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Why Heterogeneous PLC/Wireless Networks?

And why the requirements of mobile and smart energy aren’t so far apart as you may think.

Smart metering gets “really interesting” for CEO of fabless semiconductor firm Semitech Semiconductor, Zeev Collin, when it’s not just the meter that is being read, but also “other characteristics of power consumption behavior on a near real-time basis, in a recurring way.” Collin spoke with EECatalog not long after Semitech announced it is working with Brite Semiconductor to develop an Industrial M2M SoC, one that will use Semitech’s dual mode communication core for Power Line Communications (PLC)/wireless IP.

Collin sees a solution that brings the PLC pipe and wireless pipe together as one which allows OEMs to “standardize around a single solution.”

EECatalog: What is the argument in favor of heterogeneous networks?

Zeev_CollinZeev Collin, Semitech: Historically, some applications have gravitated to wireless, while others have gravitated to power line. Sometimes this has taken place because of good reasons—an application is better suited for one versus the other, or the geography is better suited for one versus the other, and sometimes it is purely political or it just happened to be that way, but as the industrial, smart energy and other markets mature, they are heading toward heterogeneous networks, where you have a mix of wireless and PLC. On a case-by-case basis you choose what’s needed to get data from one place to another—from one machine to another via mesh or directly to a gateway and then into the cloud in the most reliable way. The medium doesn’t matter, as long as there is no expectation of installing special infrastructure or any new wires like Ethernet or Fibre Channel. You want the data coming through without worrying about the medium.

EECatalog: The first products Semitech brought to market address the Industrial IoT space. As the company has entered other markets, including smart energy, have there been any surprises?

Zeev Collin, Semitech: The importance of power efficiency to applications that are not battery-powered, but connected to the grid surprised me when we got into this market. Unlike with mobile devices, where everybody understands why power is so critical, it is not entirely obvious why power efficiency would be critical if you are connected to the source of power—the grid—but it is. For many use cases, the whole idea is ultimately to save energy. If over time you consume the energy you are saving by installing communication, monitoring and control equipment, it kind of defeats the purpose.

EECatalog: What trends are you watching in the smart metering segment of the overall Industrial space?

Zeev Collin, Semitech: We are paying attention, for example, to how smart metering companies such as Itron are expanding their value proposition by becoming network and service providers. Itron has issued a number of releases recently about how it is creating a smart grid ecosystem, with the final link being utilities’ ability to use data to react in close to real-time to perform load balancing, for instance.

EECatalog: Semitech set itself apart somewhat by having its initial solutions center on narrowband power line communication (N-PLC) as opposed to wireless, but with wireless being there first, have you had the opportunity to apply lessons learned from wireless to N-PLC?

Zeev Collin, Semitech: Wireless has come a long way in the past 10 to 15 years. It is amazing to think about it: 15 to 18 years ago WiFi didn’t exist, and now it’s a ubiquitous technology. And yes, a lot of research and development went into wireless technologies, and now the lessons learned there are being applied everywhere else, including Power Line Communications. This has helped to jumpstart other segments, but it is not quite the same [for such aspects as] looking at the noise profile. Even though a lot of the same techniques apply, not all of them are suited for Power Line. At Semitech we emphasize more explicitly what would work better for Power Line. And we take common practices and then augment them with techniques that are more specifically designed for Power Line.

EECatalog: What’s a good way to visualize how wireless and Power Line differ?

Zeev Collin, Semitech: A good way to visualize wireless communications is as a sea, with the noise analogous to waves, and the ups and downs of those waves occurring somewhat predictably. The prevalent technique today in wireless, [Orthogonal Frequency Division Multiplexing] OFDM, is good at dealing with these noise characteristics because OFDM will try to optimize the signal by placing more data in the areas where the “wave” isn’t or is small.

The Power Line medium is quite different from the wireless medium in that regard. It is more like a battlefield, where everything is quiet, and then all of a sudden there is incoming mortar. You could have a big explosion in one area or a big explosion over the whole channel, and then you have a big section of the channel that is completely obstructed. OFDM can struggle with that kind of noise, because, while it is good with adapting the data to the quiet area, it needs enough “quiet area,” if you will, to get, at the very least, enough information, such as the packet header through. Otherwise, you don’t have communication at all.

One technique that we developed to combat that kind of noise profile is running a number of essentially independent modems that can operate in different areas of the spectrum, and which can be redundant to one another, so that when you have an “explosion” taking one of them down, it doesn’t affect the other. And as long as you have at least one of them that comes through, you are still going to get your data. Also, if you know there is persistent noise in certain areas, you can completely avoid those areas—you can work around it rather than sending information there.

EECatalog: Closing thoughts before we wrap up?

Zeev Collin, Semitech: The essence of our solution is that we’ve built an architecture that is very programmable and capable of advanced communication techniques that demonstrably work better, but without compromising cost and power. Now we’re expanding it to a dual mode architecture by adding narrowband wireless. The result is a true universal Industrial IoT solution that can simultaneously communicate wirelessly and over power lines, thus enabling true no-new-wires heterogeneous networks and “one solution fits all.” We’re providing the pipes. Utilities aren’t interested in the pipes, they just want to know that the pipes work.

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