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Entry type: FAQ Entry ID: 92649989, Entry date: 06/11/2014

How do you link a PNIO device to a PNIO controller via WLAN and iPCF?

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In a PROFINET network, the iPCF (industrial Point Coordination Function) is available for reliable data communication via Industrial Wireless LAN (IWLAN), even over clearances. iPCF is configured in the access point and IWLAN client.

In a PROFINET network, the iPCF (industrial Point Coordination Function) is available for reliable data communication via Industrial Wireless LAN (IWLAN), even over clearances. Unlike the standard IEEE 802.11, the Access Point (AP) controls the communication of the IWLAN clients, which avoids collisions and the data traffic is deterministic. In addition, the iPCF permits very rapid change of radio cell with a beacon interval of under 50ms.
This FAQ response describes how to set up an AP and a IWLAN client with iPCF for deterministic data exchange between an IO controller and an IO device.

Set up the Access Point as follows.

  1. Log on to the AP via the WBM (Web Based Management). Here you assign a password that is different from the default password.
  2. For the basic configuration you navigate through the Basic Wizard provided.
    Choose "AP" as Device Mode and confirm with "Next".

    Fig. 1 
  3. Select the country in which the AP is to be operated and specify a system name to identify your AP.
    Click "Next" to confirm your selection.

    There are special APs with their own article numbers for operation in the USA.

  4. Assign your desired IP address to the AP or choose to have the IP address assigned by a DHCP server.
    Confirm the entries with "Next".
  5. Under "Management Interfaces" you select the protocols through which management of the AP is to be made possible.
    Click "Next" to confirm your selection.

    For safety reasons we recommend switching off any protocols not used.

  6. Specify the antenna you have slotted. Also inform the AP the length of the cable you are using and its attenuation. This last bit of information does not influence the behavior of the AP, but is merely used as information for planning and implementing a plant.
    If you do not use all the available antennas per interface, then select "Not used (Connect 50 Ohm Termination)" after the last antenna.
    Confirm the entries with "Next".

    Fig. 2
    If you use more then one antenna, set the second or all other antenna to "RX".

  7. In the "Radio" tab you set the frequencies and the standard the AP is to use.
    In Fig. 03, the 5GHz frequency band is selected, because that is where usually less channels are already being used. 802.11a is selected to be compatible also with WLAN clients which do not support the 802.11n standard. The DFS option permits use of the upper channels of the 5 GHz frequency band. This is not recommended when using iPCF, because you might encounter radar signal interference.
    Confirm the entries with "Next".

    Fig. 3 

  8. In the next tab you can choose which channel the AP should occupy. Here you can also define the SSID of your network.
    Confirm the entries with "Next".

  9. In the "Security" tab you select "Open System" as the "Authentication Type". You cannot choose any other authentication type with iPCF to ensure the fastest possible roaming times.
    Confirm the entries with "Next".

  10. Click "Set Values" to apply the settings you have made.

  11. Select "Security > WLAN > Keys". Here you enter a password to encrypt your data traffic.
    Confirm with "Set Values".

    Fig. 4 

  12. Select "Security > WLAN > Basic" and enable "Encryption" and the type of cipher you want (AES cannot be chosen with 802.11n).

    Fig. 5 

  13. Select "iFeatures > iPCF". Enable "PNIO Support" to inform the clients of the "iPCF Cycle Time". Set "iPCF Cycle Time [ms]" to the refresh time of your IO devices.
    Confirm the entries with "Set Values".

    With IWLAN segments you need higher refresh times than with pure Ethernet cable segments. If you have a large number of clients on the AP, you must calculate 2ms per client (excluding roaming!). The roaming time increase proportionally with the number of channels to be scanned.

    Fig. 6

  14. Now you have set up iPCF on your Access Point.

Set up the client as follows.

  1. Perform steps 1 to 7 from the set up instructions of the Access Point. Set "Client" for "Device Mode" in step 2.
  2. In the "Client" you select the MAC Mode "Layer 2 Tunnel" to be able to connect up to 8 IO devices after your client. Disable the "Any SSID" option and specify the SSID of the AP.
    Confirm the entries with "Next".

    Fig. 7
  3. In the "Channels" tab you define which channels the client should scan. Here you select the channels that you have also specified in your AP.
  4. Perform steps 9 to 12 from the set up instructions of the Access Point.
  5. Enable the "Enable iPCF" option and confirm the entry with "Set Values".

    Fig. 8
  6. Now you have installed iPCF on your client. The client roams automatically to the Access Point as soon as it sees the AP.

    Go to "Information > WLAN > Available AP" to check when the client is connected with the AP (State: connected).

When configuring in STEP 7 you do not have to worry about the WLAN segment in the configuration. All you have to do is change the PNIO update times for the devices connected via the WLAN segment.

Hardware components used

FunctionName Article number
Access pointScalance W788 RJ456GK5788-2FC00-0AA0
ClientScalance W748 RJ456GK5748-1FC00-0AA0
Key PlugKEY PLUG W7806GK5907-8PA00
Key PlugKEY PLUG W7406GK5907-4PA00

Table 1

Further Information
With PROFINET IO via WLAN how do you set the update time and F-monitoring time in STEP 7 V5.x?
With PROFINET IO via WLAN how do you set the update time and F-monitoring time in the TIA Portal? 

Additional Keywords
iFeatures, iPCF MC, IWLAN, Clearance, Wireless

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