An Low Rate-Wireless Personal Area Networks (LR-WPAN) is a simple, low-cost communication network that allows wireless connectivity in applications with limited power and relaxed throughput requirements. The main objectives of an LR-WPAN are ease of installation, reliable data transfer, short-range operation, extremely low cost, and a reasonable battery life, while maintaining a simple and flexible protocol.
Two different device types can participate in an IEEE 802.15.4 network; a full-function device (FFD) and a reduces-fuction device (RFD). The FFD can operate in three modes serving as a personal arena network (PAN) coordinator, a cordinator, or a device. An FFD can talk to RFDs or other FFDs, while an RFD can talk only to an FFD. an RFD is intended for applications that are extremely simple, such as light switch or a passive infrared sendor, they don’t have the need to send large amoubts of data and may only associate with a single FFD at a time. Consequenlt, the RFD can be implemented using minimal resources and memory capacity.
reference : IEEE standard 808.15.4
Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for Low-Rate Wireless Personal Area Networks (WPANs)