An introduction to IEEE STD 802.15.4

The concept of simple sensor nets, devices the size of ping-pong balls, sprinkled liberally on the ground, has been around for a long time. Some of the big challenges have always been cost and complexity, as well as power consumption. While there have been a plurality of proprietary wireless systems developed over the past decade or so for application to this problem, these systems have suffered from an inability to scale well in cost and network complexity. In 2003, the IEEE 802.15.4 standard was ratified, and almost immediately silicon manufacturers began producing compliant single-chip radios. Now, the next generation of transceiver is on the horizon, complete with microcontroller and FLASH memory, as well as the potential for various environmental sensors to be built right into the silicon itself. IEEE STD 802.15.4 specifies the RF, PHY and MAC layers, and there are a variety of custom and industry-standards based networking protocols that can sit atop this IEEE stack. These networking protocols allow the rapid creation of mesh networks that are also self-healing. With energy-saving features designed into the basic IEEE standard, and other possibilities applied by the applications developer, IEEE 802.15.4 radios have the potential to be the cost-effective communications backbone for simple sensory mesh networks that can effectively harvest data with relatively low latency, high accuracy, and the ability to survive for a very long time on small primary batteries or energy-scavenging mechanisms like solar, vibrational, or thermal power. This paper will look closely at the IEEE standard and the features that are natively part of the standard. Some of the various networking protocols that are proposed for or being used on top of this standard will be discussed, including ZigBee networking and IPV6. Practical sensor devices employing the technology will be analyzed and power consumption investigated. In addition, the ongoing updates to the standard taking place now w- - ithin the IEEE will be discussed in light of their potential to make products developed to this standard even more useful to the sensor community