function ttlist = etsi_loopsSDSL(ttlist,len,selfdisturbers,namestr);
%% ===========================================================================
% etsi_loopsSDSL - Define the ETSI SDSL testloops
%
% Parameter:    ttlist          List to insert the testloops
%               len             Length for loop 1 to 8    
%               selfdisturbers  Number of self disturbers in the loop
%               namestr         Name string extension
% Returns:      ttlist          List with inserted the testloops
%
% Example(s):
%   
% Algorithmic details:
%   
% Reference:
%    ETSI STC TM6 Permanent document TM6(98)10 (DTS/TM-06018), 980p10a3
%    ETSI STC TM6 Helsinki 2000, WD22R3 & WD19R3, 002t22a0
%% ===========================================================================

%% ===========================================================================
% Copyright (C):                                        
%       2000-2002 by Forschungszentrum Telekommunikation Wien, Austria;
%                                                         All rights reserved.
% Project       : B1, SDSL simu
% Author(s)     : Tomas Nordstrom (Tomas.Nordstrom@FTW.at)
%                 Driton Statovci <Statovci@ftw.at>    
%
% CVS:       $Id: etsi_loopsSDSL.m,v 1.4 2002/03/18 11:59:07 tono Exp $
%% ===========================================================================
% Change History
%      2000-06-19 (ToNo) Created
%      2000-07-17 (ToNo) Added header, ETSI TM6 002t22a comments
%      2000-10-25 (GS)   Made it usable for scalar len input argument
%      2000-11-08 (ToNo) Changed format for distances
%      2001-05-05 (DS)   Swapped CO/NT side as now defined in the standard
%      2002-03-18 (ToNo) Renamed the SDSL cables
%% ===========================================================================

if nargin<3,
    selfdisturbers = 49; % 89 for noise A and D, while only 15 for B and C
end
nomodems = selfdisturbers+1;

if nargin<4,
    namestr='';
end

if length(len) == 7,
    len(8) = len(4);
end;
 
if length(len) == 1
   len=len.*ones(1,8);
end

%% ===========================================================================
% Loop #1 connects the transceivers back-to-back. This loop mainly
% stresses the analogue front end (AFE) and the dynamic range of
% the digital processing.
tt.name= sprintf('SDSL-Loop1%s',namestr);             
tt.topology=[
    {0  '' 'CO' ''}; 
    {len(1)  'ETSI-SDSL-PE04'   'NT' sprintf('%.0fm ->',len(1))};
    ];
tt.traffic=[
    {1 2 'SDSL' nomodems};
    ];
ttlist=insertList(ttlist,tt);

%% ===========================================================================
%Loop #2 is a single straight wire that represents typical
%deployment scenarios. When the length of the loop is set to
%maximum reach this loops stresses the SDSL equipment similar to
%typical deployment.
tt.name= sprintf('SDSL-Loop2%s',namestr);             
tt.topology=[
    {0  '' 'CO' ''}; 
    {len(2)  'ETSI-SDSL-PE04'   'NT' sprintf('%.0fm ->',len(2))};
    ];
tt.traffic=[
    {1 2 'SDSL' nomodems};
    ];
ttlist=insertList(ttlist,tt);

%% ===========================================================================
%Loop #3 consists of four segments of wires of different
%diameter. As a result the loop has ripples in its input impedance
%and mainly stresses the echo canceller (EC). This loop has similar
%impedance characteristics in both upstream and downstream
%directions.
seglens=[.1834 .3466 .2866 .1834].*len(3);
tt.name= sprintf('SDSL-Loop3%s',namestr);      
tt.topology=[
   {0  '' 'CO' ''}; 
   {seglens(1)  'ETSI-SDSL-PE04'   '' sprintf('%.0fm ->',seglens(1))};
   {seglens(2)  'ETSI-SDSL-PE05'   '' sprintf('%.0fm ->',seglens(2))};
   {seglens(3)  'ETSI-SDSL-PE06'   '' sprintf('%.0fm ->',seglens(3))};
   {seglens(4)  'ETSI-SDSL-PE04'   'NT' sprintf('%.0fm ->',seglens(4))};
];
tt.traffic=[
   {1 5 'SDSL' nomodems};
];
ttlist=insertList(ttlist,tt);

%% ===========================================================================
%Loop #4 consists of three segments of wires with different
%diameter. Note that it is the same loop as Loop #8, but reversed in
%transmission direction. At the NT end of this loop the impedance
%is above 150Ohm so the NT end of this loop stresses the behaviour
%of transceivers with high impedance loops. The loop impedance on
%the LT side of Loop #4 is not as interesting and theoretically the
%transfer function is the same in both directions. It is, therefore, more
%interesting to test this in the downstream direction (receiver
%under test connected to the NT end), that is, Loop #8.
seglens=[.3466 .3668 .2866].*len(4);
tt.name= sprintf('SDSL-Loop4%s',namestr);             
tt.topology=[
    {0  '' 'CO' ''}; 
    {seglens(1)  'ETSI-SDSL-PE05'   '' sprintf('%.0fm ->',seglens(1))};
    {seglens(2)  'ETSI-SDSL-PE04'   '' sprintf('%.0fm ->',seglens(2))};
    {seglens(3)  'ETSI-SDSL-PE06'   'NT' sprintf('%.0fm ->',seglens(3))};
    ];
tt.traffic=[
    {1 4 'SDSL' nomodems};
    ];
ttlist=insertList(ttlist,tt);

%% ===========================================================================
%Loop #5 consist of three wire segments where the middle segment
%has different characteristics from the end segments. This loop has
%low input impedance and mainly stresses the AFE and the EC. This
%loop stresses SDSL equipment in similar ways to Loop #7.
seglens=[100 len(5)-200 100];
tt.name= sprintf('SDSL-Loop5%s',namestr);             
tt.topology=[
    {0  '' 'CO' ''}; 
    {seglens(1)  'ETSI-SDSL-PVC04'  '' sprintf('%.0fm ->',seglens(1))};
    {seglens(2)  'ETSI-SDSL-PE08'   '' sprintf('%.0fm ->',seglens(2))};
    {seglens(3)  'ETSI-SDSL-PVC04'  'NT' sprintf('%.0fm ->',seglens(3))};
    ];
tt.traffic=[
    {1 4 'SDSL' nomodems};
    ];
ttlist=insertList(ttlist,tt);

%% ===========================================================================
%Loop #6 is the only test loop with bridge taps. The bridge taps
%put spectral nulls in the insertion loss and ripples in the line
%impedance. The impedance at the LT side is very low while the
%impedance at the NT side is close to 135Ohm. Testing with the line
%in the upstream direction will stress equipment more than testing
%in the downstream direction.
seglens=[.7143 .2857].*len(6);
tt.name= sprintf('SDSL-Loop6%s',namestr);             
tt.topology=[
   {0  '' 'CO' '' ...
         0 '' '' ''}; 
   {seglens(1) 'ETSI-SDSL-PE04' ''   sprintf('%.0fm ->',seglens(1))...
         500 'ETSI-SDSL-PE04' 'BT' '500m (ETSI-SDSL-PE04)'};
   {seglens(2) 'ETSI-SDSL-PE04' 'NT' sprintf('%.0fm ->',seglens(2))...
         500 'ETSI-SDSL-PE04' 'BT' '500m (ETSI-SDSL-PE04)'};
    ];
tt.traffic=[
    {1 3 'SDSL' nomodems};
    ];
ttlist=insertList(ttlist,tt);

%% ===========================================================================
%Loop #7 consists of three wire segments of different diameter. The
%line has low input impedance and on the LT side the impedance has
%much more ripples than the NT side, so the LT side is more likely
%to stress the EC.
seglens=[50 .6135*(len(7)-350) .3865*(len(7)-350) 300];
tt.name= sprintf('SDSL-Loop7%s',namestr);             
tt.topology=[
    {0  '' 'CO' ''}; 
    {seglens(1)  'ETSI-SDSL-PVC032'  ''   sprintf('%.0fm ->',seglens(1))};
    {seglens(2)  'ETSI-SDSL-PE04'    ''   sprintf('%.0fm ->',seglens(2))};
    {seglens(3)  'ETSI-SDSL-PE05'    ''   sprintf('%.0fm ->',seglens(3))};
    {seglens(4)  'ETSI-SDSL-PVC063'  'NT' sprintf('%.0fm ->',seglens(4))};
    ];
tt.traffic=[
    {1 5 'SDSL' nomodems};
    ];
ttlist=insertList(ttlist,tt);

%% ===========================================================================
%Loop #8 consists of three segments of wires with different
%diameter. It is the same loop as Loop #4, but reversed in
%transmission direction. 
%At the LT end of this loop the impedance is above 150Ohm
%so the LT end of this loop stresses the behaviour of transceivers
%with high impedance loops. The loop impedance on the NT side of
%Loop #8 is not as interesting and theoretically the transfer
%function is the same in both directions. It is, therefore, more
%interesting to test this loop than Loop #4.
seglens=[.2866 .3668  .3466 ].*len(8);
tt.name= sprintf('SDSL-Loop8%s',namestr);             
tt.topology=[
    {0  '' 'CO' ''}; 
    {seglens(1)  'ETSI-SDSL-PE06'   '' sprintf('%.0fm ->',seglens(1))};
    {seglens(2)  'ETSI-SDSL-PE04'   '' sprintf('%.0fm ->',seglens(2))};
    {seglens(3)  'ETSI-SDSL-PE05'   'NT' sprintf('%.0fm ->',seglens(3))};
    ];
tt.traffic=[
    {1 4 'SDSL' nomodems};
    ];
ttlist=insertList(ttlist,tt);