Single-Radio Zigbee and Thread

Earlier this year we saw that Zigbee and Thread were collaborating to implement Zigbee profiles or “clusters,” which normally appear at the top of a Zigbee stack, over the Thread stack as well.

Strategically, this allows top-level Zigbee to handle IP-based data, since Thread includes 6LoWPAN, an IPv6 adaptation for running over 802.15.4, the radio protocol used by Zigbee. Much of the world operates with IP on layer 3; this allows Zigbee infrastructure to participate.

That’s at the top of the stack. Meanwhile, at the bottom, Greenpeak recently announced a single-radio implementation of Zigbee and Thread in their GP712. It can handle both flows with a single radio – or, alternatively, it can serve as a single-stack chip, usable for either stack with a single stocking unit. It needs a thin layer to mux/demux the traffic into the appropriate stack once it leaves the radio.

This got me thinking about how these two reconvergent stacks might play together in different devices. This is based on realizing that an Internet of Things (IoT) edge node is likely to implement only one of the two protocols. So a mixed device isn’t likely to serve there (except as a single-SKU chip that goes either way).

Greenpeak says they’re targeting infrastructure nodes – hubs, gateways, set-top boxes and the like – and those devices are indeed likely to be managing multiple traffic streams across multiple platforms. On the other hand, it’s unlikely that they’ll be working at the application layer (except perhaps for deep packet inspection).

It may be a failure of imagination on my part, but the only node I can picture that might realistically process multiple protocols and implement the application layer would be a server. I’d include a phone as a possible server, although phones typically don’t do 802.15.4.

The following figures illustrate the different configurations that I’ve derived from this mental wandering. Presumably, the GP712 could serve in any of them with appropriate configuration.