Zigbee

By:

Adel Al-Ghamdi Yousef Al-Rasheedi

For:

214919 215715 Dr. Adnan Al-Andalusi

OUTLINES

       What is Zigbee?

Why is Zigbee needed?

Components of Zigbee Network Topologies LR-WPAN Architecture Zigbee vs. Bluetooth Zigbee Applications

What is Zigbee?

 Zigbee technology is a low data rate, low power consumption, low cost, wireless networking protocol targeted towards automation and remote control applications.

 It is a result of the joined forces of Zigbee Alliance and IEEE.

 Zigbee belongs to IEEE 802.15.4 standard.

Why is Zigbee needed?

 There are a verity of standards that address mid to high data rates for voice, PC LANs, video, etc. However, up till now there hasn’t been a wireless network standard that meets the unique needs of sensors and control devices .  Sensors and controls don’t need high bandwidth but they do need

low latency

and very

low energy consumption

for long battery live.

The 802 Wireless Space

Types of Components

    Two types of devices used by Zigbee system: 1. Full- function device (FFD).

2. Reduced-function device (RFD).

The network shall include at least one FFD, operating as the PAN coordinator.

RFD is intended for applications that are extremely simple and does not need to send large amount of data.

FFD can talk to RFDs or FFDs while RFD can only talk to FFD.

Network Topologies

   

Star Topology:

the communication is established between devices and a single central controller, called the PAN coordinator.

The PAN coordinator may be main powered while the devices will most likely be battery powered.

Each start network chooses a PAN identifier, which is not currently used by any other network within the radio sphere of influence. This allows each star network to operate independently.

Applications that benefit from this topology include home automation, personal computer (PC) peripherals, toys and games.

  It can be ad hoc, self-organizing and self-healing network.



Peer-to-peer (Mesh) topology:

has also one PAN coordinator. In contrast to star topology, any device can communicate with any other device as long as they are in range of one another.

Applications such as industrial control and monitoring, and wireless sensor networks.



Cluster-tree topology:

is a special case of a peer-to-peer network in which most devices are FFDs and an RFD may connect to a cluster-tree network as a leave node at the end of a branch.

 Any of the FFD can act as a coordinator and provide synchronization services to other devices and coordinators. Only one of these coordinators however is the PAN coordinator.

LR-WPAN Architecture

 The device comprises:  IEEE 802.15.4 PHY  IEEE 802.15.4 MAC   IEEE 802.15.4 NWK Application Layer  An IEEE 802.2 logical link control (LLC) can access the MAC sublayer through the service specific convergence sublayer (SSCS).

IEEE 802.15.4 PHY

PHY (MHz) Freq band (MHz) Modulation Bit rate (Kbps)

868 868-868.6

BPSK 20 915 2450 902-928 BPSK 2400-2483.5

O-QPSK 40 250

IEEE 802.15.4 MAC

 Zigbee incorporates a CSMA-CA protocol  This protocol reduces the probability of interfering with other users and automatic retransmission of data ensures robustness.

 By determining when to transmit, unnecessary clashes are avoided.

Data Transfer

    Information in a Zigbee network is transferred in packets Each packet has a maximum size of 128 bytes, allowing for a maximum payload of 104 bytes.

The Zigbee specification supports a maximum data transfer rate of 250 kbps for a range of up to 30 meters.

For priority messages, a guaranteed time slot mechanism has been incorporated . This allows high priority messages to be sent across the network as rapidly as possible.

IEEE 802.15.4 NWK

 The responsibilities of the Zigbee NWK layer include: 

Starting a network:

The ability to successfully establish a new network. 

Joining and leaving a network

: The ability to gain membership (join) or relinquish membership (leave) a network.



Configuring a new device:

The ability to sufficiently configure the stack for operation as required.

Addressing:

The ability of a Zigbee coordinator to assign addresses to devices joining the network.

IEEE 802.15.4 NWK



Security:

applying security to outgoing frames and removing security to terminating frames 

Routing:

routing frames to their intended destinations.

Zigbee Routing

  Hierarchical routing strategy Uses two strategies  AODV: Ad Hoc On Demand Distance Vector  Cluster-Tree Algorithm

Ad Hoc On Demand Distance Vector

  Pure on-demand route acquisition algorithm   Defines path of message from source to sink Nodes that are not on active path don’t maintain routing information or exchange routing tables Primary objectives   Broadcast discovery packets only when necessary Distinguish between local connectivity management and general topology management  Disseminate information about local connectivity changes to neighboring mobile nodes

Cluster-Tree Algorithm

  Forms single/multi cluster tree networks Forms self-organizing network with redundancy and self-repair capabilities  Nodes select cluster heads and form clusters in a self-organized manner.

 Self-developed clusters then connect to each other through a designated Device (DD)

Zigbee vs. Bluetooth

 Zigbee looks rather like Bluetooth but is simpler, has a lower data rate and spends most of its time snoozing  a node on a Zigbee network should be able to run for six months to two years on just two AA batteries.

 The operational range of Zigbee is 10-75m compared to 10m for Bluetooth (without a power amplifier).

Zigbee vs. Bluetooth

   Zigbee devices talk via small data packet, while Bluetooth's protocol is more complex since it is geared towards handling voice, images and file transfers.

Zigbee allows up to 254 nodes, while Bluetooth only allows up to 8 slave nodes.

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.

Zigbee Applications

security HVAC lighting control access control

BUILDING AUTOMATION CONSUMER ELECTRONICS

TV VCR DVD/CD remote patient monitoring fitness monitoring

PERSONAL HEALTH CARE

asset mgt process control environmental energy mgt

INDUSTRIAL CONTROL ZigBee

Wireless Control that Simply Works

PC & PERIPHERALS

mouse keyboard joystick

RESIDENTIAL/ LIGHT COMMERCIAL CONTROL

security HVAC lighting control access control lawn & garden irrigation

More Information

ZigBee Alliance Web Site http://www.ZigBee.org

IEEE 802.15 Web Site http://www.ieee802.org/15