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IEEE 802.15.4

IEEE 802.15.4. Content. Overview Topologies Superframe structure Frame formatting Data service Management service Interframe spacing CSMA procedure. Introduction. Until recently the main concentration In wireless was on high throughput.

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IEEE 802.15.4

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  1. IEEE 802.15.4

  2. Content • Overview • Topologies • Superframe structure • Frame formatting • Data service • Management service • Interframe spacing • CSMA procedure

  3. Introduction • Until recently the main concentration In wireless was on high throughput. • Some applications for home automation, security, agriculture,industrial etc. have relaxed throughput requirements with low power consumption and low cost. • Existing standards are not suitable because of high complexity, power implications and high cost.

  4. Applications Home automation • heating, ventilation, and air conditioning, security, lighting, and the control of objects. Industrial • detecting emergency situations, monitoring machines Automotive • automotive sensing, such as tire pressure monitoring; Agriculture • sensing of soil moisture, pesticide, herbicide, and pH levels. Others • Controlling consumer electronics, PC peripherals etc. Data rate needed ranges from 115.2 kb/s to less than 10 kb/s.

  5. 802.15.4 Architecture Upper Layers IEEE 802.2 IEEE 802.15.4 SSCS LLC, Type I IEEE 802.15.4 MAC IEEE 802.15.4 IEEE 802.15.4 868/915 MHz 2400 MHz PHY PHY

  6. Protocol Drivers • Extremely low cost • Ease of installation • Reliable data transfer • Short range operation • Reasonable battery life

  7. 802.15.4 Overview • Star and peer-to-peer topologies • Optional frame structure • Association • CSMA-CA channel access mechanism • Packet validation and message rejection • Optional guaranteed time slots • Guaranteed packet delivery • Facilitates low-power operation • Security

  8. IEEE 802.15.4 Device Classes • Full function device (FFD) • Any topology • PAN coordinator capable • Talks to any other device • Implements complete protocol set • Reduced function device (RFD) • Limited to star topology or end-device in a peer-to-peer network. • Cannot become a PAN coordinator • Very simple implementation • Reduced protocol set

  9. IEEE 802.15.4 Definitions • Network Device: An RFD or FFD implementation containing an IEEE 802.15.4 medium access control and physical interface to the wireless medium. • Coordinator: An FFD with network device functionality that provides coordination and other services to the network. • PAN Coordinator: A coordinator that is the principal controller of the PAN. A network has exactly one PAN coordinator.

  10. Low-Power Operation • Duty-cycle control using superframe structure • Beacon order and superframe order • Coordinator battery life extension • Indirect data transmission • Devices may sleep for extended period over multiple beacons • Allows control of receiver state by higher layers

  11. Typical Network Topologies

  12. FFD Communications flow RFD Star Topology PAN coordinator Master/slave

  13. FFD Communications flow RFD Peer-Peer Topology PAN coordinators Point to point Cluster tree

  14. FFD Communications flow RFD Combined Topology Clustered stars - for example, cluster nodes exist between rooms of a hotel and each room has a star network for control.

  15. Technical Characteristics • Physical layer • 20 kbps over 1 channel @ 868-868.6 MHz • 40 kbps over 10 channels @ 905 – 928 MHz • 250 kbps over 16 channels @ 2.4 GHz • MAC protocol • Single channel at any one time • Combines contention-based and schedule-based schemes • Asymmetric: nodes can assume different roles

  16. Physical Frequencies and Channels Channel 0 Channels 1-10 2 MHz 868MHz / 915MHz PHY 868.3 MHz 902 MHz 928 MHz 2.4 GHz PHY Channels 11-26 5 MHz 2.4 GHz 2.4835 GHz

  17. IEEE 802.15.4 PHY Overview Modulation/Spreading • 2.4 GHz PHY • 250 kb/s (4 bits/symbol, 62.5 kBaud) • Data modulation is 16-ary orthogonal modulation • 16 symbols are ~orthogonal set of 32-chip PN codes • Chip modulation is MSK at 2.0 Mchips/s • 868MHz/915MHz PHY • Symbol Rate • 868 MHz Band: 20 kb/s (1 bit/symbol, 20 kBaud) • 915 MHz Band: 40 kb/s (1 bit/symbol, 40 kBaud) • Data modulation is BPSK with differential encoding • Spreading code is a 15-chip m-sequence • Chip modulation is BPSK at • 868 MHz Band: 300 kchips/s • 915 MHz Band: 600 kchips/s

  18. IEEE 802.15.4 PHY Overview 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 Measurements • Packet strength indication • Clear channel assessment • Dynamic channel selection

  19. IEEE 802.15.4 PHY Overview Packet Structure • PHY Packet Fields • Preamble (32 bits) – synchronization • Start of Packet Delimiter (8 bits) • PHY Header (8 bits) – PSDU length • PSDU (0 to 1016 bits) – Data field Start of Packet Delimiter PHY Header PHY Service Data Unit (PSDU) Preamble 6 Octets 0-127 Octets

  20. IEEE 802.15.4 MAC Overview General Frame Structure • 4 Types of MAC Frames: • Data Frame • Beacon Frame • Acknowledgment Frame • MAC Command Frame

  21. IEEE 802.15.4 MAC overview • All devices have IEEE addresses • Short addresses can be allocated • Addressing modes: • Network + device identifier (star) • Source/destination identifier (peer-peer)

  22. 15ms * 2n where 0  n  14 Network beacon Transmitted by PAN coordinator. Contains network information, frame structure and notification of pending node messages. Beacon extension period Space reserved for beacon growth due to pending node messages Contention period Access by any node using CSMA-CA Guaranteed Time Slot Reserved for nodes requiring guaranteed bandwidth [n = 0]. Optional Frame Structure Battery life extension GTS 3 GTS 2 GTS 1 Contention Access Period Contention Free Period Slot

  23. 15ms * 2SO where 0  SO  14 15ms * 2BO where SO  BO  14 Optional Frame Structure • Superframe may have inactive period Inactive Period SO = Superframe order BO = Beacon order

  24. IEEE 802.15.4 MAC overview • Star networks: devices are associated with coordinators • Forming a PAN, identified by a PAN identifier • Coordinator • Bookkeeping of devices, address assignment, generate beacons • Talks to devices and peer coordinators • Beacon-mode superframe structure • GTS assigned to devices upon request b

  25. General MAC Frame Format Frame control field

  26. Beacon Frame Format

  27. MAC Command Frame • Command Frame Types • Association request • Association response • Disassociation notification • Data request • PAN ID conflict notification • Orphan Notification • Beacon request • Coordinator realignment • GTS request

  28. Data Frame Format Acknowledgement Frame Format

  29. Data Service • Data transfer to neighboring devices • Acknowledged or unacknowledged • Direct or indirect • Using GTS service • Maximum data length (MSDU) aMaxMACFrameSize(102 bytes)

  30. Data TransferMessage Sequence Diagram

  31. Indirect Data TransferMessage Sequence Diagram

  32. Passive Scan

  33. Active Scan

  34. OrphaningMessage Sequence Diagram

  35. Inter-frame Spacing For frames ≤ aMaxSIFSFrameSize use short inter-frame spacing (SIFS) For frames > aMaxSIFSFrameSize use long inter-frame spacing (LIFS)

  36. Slotted CSMA Procedure Used in beacon enabled networks.

  37. Un-slotted CSMA Procedure Used in non-beacon networks.

  38. 802.15.4 Architecture Applications • Network Routing • Address translation • Packet Segmentation • Profiles ZigBee IEEE 802.15.4 MAC IEEE 802.15.4 IEEE 802.15.4 868/915 MHz 2400 MHz PHY PHY

  39. ZigBee • Relation to 802.15.4 similar to Bluetooth / 802.15.1 • Pushed by Chipcon (now TI), ember, freescale (Motorola), Honeywell, Mitsubishi, Motorola, Philips, Samsung… • More than 260 members • about 15 promoters, 133 participants, 111 adopters • must be member to commercially use ZigBee spec • ZigBee platforms comprise • IEEE 802.15.4 for layers 1 and 2 • ZigBee protocol stack up to the applications

  40. ZigBee Stack Architecture

  41. Typical ZigBee-Enabled Device Design Typical design consist of RF IC and 8-bit microprocessor with peripherals connected to an application sensor or actuators

  42. 34KB /14KB 356 mA Wireless Technology Comparison Chart

  43. Competing/Similar Technologies • Bluetooth • http://www.bluetooth.org • http://www.bluetooth.com • X10 • Powerline protocol first introduced in the 1970's. • http://www.x10.com/technology1.htm • Z-wave • Proprietary protocol for wireless home control networking. • http://www.z-wavealliance.com/ • INSTEON • Peer-to-peer mesh networking product that features a hybrid radio/powerline transmission • http://www.insteon.net • nanoNET • Proprietary set of wireless sensor protocols, designed to compete with ZigBee. • http://www.nanotron.com/

  44. Bluetooth based WPAN Few devices Data range is 10m to 100m Data rate is nearly 1Mb/s Power consumption is a low. Battery life is low. Star only. IEEE 802.15.4 LR-WPAN Many devices Data range is nearly 10m Data rate is 20 kb/s,40kb/s,250kb/s. Power consumption is ultra low. Battery lasts years. peer to peer,Star. Bluetooth vs IEEE 802.15.4.

  45. Summary • 802.15.4: Low-Rate, Very Low-Power • Low data rate solution with multi-month to multi-year battery life and very low complexity • Potential applications are sensors, interactive toys, smart badges, remote controls, and home automation • Data rates of 20-250 kbit/s, latency down to 15 ms • Master-Slave or Peer-to-Peer operation • Up to 254 devices or 64516 simpler nodes • Support for critical latency devices, such as joysticks • CSMA/CA channel access (data centric), slotted (beacon) or unslotted • Automatic network establishment by the PAN coordinator • Dynamic device addressing, flexible addressing format • Fully handshaked protocol for transfer reliability • Power management to ensure low power consumption • 16 channels in the 2.4 GHz ISM band, 10 channels in the 915 MHz US ISM band and one channel in the European 868 MHz band • Basis of the ZigBee technology – www.zigbee.org

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