As the costs of fixed network AMR approach the costs of traditional mobile AMR solutions, utilities are beginning to pay more attention to fixed network AMR options. Advances in network design and
technology are transforming the landscape and opening up options not previously available.
The two most common radio fixed network designs are the “star” and the “mesh”.
Good: Star Networks
Most current fixed network AMR options could be categorized as “star” networks. In a star network, each meter communicates directly with a central hub. The hub uses a radio system, usually mounted on a light pole or tower since it must be in range of every meter. Star networks often require FCC-licensed frequencies operating at high transmission power to cover the long distances standing between the meter and the hub. Careful network planning and hub positioning are critical as it must address all current and potential sources of interference and obstruction. If any meter cannot “see” the hub in question, another hub must be added. Another issue for star networks is that unforeseen obstacles easily impair network performance. For example, an RV that is parked between a meter and the hub might interrupt communications as long as it is present.
Better: “Mesh” Networks
Mesh architectures consist of a network of meters each having the ability to transmit its own information as well as receive and relay information from neighboring meters. To join a mesh network, a meter need only “see” any neighboring meter. A mesh controller serves to collect information from a large number of meters, referred to as a “cluster”. Controllers are inexpensive and are typically mounted on utility poles. Unlike star networks, mesh network controllers only need to see one meter anywhere in the cluster for the network to operate. A key feature of a mesh network is the many different communication paths between any meter and the mesh controller. In the case of one or multiple failures, the mesh will automatically route around the failed segment. Thus mesh networks are inherently self-healing.
Mesh networks are also self-configuring. New meters automatically register themselves into the network without user intervention. In fact, adding meters to the mesh actually increases the number of paths for communication. This makes the mesh structure ever more robust and fault-tolerant.
However, not all mesh networks are created equal. While self-healing and self-configuring characteristics are common to most mesh networks, suitability for utilities will vary widely based on design specifics and a network’s intended application. Achieving reliable communications over long distances at moderate data rates in a large network is paramount and is what best distinguishes AMR networks from more common, standards-based offerings like Zigbee, WiFi, or Bluetooth. While these can be adapted for AMR applications, they are better suited for smaller, shorter range, higher data rate applications.
Best: AMR Mesh Networks
AMR mesh networks are designed from the ground up for the unique requirements of automatic meter reading.
A strong AMR mesh network is fully ad-hoc. This means that no particular arrangement of nodes or rigid deployment plan is needed to set up the network. While an AMR mesh has all of the inherent advantages of an ad-hoc network, its innovative architecture eliminates the complication and computational problems associated with routing tables. This is a major advantage as it lowers costs and keeps the network free from losses in communications associated with conflicts, jamming, and/or node failures.
Discovery of new meters within an AMR mesh is completely automatic. Data transmission, reliability, throughput, and other performance parameters are unaffected by the number of “hops” or ‘hopping distance” between the controller and its furthest node. An AMR mesh network is highly scaleable - out to literally
millions of endpoints.
A well-designed AMR mesh incorporates error-checking and correcting protocols to ensure high data integrity and maximum range. And due to the fact that most nodes will have multiple paths for the data, there should be an extremely low probability of missing data.
The use of Frequency Hopping Spread Spectrum (FHSS) techniques also maximizes range and reliability. Other spreading techniques such as DSSS are ideal for short-range radio links requiring continuous connection such as a cordless telephone or WiFi computer network, however for packet-based AMR networks, FHSS provides significantly improved range. Operating in the 900MHz unlicensed band also offers greater range than solutions operating at higher frequencies while eliminating the difficulty and expense of purchasing spectrum licenses from the FCC.
While it is important to ensure that all data is moved efficiently through the network, it is equally important that the data remain totally secure, safe from unauthorized parties. The strongest readily-available security measures use 128-bit encryption. This technique, combined with a frequency-hopping, spread-spectrum radio signal and digital packet structure, provides a level of security that customers and utilities can trust with their critical billing data.
A Summary of Key Requirements for Tomorrow’s AMR Mesh Networks
Range – Endpoints must have high sensitivity and power for long range and immunity to rain, foliage, and other obstacles. Look for “link budgets” of 130dB or better. Note: A link budget is an aggregation of positive and negative elements (including transmitter power, receiver sensitivity, and antenna efficiency) that indicate expected performance between any two points in a network. A budget of 130dB is enough to allow for fluctuations in the environment while still delivering consistent operation.
Scalability – A strong AMR mesh network must have the ability to add thousands, even millions, of metering points without extensive planning. The system must be able to have endpoints automatically register themselves into the network. Note: A mesh network only gets stronger and more fault-tolerant as more metering points are added. This is because more metering points mean more routing options to overcome obstacles and issues.
Unlimited “Hops” – It is imperative that an AMR network not have a hard-coded or a practical upper limit on the number of “hops” (transactions between points on the network) a meter’s signal can take. Unlimited hops ensures reliability by allowing signals to go wherever they must to make it back to the the controller.
This feature also reduces the planning burden as networks are expanded.
Dynamic Routing – AMR mesh networks must have the ability to immediately and dynamically adapt to an ever-changing RF environment. Factors that can influence RF propagation include position and size of vehicles in the area, new construction, seasonal foliage on trees, the ebb and flow of other RF traffic - pagers, wireless phones, baby monitors, etc.
Path Redundancy – The ability to send data over multiple simultaneous paths raises the reliability of a network. Intelligent code at the collector level discriminates between redundant and new data as it is received.
Survivability – A well-designed network should have the ability to instantly recover from meter failures / power outages and continue network communications without loss of data. This is usually done with some type of battery backup or capacitor. Because mesh networks use the individual metering points to relay information, it is important that they stay “up” and allow the mesh to continue to operate for a significant period of time even after power is lost as opposed to the older approach of sending a “last-gasp” transmission. This allows points at the edges of the network cluster time to relay their data before the network itself shuts down.
Thus, network operators have status reports from all points, even in an outage situation.
Congestion-Free – AMR network topologies are dictated by the layout of the communities they serve and must be immune to bottlenecks and other sources of congestion.
Security – Data security is of paramount importance. A secure AMR mesh network requires the strongest 128-bit encryption along with spread spectrum communications.
Reliability – Data integrity throughout the network must be ensured through advanced FEC error-correcting codes, 32-bit CRC error checking and other sophisticated software algorithms.
Interoperability – In order to maximize ROI, an AMR mesh network should support collection of water and gas as well as electric meter readings. The mesh approach is ideally suited for this as gas and water meters are typically within close enough proximity to be able to “hop” onto the network either on their own or via the electric meter. And while collecting a single utility on the network will probably yield a satisfactory ROI, being able to partner with the local water and/or gas utilities only makes it look even more attractive and will hasten the network’s transformation into a profit center.
Low Cost – To become mainstream, an AMR mesh network should narrow the significant cost gap that currently exists between mobile and fixed-base AMR solutions. This cost gap has historically been a barrier to utilities choosing fixed base over less expensive mobile AMR systems. As this gap closes, it should become more common for utility ROI’s to shift in favor of network AMR.
Flexibility – AMR mesh networks should support a variety of enterprise networking and software options and not force changes to billing or other systems. Support for current and emerging network communication standards helps the network fit well into more situations.
Power Management – Power management is critical for networks also carrying water and gas AMR applications. Water and gas meter interface units must operate for 10 years or more on a single battery. More frequent battery replacements will destroy otherwise attractive ROI models.
Upgradeability - Solutions must also support in-service software upgrades for future
enhancements. Updates and new features should be able to be “pushed” to metering endpoints without having to visit the sites.
Migration – A well-designed solution should support migration from walk-by to drive-by to cluster to full fixed network operations.
A Clear and Logical Migration Path
An AMR-specific mesh network offers a unique migration path for utilities interested in deploying walk-by or mobile metering now and moving towards full network operations.
Walk-by/Mobile: Endpoints in an AMR mesh network can be initially deployed and read in a walk-by or mobile mode using an inexpensive handheld computer or vehicle-based collector. At this stage, the system behaves no differently from a dedicated mobile AMR system. Although users will certainly want to continue their migration to greater levels of automation, the system could operate indefinitely using a walk-by or mobile AMR collection strategy.
Mesh clusters: This next step increases efficiency by deploying mesh controllers at the entrances to subdivisions, townhouse and gated communities, and closed communities such as military bases and airports. Mesh controllers automatically build a mesh cluster and collect the data from every meter in the cluster.
A vehicle-based reader can then collect all of the data for the mesh cluster of 1000 or more meters by simply driving to the mesh controller. Collection times are greatly reduced. Again, the system could also operate indefinitely in this mode.
Full Mesh: Full fixed network is achieved by deploying a backhaul capability from the mesh controllers to the utility. AMR Mesh controllers should support multiple backhaul options including WiFi; GPRS and other cellular data options; RS-232; POTS or even a secondary mesh network. Once connected to the utility, mesh controllers provide real-time alarms and data collection capabilities directly to a dedicated AMR server. Data should be stored in an industry standard SQL database for easy reporting and interfacing to billing, customer-service, and other enterprise software systems.
Summary
Mesh networks designed specifically for AMR are emerging as more “intelligent” and cost-effective ways of approaching utility data collection than traditional star network approaches. Networks designed from the ground up to overcome AMR’s most pressing challenges: transmission range limited by obstacles and interference, ease of installation, the need for high levels of redundancy and extremely low cost are poised to take a leading position in the next generation of automatic meter reading solutions.
About the Authors
Russell Herring is a product development expert and one of the pioneers of applied consumer
wireless technology. He joined Datamatic’s team in mid-2005 to oversee the engineering, development, technical research and testing of Datamatic’s innovative hardware and firmware products.
Russell has approximately 30 years experience in engineering, product management and engineering management with GPS systems, voice and data communications, telematics and wireless technology. He is an acknowledged leader in the development of GPS systems and holds four key patents for
wireless communications technology.
Russell also led the design team on an innovative full echo-canceling IBM ThinkPad modem and speakerphone system.
Russell is a graduate of Texas A&M University, where he earned a Bachelor of Science in Electrical Engineering. He served as an engineer at Datapoint Corporation, a San Antonio based
computer systems manufacturer. Russell’s expertise in engineering management was established during his tenure at Data Race, Inc. and ATX Technologies, Inc., where he excelled in budget
and facility management as well as research and development.
technology are transforming the landscape and opening up options not previously available.
The two most common radio fixed network designs are the “star” and the “mesh”.
Good: Star Networks
Most current fixed network AMR options could be categorized as “star” networks. In a star network, each meter communicates directly with a central hub. The hub uses a radio system, usually mounted on a light pole or tower since it must be in range of every meter. Star networks often require FCC-licensed frequencies operating at high transmission power to cover the long distances standing between the meter and the hub. Careful network planning and hub positioning are critical as it must address all current and potential sources of interference and obstruction. If any meter cannot “see” the hub in question, another hub must be added. Another issue for star networks is that unforeseen obstacles easily impair network performance. For example, an RV that is parked between a meter and the hub might interrupt communications as long as it is present.
Better: “Mesh” Networks
Mesh architectures consist of a network of meters each having the ability to transmit its own information as well as receive and relay information from neighboring meters. To join a mesh network, a meter need only “see” any neighboring meter. A mesh controller serves to collect information from a large number of meters, referred to as a “cluster”. Controllers are inexpensive and are typically mounted on utility poles. Unlike star networks, mesh network controllers only need to see one meter anywhere in the cluster for the network to operate. A key feature of a mesh network is the many different communication paths between any meter and the mesh controller. In the case of one or multiple failures, the mesh will automatically route around the failed segment. Thus mesh networks are inherently self-healing.
Mesh networks are also self-configuring. New meters automatically register themselves into the network without user intervention. In fact, adding meters to the mesh actually increases the number of paths for communication. This makes the mesh structure ever more robust and fault-tolerant.
However, not all mesh networks are created equal. While self-healing and self-configuring characteristics are common to most mesh networks, suitability for utilities will vary widely based on design specifics and a network’s intended application. Achieving reliable communications over long distances at moderate data rates in a large network is paramount and is what best distinguishes AMR networks from more common, standards-based offerings like Zigbee, WiFi, or Bluetooth. While these can be adapted for AMR applications, they are better suited for smaller, shorter range, higher data rate applications.
Best: AMR Mesh Networks
AMR mesh networks are designed from the ground up for the unique requirements of automatic meter reading.
A strong AMR mesh network is fully ad-hoc. This means that no particular arrangement of nodes or rigid deployment plan is needed to set up the network. While an AMR mesh has all of the inherent advantages of an ad-hoc network, its innovative architecture eliminates the complication and computational problems associated with routing tables. This is a major advantage as it lowers costs and keeps the network free from losses in communications associated with conflicts, jamming, and/or node failures.
Discovery of new meters within an AMR mesh is completely automatic. Data transmission, reliability, throughput, and other performance parameters are unaffected by the number of “hops” or ‘hopping distance” between the controller and its furthest node. An AMR mesh network is highly scaleable - out to literally
millions of endpoints.
A well-designed AMR mesh incorporates error-checking and correcting protocols to ensure high data integrity and maximum range. And due to the fact that most nodes will have multiple paths for the data, there should be an extremely low probability of missing data.
The use of Frequency Hopping Spread Spectrum (FHSS) techniques also maximizes range and reliability. Other spreading techniques such as DSSS are ideal for short-range radio links requiring continuous connection such as a cordless telephone or WiFi computer network, however for packet-based AMR networks, FHSS provides significantly improved range. Operating in the 900MHz unlicensed band also offers greater range than solutions operating at higher frequencies while eliminating the difficulty and expense of purchasing spectrum licenses from the FCC.
While it is important to ensure that all data is moved efficiently through the network, it is equally important that the data remain totally secure, safe from unauthorized parties. The strongest readily-available security measures use 128-bit encryption. This technique, combined with a frequency-hopping, spread-spectrum radio signal and digital packet structure, provides a level of security that customers and utilities can trust with their critical billing data.
A Summary of Key Requirements for Tomorrow’s AMR Mesh Networks
Range – Endpoints must have high sensitivity and power for long range and immunity to rain, foliage, and other obstacles. Look for “link budgets” of 130dB or better. Note: A link budget is an aggregation of positive and negative elements (including transmitter power, receiver sensitivity, and antenna efficiency) that indicate expected performance between any two points in a network. A budget of 130dB is enough to allow for fluctuations in the environment while still delivering consistent operation.
Scalability – A strong AMR mesh network must have the ability to add thousands, even millions, of metering points without extensive planning. The system must be able to have endpoints automatically register themselves into the network. Note: A mesh network only gets stronger and more fault-tolerant as more metering points are added. This is because more metering points mean more routing options to overcome obstacles and issues.
Unlimited “Hops” – It is imperative that an AMR network not have a hard-coded or a practical upper limit on the number of “hops” (transactions between points on the network) a meter’s signal can take. Unlimited hops ensures reliability by allowing signals to go wherever they must to make it back to the the controller.
This feature also reduces the planning burden as networks are expanded.
Dynamic Routing – AMR mesh networks must have the ability to immediately and dynamically adapt to an ever-changing RF environment. Factors that can influence RF propagation include position and size of vehicles in the area, new construction, seasonal foliage on trees, the ebb and flow of other RF traffic - pagers, wireless phones, baby monitors, etc.
Path Redundancy – The ability to send data over multiple simultaneous paths raises the reliability of a network. Intelligent code at the collector level discriminates between redundant and new data as it is received.
Survivability – A well-designed network should have the ability to instantly recover from meter failures / power outages and continue network communications without loss of data. This is usually done with some type of battery backup or capacitor. Because mesh networks use the individual metering points to relay information, it is important that they stay “up” and allow the mesh to continue to operate for a significant period of time even after power is lost as opposed to the older approach of sending a “last-gasp” transmission. This allows points at the edges of the network cluster time to relay their data before the network itself shuts down.
Thus, network operators have status reports from all points, even in an outage situation.
Congestion-Free – AMR network topologies are dictated by the layout of the communities they serve and must be immune to bottlenecks and other sources of congestion.
Security – Data security is of paramount importance. A secure AMR mesh network requires the strongest 128-bit encryption along with spread spectrum communications.
Reliability – Data integrity throughout the network must be ensured through advanced FEC error-correcting codes, 32-bit CRC error checking and other sophisticated software algorithms.
Interoperability – In order to maximize ROI, an AMR mesh network should support collection of water and gas as well as electric meter readings. The mesh approach is ideally suited for this as gas and water meters are typically within close enough proximity to be able to “hop” onto the network either on their own or via the electric meter. And while collecting a single utility on the network will probably yield a satisfactory ROI, being able to partner with the local water and/or gas utilities only makes it look even more attractive and will hasten the network’s transformation into a profit center.
Low Cost – To become mainstream, an AMR mesh network should narrow the significant cost gap that currently exists between mobile and fixed-base AMR solutions. This cost gap has historically been a barrier to utilities choosing fixed base over less expensive mobile AMR systems. As this gap closes, it should become more common for utility ROI’s to shift in favor of network AMR.
Flexibility – AMR mesh networks should support a variety of enterprise networking and software options and not force changes to billing or other systems. Support for current and emerging network communication standards helps the network fit well into more situations.
Power Management – Power management is critical for networks also carrying water and gas AMR applications. Water and gas meter interface units must operate for 10 years or more on a single battery. More frequent battery replacements will destroy otherwise attractive ROI models.
Upgradeability - Solutions must also support in-service software upgrades for future
enhancements. Updates and new features should be able to be “pushed” to metering endpoints without having to visit the sites.
Migration – A well-designed solution should support migration from walk-by to drive-by to cluster to full fixed network operations.
A Clear and Logical Migration Path
An AMR-specific mesh network offers a unique migration path for utilities interested in deploying walk-by or mobile metering now and moving towards full network operations.
Walk-by/Mobile: Endpoints in an AMR mesh network can be initially deployed and read in a walk-by or mobile mode using an inexpensive handheld computer or vehicle-based collector. At this stage, the system behaves no differently from a dedicated mobile AMR system. Although users will certainly want to continue their migration to greater levels of automation, the system could operate indefinitely using a walk-by or mobile AMR collection strategy.
Mesh clusters: This next step increases efficiency by deploying mesh controllers at the entrances to subdivisions, townhouse and gated communities, and closed communities such as military bases and airports. Mesh controllers automatically build a mesh cluster and collect the data from every meter in the cluster.
A vehicle-based reader can then collect all of the data for the mesh cluster of 1000 or more meters by simply driving to the mesh controller. Collection times are greatly reduced. Again, the system could also operate indefinitely in this mode.
Full Mesh: Full fixed network is achieved by deploying a backhaul capability from the mesh controllers to the utility. AMR Mesh controllers should support multiple backhaul options including WiFi; GPRS and other cellular data options; RS-232; POTS or even a secondary mesh network. Once connected to the utility, mesh controllers provide real-time alarms and data collection capabilities directly to a dedicated AMR server. Data should be stored in an industry standard SQL database for easy reporting and interfacing to billing, customer-service, and other enterprise software systems.
Summary
Mesh networks designed specifically for AMR are emerging as more “intelligent” and cost-effective ways of approaching utility data collection than traditional star network approaches. Networks designed from the ground up to overcome AMR’s most pressing challenges: transmission range limited by obstacles and interference, ease of installation, the need for high levels of redundancy and extremely low cost are poised to take a leading position in the next generation of automatic meter reading solutions.
About the Authors
Russell Herring is a product development expert and one of the pioneers of applied consumer
wireless technology. He joined Datamatic’s team in mid-2005 to oversee the engineering, development, technical research and testing of Datamatic’s innovative hardware and firmware products.
Russell has approximately 30 years experience in engineering, product management and engineering management with GPS systems, voice and data communications, telematics and wireless technology. He is an acknowledged leader in the development of GPS systems and holds four key patents for
wireless communications technology.
Russell also led the design team on an innovative full echo-canceling IBM ThinkPad modem and speakerphone system.
Russell is a graduate of Texas A&M University, where he earned a Bachelor of Science in Electrical Engineering. He served as an engineer at Datapoint Corporation, a San Antonio based
computer systems manufacturer. Russell’s expertise in engineering management was established during his tenure at Data Race, Inc. and ATX Technologies, Inc., where he excelled in budget
and facility management as well as research and development.
