Bluetooth, babies, and bathwater - Embedded.com

Bluetooth, babies, and bathwater

The Bluetooth Special Interest Group has just released some of the details of Bluetooth 5.0, the latest version of its Internet of Things wireless protocol, to be released to developers later this year. Bluetooth is one of the major contenders in an IoT market that ABI Research projects will grow to over 40 billion devices by 2022. The SIG is also working on a separate follow-on mesh architecture that it thinks will give it an edge over competitive specs such as ZigBee and Thread.

Version 5 enhancements cover the whole range of apps where Bluetooth plays a role: the key element in the beaconing and location services built into most mobile phones; an easy-use personal networking tool that allows people to use their smartphones to access and control devices near them or in their local environment; and a means by which to provide users – but more importantly, the companies that provide the wireless IoT devices – with access and control of literally thousands of devices in a home or a building.

Among the improvements are such things as doubling the peak data rates from 1 to 2 Mbits/second and quadrupling its range from 30 to 100 meters, all with the aim of moving away from the traditional Bluetooth app-paired-to-device model to a connectionless IoT similar to that employed on IoT protocols such as ZigBee and Thread.

“The ubiquitous presence of Bluetooth in the mobile space is a key driver for the technology,” said Andrew Zagani, industry analyst at ABIResearch. “Beacons are arguably the most obvious application related directly to its presence here. The arrival of Bluetooth 5 with its 8X increased broadcast messaging capacity will enhance its opportunities further.”

Zagani said that in terms of applications such as the smart home, a key selling point will be that Bluetooth as it is currently configured does not require a separate gateway to be purchased but can use an existing smartphone or tablet device to control smart home devices.

“This removes a significant barrier to adoption and reduces the complexity and cost of developing separate gateway devices. Again, the increased range from Bluetooth 5 will also allow for greater coverage, enabling control of smart devices throughout the whole home and even outdoor applications.”

But much of the success of Bluetooth in the IoT and mobile beacon markets will depend on yet another enhancement: its Smart Mesh specification, and whether it can bring the advantages of that approach in future markets without affecting the use of the protocol in present beaconing and personal area networking apps.

The Bluetooth Smart Mesh specification is expected to be announced separately by the end of 2016. If the Bluetooth Special Interest Group is successful in its aims, ABI Research projects that its use in building smart home devices will grow by over 75 percent between 2016 and 2021 (see Figure).


Figure. ABI Research projects that Bluetooth device shipments will total over five billion units by 2021. While its use for beaconing in smartphones will remain the largest segment, significant growth is expected for the connected home, which could at least double. (Source: ABI Research)

Enough details have emerged about Smart Mesh to get companies who are members of the Bluetooth SIG excited about the possibilities. For one thing it greatly expands the area and number of nodes it can support and will also allow implementation of smart apps that take advantage of the data shared across nodes. The mesh will use a flooding approach that is supposed to be easier to implement than the IEEE 802.15.4-based ZigBee routing scheme based on Ad hoc On-demand Distance Vector (AODV). However, it makes some compromises in terms of latency compared to the alternatives in order to conserve energy.

“The Bluetooth SIG’s adoption of mesh is primarily driven by the needs of the IoT market,” said Adnan Nishat, marketing manager for Bluetooth SoCs at Silicon Laboratories. “Many of today’s IoT applications (connected home, building & industrial automation, lighting, smart meters and many others) require control, automation, and co-ordination between a large number of nodes.”

He said point-to-point solutions (and multi-hop alternatives such as Bluetooth scatternets) were the first attempts but are far from sufficient. “Home devices require reliable and robust communication with very low latency. The move into mesh by the Bluetooth SIG is to provide this capability.”

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According to Zagani, mesh will allow coverage of much larger areas and a much greater number of end devices where it has previously been limited by its much shorter range. “By relaying messages from device to device, Bluetooth mesh will allow for increased network coverage, potentially opening up new opportunities in commercial, industrial, and smart city applications, in addition to the strengthening its position in the smart home.”

He said the increased range between nodes enabled by the new Bluetooth 5 enhancements will also complement the new mesh networking profile when it arrives, allowing for installations of a much greater scale. Mesh networks also enable each node to share information about the context it is in, increasing the intelligence level of the overall network and allowing more sophisticated context-based applications to be developed, addressing one of Bluetooth’s greatest limitations when compared to competing technologies such as ZigBee.

But a big problem facing the Bluetooth SIG's Smart Mesh working group is how to preserve the familiarity and user friendliness of the current star-based piconet architecture developed originally to allow smartphone developers to easily build a variety of beaconing and location applications. Though limited to a single master controlling seven other slave devices, developers – and some tech-savvy end users – have created personal area networking applications that allow direct control of devices in their personal space.

Beyond broad descriptions of the goals of the new Smart Mesh specification, little is known about how the working group will achieve the apparently contradictory roles of being both a personal area networking building block attractive to today's still IoT-skeptical consumer and a protocol that will be competitive when the IoT requires networks that allow control of thousands of devices.

While the commercial opportunities for the IoT in the next ten or twenty years are compelling, a variety of market studies indicate that end users are less than eager for such a world. They will have to be sold on it. One reason Bluetooth has gained traction in the nascent IoT market is because it is designed to give end users a real and immediate benefit: control of the devices in their immediate environment, not the hundreds or even thousands of others in the buildings they are in.

So the method the Smart Mesh working group uses to create an industrial strength Internet of Things protocol to allow the interconnection and control of literally thousands of end devices is very important.

Everyone seems to agree that the best mechanism would be to implement Smart Mesh as a protocol on top of the existing Bluetooth standard-based stack to ensure an upgrade path for the large installed base of Bluetooth low-energy devices. But what is the best way to do that? According to Bluetooth developers I have talked to there are several ways by which mesh capabilities could be incorporated into the specification, all of which will require careful tradeoffs to preserve the easy and direct methods used currently.

One is simple replacement: do away with the current star-based piconet option altogether and replace it with the mesh. To me this does not seem a very likely possibility, as it would undercut Bluetooth's use as a beaconing tool and as a simple personal area networking tool. An alternative is to make use of Bluetooth's Profile option, leaving the piconet in place and incorporating a Mesh Profile, as was done in Bluetooth 4.1 for IPv6 wireless connectivity. Another possibility is to incorporate mesh directly into Bluetooth, and instead make the more limited, but still widely popular, piconet configuration available as a Profile.

Right now, Bluetooth's edge is its familiarity to developers of beaconing apps who have transitioned quickly to personal area IoT networking designs in which the smartphone can be used to create IoT networks, not only in the home, but in a variety of industrial and building environments as well.

So the main challenge facing the Smart Mesh Working Group will be to find some way to avoid throwing out the baby with the bathwater: preserving the mechanisms by which users gain immediate control of devices around them but at the same time come up with a protocol that will better serve the needs of the IoT market five or ten years in the future.

The Bluetooth Smart Mesh Working Group was formed in the summer of 2015 to come up with a viable approach by the end of this year. I would have asked for more time, given the market and technical complexities involved in making this transition.

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