The military uses for wireless technology are persuasive. For example, pilots can fly above a war zone and drop thousands of small wireless sensors, the size of a small pebble and costing a dollar apiece, over the terrain. As soon as they settle the devices start communicating with each other, weaving themselves into a dense digital mesh. They pick up vibration and sound, so they can identify advancing troops. The sensors can also detect the presence of nuclear, chemical or biological agents. The information they pick up is relayed to a satellite. For power, they "scavenge" energy from the environment, using solar energy or temperature changes.
The civilian uses are equally impressive. Forest rangers can drop the sensors from aeroplanes to detect fires, showing their exact location and how fast and in what direction they are spreading. Smaller versions the size of grains of rice can be used by airlines in the innards of aircraft to check for the presence of large insects or rodents that might interfere with the wiring. Still smaller versions the size of specks of salt can be added to paint, turning entire surfaces into wireless sensors that can detect motion or act as smoke alarms or security systems.
The trouble is that as yet such sensors do not exist. But a lot of practical work is already going into making them a reality. A version of the military scenario above, for instance, was rehearsed in an experiment in March 2001 at an American Marine Corps base in California. Around a dozen nodes the size of a matchbook were released by a miniature unmanned aircraft. They were able to measure the speed and direction of vehicles from ground vibrations. This proved that the technology, although still at an early stage, was viable.
The military experiment was supported by America's Defence Advanced Research Projects Agency (DARPA) and arose from a programme called "smart dust" at the University of California at Berkeley in the 1990s. It created some of the technical foundations needed for sensor networking, such as a pared-down computer operating system, database and protocol for sensors to send traffic (but "sleep" as much as possible to prolong battery life). The technologies are open standards, so may be used freely by other firms, just as the underlying protocol of the internet is open.
With DARPA's early support a gaggle of companies have emerged, such as Dust Networks, Arch Rock and Moteiv (from research at Berkeley) and Ember (based on work at MIT). Other companies, such as Crossbow Technology, Millennial Net, Sensicast, Tranzeo and MicroStrain, are applying the innovations to their existing technologies. Wireless-sensor technology is now moving out of military testing grounds and into the commercial world. It is used for things like monitoring and controlling industrial machinery, automatic temperature regulation in buildings and keeping tabs on the environment.
Whereas M2M communications generally involve wireless devices attached to equipment such as cars or vending machines that link up to the cellular system, sensor networks use small chips that are often embedded into the device and use a local-area network that may never connect to a larger one such as the cellular system or the internet. For the moment the sensors are not yet widely deployed: the technology is still maturing and customers need convincing that it is worth having. But the idea is gaining momentum. Once the volume goes up, prices will come down and follow-on innovation will speed its adoption.
A good place to get a glimpse of new wireless technologies in action is BP's Cherry Point Refinery in Blaine, Washington. Built in 1971 on almost four square miles (10 sq km), it has a daily throughput of 225,000 barrels of crude oil. The site also produces 8 percent of the world's calcined coke, which finds its way into one out of every six aluminium cans. Modernising the plant to keep it efficient is costly; BP says it has spent nearly $500m on this over the past ten years. Fields of tanks need to be monitored for operational, safety and environmental purposes. But snaking wires across such a huge area is expensive.
New wireless technologies are critical, explains Tim Shooter, who works on future technology at BP. They allow more operations to be monitored and controlled and save money at the same time. The average refinery has around 3,000 "instrumentation points" where data on things like temperature, flow, humidity and vibration are collected; managers would be even happier with 10,000 points if only they were less pricey. The cost of the basic monitoring devices ranges from $1,000 to $10,000 apiece. Although adding wireless functions to these sensors almost doubles that cost, it reduces the price of installation by 50-90 percent — and installation makes up most of the total cost. By upgrading some processes to wireless systems, Mr Shooter believes each refinery will be able to save at least $1m a year.
Getting Better All the Time
Until a few years ago wireless technology was not up to the job. The "big leap forward", says Mr Shooter, is that the new technologies are far more reliable in hostile industrial conditions and the communications protocols are more intelligent.
One notable innovation is "ad-hoc mesh networking" in which each node on the network — eg, a sensor on a water pump — is both a transmitter and a receiver and can join the network whenever required. Earlier wireless technologies assumed that sensors would send data to a specific receiver, in a hub-and-spoke fashion. This had many drawbacks. For a start, it made the system inflexible. If you added a new node, the whole system had to be reconfigured and the network became harder to manage. And if a central receiver failed, the whole system collapsed.
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