Here is the bit from the manual about aligning the CPE using the alignment 
meter. Please let me know what is missing and why RSSI is needed in addition.

- Patrick

>From section 3.2, page 49 (of 277) of the VL System Manual, July 2006

Aligning the Subscriber Unit Antenna

The SNR bar display is located on the bottom panel of the outdoor unit. The ten 
LEDs indicate the quality of the received signal. The higher the number of 
green LEDs indicating On, the higher the quality of the received signal. 

This section describes how to align the Subscriber Unit antenna using the SNR 
bar display.

Antenna alignment using the SNR bar display is possible only after the 
Subscriber Unit is associated with an Access Unit. The associated Access Unit 
must be operational and the basic Subscriber Unit parameters must be correctly 
configured. Otherwise, the unit will not be able to synchronize with the Access 
Unit. As the SNR measurement is performed on received frames, its results are 
meaningless unless the Subscriber Unit is associated with an Access Unit.

To align the Subscriber Unit antenna:
1 Align the antenna by pointing it in the general direction of the Base Station.
2 Verify that the power indication of the unit is On.
3 Verify that the W-LINK LED of the ODU is On, indicating that the unit is 
associated with an Access Unit. If the W-LINK LED is Off, check that the ESSID 
and Frequency parameters are correctly configured. If the SU is still not 
associated with the AU, increase the transmit power level to its maximum value. 
If the unit is still not associated with the AU, improve the quality of the 
link by changing the direction of the antenna or by placing the antenna at a 
higher or alternate location.
4 Rotate the antenna until the maximum SNR reading is achieved, where at least 
1 green LED is on. If you encounter prolonged difficulty in illuminating the 
minimum required number of green LEDs, try to improve the reception quality by 
placing the antenna at a higher point or in an alternate location.
5 Ensure that the front of the antenna is always facing the Base Station.
However, in certain conditions, such as when the line of site to the Base
Station is hampered, better reception may be achieved using a reflected signal. 
In this case, the antenna is not always directed toward the Base Station.
6 Secure the unit firmly to the pole.

In some cases, the antenna may need to be tilted to ensure that the level at 
which the SU receives transmissions from the AU (and vice versa) is not too 
high. As a rule of thumb, if the SU is located at a distance of less than 300 
meters from the AU, it is recommended to up-tilt the antenna by approximately 
10° to 15°. To guarantee a safety margin from the saturation level (received 
signal of -40 dBm at the antenna port), the SNR should not be higher than 50 
dB. The orange LED of the SNR bar indicates that the SNR is higher than 50 dB.

Patrick Leary
AVP WISP Markets
Alvarion, Inc.
o: 650.314.2628
c: 760.580.0080
Vonage: 650.641.1243

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