Qorvo, provider of RF solutions, announced on Wednesday that it has been awarded certification for the multi-sensor and generic switch features of Zigbee Green Power v1.1. These new features expand the types of smart home sensors that can be powered by energy harvesting, eliminating the need for batteries or enabling ultra-long battery life.
The multi-sensor extension to the Green Power specification significantly compresses data to reduce the length of Green Power communication frames. These ultra-short, ultra-dense data packets result in longer battery life and enable support for multiple types of smart home sensors in a single device. For example, the multi-sensor feature measures temperature, humidity, light levels and air quality in a single indoor device. The extension adds support for ultra-low power door and window sensors, motion sensors and leakage detectors.
Functions can be assigned to the various switches on a device during commissioning – in a user-friendly way – by using the generic switch extension. This enhances flexibility for the end customer and reduces the volume of part numbers (SKUs) for the product manufacturer.
Qorvo has supported the Zigbee Green Power feature since its inception and was one of the first Zigbee Alliance members to achieve Golden Unit status. The company continues to be a strong supporter of the new Zigbee Green Power feature set. Qorvo’s Wireless Connectivity business is a developer of wireless semiconductor system solutions for connected devices and Wi-Fi integrated front-end solutions, including advanced filtering. It offers a range of advanced Radio Frequency products, filters, and software for smart home data communications and the IoT.
Zigbee Green Power is one of the features of Zigbee 3.0 that sets this protocol apart from other smart home standards. From its inception, Green Power has been focused on reducing energy consumption to enable the ultra-long battery life or energy harvesting applications it is targeting. As a result, it has made some different tradeoffs when compared to traditional Zigbee 3.0 battery powered end nodes.
Green Power devices and traditional Zigbee 3.0 end nodes use the exact same PHY and MAC (IEEE 802.15.4), which give both devices the exact same nJ/bit figure for exchanging data. When compared to the Zigbee 3.0 end nodes, Green Power further reduces energy consumption by decreasing the number of bits that the Green Power protocol requires to have exchanged over the air. This is achieved by optimizing the sizes of the packets a Green Power node needs to send, and by reducing the number of packets it sends for a given task.
Green Power has always placed strong focus on keeping packet sizes as small as possible where Zigbee end devices rely on 64-bit MAC addresses, Green Power has introduced 32-bit Source ID to uniquely identify the devices. Green Power uses some cross-layer optimizations to avoid overhead in the packet structure. For example, it allows combining reports from different clusters inside a single packet, saving the overhead associated with having to use separate packets.
Green Power splits the functionality over the Green Power devices and the backbone nodes very asymmetrically. Green Power devices are kept as simple as possible, while the intelligence needed for routing is offloaded to the backbone network (the Zigbee 3.0 router devices). This also allows Green Power devices to save on the size of the packet headers required.
With the introduction of the new multi-sensor feature, Green Power optimizes the application level payload by exploiting the pre-knowledge of the type of reports a given sensor can send over its lifetime. Instead of indicating the meta-information with respect to data type and data format in every report sent, the multi-sensor feature provides this meta-information once during commissioning, and the reports only carry the actual measurement values. These are typically devices that combine multiple sensors, like temperature and humidity, hence the feature was named “Green Power Multi-Sensor.”
Zigbee 3.0 end nodes count on a MAC level (single hop) and APS level (end-to-end) acknowledgement mechanism to trigger retries and ensure reliability. Retries can be triggered at different layers, resulting in the very high reliability numbers for which Zigbee 3.0 is known.
In an energy-harvesting context, there is, however, no guarantee that the Green Power device will have enough energy available to perform such retries. As such, Green Power takes a different approach. To maximize reliability with a limited energy budget, Green Power leverages the powered Zigbee 3.0 backbone network, and increases the probability that the Green Power frame is received, by having Zigbee routers act as potential proxies. Although this does not enable the same reliability levels achieved by Zigbee 3.0 end devices, it is by far good enough for the large majority of sensor use cases.
Green Power devices are kept as simple as possible. They use an asymmetric approach that allows them to deal only with the application-level aspects – and, to a lesser degree, some commissioning aspects – while other networking and support-related aspects, like routing and binding, are offloaded to the Zigbee backbone network.
This enables Green Power devices to be implemented on platforms with less real estate, allowing smaller and less costly solutions. Where Zigbee 3.0 end nodes are typically equipped with at least 256 KB program memory and 16 KB data memory, the 32 KB program memory and 1 KB data memory of a Green Power device is often sufficient.
“There are hundreds of millions of smart home devices worldwide and Zigbee has the largest market share1,” said Mareca Hatler, ON World’s research director. “Creating battery-free systems is a growing trend, and Zigbee Green Power is the solution for developers to create interoperable Zigbee products that are powered with energy harvesting.”
Cees Links, general manager of Qorvo’s Wireless Connectivity business unit, said, “By offering the first multi-sensor and generic switch features to be certified under the Zigbee Green Power v1.1 specification, Qorvo is first to create new opportunities for smart home sensors that eliminate batteries or substantially increase their longevity. These features are essential to making the fully-networked smart home a practical reality.”