Telecommunications Industry Association
TR41.9-09-11-009M1
Document Cover Sheet
Project Number
PN-3-3602-RV
Document Title
Proposed Test Procedure for VDSL/VDSL2 Power Spectral Density
Source
Cisco Systems, Inc.
Contact
Tim Lawler
170 West Tasman Dr.
San Jose, CA 95134
Distribution
TR-41.9, at the November 2009 meeting
Intended Purpose
of Document
(Select one)
X
Phone: (408) 527-0681
Fax: (408) 526-4184
Email: tlawler@cisco.com
For Incorporation Into TIA Publication
For Information
Other (describe) -
The document to which this cover statement is attached is submitted to a Formulating Group or
sub-element thereof of the Telecommunications Industry Association (TIA) in accordance with the
provisions of Sections 6.4.1–6.4.6 inclusive of the TIA Engineering Manual dated March 2005, all of
which provisions are hereby incorporated by reference.
Abstract
This contribution provide test procedure for measuring VDSL/VDSL2 Power Spectral Density (PSD).
This test procedure is intended for the revised TSB-31-C (TSB-31-D).
v1.0 – 20050426
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14.6
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Power Spectral Density, VDSL/VDSL2 Terminal Equipment ANSI/TIA-968B, 5.3.8.1.3, 5.3.8.1.4
14.6.1 Background
As is the case for the VDSL/VDSL2 modem’s total power, its PSD must be limited to
minimize crosstalk. PSD is limited by the imposition of a PSD mask, which specifies a
limit as a function of frequency. The mask permits a reasonable level in the operating
bands while restricting the VDSL/VDSL2 modem’s PSD below the operating bands to
protect POTS and above the operating bands both to minimize interference both with
the downstream spectrum as well as other DSL systems potentially affected by
crosstalk. The masks presents measurement challenges because it specifies such a
broad range of signal levels, which can’t practically be made in a single sweep due to
limitations in the spectrum analyzer’s dynamic range. For this reason and resolution
bandwidth considerations, the mask is broken into two segments.
14.6.2
Purpose
To verify that the PSD is below the mask.
14.5.3 Equipment
(1)
(2)
Spectrum analyzer SEL#57.
100:50 ohm balun transformer SEL#70.
(Editor’s note: new SEL)
(3)
100:50 ohm balun transformer SEL#59.
Note: Refer to subclause 5.5 for equipment details.
14.5.4
Equipment States Subject to Test
Transmitting continuously its upstream signals at their highest signal power allowed by
the PSD mask. For VDSL2 modems that support extended upstream operation, each
EU mask number must be considered.
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Procedure
In this section the criteria frequency range has been divided into two segments. The
number of segments chosen is dependent upon the capabilities of the test equipment.
Each frequency point in the operating bands (corresponding to a measurement in a
single resolution bandwidth) of a PSD should be measured by averaging the power in
the resolution bandwidth of that frequency point for a time period of at least 10 seconds.
14.5.5.1
Procedure for Segment 1
(1)
Condition the EUT to transmit US0 continuously as described in subclause 14.4.2.
(2)
Connect the EUT to the test circuit of Figure 14.5-1 using balun transformer
SEL#70.
(3)
Set the spectrum analyzer as follows:
Resolution bandwidth (RBW): 100 Hz
Video bandwidth: 3 Hz
Attenuation: Set for minimum without overload
Reference level: (-20) dBm
dB/div: 10 dB
Marker Function: Noise dBm/Hz
Start frequency: 200 Hz
Stop frequency: 25.875 kHz
(4)
Measure and record the PSD over the first segment (200 Hz to 25.875 kHz) of the
mask, which covers the voice frequency band.
(5)
Repeat steps 1 to 4 for other Profiles.
(6)
For extended upstream operation, repeat steps 1 to 5 for each supported EU
mask (US0).
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14.5.5.2
TR41.9-09-11-009M1
Procedure for Segment 2
(1)
Condition the EUT to transmit its upstream signals continuously as described in
14.4.2.
(2)
Connect the EUT to the test circuit of Figure 14.5-1 using balun transformer
SEL#59.
(3)
Set the spectrum analyzer as follows:
Resolution bandwidth: 10 kHz
Video bandwidth: 3 kHz
Attenuation: 40 dB
Reference level: (0) dBm
dB/div: 10 dB
Marker Function: Noise dBm/Hz
Start frequency: 25.875 kHz
Stop frequency: 30 MHz
(4)
Measure and record the PSD over the second segment (25.875 kHz to 30 MHz) of
the mask.
(5)
Repeat steps 1 to 4 for other upstream signals (US0, US1 & US2) and different
Profiles.
(6)
For extended upstream operation, repeat steps 1 to 5 for each supported EU
mask (US0).
14.5.6 Alternative Methods
None
14.5.7 Suggested Test Data
(1)
Plots of the PSD for each segment with the limit line shown on each graph.
(2)
Upstream signals (US0, US1 & US2) that were measured.
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(3)
TR41.9-09-11-009M1
Line loops length that were used to obtain the PSD measurement for the upstream
signals.
14.5.8 Comments
(1)
Care must be taken to ensure that measurement errors are kept to a minimum.
Sources of error may include the following:
Impedance deviations from the ideal 100 ohm termination
Balun loss
Limited amplitude accuracy of the spectrum analyzer
PSD measurement errors caused by excessively fast sweep times or not
averaging enough samples when making a swept average measurement
(2)
Some spectrum analyzers may need a low-pass filter set to cut off frequency of 30
kHz for the Segment 1 measurement.
(3) Some spectrum analyzers may need a high-pass filter to cut off the US0 frequency
for the Segment 2 measurement.
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Figure 14.5-1. PSD Connection Diagram For Segments 1 & 2
The following measurement examples are for reference only and are not intended to be
included in TSB-31-D.
Power Spectral Density
-30.00
-40.00
-50.00
-60.00
Power density (dBm/Hz)
-70.00
-80.00
-90.00
-100.00
-110.00
-120.00
-130.00
-140.00
1.00 k
10.00 k
Frequency (Hz)
–––– Limit
–––– Result
Segment 1: 200 Hz to 25.875 kHz, Profile 17a, EU-32, loop set to 9kft.
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US0
TR41.9-09-11-009M1
US1
US2
Segment 2: 25.875 kHz to 30 MHz, Profile 17a, EU-32, loop set to 9kft, US0 on.
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US0
TR41.9-09-11-009M1
US1
US2
Segment 2: 25.875 kHz to 30 MHz, Profile 17a, EU-32, loop set to 3kft, US0 & US1on.
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US0
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US1
US2
Segment 2: 25.875 kHz to 30 MHz, Profile 17a, EU-32, loop set to 1kft, US1 & US2 on.
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