802.15.4 / ZigBee Architecture

Basics

802.15.4 is a simple packet data protocol for lightweight wireless networks.

• Channel Access is via Carrier Sense Multiple Access with collision avoidance and optional time slotting.

• Message acknowledgment and an optional beacon structure.

• Multi-level security.

• Works well for.

  • Long battery life, selectable latency for controllers, sensors, remote monitoring and portable electronics.

• Configured for maximum battery life, has the potential to last as long as the shelf life of most batteries.

General characteristics

Data rates of 250 kbps , 20 kbps and 40kpbs.

Star or Peer-to-Peer operation.

Support for low latency devices.

SMA-CA channel access, with CCA detection.

• Clear Channel Assessment.

Dynamic device addressing.

Fully handshaked protocol for transfer reliability.

Low power consumption.

16 channels in the 2.4GHz ISM band.

10 channels in the 915MHz ISM band.

One channel in the European 868MHz band.

Extremely low duty-cycle (<0.1%).

Frequency bands

Operates in Unlicensed Bands.

• ISM 2.4 GHz Global Band at 250kbps.

• 868 MHz European Band at 20kbps.

• 915 MHz North American Band at 40kbps.

PHY frame structure

PHY packet fields.

• Preamble (32 bits) – synchronization.

• Start of packet delimiter (8 bits) – shall be formatted as “11100101”.

• PHY header (8 bits) – PSDU length.

• PSDU (0 to 127 bytes) – data field.