Trouble Shooting Guide

Axxcelera Broadband
Troubleshooting-Installing an RF link - 34 - Issue: 5.3.x
Rev 2
11 Modem mmse
The modem mmse command measures the modem’s mean-squared-error (MSE) for each burst, which can
be used to determine the quality of the signal being received.
The mean squared error indicates how closely the received data coincides with the four QPSK constellation
points, the expected data values. A high MSE indicates that the received signal quality is poor, either
because there is noise/interference on the signal, or because the signal level is incorrect.
AP/SU Modem mmse
The default “hmm modem mmse” command measures the mean-squared-error over 1000 bursts of received
data. It reports the average mean-squared-error, and reports the number of bursts where the MSE exceeded
50.
192.168.3.254 hmm> modem mmse
running please wait
0 out of 1000 mse's > threshold 50
mse average 15
11.1.1 n out of 1000 mse’s > threshold 50
Number of samples n where the modem reported an MSE greater than 50. On a good link this should be 0.
The more samples over 50 the worse the link is.
11.1.2 mse average
This is the average of the 1000 MSE samples taken from the modem. A link with a low average MSE, but
a high number with MSE over 50 may indicate the presence of a bursty interferer (i.e. another SU). A high
average MSE and a high number with MSE over 50 may indicate a power problem, or the presence of a
fairly permanent interferer (i.e. another AP).
The “hmm modem mmse” command can be used to show problems on individual downlinks (when used on
individual SUs), but only shows problems on some or all of the uplinks (when used on the AP). The
command only works properly on an AP if there is a lot of upstream traffic (1 upstream burst per 10ms).
Individual uplinks can be tested if traffic is suspended from all but one SU, and the SU under test is made
to transmit a lot of upstream traffic (i.e. by sending a stream of 100 pings/second to the SU).
The MSE measurements are meaningless if made on an SU that has not locked to an AP, or on an AP that
is not receiving data from an SU.
Status Average Value Samples over 50
Good <20 0
Marginal 20-35 1-30
Poor 35-50 30-50
Bad >50 >50