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Mesh Networks – A Disruptive Technology
Wireless mesh network technology is a point-to-point, or peer-to-peer, system called an ad hoc, multi-hop network. A node can send and receive messages, and in a mesh network, a node also functions as a router relaying messages for its neighbors. Through the relaying process, a packet of wireless data will find its way to its destination, passing through intermediate nodes with reliable communication links.
True mesh networks are completely self-organizing in that nothing has to be done to provision the node (i.e. no IP address or physical location has to be assigned). Once a node is placed in the mesh network it immediately identifies its neighboring nodes and begins the communication process that ultimately registers the node with network management software.
A reliable, highly scalable network breaks the price functionality barrier necessary for device networks. The ability to scale reliably without extensive network management leads to a low cost solution. IP based networks are not suitable for large device networks because the hierarchical structure leads to extensive network management overhead and therefore high cost solutions.
Mesh AMR Network Architecture
In a wireless mesh network, meter nodes require no provisioning. Once the meter is installed, it simply identifies the network and the neighboring nodes to communicate information via a non-specified gateway to the back-office server. Information routing paths will change depending on local environment and meter nodes can communicate with any gateway depending on the most efficient routing path available. The system is truly self-organizing and self-healing as routing paths change to take into consideration wireless links that change.
Wireless mesh AMR solutions can integrate electric, gas and water meters in the same network and provide 15 minute-interval data for each meter node. Local storage at each meter node, automatic time synchronization, automatic re-organization around disrupted communication links, provide a powerful, complete, cost-effective and robust solution.
The general architecture of a mesh AMR network includes the following components:
- Wireless meters nodes
- Gateway
- Network Manager back-office software
Meter Nodes
The meter nodes form a self-organizing, self-managing and self-healing wireless mesh network that is managed through the gateway. Nodes report the collected interval data every 2 hours (programmable) to the gateway. Typically there are approximately 1,000 nodes per gateway.
Gateway
The gateway communicates with nodes and has sufficient local storage for several months of interval data from each node. Application software at the gateway recognizes gaps in data from any node due to temporary communication disruptions and will proactively request and obtain data from the nodes to fill in gaps. The gateway is connected to the back-office through standard IP connection or telephone modem.
Network Manager
Network Manager back-office software provides a graphical user interface to access the gateways, check on node status, and data reports from the nodes. Network Manager also provides for scheduled periodic collection of all data from the gateways and storage in a central database.
The salient points of a mesh AMR network that makes it attractive to utilities are:
- Reliability: The architecture of the system performs bidirectional intelligent routing and rerouting based on changing wireless communication links. Built in local storage at both nodes and gateways with intelligent recovery mechanisms ensure that data will not be lost even in the event of disruption of communications.
- Cost Effective: Extreme ease of installation; license-free spectrum; and relatively short-range radios; coupled with a large-scale network allows for low system cost.
- Data Value: Full interval data is provided from each meter point.
- Time Synchronization:The system integrates periodic time syncs to the nodes and maintains accurate time at each node.
- Integrated Framework: Electric, gas and water meters can all be integrated into the same network.
Mesh AMR Network System Cost
Meter Nodes
Because a mesh network meter node has similar components to a drive-by AMR meter (radio, memory, and microprocessor), hardware costs are similar. Meters for a mesh network will have a more capable microprocessor to run the complex operating system as well as more memory to deal with relaying of information but these costs are only slightly more than a drive-by AMR meter.
Gateways
Gateways are more complex than meter nodes with substantially greater amounts of memory and therefore cost more. It is important that gateways can manage a large number of meter node (1,000 or greater) thereby amortizing the cost of the gateway across a large number of units making the per-unit cost small.
Installation
After the planning phase which includes identifying clusters and installing gateways, the installation of mesh network enabled meters are simple and straightforward. Because of the self-organizing feature of a mesh network, installation costs are the same as changing a meter. Qualified electricians simple replace the existing meter with a mesh network enabled meter.
Summary
Self-organizing, self-managing and self-healing wireless network technology has been proven to work in both utility and commercial meter applications as evidenced by a utility that is currently operating a 3,600 meter node AMR mesh network and another electric utility is deploying a 35,000 meter node network. AMR mesh networks promise to provide the utility industry very robust functionality at prices approaching drive by systems because of the ability of meter nodes to relay information. This should usher in an era of greater information for utility and customers to better respond to changing prices as well as more efficiently manage their energy usage.
