Zigbee Protocol Stack

Zigbee Protocol Stack Using IEEE 802.15.4

Zigbee is a low-power, low-data-rate, wireless communication protocol designed for short-range, low-cost, and low-complexity IoT and automation applications. It is built upon the IEEE 802.15.4 standard, which defines the Physical (PHY) and Medium Access Control (MAC) layers.

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Overview of Zigbee and IEEE 802.15.4

• IEEE 802.15.4: Provides the foundation (physical and MAC layers) for Zigbee.

• Zigbee: Builds on top of IEEE 802.15.4 by adding the network and application layers, enabling mesh networking, security, and device discovery.

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Zigbee Protocol Stack Architecture

The Zigbee stack is organized into four major layers, aligned as follows:

+----------------------------+
|  Application Layer         |
+----------------------------+
|  Network Layer             |
+----------------------------+
|  MAC Layer (IEEE 802.15.4) |
+----------------------------+
|  PHY Layer (IEEE 802.15.4) |
+----------------------------+

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1. Physical Layer (PHY) – IEEE 802.15.4

• Function: Converts data into signals for wireless transmission and vice versa.

• Key Roles:

  • Modulation/demodulation

  • Frequency selection (typically 2.4 GHz ISM band)

  • Data rate: 250 kbps (at 2.4 GHz)

  • Channel selection

• Components:

  • Radio transceiver

  • Antenna

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2. Medium Access Control Layer (MAC) – IEEE 802.15.4

• Function: Controls access to the radio channel and provides reliable link communication.

• Key Features:

  • CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance)

  • Frame validation and acknowledgment

  • Beacon-enabled or non-beacon modes

  • Guaranteed Time Slots (GTS) for time-critical data

• MAC Frame Types:

  • Data frame

  • Acknowledgement frame

  • Beacon frame

  • Command frame

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3. Network Layer – Zigbee Specification

• Function: Handles routing, addressing, and device management in multi-hop (mesh, star, or tree) networks.

• Key Functions:

  • Addressing: 16-bit short or 64-bit extended addresses

  • Routing: AODV-based (Ad hoc On-demand Distance Vector)

  • Device Roles:

    • Coordinator: One per network, initializes and manages it

    • Router: Forwards data and extends range

    • End Device: Low-power node that communicates only with parent

  • Network Formation & Joining

  • Topology Management

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4. Application Layer – Zigbee Specification

This consists of two sublayers:

a) Application Support Sublayer (APS)

• Interface between the network layer and application objects.

• Handles:

  • Binding (logical association of devices)

  • Group addressing

  • Message routing between applications

b) Zigbee Device Objects (ZDO) & Application Objects

• ZDO: Manages device roles, security, network joining/leaving.

• Application Objects: Actual user-defined software running on the device (e.g., temperature control logic).

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Summary Table

Layer	Protocol/Standard	Function
Application	Zigbee	Device discovery, binding, profiles, and services
Network	Zigbee	Routing, addressing, topology management
MAC	IEEE 802.15.4	Access to physical medium, channel control, frame delivery
Physical (PHY)	IEEE 802.15.4	Modulation, demodulation, signal transmission

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Zigbee Topologies

• Star: All nodes connect to a central coordinator.

• Tree: Nodes form a hierarchy; routers relay data.

• Mesh: Devices can route data dynamically to each other, improving reliability and range.

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Use Cases of Zigbee

• Home automation (lights, smart locks, sensors)

• Industrial control systems

• Smart energy meters

• Healthcare monitoring

• Building automation

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