IEEE 802.15.4 Reference
The IEEE 802.15.4 standards define low-power wireless radio techniques for what the IEEE calls wireless personal area networks (WPANs). Today IEEE 802.15.4 is a vastly popular radio standard used with a much broader range of applications than what the term WPAN might seem to describe. It is aimed at providing cheap, low-power, shortrange communications for embedded devices. Several other standards or stack specifications use IEEE 802.15.4 as their physical layer (PHY) and data link-layer (DLL), including 6LoWPAN, ISA100 and ZigBee specifications.
The latest version of the standard is IEEE 802.15.4-2006 [IEEE802.15.4]. Channel sharing is achieved using carrier sense multiple access (CSMA), and acknowledgments are provided for reliability. Link-layer security is provided with 128-bit AES encryption, described further in Appendix B.3. Addressing modes utilizing 64-bit and 16-bit addresses are provided with unicast and broadcast capabilities. The payload of the physical frame can be up to 127 bytes in size, with 72–116 bytes of payload available after link-layer framing, depending on a number of addressing and security options.
The MAC can be run in two modes: beaconless and beacon-enabled. Beaconless mode uses a pure CSMA channel access and operates quite like basic IEEE 802.11 without channel reservations. Beacon-enabled mode is more complex, with a superframe structure and the possibility to reserve time-slots for critical data. IEEE 802.15.4 ...