Thread network for low-power nodes

January 12, 2016 | 13:15
The Thread network stack
The Thread network stack
According to one of the first press releases this year on the theme of ‘all things IoT’ Thread-Technology is likely to see increasing uptake this year. At the Consumer Electronics Show (CES) in Las Vegas the Thread Group were demonstrating a typical home automation network consisting of lamp modules and different sensors interacting via a radio protocol. The American semiconductor manufacturer Silicon Labs are a founding member of the Thread Group and produce SoCs and Software-stacks to implement the network into IoT products.

So, what exactly is Thread? It isn’t just use one single protocol but specifies a number of protocols used in an IoT protocol stack. To send individual bits of information it uses radio IEEE 802.15.4 (in the 2.4 GHz radio band with a 250 kbit/s data rate). The 802.15.4 spec was developed specifically for use with battery powered devices which only need to send short bursts of information sporadically. It uses much less energy than RF links such as WLAN and Bluetooth.

ZigBee communications are also based on the 802.15.4 link protocol layer. In contrast to the original ZigBee spec, Thread uses standards higher up in the Internet protocol stack such as IPv6 and UDP. The 802.15.4 link layer allows a maximum packet length of only 127 bytes but the size of the IPv6 packet is over 1000 bytes so some form of adaptation layer is necessary to perform the conversion. An intermediate layer (known as 6LoWPAN) solves the problem by fragmenting the IPv6 packets at the transmitter and reassembling them at the receiver. Use of the Internet protocol has the advantage of making it very easy to connect a node in a Thread radio network (where at least 250 nodes can be accommodated) to a ‘normal’ Internet (WLAN/Ethernet) connection. Thread successfully unites the two worlds of (home) automation; many industry watchers predict that in the long run, Thread will eventually supplant ZigBee and similar protocols.

Unlike ZigBee, Thread offers a rigorous product certification to ensure security and product interoperability. For more information visit the Thread group page.
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