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Zigbee
 

Zigbee

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    Zigbee Zigbee Presentation Transcript

    • Presents Seminar on “ ZigBee” By K.Gireesh 63,First floor, 5th Main Road, CIT Nagar, Nandanam, Chennai-35. Tel: 044-65253457 Mobile: 98405 77448 Website: www.vetechnologies.org Email: [email_address]
    • What is ZIGBEE Emerging standardized protocol for Ultra Low Power Wireless Personal Area Networks (WPANs) ZigBee is an established set of specifications for wireless personal area networking (WPAN) i.e, digital radio connections between computers and related devices. ZigBee is targeted at radio-frequency (RF) applications which require a low data rate, long battery life, and secure networking.
    • ZigBee Technical Goals
      • 10 kbps to 115 kbps data throughput
      • 10 to 75 m coverage range
      • Up to 100 collocated networks
      • Up to 2 years of battery life on standard alkaline
      • batteries
    • The ZigBee Alliance is 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.
    •  
    • IEEE 802.15.4
      • Zigbee is set of high level communication protocols based upon the specification produced by 802.15.4 - standard for wireless personal area networks (WPANs )
    • WPANs
      • A personal area network ( PAN ) is a computer network used for communication among computer devices (including telephones and personal digital assistants) close to one person
      • A wireless PAN consists of a dynamic group of less than 255 devices that communicate within a range of about a 33-feet.
    •  
    • IEEE 802 Wireless Space
    • ZigBee Vs Bluetooth
      • Bluetooth targets medium data rate continuous duty
      • – 1 Mbps over the air, ~700 kbps best case data transfer
      • – File transfer, streaming telecom audio
      • – Point to multipoint networking
      • ZigBee targets low data rate, low duty cycle
      • – 250 kbps over the air, 60-115 kbps typical data transfer
      • – Long battery life (weeks to months)
      • – More sophisticated networking
    • ZigBee Vs Other Wireless Protocols
    • IEEE 802.15.4 Standard Basics
      • Channel access is via CSMA with collision avoidance and optional time slotting
      • Three bands, 27 channels specified
      • - 2.4 GHz: 16 channels, 250 kbps
      • - 868.3 MHz : 1 channel, 20 kbps
      • 902-928 MHz: 10 channels, 40 kbps
      • Message acknowledgment and an optional beacon structure
      • Multi-level security
      • Works well for selectable latency for controllers, sensors, remote monitoring and portable electronics
      • Configured for maximum battery life - has the potential to last as long as the shelf life of most batteries
    • IEEE 802.15.4 Characteristics
      • 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
      • Channel access using Carrier Sense Multiple Access with Collision Avoidance (CSMA - CA)
      • Addressing space of up to 64 bit IEEE address devices, 65,535 networks
    • ZigBee Applications
    • Architecture 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
    • ZigBee Alliance – IEEE- Customer Relations
    • Physical Layer
    • Physical Layer Functionalities
      • The IEEE802.15.4 PHY physical layer accommodates high levels of integration by using direct sequence to permit simplicity in the analog circuitry and enable cheaper implementations.
      • Activation and deactivation of the radio transceiver
      • Energy detection within the current channel
      • Link quality indication for received packets
      • Channel frequency selection
      • Data transmission and reception
    • IEEE 802.15.4 Physical Layer Frequency Band
    • IEEE 802.15.4 PHY/MAC Characteristics
      • PHY (2.4GHz and 868/915 MHz)
      • Data rates of 250 kbps (@2.4 GHz), 40 kbps (@ 915
      • MHz), and 20 kbps (@868 MHz)
      • Optimized for low duty-cycle applications (<0.1%)
      • CSMA-CA channel access
      • Optional guaranteed time slot for applications requiring low latency (Beaconing and GTS not used by ZigBee at this point)
    • MAC Layer
      • The IEEE 802.15.4 MAC media access control layer permits use of several topologies without introducing complexity and is meant to work with large numbers of devices.
    • IEEE 802.15.4 MAC Features
      • Employs 64-bit IEEE & 16-bit short addresses
      • – Ultimate network size can be 264 nodes (more than probably needed)
      • – Using local addressing, simple networks of more than 65,000 (216) nodes can be configured, with reduced address overhead
      • • Three devices specified
      • – Reduced Function Device (RFD)
      • – Full Function Device (FFD)
      • – Network coordinator (FFDC)
      • • Simple frame structure
      • • Reliable delivery of data
      • • Supports association/disassociation
      • • Supports AES-128 security
      • • Employs CSMA-CA channel access for better coexistence
      • • Offers Optional superframe structure with beacons, GTS mechanism
    • MAC Options
      • Non-beacon network
      • - Standard CSMA-CA communications
      • Positive acknowledgment for successfully received packets
      • Optional beacon-enabled network
      • - Superframe structure
      • • For dedicated bandwidth and low latency
      • • Set up by network coordinator to transmit beacons at predetermined intervals
      • » 15ms to 252sec (15.38ms ∗ 2n where 0 ≤ n ≤ 14)
      • » 16 equal-width time slots between beacons
      • » Channel access in each time slot is contention free
    • Network Pieces : PAN Coordinator PAN Coordinator • “ owns” the network • Starts it • Allows other devices to join it • Provides binding and address-table services • Saves messages until they can be delivered • And more… could also have i/o capability • A “full-function device” – FFD • Mains powered
    • Network Pieces : Router Routers • Routes messages • Does not own or start network • Scans to find a network to join • Given a block of addresses to assign • A “full-function device” – FFD • Mains powered depending on topology • Could also have i/o capability
    • Network Pieces : End Devices End Device • Communicates with a single device • Does not own or start network • Scans to find a network to join • Can be an FFD or RFD (reduced function device) • Usually battery powered
    • IEEE 802.15.4 Device Types
      • Network Coordinator
      • Maintains overall network knowledge; most sophisticated of the three types; most memory and computing power
      • Full Function Device (FFD)
      • - Carries full 802.15.4 functionality and all features specified by the standard
      • - Additional memory, computing power make it ideal for a network router function
      • - Could also be used in network edge devices where the network touches other networks or devices that are not IEEE 802.15.4 compliant
      • Reduced Function Device (RFD)
      • - Carriers limited (as specified by the standard) functionality to control cost and complexity
      • - General usage will be in network edge devices
    • ZigBee Device Model
      • ZigBee Coordinator (ZC)
      • - One and only one required for each ZigBee network.
      • - ZigBee Network has unique PAN ID and channel no
      • - Initiates network formation.
      • - Acts as 802.15.4 PAN coordinator (FFD).
      • - May act as router once network is formed.
      • ZigBee Router (ZR)
      • - Optional network component.
      • - May associate with ZC or with previously associated ZR.
      • - Acts as 802.15.4 coordinator (FFD).
      • - Participates in multihop routing of messages.
      • ZigBee End Device (ZED)
      • - Joins ZC or ZR.
      • - Optional network component.
      • - Acts as 802.15.4 End device (RFD).
      • - Optimized for very low power operation
      • - Shall not allow association and shall not participate in routing.
    • Network Topologies
    • ZigBee Network Formation
    •  
    • ZigBee Network Model
    • ZigBee Mesh Networking
    • Traffic Modes
      • ZigBee employs either of two modes, beacon or non-beacon to enable the to-and-fro data traffic.
      • Beacon mode is used when the coordinator runs on batteries and thus offers maximum power savings, whereas the Non-Beacon mode finds favor when the coordinator is mains-powered .
    • Beacon Mode
      • In the beacon mode, a device watches out for the coordinator's beacon that gets transmitted at periodically, locks on and looks for messages addressed to it. If message transmission is complete, the coordinator dictates a schedule for the next beacon so that the device ‘goes to sleep'; in fact, the coordinator itself switches to sleep mode.
      • For better latency beacon operation is desired. In this mode, devices are assigned one of 16 time slots between beacons. Beacon intervals can be from 15 ms up to 252 seconds .
    • Non-Beacon Mode
      • The non-beacon mode will be included in a system where devices are ‘asleep' nearly always, as in smoke detectors and burglar alarms. The devices wake up and confirm their continued presence in the network at random intervals
      • Non-beacon operation implies reliance on the CSMA and acknowledgment features for successful communications.
    • Data Transfer Model Data transferred from device to coordinator • In a beacon-enable network, device finds the beacon to synchronize to the super-frame structure. Then using slotted CSMA/CA to transmit its data. • In a non beacon-enable network, device simply transmits its data using un-slotted CSMA/CA
    • Data transferred from coordinator to device • In a beacon-enable network, the coordinator indicates in the beacon that “ data is pending .” • Device periodically listens to the beacon and transmits a MAC command request using slotted CSMA/CA if necessary.
    • THANK YOU