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IEEE 802.15.4#

IEEE 802.15.4 is the standard for "Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for Low-Rate Wireless Personal Area Networks (LR-WPANs)"

Maximum Values#

  • Raw data rate: 250 kbps
  • Transmission Power: 1 mW
  • Typical range: 10 m
  • PHY payload: 127 bytes Reason: to ensure low packet and bit error rates in a lossy RF environment
  • Address: 16 bit or 64 bit

Superframe Structure#

The communication of IEEE 802.15.4 networks is structured into Superframes, which is the perdiod between two coordinator beacons. Each superframe consists of an active and an inactive period but the length of the inactive perdiod may be zero.

  ||      active        |  inactive    ||
  ||   CAP |  CFP       |              ||
  ||       |            |              ||
Beacon                               Beacon

TODO page 58 image

Frame Structure#

                            | MAC head |   MAC   | MAC foot |
                            |   (MHR)  | payload |  (MFR)   |
                              \                           /
|  Sync. header  |  PHY header  |     PHY payload       |
|     (SHR)      |    (PHR)     |        (PSDU)         |

A cyclic redundancy check (CRC) is used to detect errors in every PSDU.

Access Methods#

  • Unslotted CSMA-CA used in nonbeacon-enabled PANs
  • Slotted CSMA-CA used in beacon-enabled PANs
  • TSCH CCA used in non-shared slots in a TSCH PAN
  • TSCH CSMA-CA used for shared slots in a TSCH PAN
  • CSMA-CA with PCA in for critical events

Deterministic and Synchronous Multi-channel Extension (DSME)#

If several coordinators are present, the communication is structured into Multi-Superframes. A multi-superframe consists of repeated superframes, each of which consists of an Enhanced Beacon frame, a CAP and a CFP.

Device Types#


A full-Function Device (FFD) is a device that is capable of serving as a personal area network (PAN) coordinator.


A Reduced-Function Device (RFD) is a device that is not capable of serving as a coordinator and is intended for applications that are extremely simple.


  • Star
  • P2P / Mesh

TODO figure from p 51

Physical Layer 1 (PHY)#


  • Link quality indicator (LQI) for received packets
  • Channel frequency selection
868 MHz 2.4 GHz
Modulation BPSK O-QPSK
Channels 1 16
Bit Rate 20 kbps 250 kbps
Symbols 1 bit/smyb 4 bit/symb
Chips/Symbol 15 32

PHY Header (6 byte)#

  • Preamble: 4 byte all zero
  • Start-of-frame delimiter: 1 byte (0b11100101)
  • Length: 1 byte (bits 0-6, bit 7 reserved)


  • 3 channels available in 868MHz bands
  • 30 channels available in the 915MHz bands
  • 16 channels available in the 2.4GHz bands

Medium Access Layer 2 (MAC)#

  • 4 types of MAC frames: Data, Beacon, Ack, Command
  • typically 25 bytes MAC header

Beacon Enabled#

  • PAN Coordinator sends beacons. The beacon interval defines one superframe. Each superframe is divided into 16 time slots.

Slots: * Contention Access Period (CAP): competetive access with CSMA/CA or ALOHA, collisions possible * Contention Free Period (CFP): slots are asigned to individual devices

  • Access Management:
    • Scheduled access ("I Tell You when to Talk") with beacons
    • Random access ("You Decide when to Talk but prepare for Collisions")
    1. Carrier Sense: prior to transmitting, a node first listens to the shared medium to determine whether another node is transmitting or not.
    2. Collision Avoidance: if another node was heard, we wait for a period of time (usually random) for the node to stop transmitting before listening again for a free communications channel.
  • AES-128