Recently, two of the major suppliers of automatic meter reading equipment (AMR) both demonstrated new mesh networks in St. Louis at the annual AMRA international symposium. Something must be afoot if both Elster Electricity and Landis+Gyr, two of the industry’s predominant meter manufacturers, have made similar technology decisions in favor of developing mesh networks. What is this concept called “mesh” and what are its advantages in AMR?
Mesh refers to a geographic communications pattern that looks like a fishing net made from knots and links. In a typical wireless mesh network, the knots are meter sites and the links are the radio paths between the meter sites and a neighborhood concentrator. Using mesh communications technology, any knot in the communications chain can link to any other knot and it is up to the network to calculate an optimum path by hopping from meter to meter until the radio message eventually reaches a concentrator.
This mesh communications architecture is different from many older types of radio based meter reading technologies requiring extensive network infrastructures. “My clients are increasingly interested in mesh network communications for AMR applications”, states Ed Finamore, President of ValuTech Solutions, an AMR consulting firm. “The unique message routing characteristics of mesh technology have significantly improved the economics of fixed network deployment, while at the same time supporting time-of-use metering, remote disconnect services and other advanced features.”
Until now, the most common form of radio AMR has been through a single hop configuration from a meter to a mobile concentrator in a van or a handheld device. This single hop pattern is also seen in wireless fixed networks where the concentrator is mounted on a pole located in each neighborhood. The meter reading messages make a single hop from the house to the van or pole. Concentrators then typically use a phone line or cellular call to send data from the pole to headquarters. A second, or “double hop” is sometimes found in apartment house sub-metering systems where a radio repeater is used to get a message from the most remote apartments to the concentrator. These types of configurations greatly limit the network’s ability to deliver data through the network in near real time.
A major problem with single hopping or double hopping is that if the radio signal is weak, another expensive concentrator or repeater becomes necessary to make the system communicate properly. In addition to being expensive and, to some extent, redundant, adding additional repeaters creates deployment issues that can significantly increase the costs of network deployment. A meter read used for billing purposes is low value data worth, say, one or two dollars a month. While AMR equipment located inside the meter may cost less than $US 50, an additional concentrator on a pole can cost $US 3,000 to $4,000 for equipment, installation, and broad band connection.
Sharon Allan, Director of Strategic Initiatives and Relations at US Elster says, “Mesh networks will allow us to reach the economic price point where fixed radio AMR becomes viable for utilities”. Elster and its predecessors in the ABB metering line considered many AMR technologies. She continues, “Mesh allows us to group more nodes around a concentrator and link nodes across greater distances. Mesh also increases network reliability as each node also functions as a repeater”. Since Elster already had a line of meters with a communications port for a broad band connection, they adapted this meter to become the network’s neighborhood concentrator. In Elster’s mesh, the entire radio infrastructure is contained inside the meters. No poles are required.
The military developed much of the foundation technology for mesh networks which have been deployed to network individual soldiers, and for use as sensors scattered on the ground. The core principle of the mesh or “peer-to-peer” network is that nodes broadcast their presence to find what other nodes are nearby and which of these nodes they can communicate with. Each node then constructs a routing table listing the other nodes which are best situated to pass a message on, including who is next best. These routing tables are dynamically updated to account for new nodes or nodes temporarily lost behind various obstructions such as wet leaves. There are many variations of the routing algorithms in use as each technology company fielding a mesh network approaches the problem in a different way. One difference is whether a message can be addressed across the network to any other node or if messages seek only a specific route to the concentrator.
Much more overhead messaging, information processing, and trial and error communications are needed to operate a true “any peer to any peer” network. A network design seeking the nearest concentrator can in a sense be visualized as a funnel. A message entering the top of the funnel does not know the whole route to the bottom, but it does know who is lower down the funnel at each hop and it arrives soon enough at the bottom. Nodes configured in this scheme accept a message, look up their associated routing table, and then pass the message along. The store and forward routine being used can take from almost no time to half a second depending on the speed of the microprocessor in the meter.
Landis+Gyr uses data forwarding algorithms licensed from their partner, StatSignal Systems. Ember.com, an offspring of the MIT Media Lab, creates a new look-up table for every message. And there is also an open source group called the ZigBee.org Alliance developing a standard protocol dubbed IEEE 802.15.4 For the most part, radios like ZigBee operate at low power in the unlicensed bands: 915 MHz in the US, 868 MHz in Europe, and 2.4GHz globally. Lower powered, unlicensed technologies will typically range from 30 to 300 meters between nodes. However, licensed, two watt radio bands for Wireless Wide Area (WWAN) networks, used primarily in commercial and industrial metering applications, can extend their range to 15 kilometers or more per hop.
In today’s residential metering solutions, unlicensed radios are the norm. As long as the transmitters meet the communications specifications to prevent interference, a utility may deploy millions of unlicensed wireless meters. While the advantage is ease of deployment, the penalty is low wattage and hence short range. The range limitations of unlicensed radio have until now limited the build-out of fixed wireless AMR.
Typically there are a few meters that cannot reach the concentrator. They may be located on the wrong side of the house or are just too far away. As mentioned above, until mesh was developed, the only fixed network remedy for missed meters was to install an expensive additional concentrator. With mesh, a distant meter need only talk to a meter located closer to the center, which in turn talks to the concentrator. If a message is blocked to the East, it may find a suitable node to the South at which point it can then again hop East. Different manufacturers have adopted different norms for the number of hops and number of addresses served by each concentrator. Since each hop introduces a statistical chance of failure, use of too many hops is not a good idea. System reliability appears to be highest with three or four hops. More hops may begin to introduce error.
Many advanced metering applications lie on our horizon. Recent blackouts in Europe and North America are a reminder that wholesale deregulation and economic growth have put the electric grid under great stress. Time-of-use metering, real-time pricing, demand response, and other efficiency measures may provide a better return on investment and reliability than simply building more transmission lines or generation. However, each of these actions requires more meter data to be delivered closer to real-time. The inevitable future of the meter is to assume a greater role as an energy manager as well as a cash register. This cannot be done with drive-by AMR and will ultimately tip the economic scale to real-time AMR provided over fixed networks. While some of these networks may use power line carrier technology, wireless mesh networks appear inherently simpler than PLCs and should see an increasing level of deployment. The AMR market research firms are telling us that AMR has entered the mass market stage and will begin to rapidly penetrate the market from twenty percent of meters to over 70%. Mesh networks are one of many AMR technologies that appear to have turned a corner. One California group is shopping hard for AMR systems, but is only looking among mesh network technologies.
About the Author
Gerald Mimno is CEO of Advanced AMR Technologies, LLC where he writes extensively on harvesting value from meter data. He invites comments at gmimno@AdvancedAMR.com
Captions
(Green Illustration)
“A mesh net needs fewer expensive concentrators than a star net”
(Blue Illustration)
“The microprocessor in a star net is programmed with a fixed configuration telling the radio transmitter who to talk to. The micro in a mesh net continuously discovers who is nearby and sets up a dynamic routing table to optimize a route to the concentrator”.
Mesh refers to a geographic communications pattern that looks like a fishing net made from knots and links. In a typical wireless mesh network, the knots are meter sites and the links are the radio paths between the meter sites and a neighborhood concentrator. Using mesh communications technology, any knot in the communications chain can link to any other knot and it is up to the network to calculate an optimum path by hopping from meter to meter until the radio message eventually reaches a concentrator.
This mesh communications architecture is different from many older types of radio based meter reading technologies requiring extensive network infrastructures. “My clients are increasingly interested in mesh network communications for AMR applications”, states Ed Finamore, President of ValuTech Solutions, an AMR consulting firm. “The unique message routing characteristics of mesh technology have significantly improved the economics of fixed network deployment, while at the same time supporting time-of-use metering, remote disconnect services and other advanced features.”
Until now, the most common form of radio AMR has been through a single hop configuration from a meter to a mobile concentrator in a van or a handheld device. This single hop pattern is also seen in wireless fixed networks where the concentrator is mounted on a pole located in each neighborhood. The meter reading messages make a single hop from the house to the van or pole. Concentrators then typically use a phone line or cellular call to send data from the pole to headquarters. A second, or “double hop” is sometimes found in apartment house sub-metering systems where a radio repeater is used to get a message from the most remote apartments to the concentrator. These types of configurations greatly limit the network’s ability to deliver data through the network in near real time.
A major problem with single hopping or double hopping is that if the radio signal is weak, another expensive concentrator or repeater becomes necessary to make the system communicate properly. In addition to being expensive and, to some extent, redundant, adding additional repeaters creates deployment issues that can significantly increase the costs of network deployment. A meter read used for billing purposes is low value data worth, say, one or two dollars a month. While AMR equipment located inside the meter may cost less than $US 50, an additional concentrator on a pole can cost $US 3,000 to $4,000 for equipment, installation, and broad band connection.
Sharon Allan, Director of Strategic Initiatives and Relations at US Elster says, “Mesh networks will allow us to reach the economic price point where fixed radio AMR becomes viable for utilities”. Elster and its predecessors in the ABB metering line considered many AMR technologies. She continues, “Mesh allows us to group more nodes around a concentrator and link nodes across greater distances. Mesh also increases network reliability as each node also functions as a repeater”. Since Elster already had a line of meters with a communications port for a broad band connection, they adapted this meter to become the network’s neighborhood concentrator. In Elster’s mesh, the entire radio infrastructure is contained inside the meters. No poles are required.
The military developed much of the foundation technology for mesh networks which have been deployed to network individual soldiers, and for use as sensors scattered on the ground. The core principle of the mesh or “peer-to-peer” network is that nodes broadcast their presence to find what other nodes are nearby and which of these nodes they can communicate with. Each node then constructs a routing table listing the other nodes which are best situated to pass a message on, including who is next best. These routing tables are dynamically updated to account for new nodes or nodes temporarily lost behind various obstructions such as wet leaves. There are many variations of the routing algorithms in use as each technology company fielding a mesh network approaches the problem in a different way. One difference is whether a message can be addressed across the network to any other node or if messages seek only a specific route to the concentrator.
Much more overhead messaging, information processing, and trial and error communications are needed to operate a true “any peer to any peer” network. A network design seeking the nearest concentrator can in a sense be visualized as a funnel. A message entering the top of the funnel does not know the whole route to the bottom, but it does know who is lower down the funnel at each hop and it arrives soon enough at the bottom. Nodes configured in this scheme accept a message, look up their associated routing table, and then pass the message along. The store and forward routine being used can take from almost no time to half a second depending on the speed of the microprocessor in the meter.
Landis+Gyr uses data forwarding algorithms licensed from their partner, StatSignal Systems. Ember.com, an offspring of the MIT Media Lab, creates a new look-up table for every message. And there is also an open source group called the ZigBee.org Alliance developing a standard protocol dubbed IEEE 802.15.4 For the most part, radios like ZigBee operate at low power in the unlicensed bands: 915 MHz in the US, 868 MHz in Europe, and 2.4GHz globally. Lower powered, unlicensed technologies will typically range from 30 to 300 meters between nodes. However, licensed, two watt radio bands for Wireless Wide Area (WWAN) networks, used primarily in commercial and industrial metering applications, can extend their range to 15 kilometers or more per hop.
In today’s residential metering solutions, unlicensed radios are the norm. As long as the transmitters meet the communications specifications to prevent interference, a utility may deploy millions of unlicensed wireless meters. While the advantage is ease of deployment, the penalty is low wattage and hence short range. The range limitations of unlicensed radio have until now limited the build-out of fixed wireless AMR.
Typically there are a few meters that cannot reach the concentrator. They may be located on the wrong side of the house or are just too far away. As mentioned above, until mesh was developed, the only fixed network remedy for missed meters was to install an expensive additional concentrator. With mesh, a distant meter need only talk to a meter located closer to the center, which in turn talks to the concentrator. If a message is blocked to the East, it may find a suitable node to the South at which point it can then again hop East. Different manufacturers have adopted different norms for the number of hops and number of addresses served by each concentrator. Since each hop introduces a statistical chance of failure, use of too many hops is not a good idea. System reliability appears to be highest with three or four hops. More hops may begin to introduce error.
Many advanced metering applications lie on our horizon. Recent blackouts in Europe and North America are a reminder that wholesale deregulation and economic growth have put the electric grid under great stress. Time-of-use metering, real-time pricing, demand response, and other efficiency measures may provide a better return on investment and reliability than simply building more transmission lines or generation. However, each of these actions requires more meter data to be delivered closer to real-time. The inevitable future of the meter is to assume a greater role as an energy manager as well as a cash register. This cannot be done with drive-by AMR and will ultimately tip the economic scale to real-time AMR provided over fixed networks. While some of these networks may use power line carrier technology, wireless mesh networks appear inherently simpler than PLCs and should see an increasing level of deployment. The AMR market research firms are telling us that AMR has entered the mass market stage and will begin to rapidly penetrate the market from twenty percent of meters to over 70%. Mesh networks are one of many AMR technologies that appear to have turned a corner. One California group is shopping hard for AMR systems, but is only looking among mesh network technologies.
About the Author
Gerald Mimno is CEO of Advanced AMR Technologies, LLC where he writes extensively on harvesting value from meter data. He invites comments at gmimno@AdvancedAMR.com
Captions
(Green Illustration)
“A mesh net needs fewer expensive concentrators than a star net”
(Blue Illustration)
“The microprocessor in a star net is programmed with a fixed configuration telling the radio transmitter who to talk to. The micro in a mesh net continuously discovers who is nearby and sets up a dynamic routing table to optimize a route to the concentrator”.
