ZigBee bridges and gateways for building large monitoring and control networks

1
"ZigBee bridges and gateways for building large
monitoring and control networks"

• SangKil Lee / u-IT System Integrator
• Representative of Institute of Network
  Technologies, Russia
• infoland_at_paran.com
• http//www.mediamob.co.kr/infoland/

2
Why bridges?

• ZigBee networks often span across several rooms
  or buildings.
• Connecting them all with low-power 2.4 GHz radio
  links only may be impractical or impossible.
• Bridges allow for increasing the distance between
  the nodes, bypassing walls and obstacles and
  eliminating black spots.

3
How do they work?

• The bridges look as normal Zigbee routers from
  the wireless network point of view.
• At same time, they encapsulate some of data
  packets traveling across the wireless network
  into IP packets and forward them across different
  media Ethernet or powerline.
• Another bridge located close to the destination
  node of the ZigBee packet extracts it from the
  corresponding IP packet and transmits it by
  radio.

4
ZigBee-over-Ethernet bridge

• Connects wireless segments using UDP/IP over
  10/100 Base-T Ethernet encapsulation.
• Work with all IP routers, including DSL and cable
  routers, home and office internet access points.
• Wall or shelf mountable.
• Supports Power over Ethernet as a power source.
• Serves ZigBee networks of any size due to the
  powerful AT91RM9200 CPU and 8MB RAM
• Software upgradeable to support the latest
  versions of the ZigBee standard.

5
ZigBee-over-powerline bridge

• Transmits data over powerline according to the
  HomePlug v1.0 standard at rates up to 14 Mbbs.
• Requires no extra wiring
• Typical length of a powerline hop over 150m.
• Supports consecutive powerline hops, a chain of
  bridges allow for passing data over many hundreds
  of meters via powerline.
• Wall socket mountable.

6
Both products use the ZigBee stack implementation
developed by INT Russia

• Bridges in conjunction with software gateways
  from a cheap and powerful solution for data
  exchange between the ZigBee devices and the
  corporate IT environment.

7
Why gateways?

• In the corporate environment, the benefit from
  ZigBee network is the greatest when there is a
  bidirectional timely data exchange between the IT
  infrastructure and the wireless devices.
• In the industrial automation area, real-time data
  are typically handled by SCADA software. The
  MODBUS/TCP to ZigBee gateway allows for
  convenient data exchange of ZigBee devices with
  majority of SCADA available on the market.
• Web services, WSDL and SOAP are lingua franca of
  todays corporate IT. Both J2EE and .Net natively
  support writing clients that access Web service
  all major platforms like SAP offer convenient
  data exchange use them. The ZigBee to Web
  services gateway allows the applications to read
  data from the ZigBee sensors and issue commands
  to the ZigBee actuators.

8
How do they work?

• The ZigBee gateway from INT are implemented in
  software and run under Windows or Linux.
• The computer running a gateway must have access
  to an IP network. At least one ZigBee bridge is
  required for operation.
• The protocol encapsulation scheme for Web
  services is presented below the one for
  MODBUS/TCP is simular.

9
ZigBee to Web Services gateway

• The software works as Apache server module using
  Axis C. One Server can work with multiple
  bridges, thus reducing the cost.

APL NWK UDP/IP Ethernet
APL NWK MAC 802.15.4 PHY 802.15.4
SOAP HTTP TCP/IP
ZigBee to Web Services Gateway
ZigBee Over Ethernet Bridge
Web Services Client
SOAP
SOAP
ZigBee
ZigBee nodes
10
ZigBee to MODBUS/TCP gateway (for SCADA)

• The OPC server used with SCADA must support
  MODBUS/TCP protocol for the gateway to work.
• reads and sets attribute values of ZigBee
  devices.
• caches the values to avoid flooding the ZigBee
  network with too frequent requests and draining
  the device batteries
• allows for flexible mapping of ZigBee devices and
  attributes on OPC tags.