly, such localized
jammers are not considered because they do not address the underlying concern.
Therefore, we here compare solutions that satisfy the requirements of all stakeholders interested in
combating illicit cell phone usage without harming the legitimate interests of any stakeholder
community (both the corrections industry and the mobile carrier industry). The “precision
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jamming” system is designed to meet these requirements, thus making it the jamming alternative
upon which this paper will focus.

3.2.1 General Considerations
To provide effective denial of contraband phone use, a complete wireless system of jammers must
be designed, deployed, managed and maintained. Thus, an effective precision jamming system will
have significant commonality with MAS.

3.2.1.1 Coverage Footprint Requirements
A key jamming system requirement is that the coverage footprint must be very near to 100% for
the solution to be effective. Thus, if the system design is only 99% effective, there may well be
significant areas in which prisoners could still make illegal calls. It is in prisoners’ interests to find
these areas, so it should be assumed uncovered areas will be sought out and used by inmates when
possible. For example, in a correctional facility of size 1,000 by 1,000 feet (or 1 million square
feet), a 99% effective goal would leave 10,000 square feet of space in which calls could still be
made. Thus, if the goal is to ensure that contraband phones cannot be used within a correctional
facility, a precision jamming coverage goal would likely be closer to 99.99%. A sophisticated
management system will be required to ensure that all jammer devices are operational and
performing to specifications in order to maintain this level of coverage.

3.2.1.2 Denial of Service to All Devices
By their very nature jamming systems deny wireless communication to all users. Therefore,
legitimate personal and professional wireless communication will be prevented along with use by
prisoners. Given the scope and depth of wireless communication’s support of applications for
work, safety and awareness, denial of these services to legitimate users can create issues of
organizational effectiveness and safety. Regarding the latter, jamming systems will also block 911
calls which are essential for effective response to emergency situations and may violate 911
regulations.
For example, the FCC, in its 4th Report and Order setting wireless E911 requirements [7], has noted
its tangible benefits of improving location accuracy with respect to personal safety and protection
of property. Jamming systems will nullify any such benefits.

3.2.1.3 Degradation of Local Commercial Wireless Networks
Due to the nature of R.F. propagation, it is virtually impossible to design a jamming system that
effectively blocks all wireless communication within the correctional facility boundary while
causing no degradation to wireless systems operating outside of the boundary. Due to well accepted
commercial wireless engineering design considerations, wireless networks are designed with
carefully controlled “margins” for connection reliability. In other words, the equipment and
supporting systems necessary to enable reliable communication links to a targeted coverage area
are designed to provide service at low signal strength, thereby extending a particular cell tower’s
coverage area. Thus, while the deployed commercial wireless system is designed to ensure reliable
links between the base station and phone, there is not an excessive “margin for error”, especially at
cell’s coverage edge.
Therefore, when R.F. jamming energy propagates beyond the correctional facility’s security
perimeter, it can cause significant degradation to outside commercial wireless system performance.
Thus a “perfect” jamming system would create high power R.F. interference within the correction
facility’s perimeter and near zero R.F. power outside the perimeter, a design that would be virtually
impossible to implement. R.F. energy from the jamming system will certainly propagate beyond
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the perimeter and, in many cases, create sufficient interference in the surrounding commercial
system to significantly degrade performance or even prevent reliable connections from being
established. In other words, the unplanned interference caused by the precision jamming system
will overwhelm the “margin for error” built into the commercial system. This degradation can
occur even for facilities in rural areas, particularly if there are nearby areas where one can expect
legitimate commercial wireless activity, for example, highways.
As a consequence of these effects, precision jamming R.F. system design must minimize any
negative impact on nearby commercial systems. This design will require coordination with all
potentially affected commercial operators with regard to interference levels and Key Performance
Indicators (KPIs). A reliable, low delay management process will also need to be established and
maintained over the jamming system’s lifetime to ensure that interference issues are quickly
identified and resolved. Thus, a sophisticated management system will be required for a practical
precision jamming system.
Finally, the precision jamming system must be designed to have no measurable negative impact on
spectrum bands used by the correctional staff for communication. In particular, public safety
wireless communication systems must be completely unaffected by the jamming system. Further,
with the introduction of FirstNet, First Responder communications services will be carried over
commercial wireless networks. Thus, it is imperative that R.F. jamming systems not degrade these
networks.

3.2.2 Practical Experience
Although use of jammers is generally prohibited in the United States, there is available information
regarding their practical use in correctional facilities.

3.2.2.1 NTIA Testing
On May 12, 2010, the Department of Commerce published a Notice of Inquiry in the Federal
Register titled “Preventing Contraband Cell Phone Use in Prisons.” The following extracted text
(emphasis added) relates to the issue of jammers [8].
Telecommunications and Information Administration (NTIA) seeks comment on technical
approaches to preventing contraband cell phone use in prisons. Congress tasked NTIA with
developing, in coordination with the Federal Communications Commission (FCC), the
Federal Bureau of Prisons (BOP), and the National Institute of Justice (NIJ), a plan to
investigate and evaluate how wireless jamming, detection and other technologies might be
utilized for law enforcement and corrections applications in Federal and State prison facilities.
To assist in its evaluation of these technologies, NTIA requests information from the public
on technologies that would significantly reduce or eliminate contraband cell phone use
without negatively affecting commercial wireless and public safety services (including
911 calls and other government radio services) in areas surrounding prisons.
The NTIA conducted extensive testing of jammers resulting in numerous issued reports [9], [10],
[11], [12]. Although summarizing this extensive effort is beyond scope for this paper, we have
drawn the following two points from this body of work:
1. Although use of jammers is substantially prohibited in the United States, this NTIA work
has created a resource from which R.F. issues associated with jamming systems can be
identified and assessed.
2. Even for these extremely limited tests, practical information on jammer impact to nearby
commercial wireless systems was generated.
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The focus here will be on point 2. The following excerpt from [9] indicates that even for the
extremely limited jammer device tests at the Cumberland facility (see Figure 1 (left) and Figure 2),
nearby commercial wireless operators reported measurable and significant degradation to their
network performance.
The wireless carriers express concern about the interference that jammers could cause to inband cell phones, based upon the NTIA tests at the Cumberland, Maryland facility. In its
comments, Sprint Nextel contends that after analyzing data gathered at one of its cell sites,
interference may have occurred to cell phones attempting to communicate with that cell site.
Sprint Nextel notes that this cell site provides coverage to the area immediately north of the
jamming zone. Additionally, Sprint Nextel states that during the test period, there was a
“definite trend upward in the rate of dropped calls and a trend downward in successful call
attempts.” Verizon Wireless concludes that “signal measurements from the NTIA jamming
tests taken at the furthest distance outside the prison from the jammer location are strong
enough to cause harmful interference to commercial mobile subscriber devices.” Other
carriers note their concerns over the results of the NTIA testing and the potential for
interference.
Note that these negative consequences resulted from testing of a jammer device as opposed to a
jamming system which consists of numerous devices deployed throughout the entire prison.
Therefore, we expect that a deployment of a poorly designed system consisting of numerous
jammer devices would pose a far greater threat to external wireless systems than did this limited
test.

3.2.2.2 Other Countries
Jammers are legal in other areas of the world where they have been used in many venues, including
prisons. Based on these deployments, the GSMA published a paper titled “Common position
proposal on signal inhibitors (jammers) in Latin America”. Based on this practical experience the
GSMA stated the following:
The issue of mobile signal inhibitors has been treated in different occasions by the GSMA and
different aspects of its use have been covered, from regulatory issues to the security
implications. An important case, we see with great concern, are the issues around the
constraints of mobile services in prisons in Honduras, Guatemala and other countries in the
region. However, despite its use in prisons is not new, this particular approach has not been
included in the debates of the GSMA.
Mobile network operators invest heavily to provide coverage and capacity through the
installation of radio base stations. Therefore, the indiscriminate use of inhibitors affect these
investments since customers can not make use of mobile services in the ranges of these
inhibitors.[13]
The authors, based on this practical experience, go on to make similar arguments against use of
jammers as have been included in this paper. For example, the following figure has been extracted
which shows the significant negative impact on call-drop rate due to being in-range of a jammer
device.

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Figure 5.

Extracted Figure from [13]

This figure shows a time plot for “dropped calls” by a cellular system in the vicinity of a “jammer.”
A “dropped call” denotes a defect in which the cellular system is unable to maintain the wireless
link during the call, and thus the call is prematurely terminated (i.e., before the entities in the call
have finished their communication). While the “jammer” is turned off this severe quality defect
occurs at well below 2% of the time. However, when the “jammer” is turned on this defect
skyrockets to almost 18%. In other words, with the “jammer” on almost one in five calls will
prematurely terminate. Thus, the issues that have led to banning jammers by non-federal entities in
the United States have been confirmed by the practical consequences of these disruptive devices in
Latin America.
The GSMA paper addresses numerous technical and policy issues related to use of jammers. The
following paragraph from the Conclusions section summarizes their findings, which are based on
practical experience.
The inhibition and/or interference caused by these devices affect citizens, public safety and
services. Not only it does [sic] limit network coverage, but also degrades service delivery,
generates harmful interference to additional services that use radio communications,
increasing problems for public health officials and security, it constraints access to primary
support services and can even be used to commit crimes by blocking security services. At the
same time, blocking the signal does not attack the root of the problem - the wireless devices
illegally ending up in the hands of inmates, who then use them for illegitimate purposes, or
that the services aren’t used in inappropriate areas or places. There are many and diverse
alternative ways which allow compliance with this end without affecting users rights. [13]
Additionally, in a recent The Sun article on prevention of contraband cell phone use in UK prisons,
“fears that traditional jammers could take out the mobile phone signal in entire neighborhoods close
to a prison” were discussed [14]. Due to these legitimate concerns, a trial system with sophisticated
technology that can “create a huge virtual filter that detects any handset that hasn’t been approved
by a prison governor and then blocks the signal” is being tested.

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4 C OST C OMPARISON
In this section, we provide a relative cost comparison between Managed Assess and precision
jamming systems. Generation of a comparison with specific dollar costs would require
identification of a specific correctional facility for which the systems are targeted, performance
requirement definition, design and modeling work, component and system costing and OPEX
estimation.

4.1 Correctional Facility Sizes and Characteristics
Correctional facilities come in many sizes and are located in diverse areas, from rural to dense
urban. They also have a wide variety of purposes and house a wide array of inmates with unique
needs for support and supervision. These needs often have significant impacts on the physical
architecture of the facility, the inmate to staff ratio, the risks associated with the inmate population,
and the relative freedoms that the inmates enjoy. For example, medical service areas present
particular challenges due to the use of electronic equipment that supports health and life. Finally,
the facility’s age can cause significant design variation due to changes in building materials, layout
and A.C. power availability.
This complexity does have a significant impact on the challenge associated with designing an
appropriate system to mitigate the contraband phone challenge. A detailed discussion on this set
of topics is beyond the scope of this paper, but it is critical to note that the implication is that
considerable wireless technology sophistication would be required to provide an appropriate design
for either a precision jamming system or a MAS implementation.
We are addressing the variability in size by identifying three facility types based on their physical
“footprint” (as opposed to inmate population size), those being “large,” “medium” and “small.”
Figure 6 shows specific examples for each of these facility types.

Figure 6.

Large, Medium and Small Correctional Facility Working Examples

The large (Federal Correctional Institution in Cumberland, MD) and medium (Dallas County
Detention Center) facilities have been previously discussed in Section 2.2. The small facility
example is the Anaheim Detention Facility in Anaheim California. Note that both the medium and
small facilities are embedded in an urban area while the large facility consists of multiple buildings
and open areas surrounded by a security perimeter.
Of course, there are correctional facilities that are smaller than the Anaheim Detention Facility.
However, once a facility becomes very small the need for any contraband phone denial system
becomes less urgent (i.e., so small that staff can regularly or continually observe prisoner conduct).
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4.2 Cost Assessments
4.2.1 Common Elements
Since both Managed Access and precision jamming systems must deliver managed R.F. energy
throughout the entire correctional facility (indoors and outdoors), there will be significant
similarities between these two systems. These common elements are:
1. System design and deployment (Non-Recurring Expense, NRE) that includes site
surveys, R.F. propagation analyses, engineering design, and the deployment of the system.
2. Head-end device(s) that provides the R.F. interface (Capital Expenditure, CAPEX)
3. Distribution system that enables precision delivery of R.F. energy within the correctional
facility’s perimeter (CAPEX)
4. Management system that ensures continuity of service, monitors system/element
performance, detects fault conditions and communicates relevant information to the
appropriate managers or other stake-holders (CAPEX)
5. Operational expenses (Operational Expenditure, OPEX) includes an ongoing assessment
of the R.F. footprint. The objective is to minimize and ideally eliminate both unintended
coverage holes within the prison facility and leakage beyond the prison boundary. Sensorbased observations are used for incremental propagation modeling / analyses and for finetuning adjustments of R.F. coverage (e.g., tweaks to antenna directionality, power levels
and other system configurable parameters). Numerous other OPEX costs include
management personnel, maintenance, troubleshooting and upgrade activities, among
others.

4.2.2 Element Differentiation
Although there are common elements, the specific requirements and associated capabilities of these
elements will vary depending on whether it is part of a Managed Access or precision jamming
system.

4.2.2.1 System Design and Deployment
4.2.2.1.1 Overview
Each correctional institution has its own unique structure and layout, and in most cases, requires
individual surveys, design, engineering, and deployment for the implementation of MAS and
precision jamming systems. The R.F. surveys and system designs will need to address factors
affecting R.F. propagation including, but not limited to, the footprint of the institution, building
materials, internal structures, and locations of inmates. Both system types will require very similar
individualized system design and deployment to be effective at denial of service without impacting
commercial wireless networks outside the confines of a correctional facility. Given that the intent
of the R.F. survey and system designs are similar in nature between MAS and precision jamming
systems, there will be very little cost differentiation expected.
MAS and jamming systems should be hardened to withstand damaging weather and other
environmental conditions. They should also be hardened against potential sabotage because
inmates may attempt to disable the system by destroying infrastructure such as cabling and
antennas. The design may require burying cables and erecting fencing around exposed system
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infrastructure. These hardening efforts result in cost to the initial design and subsequent operational
phase, and will be similar for both MAS and precision jamming systems.
4.2.2.1.2 Relative Cost Estimate
Both MAS and precision jamming systems require similar levels of design and deployment
complexity. Thus, due to these essentially identical requirements, the relative cost can be expected
to be relatively the same regardless of facility size.
Facility Size

Table 1.

Relative Jamming
System Cost

Small

~1x

Medium

~1x

Large

~1x

Design and Deployment: Relative Cost for Jamming System with MAS Baseline

4.2.2.2 Head-End Device
4.2.2.2.1 Overview
For a MAS, the head-end device will be a “base station” that provides the bi-directional R.F.
communication interfaces. At a minimum, the head-end will need to support multiple cellular
bands and technologies (e.g., 2G, 3G and 4G). Most MAS base stations consist of software defined
radios (SDRs) that provide simultaneous support for the range of cellular bands and technologies
through software implementations on reusable hardware platforms. Through the use of these SDR
based “soft modems,” various combinations of cellular bands and technologies can be
accommodated. The use of SDRs allows the MAS to support multiple cellular bands and
generations of technologies/standards in a single system.
For a precision jamming system, the head-end device will be a transmit signal source that provides
the service denial interference signal. This interference signal must be highly frequency selective.
That is, it must generate energy only in the Down-Link (DL) bands of the FDD systems to be
blocked (e.g., cellular) and in the communication bands for the TDD systems to be blocked. All
other bands used for legitimate wireless communication must have virtually no significant energy
in them. This frequency selectivity is generally implemented using high precision filtering systems.
Given the niche nature of the available correctional facility market, it will be difficult for precision
jamming systems to compete with MAS systems. That is, since precision jamming systems will
tend to be custom designed solutions for correctional facilities they will have to recoup the costs of
engineering, research and development over a relatively small market size. In addition, precision
jamming solutions must address the evolving communication landscape (i.e., new generations of
mobile access technologies, spanning a more diverse set of frequency bands) within these same
niche market constraints.
In contrast, MAS systems benefit from the hardware and software volumes generated by the worldwide, standardized cellular industry. That is, cellular costs are driven by competition among the
global ecosystem of vendors and component suppliers, all competing to serve the needs of
commercial mobile users. As a consequence, the research and development cost of associated
equipment is spread out over a worldwide marketplace and is driven by extremely high levels of
competition. Thus, the MAS solutions will be on a steeper cost reduction curve than that of
precision jamming.

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In comparison, it is difficult to imagine a comparable ecosystem of precision jamming vendors
vying to compete based on cost and performance. The vendor ecosystem will very likely be small
and limited to proprietary systems with significantly lower market incentive to reduce product
costs. This disadvantage will be exacerbated by the introduction of new cellular technologies which
will force the proprietary precision jamming systems to evolve within the context of a niche
marketplace.
4.2.2.2.2 Relative Cost Estimate
Although the head-end devices used for MAS and precision jamming systems are different in
function, the complexity required to implement this functionality is similar. However, as the above
discussion demonstrates, MAS head-ends will have cost advantages associated with the volumes
and distributed costs of the cellular marketplace. MAS head-ends will evolve to utilize pico-cell
technology and leverage their cost reductions over time. Thus, we expect that the precision
jamming head-end cost will be at a disadvantage relative to the MAS. The precision jamming
disadvantage will likely increase as the facility size increases because multiple head-ends may be
required. We have chosen to use conservative estimates for this precision jamming disadvantage
pending additional data.
Facility Size

Table 2.

Relative Jamming
System Cost

Small

~1.1x

Medium

~1.2x

Large

~1.3x

Head-End Device: Relative Cost for Jamming System with MAS Baseline

4.2.2.3 Distribution System
4.2.2.3.1 Overview
MAS systems have been successfully deployed using Distributed Antenna System (DAS)
technology. Due to the primary requirement of providing R.F. coverage with power that
overwhelms signals from sites outside the correctional facility, an active DAS may be necessary
for R.F. signal distribution. An active DAS distributes R.F. signals to active remote units via optical
fiber. The remote units require both power and control interfaces.
Since jamming systems need to deliver sufficient interference power throughout the correctional
facility to block communication, the R.F. distribution will almost certainly require an active DAS,
especially when taking into account the design principles of the local cellular network (see section
3.2.1.3). Each remote unit must interface with an antenna that is capable of covering all channels
to be jammed. However, whereas MAS systems require bi-directional R.F. distribution, precision
jamming systems require only transmitters on the active DAS. Since active DAS systems up to this
point have been designed to improve coverage and performance of conventional mobile services in
buildings and venues, they have been designed to be bidirectional. An active DAS system that is
optimized for the transmit-only nature of a precision jamming system would require new design
and development. Thus, it is assumed that the deployment of a precision jamming system will
utilize a conventional active DAS distribution system, with Up-Link signals filtered out at the headend. Therefore, there is no immediate cost difference that can be garnered from precision jamming
systems requiring transmit-only capable active DAS systems.

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4.2.2.3.2 Relative Cost Estimate
Both MAS and precision jamming systems are required to cover virtually 100% of the facility area
that is accessible to prisoners with signal power greater than that from outside cellular systems.
Thus, due to these essentially identical requirements, the relative cost will be virtually the same
regardless of facility size.
Facility Size

Table 3.

Relative Jamming
System Cost

Small

~1x

Medium

~1x

Large

~1x

Distribution System: Relative Cost for Jamming System with MAS Baseline

4.2.2.4 Core Network (MAS Only)
4.2.2.4.1 Overview
The core network provides connectivity and associated features and services from the head-end
base station(s) to the commercial wireless network (including the Internet). This network element
is required for MAS systems, but is not required for precision jamming systems (since jamming
eliminates network traffic). In addition to network connectivity, some MAS vendors use the core
network to provide 911 services as well as the lawful intercept and forensics associated with the
Communications Assistance for Law Enforcement Act (CALEA). Thus, for instance, under court
orders and/or applicable laws, analyses that detail which users are accessing the system including
time, duration and frequency, can be provided. Forensics on short message service (SMS) text
messages can also be compiled and logged. Some MAS systems also offer services that locate
active devices within the facility in addition to managing its communications.
Core networks are nearly fixed price across all sizes of MAS systems. However, the MAS system
can support the active phone service, forensics, and overall management based on having the core
network connectivity and capability.
4.2.2.4.2 Incremental Cost Estimate
Since a precision jamming system does not require a core network, the cost is an incremental
increase for the MAS. Based on discussions with MAS vendors we believe that the MAS core
network will add approximately $50K of incremental cost regardless of the facility size.

4.2.2.5 Management System
4.2.2.5.1 Overview
The MAS management system must manage connectivity from the base station to one or more of
the commercial cellular networks. It must also provide the monitoring, configuration and user
interface capabilities necessary to manage the local R.F. communication system.
The precision jamming management system must also provide monitoring, configuration and user
interface capabilities. A reliable, low delay management process is required to ensure that
interference issues with nearby wireless systems are quickly identified and resolved.
The MAS and precision jamming management systems will have many common capabilities and
functions, including:

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•

Self-monitoring capability and telemetry features that enable alerting the operator about
equipment or component failure leading to signal strength fluctuations (similar cost).

•

Signal strength and coverage must be routinely checked to ensure the signal remains within
the designed performance parameters inside and outside the correctional facility (expected
higher precision jamming cost due to stricter monitoring requirements).
o

The verification of a jamming signal cannot be done remotely unless specific R.F.
monitoring devices are installed at multiple locations on the perimeter of the
facility. As has been previously noted, R.F. jamming signals must be low enough
in power external to the facility so that there is no degradation to the external
cellular network. Thus, a monitoring system would need to be installed that
continuously monitors the jamming system R.F. power outside of the facility.

o

For a MAS system design, as long as any R.F. signal leakage beyond the
correctional facility perimeter is lower in power than that provided by the external
cellular network, there will be minimal chance of service degradation to the general
public. This condition can be ensured through proper design and deployment of
the MAS system.

•

The R.F. coverage footprint inside the prison must be routinely checked to ensure the MAS
or jammer signal strength is dominant within the facility (similar cost).

•

MAS and precision jamming systems may need to be updated to cover new cellular bands
and/or systems, resulting in increasing complexity and cost (higher cost for precision
jamming expected since the MAS head-end is designed to support efficient upgrade).

•

Remote management of all active components for diagnostics and understanding system
operational status (higher precision jamming expected cost due to need for higher
frequency, lower latency monitoring and response).

4.2.2.5.2 Relative Cost Estimate
Although many of the cost elements are similar between these two systems, we expect precision
jamming management costs to be higher for medium and large facilities. This is due to the
increasing complexity of indoor/outdoor spaces that must be covered by the jamming signal as the
facility size increases, especially if the correctional institute is a campus.
As the facility size increases, there is a corresponding increase in the monitoring and diagnostic
capabilities necessary to ensure that nearby wireless systems are not degraded. This issue is of
particular sensitivity for jamming systems, as any R.F. energy leakage beyond the facility perimeter
can significantly degrade or outright block legitimate wireless communication by the general
public. Therefore, the jamming system must be designed to stricter requirements than the MAS,
thus increasing the precision jamming system cost. Due to these considerations, the relative
management cost for a jamming system is expected to be higher for medium and large facilities.
Facility Size

Table 4.

Relative Jamming
System Cost

Small

~1.0x

Medium

~1.1x

Large

~1.2x

Management System: Relative Cost for Jamming System with MAS Baseline

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4.2.2.6 Operational Expenses
4.2.2.6.1 Overview
This section assumes that a managed and monitored precision jamming management system has
been deployed as described in section 4.2.2.5. Given that, then both MAS and precision jamming
systems incur common operating expense items that include:
•

Costs associated with operational performance testing obligations. The following need to
be identified:
o

resources for recurring performance testing (labor and instrumentation for
coverage measurement and analysis)

o

operational costs associated with characterization of footprint quality (coverage
holes inside and leakage outside the prison facility)

o

testing methodology that will be used to assess the presence of holes and/or leakage

•

Management personnel, maintenance and troubleshooting

•

System upgrades to accommodate introduction of new technologies and protocols

4.2.2.6.2 Relative Cost Estimate
The costs associated with above functions are expected to be roughly similar regardless of facility
size.
Relative Jamming
System Cost

Facility Size

Table 5.

Small

~1x

Medium

~1x

Large

~1x

Operational Expenses: Relative Cost for Jamming System with MAS Baseline

4.2.3 Cost / Performance Tradeoffs
Given the similar cost associated with deployment of precision jamming and MAS solutions, the
question arises concerning cost/performance tradeoffs. For example, if the coverage footprint or
operation timespan requirements are reduced, does one of these solutions have an advantage?
Prior to addressing this issue, we reiterate that such requirement reductions will significantly reduce
the effectiveness of any solution. That is, given the existence of a highly motivated, adaptable and
creative inmate population (with lots of time on their hands), we can expect that even marginal
system requirement reductions will be leveraged into major illicit use benefits.
Given this concern, we provide the following assessment for these two systems.
•

System design and deployment (NRE)
Both solutions will benefit at similar levels for requirement reductions.

•

Head-end device (CAPEX)
This is a fixed cost for both solutions, thus this component is insensitive to requirements
reduction.
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•

Distribution system (CAPEX)
Both solutions will benefit at similar levels for requirement reductions.

•

Core Network (CAPEX)
This component is unique to a MAS. The proportional cost impact of this fixed cost will
increase as other component costs decrease with requirement reduction.

•

Management system (CAPEX)
Both solutions will benefit at similar levels for requirement reductions.

•

Operational expenses (OPEX)
Both solutions will benefit at similar levels for requirement reductions.

The above analysis in isolation could be interpreted to suggest that there may be a crossover point
at which a precision jamming solution would be more cost effective than a MAS system given the
fixed cost of the core network necessary for an MAS solution. However, the numerous additional
performance and cost issues previously discussed may suggest that any limited advantage for
precision jamming solutions will be more than offset by the many advantages associated with MAS,
including long term cost, in the majority of prison deployment scenarios. Most importantly, a
reduced-performance “solution” is not recommended because of probable MAS or jamming
coverage gaps and thus, it does not address fully the underlying problem.

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5 C ONCLUSIONS
5.1 Summary
In Section 4 we identified major system elements for MAS and precision jamming systems and
analyzed the associated relative cost implications. Three prison facility sizes were considered:
small, medium and large (see Section 4.1).
The results (see Section 4.2 for details) are summarized in Table 6. Note that all elements were
assessed in relative terms (i.e., cost of the precision jamming system relative to the MAS).
Element

Facility Size Cost Assessment
Small

Medium

Large

Design & Deployment
(NRE)

~1x

~1x

~1x

Head-End Devices
(CAPEX)

~1.1x

~1.2x

~1.3x

Distribution System
(CAPEX)

~1x

~1x

~1x

Core Network – MAS
Only (CAPEX)

~$-50K

~$-50K

~$-50K

Management System
(CAPEX)

~1x

~1.1x

~1.2x

Operational Expenses
(OPEX)

~1x

~1x

~1x

Table 6.

Cost of Jamming System with Respect to the MAS Baseline

Summaries for the assessed facility sizes follow:
•

In a large facility, a precision jamming system is expected to be costlier than a MAS system
due to larger management and head-end costs.

•

In a medium facility, the precision jamming system’s management and head-end costs are
expected to be higher. However, the MAS core network cost would offset some of this
difference. Thus, the total cost may be essentially the same, with a possible advantage to
the MAS solution.

•

In a small facility, the additional system cost of the MAS core network will be a larger
percentage of the total cost than for a medium or large sized facility. The slightly lower
MAS head-end cost will compensate somewhat for the core network cost in this relative
comparison. Thus, the MAS may be slightly more costly.

While these results focus on general expectations, because of individual prison characteristics cost
variation will occur.
These results are in general agreement with the CellAntenna FCC filing [15] which states that
“Managed Access commands only a 10%-15% higher price-tag compared to jamming.” Our
assessment indicates that a MAS will likely be of equivalent or slightly higher cost for medium to
small prison facilities. However, MAS may have a cost advantage in large facilities. Thus, both
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we and CellAntenna have concluded that there will be a rough equivalence between the cost of
“precision jamming” and MAS solutions.
In addition, Harris Corporation has conducted a jamming vs. MAS assessment that concludes with
regard to cost:
To effectively block calls, the cost, engineering, installation, and logistics of a jamming system
are very similar in scope to a managed access system. [16]
The results of this paper are consistent with this analysis.
Because of the extreme diversity in correctional facility characteristics it is impossible to determine
absolute cost values. Therefore, we provide the following rough order of magnitude (ROM) ranges
of total system cost as a means for calibrating the relative results. Note that these costs assume the
above discussed rough equivalence between precision jamming and MAS solutions.
Facility Size
Small

Table 7.

Total Cost Range
$300,000 - $600,000

Medium

$500,000 – $1,200,000

Large

$1,000,000 - $2,000,000

ROM Total Cost Ranges (Total = NRE + CAPEX; OPEX excluded)

In Table 8, ROM cost ranges for NRE, OPEX and CAPEX components are provided. These
estimates are intended to provide additional context for the relative cost results. The NRE and
CAPEX costs focus on the initial system design and deployment. However, over time additional
NRE and CAPEX expenditures will be required as the facility evolves and equipment wears out or
needs to be upgraded.
Facility Size

NRE

OPEX

CAPEX

Small

$150,000 - $250,000

$30,000 - $50,000 per year

$150,000 - $350,000

Medium

$250,000 - $500,000

$50,000 - $100,000 per year

$250,000 - $700,000

Large

$500,000 - $800,000

$100,000 - $200,000 per year

$500,000 - $1,200,000

Table 8.

ROM Decomposed Cost Ranges

Note that the MAS will permit 911 emergency calls, not affect public safety (and other) wireless
systems and allow GPS location services. A precision jamming system will likely degrade or
disable these critical services. The significant benefits that will be lost by blocking 911 calls using
precision jamming systems were discussed in section 3.2.1.2.
Finally, with the deployment of FirstNet, First Responder communications may be carried on
commercial cellular bands. Since a jammer does not discriminate between cellular users, first
responders attempting to communicate on the affected cellular frequency bands will be blocked.
This would be a problem for first responder communications within the correctional facility, as
well as outside of the facility if the jammer degrades local commercial wireless networks that also
carry First Responder communications.

5.2 Conclusion
Given the significant baseline similarities between MAS and precision jamming systems and the
fact that each has marginal cost advantages in specific areas, we conclude that the overall costs will
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be similar between the two systems. Operationally however there is an enormous difference in that
a jamming system, even if very well designed and skillfully deployed, is still effectively a very
“blunt instrument” approach to the problem while the MAS approach is more of a “versatile tool”
that has numerous other diagnostic benefits. The MAS solution thus enables prison officials to
gain a valuable perspective on the wireless activity in the prison and to use this information as
appropriate to detect and deter not only wireless misuse, but potentially other contraband and
general criminal activities.

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6 R EFERENCES
[1] Letter from James D. Schlichting, Acting Chief, Wireless Telecommunications Bureau,
to Devon Brown, Director, District of Columbia Department of Corrections, DA 09-354,
February 18, 2009.
[2] “Mobile signal jammers donʼt work on 3G, 4G in Punjab jails | punjab | Hindustan Times,”
http://www.hindustantimes.com/punjab/in-punjab-jails-mobile-signal-j…don-t-work-onhigh-speed-networks/story-VTrcrIgAvgTVIpYQoA4lBJ.html.
[3] “Analysis of Managed Access Technology in an Urban Deployment: Baltimore City Jail
Complex,” Engility Corporation, September 2015.
[4] Letter from National District Attorneys Association to Ajit Pai, Chairman, Federal
Communications Commission, October 27, 2017.
[5] Letter from U.S. Department of Justice to Marlene H. Dortch, Secretary, Federal
Communications Commission, GN Docket 13-111, August 28, 2017.
[6] Letter from Arkansas Board of Corrections to Ajit Pai, Chairman, Federal
Communications Commission, GN Docket 13-111, July 20, 2017.
[7] FCC 4th Report and Order, Wireless E911 Location Accuracy Requirements, PS Docket
7-114, Feb. 3, 2015.
[8] Federal Register Vol. 75, No. 91, Wednesday, May 12, 2010, Notices: Department of
Commerce, National Telecommunications and Information Administration, Docket No.
100504212–0212–01, Preventing Contraband Cell Phone Use in Prisons.
[9]

“Contraband Cell Phones in Prisons: Possible Wireless Technology Solutions,”
Department of Commerce Report, December 2010.

[10] “Emission Measurement Results for a Cellular and PCS Signal-Jamming Transmitter,”
Department of Commerce, NTIA Report TR-10-465, February 2010.
[11] “Emission Measurements of a Cellular and PCS Jammer at a Prison Facility,” Department
of Commerce, NTIA Report TR-10-466, May 2010.
[12] “Initial Assessment of the Potential Impact from a Jamming Transmitter on Selected InBand and Out-of-Band Receivers,” Department of Commerce, NTIA Technical
Memorandum 10-468, May 2010.
[13] “Common position proposal on signal inhibitors (jammers) in Latin America,” GSMA, 14
July 2014.
[14] “Jails will FINALLY start jamming lags' smuggled mobiles as rollout for high-tech
blockers begins.” https://www.thesun.co.uk/news/1956860/government-plans-smuggledmobile-crackdown-in-prisons/.
[15] Reply Comments of CellAntenna Corporation, Howard Melamed, President Jamming
Versus Managed Access and IMSI Catching, GN-Docket No. 13-111, 28 December 2017.
[16] https://www.harris.com/sites/default/files/downloads/solutions/mas_vs._jamming_infogr

aphic_final.pdf.

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