Ipcf / Ipcf-Ht / Ipcf-Mc - Siemens SIMATIC NET SCALANCE W780 Series Configuration Manual

4.7

iPCF / iPCF-HT / iPCF-MC

The wireless range of an IWLAN system can be expanded by using multiple access points. If
a client moves from the area covered by one access point to the area covered by another
access point, the wireless link is maintained after a short interruption (roaming).
If very fast update times are required, for example for PROFINET communication, access
points and client modules need to be used that use the proprietary methods iPCF / iPCF-HT
or iPCF-MC for fast roaming and deterministic data traffic.
iPCF / iPCF-HT / iPCF-MC can only be operated alone. A combination with each other is not
possible, e.g. iPCF with iPCF-HT or iPCF-MC.
How it works
iPCF
With iPCF the access point checks all nodes in the wireless cell cyclically. At the same time,
the scan includes the downlink traffic for this node. In the reply, the node sends the uplink
data. The access point scans a new node at least every 5 ms.
The scan of a node is seen by all other nodes in the cell. This allows a client to detect the
quality of the wireless link to the access point even when it is not communicating with the
access point itself. If the client does not receive any frames from the access point for a
certain time, it starts to search for a new access point.
In iPCF mode, both the search for a new access point and the registration with this access
point have been optimized in terms of time. Handover times significantly below 50 ms are
achieved.
The "Legacy Free (iPCF-LF)" setting is available to prevent the performance from being
slowed down by the IEEE 802.11 a/b/g device generation. When enabled, only the devices
that communicate with the IEEE 802.11n standard and have the "Legacy Free (iPCF-LF)"
setting enabled are accepted. WLAN mode IEEE 802.11n need not be enabled for this,
however.
Stable PROFINET communication is only possible when a WLAN client is in a wireless cell
with more than 60 % or -65 dBm signal strength at all times. This can be checked by
activating and deactivating the various wireless cells.
This does not mean that the client needs to change when there is a signal strength < 60 %
(< -65 dBm). Make sure that access points are available with adequate signal strength.
You configure iPCF in "iFeatures > iPCF > iPCF (Page 404)".
iPCF-HT
If a higher data throughput is required for iPCF, iPCF-HT is used. With this you can, for
example, alongside PROFINET also transfer video data. This is achieved by more effective
transfer of data packets using frame-bursting (A-MPDU). The individual data packets are
grouped together that are intended for the same receiver station (client) and that have the
same prioritization.
You configure iPCF-HT in "iFeatures > iPCF > iPCF-HT (Page 408)".
iPCF-MC
For freely moving nodes that communicate independently of a RCoax cable or directional
antennas, iPCF-MC should be used. With iPCF-MC, the client also searches for potentially
SCALANCE W780/W740 to IEEE 802.11n Web Based Management
Configuration Manual, 08/2018, C79000-G8976-C267-13
Technical basics
4.7 iPCF / iPCF-HT / iPCF-MC
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