Is Google and Nest’s Thread a ZigBee Killer?

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. The big two are Google and Nest, not least because Nest’s products may already be using it. But others in the consortium are interesting. 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 architecture of choice for the Internet of Things. They processors will be smaller, cheaper and lower powered, but will 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 are there (aren’t they always), but so are some very large names in home automation, such as Big Ass Fans and Chubb. And what must be worrying the ZigBee community is that Freescale and Silicon Labs complete the list of founder members.

The important point here is that Thread is not ZigBee. It works in the same spectrum and can use the same chips. It is also a mesh network. But 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’s Google and Nest saying “ZigBee doesn’t work”.

This isn’t the first time that Google has proposed a wireless standard. Back 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. This time around is different. Nest is not Lighting Science Group. To many people, even before their acquisition by Google, Nest were home automation. They’ve 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 are not going to stand still. They’re already calling for interest from other companies and 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. That 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 case 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 case it might be needed, but in that case, why populate the board and increase the cost? That theory was dispelled when the second generation thermostat come 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 something else is Thread. So far I’ve 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 has probably killed it at birth. Freescale is another ZigBee provider. The fact that they and Silicon Labs are working on Thread has a serious consequence for ZigBee. The basic chips these companies make work with many wireless standards; what differs is the protocol stacks which can require hundreds of man years 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 and without that engineering effort the ZigBee stacks, which still have work to be completed, will wither and die.

This is also a very bitter pill for smart meter manufacturers and utilities. If the market stops supporting ZigBee and moves to Thread, then it means that utilities have chosen an obsolete technology to put in 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 which ZigBee ended up with.  That was heavily influenced by utilities and Government sponsored academics, resulting in a stack that was a rather bloated committee job and too big to fit into most existing ZigBee chips.  As a result chip companies came out with newer, more expensive chips with much more memory.

The Thread Protocol Stack

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.

This may all be a good thing for those involved with ZigBee, if not for ZigBee itself.  Over the years ZigBee has been rather promiscuous in allowing its name to be associated with anything that used an 802.15.4 chip, regardless of what sort of stack it had.  In much of the Far East 802.15.4 is synonymous with the word ZigBee and universities have been complicit in churning out graduates with “ZigBee” experience who think that a standard is something you can rip up and rewrite, rendering them largely unemployable.  As a result ZigBee has achieved a reputation for minimal or no interoperability.  Even in smart metering, where it has had most success, there are over half a dozen different versions of the Smart Energy Profile and limited interoperability between manufacturers, even within any one of the versions.

Thread gives the industry players a phoenix opportunity – the chance to walk away from the mess and start afresh, taking the best bits and discarding the albatrosses.  But to do that cleanly they probably need to euthanise the ZigBee Alliance.

So where does this put Bluetooth? Bluetooth has been less than successful at penetrating the home automation market than other low power standards, allowing ZigBee and Z-Wave make most of the running (although crawling might be more accurate – this sector has not taken off). In recent months that’s started to turn around, largely because of 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, which may 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 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’s too early to say whether there is an opportunity for Thread and Bluetooth to come together? It would not be the first time such a thing 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. Mesh alleviates that, but needs 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 have other issues in getting to scale, not least the limited number of component suppliers and no prospect of support in a smartphone or tablet.

There are still many unanswered questions abut Thread, so I’d recommend signing up for their newsletter.  Why is the smart tap on their website still dripping? 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.  Why is it called Thread? I’m sure these will  be answered. But all of a sudden, the presence of Thread makes the prospect of home automation becoming a reality look a lot more possible.


* As always, wireless standards take longer to emerge than predicted, not least because they’re difficult.  I suspect we won’t see the first release until the end of summer 2015.