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Figure 24 The Hidden Station Problem
station" problem. Both station A and station B are within range of the
Access Point RLM however, station B cannot "hear" station A, therefore
station A is a "hidden station" for station B.
When station B starts to communicate with the Radio Link Module, it might
not notice that station A is already using the wireless medium. When station
A and station B send messages at the same time, they might collide when
arriving simultaneously at the Access Point RLM. The collision will most
certainly result in a loss of messages for both stations.
In situations as pictured
medium reservation may provide a solution to prevent message collisions by
handing over transmission control to the Access Point RLM.
Troubleshooting a "hidden station" problem usually provides the best results
when it is performed on the suspected stations that suffer from errors as a
result of the "hidden station" problem.
When configuring the PC Card CP 1515 parameters of an individual station
you can enable the RTS/CTS Medium Reservation parameter:
•
To enable RTS/CTS Medium Reservation parameter, choose
tab and enable
You can enable RTS/CTS Medium Reservation on individual stations, i.e. the
setting of this parameter does not have to be the same for all SIMATIC NET
IWL equipped devices in your network.
Industrial Ethernet Wireless LAN RLM Manager, CP 1515 Manager
C79000-G8976-C171-01
illustrates an example of the "hidden
Figure 24 The Hidden Station
in the CP 1515 Manager, select the
Problem, RTS/CTS
.
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