Trouble Shooting Guide

Axxcelera Broadband
Troubleshooting-Installing an RF link - 39 - Issue: 5.3.x
Rev 2
14 Modem msreg 6 1
The modem msreg 6 1 command will display the RX digital AGC level. This is a fine gain adjustment. It
is the only dynamic gain adjustment on APs. SUs also have a course gain adjustment, the Radio AGC,
which adjusts the gain over a wide range.
On SUs the Rx digital AGC does not assist in debugging, because of the presence of the Radio AGC.
However, for APs it indicates if the received signal is too strong or too weak.
AP Modem msreg 6 1
The signal from all SUs should be about –74dBm on arrival at the AP receiver.
If the signal is too strong then the gain of the digital AGC drops. If the signal is too weak then the gain of
the digital AGC increases. The digital AGC is fast-acting and is reset at the end of each burst to its starting
point of maximum gain (corresponding to a register value of 127). As the signal is received, the gain of the
digital AGC drops whenever the signal level is above the correct level.
When the received signal level is about –74dBm the digital AGC drops from 127 to an average range of 30-
50. If the signal level is too strong the digital AGC may drop to its lowest gain (corresponding to a register
value of 21). Readings of 21 indicate that the receiver is overloaded. If the signal level is too weak then
the digital AGC will not drop as far as expected, and it may even remain at its starting position of 127.
192.168.100.200 hmm> modem msreg 6 1
001: [0x06] 0x33 51
Average : 51.0
Status Average value
Bad 21
Marginal 22-25
Good 25-55
Marginal 55-70
Bad >70
Values for the Rx digital AGC can range from 21 to 127, and should be 25-55 for typical AP receiver.
The command only works properly on an AP if there is upstream traffic (one burst per reading of msreg 6).
Individual uplinks can be tested if traffic is suspended from all but one SU, and the SU under test is made
to transmit upstream traffic (i.e. by sending a stream of pings/second to the SU).
The digital AGC measurements are meaningless if the AP is not receiving data from an SU.