Siemens CP 1515 User Manual
Page 147
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Industrial Ethernet Wireless LAN RLM Manager, CP 1515 Manager
C79000-G8976-C171-01
147
may perceive that wireless stations show a degrading performance,
perceived as long network response times when communicating via the
network.
Where poor performance is typically caused by poor radio link quality
(identified by a poor signal to noise ratio (SNR)), the scenario described
above may also be perceived in areas where:
•
Site monitor measurements show an excellent wireless coverage by at
least two Access Points RLMs or more on every location.
•
Link test measurements at such locations may show:
—
An excellent SNR for communications between wireless stations
and the Radio Link Module.
—
A large number of messages transmitted at lower rates.
In this type of situations the disappointing network performance might be
caused by the busy wireless traffic in that area, where the CSMA/CA
protocol causes the wireless stations to defer transmissions to often for
either:
•
Heavy data traffic by other stations in the same wireless cell
•
Traffic from stations in neighboring cells, where stations in a location
where wireless cells overlap one another seem to suffer more than the
other stations.
The last example would typically occur only in networks where all Access
Points RLMs have been configured to operate at the same frequency, or at
frequencies with an insufficient channel separation (see
).