In contrast to the upcoming new technologies that aims for high speed data transfers, Zigbee technology provides a stable, high efficient networking using low data transfer rates when the information and communication of the devices are less. The aim of this article is to provide information about Zigbee technology, its architecture, network topologies, applications, advantages and disadvantages.
What is Zigbee in IoT
This technology is built on IEEE standard specification for Wireless Personal Area Networks (WPANs). It is an open standard, packet based protocol used for more reliable, low power wireless networks. They are designed to operate at 868MHz, 902-928 MHz and 2.4 GHz frequencies that require a low data transfer rate of 250 Kb/sec across 16 different channels.
Fig. 1 – Introduction to Zigbee Technology
The range of Zigbee is between 10 meters and 100 meters. Its wireless networking is simpler to design, less expensive, highly stable and offers more secure networking. The discovery of Zigbee protocol has successfully eliminated the risk of single point signal failures.
Wireless communication is established when Zigbee devices are integrated into systems across IoT (Internet of things) industry via Zigbee getaways.
Fig. 2 – Zigbee Module and Devices
Architecture of Zigbee
- Foundation Layers
- Application and Interface Section
This Layer is defined by IEEE 802.15.4 standard. Both Physical layer and Medium Access Control (MAC) layers act as foundation layers for this technology.
The physical and electrical characteristics are defined by the physical layer. Whereas, Medium Access Control (MAC) layer provides interface between the physical and network layers.
Fig. 3 – Zigbee Architecture (Stack)
Application and Interface Section
This section is defined by Zigbee Specifications and contains Network Layer and Application Layer.
Network Layer provides interface between MAC layer and the application layer. It is responsible for routing and establishing different network topologies namely Star, Mesh and Tree topology. Initiation of a network, assigning node addresses, configuring of new devices, providing secured transmission is the responsibility of the network layer.
The Application Layer consists of sub layers namely Application Support Sub Layer and Application Framework.
Application Support Sub Layer (APS) is responsible for filtering of packets for end devices, checks for duplicity of packets which is common in a network that supports automatic retries.
The Application Framework represents how end points are implemented, how data requests and data confirmation is executed for that particular vendor.
Zigbee Network Nodes
Zigbee’s system structure consists of three different devices or nodes within a single network. They are:
- End Devices
Fig. 4 – Network Node Types
Zigbee Coordinator is responsible to establish a centralized network. A coordinator resembles a router with added functionality like selecting an appropriate channel after scanning for available channels and selecting extended PAN-ID.
The routing services to network devices are provided by Zigbee router. The router is expected to remain in “ON” state unlike sleeping end devices which remains in “OFF” state when idle.
On behalf of sleeping end devices , the coordinator or a router is designated as ‘primary discovery cache device’ which provides server related services like uploading, storing the information and responds to requests.
End devices are leaf nodes which communicate only through their parent nodes. End devices are categorized into two types based on their network stack. They are:
- Sleepy End Devices
- Non-Sleepy Devices
Sleepy End Devices
When the device is in idle state, it turns off the radio which helps in conserving the resources.
The devices are in “ON” state even when they are idle. The standard Zigbee devices are of this type.
Zigbee Network Topologies
This technology supports Star, Tree and Mesh topologies.
Fig. 5 – Zigbee Network Topologies
This type of topology consists of a coordinator and several nodes or end devices. The node communicates with only one coordinator for the communication.
Any data packet exchange between the nodes must go through the coordinator and there is no alternate path from source to destination and hence it may become bottle necked.
This type of topology consists of a central node which is a coordinator, routers and end devices. The routers expand the network coverage.
The end nodes connected to the routers or the coordinators are called its children. The end device always communicates with its parent who is the router or coordinator.
Mesh topology is also known as peer to peer network or a multihop network. In this topology the data packets pass through multiple hops to reach their destination which suggests that if the data path fails then the node finds an alternate path to reach its destination.
This network requires less power to operate when the devices are placed closed to each other. This type of network consists of one coordinator, several routers and end devices. Adding more devices to the network increases the range of a network.
Applications of Zigbee Technology
The applications of this technology includes: –
1. Collection of Medical Data
This technology is used in home patient monitoring where collection of medical data is crucial. In this system, a patient wears a Zigbee device which collects the information like the pulse rate, temperature of the body, blood pressure etc.
2. Intelligent Smoke Alarms
This technology is used in intelligent smoke alarms. This system consists of a smoke detection module, a wireless communication module, data collection module and an intelligent identification module which differentiates the types of smokes i.e. smoke arising from cooking, from accidental fire, foggy air etc. thus improving the safety of the user.
Fig. 6 – Applications of Zigbee Technology
3. Home Automation System
This technology is used in home automation system leading to create smarter homes that has enhanced the comfort, convenience, security of the users. Smart Air conditioners, smart TV’s, smart refrigerator, smart home alarms can be made inter operable using this technology.
4. Wireless Sensor Networks
An intelligent smart wireless sensor network system helps to gather information and to monitor air quality, weather conditions, traffic etc.
Advantages of Zigbee Technology
The advantages of this technology include:
- It is more stable and reliable.
- It is less complex than Bluetooth.
- Installation is easy and consumes less power.
- Its protocol patent is free and hence cost effective.
- Easier to control and monitor home devices with a touch of a button.
Disadvantages of Zigbee Technology
The disadvantages of this technology include:
- It operates on short range i.e. 10-100 meters line of sight.
- Low transmission rate.
- It has certain limitations in the area of memory size, processing speed of data.
- Less secure compared to Wi-Fi based security systems.