The increasing interest around the world in development of "smart grids" requires the acceptance of communications standards that are designed specifically for low power, low data rate networks. The protocols need to be secure, robust, and resistant to outside RF interference in order to be used for industrial and home automation networks.

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. Some of its benefits are:

• 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 acknowledgement
• Energy detection and link quality indication

The simple frame structure provides a maximum payload of around 100 bytes, which is typical of the small amount of data required for the industrial and home applications. One solution based on the IEEE 802.15.4 standard is ZigBee - an internationally recognized open protocol. Interoperability is one of the main requirements for the successful implementation of smart grid technology. It is supported by the ZigBee Alliance, which ensures interoperability and compatibility of components from a wide range of suppliers.

A significant advantage of ZigBee networks is their ability to mesh - i.e. to use other nodes as repeaters to relay a message to another node that is out of the maximum 76 meters (250 feet) range. Such networks are also self-healing - messages are automatically rerouted around a node that has failed. The 2.4 GHz ISM (industrial, scientific, and medical) band used by ZigBee has been set aside for unlicensed operation, meaning anyone is allowed to use it without having to obtain a license from a governmental regulatory body.

More information at:
www.zigbee.org