Thursday, April 16, 2015

ZigBee or Not to Be, or, Why Fi?

One of the interesting things to come out of a number of my conversations at conferences is the single-minded focus on a given company's chosen approach to implementing Demand Response.  The most often mentioned approaches were either ZigBee or WiFi.

Each has it's advantages, and disadvantages.



For the ZigBee crowd, it seems that the large installed base of Smart Meters with embedded ZigBee radios would seem to be a slam-dunk victory.  Emphasis on the word "seem".

Of all of the Smart Meters in place with ZigBee radios, only a tiny fraction of them are actually turned on and used.  There are a few reasons for that:
  • Many of them are early versions of ZigBee, which had some issues regarding security.
  • AMI systems are somewhat limited in the encryption that they can implement, because a key element (the meter itself) doesn't really have a lot of spare capacity to implement advanced, and advancing, encryption.  
    • The more information you pass through an encrypted system, the easier it is for that encryption to be cracked.
    • If a Utility passes a lot of device control information over the AMI system's encryption, they weaken that encryption, and reduce its useful life.
    • Meters are supposed to be long-lived devices.
  • Utilities are also recognizing that having a lot of detailed information about the individual devices in the home exposes them to a greater risk of cyberattack, by making their systems a juicier target.
    • The secret to cybersecurity is not to be impenetrable, that isn't possible.  The secret is to be tough enough that it isn't worth the effort.
    • Its a little like the story of the two hikers who were confronted by a Grizzly.  One of the hikers dropped his pack, dumped his boots and quickly put on track shoes.  The other hiker said, "You idiot, you can't outrun a bear!" The fleet-footed hiker answered, "I don't need to outrun the bear, I only need to outrun you."
    • Having that very personal information about their customers not only creates a better target for hackers, bidirectional communication with individual devices greatly increases the "attack surface" (the pool of equipment through which an attack could come.)
    • Finally, all of that adds up to a major pain in the posterior in terms of a large body of personal information that must be protected, and a potential lawsuit risk if it is penetrated.
OK, so what about WiFi?  Any issues there?
As probably most of my readers are aware, WiFi isn't just WiFi.  There are a number of different standards in place, and more on the way.  The standards existing "in the wild" are:
  • 802.11a - 5Ghz band, shortest range, slowest speed
  • 802.11b - 2.4Ghz band, same range, but up to 11Mbit/sec.
  • 802.11g - 2.4Ghz band, slightly longer range, but up to 11Mbit/sec.
  • 802.11n  - 2.4 & 5Ghz bands, twice the range, up to 150Gbit/sec and multiple antennas (MIMO). 
Now, companies are generally going to build in WiFi that meets the need at the lowest cost.  Demand response and home automation generally doesn't need massive throughput, and they need to be compatible with the most common routers out there.  So, they're going to opt for 802.11a,b,or g.

Now the real attraction for 802.11n in the market is that it finally has the bandwidth to stream video, and do it in HD.  (Ok, not the upper end of HD, but at least better than SD.)  That bandwith is of course useful for other things (like me writing this blog entry) but most folks who spend the bucks for an 802.11n router are doing it so that they can stream video.

What happens when you connect an 802.11a,b, or g device to an 802.11n router?  It connects, and works just fine, thank you.  The 802.11n router falls back to a, b, or g, as needed.  But there's a catch (there's always a catch).

Unless you either;
  • spend the really big bucks for an 802.11n router that can do 802.11n on one channel (or band), and 802.11a, b, or g on another channel (or band), or
  • have two routers (one just for 802.11n and the other doing 802.11a,b,g)
everything on the wireless network falls back as well.

That means that the customer's fancy Wi-Fi home automation system may just break their fancy wireless video streaming.  This is not a positive customer experience.

Add in the fact that people change their WiFi routers out, and aren't careful about transferring set-ups from their old router and you start to have basic connectivity issues.

So what's the solution?

Well, we could just recognize that there is no Holy Grail of DR communications, and go with a modular approach.

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