Enterasys Networks 802.11 - Manual (Page 134)

Testing Radio Communications Quality
6-4
A low signal level indicates that the client and the test partner may be too far apart or
there may be obstructions between them. If possible, remove the obstructions, move
the devices closer, or use the optional Range Extender antenna described in
“Range
Extender Antenna” on page 1-17 .
4. Check the Total Messages column. Data throughput efficiency is measured in
messages sent, lost, or received.
5. Divide the number of Messages Lost by the number of Messages Sent. The Messages
Sent number must be greater than 200.
Typically, the number of Messages Lost is less than 1 percent of the number of
Messages Sent. If this number increases to 5 percent, you may have communication
problems. If necessary, click the Reset button to observe only the current data
throughput.
If the SNR is low and the number of messages lost is high, the problem is likely due to a
poor communications quality. For example, the client and the test partner are too far apart
or the connection suffers from a source of noise interference.
If the SNR is adequate or good but there is a relatively large number of messages lost or
received after a retry, the problem might indicate:
•
A very busy network where many clients try to access the medium at the same time.
•
A microwave oven in close vicinity (7 to 10 feet) to the client or AP is causing short
bursts of interference. This noise might not be displayed by the noise level indicator,
but could still be forcing the clients to retransmit frames.
•
Another client is suffering from a poor communications quality and is consequently
sending many retransmissions.
•
Numerous frame collisions are occurring due to a hidden station problem.
Run the RoamAbout Client Utility link test from multiple clients to determine if the
problem is local (one client only) or experienced by all clients.
If all clients suffer from poor data throughput efficiency despite a good SNR value, the
traffic load could be caused by the following:
•
Many wireless clients are trying to communicate simultaneously.
•
Clients are deferring data transmissions to avoid frame collisions.
•
Clients are retransmitting frames repeatedly because initial transmissions failed, which
can be due to frame collisions.