The appeal of reliable, robust, and low power wireless networks using mesh principles has long been obvious, in both the industrial and domestic environments. To succeed in the latter, it is imperative that operation is simple, out-of-the-box, and faultless. For the homeowner, anything other than simple set-up and consistent operation means a product returned to the store. Similarly, while early adopters might settle for proprietary families of devices, the full potential of a market sector can only be realized when products from multiple sources can be used together. Standards are required.
The sequence of events triggering standards is familiar. The bright idea of the moment takes hold in the industry; there is more than one concept of how the idea might be set on course to become a successful product line; groupings and collaborations take root; and in a very short time, competing candidates vie to become, ‘the standard’.
The basic ideas of low-power, modest-data-rate RF protocols for wireless monitoring and control applications date back more than 20 years. The Zigbee Alliance was constituted in 2002 and has developed a broad-ranging standard. It currently has specifications that span a range of application spaces including home automation lighting control, and smart energy. Member companies now have many millions of products deployed in markets worldwide.
Also present in the home-automation networking space is Bluetooth, coming from a different starting point, as it was conceived to enable wireless point-to-point, device-to-device data links. Through its evolution through Bluetooth Low Energy (Bluetooth LE), Bluetooth recently gained range and throughput enhancements (albeit not concurrently) in the latest iteration (Bluetooth 5) and mesh networking support with the Bluetooth mesh 1.0 release. The Bluetooth Special Interest Group (SIG) reports market success for its mesh network option in, in particular, the smart-lighting sector. Bluetooth LE is supported natively in all currently available smartphones and tablets, which the Bluetooth SIG sees as an advantage because it offers consumers a familiar interface for controlling wireless home-automation devices.
Dotdot is not, therefore, a new standard in its own right – the Zigbee positioning is that it is a “common layer for IoT [devices] with Thread as a common platform”. Dotdot also isn’t a ground-up exercise but is based on application-level features already present in the Zigbee specification – the Zigbee Cluster Library (ZCL). ZCL, now “re-branded” as Dotdot, is a set of commands and attributes, spanning multiple Zigbee profiles, that a developer uses to construct products that will interoperate with products from other makers, or that will use Zigbee public profiles (for example, Zigbee Smart Energy). In an analogy with the App Store model of smartphone usage, Dotdot will enable applications to run on any suitable, and compliant, device.
Standards wars are resolved in a number of ways; there may be a process of attrition, with some contenders disappearing; or one of collaboration and convergence. Help may also come from the hardware part of the equation. Successive generations of integrated circuits in a particular technology space build on experience gained; and integration levels increase. In early generations of a product line, there may be different silicon for different firmware/software standards. When later iterations are taped out, the optimum choice for configuring the feature set may be to produce a multiprotocol part that will accommodate all of the relevant protocols and standards freeing the developer from the risk of narrowing his or her options too soon.
An example is Nordic’s nRF52840 multiprotocol System-on-Chip (SoC) built around an ARM 32-bit Cortex-M4F microprocessor with 1MB Flash and 256kB RAM. The chip supports Bluetooth 5 and ANT, in addition to configurable, proprietary 2.4GHz operation. Additionally, the nRF52840 includes an IEEE 802.15.4 PHY to support any protocol based on the standard.