Introduction to the ZigBee Wireless Sensor and Control Network
ZigBee is a new standard developed by the ZigBee Alliance for personal-area networks (PANs). Consisting of more than 270 companies (including Freescale, Ember, Mitsubishi, Philips, Honeywell, and Texas Instruments), the ZigBee Alliance is a consortium that promotes the ZigBee standard for a low-rate/low-power wireless sensor and control network. The ZigBee protocol stack is built on top of IEEE 802.15.4, which defines the Media Access Control (MAC) and physical layers for low-rate wireless personal-area network (LR-WPAN). The ZigBee standard offers a stack profile that defines the network, security, and application layers. Developers are responsible for creating their own application profiles or integrating with the public profiles that were developed by the ZigBee Alliance. The ZigBee specification is an open standard that allows manufacturers to develop their own specific applications that require low cost and low power.
The ZigBee specification has undergone multiple modifications. The major milestones in its revision history are listed here:
- In 2004, the ZigBee Alliance published its first specification, which supported a home control lighting profile. However, the ZigBee Alliance no longer supports the 2004 specification.
- In February 2006, the ZigBee Alliance published the ZigBee Stack 2006, which contained modifications to ZigBee 2004.
In October 2007, the ZigBee Alliance published two feature sets called ZigBee and ZigBee PRO. The ZigBee feature set is interoperable with ZigBee PRO. If a network is based on the ZigBee PRO stack, devices from the ZigBee feature set stack can join the network as end devices. Likewise, if a network is based on the ZigBee stack, ZigBee PRO devices can join the network as end devices.
The ZigBee feature set is backward compatible with ZigBee 2006; a ZigBee feature set device can join in a ZigBee 2006 network and vice versa.
The ZigBee Alliance developed the following application profiles:
- Smart energy: ZigBee can be used to quickly read electrical, gas, and water meters. The ZigBee smart energy network enables wireless communication between the advanced metering infrastructure (AMI) and the home-area network; that is, the smart energy network will connect home appliances with the utility company for improving energy efficiency and managing peak demand.
- Commercial building automation: In a commercial building, ZigBee can be an integral tool in building maintenance. ZigBee wireless can be used to monitor smoke-detector operation and fire-door position. Suppose that a high-rise building contains 50 floors, with each floor having 50 rooms, and each room is equipped with a smoke detector. For safety reasons, each smoke detector must be tested every month. This requires checking 2,500 rooms! Instead of requiring that someone manually test the 2,500 smoke detectors, ZigBee allows a central station to remotely monitor each smoke detector. A ZigBee device may also be used to turn on and off a light without using any wire.
- Home automation: ZigBee home automation profile defines devices that are used for residential and commercial applications. ZigBee can be used to remotely control lighting, heating, cooling, and door-locking mechanisms. It can also remotely monitor smoke detectors and home security systems
- Personal, home, and hospital care (PHHC): This profile is used for monitoring the personal health of a patient at home without limiting a patient's mobility. For example, it can remotely monitor blood pressure and heart rate.
- Telecom applications: Embedding a ZigBee device into a mobile phone or PDA creates a new device called a ZigBee mobile device. A ZigBee mobile device can be used to communicate with other ZigBee devices. Users of ZigBee mobile devices can send and receive messages and share ring tones, contacts and images. More important, the ZigBee mobile device can even communicate with ZigBee devices that use different application profiles. For example, a ZigBee mobile device can be used to alert emergency services when a PHHC-enabled device detects a critical problem with the patient's health.
- Remote control for consumer electronics (ZigBee RF4CE): Currently, most remote controllers are using infrared (IR) technology, which requires line of sight; ZigBee RF4CE is a protocol that uses radio frequency (RF) to replace IR technology for remote controllers used in consumer electronics.
- Industrial process monitoring and control: ZigBee offers solutions for wireless sensor and control. Therefore, it can be used for monitoring and controlling industrial processes without using wire. For example, in inventory tracking, each piece of equipment can be tagged with a wireless sensor and can then be located by a ZigBee node. This process is called radio frequency identification (RFID). ZigBee can monitor machine condition and the performance of operating equipment within a plant; ZigBee can record and transmit such critical information as temperature, pressure, flow, tank level, humidity, and vibration.