function [E_up,E_down] = evalPBO(PBOmethod,PBOparam,tot_Att,start_node,stop_node,Ref_Att,Ref_Noise,dmax);
%% ===========================================================================
% evalPBO -     Calculates PBO for up and downstream 
%
%        INPUT
%        -----
%        PBOmethod :    PBO method 
%        PBOparam  :    Parameters for the choose method
%        tot_Att   :    matrix with Attenuation in dB/km
%        start_node:    Start node for PBO modem
%        stop_node :    Stop node for PBO modem
%        Ref_Att   :    Reference Attenuation for PBO calculation
%        Ref_Noise :    Reference Noise for PBO method
%        dmax      :    Maximum length VDSL modem
%
%        OUTPUT
%        ------
%        E_up      :    Scaling of transmit upstream PSD
%        E_down    :    Scaling of transmit downstream PSD
%
% Example(s):
%
% Algorithmic details:
%
% Reference:
%    FSAN duplex simulation memo, Telia 1998
%% ===========================================================================

%% ===========================================================================
% Copyright (C) 1998 by Telia Research AB, Lulea, Sweden; All rights reserved. 
% Project       : FSAN duplex model
% Author(s)     : Tomas Nordstrom (Tomas.B.Nordstrom@Telia.se)
%               : Daniel Bengtsson (Daniel.J.Bengtsson@Telia.se)
%
% CVS:       $Id: evalPBO.m,v 1.2 1999/03/31 13:15:56 tono Exp $
%% ===========================================================================
% Change History
%      1998-12-16 (DaB) Created     
%      1998-12-22 (ToNo) Added and updated comments
%		 1999-02-04 (DaB) Modified to allowmultiple cables 
%      1999-03-10 (DaB) Added new PBO methods
%      1999-03-11 (DaB) New input arguments
%% ===========================================================================
global ex;

f=ex.param.f; 	% Frequency axis

switch PBOmethod
case 'None', 	% No PBO method
   E_up=ones(1,length(f));
case 'RefLen',	% Reference length method
   att=tot_Att(stop_node,:)-tot_Att(start_node,:);
   tmp=Ref_Att.*(PBOparam./1000)-att;
   tmp=min(tmp,zeros(size(f)));
   E_up=ones(1,length(f)).*10.^(tmp/10);
case 'RefFEXT',	% Reference FEXT method
   att=tot_Att(stop_node,:)-tot_Att(start_node,:);
   len_att=ex.tt.topology{stop_node,1}-ex.tt.topology{start_node,1};
   tmp=Ref_Att.*(PBOparam./1000)+10*log10(PBOparam)-att-10*log10(len_att);
   tmp=min(tmp,zeros(size(f)));
   E_up=ones(1,length(f)).*10.^(tmp/10);
case 'RefFreq'	% Reference frequency method	
   f_ref=PBOparam;
   f_index=max(find(f<=f_ref));
   att=tot_Att(stop_node,f_index)-tot_Att(start_node,f_index);
   tmp=Ref_Att(f_index).*dmax-att;
   tmp=min(tmp,zeros(size(f)));
   E_up=ones(1,length(f)).*(10.^(tmp/10));
case 'RefNoise'	% Reference Noise method	
   att=tot_Att(stop_node,:)-tot_Att(start_node,:);
   len_att=(ex.tt.topology{stop_node,1}-ex.tt.topology{start_node,1})./1000;
   tmp=10*log10(Ref_Noise)-att-20*log10(f./1e6)-10*log10(len_att)-ex.param.XTlevel.FEXT+60;
   tmp=min(tmp,zeros(size(f)));
   E_up=ones(1,length(f)).*(10.^(tmp/10));

otherwise
   sprintf('Unknown PBO mthods: %s',PBOmethod)
end; %switch

E_down=ones(1,length(f));	% Downstream PBO not implemened !!!!!!!