IEEE 802.15.4 was designed to address the need for a low-cost, low-power wireless standard optimized for monitoring and control applications.  While similar to other low power wireless standards, features such as fast power-on latency and mesh networking help differentiate it from the field of other existing IEEE technologies. 

IEEE 802.15.4 has become a solid foundation for low rate wireless solutions, including ZigBee, WirelessHART and SP100 network stacks.  IEEE 802.15.4 was first released in 2003 and the specification defines 3 bands: 868 MHz, 900 MHz and 2.4 GHz.  It is the latter 2.4GHz band that is most popular due to the global regulatory approvals of the 2.4 Ghz ISM band.  IEEE 802.15.4 supports AES128 bit encryption which is considered sufficient by most applications today.  It has a very simple frame structure that provides a maximum payload of around 100 bytes, which is typical of the small amount of data required for these applications.  It was also designed with reliability in mind and uses carrier sense multiple access with collision avoidance (CSMA-CA) as the access method, message acknowledgement to ensure delivery, energy detection to pick channels and Link Quality to check the quality of the connection.  All of these features help ensure reliable data deliver, even in the presence of interference.  For device addressing, it uses IEEE 64 bit addresses for the physical device and then assigns a 16 bit address when joining the network.  IEEE 802.15.4 also supports multiple network types, including peer-to-peer, star, cluster tree and mesh networks.  For networks that require a more deterministic delivery, it can support beaconed networks to provider a certain amount of QOS is required.

IEEE 802.15.4 Protocol Benefits

• 2.4 GHz, 16 channels, 250 kbps data rate
• DSSS energy spreading scheme
• CSMA-CA
• AES 128 encryption and authentication 
• Simple frame structure 
• Reliable data delivery
• Message acknowlegement 
• Energy detection and link quality indication