Radio Frequency
Strategy in an
AMI Deployment
Larry Eggleston
Director, Product Marketing
Michael Schleich
Director, Research and Development
tabLE of ContEntS
Radio Frequency Strategy in an AMI Deployment ... 3
Question One: Narrowband or Wideband? ... 3
Wideband ... 3
Narrowband ... 3
Question Two: Licensed and Unlicensed? ... 3
Unlicensed ... 4
Licensed ... 4
AMI Vendor RF Strategies ... 4
Industry Adoption of Unlicensed Bands ... 4
Itron Position ... 4
radio frEquEnCy StratEgy in an aMi dEPLoyMEnt
Energy and water utilities are moving towards advanced metering infrastructure (AMI) projects to help manage the growing
challenges of supply/demand balancing, ensure delivery reliability, manage operational costs and improve customer service. Wireless networks are a foundational component of AMI
solutions, offering utilities real-time meter data, distribution system performance indicators and two-way communications for remote system control. Network radio frequency (RF) and bandwidth utilization are major factors for utilities as they strive to find the system that will offer unquestionable service reliability. Experienced AMI vendors understand the critical importance of network performance for their customers and subsequently develop RF strategies to ensure expected service levels are met, both near- and long-term.
Two key areas requiring analysis and assessment when considering an RF strategy are:
» Business Objectives
The RF strategy deployed is typically viewed as a technical decision. However, the business impact on this decision needs to be viewed as well. Of paramount importance, does the technical choice meet the requirements of the business case? Primarily, does available bandwidth support the short and long term strategy for data throughput? How much data can be delivered and at what rate today? Is there sufficient capacity available for growth? Will the RF strategy support low latency needs such as notification of alarm events and In-Home Display? As the territory grows, will there be capacity to meet the increasing data needs required as population and use cases evolve? Is the system one-way or two-way? What capabilities does the solution enable? Utilities should thoroughly examine not only their immediate business needs but also anticipate the factors that could be helping to shape their business in the years to come.
» Performance
In order to guarantee performance over the life of the solution, all RF solutions, whether licensed or unlicensed, need to address a plan for ensuring prescribed Quality of Service (QoS) levels. QoS performance is measured by capacity, data rate and latency and is essential for AMI networks with growing data needs. Capacity can be measured as the number of AMI transmission points in a given network. Data rate impacts the amount of data a network can efficiently transmit at a given time and latency defines the freshness of the data in the system and is critical regarding commands and on-demand read confirmations in two-way networks. These attributes have a direct relationship on system performance. Conversely whether a licensed or unlicensed system, radio interference can degrade performance, if not appropriately considered in the system design. When designing an AMI system, the system architect must consider balancing all of these attributes to ensure a robust solution.
This document will help the reader recognize the important questions to consider when choosing an RF strategy. By considering the business case and overall performance
expectations on bandwidth and licensed or unlicensed strategies, it will become evident that an unlicensed strategy is well suited for advanced metering and is the RF spectrum of choice for AMI system suppliers.
quEStion onE: narroWband or WidEband?
As outlined above, capacity, data rate and latency are leading performance indicators for AMI networks. The impact bandwidth has on these three performance classes is a key consideration in developing an RF strategy for an AMI solution. To understand the performance differences between a wideband system and a narrowband system requires a real-world comparison.
»Wideband
Itron offers wideband capability for its AMI solution, operating in the frequency band between 902MHz - 928MHz. Itron wideband systems operate across 120 channels and are designed to receive up to 120 separate transmissions simultaneously, each at 37.5 kbps (kbps = kilo bits per second) data rate. This capacity and data rate enables information from all endpoints to be delivered with low latency. Typically, for the full deployment, each meter’s message collected by the system will be less than 5 minutes old at any point in time. Proper RF network design helps ensure that capacity, data rate and latency aren’t adversely impacted by service increases.
»Narrowband
Known narrowband competitors operate at 450MHZ and 900MHz frequencies and have typical bandwidths of only 12.5 kHz, with some claiming extensions up to 50 KHz. Their narrowband systems utilize between one to four channels and therefore can only simultaneously receive one to four transmissions at any given moment, at typical data rates ranging from 1.2 kbps to 8 kbps. In the narrowband case, for the full deployment, each meter’s message collected by the system will be several hours old at any point in time.
The summary is that the Itron wideband system provides a raw instantaneous capacity of 4500 kbps (120 x 37.5 kbps) compared to a typical narrowband system with an instantaneous capacities ranging between 1.2 kbps and 32 kbps (4 x 8 kbps). While neither system would be designed at that limit, this comparison does show the relative magnitude of data handling potential between a wideband and a narrowband system.
quEStion tWo: LiCEnSEd and unLiCEnSEd?
While a preponderance of AMI solutions utilize unlicensed, yet regulated, RF spectrum, some AMI solutions have been developed for licensed frequencies. These latter solutions have their roots in a pre-AMI business model where a daily meter read sufficed and there was little call for advanced functionality such as two-way capabilities driving operational efficiency, system integrity telemetry or conservation-based in-home display (IHD) to enable consumer action.
At first glance, it might seem that licensed frequencies would be preferred. However, reliability is not guaranteed within a licensed band, nor should an unlicensed band be defined as unreliable. The fact that a majority of AMI vendors are utilizing unlicensed frequencies is strong support to its performance reliability. Are all of the AMI solutions today utilizing unlicensed bands today at risk? Certainly not. The implication that licensed spectrum is more robust and more protective has not been demonstrated by industry. This is especially true when considering system growth and AMI business drivers.
» Unlicensed
•Use of unlicensed frequencies—typically the industrial, science and medical (ISM) bands—does not mean that the band is uncontrolled. Every device operating on the band is still regulated by the Federal Communications Commission (FCC) and must pass stringent test requirements to ensure that it operates within the guidelines of the band—guidelines that are in place to protect equal access of the band
•The FCC objective in overseeing the operation of unlicensed bands is to assure a fair playing field. Today, there are hundreds of millions of devices that operate in ISM bands. Continued maintenance of the band is incented by the base of users already in place
•Unlicensed bands exist globally. Technology evolution and enhancements are commonly driven and subsidized across global opportunities. This ensures a cycle of continuous improvement, resulting in lower cost and higher performing equipment
•Because the users of unlicensed channels expect other users in band, and since these users are regulated, the operational signature of those users is also known. Thus, mature system architecture includes robust interference management techniques. To manage interference, users of unlicensed frequencies utilize multiple pro-active communications techniques to avoid interference, thus ensuring a high QoS level
» Licensed
•Licensed wideband spectrum is not publically available and if it were, it would be cost prohibitive. Therefore in the AMI industry, licensed solutions are synonymous with narrowband systems, inclusive of the performance limitations inherent in narrowband systems
•Licensed frequencies do not guarantee interference-free operations. Interference can come from legal adjacent channel users and from other licensed users. Different RF power levels are allowed in the licensed bands, with ranges from less than 1 Watt up to 300 Watts. A high power signal, such as a legal 300 Watt transmitter, in a legal channel can cause interference and adversely impact communications reliability for a lower power device in adjacent channels
•When interference does occur, licensed devices have no option. They are licensed for operation on a single or a small subset of channels, which eliminates their ability to move to open channels. This will contribute to diminished Quality of Service
•Utilizing licensed bands over large territories could require separate licenses to cover multiple areas, leading to additional logistics management. Because certain devices have to be deployed in certain areas, specific configurations would be required, creating warehousing and inventory issues •Since licensing of communications channels is publically
available, territory growth offers no guarantee that the same operating frequencies will be available
aMi VEndor rf StratEgiES
industry adoption of unlicensed bands
There is little debate on whether licensed or unlicensed operations best serves the needs of AMI customers as the vast majority of AMI vendors utilize unlicensed bands for their systems operations. This list includes Datamatic, Elster, GE, Itron, Landis+Gyr, MasterMeter, Silver Spring Networks and Trilliant. Even some AMI suppliers that utilize licensed frequencies are promoting equipment that use unlicensed spectrum as a part of their network.
itron Position
In determining to go with licensed or unlicensed frequencies, Itron decided to utilize the unlicensed frequency for our AMI solutions because it offers customers greater system flexibility, superior performance and a lower cost of ownership.
Itron has been developing RF-based meter data collection systems for over 20 years, and with over 60 million devices in the field that operate within the unlicensed frequency, our products have been the cornerstones of successful collection systems to utilities around the globe. Our experience working in the unlicensed band, along with our long term commitment to innovation has resulted in the development of advanced radio technologies that minimize interference, increase system reliability and enhance performance. In fact, the FCC looks to Itron as a leader in spectrum utilization. Compared to a narrowband approach utilizing one or two channels, Itron’s technology simultaneously operates on 120 multiple independent communications channels. This allows the system to ignore channels with interference noise while leaving the majority of channels available for system data transmission.
This diagram represents the 120 independent channels that Itron reads across simultaneously on in the unlicensed frequency. The large blue arrow is interference and the smaller arrows are transmissions. Radio signals will be blocked from the channels where interference is and those signals will jump automatically to any one of the many channels that remain open. This advanced radio functionality is possible by the coordinated design between Itron endpoints and radios, leveraging the adaptive channel plan engineered by Itron.
With an Itron RF solution, our customers gain:
» Agility — robust, military-derived, frequency-hopping transmissions to provide interference immunity
» Adaptability — optimal channels are automatically selected for each field collector
» Established Technology — our 5th generation software defined radio features powerful digital signal processing (DSP) capabilities and fifth generation software to provide superior performance, even in the harshest RF conditions
» Growth — system capacity and bandwidth designed with industry leading performance while having adequate margin to support future growth in both population and advanced functionality
» Conservative Propagation Predictions — leading propagation modeling and actual environmental testing are utilized to determine conservative deployment parameters
Even though the bulk of our technology utilizes unlicensed bands, Itron does offer a successful wireless network solution for the water industry that uses a licensed frequency. Our historical experience with both licensed and unlicensed solutions has reinforced our decision to use the unlicensed frequency for our data-rich AMI solutions.
SuMMary
When selecting an AMI provider, one of the decision points is to choose a vendor and their RF spectrum choice based upon meeting ones’ business objectives. Are flexibility, performance and cost objectives met? Licensed and unlicensed frequencies options are available. When it comes to providing true AMI capabilities, the industry has clearly moved to the unlicensed spectrum for the reasons stated here. When choosing a specific AMI solution, it is imperative to understand how the technical choice meets the business case requirements, and to consider an RF strategy where proactive measures ensure long-term robust operations.
Unlicensed frequencies offer critical system performance that the majority of AMI vendors have embraced with full confidence, to ensure the near- and long-term levels of service that are expected by their customers.
While Itron strives to make the content of its marketing materials as timely and accurate as possible, Itron makes no claims, promises, or guarantees about the accuracy, completeness, or adequacy of, and expressly disclaims liability for errors and omissions in, such materials. No warranty of any kind, implied, expressed, or statutory, including but not limited to the warranties of non-infringement of third party rights, title, merchantability, and fitness for a particular purpose, is given with respect to the content of these marketing materials. © Copyright 2012, Itron. All rights reserved. 100965WP-03 05/12
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