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FAQs: Zigbee

Posted: 13 Oct 2008 ?? ?Print Version ?Bookmark and Share

Keywords:FAQ? Zigbee?

What is Zigbee?
Zigbee is a standard for embedded application software and has been ratified in late 2004 under IEEE 802.15.4 Wireless Networking Standards.

Zigbee is an established set of specifications for wireless personal area networking (WPAN), i.e., lighting control among related devices. This kind of network eliminates use of physical data buses like USB and Ethernet cables. The devices could include telephones, hand-held digital assistants, sensors and controls located within a few meters of each other.

Zigbee is one of the global standards of communication protocol formulated by the relevant task force under the IEEE 802.15 working group

How Zigbee came into existence?
The Zigbee Alliance has been set up as "an association of companies working together to enable reliable, cost-effective, low-power, wirelessly networked, monitoring and control products based on an open global standard". For the first time, companies will have a standards-based wireless platform optimized for the unique needs of remote monitoring and control applications, including simplicity, reliability, low-cost and low-power".

Where Zigbee can be used?
The goal is "to provide the consumer with ultimate flexibility, mobility, and ease of use by building wireless intelligence and capabilities into every day devices. Zigbee technology will be embedded in a wide range of products and applications across consumer, commercial, industrial and government markets worldwide. Presently this includes broadly the Home Automation, Building Automation, Consumer Electronics, Personal Health Care and Industrial Automation categories.

Some of the direct applications are:

  • Security

  • HVAC

  • Lighting Control

  • Access Control

  • PC & Peripherals

  • Remote controls for TV/DVD

    What can Zigbee network contain?

    The target networks encompass a wide range of devices with low data rates in the Industrial, Scientific and Medical (ISM) radio bands, with building-automation controls like intruder/fire alarms, thermostats and remote (wireless) switches, video/audio remote controls likely to be the most popular applications.

    So far sensor and control devices have been marketed as proprietary items for want of a standard. With acceptance and implementation of Zigbee, interoperability will be enabled in multi-purpose, self-organizing mesh networks.

    What are the features of Zigbee?

  • Has low power consumption with battery life ranging from months to years. (Operates in discontinuous Tx/Rx mode or sleep mode)

  • Maximum data rates allowed for each of these frequency bands are fixed as 250 kbps @2.4 GHz, 40 kbps @ 915 MHz, and 20 kbps @868 MHz.

  • High throughput and low latency for low duty-cycle applications (
  • Channel access using Carrier Sense Multiple Access with Collision Avoidance (CSMA-CA)

  • Addressing space of up to 64-bit IEEE address devices, 65,535 nodes per network and support typical range of 50 M.

  • Fully reliable "hand-shake" data transfer protocol.

  • Supports network topologies like star, peer-to-peer, mesh and cluster tree

    What are the layers in Zigbee?

    The Zigbee Standard has evolved standardized sets of solutions, called 'layers'. These layers facilitate the features that make Zigbee very attractive: low cost, easy implementation, reliable data transfer, short-range operations, very low power consumption and adequate security features. The layers are:

  • Application Support layer

  • Network Layer

  • Media access control (MAC) layer

  • Physical (PHY) layer

    What are the device types in the Zigbee network?

    There are three different Zigbee device types that operate in any self-organizing application network.

  • Coordinator

  • Router

  • End Device( either full function FFD or reduced function RFD devices)

    What are the frame structures supported by Zigbee?

    The four frame structures are:

  • Beacon frame for transmission of beacons

  • Data frame for all data transfers

  • Acknowledgement frame for successful frame receipt confirmations

  • MAC command frame

    What are advantage of cluster / mesh network over star networks?

    The cluster and mesh network are also known as a multi-hop network, due to their abilities to route packets between multiple networks, while the star network is called a single-hop network. The mesh network allows the designer the extended the physical range of the network, and to provide adequate redundancy.

    What is CSMACA Technology?

    CSMACA is Carrier sense multiple access collision avoidance, CSMA/CA is a modification of pure CSMA. Collision avoidance is used to improve the performance of CSMA by attempting to be less "greedy" on the channel. If the channel is sensed busy before transmission then the transmission is deferred for a "random" backl-off interval. This reduces the probability of collisions on the channel.

    What is CSMACD Technology?

    CSMACD is Carrier sense multiple access collision detection, is a network control protocol in which a carrier sensing scheme is used.

    a transmitting data station that detects another signal while transmitting a frame, stops transmitting that frame, transmits a jam signal, and then waits for a random time interval (known as "backoff delay" and determined using the truncated binary exponential backoff algorithm) before trying to send that frame again.

    Collision detection is used to improve CSMA performance by terminating transmission as soon as a collision is detected, and reducing the probability of a second collision on retry, also methods for collision detection are media dependent.

    - Source: Microchip Technology Inc.

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