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Chapter 6 - Measuring Mode UMS (Upstream-Monitoring-System)
AMA 310/UMS V21.0
Chapter 6
Measuring Mode UMS (Upstream-Monitoring-System)
6.1
Introduction
The Upstream-Monitoring-System (UMS) is a measuring system consisting of an instrument in the
headend and one or several handheld devices for field use. The UMS serves for measuring the
return path in a DOCSIS net. The following measurements can be performed with this system:
sweeping (= frequency response measurement), TILT measurement, BER measurement, MER
measurement, constellation diagram, real time spectrum. The measurements can be performed
during active modem operation.
The data transmission from the headend device to the handheld devices will be done via transport
stream and DVB-C modulation. If the headend has a transport stream multiplexer, the UMS data
stream may be added to an existing DVB-C channel.
The commands from the field device VAROS 107 to the headend AMA 310/UMS will be sent via
narrow-band telemetry carriers which are directly located in the upstream frequency range on
otherwise unused frequencies.
The overall communication is thus directly made via the cable net to be measured. No additional
transmission channel (Internet, mobile communication connection,
…
) is required.
Further information can be found in the Application-Note "AN006
–
Upstream-Monitoring-System
UMS" on
→
"Application Notes".
Basically the overall measurement functionality is initiated from the field device, during on-going
UMS operation virtually no operating steps are required at the AMA 310/UMS. Therefore, we also
refer to the operating instructions of the field device VAROS 107 apart from the Application Note
mentioned above.
6.2
Starting the System
Before the UMS system can be used successfully, some settings have to be made on the headend.
These are summarized in Chapter 8 - UMS Configuration.
Unless "AUTO-START" has been set in the configuration (see Chapter 8.1.1.1 - Auto-Start), the
function UMS can be started manually from the basic state via the
F2
key (
START
).
First all hardware modules are initiated. Subsequently the return path spectrum can be seen on the
graphics screen (see Figure 6-1).
The level raster is 10 dB/DIV. The dynamic range may be a maximum of 70 dB.
The labeling of the level lines in the unit dBµV can be seen on the left. In the lower blue bar the
start and stop frequencies (band limits) are shown.
The horizontal dotted line with red labeling "ref" is the level reference preset in the UMS setting
(see Chapter 8.1.3 - Network Settings) which should correspond to the nominal input level of the
CMTS.
Note:
The scaling of the level axis is done automatically depending on the
reference level set!