In a rapidly evolving utility landscape, advanced metering infrastructure (AMI) has emerged as an attractive solution for organizations seeking to enhance connectivity and transform their infrastructure into smart infrastructure.
As AMI adoption has accelerated, electric service providers have a choice of networks to power their smart grid communications:
- Privately licensed spectrum signals carried over a point-to-multipoint network architecture
- Publicly available spectrum signals carried over a mesh network architecture
The two approaches differ in architecture and signal type and offer distinct benefits and features for utilities. When selecting and designing a wireless communication network, utilities must compare, contrast and evaluate the two approaches as they relate to their unique challenges and needs. Conducting a thorough examination of architectural impacts, signal attributes, business and regional challenges, as well as other factors impacting wireless utility communications, will help utilities make smart choices when investing in AMI.
In this article, we examine the distinction between point-to-multipoint and mesh networks.
Point-to-multipoint vs. Mesh: Key Differences
While mesh and point-to-multipoint networks both offer advantages for utilities, key differences exist that point to distinct advantages.
Architectural approaches
Mesh and point-to-multipoint are two distinct architectural approaches to two-way radio communication networks. In a mesh network, many radios (also referred to as endpoints) can talk to each other, peer-to-peer. Each point on the network can receive, store and transmit signals to other points in many directions. In a point-to-multipoint network, there is a “master/hand” relationship in which a single point can talk to all the other points individually, and they can talk back to it—but not to each other.
Privacy
All mesh networks use unlicensed spectrum for their communications channel. They operate on public, not private channels. Often referred to as the industrial, scientific and medical (ISM) frequency band, this spectrum is shared with a wide range of devices including cordless telephones, baby monitors and wireless Internet access modems.
Licensed spectrum networks are private. Government regulators lease or sell use of an assigned bandwidth range which may only be used by a specific licensed user in a particular region. Interference is not tolerated within that region and is protected by government agency enforcement.
Interference
Unlicensed mesh networks often have a high noise floor. A noise floor is like people talking during a movie; due to the number of voices being heard, understanding what’s being said during the movie becomes more difficult. When industrial, institutional and medical devices are all sharing spectrum, the noise floor is high. With more devices “talking” above, below and even on the same operating frequency, utilities that deploy a mesh system architecture face challenges in the signal-to-noise ratio, which leads to inferior throughput and reliability.
Licensed spectrum systems have a naturally low noise floor, maintaining excellent signal-to-noise ratios even across longer distances and in the presence of signals on nearby bands. And, like an open highway, signal traffic can move swiftly and travel further than when plagued by congestion. Licensed spectrum allows data to be transferred to and from the meter quickly and reliably.
Range
Unlicensed mesh networks, being public, are prohibited from generating more than one watt of output; which makes the signal range limited. Even if they could transmit further, they would suffer poor signal-to-noise ratios across longer distances. For these reasons, mesh networks require many points close together and move signals across a larger area through a series of short-range transmissions to intermediate nodes.
Licensed spectrum systems enable utilities to use higher power levels to optimize performance. Because of this flexibility, licensed spectrum networks are virtually interference-free and untroubled by crowded channels, as opposed to mesh networks whose power allotment largely relegates architecture to line-of-sight coverage only. Licensed spectrum signals routinely reach many times the distance of mesh signals.
Bandwidth requirements
Unlicensed mesh networks use a lot of bandwidth for each transmission because the data “hops” from node to node and requires a new slice of spectrum for each step. As such, the cumulative sum of bandwidth for sending a signal from its source to a final endpoint can really add up.
Licensed spectrum systems can work with a narrower band; however private spectrum is not as abundant as public spectrum. It’s not free, either. It must be purchased or leased, sometimes in auctions where bidders must compete for licensed bandwidth.
Latency
Low latency, or reduced delay time, is increasingly important in the data-heavy smart grid era. Unlicensed mesh networks involve a processing step with each node they reach, and this slows the signal’s process to its destination. This lag or latency increases not only with distance but when there is traffic from voice communications or a high volume of other data.
Licensed spectrum systems allow signals to move through fewer or no mid-point nodes, so processing time is minimal, and the signal moves swiftly to its destination. For utilities, reducing delay time in communication to and from the meter allows technicians to identify outage information faster, which improves response time and provides the data needed to proactively address issues before a customer calls in to report an outage.
Top Criteria for Utility Communications Applications: What Matters and Why
Taking note of the features and architectural considerations that differentiate each approach, utilities must consider the below factors to determine which wireless network will perform best for their needs:
- Cost
- Privacy and security
- Reliability
- Redundancy
- Range
- Signal to Noise Ratio/interference
- Latency
- Interoperability
- Scalability
- Resistance to obsolescence
- Ruggedness in weather
- Geographic challenges
Which matters most? It depends on the utilities’ project requirements. The type of communication network was a big factor in the AMI solution deployed at Benton PUD.
Randolph Wheatley is vice president of Communications Solutions at Sensus. Wheatley has 30 years of experience within the technology space with leadership roles in product management, operations, and product development at Sensus. He obtained his MBA at the University of Texas at Dallas.
Public Utility Perspective on Wireless Communication Options
By Steve Hunter
Benton PUD is located in the heart of Washington State’s Tri-Cities—also known as “Washington Wine Country.” We serve more than 50,000 customers across Kennewick, Finley, Benton City, Prosser and outlying areas. While residents of this “year-round paradise” are known for a sense of fun and adventure, they’re serious when it comes to their demand for reliable and efficient service.
To proactively address our customers’ needs for higher quality service, we realized that we needed to think bigger about our electricity infrastructure, and that meant upgrading to advanced metering infrastructure (AMI) technology.
We wanted to deploy a network that would allow us to improve overall operations and communication with customers, so AMI made sense. While we knew AMI was the right path, there was a lot of research that went into identifying the right AMI provider and that included understanding the difference between a point-to-multipoint network architecture and mesh network architecture.
Laying the foundation
Our team understood that the communication network would be the foundation for a successful AMI deployment, so we prioritized the criteria list. Most importantly, we wanted a network that would allow for fast communication with our electric meters while also serving as the foundation for future applications.
We knew that an AMI deployment was an investment, so the team needed to identify what additional services were needed to meet customer expectations now and provide an opportunity for growth in the future.
A solution that checked all the boxes
After evaluating AMI solutions, we ultimately chose a point-to-multipoint network architecture based on the need to optimize network performance and quickly process data on a secure and reliable network.
The solution, provided by a North Carolina-based utility technology provider, met all of our criteria and would lay a foundation for future success. One of the biggest factors in the decision was the vendor’s two-way communication network that offered the right capabilities to meet both current and future needs.
Providing value for our customers
Now fully deployed, our AMI solution on the point-to-multipoint network has exceeded expectations. For starters, the solution has delivered the flexibility and security we desired while allowing our utility to add more enhancements for customers.
Our team knows we made the right choice because the value of the network has only increased over time. Since the initial deployment, we’ve been able to add a new customer portal so residents can monitor their usage and we have plans to launch a prepay program by the end of the year.
Because the meters communicate to our utility staff in near-real time when there is an outage, we’ve improved response time to outages and are able to pinpoint issues that previously would have never been detected.
All of this helps us work more proactively on behalf of our customers. When utility staff receives an outage notification, we can communicate with customers and swiftly initiate repairs.
It’s a win-win for our utility and customers.
Charting a path to the future
The AMI solution on the point-to-multipoint network is our foundation for the future. As the industry progresses and new smart grid applications hit the market, we will continue to evaluate new capabilities.
The factors that affect a utility’s choice of a wireless network are highly influenced by the individual organization’s resources, goals and challenges. In practice, a combination of mesh and private/point-to-multipoint approaches may exist across a utility’s different applications or even within them as projects scale and grow.
By weighing the factors, utilities can select a wireless communications network that will fit their current budget and future needs, deliver equal or improved reliability and support long-term customer satisfaction with rates and services.
Steve Hunter is director of operations and assistant general manager at Benton PUD, overseeing the safety and reliability of the utility’s electric system. He has more than 30 years working in the engineering and operations departments. Hunter is a Washington State-licensed professional engineer and obtained his bachelor’s degree in electrical engineering from Washington State University.
