User guide

45 Mbps Backhaul User Guide
Issue 3, December 2004 Page 28 of 113
5.7.9 Aligning the ODUs
The following is a description of the steps taken to establish a radio link between the two units forming the
bridge and align the units for the best signal strength.
The 45 Mbps Backhaul uses audible tones during installation to assist the installer with alignment. The installer
should adjust the alignment of the ODU in both azimuth and elevation until highest pitch tone is achieved
3
. The
tones and their meanings are as follows:
State Name
Tone
Description
State Description
Pitch
Indication
(Higher pitch =
higher power)
Band Scan
Regular beep
Executing band scan
N/A
Scanning
Slow broken
tone
Not demodulating the wanted signal
Rx Power
Synchronized
Fast broken tone
Demodulating the wanted signal
Rx Power
Registered
Solid tone
Both Master and Slave units
exchanging Radio layer MAC
management messages
Rx Power
Table 3 Audio indications from the ODU
The term ‘wanted signal’ refers to that of the peer unit being installed.
In each of the states detailed above the unit should be aligned to give the highest pitch tone. It should be noted
that if, when in the Synchronized or Registered state the tone varies wildly, you may be suffering from
interference or a fast fading link. Installing in this situation may not give a reliable link. The cause of the
problem should be investigated.
For the ease of alignment both Master and Slave units use the install tones in the same way but with some small
behavioral differences. This allows the installer to install the Slave unit first and carry out the initial alignment
with the Master unit if desired. However due to the Behavioral differences of Master and Slave units it is
recommended that the Master unit is installed first and the initial alignment carried out at the Slave unit.
The following behavior should be noted:
When first started up and from time to time the Master unit will carry out a band scan to determine which
channels are not in use. During this time, between 10 and 15 seconds, the Master unit will not transmit and as a
consequence of this neither will the Slave unit. During this time the installation tone on the master unit will drop
back to the band scan state and the Slave unit will drop back to Scanning state with the pitch of the tone set be
the background noise level. Alignment of the unit should cease during this time.
The master unit can take between 10 seconds in 0-5km mode to 60 seconds in 0-200km mode to determine the
range of the link being installed
4
. The Master unit will remain in the Scanning state until the range of the link
3
The pitch of the alignment tone is proportional to the power of the 5.8 GHz wireless signals. The
best results are usually achieved by making small incremental movement in angular alignment.