GE MDS entraNET 900, Техническое руководство

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162 MDS entraNET Technical Manual 05-4055A01, Rev. E
6.5.2 Aiming Directive Antennas for Maximum RSSI
The wireless network integrity depends, in a large part, on stable radio
signal levels being received at each end of a data link. In general, signal
levels stronger than –90 dBm provide the basis for reliable
communication that includes a 15 dB fade margin. As the distance
between the AP and Remotes increases, the influence of terrain, foliage,
and man-made obstructions become more influential, and the use of
directional antennas at remote locations becomes necessary. Directional
antennas usually require some fine-tuning of their bearing to optimize
the received signal strength. The transceiver has a built-in received
signal strength indicator (RSSI) that you can use to tell when the antenna
is in a position that provides the optimum received signal.
RSSI measurements and Wireless Packet Statistics are based on multiple
samples over a period of several seconds. The average of these
measurements is displayed by the entraNET MS.
The measurement and antenna alignment process usually takes 10 or
more minutes at each transceiver.
The path to the Management System Menu item is shown in bold text
below each step of the procedure.
Procedure
1. Verify that the Remote is associated with an AP radio. Observe the
condition of the
LINK
LED.
LINK LED = on or blinking
This indicates that you have an adequate signal level for the
measurements, and it is safe to proceed.
2. View and record the
Radio Retries
and
No Ack
counts on the Radio
Packet Statistics Screen ( Figure 3-45 on Page 81 ). This information
will be used later.
3. Clear the
Radio Statistics
history.
4. Read the RSSI level at the Remote
(RADIO RSSI=).
5. Optimize the RSSI by slowly adjusting the direction of the antenna
and watching for a peak in received signal strength. Get the RSSI
indication several times after making each adjustment, so that the
RSSI accurately reflects any change in the link signal strength. The
higher the indication (less negative), the stronger the signal level
(that is, –60 is better than –70).