Practical and cost-effective communications solutions are needed to enable control of the growing number of integrated distributed energy resources (DERs) and grid-edge local aggregator devices such as home energy management systems. Each year, the total installed photovoltaic (PV) system capacity increases by an estimated 5 GW, over half of which is interconnected to the distribution system.1 PV’s increasing penetration—already accounting for the bulk of DER capacity—underscores the need to enable and manage its continued integration on the distribution system.2 Much previous work has shown that advanced distribution management systems (ADMS), which are effectively integration platforms for various grid control and visibility applications, can help enable the integration of higher levels of PV while also improving the overall performance and efficiency of the distribution circuit. Greater connectivity and controllability of utility- and customer-owned equipment increases the level of DER integration and overall circuit performance.3 The required performance of the enabling communications system, however, has been less thoroughly studied and is often greatly oversimplified in ADMS performance analysis. The availability of new technologies such as distributed sensors, two-way secure communications, advanced software for data management, and intelligent and autonomous controllers is driving the identification of communications standards and general requirements,4 but the link between the communications system and the expected performance of a utility-implemented control system such as an ADMS or other communications-reliant protective function requires further investigation.

1. jli@anterix.com
21, rue d’Artois, F-75008 PARIS CIGRE US National Committee
http://www.cigre.org 2019 Grid of the Future Symposium
Evaluation of Utility Advanced Distribution Management System (ADMS) and
Protection Functions Over Private LTE Communications Network
J. LI B. MATHER
Anterix National Renewable Energy Laboratory (NREL)
USA USA
SUMMARY
Practical and cost-effective communications solutions are needed to enable control of the
growing number of integrated distributed energy resources (DERs) and grid-edge local
aggregator devices such as home energy management systems. Each year, the total installed
photovoltaic (PV) system capacity increases by an estimated 5 GW, over half of which is
interconnected to the distribution system.1
PV’s increasing penetration—already accounting
for the bulk of DER capacity—underscores the need to enable and manage its continued
integration on the distribution system.2
Much previous work has shown that advanced
distribution management systems (ADMS), which are effectively integration platforms for
various grid control and visibility applications, can help enable the integration of higher levels
of PV while also improving the overall performance and efficiency of the distribution circuit.
Greater connectivity and controllability of utility- and customer-owned equipment increases
the level of DER integration and overall circuit performance.3
The required performance of
the enabling communications system, however, has been less thoroughly studied and is often
greatly oversimplified in ADMS performance analysis. The availability of new technologies
such as distributed sensors, two-way secure communications, advanced software for data
management, and intelligent and autonomous controllers is driving the identification of
communications standards and general requirements,4
but the link between the
communications system and the expected performance of a utility-implemented control
system such as an ADMS or other communications-reliant protective function requires further
investigation.
1
Mather, B., Yuan, G., (2018). Going to the Next Level: The Growth of Distributed Energy Resources, IEEE
Power and Energy Magazine, v.16 issue 6.
2
Palmintier, B., et al., (2016). On the Path to SunShot: Emerging Issues and Challenges in Integrating Solar with
the Distribution System (NREL Technical Report No. NREL/TP-5D00-65331). Golden, CO.
3
Palmintier, B., et al., (2016). Feeder Voltage Regulation with High Penetration PV Using Advanced Inverters
and a Distribution Management System: A Duke Energy Case Study (NREL Technical Report No. NREL/TP-
5D00-65551). Golden, CO.
4
https://www.nist.gov/programs-projects/smart-grid-communications-0, updated May 7, 2018.

2. 2
Long-Term Evolution (LTE) is a standardized specification for wireless broadband
communication. LTE is based on the 3rd Generation Partnership Project (3GPP), starting
with Release 8 specifications developed in 2008. Benefits of this technology include:5
- Higher bandwidth - 4G LTE provides broadband speeds well above 3G speeds
- Low latency - lower idle-to-active times (improved network responsiveness)
- High spectrum efficiency – higher air-interface capacity, improved cost efficiency
- End-to-end IP network – An all IP network means easier integration and
interoperability
- Enhanced security features – 3GPP security architecture for user equipment, access,
network, visibility
- Quality of Service – integration of existing network service layers to corresponding
air-interface QoS class identifier (QCI)
- Robust eco-system – LTE, since 3GPP Release 8 (2008), included in more than 5,000
devices from over 400 suppliers.6
Given the benefits listed above, LTE should be evaluated for its ability to meet the growing
need for advanced control of DERs and grid-edge assets. Though utilities can use readily
available public LTE networks for broadband connectivity to any number of endpoints and
applications, this paper addresses the use of a private LTE (P-LTE) network to support a
critical protective application called direct transfer trip (DTT). DTT is a low-latency, low-
bandwidth application that holds a particular promise for the cost-effective integration of
DERs, particularly as they become increasingly prevalent in the distribution grid.
Specifically, this paper addresses the evaluation of P-LTE for DTT conducted in the National
Renewable Energy Laboratory’s ADMS Test Bed. The paper also discusses future
performance evaluation of ADMS applications with integrated P-LTE.
KEYWORDS
Advanced Distribution Management System
Distributed Energy Resources
Direct Transfer Trip
Private LTE
Broadband Communications
Industrial Control Systems
5
https://www.telecomstechnews.com/news/2016/mar/15/opinion-4g-lte-and-its-benefits-enterprise-networks/ ,
March 15, 2016
6
https://gsacom.com/paper/status-lte-ecosystem-report-5614-lte-devices-announced-455-suppliers/ , June 24,
2016

3. 3
Background
Research Institution, Utility Industry and Technology Partner Collaboration
A number of current projects within the Power System Engineering Center at the National
Renewable Energy Laboratory (NREL) focus on the development and practical
implementation of advanced distribution management systems (ADMS) that require data
communications among devices or between a centralized ADMS controller and multiple
pieces of utility equipment such as capacitor bank controllers or voltage regulator controllers.
Frequently, these laboratory implementations of ADMS use hardwired connections as their
communications pathways. In order to evaluate the performance of ADMS and other utility
communication-reliant functions in a realistic environment, NREL and Anterix partnered on a
project focused on the integration of utility control systems with wireless communications,
specifically P-LTE. In this project, Anterix provides its expertise and existing private
broadband solution to implement a realistic utility communications network that draws
heavily on NREL’s ADMS Test Bed and past and current projects related to ADMS testing.
In consultation with an industry advisory board (IAB) formed specifically for the project, the
project team worked to ensure that evaluation activities reflected real-world, current and
future utility applications and use cases. The IAB was instrumental in defining use cases and
test scenarios that would be meaningful in common utility control procedures. The IAB also
provided invaluable input on the amount, type, and priority of data that a combined utility
communications system such as P-LTE would carry. It also played a key role in reviewing
and providing feedback to test results. In return, IAB members would be using project results
to guide its own network infrastructure plans. IAB members include seven utilities and one
industry expert:
Table 1. Industrial Advisory Board Members for NREL/Anterix Project
Consumers Energy
Evergy
Duke Energy
Eversource
Holy Cross Energy
Hawaiian Electric Company
Xcel Energy
Dots and Bridges
Given the use cases NREL wished to address and utilities’ need to enable advanced control of
their distribution networks, the project team focused on testing wireless data network use
cases that relate to ADMS, a core component of grid modernization initiatives across the
country. The team also developed a mission critical use case with low latency requirements
to represent the criticality of data communications, to control certain critical grid-edge
equipment, during events like faults and abnormal operating conditions.
Distributed Generation and its Impact to the Smart Grid
DERs—produce electricity at or near where it will be used, frequently via technologies like
solar photovoltaic (PV) systems and combined heat and power (CHP) A DER system may
serve a single structure, such as a home or business, or it may be part of a microgrid (a

4. 4
smaller grid that is also tied into the larger electricity delivery system) that serves a major
industrial facility, a military base, or a large college campus. When connected to the electric
utility’s lower voltage distribution lines, DER can help support delivery of clean, reliable
power to additional customers and reduce electricity losses along transmission and
distribution lines.7
In the residential sector, common DER systems include:
- Solar photovoltaic panels
- Small wind turbines
- Natural gas-fired fuel cells
- Emergency backup generators, usually using gasoline or diesel fuel
In the commercial and industrial sectors, distributed generation can include resources such as:
- Cogeneration systems
- Solar photovoltaic panels
- Wind
- Hydropower
- Biomass combustion or cofiring
- Municipal solid waste incineration
- Fuel cells fired by natural gas or biomass
- Reciprocating combustion engines, including backup generators which may be oil-
fueled
Utility-scale DER systems typically generate from 1 to 10 MW of power.8
In many cases,
they must be connected to the utility grid in order to provide power to other utility customers.
In times of extreme events—such as when lightning strikes a tree and downs a power line—
even a grid-connected DER may become isolated or “islanded” if the utility grid is not
designed with appropriate protections to enable transmission from DER power sources. An
unintentionally islanded DER may be left to provide service to the utility’s local customers,
essentially becoming an unregulated power system at risk of unpredictable conditions because
of the mismatch between the local demand for electricity and the isolated DER's limited
capacity.
The increase in DERs is driving the need for cost-effective communications to help control all
these new distribution-connected generation elements and the evaluation of the effectiveness
of those communications solutions. Utilities must ensure reliability and resiliency of their
systems, and that requires dependable communications among the customer location, the
DER system, and the utility control system. The following figure illustrates the growth in
DERs.
7
https://www.epa.gov/energy/distributed-generation-electricity-and-its-environmental-impacts , January 19,
2017
8
Distributed Generation Direct Transfer Trip (DTT), URI Capstone Project 2016

5. 5
Figure 2.10.1: Forecasted Demand per Source
(Source: Navigant)
Private LTE
P-LTE systems are particularly well-suited for providing the critical communications
capability that electric utilities and other enterprises need to consolidate the many disparate
communications links they use today—both point-to-point and point-to-multipoint.9
P-LTE
networks offer several core benefits that address the critical needs of electric utilities:
- Licensed spectrum provides the network operator with recourse in the event of
interference. Causers of interference must comply with FCC mandates or face
prosecution and fines for non-compliance.
- Operator control of a private LTE network enables a utility to determine the
infrastructure its data traverses. In the same way applications for critical infrastructure
are rarely hosted in public cloud service providers such as Amazon or Google, utilities
will be in control of their infrastructure and their traffic management policies, not
subjected to a common carrier’s policies.10
- Inherent security features of LTE include mutual authentication between user
equipment (UEs) and base stations (eNBs) as well as the use of proven encryption
schemes; these are two major improvements of LTE11
over its predecessor mobile
wireless technologies. Overlaying LTE with best-practice security measures such as
9
CIGRE US National Committee 2018 Grid of the Future Symposium, Leveraging Private LTE Networks in the
Electric Utility, L. Greenstein
10
ARS Technica. “Fire dept. rejects Verizon’s ‘customer support mistake’ excuse for throttling”
https://arstechnica.com/tech-policy/2018/08/fire-dept-rejects-verizons-customer-support-mistake-excuse-for-
throttling/ Jon Brodkin August 22, 2018
11
National Institute of Standards and Technology. US Department of Commerce. “LTE Security – How Good Is
It?” https://csrc.nist.gov/CSRC/media/Presentations/LTE-Security-How-Good-is-it/images-
media/day2_research_200-250.pdf Michael Bartock, Jeffrey Cichonski, Joshua Franklin

6. 6
virtual private network (VPN) tunnels provides the level of security needed for critical
infrastructure.
- Visibility of network elements is a key component of 3GPP cyber-security. In non-
private systems, the service provider controls visibility and rarely shares it fully with
network users. In privately-owned systems, the user gains full control over visibility.
- Combining traffic from multiple applications with various priority, throughput, and
latency requirements is a capability LTE provides through its Quality of Service (QoS)
class identifier (QCI) features.
- Spectral efficiency is a great benefit of broadband technology, particularly as
compared to wideband. The efficiency of LTE enables high data rates and permits
multiple users to share a common channel.
- LTE narrowband low power wide area (LPWA) Internet of things (IoT) technology
enables LTE spectrum to be shared among broadband LTE applications and
narrowband IoT (NB-IoT) applications. NB-IoT is ideal for monitoring or controlling
very large quantities of devices or equipment that generally require relatively low
uplink and downlink data rates.
- Mobility enables mobile worker devices to connect automatically into the P-LTE
network for seamless access to vital backend resources.
Project Timeline
The NREL/Anterix project started in February 2019 and consists of two phases. Phase 1 of
the project is completed and included the implementation of a photovoltaic inverter system’s
direct transfer trip (DTT) feature over P-LTE. DTT is a protection function that quickly
disconnects or shuts down a DER (typically a large MW-scale DER) on a distribution circuit
when that circuit substation breaker or an upstream recloser opens. Without rapid
disconnection by DTT, subsequent closing of the breaker or recloser could connect the
normally functioning portion of the power system into a powered and potentially out-of-phase
remainder of the circuit, potentially causing damage to utility and customer equipment. The
disconnection also ensures that the DER does not become unintentionally islanded, continuing
to generate even when disconnected from the utility.
Most utilities require low latency communications for the implementation of DTT
functionality. This paper provides initial testing results of Phase 1 laboratory evaluations. The
NREL/Anterix project team intends to collect and report a more comprehensive set of DTT
performance results in the future.
Phase 2 of the project will use NREL’s ADMS testbed to evaluate both P-LTE capabilities
implicated by additional use cases as well as end-to-end ADMS application use cases. The
project will provide a quantified understanding of the impact of the communications portion
of an ADMS on overall grid-level performance when the communication network is a private
LTE broadband network. The project team will publish the results of its evaluation of a
number of ADMS/control use cases tested on a laboratory LTE network implementation. In
performing the evaluation, the project team will gather two sets of measurements:
Two sets of measurements will be gathered as part of this project:
- End-to-end ADMS functions and their performance metrics and
- Air-interface performance metrics such as throughput and latency for the LTE system,
measured on both uplink and downlink data paths under various signal strength, signal
quality, and user traffic scenarios.

7. 7
P-LTE Test Bed
NREL Facilities
This project utilizes NREL’s Energy Systems Integration Facility (ESIF). Specifically, ESIF’s
Power System Integration Laboratories (PSIL), the location of the ADMS test bed, has been
augmented with the addition of a private LTE network. Thus, the project enjoys a robust
range of resources including the ADMS testbed, grid-edge devices, DER systems, power
components for automatic voltage regulation, simulation for real-time control, and realistic
electric distribution communications traffic loading profiles. For end-to-end IT networking
functions, ESIF provides VLANs, management plane VPN, and integration of network
switches and routers to the P-LTE system.
LTE System
The LTE system is an all-inclusive software implementation of LTE core (ePC-
HSS/MME/SGW/PGW) elements and the LTE radio access network (eNB) functions. The
team implemented the LTE system as a private network running in a Linux environment on a
stand-alone server rack. The network allows LTE user equipment or endpoints with
appropriate USIM cards to attach on Band 8 (900 MHz). The system, based on 3GPP Release
14 and implementing some later functions, includes the following key features:
- Visibility and monitoring of the air-interface
- Support for NB-IoT, Cat-M1, and LTE technologies
- Air-interface QoS prioritization mapped to specific DSCP/TOS IP tags
- 3GPP security architecture including access and network authentication, air-interface
integrity and encryption control
- Access class control with or without pre-emption
- MAC scheduling optimized for traffic loading and RF channel profiles
- MIMO transmission modes
Department of Energy’s Guidance and Support
Department of Energy (DOE) designated the NREL/Anterix effort as an ESIF High-Impact
Project. This designation provided additional funding to expand the scope of the project and
to focus it on developing ESIF capabilities related to utility communications systems
integration and performance evaluation. It is currently one of seven projects NREL recently
presented initial results from the project to the DOE as part of the ESIF User Program’s
yearly review. Two key objectives related to the ESIF High-Impact designation are:
- Ensure ESIF capabilities are relevant to support any communications system: Latency
communications measurements are relevant to all forms of communications (wired or
wireless).
- Carefully consider communications role in utility resiliency: The project addresses
both (1) the resilience of the enabled power system benefiting from the improved
utility control (ADMS, etc.) provided by the communications system, and (2) the
resilience of the communications system itself (in the face of poor signal strength,
congestion scenarios, etc.)
Demonstration of Direct Transfer Trip of a Photovoltaic Inverter System at NREL

8. 8
DTT causes the immediate operation of a relay or recloser when an upstream breaker opens in
the electric distribution system. The substation generates a “trip” command, and a data
communications link carries that command to the breaker or recloser connecting the DER or
the DER system may receive the command and shutdown automatically. As DERs are often
located a considerable distance from the substation (where utility communications is typically
available) DTT communications can be challenging and costly. Also, as DERs become
increasingly common in today’s smart grid, DTT implementation are becoming more
numerous and multiple DTT communication nodes may be needed per distribution circuit.
Traditionally, communications to DTT-capable relays and reclosers use:
- leased copper line tone circuits with constant connection
- fiber-optics communication with direct connection
- microwave radio with direct channel, or
- serial narrow-band or proprietary radio links with direct channel
This test uses the private LTE system as the communications link between a command center
(i.e. a substation) and the recloser which disconnects a PV generator attached to the
distribution circuit. The project team evaluated two air-interface components:
- Coverage: Measure the impact of variation in signal strength and signal quality on
throughput and latency for the critical DTT application.
- Capacity: Measure the impact of various traffic congestion conditions under both best
efforts and prioritized traffic loading scenarios on throughput and latency for the
critical DTT application.
DTT Testbed
The project team has implemented a full communications and equipment test of a direct
transfer trip DTT application where a PV inverter is signalled to trip offline via the private
LTE network. The test measures the time required to communicate the signal and then
disconnect the inverter under various communication system scenarios (congestion,
prioritization, etc.). The PV inverter (100 kW in capacity) was configured to trip offline upon
receiving a direct DNP3 signal from an accompanying computer. The PV inverter was
connected to a PV simulator and AC grid connection to simulate connection to a nominal grid
operating under otherwise normal conditions (i.e. normal but for the communications signal
requesting immediate disconnection from the grid).

9. 9
Figure 2.10.1: Forecasted Demand per Source
(Source: NREL / Anterix P-LTE Testbed Configuration)
In the initial demonstration, the team measured in real-time the round-trip delay between the
computer and the communication’s module on the recloser attached to the PV inverter system.
The LTE air-interface signal strength and signal quality telemetry were also monitored in real-
time.
Legend
ACREDB – AC Research
Electrical Distribution
Bus (part of ESIF
capability)
CB – circuit breaker
EPO – Emergency Power
Off – a safety function
only used for lab
evaluations, not used in
utility domain

10. 10
Table: Direct Transfer Trip of PV inverter System Initial Test Results
Test
Case
Description Measured
round-
trip
Delay
(ms)
Communication
Link
Congestion
Configuration
Communication
Link Signal
Strength
Result
1 DTT of PV
inverter under
strong LTE
signal
coverage
20 – 40
ms
No congestion -65 to -75 dBm
RSSI
Opened circuit with
consistency
2 DTT of PV
inverter under
weak LTE
signal
coverage
50 – 90
ms
No congestion -90 to -100
dBm
Opened circuit with
consistency
3 DTT of PV
inverter under
congested LTE
channel (best
efforts – no
QoS)
80 – 600
ms
Fully loaded
downlink
resource
utilization with
background
traffic on same
cell
-65 to -75 dBm Inconsistent
behaviour ranging
among opened
circuit, opened
circuit with long
delay, opened
circuit with no
acknowledgement,
TCP/IP
communications
error, and no-trip
4 DTT of PV
inverter under
congested LTE
channel with
prioritized
traffic (QoS
enabled for
critical traffic)
20 – 40
ms
Fully loaded
downlink
resource
utilization with
background
traffic on same
cell
-65 to -75 dBm Opened circuit with
consistency
(Source: NREL / DOE High Impact Project Review, September 12, 2019)
Results show that under both strong and weaker LTE signal strength and quality, the DTT
application nonetheless operated with consistency and relatively low delay. Further
characterization of the delay will be tested to formulate an adequate LTE cell edge coverage
boundary. Results also show that under heavy downlink congestion, the traffic on the
command link from server to relay must be prioritized over the LTE air-interface for DTT to
operate reliably. To enable DTT functionality, the air-interface and network end-to-end traffic
plane must be configured with a dedicated QoS that is higher than that of other, less critical
traffic.
The final project report will quantify and characterize the reliability and performance of the
system under additional congestion loads and various LTE signal strength and quality
scenarios.

11. 11
The project team intends to further refine the DTT testing. It will incorporate one-way
latency measurement capabilities into the testbed and will measure the full end-to-end time to
trip from command sent (server-side) to circuit open (PV inverter relay). The measurements
will be made with external real-time computational resources such as an OPAL-RT using a
synchronized timing source.
ADMS Integration
The second stage of testing will utilize NREL’s ADMS Testbed. The ADMS Testbed will be
configured with the Holy Cross Energy (HCE) ADMS Use Case. Within this use case, the
project team will conduct and evaluate a range of experiments with various communications
settings/congestion levels. The HCE Use Case consists of simulation data for two days of
utility operation; one day is the system peak loading day (which occurs in the wintertime) and
the other is the peak PV generation day. The data for one hour from each of these days, during
which a large amount of communications and control actions occur, will be used to evaluate
the system in real-time on the ADMS Testbed. Both of the selected hours are representative of
critical operational periods for utilities, so latency and/or dropped packets in the
communications system will have a noticeable impact.
The simulation during these two hours of real-time evaluation includes a comprehensive
DERMS (Distributed Energy Resources Management System) control, which controls roof-
top PV systems, batteries, EV loads, HVAC loads, and electrical water heaters using a
previously developed real-time optimal power-flow algorithm. The DERMS interfaces with a
Survalent ADMS using only the SCADA module through which the DERMS control receives
voltage and feeder head (start-of-circuit) power measurements. The DERMS can control up to
six hardware devices including a three-phase PV inverter, two single-phase inverters with a
battery, and one EV charger. Within the HCE Use Case there are 161 controllable residential
loads, including a rooftop PV system, an HVAC system, and a water heater. Some loads also
include a battery energy storage system and EV chargers. The project team will simplify the
HCE Use Case slightly by limiting the number of real hardware end points it includes, thus
facilitating lab evaluation and scheduling.
Phase 2 testing will include evaluation of the air-interface performance under various
coverage and congestion scenarios.

12. 12
(Source: NREL / Anterix P-LTE Testbed Configuration Phase 2)
Follow-on Work
Data collected on this project will facilitate advances in distribution protection methods and
will enable additional, potentially cost-effective measures for ADMS and distribution
automation (DA) applications. The IAB will review these findings and perhaps propose new
use cases for grid operations.
Many utility trials have focused on existing DA applications using P-LTE communications in
the 900 MHz spectrum band. This project builds on that work, proving that P-LTE can enable
low-latency applications such as DTT on a PV inverter and similar systems.
Acknowledgements
This work was authored, in part, by Alliance for Sustainable Energy, LLC, the manager and
operator of the National Renewable Energy Laboratory for the U.S. Department of Energy
(DOE) under Contract No. DE-AC36-08GO28308. Funding was provided by U.S.
Department of Energy Office of Energy Efficiency and Renewable Energy via the Energy
System Integration Facility High-Impact Project (ESIF-HIP) designation of the Enabling
Realistic Communications Evaluations for ADMS (ERCEA) Project. The views expressed in
the article do not necessarily represent the views of the DOE or the U.S. Government. The
U.S. Government retains and the publisher, by accepting the article for publication,
acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable,
worldwide license to publish or reproduce the published form of this work, or allow others to
do so, for U.S. Government purposes.
BIBLIOGRAPHY
[1] Mather, B., Yuan, G., (2018). Going to the Next Level: The Growth of Distributed
Energy Resources, IEEE Power and Energy Magazine, v.16 issue 6.

13. 13
[2] Palmintier, B., et al., (2016). On the Path to SunShot: Emerging Issues and Challenges in
Integrating Solar with the Distribution System (NREL Technical Report No. NREL/TP-
5D00-65331). Golden, CO.
[3] Palmintier, B., et al., (2016). Feeder Voltage Regulation with High Penetration PV Using
Advanced Inverters and a Distribution Management System: A Duke Energy Case Study
(NREL Technical Report No. NREL/TP-5D00-65551). Golden, CO.
[4] https://www.nist.gov/programs-projects/smart-grid-communications-0, updated May 7,
2018
[5] https://www.telecomstechnews.com/news/2016/mar/15/opinion-4g-lte-and-its-benefits-
enterprise-networks/ , March 15, 2016
[6] https://gsacom.com/paper/status-lte-ecosystem-report-5614-lte-devices-announced-455-
suppliers/ , June 24, 2016
[7] https://www.epa.gov/energy/distributed-generation-electricity-and-its-environmental-
impacts , January 19, 2017
[8] Distributed Generation Direct Transfer Trip (DTT), URI Capstone Project 2016.
[9] CIGRE US National Committee 2018 Grid of the Future Symposium, Leveraging Private
LTE Networks in the Electric Utility, L. Greenstein
[10] ARS Technica. “Fire dept. rejects Verizon’s ‘customer support mistake’ excuse for
throttling” https://arstechnica.com/tech-policy/2018/08/fire-dept-rejects-verizons-customer-
support-mistake-excuse-for-throttling/ Jon Brodkin August 22, 2018
[11] National Institute of Standards and Technology. US Department of Commerce. “LTE
Security – How Good Is It?” https://csrc.nist.gov/CSRC/media/Presentations/LTE-Security-
How-Good-is-it/images-media/day2_research_200-250.pdf Michael Bartock, Jeffrey
Cichonski, Joshua Franklin