Telecommunications Industry Association
(TIA)
PNT-99-03
Quebec, Canada, 19 August 1999
PN-4643 G.pnt AD HOC COMMITTEE CONTRIBUTION
Technical Committee TR-30 Meetings
SOURCE:
CONTRIBUTOR:
Texas Instruments
Name:
Phone:
Fax:
E-mail:
Rohit Gaikwad
Murtaza Ali1
972-997-5290
972-997-5693
mali@ti.com
TITLE:
compatibility experiments
PN-4643 G.pnt: Crosstalk analysis models for G.PNT and G.VDSL spectral
PROJECT:
PN-4643 G.pnt
DISTRIBUTION:
Members of TR-30.1 PN-4643 G.pnt Ad Hoc and meeting attendees
ABSTRACT
The analysis models used in computing crosstalk interference and line attenuation in the original paper [1] were not
provided in the document. The purpose of this document is to clarify this by specifying the FEXT, NEXT, and line
attenuation models. The analysis models provided herein are consistent with those models agreed upon at the
Nuremberg SG15/Q4 meeting on August 6, 1999 [4], [5]. These models will be used by all ITU-T SG15/Q4
participants who perform G.pnt VDSL crosstalk analyses. This will facilitate the generation of uniform and consistent
results.
1
1.
Introduction:
The equations used in computing crosstalk interference and line attenuation in the original paper [1] were
not provided in the document. The purpose of this document is to clarify this by specifying the FEXT,
NEXT, and line attenuation models. The analysis models provided here are consistent with those models
agreed upon at the Nuremberg SG15/Q4 meeting on August 6, 1999 [4], [5]. These models will be used by
all ITU-T SG15/Q4 participants who perform G.pnt – VDSL crosstalk analyses. This will facilitate the
generation of uniform and consistent results.
2.
Crosstalk combining models and line attenuation model
The PSD of G.PNT NEXT is expressed as:
PSDPNT  NEXT ( f )  PSDPNT  Disturber( f ) xn f
3
2
where xn = 8.818 n/49)0.6 or equivalently, xn = 0.8536 n0.6 for n<50.
The FEXT loss model is:
H FEXT  f   klf 2 H channel  f  
2
2
where H channel  f  is the channel transfer function, k is the coupling constant and is 8 10-20 (n/49)0.6 for
n<50 or 3.083 10-20 for 10, 1% worst-case disturbers, l is the coupling path length in feet, f is in Hz. The
FEXT noise PSD is therefore:
PSDPNT  FEXT ( f )  PSDPNT  Disturber( f ) H FEXT  f 
2
Alternately, VDSL NEXT and FEXT noise interference into G.PNT use the same equations.
In the presence of both VDSL and HPNA disturbers, the combined NEXT PSD is expressed according to
the crosstalk combining model in [4]

PSDNEXT ( f )    PSDPNT  Disturber ( f ) X N f

3
2 0.6
1
n


1 / 0.6



0.6
( f ) H 2 ( f ) X F f l2 n
0.6
2
  PSDVDSL  Disturber ( f ) X n f

3
2
n
0.6
2


1 / 0.6
where n1 and n2 are the number of G.PNT and VDSL disturbers respectively and
XN = 8.536  10-15.
Similarly, the combined FEXT PSD due to VDSL and HPNA disturbers is expressed as

2
PSDFEXT ( f )   PSDPNT  Disturber ( f ) H 1 ( f ) X F f 2 l1 n10.6


1 / 0.6
 PSD
VDSL Disturber
2
2
where n1 and n2 are the number of G.PNT and VDSL disturbers respectively with coupling path lengths l1
and l2, and XF = 7.7441  10-21. |H1(f)| and |H2(f)| are the channel transfer functions of the loop over lengths
l1 and l2. In [1], the coupling path lengths l1 and l2 are equal.
The total crosstalk power is obtained by summing the individual NEXT and FEXT powers.
We use G.VDSL loops with no bridged taps having lengths of 300 m, 900 m, 1200 m, and 4500 ft (all of 26
AWG). The R, L, C, G paremeters for the loops were obtained from [3, Table 3.4].
A 3 dBm/Hz exit loss was assumed on the G.PNT transmit spectra while computing the crosstalk powers.
2

1 / 0.6



0.6
The point of injection of NEXT and FEXT is assumed to be at the network interface device (NID) end.
3.
Conclusions:
The models used to generate the data are based on well accepted models published previously [2], [3], [4].
4.
Summary
This contribution is provided for information only.
5. References
[1]
ITU-T Temporary Document NG-102, Q4/15, G.PNT: Spectral compatibility of home phoneline network
transceivers (G.PNT) with xDSL and other existing in-home services, Nuremberg, Germany 2 –6 August 1999
[2]
ITU-T Temporary Document MA-055, Q4/15, G.gen: HomePNA 1.0 Spectral Compatibility, Australia 29
March – 2 April 1999
[3]
Walter Y. Chen, DSL Simulation Techniques and Standards Development for Digital Subscriber Line
Technology, MacMillan Technology Series, 1998
[4]
ANSI T1E1.4/99-002R4, Spectrum Management for Loop Transmission Systems
[5]
ITU-T Temporary Document NG-118R1, Q4/15, G.PNT: G.pnt: Ad hoc group report, Nuremberg, Germany 2 –
6 August 1999
3