Introduction of ZigBee
ZigBee is a Personal Area Network task group with low rate task group 4. It is a technology of home networking. ZigBee is a technological standard created for controlling and sensing the network. As we know that ZigBee is the Personal Area network of task group 4 so it is based on IEEE 802.15.4 and is created by Zigbee Alliance.
ZigBee is a standard that addresses the need for very low-cost implementation of Low power devices with Low data rates for short-range wireless communications.
Why another short-range communication standard??
Types of ZigBee Devices:
- Zigbee Coordinator Device: It communicates with routers. This device is used for connecting the devices.
- Zigbee Router: It is used for passing the data between devices.
- Zigbee End Device: It is the device that is going to be controlled.
General Characteristics of Zigbee Standard:
- Low Power Consumption
- Low Data Rate (20- 250 kbps)
- Short-Range (75-100 meters)
- Network Join Time (~ 30 msec)
- Support Small and Large Networks (up to 65000 devices (Theory); 240 devices (Practically))
- Low Cost of Products and Cheap Implementation (Open Source Protocol)
- Extremely low duty cycle.
- 3 frequency bands with 27 channels.
Operating Frequency Bands (Only one channel will be selected for use in a network):
- Channel 0: 868 MHz (Europe)
- Channel 1-10: 915 MHz (the US and Australia)
- Channel 11-26: 2.4 GHz (Across the World)
Zigbee Network Topologies:
- Star Topology (ZigBee Smart Energy): Consists of a coordinator and several end devices, end devices communicate only with the coordinator.
- Mesh Topology (Self Healing Process): Mesh topology consists of one coordinator, several routers, and end devices.
- Tree Topology: In this topology, the network consists of a central node which is a coordinator, several routers, and end devices. the function of the router is to extend the network coverage.
Architecture of Zigbee:
Zigbee architecture is a combination of 6 layers.
- Application Layer
- Application Interface Layer
- Security Layer
- Network Layer
- Medium Access Control Layer
- Physical Layer
- Physical layer: The lowest two layers i.e the physical and the MAC (Medium Access Control) Layer are defined by the IEEE 802.15.4 specifications. The Physical layer is closest to the hardware and directly controls and communicates with the Zigbee radio. The physical layer translates the data packets in the over-the-air bits for transmission and vice-versa during the reception.
- Medium Access Control layer (MAC layer): The layer is responsible for the interface between the physical and network layer. The MAC layer is also responsible for providing PAN ID and also network discovery through beacon requests.
- Network layer: This layer acts as an interface between the MAC layer and the application layer. It is responsible for mesh networking.
- Application layer: The application layer in the Zigbee stack is the highest protocol layer and it consists of the application support sub-layer and Zigbee device object. It contains manufacturer-defined applications.
- Contention Based Method (Carrier-Sense Multiple Access With Collision Avoidance Mechanism)
- Contention Free Method (Coordinator dedicates a specific time slot to each device (Guaranteed Time Slot (GTS)))
- Home Automation
- Medical Data Collection
- Industrial Control Systems
- meter reading system
- light control system