An introduction to Zigbee / IEEE 802.15.4 Wireless Network

Zigbee or 802.15.4 is a wireless network standard to create a wireless network using low cost, low power consumption & low data rate connectivity devices. It can beat your Wi-Fi networks hands down for certain applications like industrial automation, medical patient monitoring, etc due to its prominent features. Let us find out what they are, in this article.

What is Zigbee/ 802.15.4 Network?

Zigbee is a Wireless Networking standard like Wi-Fi. Zigbee even operates in the same unlicensed frequency spectrum of 2.4 Ghz like Wi-Fi, but the similarity ends there. Zigbee devices form self configuring, self healing wireless networks that use low cost devices (radios, clients) to achieve a limited throughput (250 Kbps). The low bandwidth might surprise you initially, but that is sufficient for many applications.

Zigbee is the name of the alliance formed by independent companies that have some interest in manufacturing inter-operable wireless sensors and radios that can work with Zigbee standard and 802.15.4 is the IEEE Standard for the same. While IEEE 802.15.4 defines the physical and MAC layers, Zigbee itself defines the network and application layers of this wireless network. It means that all Zigbee devices will work with each other, irrespective of the manufacturer.

Features of Zigbee/ 802.15.4 Network:

• Throughput: 250 Kbps at 2.4 Ghz with 16 Channels / 40 Kbps at 915 Mhz with 10 Channels
• Transmission distance: 100 meters (Can be lesser in indoor and higher in outdoor conditions)
• Frequency: Uses unlicensed bands, can work anywhere in the world without requiring special permissions
• System resources required: 4-32 Kb
• Battery life: Around 1000 Days, Low power design
• Scalability: Highly scalable network that can accommodate up to 64,000 nodes using a single coordinator
• Relationship with Wi-Fi: Zigbee Networks can interfere with Wi-Fi if both are operating in 2.4 Ghz and they are not designed to inter-operate natively
• Cost: Zigbee Routers and Sensors cost very less (compared to Wi-Fi) and hence are more suitable for bulk deployment
• Network Topology: Uses Mesh Topology, Star Topology and Peer-to-Peer Topology, and can work in any one of them
• Power: Battery powered, no need for running cables across the premises

Applications of Zigbee/ 802.15.4 Network:

Some applications suitable for Zigbee / 802.15.4 Wireless network include : Industrial automation, Energy automation, Access Control, Heart rate monitor, Home security, Environmental control, Lighting control, Meter reading, HVAC / Heating control, etc.

Components of Zigbee/ 802.15.4 Network:

Coordinator: There is one coordinator (generally) in a Zigbee network that stores the network configuration information, security keys and all other important information about the network. This is the control unit of the whole Zigbee network. But in large networks, multiple Coordinators can be linked together. The end points/ sensors can connect directly with the coordinator, if required.

Router: Since the range of the Coordinator is limited, Routers are used to extend the Zigbee networks.  They have a range of 100 meters each, and they are kept within the range of other nearby routers so that they can form a mesh network. They connect the end users with the coordinator.

End point / Sensor/ Client: This is the small sensor that can be connected with any device that needs to transmit / receive control messages through the wireless network. They can be connected to the router / coordinator to be able to communicate with other devices.

Advantages of the Mesh Network used in Zigbee Networks:

The routers that are used to extend the Zigbee networks can connect with each other (within a certain range) using a Mesh Network. In fact, each router is connected to at least two more routers in a properly planned Zigbee network. Since these devices are battery powered (low power) devices, they don’t need any cables to connect back to the coordinator.

Each router not only transmits and receives messages intended for the end clients/ end points connected to it but also relays the messages of the other routers connected to it.

The Mesh architecture not only avoids backbone cabling, but also provides a good degree of fault tolerance. Even if one access point is down, the messages could be routed through others. The Zigbee network is designed to work efficiently by automatically identifying the shortest route possible for relaying every message.

Even if there are some structural obstructions, clients connect to an alternate router in their range. The Zigbee networks are extremely scalable and support up to 64,000 nodes using a single coordinator. If required, high powered RF radios can be designed for specific applications.

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