Siemens CP 1515 - Manual (Page 133)

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Industrial Ethernet Wireless LAN RLM Manager, CP 1515 Manager
C79000-G8976-C171-01
133
Figure 24 The Hidden Station Problem illustrates an example of the “hidden
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 Figure 24 The Hidden Station Problem , RTS/CTS
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
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in the CP 1515 Manager, select the
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tab and enable
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.
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.