Performs ranging and displays measurement performance data on the upstream
and downstream signal level, downstream modulation error ratio (MER) (or
EVM, as configured), and the estimated downstream bit error rate (BER)
before and after forward error correction (FEC). The range measurement
data can be viewed in relation to user-configured limits to determine
the Pass/Fail status of the DOCSIS channel.
Measurement Data
The RANGE SUMMARY screen contains a summary of all of the DOCSIS Ranging
measurement data. This measurement data is captured during the DOCSIS Ranging
test process. There will be a continuous update of displayed values when the
test is complete. To perform the test again, press the VIEW softkey,
use the arrow keys to select Restart, and press ENTER.
Only valid measurements and parameters are displayed. When incomplete measurements
occur (due to system errors or a manual termination of the measurement
procedure), dashes (---) take the place of numeric values that are not
valid, and incomplete limit testing results are indicated by a question
mark symbol.
Limit Checking Results
At the top of the screen in the left corner, the overall Pass/Fail result
is displayed next to the name of the selected limit set. The failure of
any one item on the screen produces an overall failure indication. Directly
below the overall Pass/Fail result is information indicating whether the
test was completed successfully or, if not, what error occurred.
Directly to the left of the Downstream and Upstream levels will indicate
the pass/fail status for each item tested. When a measurement fails to
fall within the selected limit-set range, an up or down arrow appears
to the right of the measurement indicating that the value is too high
or too low. Numeric values that are out-of-range appear as bold text.
NOTE: No Pass/Fail information is available when limit checking is
turned off.
The DOCSIS Ranging Summary screen contains one headroom readings:
Upstream Headroom
Upon successful ranging with the network CMTS, DSAM displays the resultant
upstream transmit LEVEL required out of the DSAM. Level Headroom is the
difference between the maximum output possible (58 dBmV for QPSK, 55 dBmV
for 16 QAM) and the LEVEL transmitted. This Level Headroom is tested against
the "Min CM Headroom" limit value if limits are "ON"
(factory default 5 dB).
Example 1: You successfully range with the CMTS. Results show that
the CMTS instructed the DSAM to transmit a QSPK carrier and the successful
transmit level is 42 dBmV. Level Headroom shown is the maximum specified
level for QSPK of 58 - 42 = 16 dB. Since 16 dB is greater than
the 5 dB limit, the measurement passes.
Ranging Graphs
Upon successful ranging, bar graphs will be presented for both the
upstream and downstream levels. In the event that the connection is a
DOCSIS 3.0 connection with bonded channels, these graphs will show all
bonded upstream and downstream channels.