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Chapter 8 - UMS Configuration
AMA 310/UMS V21.0
8.1.5.1
Modem Upstreams
As the UMS operates when the DOCSIS modems are running, there must by no means be
collisions with the upstream frequencies of the cable modems. Therefore, the UMS has to know on
which upstream frequencies and with which bandwidth (symbol rate) the cable modems transmit in
the network.
By selecting the menu item
UPSTREAMS
an input window can be called up in which all active
modem upstreams with their center frequency and symbol rate can be put in. Up to eight active
upstream frequencies can be defined. When entering the frequency 0, an upstream can be
cancelled from the system. Valid symbol rates are 320 kSym/s, 640 kSym/s, 1280 kSym/s, 2560
kSym/s and 5120 kSym/s. Even here the input of a system graphics shown (see chapter 8.2 -
System Plan) is supported.
8.1.5.2
Bit Error Rate Measurement (BER)
The UMS supports a BER measurement (including MER measurement and constellation diagram
display) in the upstream path. For this purpose e.g. at the subscriber connecting socket modulated
upstream carriers are fed into the return channel by means of the handhelds and they will be
evaluated in the headend. The measurement results will be returned again to the handheld. This
measurement can be performed with active DOCSIS modem operation. However, these test
carriers must not overlap with the modem frequencies. The system supports the BER
measurement in four different frequencies. These can be distributed freely in the return path taking
into account the modem frequencies.
By selecting the menu item
BER-MEAS
an input window can be called up in which up to four test
frequencies with their symbol rates and modulation schemas can be entered. When entering the
frequency 0 a test carrier can be deleted from the system. Valid symbol rates are 320 kSym/s, 640
kSym/s, 1280 kSym/s, 2560 kSym/s and 5120 kSym/s. Admissible modulation schemas are QPSK,
16QAM, 64QAM, 256QAM. Here again the input of a system graphics shown (see chapter 8.2 -
System Plan) is supported.
8.1.5.3
TILT Measurement
Apart from the frequency sweep function the UMS also supports a special TILT function. This is
used in the handhelds for a quick and uncomplicated line-up assistance for return-path-capable
amplifiers as well as for an equalization of a tilted frequency response. Here the handheld transmits
four pilot carriers at the same time, which the headend measures and their levels are transmitted
back to the handheld in real time.
This measurement can be performed during active DOCSIS modem operation. However, the pilot
carriers must not overlap with the modem frequencies. The pilots for the tilt measurement can be
distributed freely in the return path range.
By selecting the menu item
TILT-MEAS
an input window can be called up where four pilot
frequencies can be entered. Here again the input is supported by a system graphics shown (see
chapter 8.2 System Plan).
8.1.6
Forward Path Measurement
The UMS can also be configured for measurements in the forward path. For this purpose certain
downstream frequencies may be set in the headend unit, which can be measured systematically by
the handheld within the scope of the report function (see chapter 8.1.9 - Report). The idea here is
that at a central point it is possible to set which measurements shall be performed and recorded in
situ via the handhelds in the forward path.
By selecting the menu item
DNSTREAMS
an input window can be called up in which several
downstream frequencies with their symbol rates and modulation schemas can be entered. When