What is Zigbee? – Overview
Do you want to adopt a flexible network structure with very long battery life and is easy to install?
To answer this, we have a question: what is Zigbee? Zigbee is a wireless technology standard defining a set of communications protocols for limited range communications.
Zigbee is low in cost, less in power IoT networks. Zigbee works on IEEE 802.15.4 physical radio specification along with unlicensed bands.
Why Do We Need Zigbee Technology?
If we already have communication standards like Wifi and Bluetooth then why do we need another short-range communication standard? Well, the Zigbee standard is for control and sensor networks.
The objective is to monitor and control devices as Wi-Fi and Bluetooth are not suitable for this specific wireless communication.
So, what is Zigbee addressing in its standard? 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.
It is one of the most commonly used standards for the Internet of Things (IoT).
Zigbee is an open-source standard that was developed by Zigbee Alliance which is an organization created in 2002, now including 100s of companies as its users.
Applications of Zigbee Technology
1. Home Automation:
In Zigbee Home Automation, a home automation controller with a software application that controls devices.
The controller is also called a central hub or simply a hub. The gateway is the interface between the Zigbee network and the web.
The gateway connects to the internet that lets the house owner control smart home devices from anywhere in the world. Some of the smart home devices the Zigbee includes are:
- Door locks
- Smoke detectors etc.
Now in the figure, switches are not connected to any electrical wire because they are battery operated. Switching on and off the plugs will deliver a note to the controller whether the appropriate device is to turn off or on.
2. Medical Data Collection:
Another interesting Application of the Zigbee network is the Remote Monitoring System. Here a patient can be wearing some Zigbee sensors collecting information such as blood pressure, heart rate, body temperature, etc.
This information will be sent through the Zigbee gateway over the internet to the personal computer in the hospital so that a physician or a nurse can monitor the patient’s health.
You might have a question, why can’t we just use Wi-Fi or Bluetooth technology for these devices? WiFi uses a lot of power for battery-powered devices or devices where low power consumption is required e.g. sensors.
Devices in Zigbee use a low data rate which is the opposite in the case of Wi-Fi. So it is overkill to use Wi-Fi in this application.
Bluetooth will also be a bad fit because the Bluetooth network can only support a maximum of 7 devices, while Zigbee supports 100 devices.
3. Industrial Control Systems:
Industries use Zigbee technology as devices can be connected to the router with fewer data costs and less power consumption. Moreover, it collects every information required and performs control tasks inside a building.
General Characteristics of Zigbee Standard:
- Low Power Consumption: Zigbee devices can typically operate for several years on a single battery. In Zigbee applications, the devices spend their time in a saving power mode also known as sleep mode.
- Low Data Rate: It varies between 20kbps-250 kbps, whereas Wi-Fi will result in 11 Mbps and Bluetooth in 1 Mbps. Zigbee can transfer a lot of data.
- Short Range: Zigbee network ranges up to 75-100 meters indoors and outdoors up to 300+ meters (line of sight).
- Network Join Time: It takes about 30 msec to join a network, whereas Wi-Fi will take 3 seconds and Bluetooth up to 10 seconds.
- Support small and large networks: Zigbee networks vary from several devices to 1000 devices. Zigbee can support up to 65000 devices in a single network as per theory, but practically 240 devices are supported compared to this Wi-Fi can support 32 and Bluetooth only seven devices.
- Low Cost of Products and Cheap Implementation: The reason for this is the simplicity of the technology. Zigbee Standard is less complex than Wi-Fi or Bluetooth Standard, as it is an open-source protocol that makes it cheaper for the manufacturer because they don’t have to pay any license fee or royalty.
- Security: Zigbee uses AES cryptographic algorithm for data encryption and data authentication. It is a standard that banks are using for their online operations. It is in Government agencies with one of the secure cryptographic algorithms.
- Operating Frequency Bands: There are three frequency bands currently assigned to Zigbee.
- 868 MHz – It includes only one channel. This band is in Europe.
- 915 MHz – It includes ten channels that are in the US and Australia.
- 4 GHz – It includes 26 channels and is available across the world.
Types of Zigbee Devices and Networks:
1. Coordinator – Zigbee Coordinator is the most capable device. It is the device that starts the network. It is the root of the network as there is one coordinator in each network. The coordinator performs the many tasks:
- Channel selection – Before the coordinator starts, it automatically performs the channel scan to select it, with less interference.
- Assign an ID to the Network – It allocates the unique address to each device in the network. So anytime the device joins, the network coordinator assigns the address to it. The coordinator also initiates and transfers messages in the network.
2. Routers – Zigbee routers act as initial nodes between the coordinator and the end devices.
This causes route traffic between different nodes. They also receive and store messages intended for their children. Routers allow other routers and end devices to join the network.
3. End Device – Zigbee end device contains just enough information to talk to the parent node.
They may sleep (a standby), which makes end devices suitable choices for battery-operated devices. All traffic to an end device moves to its parent. The end device requests its parent for any pending messages.
Zigbee Network Topologies
What is ZIgbee? – Zigbee Network Topologies
1. Star Topology
- It is the simplest and the least expensive implementation.
- There are no routers in this architecture.
- The end device can not communicate directly with another end device.
2. Mesh Topology
- Every node connects with the neighboring node(except for the end devices)
- A message hops from one device to another to reach its destination.
- If a node fails, data can be re-routed using another path.
3. Tree Topology
- It’s not very different from mesh configuration as it’s not connected to neighboring nodes.
- Routers are not interconnected.
The coordinator assigns only one channel to the network as all devices will have to share this single channel to communicate. There are two methods for channel access:
- Contention based method
- Contention free method
1. Contention Based Method
- Devices do not need to be synchronized.
- Carrier Sense Multiple Access- Collision Avoidance mechanism used by all devices to access the channel.
- In CSMA anytime a device wants to transmit:
- It first goes into receive mode.
- Detect if there is any signal in the channel
- The device will only transmit the data if the channel is clear. However, if it is not clear, the device backs off for a random period and tries again.
2. Contention Free Method
- The coordinator dedicates a specific time slot to each device. It is called a guaranteed time slot(GTS).
- There is a beacon used to synchronize the clocks of all devices in the network.
Step 1: Be sure to have a hub.
Step 2: Select devices. Consider room size. While using Zigbee, the device should be in 10-20 meters. If devices are not that close together, you should have the Zigbee range.
It uses a range of extender devices that act as a router in a Zigbee mesh network.
If your rooms are spacious, you’ll wish for home technology with a longer direct range, like Z-Wave.
Step 3: Setup the hub.
Step 4: Plugin and connect devices.
Zigbee is the best, powerful, and cost-friendly home technology. Zigbee is low-power and only uses data when required. It has many advantages over Bluetooth.
It consumes less energy than Wi-Fi, resulting in the best battery life.