ZigBee what is it, ZigBee vs Bluetooth

ZigBee is a wireless communications protocol, somewhat like Bluetooth, used for machine to machine (M2M) interconnection and control. It is a low power, wireless network, which allows devices to interconnect and pass commands back and forth. In this way, it allows wireless technology to extend beyond what we are currently experiencing, drawing us closer to the automated home.

 

 

 

While ZigBee and Bluetooth are both wireless network protocols operating in the same frequency range, they are neither cross-functional or competing with each other. The two protocols are different enough that they can’t network together. But since they are intended for different purposes, cross-communication functionality is not needed.

 

Bluetooth is primarily used as a way of connecting consumer electronics together for user convenience. To put that another way, it’s a way of eliminating the need for cables to connect our various electronic devices together. Whether used for computers, audio equipment or telephones, it is always used with consumer electronics. ZigBee is not intended for use with consumer electronics, but rather for use in equipment that is intended to be automated and operate largely without user input.

 

ZigBee is still a relatively new technology. Although it was first released in 2003 and has hundreds of members and adopters, it hasn’t gained the widespread recognition that Bluetooth has. Nevertheless, if anything brings about the wireless home, it will probably be ZigBee.

 

This technology can be found in use in such diverse applications such as wireless sensor networks, industrial control, home automation, alarm systems and building automation. The devices themselves are low power devices, with a designed-in battery life of a minimum of two years.

 

How ZigBee Works

ZigBee works over mesh networking, a decentralized networking system. These networks can take on a star, tree or mesh (net) format. The network operates on the industrial, scientific and medical radio bands. It is a digital communications protocol (avoiding analog), with low bandwidth.

 

A ZigBee network can include three different types of devices:

 

  • ZigBee Coordinator (ZC) – These are the most capable devices which form the root of the network and may connect to other networks. A ZC is required for each network, as this is the device that starts the network. It stores network information, including being the repository for security keys.

  • ZigBee Router (ZR) – Routers perform two functions in a ZigBee network. They perform the normal router function of connecting devices to the network. In addition, they can run applications on the network.

  • ZigBee End Device (ZED) – These are the individual devices attached to the network. They have no ability to pass on data from other devices. A ZED contains just enough functionality to talk to the network, specifically communicating with a Coordinator or Router. When not needing to communicate, they change over to a “sleep” mode to conserve batteries.


By minimizing the amount of time that the radio portion of the ZigBee device is operating, the devices are able to conserve power, giving them long life. Whereas BlueRay devices are usually rechargeable, ZigBee devices are not, rather depending upon the long life offered by minimal power consumption.

 

There are actually a wide variety of ZigBee protocols and control programs, based on a number of specific application profile specifications. These include such areas as ZigBee Home Automation, ZigBee Smart Energy, ZigBee Telecommunication Services and ZigBee health Care. Each of these specifications is written for a specific functional area, in order to prevent overlap and confusion.

 

Like Bluetooth, ZigBee requires that devices on the network be “discovered” by the router or controller. For this to happen, they must all speak the same application protocol. This allows several ZigBee networks to operate in the same or overlapping areas, without creating interference problems.

 

The amount of time that it takes ZigBee devices to “handshake” and join a network is much less than that of Bluetooth devices, helping to maintain the long battery life. Bluetooth devices typically take 3 seconds to join a network, while ZigBee devices need a mere 30 milliseconds. This reduces the amount of radio on time considerably, allowing the device to return to sleep mode.

 

 

Comparing ZigBee to Bluetooth

Since Bluetooth is much better known, ZigBee can be understood by a direct comparison of the technical specifications of the two.

 

Item

Bluetooth

ZigBee

Maximum network speed

1 Mbit/s

250 Kbit/s

Protocol stack size

120 kbyte

28 kbyte

Network range

1 or 100 m, depending upon radio class

70 m

Typical network join time

3 seconds

30 milliseconds

Modulation technique

Frequency Hopping Spread Spectrum (FHSS)

Direct Sequence Spread Spectrum (DSSS)

Battery

Intended for frequent charging

Not rechargeable – depends on long battery life (up to 10 years)


As you can see from these specifications, there is no way that ZigBee could be used for many Bluetooth applications, such as transmission of audio and video signals. The high data transfer requirements for those applications is totally incompatible with ZigBee’s maximum speed.

 

 

However, this low bandwidth, along with the long battery life, makes ZigBee ideal for smart home and industrial devices. The devices can be quickly and easily integrated into the network, allowing them to communicate with the Controller, transferring data and receiving operating commands for the ZigBee devices themselves.