ULP Wireless Update

Thread protocol extends smart home influence

Thread protocol extends smart home influence

As the connected home gathers pace, a dedicated open-standard communication protocol is required

As more home automation IoT devices come onto the market, effective and efficient interoperability has never been more important. Many of today’s commercial protocols are proprietary, meaning only devices from a single vendor will interoperate. Worse yet, proprietary protocol set-up is tricky, efficiency is compromised, and security isn’t as strong as it could be. And many proprietary systems connect to the Internet via a single point such as a home Wi-Fi router, which means the entire network is broken if the router goes down.


Open-standard communication protocols address the drawbacks of proprietary protocols. Established technology such as Bluetooth Low Energy and zigbee are popular, and now Thread is attracting a lot of attention among smart-home sensor makers.


Thread is emerging as a low-power, easy-to-use, secure solution for the smart home. It has the backing of Google following its acquisition of Nest, the company famous for its smart home thermostat, at the beginning of 2014. Since then Google has used Nest’s Thread protocol as the basis for its smart home connectivity offering.


Google then set up the Thread Group, which now includes companies such as Samsung, ARM, and Qualcomm, to develop and maintain Thread as an open-standard protocol for low power wireless home automation networks. The first Thread standard was released in July 2015 offering scalability and reliability combined with security features such as smartphone- grade authentication and AES encryption.


Combining WPANs and IPv6

Thread, like some of its smart home counterparts including zigbee and Wireless HART, is built on the IEEE 802.15.4 standard which helps underpin its low power consumption. The Institute of Electrical and Electronic Engineers (IEEE) has developed and maintained this physical layer (PHY) and media access control (MAC) standard since 2003. It is designed for low power, low data rate wireless personal area networks (WPANs), allowing for up to 250kbit/s data rates, but the rate can be lowered for reduced power consumption. Useable range is around 10m. A 6LoWPAN (IPv6 over low power WPAN) adaption layer bridges the gap between the IEEE 802.15.4 PHY and MAC (primarily designed for transmission of lightweight packets across the home network) and the Thread upper layers and application (which handle the larger packets and IP address headers of the IPv6 protocol).


By supporting Internet Protocol (IP), Thread devices can communicate with all other IP-addressable devices on the Internet of Things (IoT) without relying on an expensive and complex gateway. Instead, Thread networks employ relatively inexpensive ‘border routers’ in place of complex gateway devices to relay the short-range WPAN signals to the Internet proper. IP support also means Thread devices can take advantage of existing, proven security- and transport-protocols that already service other IPv6 devices.


Thread networks

A second key advantage of Thread is its mesh network support for up to 250 devices. Mesh networks can self-heal by re-routing packets when individual nodes go down - building in redundancy. A mesh topology also enables scalability – more nodes can easily be added, extending the network’s reach.


However, not all Thread devices are able to operate as mesh nodes. End devices (for example, the smart home’s thermostats) are only able to transmit data and check for messages via their parent router. Such sensors spend most of the time in sleep mode, and by limiting the network functionality and duty cycle of end devices, efficiency (and battery life) is improved.


Routers play the key role in Thread mesh networking by relaying traffic and facilitating the commission of new devices. New devices need authorization from the user via a smartphone or tablet for security, but such authorization only takes a few steps. The first device to join the network becomes the lead router and makes decisions within the network. Other devices can then join the network as either router eligible devices or end devices, with router eligible devices able to become routers if needed. Unlike end devices, routers are not designed to sleep so inevitably use more battery power. Border routers provide bridges between the Thread network and exterior networks (in most cases, the Internet). Border routers can be specific Thread gateway devices or other devices that can communicate via both Thread and other protocols, such as home Wi-Fi gateways that have built-in Thread functionality. If one border router in the network fails, then another can take over.


Thread in Products

Last year, home automation firm Nest released an open-source implementation of Thread, called OpenThread. The networking protocol is available on GitHub and is both operating system and platform agnostic with a radio abstraction layer supported on multiple platforms. The idea is to give more developers access to Thread technology to encourage them to incorporate the protocol into new products. However, companies must join the Thread Group to gain the intellectual property rights to the protocol. Products must also be approved by the group before they can be marketed as “Thread-certified”.


Thread is gaining momentum with wireless chip vendors. For example, Nordic Semiconductor, an established supplier of Bluetooth Low Energy, ANT+, and 2.4GHz proprietary solutions, has added IEEE 802.15.4 PHY and MAC support to its nRF52840 System-on-Chip (SoC). The SoC is also Thread certified. For developers wishing to use the nRF52840 SoC’s IEEE 802.15.4 capability for Thread devices, Nordic supplies a Software Development Kit (SDK), employing OpenThread, for product development.


Given Thread’s key advantages in the smart home space, and the possibility of relatively straightforward software upgrades of IEEE 802.15.4-based products to enable them to use the Thread protocol, initiatives like OpenThread promise to result in rapid Thread adoption. When this happens, home automation devices such as smart thermostats will truly become an integral part of the IoT.