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ZigBee Module 구성도

ZigBee Module 구성도. IEEE 802.15.4 LR-WPAN. Low power consumption Frequent battery change is not desired and/or not feasible Low cost Otherwise, wireline alternative may be preferred An application itself may not be attractive High throughput is not required

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ZigBee Module 구성도

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  1. ZigBee Module 구성도

  2. IEEE 802.15.4 LR-WPAN • Low power consumption • Frequent battery change is not desired and/or not feasible • Low cost • Otherwise, wireline alternative may be preferred • An application itself may not be attractive • High throughput is not required • Typically, short-lived sporadic messages • Latency or reliability could be more important

  3. IEEE 802.15.4 LR-WPAN

  4. IEEE 802.15.4 LR-WPAN

  5. IEEE 802.15.4 LR-WPAN

  6. IEEE 802.15.4 MAC • Extremely low cost • Ease of implementation • Reliable data transfer • Short range operation • Very low power consumption • Simple, but flexible protocol

  7. IEEE 802.15.4 MAC • Network Coordinator • Transmits network beacons • Sets up a network • Manages network nodes • Stores network node information • Routes messages between paired nodes • Receives constantly • Network Node • Generally battery powered • Searches for available networks • Transfers data from its application as necessary • Determines whether data is pending • Requests data from the network coordinator • Can sleep for extended periods

  8. IEEE 802.15.4 MAC • Device Classes • Full function device (FFD) • Any topology • Network coordinator capable • Talks to any other device • Reduced function device (RFD) • Limited to star topology • Cannot become a network coordinator • Talks only to a network coordinator • Very simple implementation • MAC Features • Association, disassociation • Acknowledged frame delivery • Channel access mechanism • Frame validation • Guaranteed time slot management • Beacon management • MAC management has 26 primitives • cf. 131 primitives of 802.15.1 / Bluetooth

  9. IEEE 802.15.4 MAC • Access Mechanisms • Carrier-Sense Multiple Access with Collision Avoidance (CSMA-CA) • Either slotted or unslotted version used • Slotted CSMA-CA in a beacon-enabled network • Unslotted or standard CSMA-CA in networks without beacons • Optionally, contention-free access using Guaranteed Time Slots (GTSs)

  10. IEEE 802.15.4 MAC • MAC-Related Parameters • One symbol duration • 16 usec (@2.4GHz), 25 usec (@900MHz), 50 usec (@800MHz) • aUnitBackoffPeriod = 20 symbols • Backoff countdown unit • aBaseSlotDuration = 60 symbols • A superframe slot = aBaseSlotDuration * 2^SO • SO = superframe order • CCA detection time = 8 symbols • Random backoff [0,2^BE-1] • Backoff exponent BE increases by one whenever CCA busy • macMinBE = 0~3 (3 is default) • If macMinBE=0, collision avoidance is disabled for the first tx attempt • aMaxBE = 5 (constant) • aMaxFrameRetries = 3 (constant) • Contention window CW for slotted CSMA-CA • Initially 2, and decreases by one after a CCA idle assessment • To avoid a potential collision with an ACK transmission

  11. IEEE 802.15.4 MAC • Power Save Mechanisms • Going to sleep state as often as possible by utilizing: • Inactive mode in superframes • Snooze mode of coordinator • No beacon transmission in snooze mode • GTS for other devices • Extracting pending messages from coordinator • Using data request command • Message pending indicated in beacon frames • Addressing • All devices have unique 64-bit extended addresses • 8-bit or 16-bit short addresses can be allocated during association • Addressing modes: • Network + device identifier • Source/destination identifier

  12. IEEE 802.15.4 MAC • General MAC Frame Format

  13. IEEE 802.15.4 MAC • MAC Frame Components • Frame control • MAC frame type, Address field format • Controls the ACK – ACK or no ACK • Address Information • Variable number of addresses • 8-bit/16-bit short or 64-bit extended address • Sequence number • Same number use for the subsequent ACK • Frame check sequence (FCS) • CRC-16 for frame integrity check • Four Types of MAC Frames • Data Frame • Acknowledgment Frame • After TurnaroundTime (12 symbols) or aUnitBackoffPeriod boundary • Beacon Frame • Specifies devices with pending messages • MAC Command Frame • Association request/response • Data request for pending messages • GTS request/allocation and many others

  14. IEEE 802.15.4 PHY • Operating Frequency Bands

  15. IEEE 802.15.4 PHY • Channel Frequencies • Modulation Parameters

  16. IEEE 802.15.4 PHY • PHY Common Parameters • Transmit Power • Capable of at least 1 mW • Transmit Center Frequency Tolerance - 40 ppm • Receiver Sensitivity (Packet Error Rate <1%) • -85 dBm @ 2.4 GHz band • -92 dBm @ 868/915 MHz band • RSSI Measurement • Packet strength indication • Clear channel assessment (CCA) • Dynamic channel selection • PHY Frame Structure

  17. IEEE 802.15.4 • Characteristics • Simpler PHY • One Tx rate per channel • Low Tx power • Simpler MAC • No virtual carrier-sense • No worry about hidden nodes • No RTS/CTS & No fragmentation • No continuous CCA • Relaxed timing requirement • Extensive power saving features • Zigbee Stack Requirements • 8-bit μC, e.g., 80c51 • Full protocol stack <32k • Simple node only stack ~4k • Coordinators require extra RAM • Node device database • Transaction table • Pairing table

  18. ZigBee Spec. V1.0

  19. ZigBee Spec. V1.0 • ZigBee Coordinator (ZC) • One and only one required for each ZB network. • Initiates network formation. • Acts as 802.15.4 2003 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 2003 coordinator (FFD). • Participates in multihop routing of messages. • ZigBee End Device (ZED) • Optional network component. • Shall not allow association. • Shall not participate in routing.

  20. ZigBee Spec. V1.0

  21. ZigBee Spec. V1.0

  22. ZigBee Spec. V1.0

  23. ZigBee Spec. V1.0 • ZigBee Routing • If you’ve got a routing table entry then use it. • If you’ve got a routing table and there’s room • for another entry then try route discovery. • Otherwise, route along the tree (if you can). • Tree Routing

  24. ZigBee Spec. V1.0 • Routing Table • Route Discovery Table

  25. ZigBee Spec. V1.0 • Routing Cost

  26. ZigBee Spec. V1.0 • Starting a network • Permitting a device to join

  27. ZigBee Spec. V1.0 • Joining a network • Joining by orphaning

  28. ZigBee Spec. V1.0 • NWK setting for a residential stack

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