ZigBee Module 구성도

IEEE 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

IEEE LR-WPAN

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

IEEE 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

IEEE 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 / Bluetooth

IEEE 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)

IEEE MAC  MAC-Related Parameters  One symbol duration 16 usec 25 usec 50 usec  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

IEEE 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

IEEE MAC  General MAC Frame Format

IEEE 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

IEEE PHY  Operating Frequency Bands

IEEE PHY  Channel Frequencies  Modulation Parameters

IEEE PHY  PHY Common Parameters  Transmit Power Capable of at least 1 mW  Transmit Center Frequency Tolerance - 40 ppm  Receiver Sensitivity (Packet Error Rate <1%) GHz band /915 MHz band  RSSI Measurement Packet strength indication Clear channel assessment (CCA) Dynamic channel selection  PHY Frame Structure

IEEE  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

ZigBee Spec. V1.0

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

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

ZigBee Spec. V1.0  Routing Table  Route Discovery Table

ZigBee Spec. V1.0  Routing Cost

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

ZigBee Spec. V1.0  Joining a network  Joining by orphaning

ZigBee Spec. V1.0  NWK setting for a residential stack