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The public vs. private networks debate has been raging for some time now. Recently, Earth2Tech published two opposing articles, one by its Editor Katie Fehrenbacher, and the other by Stephen Johnston CEO of Smartsynch, exploring various reasons why utilities would prefer either privately-owned (working with a third party to build their own) or public carrier (often times cellular) networks for their smart grid communications needs. But is it truly one or the other, or is there an optimal mix with a combination of both?
Here’s my perspective: While most utility network communication needs will be fulfilled by private networks, there is still an important role for public cellular networks to play in augmenting private networks. Focusing specifically on wireless communications, I’ll begin by examining 6 key requirements laid out by the Utilities Telecoms Council (UTC) in their recent response to a Department Of Energy request for information. These requirements are: Availability, survivability, coverage, latency, security and life cycle.
Availability is a measure of how reliably a system performs over an extended period of time. Mission-critical communications — that are required for the power grid — need network availability of 99.999 percent or higher. That equates to just over 5 minutes of downtime per year. Private wireless networks can be engineered to meet these levels of availability, often through a combination of wireless technologies and high-availability architectural options such as mesh networks, like the ones created by my company Tropos, with multiple redundant communication pathways.
Public carrier networks can have high degrees of network availability, but the services they provide are shared with the consumer market and network performance can degrade dramatically in situations of network congestion, such as during emergencies and natural disasters, when utilities most need reliable communications. As of now the only way for utilities to ensure that their traffic is properly prioritized is to install and operate their own private communications networks.
Survivability is related to the resilience of the system — its ability to continue to deliver essential services even in the presence of attacks, failures, or accidents. Communications systems need to be environmentally hardened to withstand a wide variety of adverse weather conditions as well as to be provided with hours to days of backup power so as to remain operational during power outages following weather events. Utility private networks can achieve a high degree of survivability through the use of multiple technologies, multiple spectrum bands, and resilient mesh network architectures employing sophisticated algorithms for channel selection, power control and interference mitigation.
Public carrier networks have a mixed record with regard to survivability. For example, Southern Company noted in their filing with the FCC that they had to rely on their private communications networks to aid in power restoration after an extended weather-related outage, as the public network was out of service during that time – lack of adequate backup power on commercial networks results in the public network remaining unavailable until utility electric service has first been restored.
Coverage refers to the extent to which the communications network provides service within a given target area. The desired goal is usually to get close to 100 percent coverage. Given the wide diversity of utility environments and the mix of urban, suburban and rural territories in the service area, achieving close to 100 percent may sometimes be impossible for private or public communications technologies.
Utility private networks often use a combination of wireless technologies to achieve their coverage goals. Achieving these coverage goals presents a challenge for commercial public carriers since their business model and systems are optimized around providing coverage to the largest number of consumers possible, versus being designed to ubiquitously cover an entire utility service territory. Unserved or underserved areas are often not economical for a public carrier. However, there is still a role for public networks in areas where private networks are not feasible or cost-effective to deploy.
Latency is basically how long it takes for the data to run over the network. Some mission critical applications, such as distribution automation and wide-area monitoring and control, need to have a very low-latency to operate effectively (for example, line protection and control systems need a latency of under 20 milliseconds), whereas others that relate to smart meters are less demanding. Compared to private wireless technologies which can reach latencies of the 10-100 millisecond range, public cellular technologies widely deployed today offer latencies in 100-1000 millisecond range.
Security encompasses the protection of sensitive data and the control of access to critical systems. These information security capabilities and protections exist in both well-designed public and private wireless networks, but an additional aspect of security in the context of utility operations is the need to ensure system integrity and availability even under adverse conditions such as external attacks or disruptions and peak loads.
Since communications technology tends to evolve on a faster timescale (2-4 years) than utility capital investment cycles (15-20 years or more), equipment vendors and service providers need to be able to make long-term commitments to supporting deployed networks. In a way, this could be seen as a point in the favor of public networks. For many utilities, however, a commonly-expressed concern is that they are “forced” by the faster phone company technology upgrade cycles into upgrading large numbers of deployed endpoints (meters and field devices) or deal with the consequences of “stranded assets” — technology that no longer is compatible.
There are tradeoffs, usually involving cost, when it comes to achieving the desired reliability and performance objectives of a network. One of the benefits of a privately-owned network is the ability to design and implement a network that meets the reliability and security needs of mission critical smart grid applications, while making any necessary cost or technology tradeoffs along the way. By contrast, public carrier networks are designed to the cellular operator’s business objectives, which may not be aligned with those of the utility. With a private network, the utility has control over what technologies to deploy in which areas to achieve the desired levels of coverage, reliability and performance for its specific applications.
Most utility networks communications needs will be fulfilled by private networks, but there is still an important role for public cellular networks to play in augmenting private networks. Similarly, the UTC determined that utilities will use commercial carriers to support some of their applications, but that the majority of them will rely on private networks.
Additionally, Pike Research notes in their report that “Generally, grid applications with strict performance requirements, high reliability requirements, or high cost sensitivity tend toward utility-owned (private) and operated infrastructure. Other applications, such as AMI backhaul applications, will often use public infrastructure.”
Given the wide diversity of utility service territories, the regulatory requirements and their specific communications needs, it is probably safe to say that both public and private networks have important roles to play in enabling smart grid communications.
Narasimha Chari was responsible for developing Tropos Networks’ core intellectual property, including the design and development of the company’s wireless networking and routing protocols. Currently, he focuses on system and product architecture, product planning and participates in the company’s advanced development efforts. Among other honors, Mr. Chari was recognized by MIT Technology Review magazine in 2005 as one of the Top 35 Innovators under the age of 35. Prior to founding Tropos, Mr. Chari was a research scientist at Harvard University where he was recognized as a top lecturer and received the White Prize for excellence in teaching. He has performed research, published papers and disclosed patents in a variety of areas of mathematics, physics and wireless networking.
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