Siemens CP 1515 - Manual (Page 136)

(OLPLQDWLQJ 5HGXQGDQW 7UDIILF
136 Industrial Ethernet Wireless LAN RLM Manager, CP 1515 Manager
C79000-G8976-C171-01
Since all stations connected to the Access Point RLM are typically
within range of that Radio Link Module, they should be able to
sense whenever the RLM is using the medium to transmit
messages via the wireless medium.
Enabling RTS/CTS medium reservation on the RLM would require
the Access Point RLM to ask for a CTS for every message that it
wishes to forward to stations within its range, even if it is forwarding
traffic between stations that belong to the same wireless cell.
This might cause redundant network overhead that could negatively
affect the throughput performance instead of providing a remedy.
If you insist on enabling RTS/CTS medium reservation on the Access Point
RLM, you will notice that the configuration of this option for Access Points
RLMs is slightly different from that of wireless stations.
The Access Points RLMs allow you to customize the sensitivity of the RTS/
CTS mechanism. By entering a user-defined frame length value in the
576
&76 0HGLXP 5HVHUYDWLRQ 7KUHVKROG
field (in the edit mode, select
,QWHUIDFH
tab, then click the
$GYDQFHG
button), you can influence when
the Access Point RLM should apply the RTS/CTS mechanism. For example:
• When a message is shorter than the RTS/CTS medium reservation
threshold, the Access Point RLM will not initiate an RTS to the
addressed station, but use the CSMA/CA protocol: i.e. it will
immediately transmit the message when it senses that the medium is
free.
• When the length of a message exceeds the RTS/CTS medium
reservation threshold, the Access Point RLM will first send an RTS to the
addressed station and defer transmission until the addressed station has
responded with a CTS message.