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AMI Part 3 -- Technology Basics

John Benson's picture
Senior Consultant Microgrid Labs

PROFESSIONAL EXPERIENCE: Microgrid Labs, Inc. Senior Consultant: 2014 to Present Developed product plans, conceptual and preliminary designs for projects, performed industry surveys and...

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  • May 8, 2018


The first paper in this series, Roots, can be accessed via the link below.

The second paper in this series, Creating Demand (for AMI), can be found through the link below:

An advanced metering infrastructure (AMI) system is rather complex. Each system architecture has at least two, and sometimes three separate networks.

The top layer is public network (generally TCP/IP). This layer is called a wide area network (WAN), and sometimes a backhaul network.

The second layer is proprietary to the AMI vendor's design, and the third layer (if there is one) uses a standard design. With the latter, it appears that ZigBee is winning this battle, at least among AMI systems. With systems that have a third layer, this extends the AMI system firmly into the general Internet of Things (IoT).

Think of a normal detached home. The top two layers of AMI get the network to the electricity meter that is (frequently) on the side of the home. Sometimes it also goes to the gas and water meters, but the electronics for these are generally battery-powered, so these might use the third layer or a separate low-power second layer.

Adding a third network layer designed to penetrate the home can extend this network to devices in the home, especially energy-related devices like heating ventilation and air conditioning (HVAC) thermostats. The commands and information sent to and received from these devices are simple so this third layer can be slow, but it must be secure, and inexpensive. Some devices in this layer are battery-powered, so it should be low-power.


The three networks are described below.

2.1. Wide Area Network

A given WAN might potentially spread and gather information from the entire AMI system. With the exceptions being systems for really large utilities like my utility, PG&E (statistics below):[1]

  • Service area (map) covers about half of California.
  • 106,681 circuit miles of electric distribution lines and 18,466 circuit miles of interconnected transmission lines.
  • 42,141 miles of natural gas distribution pipelines and 6,438 miles of transportation pipelines.
  • 5.4 million electric customer accounts.
  • 4.3 million natural gas customer accounts.

Other utilities may have fragmented WAN service-providers in the utility's territory. Thus some utilities may need to use multiple carriers for coverage, or the best pricing.

The technologies that may be used include:

  • Wired (and/or optical) networks offered by telephone carriers (like AT&T)
  • Wired (and/or optical) networks offered by cable carriers (like Comcast)
  • Optical (mainly, but also satellite) networks offered by network service providers (like Cogent Communications)
  • Wireless networks (like Verizon)

It should be noted the wireless networks use wired/optical network service to connect their cell-masters to each other and to their internal networks.

2.2.Neighborhood Area Network

Although this layer will be called a neighborhood area network herein, it is also called a field area network, personal area network, and other names. The neighborhood area network (NAN) uses a proprietary design to get from either the wireless AMI transceiver (for wireless NANs) or the distribution substation (for power-line carrier (PLC) NANs) to the electric meters (also gas meters and/or water meters, but note these cannot directly use PLC).

When I was in this market, and was last interested in other vendors (2004 or 2005) it seemed like there were 10 or 15 vendors. These fell into two categories: Contenders: product not yet fully developed, and (2) Legacy vendors: product fully developed, but not suitable for future AMI. I just completed a pretty thorough search, and it appears that these have consolidated to just four major market-participants and three minor participants. The most interesting thing about these is that three of them (first subsections below) have similar technologies in that all three offer both wireless and power line carrier. The seven subsections below cover these participants.


Based on acquisitions, market share and partnerships, Itron should end up being a big winner in this market. They have acquired SmartSynch, Comverge (both my former associates) and most recently (last fall) Silver Springs Networks. The latter appears to have been largely successful when Itron purchased them.

Technology: Both Itron and Silver Springs appear to be focused on using an IEEE 802.15.4g wireless standard for their future products. This network standard, called the Smart Utility Networks (SUN), "…provides a global standard that facilitates very large scale process control applications such as the utility smart-grid network capable of supporting large, geographically diverse networks with minimal infrastructure, with potentially millions of fixed endpoints."[2] See the reference and also see the links below. This standard is being promoted by the WiSUN Alliance (second link below). Both Itron and Silver Spring, as well as Landis+Gyr are "Promoter" members of the Alliance.

This appears to be a mesh technology, potentially requiring multiple hops to get from the WAN interface to a given device. This trades longer latencies for resilience (self-healing) and ubiquitous coverage. This standard uses Internet Protocol (IP), version 6 (IPv6), and most IP implementations use multiple hops to get from the source to the destination.

Silver Springs Network's implementation of this standard is called Starfish. They also offer a low power version of it (called Milli, for battery powered devices) and a method for retrofitting legacy devices with Starfish network interfaces.

Itron's implementation of the above standard is called OpenWay® Riva. There are two interesting features for their Adaptive Communications Technology Module for this technology: (1) it apparently it has provisions for powerline carrier (PLC) communication (not supported by 802.15.4g), and (2) It was developed in partnership with Cisco, who also developed Cisco 1000 Series Connected Grid Routers. As a major component of an OpenWay network.

I know Silver Springs offers support for a ZigBee HAN, and I would guess that OpenWay does also. See the PG&E link below and section 2.2.2 below (for a discussion of ZigBee).

Projects: The following are a sample of major projects. Instead of describing these below, I provided links to articles describing them.

ComEd (Silver Springs):

CenterPoint Energy (OpenWay):

SCE (above link, OpenWay)

SDGE (above link, OpenWay)

PG&E (Silver Springs)

OG&E (Silver Springs)


I was an employee of Landis & Gyr for about 17 years, until I moved over to Siemens in the middle of the Siemens acquisition of Landis & Gyr (the late 1990s). After Siemens sold the Meter division of what was formerly Landis & Gyr to KKR a few years later, it changed its name to Landis+Gyr.

Landis+Gyr has been involved in the AMI industry since the beginning. In 2006, its then owner (The Bayard Group) purchased CellNet from GTCR Golder Rauner. At that time CellNet had the largest installed base of communicating meters. These used a one-way RF communication technology to remotely read the meters (called automatic meter reading or AMR). Bayer also purchased Hunt Technologies in 2006, another AMR vendor. Hunt used power line carrier technology (PLC). Both of these companies were merged with Landis+Gyr.

The former customers of CellNet and Hunt are still supported by Landis+Gyr, and the CellNet technology has evolved to support a competitive AMI feature set. This design is called Gridstream RF Mesh, and uses the unlicensed 902-928 MHz ISM RF Band for its NAN. It also offers a ZigBee 2.4 GHz Home Area Network (HAN, also called a personal area network or PAN) in the meter as a subnetwork in addition the primary NAN. ZigBee is another IEEE 802.15.4, but not the IEEE 802.15.4g, Smart Utility Networks (SUN). Landis+Gyr is a member of the ZigBee Alliance (link below).

Since Landis+Gyr is a Promoter member of WiSUN Alliance, I expect they are evolving their NAN technology to this standard.

The PLC network used by Landis+Gyr is the TS2 technology originally developed by Hunt (I believe under development when Bayard acquired them). Hunt's original technology was called Turtle (TS1) because it was slow, but reliable.

Projects: The following is a sample of projects with links to articles describing them.


United Illuminating


Southwest Tennessee EMC (PLC System)

Western Indiana Energy (PLC System)


Aclara has been a dominant manufacturer of PLC AMI systems. These systems are quite different from most RF systems, especially mesh systems. Whereas RF systems require a certain density of meters (per square-mile) in order to be cost-effective. Since PLC systems follow the power distribution network, this is not a consideration. For most urban environments, RF mesh system work fine, in most cooperatives and small municipal systems, PLC is probably a better fit. Note that some utilities have parts of their service area that have very low population-densities and thus are better served by PLC systems.

Aclara's primary NAN is Two-Way Automatic Communication System (TWACS) technology. This is a full-featured power-line carrier technology. In addition Aclara offers two additional technologies:

Synergize RF Communications Network provides two-way communications for water, gas and electric utilities. This network seems to offer a full range of AMI features. The network employs licensed 450-470-MHz radio frequencies for all inbound and outbound communications between data collectors and endpoints. This appears to use a single hop with low latency vs. mesh networks with multiple hops. I believe this was formerly the STAR Network from Hexagram. This is a proven low-power AMR system that has been around since 1984. Apparently Aclara acquired this technology around 2006.

Synergize Metrum Cellular LTE came through an acquisition of Metrum. This uses a digital cellular network, and also appears to offer a full range of AMI features.

At least some of the Aclara network meters offer ZigBee HAN technology for linking to other devices.

Projects: The following is a sample of projects with links to articles describing them.



DC Water  

Dothan Utilities

Piqua, Ohio


Sensus calls its NAN FlexNet®. This uses a dedicated licensed RF channel with a single hop. Since FlexNet provides service to gas and water end-points (in addition to electric meters, lighting and other devices) it needs to have a low-power implementation for battery-powered devices. They also offer ZigBee networking for linking devices in to FlexNet end-points. They have ZigBee implementations for devices used for demand response including thermostats, pool pumps, electric hot-water heaters, and possibly others. Sensus is a member of the ZigBee alliance.

Sensus is owned by Xylem (purchased in 2016), Xylem is mainly in the water-utility products and service industry. Although Sensus has reasonable offerings for the electric-utility market, we might expect them to focus more on water in the future.

Projects: The following is a sample of projects with links to articles describing them.

Cobb EMC



City of Azusa  

Dickson Electric System


Honeywell - Elster (hereafter "Elster") calls its NAN Energy Axis. This is a mesh network that uses the 902-928 MHz ISM RF Band. The primary network protocol for their latest version of Energy Axis is TCP/IP, and they use 128-bit encryption. Elster offers a low-power version of the network for water and gas devices, and a ZigBee HAN for extension of Energy Axis to communicate with IoT devices.

Elster has deployed 110 systems world-wide with 5.4 Million end-points.

Projects: The following is a sample of projects with links to articles describing them.

Salt River Project


Navajo Tribal Utility Authority

City of Fort Collins

Idaho Falls Power  

Silicon Valley Power


Trilliant offers two network technologies. The original technology is Secure Mesh. As the name suggests, this is a mesh architecture operating in the 2.4 GHz unlicensed band. The network standard is IPv6 conforming to IEEE 802.15.4g (Smart Utility Networks (SUN)) and Trilliant is a Contributor member of the WiSUN Alliance.

The other network is Random Phase Multiple Access (RPMA®) that came from Ingenu, an IoT vendor in San Diego. The deal was put together in 2015, and was a combination of an acquisition (Trilliant acquired Ingenu’s smart grid application business) and licensing (of RPMA by Trilliant).

RPMA is a low data rate / high capacity network that provides wide area coverage, and uses a single hop over a 2.4 GHz unlicensed RF band. RPMA conforms to IEEE 802.15.4k. For more information of this technology go through the link below. This technology appears to be focused on low-power applications.

Trilliant offers a ZigBee HAN connectivity via a digital cellular (GPRS) Trilliant Communications Hub. They also have demonstrated connectivity to their Secure Mesh via a Micro Access Portal (MAP). Trilliant is a member of the ZigBee Alliance.

Projects: The following is a sample of projects with links to articles describing them.

Central Maine Power

Hydro One

Jamaica Public Service  

Louisville Gas and Electric



The Tantalus Utility Network (TUNet®) apparently can use either a direct connection via 220 MHz RF or a mesh network via 902-928 MHz ISM RF Band. Regarding their mesh network, Tantalus indicates it is self-healing, but they also say in normally only uses a single path to each node. In a diagram they show multiple hops. They also indicate that each end-point is self-initiating, which leads me to believe that the self-healing process involves a timeout-reinitiate cycle. They also offer hybrid networks consisting of 220 MHz (or IP) WAN and their IP-mesh network. Also offered are ZigBee (or WiFi) thermostats, smart-plugs and load control switches.

Projects: The following is a sample of projects with links to articles describing them.

EPB Chattanooga

Electric Cities of Georgia

Marietta Power and Water

People’s Energy Cooperative et al

3.Functions Supported

Automatic meter reading (AMR) was the predecessor of advanced metering infrastructure (AMI). As such AMR simply made monthly meter reading more efficient and less labor-intensive than a meter reader walking to each meter and writing the reading. Below are additional functions that AMI provides. I've grouped these into three subsections for (1) functions directly related to the metering function, (2) other energy-related functions, and (3) functions that go beyond energy.

3.1.Metering Functions

Electric load profile – daily or on-demand retrieval: Load profiles and how they can drive demand response were covered in the first two papers in this series. Prompt retrieval of profiles when required probably have the greatest value for utilities, regulators and the public vs. other AMI functions.

Water and gas AMR: Since water and gas can be stored, the price per unit is linear over time. Intervals are not required, and a monthly read is adequate.

Remote disconnect: one of the highest service cost for electric utilities is managing customers that pay their bills late or not at all. The ultimate remedy is to disconnect power, but doing this manually is both very labor intensive, and potentially dangerous (read: irate customers). Residential AMI meters can be equipped with a remotely actuated disconnect, eliminating these issues.

Prepay metering: Dealing with same problem as remote disconnects, prepay metering takes this one step further, is much better for the consumer, but complex in implementation. I worked with prepay metering products when I was with Siemens. In addition to remote disconnects, prepay requires (1) a method to transfer payments made from the payment office to the in-residence terminal-meter system and (2) a running amount of credit-remaining displayed on this terminal. AMI makes these processes much more convenient.

3.2.Other Energy-Related Functions

Active demand response / load control: By active I mean that the system can assertively reduce loads during a utility's peak demand periods. For most utilities this is by cycling air-conditioning compressors and (if present) pool pumps during hot periods. This works for customers because the in-home temperature rises very slowly for a few hours. Customers usually receive a credit on their electric bill for accepting this.

Communication with energy-related devices: Although this function can be used with the prior application, today it is more likely used with price-responsive demand-response (via a tiered tariff as described earlier) and controlled by the customer. The customer should also be able to see his recent (last interval) consumption in a user-friendly format (like dollars per hour). Devices controlled include:

  • Thermostats
  • Simple high-tariff alert devices
  • Customer messaging devices
  • Smart appliances and plugs

The communication systems for these typically use home area networks (HANs), and thus go well into the Internet of things (IoT).

Distribution automation: This is mostly an extension of SCADA, and has been around almost as long. Currently wide-area networks (as described above, and to include digital cellular) are generally used for communication for a number of reasons, including high-security, low latency and high-reliability. Distribution devices monitored and controlled include switches, transformers, fuses and disconnects.

Outage management: All or virtually all AMI systems can detect when each end-point / meter loses power. Thus they can provide notification of a power outage, its extent, and the extent of restoration. This speeds up utility response, and more efficiently uses labor.

3.3.Non-Energy Functions

Water leak management: The most advanced of these systems use acoustic sensors in the water network to localize leaks. Also metering water flow at several points in the network and at each consumer, could provide similar functions, but this might require something like profile metering.

Water and gas network pressure monitoring: This detects over- or under-pressure in these networks, and alerts the utility to these anomalous conditions.

Non-utility IoT transport: Any AMI system-owner can offer communication service to anyone needing communication to distributed devices. The one that I see mentioned most frequently is lighting control systems (public area / street lighting), although there are probably many more candidates.


[2] IEEE 802.15 WPAN Task Group 4g (TG4g), Smart Utility Networks.

John Benson's picture
Thank John for the Post!
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Paul Alvarez's picture
Paul Alvarez on Feb 4, 2020


Once the decision has been made to go with RF mesh, I understand the advantages of an RF mesh with IP.  But is IP strictly required for AMI?  There are plenty of RF mesh networks installed for AMI without IP, correct?




John Benson's picture
John Benson on Feb 4, 2020

Yes - Older ones (AMR) are not IP. When RF data networks were in their infancy, ditto IP, and the latter had too much overhead for the low efficiency of the former.

However, by Y2K when my primary experience with AMI started, all of the "modern" RF networks (like Silver Springs Network, now part of Itron) used IP.



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