IEEE 802.15.4 Connectivity Technologies in IOT

Communication Protocols

The following communication protocols have immediate importance to consumer and industrial IoT :

• IEEE 802 .15.4
• Zigbee
• 6LoWPAN
• Wireless HART
• Z-Wave
• ISA 100
• Bluetooth
• NFC
• RFID

Features of IEEE 802.15.4

• Well-known standard for low data-rate WPAN.
• Developed for low-data-rate monitoring and control applications and extended-life low-power-consumption uses.
• This standard uses only the first two layers (PHY,MAC) plus the logical link control (LLC) and service specific convergence sub-layer (SSCS) additions to communicate with all upper layers
• Operates in the ISM band.

• Uses direct sequence spread spectrum (DSSS) modulation
• Highly tolerant of noise and interference and offers link reliability improvement mechanisms.
• Low-speed version use Binary Phase Shift Keying (BPSK).
• High data-rate versions use offset-quadrature phase-shift keying (O-QPSK).
• Uses carrier sense multiple access with collision avoidance (CSMA-CA) for channel access.
• Multiplexing allows users or nodes interference-free access to the same channel at different times.

IEEE 802.15.4 Variants

IEEE 802.15.4 Types

Full Function Device (FFD)

• Can talk to all types of devices
• Supports full protocol

Reduced Function Device (RFD)

• Can only talk to an FFD
• Lower power consumption
• Minimal CPU/RAM required

IEE 802.15.4 Frames

Beacon Enabled Networks

• Periodic transmission of beacon messages
• Data -frames sent via Slotted CSMA/CA with a super frame structure managed by PAN coordinator
• Beacons used for synchronization & association of other nodes with the coordinator
• Scope of operation spans the whole network.

Non-Beacon Enabled Networks

• Data-frames sent via un-slotted CSMA/CA (Contention Based)
• Beacons used only for link layer discovery
• Requires both source and destination IDs.
• As 802.15.4 is primarily, a mesh protocol, all protocol addressing must adhere to mesh configurations
• De-centralized communication amongst nodes

Books :

MAC Protocols for Cyber-Physical Systems (SpringerBriefs in Computer Science) 2015 Edition, Kindle Edition by Feng Xia (Author), Azizur Rahim (Author, Contributor)