Telecommunications Industry Association
TR41.9-09-11-010M1
Document Cover Sheet
Project Number
PN-3-3602-RV
Document Title
Proposed Test Procedure for VDSL/VDSL2 Signal Power
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 total power. This test procedures is
intended for the revised TSB-31-C (TSB-31-D).
v1.0 – 20050426
Telecommunications Industry Association
TR41.9-09-11-010M1
This would be for TSB 31D development.
14.4
14.4.1
Conditioning VDSL/VDSL2 EUT to Transmit Continuously
General
This subclause provides a suggested test procedure to measure aggregate signal
power, power spectral density (PSD), and longitudinal output voltage (LOV) for
VDSL/VDSL2 modems (VTU-R) against the applicable requirements specified in
ANSI/TIA-968-B.
14.4.2 Conditioning the EUT to Transmit Continuously (add words allowing user
to configure the modem via software)
To properly measure aggregate signal power, PSD, and LOV, the EUT must be
conditioned to transmit at its highest signal power level as allowed by the respective
PSD masks without a sustained connection to companion equipment. The method of
testing with a companion device is impractical for VDSL/VDSL2 equipment since the
companion (VTU-C) equipment may present excessively high signal levels at
frequencies at which the upstream PSD mask demands very low PSD levels. The
amount of attenuation required to reduce the companion equipment’s signals below the
upstream mask would be excessive to permit the link to come up at the maximum
upstream signal power levels. This is because VDSL/VDSL2 equipment automatically
reduces the line rate and power levels over long loops to maintain an acceptable level
of performance. VDSL2 modems that support extended upstream operation must be
tested against all of the spectral masks for all the operational modes that they support.
The VDSL/VDSL2 modem will need to bring the link up over an artificial line (see Figure
14.4-1) whose characteristics effectively force the EUT into its maximum signal power
allowed by the PSD masks. Next, the EUT is strapped or conditioned to disable retrains
so that once the showtime state has been achieved, the EUT may be disconnected from
the artificial line and connected to a 100 ohm measurement termination.
The EUT may need to be trained up with the VTU-C over various line loops to produce
all of the EUT’s PSD upstream signals (US0, US1 & US2). For example for profile 12a:
when the EUT is trained up over a 1000 ft loop it may only produce US1 and US2 PSD
signals at their maximum level. When the EUT is trained up over a 3000 ft loop it may
only produce US0 and US1 signals (US0 may not be at its maximum level). When the
EUT is trained up over a 9000 ft loop it may only produce US0 PSD signal at its
maximum level. The amount of line loops will vary from one vendor’s CPE to another
and even with the same CPE if the start up margin is changed.
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Telecommunications Industry Association
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Figure 14.4-1. VDSL/VDSL2 conditioning setup
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Telecommunications Industry Association
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14.5
Signal Power Limitations, VDSL/VDSL2 Terminal Equipment
968-B, 5.3.1.1
14.5.1
ANSI/TIA-
Background
The aggregate signal power, or total power, of the VDSL/VDSL2 modem must be
limited to minimize near end crosstalk (NEXT) with other DSL systems that share the
same cable binder. Crosstalk is widely recognized as a form of third party harm and
represents the principal impairment to many DSL systems.
14.5.2 Purpose
To verify that the signal power level transmitted to the network is properly limited.
14.5.3
Equipment
(1)
True rms AC voltmeter SEL#41. (bandwidth question here – 5 MHz limit for ac
voltmeter? Should this be Spectrum analyzer since we are seeking up to 30 MHz
bandplan? Should we use term “Power meter” here? (TR 41.7.4 631A uses this
term so maybe we can use their definition)
(2)
100 ohm, 1 %, non-inductive resistor.
Note: Refer to subclause 5.5 for equipment details.
14.5.4 Equipment States Subject to Test
Transmitting continuously at its highest signal power allowed by the PSD mask. For
VDSL2 modems that support extended upstream operation, each EU mask number
must be considered.
14.5.5
Procedure
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Telecommunications Industry Association
TR41.9-09-11-010M1
(1)
Condition the EUT to transmit its upstream signals at the highest power level as
described in 14.4.2.
(2)
Connect the EUT to the test circuit of Figure 14.5-1.
(3)
Measure and record the signal power level in dBm. The level should be averaged
over a time span of at least 10 seconds if shorter term variations are observed.
(4)
Repeat steps 1 to 3 for other upstream signals and different Profiles.
14.5.6 Alternative Methods
The total signal power may also be calculated by integrating the PSD over the operating
band. This task consists of measuring the PSD over the operating band using a 10 kHz
resolution bandwidth at discrete frequencies with a stepped interval of 10 kHz. The
individual PSD readings are then converted to power readings by multiplying the PSD
(in terms of watts/Hz) by the 10 kHz resolution bandwidth. This results in a power level
for each 10 kHz window. These are then summed over the operating band to give the
total power.
14.5.7 Suggested Test Data
(1)
Signal Power Level.
(2)
Upstream signals (US0, US1 & US2) that were measured.
(3)
Line loops length that were used to obtain the total power measurement.
14.5.8 Comments this may change if power meter replaces ac voltmeter and the
figure following this may also change (if the power meter is a 50 ohm source then
a BALUN may be necessary (50 to 100 BALUN) This may make sense to also
update the ADSL section since a power meter is a better method to measure the
ADSL band. The ac volt meter is bandwidth limited and probably should not have
been used for this testing purpose.
If the AC voltmeter has its dBm scale referenced to 600 ohms, then a correction factor
of 7.8 dB must be added to the displayed reading to account for the measurement
impedance of 100 ohms. It is recommended that the voltmeter provide a highimpedance balanced input particularly if the EUT has intentional paths to ground.
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Telecommunications Industry Association
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Figure 14.5-1. Average Signal Power
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