1. Wireless NETWORKS NET 434 Topic No 8 Wireless PANs ZiGBee NEtworks
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2. Introduction IEEE 802.11 WPANs
Ethernet matching speed
Long range(100m)
Complexity to handle seamless roaming
Data throughput of 2-11Mbps
WPANs
Space around a person or object that extends up to 10m in all directions.
Low-cost
Low power
Short range
Very small size.
IEEE working group created WPAN standard.
This group has currently defined three classes of WPANs that are differentiated on the following basis
Data rate,
Battery drain
Quality of service(QoS).

3. introduction High data rate WPAN (IEEE 802.15.3)
Suitable for multi-media applications that require very high QoS.
Medium rate WPANs (IEEE /Blueetooth)
To handle a variety of tasks ranging from cell phones to PDA communications and have QoS suitable for voice communications.
Low rate WPANs(IEEE /LR-WPAN)
To serve a set of industrial, residential and medical applications with very low power consumption and cost requirement not considered by the above WPANs and with relaxed needs for data rate and QoS.
The low data rate enables the LR-WPAN to consume very little power.
Zigbee
IEEE committee started working on a low data rate standard a short while later.
Then the ZigBee Alliance and the IEEE decided to join forces and ZigBee is the commercial name for this technology.

4. Zigbee
Power Consumption: ZigBee is expected to provide low cost low power connectivity for equipment that needs battery life as long as several months to several years but does not require data transfer rates as high as those enabled by Bluetooth.
Topology: ZigBee can be implemented in mesh networks larger
Range: ZigBee compliant wireless devices are expected to transmit meters, depending on the RF environment and the power output consumption required for a given application
Band:The unlicensed RF worldwide(2.4GHz global, 915MHz Americas or 868 MHz Europe).
Data Rate: The data rate is 250kbps at 2.4GHz, 40kbps at 915MHz and 20kbps at 868MHz.

5. Zigbee Versus Bluetooth
ZIGBEE is simpler than BLUETOOTH
Data Rate: ZIGBEE has a lower data rate and spends most of its time snoozing.
Battery Life: Low data rate 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.
Operational Range: The operational range of ZigBee is 10-75m compared to 10m for Bluetooth(without a power amplifier).
Data Rate: ZigBee sits below Bluetooth in terms of data rate. The data rate of ZigBee is 250kbps at 2.4GHz, 40kbps at 915MHz and 20kbps at 868MHz whereas that of Bluetooth is 1Mbps.
Configuration: ZigBee uses a basic master-slave configuration suited to static star networks of many infrequently used devices that talk via small data packets.
It allows up to 254 nodes.
Bluetooth’s protocol is more complex since it is geared towards handling voice, images and file transfers in ad hoc networks.
Bluetooth devices can support scatternets of multiple smaller non-synchronized networks(piconets). 8 Slaves or nodes in a baisc master slave piconet set up.
Wake up Time: When ZigBee node is powered down, it can wake up and get a packet in around 15 msec whereas a Bluetooth device would take around 3sec to wake up and respond.

6. Device architecture/Protocol architecture
IEEE
Specification of the lower two layers of the protocol(physical and data link layer).
ZigBee Alliance aims to provide the upper layers of the protocol stack (from network to the application layer)
physical Layer:
Contains the radio frequency (RF) transceiver along with its low-level control mechanism
MAC sub-layer
Provides access to the physical channel for all types of transfer.
Upper Layers
Network layer provides network configuration, manipulation, and message routing
Application layer provides the intended function of a device.

7. Physical Layer
It operates on one of three possible unlicensed frequency bands.
868.0–868.6 MHz: Europe, allows one communication channel (2003, 2006, 2011)
902–928 MHz: North America, up to ten channels (2003), extended to thirty (2006)
2400–2483.5 MHz: worldwide use, up to sixteen channels (2003, 2006)
There is a single channel between 868 and 868.6MHz, 10 channels between and 928.0MHz, and 16 channels between 2.4 and GHz

8. Physical layer
The standard offers two PHY options based on the frequency band.
Based on direct sequence spread spectrum (DSSS).
The data rate is 250kbps at 2.4GHz, 40kbps at 915MHz and 20kbps at 868MHz.
The higher data rate at 2.4GHz is attributed to a higher-order modulation scheme.
Higher rate means higher throughput.
Lower frequency provide longer range due to lower propagation losses resulting in a larger coverage area.