Imagine sprinkling tiny sensors on road and fields for surveillance, putting them in buildings and bridges to monitor structural health, and installing them in industrial facilities to manage energy, inventory and manufacturing processes.That’s the idea behind the emerging technology of wireless sensor networks (see “Casting the Wireless Sensor Net”).
Boston-based Ember is at the epicenter of this field. The MIT spinoff sells radio chips with embedded processors that can organize themselves into networks to manage real-world data from sensors. Ember CTO Robert Poor-whose past life includes stints as a programmer in the computer graphics group that became Pixar and as a guitar technician for the Grateful Dead’s Jerry Garcia-spoke with Technology Review staff writer Gregory T. Huang about his visions of a world filled with wirelessly networked devices.
TR: How did you first get involved with self-organizing, wireless sensor networks?
Poor: When Andy Wheeler and I were students at MIT, there was a DARPA [U.S. Defense Advanced Research Projects Agency] program called SensIT, which was looking at sensor networks. One application was battlefield-awareness systems, which really needed an easily deployed, reliable mesh network architecture. It was funding from that that allowed Andy and me to go from software simulations to hardware prototypes. We built hardware systems while we were still at MIT.
TR: How did Ember get off the ground?
Poor: Ember was started just over two years ago. At first, if we talked about wireless device networks, people would look at us strangely and say, what’s that all about? So we spent the first part of our time proving the technology to people and getting our very first platforms out there. Since that time, some things have changed-people no longer look at us strangely when we say wireless device networks. By the way, I do have a small issue with the term “sensor networks”-the term suggests just one-way communication, from sensor to collection point. Ember’s networks provide two- way communications. This is important for calibrating sensors, monitoring network conditions, and controlling devices. Our customers have needs that go beyond just sensors, and they actually have to control stuff.
TR: Ember’s customers are primarily in supply chain management, automated meter reading, and industrial and building automation. What are the most exciting applications?
Poor: Well, money is exciting, even if the applications may be mundane! One of our customers is Tyco Thermal Control. They make heating tape that you wrap around pipes. Not a big deal except when you’re in a petroleum field in northern countries where it gets cold, and you have to keep the stuff in the pipes warm so it doesn’t get too thick. Their problem is that they have to have temperature sensors that are wired to a controller, which communicates back to the pipe heating tape. In an oil separation plant, it would cost them between $3 and $10 a foot to run the wire, and there’s on the average of 1,000 feet per temperature sensor/tape combo. So that’s $3,000 to $10,000 per temperature sensor-for just the wiring. And in their case, they don’t own that part of the process. That’s actually done by a field installer, so it’s subject to errors. For example, if an installer installed a temperature sensor near a steam outlet, it would read that it was too warm, and so it wouldn’t heat up the pipe. The stuff in the pipe would get too thick, and a tank might burst. The plant could be down for six days at a cost of $100,000 an hour, just because the technician installed a temperature sensor in the wrong place. So what Tyco’s finding with our technology is that they can put down redundant temperature sensors, use two out of three votes to get a reliable temperature reading, and the installed cost is still less than the wired equivalent.
TR: Do you see these systems pervading our everyday lives?
Poor: Yes-much in the same way bar codes pervade our everyday lives. I bet 30 percent of the things on your desk have bar codes in them right now, but you don’t think about them. They’re just there. In your office right now, you look around, you see lights and switches. Those would be wirelessly networked. You see smoke detectors and heat detectors. Those would be networked. You see air conditioning systems and thermostats. Those would be networked. These are all existing infrastructure. And the interesting thing that will happen is that things that are not currently part of any kind of network will also be networked.
TR: Like what, for example?
Poor: There are microcontroller chips everywhere. During 2001, DARPA figures that there were 150 million CPU class chips sold. But during the same period of time, 7.5 billion embedded microcontrollers were sold. There are about 50 in your car. You probably have 100 around your house right now, just in little things like your toaster and your VCR controllers. Those are all candidates for being networked, because if the last two decades have taught us anything, it’s that connectivity, not computation, makes something valuable. I could give you the fastest computer in the world with no Internet connection. How useful is that?
TR: How might these embedded networks have an impact?
Poor: Say you’re on your way to work Let’s put a wireless embedded node in every streetlamp. Why would you do that? The town of Brookline, MA, spends about $200,000 a year to drive someone around in a truck. And they have to do it both day and night, because in the day they’re looking for lights that are stuck on, which is costing them money, and at night they’re looking for lights that are burned out. Both are problems. If all these lights were networked, they could just trickle their data back slowly to the control center and provide an alert as to which lamps are burnt out or stuck on.
TR: That would certainly help the public works department, but how would it affect the rest of us?
Poor: Once you’ve got the nodes in place, the entire town of Brookline has a wireless mesh spread over it, which can be used for other purposes. This is Metcalfe’s Law-that is, a network’s value increases with the number of things connected to it. So you put a wireless network node in every bus and as it drives past a street lamp, it notes that the bus is there and it can zip the information four blocks ahead to the next bus kiosk that says that #39 will be here in three minutes. And put one on the kids who are on the bus, and it can make sure they got on the bus at the right place and got to school at the right place and nothing happened in between. We can skirt the issues of privacy here, because this is something their parents want them to have. And this is all overlaying a network that was installed for an entirely different reason. I like to call it Moore’s Law meets Metcalfe’s Law. Silicon has gotten cheap, wiring has not. So if you build networks that make their connections via silicon radios rather than wire, they’re going to get cheaper, which means they can get more pervasive. You can’t do that if it’s a wired network.
TR: What’s the cost of setting up one of your embedded device networks?
Poor: Right now, if you add one of these $5 devices to a $2 light switch, you’ve got on the order of $10 cost. And installing it really means taking a piece of double-stick tape or Velcro and thwacking it on the wall. The fact that you make a self-organizing network simplifies things, so there’s really not much additional labor associated with that.
TR: What do you see as the big challenges in the next year, and next five years?
Poor: It’s difficult to predict where the real problems are going to lie, because it’s really going to be opportunistic-different applications will catch on at different times. The requirements of a system are highly dependent on the actual application, and it will be a delectably messy environment for a while. Coming up with scalable and adaptable architectures that work across multiple applications is going to be critical.
TR: Scaling up a self-organizing device network from a few nodes to a hundred is a problem that lots of people are trying to solve. How big are your networks?
Poor: We’re deploying multiple-hundred node networks now. We have simulated up to multiple thousands and one of our challenges has been to find a physical space to lay out that large a network.
TR: Are you working toward making the network itself into some sort of collective consciousness or intelligence?
Poor: I think it was [MIT Artificial Intelligence Lab Director] Rod Brooks who used to promote behavior over intelligence. You know, he said, insects display behavior and when you put enough insects together, then you start to see something that resembles intelligence. The classic example is termites. One termite by itself runs around randomly, 10 termites will roll dirt into a ball. But you get a couple million of them together and they build these incredibly complex nests. Where’s the intelligence there? So I think it’s misleading to talk about things on the order of light switches and thermostats and strain gauges and tank level centers and such. It may be a mistake to talk about intelligence per se, but each of those points on a network needs to have enough behavior that they will self assemble into a large and scalable network. And then we point to the aggregation. There’ll be some nodes that have more computational power than others, which will do some kind of analysis, and distill the data down to more useful information. Is that intelligence? A little bit. It’s more like behavior.
TR: If you had to boil down Ember’s contribution to one idea, what would it be?
Poor: We took the gutsy move of going from what was a fairly pure research topic into commercial systems. There are other people that were working in defense systems, and that’s nice because there are always clear funding paths for that. So I think we were one of the first to actually open up embedded device networking to a commercial audience. The gratifying thing is that there’s now a lot of other people in the space, and we think that has validated the market.
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