ZigBee

ZigBee is a low-power, low-data, short range wireless communication technology and an international standard protocol for the next generation wireless network. ZigBee's reduced data size helps in building large network with low cost. ZigBee uses the PHY and MAC layers defined by IEEE 802.15.4 that is a global standard for low power, short range wireless networks.

Low Power

A variety of markets has been included such as industrial monitoring and automation etc because of it's simple, cost-effective and low-power wireless connectivity. The building blocks of a ZigBee-compliant platform are RF transceiver, MAC and ZigBee software, Microcontrollers and Sensors etc.

Robust

ZigBee robust foundation is provided by 802.15.4. This ensures a reliable solution for noisy environments. Energy detection, clear channel assessment and channel selection are the features that help the device to pick the best possible channel. Network and data security is ensured by multiple levels of security. The data delivered to it's destination is ensured by Message acknowledgement.

Mesh Networking

ZigBee is differentiated from other networks by it's ability to cover large areas with routers. The network is extended by Mesh topology and reliability of the network is increased by self healing. This is done by re-routing a message in case of node failure.

Interoperability

Testing and certification programs of the ZigBee Alliance ensures interoperability between vendors. Users can be assured the devices that go through certification testing and use the ZigBee logo will work with other devices based on the same applications. This provides end customers peace of mind while creating the ZigBee logo products.

Need for ZigBee

There are multitude of standards like Bluetooth and Wi-Fi that address mid to high data rates for Voice, PC LANs, Video,etc. However, up till now there hasn't been a wireless network standard that meets the unique needs of sensors and control devices. Sensors and controls don't need high bandwidth but they do need low latency and very low energy consumption for long battery lives and for large device arrays. The ZigBee Alliance is not pushing a technology; rather it is providing a standardized base set of solutions for sensor and control systems.

Advantages

  Reliable
  Mesh networking
  Low data-rate applications
  Very long battery life
  Secure
  Scalable
  Low cost
  Low Power

Applications

  TV, VCR, DVD/CD remote
  Mouse / Keyboard / Joystick
  Security, lighting control and access control
  Asset management, Energy management
  Patient monitoring, Fitness monitoring
  Building automation
  Wireless sensor applications
  Global applicability

IEEE 802.15.4

ZigBee comprises two standards

1. IEEE 802.15.4, for the physical layer(PHY) and media-access-control (MAC) layers.
2. ZigBee standard for networking, security and application layers.

IEEE 802.15.4 is one of the ZigBee standard. So any ZigBee application is an 802.15.4 application.

The IEEE standard 802.15.4 was created for low rate, wireless personal area network. WPAN is a low-cost, very low power consumption, network flexibility standard. It consists of two basic devices.

  Full-function device
  Reduced-function device

A Full-function device can act as a Coordinator and a Router.
A Reduced-function device is always an End-device.

IEEE 802.15.4 PHY Layer

This layer specifies how 802.15.4 devices communicate with each other over the wireless channel. The use of three frequency bands with varying data rates is allowed. The bit rates are 20 Kb/s in the European 868 MHz band, 40 Kb/s in the North American 915 MHz band, and 250Kb/s in the worldwide 2.45 GHz band.

Activation and deactivation of the transceiver, channel frequency selection and data transmission/reception is done by this layer.

IEEE 802.15.4 MAC Layer

This layer specifies, when the communication channel is accessed by the devices. Beacon generation and synchronization, supporting PAN association and disassociation, supporting optional device security, managing channel access via CSMA-CA are the services provided here.

The emphasis is on very low cost communication of nearby devices with little to no underlying infrastructure, intending to exploit this to lower power consumption even more.