We are all familiar with devices like smartphones and Internet of Things (IoT) that use Long-Term Evolution (LTE) to enable their connectivity to commercial cellular networks around the world and provide plug-and-play connectivity for a multitude of end-user devices. LTE is a global standard for wireless broadband communications first proposed in 2004 and has been under continuous refinement ever since. That same standard is now available for utilities to use to build their own private networks.
Utilities have had private, wireless networks for several decades. However, those networks were typically proprietary and purposely built for each application. This resulted in utilities installing, supporting, and maintaining multiple networks for every application that required communications.
Utilities now have access to a standard technology that supports multiple applications across one technology platform, offering an increase in capacity and speed from previous technologies and providing the path for commercial carriers across the globe. Its massive user base means it will be sustainable, giving utilities much needed and long overdue technology stability.
LTE brings mainstream technology to the utility sector. It is a standard technology that is used in commercial markets and allows for forward and backward compatibility, has hundreds of manufacturers making thousands of different types of devices, can be used in many different spectrum bands, and is used globally.
It allows for prioritization, which is important for mission-critical communications such as Supervisory Control and Data Acquisition (SCADA) applications. LTE also allows for communication to tens of thousands of devices, which is becoming increasingly important in the utility sector as utilities deploy grid modernization devices.
LTE, however, requires a significant amount of spectrum. Utilities have limited access to spectrum and not typically in the quantities needed for LTE deployments. Additionally, LTE has a core which may require managing and operating by a dedicated staff.
LTE is relatively low power, meaning the small coverage area from a tower to its connected end point devices requires many tower sites. These sites can be expensive to build over a wide geographic area, especially in rural areas where the density of end devices is low.
Commercial carriers use LTE in their networks, and – despite it being built out in most of the country – there are still large areas without sufficient or even any service. This is particularly true in rural areas: Commercial carriers build their networks to serve people, and utility equipment is not always located in areas where those people reside.
Commercial carriers’ LTE networks are not designed to the levels of reliability and resiliency required by utility mission critical applications. Most commercial networks cannot withstand long-term power outages. They may have battery backup at their tower sites for short-term outages, but they lack generator backups to provide service during long-term power outages resulting from disasters such as hurricanes or ice storms. Additionally, commercial networks typically do not employ prioritization even though LTE provides for it within the standard. This means that utilities’ communications have no greater priority than a text message or a YouTube video.
This does not mean commercial networks can’t be used for utility communications; it simply depends on the application. While mission-critical applications such as SCADA are not well suited for public networks, higher bandwidth applications such as video surveillance or event files that aren’t time sensitive are good applications for commercial networks.
Private LTE has become the focus of utility networks over the past few years. Private LTE allows utilities to continue to maintain control of their network, allowing them to control availability, reliability, security, and in some cases latency, which meets the needs for mission critical communications. It also allows utilities to capitalize on a standard that is used by billions of devices, resulting in lower end device costs. LTE allows for prioritization, so SCADA can have a higher priority than applications such as capacitor bank controllers or other low priority applications.
Another benefit is that the network is under the control of the utility. The utility is responsible for upgrades and maintenance on their terms and can send out technicians 24 hours per day, seven days per week, 365 days per year.
At the same time, it has been very challenging for utilities to acquire spectrum to build PLTE networks. Most of the spectrum that utilities have access to do not have the bandwidth required by PLTE, which requires a minimum channel size of 1.4 MHz. However, there have been a few spectrum options recently made available that utilities may be able to purchase or lease.
The 900 MHz spectrum owned by Anterix is a likely candidate. The 3.5 GHz band (CBRS), recently auctioned off for private use, is a good candidate, but the use of the shared portion of the spectrum needs to be closely examined, particularly for mission critical applications. The 406-420 MHz band may have the possibility of being shared with the federal government. Across these bands, the higher the frequency, the shorter the signal range, which is a major cost driver as more towers are needed to provide adequate signal coverage. Spectrum needs to be carefully considered when exploring PLTE as options are limited.
FirstNet is a public safety, LTE network built to provide the ability for First Responders to interoperate nationwide between agencies. It is a result of the 9/11 Commission recommendations and comes after many years of lobbying following this recommendation. In February 2012, as part of Middle Class Tax Relief and Job Creation Act, 20 MHz of spectrum was allocated and the network was established. The spectrum allocated to FirstNet is in the 700 MHz band, which provides excellent propagation characteristics.
In March 2017 AT&T was awarded the FirstNet contract, and in 2018 AT&T began putting first responders on the network. Due to the criticality of some utility applications and their impact on life and property, FirstNet is offering utilities access on the network for some critical utility applications and some utilities are beginning to use it as a solution for some of their applications. FirstNet actively uses LTE prioritization, making it a more appealing alternative than a public, commercial network.
Utilities can benefit from all three types of LTE networks. Private networks are needed when utilities need mission critical communication that requires high availability, high reliability, low latency, and high security. A private LTE network requires a lease or purchase of spectrum and will have a higher capital expenditure.
Commercial networks can be used when utility applications do not have these stringent requirements and can also be used to provide backup services on more critical applications. For some devices, it can provide a network to roam onto where it is not cost effective to build out a PLTE site.
FirstNet has the ability to bridge the public/private divide and is a more robust network than a commercial network. It is not, however, a private network under the utility’s control, and applications have to be approved by FirstNet.
A hybrid network could also be considered. Applications such as SCADA and mission-critical voice have different requirements than AMI, surveillance video, and text and monitoring applications.
LTE provides significant benefits for utilities, including the ability to use technology and devices used in the commercial market, providing a supported network and end devices that are more cost-effective for deploying the millions of devices needed for grid modernization. Utilities will need to consider their applications to determine the type of network or a combination of networks that will satisfy them; if they are heading toward a private LTE solution, gaining access to spectrum should be top of mind.
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