22-06-2010, 12:35 PM
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A ZIGBEE NETWORK BASED WIRELESS HEART MONITERING SYSTEM
Presented By:
B. Divya Chandrika
D. V. Sandeep Raju
P. Shirish Kumar
P. Sasikanth
What is ZigBee
Wireless networking technology.
IEEE 802.15.4 wireless protocol.
Radio environments in isolated locations.
IEEE IEEE 802 IEEE 802.15 IEEE 802.15.4
Zigbee Technology
The IEEE is the Institute of Electrical and Electronics Engineers. They are a non-profit organization dedicated to furthering technology involving electronics and electronic devices.
IEEE involved in network operations and technologies, including mid-sized networks and local networks. Group 15 deals specifically with wireless networking technologies.
For the last few years, we've witnessed a great expansion of remote control devices in our day-to-day life. Five years ago, infrared (IR) remotes for the television were the only such devices in our homes. Now I quickly run out of fingers as I count the devices and appliances I can control remotely in my house. This number will only increase as more devices are controlled or monitored from a distance.
Why so many remotes Right now, the more remotely controlled devices we install in our homes, the more remotes we accumulate. Devices such as TVs, garage door openers, and light and fan controls predominantly support one-way, point-to-point control. They're not interchangeable and they don't support more than one device. Because most remotely controlled devices are proprietary and not standardized among manufacturers, even those remotes used for the same function (like turning on and off lights) are not interchangeable with similar remotes from different manufacturers. In other words, you'll have as many separate remote control units as you have devices to control.
Some modern IR remotes enable you to control multiple devices by "learning" transmitting codes. But because the range for IR control is limited by line of sight, they're used predominantly for home entertainment control.
A HAN can solve both problems because it doesn't need line-of-sight communication and because a single remote (or other type of control unit) can command many devices.
ZigBeeâ„¢s low power consumption is rooted not in RF power, but in a sleep mode
specifically designed to accommodate battery powered devices. Any ZigBee-compliant
radio can switch automatically to sleep mode when itâ„¢s not transmitting, and remain
asleep until it needs to communicate again. For radios connected to battery-powered
devices, this results in extremely low duty cycles and very low average power
consumption
Low RF Power Application
A common example of ZigBee networking with low RF power is office lighting. In this
application, light switches containing battery-powered ZigBee radios turn lights on and
off by issuing commands to ZigBee radios in fluorescent tubes, with no wires between
switch and fixture (representing tremendous cost savings in eliminating electrical runs).
Button cell batteries in the light switches last for years, with the radio waking up and
using battery power only when flipped on or off to transmit the new state to the
fluorescent tubes (and going immediately back to sleep). As switches and light fixtures
are in close proximity, and ZigBee routers in the fluorescent tubes can relay commands
to other routers, the application would work well using ZigBee radios with only 1 mW RF
power.
If two network points are unable to communicate as intended, transmission is dynamically routed from the blocked FFD to another FFD with a clear path to the dataâ„¢s destination. This happens automatically, so that communications continue even when a page link fails unexpectedly. Dynamic routing can also extend the networkâ„¢s effective reach; when the distance between the base station and a remote node exceeds the devicesâ„¢ range, an intermediate node or nodes
can relay transmission, eliminating the need for separate repeaters.
The potential issue of latency
In any dynamic routing, each node-to-node hop introduces latency. With ZigBee, that latency is typically several milliseconds per hop, so that a multi-hop path can introduce tens of milliseconds of latency as data travels to its destination. Routing algorithms are typically designed to optimize the data path, but dynamic routing always introduces latency.
ZigBee Origin
¢ IEEE 802.15.4
¢ ZigBee ratified in 2004.
Need for ZigBee
In 2004 there was a need of a wireless network which is
cost-effective
supports low data rates
low power consumption
secure and reliable
Run for years
The framework for the application layer, which includes the application support sub-layer (APS), the ZigBee device objects (ZDO) and the manufacturer-defined application objects
Why the name ZigBee
Zig zag patterns - BEES
Invisible webs of Mesh network.
The name "ZigBee" is derived from the erratic zigging patterns many bees make between flowers when collecting pollen. This is suggestive of the invisible webs of connections existing in a fully wireless environment.
It has been suggested that the name evokes the haphazard paths that bees follow as they harvest pollen, similar to the way packets would move through a mesh network
Using communication system, whereby the bee dances in a zig-zag pattern, worker bee is able to share information such as the location, distance,
And direction of a newly discovered food source to her fellow colony members. Instinctively implementing the ZigBee Principle, bees around the world actively sustain productive itchiness and promote future generations of Colony members
WPAN
IEEE 802.15.4
Main features
Flexibility
Low cost
Very low power consumption
Low data rate
The main features of this standard are network flexibility, low cost, very low power consumption,
and low data rate in an adhoc self-organizing network among inexpensive fixed, portable and moving
devices.
Licences
Three license free bands
2.4 GHz
915 MHz for North America
868 MHz for Europe
At 2.4 GHZ
16 channels -data transfer of 250 kbps
At 915 MHz
10 channels -max 40 kbps transfer rate
At 868 MHz
1 channel -max 20 kbps transfer rate
ZigBee operates is one of three license free bands
2.4 GHz, 915 MHz for North America, and 868 MHz for Europe
At 2.4 GHZ, there are a total of 16 channels available with a maximum data transfer of 250 kbps
At 915 MHz: 10 channels for a max 40 kbps transfer rate
At 868 MHz: 1 channel for a max 20 kbps transfer rate
ZigBee incorporates a CSMA-CA protocol
This protocol that reduces the probability of interfering with other users and automatic retransmission of data ensures robustness.
By determining when to transmit, unnecessary clashes are avoided.
128-bit AES encryption “ Provides secure connections between devices
Support for multiple network topologies : star, peer-to-peer, mesh
Addressing space of up to 64 bit IEEE address devices
- Up to 65,535 nodes on a network
Optional guaranteed time slot for applications requiring low latency
Fully reliable hand-shaked protocol for transfer reliability
Range: 50m typical (5-500m based on environment)
Link quality indication
Clear channel assessment
Retries and acknowledgements
Support for guaranteed time slots and packet freshness
¢ 2.4GHz and 868/915 MHz dual PHY modes. This represents three license-free bands: 2.4-2.4835 GHz, 868-870 MHz and 902-928 MHz. The number of channels allotted to each frequency band is fixed at sixteen (numbered 11-26), one (numbered 0) and ten (numbered 1-10) respectively. The higher frequency band is applicable worldwide, and the lower band in the areas of North America, Europe, Australia and New Zealand .
¢ Low power consumption, with battery life ranging from months to years. Considering the number of devices with remotes in use at present, it is easy to see that more numbers of batteries need to be provisioned every so often, entailing regular (as well as timely), recurring expenditure. In the ZigBee standard, longer battery life is achievable by either of two means: continuous network connection and slow but sure battery drain, or intermittent connection and even slower battery drain.
¢ Maximum data rates allowed for each of these frequency bands are fixed as 250 kbps @2.4 GHz, 40 kbps @ 915 MHz, and 20 kbps @868 MHz.
¢ High throughput and low latency for low duty-cycle applications (<0.1%)
¢ Channel access using Carrier Sense Multiple Access with Collision Avoidance (CSMA - CA)
¢ Addressing space of up to 64 bit IEEE address devices, 65,535 networks
¢ 50m typical range
¢ Fully reliable hand-shaked data transfer protocol.
¢ Different topologies as illustrated below: star, peer-to-peer, mesh
Why ZigBee
Long range (10-100 meters)
Long Battery Life
Secure communication
Low complexity
ZIGBEE TOPOLOGY
ZigBee Supports 3 Topologies
Star topology
Peer to Peer topology
Cluster Tree or Mesh Topology
Depending on the application requirements, the LR-WPAN may operate in either of two topologies: the star
topology or the peer-to-peer topology. Both are shown in Figure 1. In the star topology the communication is
established between devices and a single central controller, called the PAN coordinator. A device typically
has some associated application and is either the initiation point or the termination point for network
communications. A PAN coordinator may also have a specific application, but it can be used to initiate,
terminate, or route communication around the network. The PAN coordinator is the primary controller of the
PAN. All devices operating on a network of either topology shall have unique 64 bit extended addresses.
This address can be used for direct communication within the PAN, or it can be exchanged for a short
address allocated by the PAN coordinator when the device associates. The PAN coordinator may be mains
powered, while the devices will most likely be battery powered. Applications that benefit from a star
topology include home automation, personal computer (PC) peripherals, toys and games, and personal
health care.
The peer-to-peer topology also has a PAN coordinator; however, it differs from the star topology in that any
device can communicate with any other device as long as they are in range of one another. Peer-to-peer
topology allows more complex network formations to be implemented, such as mesh networking topology.
Applications such as industrial control and monitoring, wireless sensor networks, asset and inventory
tracking, intelligent agriculture, and security would benefit from such a network topology. A peer-to-peer
network can be ad hoc, self-organizing and self-healing. It may also allow multiple hops to route messages
from any device to any other device on the network. Such functions can be added at the network layer, but
are not part of this standard.
The basic structure of a star network can be seen in Figure 1. After an FFD is activated for the first time, it
may establish its own network and become the PAN coordinator. All star networks operate independently
from all other star networks currently in operation. This is achieved by choosing a PAN identifier, which is
not currently used by any other network within the radio sphere of influence. Once the PAN identifier is
chosen, the PAN coordinator can allow other devices to join its network; both FFDs and RFDs may join the
network.
Network Layer AND Application Layer
ZigBee architecture includes
The ZigBee Device Object (ZDO)
User-Defined Application Profile
The Application Support (APS)
PHY LAYER
The physical radio channel.
IEEE 802.15.4 PHY physical layer
Activation and deactivation of the radio transceiver,
Energy detection (ED),
Link quality indication (LQI),
Clear channel assessment (CCA),
Channel selection.
MAC LAYER
Enables the transmission across the PHY data service.
The features of MAC sub layer are
Beacon Management,
CSMA-CA Mechanism,
GTS management,
Acknowledged frame delivery.
DATA TRANSFER
Packets
Packet maximum size of 128 bytes, allowing for a maximum payload of 104 bytes.
Maximum data transfer rate of 250 kbps for a range of up to 100 meters
Time synchronization
DATA TRANSFER
This data transfer transaction is the mechanism for transferring data from a coordinator to a device.
When the coordinator wishes to transfer data to a device in a beacon-enabled network, it indicates in the
network beacon that the data message is pending. The device periodically listens to the network beacon and,
if a message is pending, transmits a MAC command requesting the data, using slotted CSMA-CA. The
coordinator acknowledges the successful reception of the data request by transmitting an optional
acknowledgment frame. The pending data frame is then sent using slotted CSMA-CA. The device
acknowledges the successful reception of the data by transmitting an acknowledgment frame. The
transaction is now complete. Upon receiving the acknowledgement, the message is removed from the list of
pending messages in the beacon
When a coordinator wishes to transfer data to a device in a nonbeacon-enabled network, it stores the data for
the appropriate device to make contact and request the data. A device may make contact by transmitting a
MAC command requesting the data, using unslotted CSMA-CA, to its coordinator at an application-defined
rate. The coordinator acknowledges the successful reception of the data request by transmitting an
acknowledgment frame. If data are pending, the coordinator transmits the data frame, using unslotted
CSMA-CA, to the device. If data are not pending, the coordinator transmits a data frame with a zero-length
payload to indicate that no data were pending. The device acknowledges the successful reception of the data
by transmitting an acknowledgment frame.
Reliability and Fail Safe measures
Detect if any node in the ZigBee has failed.
Computer receives periodic data.
Software running on the computer attached to zigbee coordinator.
Can estimate life time of the zigbee nodes.
Conclusion
Remote monitoring capability of existing health care system.
Feasibility
Secure
Robust
Low-power consuming.
Operate on multiple channels
