The smart grid is no longer a pipe dream. The introduction of next-generation networks – coupled with the recent influx of capable and efficient smart grid applications – has given utilities plenty of reason to extend connectivity to the electric distribution grid.
This evolution has begun to shine light on the Field Area Network (FAN), a private, multiple purpose network capable of providing last-mile connectivity with low latency and high availability. These architectures can enable a new suite of smart grid applications that provide greater control and flexibility over key assets while simultaneously lowering operating costs.
Architecting a multi-purpose FAN network requires careful consideration. Utilities need to analyze their existing WAN footprint and infrastructure assets and make careful decisions on the four major buildings of a Field Area Network:
- Physical medium (wireless or wireline)
- Network topology
- Network technology
- Product platform
Physical medium choices
The most basic decision that utilities need to make is whether to build their FAN capabilities on the back of a wireless or a wireline network.
Power line carrier (PLC) technologies, the most widely used infrastructure to support wireline networks, have evolved in recent years to the point that they can host full Advanced Metering Infrastructure (AMI) applications, particularly overseas where the transformer-to-meter ratio is higher.
However, PLC networks have a number of drawbacks: they are not reliable across transformers, they tend to limit throughput and they use the power lines that are subject to physical outages.
Fiber-optic networks are another wireline possibility – providing near unlimited capacity and the best possible latency – but the cost associated with these network often outweighs the smart grid gains.
Wireless networks, on the other hand, provide a number of cost-effective and efficient options. Utilities can rely on traditional narrowband radios used in utilities, which can operate in the licensed or unlicensed spectrum, as well as broadband wireless technologies like Worldwide Interoperability for Microwave Access (WiMAX (News - Alert)) and Long Term Evolution (LTE).
Of these options, the most ideal solutions for utilities are broadband-related options, which are much more robust than narrowband radio technologies that are inadequate for supporting a multi-purpose network.
"Unlike narrowband radio solutions, these broadband solutions are standards-based platforms," telecom equipment vendor Alcatel-Lucent (News - Alert)-Lucent notes in a recent white paper, Architecting Wireless Field Area Networks. The authors further state, "As such, they provide a greater choice of vendors to utilities and ensure long-term support for the network."
Wireless network topology choices
Wireless technologies provide a number of different topology options for FANs. One of the more common approaches is a point to multi-point (PMP) topology, where one radio, typically called a base station (BS) or access point (AP) radio, would simultaneously handle multiple links to endpoint radios called Customer Premises Equipment (CPE) or Subscriber Modules (SMs), according to Alcatel-Lucent.
This topology is a very popular choice for FANs operated by utilities in North America and Australia. However, unless redundancy is built-in, network owners will need to build redundant base stations to avoid the ramifications of failures.
Another option is RF mesh topology, widely used for AMI networks in the last mile. These topologies are gradually gaining a higher level of acceptance by utilities who are responding well to the technology's built-in resiliency. However, the advanced feature sets and capabilities of RF mesh come at a cost. The mesh nodes tend to be more expensive than the CPE typically used in PMP networks.
In addition, mesh technology is often only available with unlicensed spectrum, a concern that often leads to interference. Utilities can overcome this problem by deploying directional antennas or sectorizing the site in the manner used for PMP networks, says Alcatel-Lucent.
Yet another approach is hybrid mesh technology, "where omnidirectional antennas are sectorized to obtain directionality and provide more tolerance to interference," says Alcatel-Lucent.
"This sectorization is achieved with one radio, which switches between different antennas in sequence and at a very high rate — thousands of connections per second. This reduces the cost of radio and lowers real estate requirements, and it also optimizes the number of sites required to support the network and minimizes the probability of interference."
Wireless technology choices
Wireless technology choices cannot be made in a vacuum; selections must be made based on the aforementioned spectrum and topology requirements. WiMAX and LTE (News - Alert) networks can only be implemented as PMP networks while Wi-Fi can be deployed in PMP or mesh topologies. Licensed spectrum offers more options than unlicensed spectrum, including LTE, WiMAX, and older technologies like Data Over Cable Service Interface Specification (DOCSIS).
Alcatel-Lucent recommends LTE as the best technology for PMP networks, but acknowledges that spectrum supported by LTE is scarce and highly sought after by service providers. This may all change in coming months though, as Congress recently authorized the First Responder Network Authority (FRNA or “FirstNet”) to build a financially self-sustaining network through, among other things, partnerships to share infrastructure with third parties, including utilities.
"This is a unique opportunity for utilities to obtain a very attractive spectrum for deploying FANs, without incurring the very high cost of obtaining spectrum through a spectrum auction," says Alcatel-Lucent.
WiMAX is also another strong option.
The product platform
When all the analysis is completed and the technology choices are made, utilities must then study diligently to choose the right product platform. Utilities should look at optional features like redundancy and supported packets sizes, and only target solutions that are compliant with utility standards. In addition, utilities should ask questions about future product developments to help them outline future FAN utilization.
"Beyond making the right choices for each building block, it is important to engineer the network properly to ensure that all network objectives are met," says Alcatel-Lucent. "In addition, proper integration of the FAN with adjacent layers such as the Wide Area Network and Neighborhood Area Networks (NANs) is critical to ensure that end-to-end performance objectives are achieved."
Alcatel-Lucent has been actively engaged with electric utilities from around the globe developing communications network solutions focused on optimizing the all of the benefits smart grids will deliver. FANs are just one critical component in a broad portfolio of solutions aimed at addressing the diverse challenges utilities face in deploying smart grids based on their unique requirements.
Edited by Peter Bernstein