Paul Senior, Airspan Networks
In recent years, “smart grid network” has become an overused phrase that has saturated the energy industry. Information has been pouring out about technologies, creating confusion about what the real options are and what each delivers.
Issues and questions related to wide-area wireless communication networks and how technologies compare abound.
Despite numerous smart grid definitions, the goal is to benefit utilities, consumers and the environment by creating a more efficient energy generation and supply ecosystem. The entirety of the smart grid incorporates several companies, products, components and technologies. But the essential link is the communications infrastructure. In addition to the myriad technology and operational determinations that must be made in designing a network that addresses these requirements, the selection of the spectrum that will provide the network’s wireless backbone is critical. This decision impacts the structure, capacity and scalability of the planned network and will have long-term consequences for the effectiveness, as well as capital and operating costs, of the network.
Network Requirements Planning
Some utilities have been committing to narrowband wireless solutions in support of near-term objectives, such as AMI programs, with apparent minimal regard for the future complexity that such a decision may impose on network planning. In some cases, these commitments are responses to the requirements of stimulus-funded smart metering programs. This approach, whether using public or private spectrum, likely will not provide adequate bandwidth to enable the high-return on investment (ROI) middle-mile applications such as distribution automation (DA), telepresence, mobile work force and monitoring. In addition, these narrowband approaches typically cannot be scaled or backward integrated to address these opportunities. Consequently, utilities will need to replace or substantially reconfigure their networks within a short time following their advanced metering infrastructure (AMI) decisions.
The diagram on Page 18 shows distribution applications utilities are pursuing and demonstrates the rapid rate at which bandwidth capacity is consumed.
Private licensed spectrum of adequate bandwidth is the best approach to achieve the broadband capacity necessary to support the full range of applications required for a complete smart grid network, thereby future-proofing utilities’ wireless networks for future technology generations. This solution enables a private network that avoids a public or shared interface and assures utilities top network priority for critical infrastructure communications.
Several considerations exist in making the spectrum decision underlying the smart grid wireless communications infrastructure plan:
- 1. Coverage,
- 2. Licensed vs. unlicensed,
- 3. Narrowband vs. broadband,
- 4. Private vs. public network, and
- 5. Cost.
Coverage. Spectrum rules and ownership patterns create complexities in configuring a service-areawide wireless spectrum solution. Utilities often must create hybrid networks to achieve adequate coverage of targeted end points. This mix of spectral solutions complicates network planning and might result in coverage dead spaces that must be addressed with costly alternative links. Uniform spectral coverage becomes increasingly valuable as last-mile and middle-mile networks converge.
Licensed vs. unlicensed. The utility industry is becoming increasingly aware of the importance of exclusive spectrum access to assure access and priority for critical infrastructure connectivity. Unlicensed spectrum already has played a role for utilities. For example, 900 MHz solutions have been used for millions of meters nationwide. It works for battery-powered meters and allows an aggregated, timely reading of many meters. This form of communications, however, is a one-way, meter-reading capability. It does not allow the two-way communication that allows consumer interaction and real-time data applications for home-area networks (HANs).
To achieve this, a utility needs a secure, two-way broadband network. A utility can use unlicensed spectrum to achieve this, but unlicensed or semi-licensed spectrum such as 2.4, 3.65 or 5.8 GHz are susceptible to interference while leaving little control over who or what uses the shared spectrum, creating a cybersecurity vulnerability.
To build a mission-critical solution, a utility must use a licensed spectrum solution that allows it to build a private, secure network that can be controlled, protected and operated better. This private network can complement existing 900 MHz or 3.65 GHz applications while empowering the utility and allowing a broadband, robust, two-way network needed for key applications.
Accessing licensed spectrum is the biggest challenge. It is limited in availability. The Utilities Telecommunications Council (UTC) has been advocating that the Federal Communications Commission make spectrum available to utilities. The potential outcome of this initiative is unclear. Some companies offer utilities long-term spectrum leases. Airspan Networks, for example, offers long-term lease arrangements directly with the leaseholder in the 1.4 GHz spectrum. This spectrum is available nationwide to utilities for exclusive coverage of their service areas.
Narrowband vs. broadband. During the past couple of decades, low-speed supervisory control and data acquisition (SCADA) applications were all utilities required. Today, however, utilities need broadband connectivity to enable the bandwidth-demanding (i.e. Mbit/s not kbit/s) applications associated with smart grid networks.
Fiber can support many of the most demanding applications. But the economics of fiber fizzle as the grid moves into the distribution process and spreads beyond the reach of existing fiber networks. This is where wireless broadband takes over.
The Department of Energy (DOE) analyzed this smart grid phenomenon and created a matrix that depicts this point. To run a number of smart grid applications on the same network, a broadband pipe is required.
The requirement of broadband connectivity grows exponentially and is the only network that allows applications such as mobile work force, video and closed-circuit television applications. Utilities that make network commitments without considering the inevitable increase in traffic and applications risk creating overly costly, complex communications networks that likely will require substantial rework.
Private vs. public network. Private networks are wholly owned and operated by a utility (or selected partner). In these scenarios, the utility selects the technology and infrastructure and is responsible for the deployment and operation of that network. Private networks are more expensive initially, but long-term costs can be significantly lower than public networks.
Public networks are publicly available carrier networks, usually cellular networks, shared by the consumer market. Utilities must share the network with neighboring businesses and residents, and they have no control over usage.
An ongoing debate exists on whether private or public networks better meet the demand of smart grid communications. Public networks offer mobile and voice connectivity that might be better met on their networks, but private networks offer several performance advantages that a public network cannot provide to the same degree. These advantages include network reliability, security and latency (refer to the DOE matrix for minimum requirements for most of these parameters, Page 20).
- Reliability: A utility must depend on a network operating at a minimum of 99 percent reliability (uptime). WiMAX and 4G equipment properties such as system redundancy and prioritization allow for a more reliable, dependable network. Public networks are highly susceptible to degradation and interference and cannot guarantee such a high quality of service. This can become more problematic during emergencies and natural disasters when utilities most rely on their network reliability and are under pressure to deliver.
increasingly is becoming a point of contention for utilities. More stringent security standards are being released, holding utilities accountable for their system integrity and exposing them to possible hefty fines for not adhering to those standards. No public system can offer the level of security guaranteed by a private network. Only a private network completely can control all data traffic and users allowed access. This helps create an added level of security against security breaches.
- Latency: For many smart grid applications to function properly, a minimal level of latency is required. Latency is the time it takes to communicate a piece of information across the network. Many applications cannot function accurately if it takes too long for the information to pass through. This means that the latency must be extremely low, often lower than a few milliseconds, to meet requirements. Private networks using 4G WiMAX equipment have extremely low latency rates. This enables utilities to deploy networks confidently to support applications including AMI, demand response and mission-critical functions. Public networks often function at latency rates of up to 100 times those of private networks.
Cost. Spectrum cost must be evaluated on a total cost-of-ownership basis when comparisons are made among private licensed, unlicensed and public carrier alternatives. Although private networks require up-front infrastructure build outs, many utilities demand the control over their critical infrastructure that private networks enable. Although public carrier deployments might require a smaller infrastructure investment from the outset, the cost of ongoing, mandated infrastructure upgrades and the lack of total network control by the utility are factors to consider. Many industry participants acknowledge the rapidly expanding role of communications in utility operations and insist the level of network control that only private networks can provide.
In addition, private licensed spectrum acquisitions can be paid annually or as ownership rights or capitalized leases that may be included in a utility’s rate base for ROI purposes. Public carrier spectrum models offer much less flexibility. In addition, the terms of acquisition of private licensed spectrum can be negotiated up front so the economics of this element of the cost structure are predictable. By contrast, public carrier contracts typically leave utilities at the mercy of future telecom provider pricing policies.
Some utilities are committing to short-term, narrowband wireless solutions in support of near-term objectives, such as AMI programs, with apparent minimal regard for the future complexity that such a decision might impose on network planning. These short-term approaches typically cannot be scaled or backward integrated to address these opportunities. Consequently, some utilities will need to replace or substantially reconfigure their networks within a short time following their AMI decisions.
Private licensed spectrum of adequate bandwidth, combined with professional wireless network design, is generally the best approach to achieve the broadband capacity necessary to support applications required for a complete smart grid network. This approach enables a private network that avoids a public, shared interface and assures a utility top network priority and security for critical infrastructure communications.
Paul Senior is chief technical officer with Airspan Networks.
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