Is Google and Nest’s Thread a ZigBee Killer?

ZigBee may soon start looking a bit Threadbare, writes Engerati member Nick Hunn.
Published: Mon 21 Jul 2014

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Today, Google and Nest launched the Thread Group – a new wireless network for home automation. It’s not the first and it won’t be the last, but it has some important names behind it such as Google and Nest.

But, others in the consortium are interesting. For instance, ARM is there. Today they power most of our mobile phones, providing the IP behind the processors in billions of chips. But, they have a vision of being the microprocessor of choice for the Internet of Things. Their processors will be smaller, cheaper and lower powered. They will also provide the first opportunity for chip vendors to think about trillions.

ARM’s inclusion in the group is an obvious step in their process of acquisition and investment in IoT companies.

Samsung is also there but so are some very large names in home automation, such as Big Ass Fans and Chubb. And, the ZigBee community must also be worried that Freescale and Silicon Labs now complete the list of founder members.

ZigBee doesn’t work

The important point here is that Thread is not ZigBee. It works in the same spectrum and uses the same chips. While it is also a mesh network, it is not compatible. As the Thread technology backgrounder says, they looked at other radio standards and found them lacking, so they started working on a new wireless mesh protocol.

To put it more crudely, it is Google and Nest saying “ZigBee doesn’t work”.

This isn’t the first time that Google has proposed a wireless standard. In 2011, they used their I/O conference to announce an initiative with Lighting Science Group to produce a home automation wireless mesh standard operating at 868 – 915MHz. I didn’t think that would shake the world and it didn’t. However, this time around it is different. Nest is not Lighting Science Group. To many people, even before their acquisition by Google, Nest was home automation. They have released the API to their products and built up an impressive roll-call of partners, including Mercedes-Benz, Whirlpool, Jawbone, Logitech, Chamberlain and LIFX. Now that they have the resources of Google, it’s clear that Nest is not going to stand still. They are already calling for interest from other companies and they plan to release a specification for Thread later in 2014.

My guess is they may miss that date, not least because every other wireless standard I’m aware of has been late. Wireless is difficult and as more partners come on board they will find bugs which need to be corrected. But, the release will happen. The Thread site says that it is already in products, which answers a long-standing question about Nest devices.

When the Nest thermostat was first launched, teardowns reported that it contained a Texas Instruments CC2530 chip, a 2.4GHz chip which is normally used for running ZigBee. However, Nest never announced ZigBee compatibility or showed this working with any ZigBee device.

There was speculation that it had been included in the event that energy utilities wanted to connect the thermostats to smart meters, not least because Nest was wooing them to be part of their demand response programs.

Other theories were that it was included in the event it was needed. But, in that case, why populate the board and increase the cost? That theory was dispelled when the second generation thermostat came out and teardowns discovered that the TI chip had been replaced by an Ember EM357. You don’t do a chip change unless you’re using it. And the same EM357 duly appeared in the Protect smoke alarm. The inference was that Nest was using these chips for something else. But, what?

Today, we can assume that the “something else” is Thread.

So far, I have never seen anyone claim that they’ve seen any activity from these chips, but if it is low power, it would be very intermittent and difficult to see within the Wi-Fi activity. If it is in use, that will provide a very useful experience base for the Thread partners to help hone their standard.

The ZigBee community will be alarmed. Silicon Labs acquired Ember last year. Ember was very much the founder and poster child of ZigBee mesh which, as a standard, has struggled to get a hold in any market other than smart meters. Within that market, manufacturers have used the older non-IP version of the ZigBee standard. Although ZigBee 2.0 has moved to support 6LoWPAN, the Thread announcement probably killed it at birth.

Freescale is another ZigBee provider. The fact that Freescale and Silicon Labs are working on Thread has a serious consequence for ZigBee. The companies that make these basic chips operate with many wireless standards. What is different is the protocol stacks which may require hundreds of man hours of development.

Although the chips may work with any standard, only those which are showing commercial promise will be given the resource to develop the protocol stacks. My guess is that the ZigBee teams, within Silicon Labs and Freescale, have been moved to Thread development. Without that engineering effort, the ZigBee stacks-which still have work to be completed-will wither and die.

A bitter pill

This is a very bitter pill for smart meter manufacturers and utilities to swallow. If the market stops supporting ZigBee and moves to Thread, then it means that utilities have chosen an obsolete technology for their smart meters. Any plans they had to connect to home devices for demand response will need to be scrapped and rewritten. In the utility world, that means a delay of several years and an ever greater distrust of the wireless industry.

Nest’s move to the Ember EM357 may give us a clue about the size of the Thread stack. The website shows us the basic architecture of Thread, which is a lot cleaner than the SEP2.0 approach that ZigBee ended up with. This was heavily influenced by utilities and Government-sponsored academics, resulting in a stack that was a rather bloated committee job which was too big to fit into most existing ZigBee chips. As a result, chip companies came out with newer, more expensive chips with a lot more memory.

Thread talk about their clean piece of paper approach to the design. My guess is that they wanted something that would fit into an existing chip without the need for external flash or a more expensive chip. Their move from the CC2530F256 to the EM357 contradicts the industry trend by shrinking the flash memory from 256k to 192k, suggesting that they already knew the size of the Thread stack and were cost reducing. If they’ve staked their product design on the 192k limit of the EM357, it suggests we’re going to be shown a very efficient protocol stack when the Thread documentation is released.

Bluetooth and Thread

So where does this put Bluetooth? Bluetooth has been less than successful at penetrating the home automation market. This gave ZigBee and Z-Wave a major opportunity to make the most of the running-although crawling might be more accurate since this sector has not taken off.

However, this has changed over the last few months. This is due largely to the widespread implementation of Bluetooth Smart (the standard formerly known as low energy) in tablets and smart phones.

It also appears to be the connectivity standard of choice for in-home connections within Android TV. (Incidentally it seems very strange that Thread was not announced at Google I/O last month, when ATV was very much the main theme. If Thread was just a way of getting back at Apple for their HomeKit announcement, you would have expected it to be a highlight of the I/O event.) The two wireless standards can certainly co-exist, but Nest will need to persuade smartphone vendors to incorporate it into their devices. This may prove to be an uphill struggle, particularly with Apple. And it’s important that any home control technology is in every smartphone and tablet, as the lifetime of home automation products will span many changes of phone and tablet.

Bluetooth is certainly not standing still.

Cambridge Silicon Radio has demonstrated a mesh network for Bluetooth, and the Bluetooth SIG is working on IPv6 support and longer range. It could be too early to say whether there is an opportunity for Thread and Bluetooth to come together. It would not be the first time this has happened and large manufacturers can exert a surprising amount of pressure. The home automation market needs consolidation in standards, particularly in terms of interoperability and device management. Whilst it is fragmented, nobody is likely to win.

Z-Wave will also feel threatened. I imagine they will continue to promote the advantage of being a sub-GHz product, which will translate into easier installations. 2.4GHz is not the best frequency for the home as range is a challenge, particularly for the first few devices deployed. While Mesh alleviates that, it requires multiple devices to be deployed before it can compete on range. That, in itself, would argue for a Bluetooth / Thread conflation to push up the number of routing nodes in any home. However Z-Wave has other issues in reaching scale: the limited number of component suppliers and no prospect of support in a smartphone or tablet.

There are still many unanswered questions about Thread. I am therefore recommending that you sign up for their newsletter. I’m not sure why the smart tap on their website drips? Surely it should have asked for a new washer by now? Why is their logo an ampersand rolling downhill? Maybe “and over and over again” is a metaphor for home automation. I’m sure these will be answered. The presence of Thread makes the prospect of home automation becoming a reality look a lot more possible.