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Zigbee And The Waggle Dance

In 1973, Karl von Frisch received a Nobel Prize for his work on honeybee communications.  Among other accomplishments, he decoded the waggle dance, the method by which a honeybee tells others where it found pollen.  Twenty-five years later, the Zigbee Alliance began promoting a data communications scheme inspired by the waggle dance.  In 2003, Zigbee became an IEEE standard, and in 2006 it was revised and improved.  Today it is a core technology for local Internet-of-Things networks, controllers, devices, and sensors installed by builders ranging from giant data service providers down to do-it-yourselfers.

waggle dance
Dance Of The Honeybee
When a honeybee returns to its colony
after finding food or water
it shares details of its discovery
in a dance that carries a message

Zigbee networks can share spectrum and controllers--such as tablet computers--with Wi-Fi networks.  In smart home applications, for example, high data rate devices like security cameras will often use Wi-Fi to talk to a controller, while low data rate devices, such as smoke alarms, door and window sensors, and motion detectors, are likely to communicate using Zigbee.  The local controller may talk to other devices such as PCs, smartphones, and tablets using Wi-Fi or a hardwired LAN.  IoT developers, by using tablet computers that resemble low-end general purpose Android slates for controllers, take advantage of the inexpensive hardware and software.

A Zigbee controller tablet can manage multiple types of networks the way a similar small computer does in a smartphones or general purpose tablet.  Instead of NFC or Bluetooth or GPS radios, an IoT tablet might have transceivers for Zigbee or another IoT local network scheme.  Like general purpose smart devices, IoT controllers have Wi-Fi radios and software that makes it easy to integrate the IoT with local equipment and also provide communication via WANs to remote server farms managed by home security companies or other providers.

The Android platforms used to manage IoT devices let the local controllers run some ordinary apps.  For instance, an end user might want to check a weather forecasting app before adjusting thermostats, lighting, or other environmental controls.  The solution is to install a standard weather service app.  The weather app runs right on the Zigbee controller.  It is the very same app available to users of Android phones and tablets via Google Play or another app source or a variation of that app provided by the maker of the controller.

zigbee radio
Zigbee Radio
This device, shown with its antenna, sends and receives
data over a Zigbee network, performing all the repeater functions
required to create a mesh communications system

However, even though IoT controllers share quite a bit of technology with run-of-the-mill Android tablets, the Internet of Things is in some ways quite different from the Internet of mobile clients.  IoT really needs Zigbee or an alternative local networking scheme that has technical and economic characteristics similar to those offered by Zigbee.

One of the most important characteristics of Zigbee is its very low power requirement.  A Zigbee radio that fits inside a magnetic door or window closure sensor might pack a small battery that lasts three, four, even five years.  Zigbee devices are also smart and dependable.  A Zigbee smoke detector rarely needs a fresh battery and, when the battery starts to run low, it issues a distress call telling its controller to initiate a service call.  A Zigbee light switch might not need wiring at all.  Instead, the energy required to flip the switch on or off could generate enough power to fire up a radio and sent a command as a short burst of data.  There are corresponding smart devices for the appliance end of things.  For instance, there are light bulbs with Zigbee radios that can be adjusted by remote control; the adjustments include brightness and hue.  Having these radios alive all the time doesn't lead to large power bills; they use milliwatts.

zigbee logo
Zigbee Alliance
This organization keeps Zigbee open as it provides documentation,
promotion and technical advice for participants and end users

With Zigbee, the low power means a short range.  While one Wi-Fi hub can fill a typical home with plenty of signal, Zigbee might be able to reach only 50 to 100 feet, and possibly less.  Consequently, the star network topology used with Wi-Fi hubs simply won't work in an IoT setting.  Instead, Zigbee uses a mesh system.  If a controller reaches out to talk to a device, such as a thermostat, and it cannot reach the target directly other Zigbee devices within range will step up and act as repeaters.  Similarly, a sensor trying to send a message to a controller that is out of reach asks its neighbors to repeat the message.  They will do this until the information gets to its target and the receiving device gets an acknowledgement back to the originator of the message.

By naming its scheme after the dance of the honeybee, the Zigbee Alliance elevated local networking to a higher philosophical level.  The waggle dance is a social communication, the Twitter of the insect world.  The way it works, when a bee returns to its hive excited by a significant find of suitable flowers, it will move into the middle of a group of worker bees and dance around in a figure eight pattern.  During the middle portion of the path the bee will waggle from side to side.  The orientation of the dance tells other bees about the direction to the source of pollen.  The waggle pattern provides information about the distance from the hive to the flowers.

Now it turns out that the waggle dance is only used if the returning bee has come a considerable distance, typically more than 100 yards.  If the returning bee has found flowers closer to the hive it performs a different dance.  In any event, in a lively hive every bee coming back with a waggle dance motivates several bees to search for the flowers it has found.  These bees may in turn dance up and motivate even more workers; they are like the repeater radios in an electronic Zigbee network.

Zigbee isn't the only local networking scheme used by IoT technologists, but it is the leading open standard, and its popularity seems to be growing.  Its two main rivals, Z-Wave and Infineon, are proprietary.  Their creators are happy to license the technology and they also do a pretty good job of policing their licensees to enable end users can rely on interoperability within either of their schemes.  The Zigbee Alliance is trying to keep things orderly, too, but as is the case with other open standards, Zigbee is somewhat more prone to suffer compatibility issues.  Still, the openness has been a fabulous magnet for developers, and it is one reason Zigbee apparatus is the primary IoT offering for do-it-yourselfers at Lowe's.  Smart home services from Comcast and Time Warner Cable also use Zigbee augmented by Wi-Fi for cameras and some other devices.  By contrast, Verizon's smart home services use the proprietary Z-Wave local technology.  Even if Verizon is not in the Zigbee camp, it has a pretty complete set of devices.  It is too early to say whether Zigbee will evolve in ways that put it far ahead of other IoT local networking schemes, but at the moment it looks like Zigbee is pulling ahead.

The IoT world will soon include its own wide area networking scheme, one that could handily beat mobile telephony and wired WAN alternatives.  The first noteworthy player is Sigfox, based in France, which is piloting a service in the Silicon Valley area, one that spans the peninsula from San Francisco down to San Jose.  Sigfox hopes to offer networking that costs $10 per year per hub and possibly, for customers with many hubs and low traffic, a lot less than that.  Sigfox radios use low power and low data rates but have a far longer reach than local networking technologies like Zigbee.  In the USA, one of the outfits that will piggyback on Sigfox is Whistle, which will offer a communicating pet collar and a support service to help track Spot and Puff.

IBM is well aware of Sigfox and at least one of its customers, an IoT company called Worldsensing.  Four years ago, IBM gave Worldsensing a 2010 Smart Camp award for its FastPrk smart cities parking system.  Since then, Worldsensing, using a Sigfox WAN, lit up what it says it the largest automated parking space management system in the world, in Moscow; it has been running for about a year and a half.

Nevertheless, even though its PR folk are buzzing away, IBM has not yet developed a significant presence in the part of the Internet of Things where networked gadgets are routinely doing the waggle dance.  One would think this would come naturally to the company, and perhaps it soon will.  After all, Bee is IBM's middle name.

— Hesh Wiener May 2014


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