Bluetooth IoT IoT applications Network Technologies Standards (802.11)

Unified ZigBee/Thread platform comes closer

ZigBee apps library will run over Thread as prelude to interoperability and testing program, and possibly full merger

The likely outcome of the smart home standards race – a head-to-head between Bluetooth LE (BLE) and a unified 802.15.4-based protocol – came a step closer this week, as the ZigBee Alliance announced extended cooperation with rival Thread Group. This sets the stage for Google to achieve its goal of uniting those two ecosystems, bringing together the two main wireless mesh platforms built on the IEEE 802.15.4 physical layer.

Google is the eminence grise behind the Thread Alliance, which was set up in July 2014 to promote the protocol – an implementation of the 6LoWPAN standard devised by Google subsidiary Nest – as the de facto technology for smart home personal area networks (PANs). As such, it was looking to influence the entire smart home platform from connection to application to device, via activities like Thread, Android/Brillo and Nest. That set it up against the major existing WPAN players, ZigBee and BLE, and while the web giant was public in its appeals to the ZigBee community to join forces, the initial reaction was cool.

However, the two groups have been getting closer. Some vendors, like Freescale, Silicon Labs, Greenpeak and NXP, have launched platforms that support both specifications, while in April, the two alliances agreed to define a spec for running ZigBee’s application layer over Thread. This allowed for interoperability, and gave ZigBee devices a path to a native IP network (one of the reasons Nest did not adopt ZigBee in the first place).

At this week’s Consumer Electronics Show (CES) in Las Vegas, a more far-reaching cooperation will be announced, which may prove timely, given that the Bluetooth SIG is promising significant enhancements to its own platform this year – including plans to fill a major gap in its standards, support for mesh.

The ZigBee Alliance says it will create an end-to-end IoT development platform that allows its applications library to run over Thread’s IP-based protocol. An extension of the 2015 pact, this is possible because Thread operates at the network layer only, while ZigBee is built around multiple multilayer profiles for different target applications (though it is in the process, with the upcoming ZigBee 3.0, of harmonizing most of these).

Of course, it is not hard to see the logic of combining the two technologies completely over the year ahead. In its statement, the ZigBee Alliance said it was broadening the options for its members, notably by adding native IP support, but also driving “industrywide standards unification opportunities for the IoT”.

That would avoid a showdown with Thread, which has the backing of Google’s powerful IoT ecosystem as well as major players like ARM and Freescale. Although ZigBee is far longer established, and has a broader platform which can extend to multiple layers and target markets, its progress has been limited by fragmentation and development complexity. Bluetooth, building on its ubiquity in mobile devices, has the upper hand, and some other candidates, notably Z-Wave, also retain strong presence in the home market, while ZigBee’s traditional stronghold has been industrial control.

The first step will be to add Thread compatibility to the ZigBee library, following the completion of an evaluation process kicked off by the liaison deal agreed in April. Then, the two industry alliances will devise a “roadmap for specifications, branding, and a complete test and certification program” for ZigBee-over-Thread, which should be ready in the third quarter.

The ZigBee Alliance said the combined solution will be just one option for its members, but will “streamline product development, improve interoperability and ultimately enhance the consumer’s experience in the connected home across a variety of smart IoT applications”.

Tobin Richardson, president and CEO of the Alliance, said in a statement: “We are now taking an important step toward IoT unification by adding compatibility with the Thread networking stack and its IP underpinnings to the ZigBee Alliance’s solutions portfolio. This portfolio spans all network layers and critical energy harvesting and other foundational technologies, and is supported by all necessary interoperability and marketing solutions.”

Chris Boross, president of the Thread Group, said: “Bringing ZigBee’s application layer to Thread-enabled devices will simplify product development and increase interoperability, encouraging the Thread ecosystem – and the connected home – to flourish. Our organizations share many of the same members, and we look forward to collaborating with the ZigBee Alliance to offer the market a combined solution for the connected home.”

This harmonious outcome was far from assured when Thread made its debut 18 months ago. The decision to promote a new implementation, rather than adopt ZigBee, was widely seen as Google’s bid to control the agenda, though the official reason was the lack of IPv6 support in ZigBee.

Thread’s remit was to standardize the physical links between objects in a home around IEEE 802.15.4 radio, to ensure interoperability for sensors and devices from all vendors, and it chose a variation on 6LoWPAN – effectively a version of IP for the embedded space – because this was already in use at Nest, and because it would future-proof the home IoT against running out of address space. A pure 6LoWPAN platform was rejected, according to Nest, because of some security weaknesses.

But initially, the ZigBee Alliance did not leap into bed with Nest too readily. Its initial response to the launch was to say: “Thread appears different from ZigBee, which addresses both the network and application level necessary for success in the IoT device market and has led ZigBee to be deployed in tens of millions of devices around the world. Thread does not seem to provide the higher level standardization to ensure interoperability between devices.”

However, it promised to evaluate the new challenger and noted that five of the seven Thread Group founders were also Alliance members, pointing out that “this connection makes it that much more likely to develop a path for collaboration”. That collaboration is real now, and should allow ZigBee’s technologies to survive and grow in the smart home, even if, in time, they become submerged into a common Thread-orchestrated platform. By contrast with the fragmentation of ZigBee’s profiles and interest groups, Google – as Android shows – is a master of open sourcing its inventions while really keeping them under its control. That track record of driving mass adoption and developer support may well prove to be the vital element – more important than any technical considerations – which converts the ZigBee (and pure 6LoWPAN) communities.

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