25 Jan 2016

Moving to Zigbee IPv6

Josh Mickolio, Product Manager-RF, Digi-Key looks at the migration of Zigbee to IPv6 and some of the relating advantages.

With the prospect of billions of sensors and devices being connected up to the Internet, the world has been running out of numbers. These numbers are the old IPv4 addresses that currently allow devices to connect to the Internet, but for the Internet of things, a new scheme has been introduced.

IPv6 extends the address space to allow individual sensors and nodes to be connected directly to the Internet, but this is also requiring significant changes to wireless networks that previously used gateway to control access to the nodes.

Zigbee basics

Zigbee is one of the most common of these wireless network protocols, and after several years of discussion, a version of the Zigbee mesh networking standard that supports the new IPv6 Internet protocol has been launched. This has required significant changes to software in the network layer, including more security for the nodes.

ZigBee IP is the first open standard for an IPv6-based full wireless mesh networking solution and provides seamless Internet connections to control low-power, low-cost devices, driving the Internet of Things (IoT), particularly in home automation and smart grid applications.

The mesh capability is an important part of the Zigbee standard as it allows nodes to connect to each other to extend the network rather than work through a single point such as an access point, although a gateway device is needed to connect to other networks. This makes Zigbee easy to extend which is a strong advantage for IoT and machine to machine (M2M) applications. The key change is that, unlike Zigbee today, Zigbee IP networks do not necessarily need gateway devices to connect to the Internet and so other devices can also potentially access the nodes.

The new standard connects dozens of the different devices into a single control network and is designed to support the forthcoming revision of ZigBee Smart Energy (version 2.0) that takes Zigbee into other frequency bands, not just the unlicensed 2.4GHz band. This supports smart power grid, power and water utility and M2M applications, opening up a tremendous opportunity for chip and system developers.

Zigbee spcification

The ZigBee IP specification adds network and security layers and an application framework to the existing IEEE 802.15.4 standard to provide a more scalable architecture with end-to-end IPv6 networking, laying the foundation for an Internet of Things without the need for intermediate gateways. It uses existing standard Internet protocols such as 6LoWPAN, PANA, RPL, TCP, TLS and UDP with proven, end-to-end security using 128bit AES encryption and public key infrastructure.

Another significant change is that alongside global operation in the 2.4GHz frequency band according to IEEE 802.15.4, it also supports regional operation in the 915MHz band for the Americas, 868MHz in Europe and 920MHz in Japan. The raw data throughput rates of 250Kbs can be achieved at 2.4GHz with 16 channels, just the same as today’s Zigbee networks, but 40Kbs is possible at 915MHz through 10 channels and 20Kbs at 868MHz on 1 channel, although it is important this is halved for each hop through a neighbouring node if using the mesh capability. Transmission distances range from 50 to 200 meters, depending on power output and environmental characteristics. Coupled with the lower power requirements, this makes Zigbee IP well suited for sensor data and control applications with low data rates.

Because there is no need for a gateway on the network, the new Zigbee IP protocol has to support more complex discovery mechanisms such as full application confirmation. Devices can now be added anywhere in the network, and paired with devices perhaps on other networks, so the discovery, authentication and pairing layers are significantly more complex and need this full application confirmation which previously was handled in the gateway.

Multiple star topologies

The new standard also supports multiple star topologies and inter-personal area network (PAN) communication as again the Zigbee networks can be set up in many more ways. This means support for both unicast and multi-cast transmission options is also needed.

The good news is that there is a new generation of silicon being delivered that makes use of more advanced process technologies to deliver more performance with more integration (such as AES encryption engines) with lower power. This will enable the next generation of Zigbee IP systems.

The ZigBee IP networks are composed of several device types: ZigBee IP Coordinator, ZigBee IP Routers and ZigBee IP Hosts. Coordinators control the formation and security of networks. Routers extend the range of networks. Hosts perform specific sensing or control functions. Manufacturers often create devices that perform multiple functions, for example a programmable communicating thermostat may also route messages to the rest of the network.

Figure 1 illustrates an example ZigBee IP topology that includes one coordinator, a border router for Internet control access, five routing devices and, two end devices creating a control network. An example network in a smart home, the coordinator may be a programmable communicating thermostat with advanced support for an in-home display. Devices such as smart plugs, thermostats and smart appliances could be configured as routing devices. Simple devices such as smart appliances and temperature sensors could be end devices.

Example ZigBee IP topology

Figure 1: An example ZigBee IP topology

The ZigBee IP specification is built with a layered architecture, and is therefore suitable for any link layer within the 802.15.4 family. ZigBee IP incorporates technologies, such as 6LoWPAN and RPL, that optimize meshing and routing for wireless sensor networks. This blend of technologies results in a solution that is well suited to extend IP networks to IEEE 802.15.4-based MAC/PHY technologies.

Interference will be an increasingly important challenge with IPv6-based systems that are more spread out and working with other networks in the 2.4GHz band such as Bluetooth and WiFi. As a result ZigBee IP products have the ability to access to 16 separate, 5MHz channels in the 2.4GHz band so that band management can be used to avoid interference.

This can either be done manually when a device is added to the network, or, as is more likely, using adaptive software to monitor the quality of a link and hop to a new band if necessary. This also helps keep the power consumption down as higher power will not be needed in the link to overcome interference.

The move to Zigbee IP and IPv6 will open up the market for lower cost integrated devices, perhaps around cores such as Atmel’s AVR for client systems, as well as highly integrated single chip implementations for controllers and more sophisticated clients that can also manage parts of the network. This will require modification to the MAC, PHY and network layers of the devices and may well require spins of the silicon over the next 12 to 18 months. TI and Silicon Labs are currently supplying Golden Units for testing Zigbee IP systems for interoperability.

Conclusion

Simply moving to an IPv6 addressing scheme is just the start of the move to Zigbee IP. Expanding the scalability of Zigbee’s authorization process, coupled with increased security and additional network topologies, allows the devices to be easily added to the network and protected. While previously the gateway had protected the end device from attack, now that security can be implemented at the end point through a fully tested and robust framework.

Combined with the additional elements of Zigbee IP and the Smart Energy profile, the IPv6 infrastructure will provide a scalable, robust network that can be used to connect the billions of new devices that are set to be part of the Internet of Things over the next decade.

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About the author

Josh Mickolio, Wireless and RF Product Manager at Digi-Key Corporation, is focused on the wireless industry and its emerging markets. Working in this role for over 10 years has offered the opportunity to engage in an exciting technology sector while supporting the latest engineering developments in Bluetooth, Cellular, WLAN, Zigbee and discrete RF for connected devices and infrastructure design.

Digi-Key Corporation is a global, full-service provider of both prototype/design and production quantities of electronic components, offering more than three million products from over 650 quality name-brand manufacturers. With over 800,000 products in stock, an impressive selection of on-line resources, and the logistical advantage of more than 800,000 square feet of expandable distribution space, Digi-Key continues to move forward, affirming its commitment to stocking the broadest range of electronic components in the industry and providing the best service possible to its customers.

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