Telecommunications Industry Association
TR41.9-15-05-006
Document Cover Sheet
Project Number
Document Title
Overview of G.Fast
Source
Cisco Systems
Contact
Tim Lawler
170 West Tasman Dr.
San Jose, CA 95134
Distribution
TR-41.9
Intended Purpose
of Document
(Select one)
X
Phone: (408) 527-0681
Fax: (408) 853-3288
Email: tlawler@cisco.com
For Incorporation Into TIA Publication
For Information
Other (PSD Requirements from G.9700describe) -
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 3.3.2.2 through 3.3.2.4 inclusive of the TIA Engineering Committee Operating Procedures dated
May 2014, all of which provisions are hereby incorporated by reference.
Abstract
This contribution provides an overview of the PSD and other requirements for G.Fast from ITU-T G.9700
that could go into TIA-968-B to protect wireline carrier networks from harm.
V2.1 – 20141205
Telecommunications Industry Association
TR41.9-15-05-006
Abbreviations and acronyms
FAST
Fast Access to Subscriber Terminals
FTU
FAST Transceiver Unit
FTU-O
FTU at the Optical network unit
FTU-R
FTU at the Remote site (i.e., subscriber end of the loop)
LESM
Low-frequency Edge Stop-band Mask
LPM
Limit PSD Mask
MBW
Measurement Bandwidth
TxPSDM
Transmit PSD Mask
7.2
PSD mask specifications
7.2.1 Limit PSD mask (LPM)
The limit PSD mask (LPM) represents the absolute maximum that the TxPSDM shall never
exceed. The in-band LPMs for 106 MHz profile and 212 MHz profile are presented in clause
7.2.1.1. The out-of-band LPMs are defined in clause 7.2.1.2.
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TR41.9-15-05-006
7.2.1.1 In-band LPM
The in-band LPMs for the 106 MHz profile and the 212 MHz profile are shown in Figures 7-1 and
7-2, respectively. The parameters for these LPMs are presented in Tables 7-2 and 7-3, respectively.
PSD in
dBm/Hz
−65
−73
−76
ft r1
ft r2
30
Frequency
in MHz
G.9700(13)_F7-1
Figure 7-1 – In-band limit PSD mask for 106 MHz profile
This PSD measurement is done using a 1 MHz MBW.
Table 7-2 – Parameters of in-band LPM for 106 MHz profile
Parameter
Frequency
(MHz)
PSD
(dBm/Hz)
ftr1
2
– 65
30
– 65
30
– 73
106
– 76
ftr2
Description
The LPM below ftr1 is defined in clause 7.2.1.2.
The PSD limit values between the points listed shall be
obtained by linear interpolation in dB over linear
frequency scale. The LPM above ftr2 is defined in clause
7.2.1.2
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Telecommunications Industry Association
TR41.9-15-05-006
PSD in
dBm/Hz
−65
−73
−76
−79
ft r1
30
ft r2 Frequency
in MHz
106
G.9700(13)_F7-2
Figure 7-2 – In-band limit PSD mask for 212 MHz profile
This PSD measurement is done using a 1 MHz MBW.
Table 7-3 – Parameters of in-band LPM for 212 MHz profile
Parameter
Frequency
(MHz)
PSD
(dBm/Hz)
ftr1
2
– 65
30
– 65
30
– 73
106
– 76
212
– 79
ftr2
Description
The LPM below ftr1 is defined in clause 7.2.1.2.
The PSD limit values between the points listed shall be
obtained by linear interpolation in dB over linear
frequency scale. The LPM above ftr2 is defined in clause
7.2.1.2
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Telecommunications Industry Association
TR41.9-15-05-006
7.2.1.2 Out-of-band LPM
The out-of-band LPM shall be as shown in Figure 7-3 for the low-frequency edge, and in Figure
7-4 for the high-frequency edge, where PSDtr1 is the value of the in band LPM at frequency ftr1
and PSDtr2 is the value of the in-band LPM at frequency ftr2. The parameters for these LPMs are
presented in Tables 7-4 and 7-5, respectively.
PSD
(dBm/Hz)
PSD tr1
175 kHz
−80
See ITU-T G.993.2 Annex A, B, or C
−90
−97.5
−100
4
20
500
ft r1
Frequency
(kHz)
G.9700(13)_F7-3
Figure 7-3 – Low-frequency edge out-of-band LPM
Requirements for frequencies below 4 kHz are specified in Annex A of ITU T G.993.2 for the
region of North America.
The frequency point between 500 kHz and ftr1 is 1.825 MHz (2 MHz (ftr1) – 175 kHz).
The MBW for this PSD mask is 1 kHz for 4 kHz to 20 kHz and 10 kHz for 20 kHz to 2 MHz.
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Telecommunications Industry Association
TR41.9-15-05-006
Table 7-4– Parameters of low-frequency edge out-of-band LPM
ftr1
(MHz)
PSDtr1
Description
(dBm/Hz)
The PSD limit at transition frequency ftr1 drops from PSDtr1
to -80 dBm/Hz.
2
– 65
The PSD limit in the transition band shall be obtained by
linear interpolation in dB over linear frequency scale.
The PSD limit between 4 and 20 kHz shall be obtained by
linear interpolation in dB over a log(f) scale.
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Telecommunications Industry Association
TR41.9-15-05-006
Figure 7-4 – High-frequency edge out-of-band LPM
This PSD measurement is done using a 100 kHz MBW and measured up to 300 MHz.
Table 7-5– Parameters of high-frequency edge out-of-band LPM
ftr2
(MHz)
PSDtr2
(dBm/Hz)
Transition band, Δfth
106
–76
20
212
–79
40
Description
(MHz)
The PSD limit in the transition band (Δfth)
shall be obtained by linear interpolation in dB
over linear frequency scale.
For 106 MHz profile the frequency point between ftr2 and 300 MHz is 126 MHz (106 MHz (ftr2)
+ 20 MHz (Δfth)).
For 212 MHz profile the frequency point between ftr2 and 300 MHz is 252 MHz (212 MHz (ftr2)
+ 40 MHz (Δfth)).
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TR41.9-15-05-006
Transmit PSD verification
The measurement bandwidth (MBW) for evaluation of the PSD shall be as defined in Table 8-1.
The measurement bandwidth shall be centred on the frequency in question.
The mask value to be compared against shall be the maximum value the mask takes within a
window [f − ½×MBW, f + ½×MBW].
Table 8-1 – Measurement bandwidth settings for transmit PSD verification
Frequency band
Measurement bandwidth
(MBW)
4 kHz < f < 20 kHz
1 kHz
20 kHz < f < ftr1
10 kHz
(ftr1+ ½×MBW) to (30 MHz – ½×MBW)
1 MHz
(30 MHz + ½×MBW) to (ftr2 – ½×MBW)
1 MHz
>ftr2 to 300 MHz
100 kHz
Note: ftr1 is 2 MHz, ftr2 is 106 MHz or 212 MHz.
Below are the calculations for the 1 MHz measurement bandwidth:
2 MHz (ftr1) + (0.5 x 1 MHz) = 2 MHz + 500 kHz = 2.5 MHz
30 MHz – (0.5 x 1 MHz) = 30 MHz – 500 kHz = 29.5 MHz
So the frequency range would be:
2 MHz to 29.5 MHz
1 MHz
30 MHz + (0.5 x 1 MHz) = 30 MHz + 500 kHz = 30.5 MHz
For 106 MHz profile:
106 MHz (ftr2) – (0.5 x 1 MHz) = 106 MHz – 500 kHz = 105.5 MHz
So the frequency range would be:
30.5 to 105.5 MHz
1 MHz
For 212 MHz profile:
212 MHz (ftr2) – (0.5 x 1 MHz) = 212 MHz – 500 kHz = 211.5 MHz
So the frequency range would be:
30.5 to 211.5 MHz
1 MHz
The equations above show that there is a +/- 500 kHz gap.
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Telecommunications Industry Association
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For TIA-968-B I would recommend that the 1 MHz measurement bandwidth frequency bands be
the following without the +/- 500 kHz gap:
Frequency band
RBW
2 MHz to 106 MHz
1 MHz
Frequency band
RBW
2 MHz to 212 MHz
1 MHz
I also recommend that MBW be RBW in TIA-968-B.
7.3
Termination impedance
A termination impedance of RV = 100 Ohm, purely resistive, at the U interface, shall be used for
both the FTU-O and the FTU-R.
7.4
Maximum aggregate transmit power
The maximum aggregate transmit power of both the FTU-O (in the downstream direction) and the
FTU-R (in the upstream direction) shall not exceed the level specified in Table 7-1 for any given
profile when measured using the termination impedance defined in clause 7.3.
Table 7-1 – Profile control parameters
Profile (Note 1)
Parameter
Maximum aggregate
transmit power
106 MHz
+4 dBm (See clauses 7.3 and 7.4)
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212 MHz
For further study
Telecommunications Industry Association
TR41.9-15-05-006
Electrical requirements from G.9701
14.x.1 Longitudinal conversion loss
The LCL of the FTU transceiver shall be greater than or equal to 38 dB in the frequency band up
to 12 MHz. The LCL above 12 MHz is for further study.
I recommend that transverse balance requirements use the values in figure 36 of TIA-968-B in the
range of 2 MHz to 30 MHz.
Also G.9701 mentions that G.Fast can be deployed over POTS, so the following additional
requirements from TIA-968-B would need to be done:
Transverse balance requirements for analog voice band equipment in 5.1.10.
Limitations on equipment intended for operation on loop start telephone facilities requirements in
5.1.11.2.
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