Zigbee® 3.0 Green Power: Saving the Day for IoT Connectivity

With the proliferation of apps and devices, a standard is needed to ensure simplicity on the user end, reliability of connections, and interoperability of products from a variety of manufacturers.


With its 2014 release of Zigbee 3.0, the Zigbee® Alliance announced the unification of its wireless standards to a single standard named Zigbee 3.0. This standard seeks to provide interoperability among the widest range of smart devices and give consumers and businesses access to innovative products and services that will work together seamlessly to enhance everyday life.

Zigbee 3.0 also includes Zigbee Green Power. Zigbee Green Power was originally developed as an ultra-low-power wireless standard to support energy harvesting devices (i.e., devices without batteries that are able to extract their energy requirement from the environment.) Green Power is especially effective for devices that are only sometimes on the network (when they have power). The Green Power standard enables these devices to go on and off the network in a secure manner, so they can be off most of the time.

As an ultra-low wireless technology, Green Power is also a very effective option when using battery-powered devices, as it enables them to run off a battery for years. Green Power also allows for low-cost end nodes to communicate with the rest of the network, specifically in situations where there is no meshing required.

What Is Meshing?
Meshing has long been an intriguing concept in networking technology, so let’s take a quick look using a familiar Wi-Fi meshing scenario. The basic home Wi-Fi setup today is a cable or DSL router that wirelessly connects with our tablets and smartphones. If it doesn’t work so well, we install a repeater as an intermediate. These days there are sets of router boxes available that are preconfigured to wirelessly work together to cover our sprawling mansions or tidy cottages, as the case may be, including that room behind the garage where we escape to play video games. Reliable, speedy coverage.

So how can meshing help? The concept is a simple one. If I am in one corner of the house with my smartphone, and a laptop is closer to me than the router, then I just hop (mesh) via the laptop—as long as it is powered on. Meshing is generally self-configuring: everyone on the network helps everyone else to reach the router and via the router, the internet. And if that intermediate laptop is turned off, then my smartphone finds another device. Meshing can also be self-healing; it’s no problem if one link to the router breaks down, as the network will (hopefully) find another one

So, what’s the downside? This is one of those situations where sympathetic, pioneering technology clashes with the day-to-day grumpy consumer, who wants reliable connectivity all the time without being bothered with much else.

Unfortunately, there are three general problems with meshing—and this is true whether we’re looking at Wi-Fi or Zigbee (or Thread). The first is intermittent failures, the second is related to battery life, and the third is cost.

Meshing Has Issues; Zigbee Green Power Has Answers
Intermittent failures are usually recognized as a nasty network problem—sometimes it works, sometimes it doesn’t. Nobody knows why, exactly, so nobody can really fix it. In the meshed Wi-Fi example above, maybe your smartphone network connection depends on whether your son leaves his game station on or off—and good luck figuring out that one.

And then there’s battery life. In a meshed Wi-Fi network, your laptop might become an intermediate node. Suddenly, your laptop is running low on battery, because someone else in the family was (perhaps unknowingly) using your laptop as a hopping point (“meshing node”) for watching YouTube videos on his tablet. The meshing network has actually created a battery issue for a device that wouldn’t have had a problem otherwise.

And finally, there’s a cost issue. Every node in the network is not only an edge node (“a node doing something”), but it also needs to be able to function as a meshing node—and it needs to be equipped to do so. In practice, this means running more software on a larger processor with more memory. And meshing nodes may also have to be “on” constantly, which requires a larger and more expensive battery, while an edge node only has to be turned on when triggered.

But here is where the Zigbee 3.0 with Green Power saves the day. Zigbee enables meshing, but does not require it. Edge nodes can easily be Green Power networked, and if the area to be covered exceeds the range of a single router, multiple routers can work together to establish a backbone network that all the edge nodes can connect to, without carrying the overhead themselves to be meshing nodes.

Is Meshing an Outdated Concept?
In the context of a home, meshing is a band-aid solution for a poor radio that lacks range. Meshing would not be necessary with a powerful enough radio, running on a coin cell battery, that enables you to reach the router—even if it is not located in the most optimal center of the home. These radios may not have existed 10 years ago, but they exist today. This makes meshing a fringe solution for exceptional radio coverage problems. And these days, multiple radio frequency Wi-Fi channels are more often implemented, not meshing. Zigbee can do that, too.

The self-healing “benefit” of meshing is also a bit of a relic from the days when networking equipment was not as reliable as it is today. Single points of failure were red flags, and mesh networks with multiple paths were seen as a great plus—enabling rerouting via alternative connections at the moment of breakdown. But with today’s reliable networking equipment, the need for avoiding single points of failure is more or less gone.

Still there are many situations where meshing is a good and practical solution, e.g. where coverage is limited, or where there is lack of infrastructure.

How Does Green Power Work?
As a standard feature of Zigbee 3.0, Green Power’s simple networking protocol essentially brings all the complex networking features to a proxy (usually the router), while the Green Power node focuses on making sure that the essential signal—whether a temperature measurement, a command to turn on a light, reporting whether a door or window is open or closed—reliably reaches a router for further consumption. As mentioned, Zigbee Green Power features ultra-long battery life ¬– and in the case of energy-generating light switches, there is no need for batteries at all. Zigbee Green Power is fully integrated with Zigbee 3.0 and fully compatible with all the services that the Zigbee 3.0 delivers, from installation to security, and from ease-of-use to maintenance.

Green Power Works in Simple and Complex Scenarios
At the simplest end, it enables low-cost implementations of standard, standalone solutions. This covers most of the Zigbee applications in the market today. For example, if you have a few lamps, a dimmer-switch and a gateway, then to connect the lamps to the internet, you only need Green Power. As simple as that—no meshing capability required.

For more extensive solutions, Green Power enables the building of a simple Zigbee star network in your home. Or there can be multiple stars dropping from a single backbone in the case of a larger building installation. Either way, Green Power eliminates the disadvantages of meshing— intermittent connections that are difficult to diagnose, and unexpected situations where sensor nodes suddenly and quickly run out of battery power.

Green Power also allows for a Zigbee infrastructure that is fully aligned with the Wi-Fi infrastructure in a building. It is useful to note that a Zigbee radio has a comparable or better range than a Wi-Fi radio. Zigbee (IEEE 802.15.4) is essentially low-power Wi-Fi (IEEE 802.11).

The practical fact is that both Zigbee 3.0 (with Green Power) and Wi-Fi integrate in a single router box, simplifying and cost-reducing the overall networking infrastructure for consumers or enterprise customers, and paving the way for the real Smart Home as part of the Internet of Things. But only Zigbee 3.0 networks use meshing when it really adds value—the real power of Green Power.

Cees Links is GM of Qorvo’s Wireless Connectivity Business Unit. Links was the founder and CEO of GreenPeak Technologies, which is now part of Qorvo. Under his responsibility, the first wireless LANs were developed, ultimately becoming household technology integrated into PCs and notebooks. He also pioneered the development of access points, home networking routers, and hotspot base stations. He was involved in the establishment of the IEEE 802.11 standardization committee and the Wi-Fi Alliance. He was also instrumental in establishing the IEEE 802.15 standardization committee to become the basis for the ZigBee® sense and control networking. He was recently recognized as Wi-Fi pioneer with the Golden Mousetrap Lifetime Achievement award. For more information, please visit www.qorvo.com .



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