WIRELESS STANDARDS seem to he breeding. Perhaps as soon as you get two of them nicely settled in an unlicensed hit of spectrum it‘s inevitable. Late last year, ZigBee arrived in the 2.4GHz band, joining the now well-established Bluetooth and Wi-Fi. ZigBee looks rather like Bluetooth but is simpler, has a lower data rate and spends most of its time snoozing. This characteristic means that a node on a ZigBee network should be able to run for six months to two years on just two AA batteries, claim backers.
EARLY PROMOTION
Philips, Motorola, Honeywell, Invensys and Mitsubishi Electric started promoting ZigBee when they formed the ZigBee Alliance in October 2002. This was once they had secure the physical layer(PHY) and media access control(MAC) under the IEEE 802.15.4 WPAN(Wireless Personal Area Network) Standard.
Zigbee
ZigBee is the emerging industrial standard for ad hoc networks based on IEEE 802.15.4. Due to characteristics such as low data rate, low price, and low power consumption, ZigBee is expected to be used in wireless sensor networks for remote monitoring, home control, and industrial automation. Since one of the most important goals is to reduce the installation and running cost, ZigBee stack is embedded in small and cheap micro-controller units. Since tree routing does not require any routing tables to send the packet to the destination, it can be used in ZigBee end devices that have limited resources.
The ZigBee standard can operate in the 2.4GHz band or the 868MHz and 915MHz ISM (industrial, scientific and medical) bands used in Europe and the US respectively It sits below Bluetooth in terms of data rate: 250kbps at 2.4GHz (compared to Bluetooth's 1Mbps) and 20-40kbps in the lower frequency bands. The operational range is 10-75m, compared to 1Om for Bluetooth (without a power amplifier).
One other important difference between ZigBee and Bluetooth is in how their protocols work. ZigBee's uses a basic master-slave configuration suited to static star networks of many infrequently used devices that talk via small data packets. This aspect suits ZigBee to building
automation and the control of multiple lights, security sensors and so on.
Bluetooth's protocol is more complex because it's geared towards handling voice, images and file transfers in ad hoc networks. Bluetooth devices can work peer-to-peer and support scatternets of multiple smaller non-synchronised networks (piconets). The protocol, however, only allows up to eight slave nodes in a basic master-slave piconet set-up. ZigBee allows up to 254 nodes. Masters can talk to each other and the number of nodes can he increased beyond 254 if necessary.
Low latency is another important feature of ZigBee. When a ZigBee device is powered down (all circuitry switched off apart from a clock running at 32kHz), it can wake up and get a packet across a network connection in around 15 milliseconds. A Bluetooth device in a similar state would take around three seconds to wake up and respond. “The latency gives you some power consumption advantages and it‘s important for timing-critical messages. A sensor in an industrial plant needs to get its messages through in milliseconds”.
EARLY PROMOTION
Philips, Motorola, Honeywell, Invensys and Mitsubishi Electric started promoting ZigBee when they formed the ZigBee Alliance in October 2002. This was once they had secure the physical layer(PHY) and media access control(MAC) under the IEEE 802.15.4 WPAN(Wireless Personal Area Network) Standard.
Zigbee
ZigBee is the emerging industrial standard for ad hoc networks based on IEEE 802.15.4. Due to characteristics such as low data rate, low price, and low power consumption, ZigBee is expected to be used in wireless sensor networks for remote monitoring, home control, and industrial automation. Since one of the most important goals is to reduce the installation and running cost, ZigBee stack is embedded in small and cheap micro-controller units. Since tree routing does not require any routing tables to send the packet to the destination, it can be used in ZigBee end devices that have limited resources.
The ZigBee standard can operate in the 2.4GHz band or the 868MHz and 915MHz ISM (industrial, scientific and medical) bands used in Europe and the US respectively It sits below Bluetooth in terms of data rate: 250kbps at 2.4GHz (compared to Bluetooth's 1Mbps) and 20-40kbps in the lower frequency bands. The operational range is 10-75m, compared to 1Om for Bluetooth (without a power amplifier).
One other important difference between ZigBee and Bluetooth is in how their protocols work. ZigBee's uses a basic master-slave configuration suited to static star networks of many infrequently used devices that talk via small data packets. This aspect suits ZigBee to building
automation and the control of multiple lights, security sensors and so on.
Bluetooth's protocol is more complex because it's geared towards handling voice, images and file transfers in ad hoc networks. Bluetooth devices can work peer-to-peer and support scatternets of multiple smaller non-synchronised networks (piconets). The protocol, however, only allows up to eight slave nodes in a basic master-slave piconet set-up. ZigBee allows up to 254 nodes. Masters can talk to each other and the number of nodes can he increased beyond 254 if necessary.
Low latency is another important feature of ZigBee. When a ZigBee device is powered down (all circuitry switched off apart from a clock running at 32kHz), it can wake up and get a packet across a network connection in around 15 milliseconds. A Bluetooth device in a similar state would take around three seconds to wake up and respond. “The latency gives you some power consumption advantages and it‘s important for timing-critical messages. A sensor in an industrial plant needs to get its messages through in milliseconds”.
