RFZigbee Mesh Network Tutorial: Basics and Features
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This tutorial covers the basics of Zigbee mesh networks, including their features, advantages, and disadvantages. It also provides links to other Zigbee tutorials for further learning.
Network Topologies: Star, Tree, and Mesh
Figure 1 illustrates the common network topology types: star, tree, and mesh.
The figure shows how Zigbee elements, such as the coordinator, router, and end devices, are connected in these different network topologies.
In a mesh network, each node typically relays or routes data until it reaches the destination node. This makes mesh networking a powerful solution for routing data. Each node cooperates with other nodes to achieve an equal distribution of data.
The advantages of mesh networking are:
- Extended Range: Data can hop from node to node, easily extending the network’s range.
- Easy Node Insertion: New nodes can be easily added to the network.
- Self-Healing: In case of node failure or lost connection, data can be routed through other healthy nodes.
Because Zigbee supports mesh topology between its devices, it has become a popular choice for wireless mesh networking systems, especially in low data rate and low-power applications.
Zigbee Mesh Network Basics
Figure 2 depicts a simple Zigbee mesh network consisting of a coordinator, routers, and end devices. All nodes can transmit and receive data, but they have specific roles:
- Coordinator: Only one coordinator is needed to form a Zigbee network. It stores all the critical information about the network, including encryption keys.
- Routers: These are intermediate nodes that relay data between devices.
- End Devices: These are of two types: reduced function devices (RFDs) and full function devices (FFDs). RFDs cannot relay data and communicate with their parent devices (routers/coordinator) for relaying. FFDs, on the other hand, can relay data. Zigbee mesh networks typically use FFDs.
Zigbee is an open standard, which allows for interoperability between devices from different vendors.
Features of Zigbee Mesh Network
The following table outlines the key features of Zigbee mesh networks:
| Specifications | Details |
|---|---|
| Zigbee Mesh Support | IEEE Standard 802.15.4-2003 defines PHY and MAC layers; upper layers are managed by the Zigbee Alliance. |
| Frequency of Operation | Supports 2.4 GHz, 900 MHz, and 868 MHz bands. |
| Data Rate | 250 Kbps, 40 Kbps, 20 Kbps in different bands. |
| Sleep Operation | Only end devices can sleep. Coordinators and routers must remain active to allow new end devices to join the network. |
| Coverage Range | Most devices have a range of about 3.2 Km or less for each hop during transmission. |
| Encryption/Security | Uses AES encryption. |
| Zigbee Frame Payload Size | 80 bytes. |
| Interoperability | Possible as it is an open standard. |
| Addressing | Supports two types: MAC addressing of size 64 bits and network addressing of size 16 bits. |
DigiMesh
Digi International has developed a proprietary mesh protocol based on Zigbee, known as “DigiMesh.” This network has advantages and disadvantages compared to standard Zigbee mesh networks. DigiMesh allows sleep functionality on all nodes, which saves battery power and extends battery life.
