function [upband,downband]=planConvertion2Band(frequencies,directions,guardband)
%% ===========================================================================
%planConvertion2Band - Convert a frequency plan into two active bands
%
% Parameter:    frequencies	Array of switching frequencies
% Parameter:    directions	Direction at these frequencies
% Parameter:    guardband	Size (0-1) or (f Hz) of guardbands
% Returns:      upband   	Upper and lower edges in upstream band
% Returns:      downband   	Upper and lower edges in downstream band
%
% Example(s):
%   %% Define a four band plan
%   [upb,downb]=planConvertion2Band([.138e6 2.6e6 5.4e6 10.25e6  20e6],'dudu')
%   low=1;high=2;
%   upb(2,low) % Returns 10.25e6
%   downb(1,high) % Returns 2.6e6
%
%   %% Set up UPBO bands for plan 997 with 125e3 used as guardband
%   bplan = [138 3000 5100 7050 12000]*1e3; % 997 
%   tfplan.PSD.UPBO.band=planConvertion2Band(bplan,'dudu',125e3)
%
%% ===========================================================================

%% ===========================================================================
% Copyright (C):                                        
%       2005-2009 by Forschungszentrum Telekommunikation Wien, Austria;
%                                                         All rights reserved.
% Project       : FTW's xDSLsimu
% Author(s)     : Tomas Nordstrom (Tomas.Nordstrom@FTW.at)
%               : Daniel Bengtsson (Daniel.J.Bengtsson@Telia.se)
%
% CVS:       $Id: planConvertion2Band.m 593 2005-03-24 16:28:02Z tono $
%% ===========================================================================
% Change History
%      2005-03-29 (ToNo) Created (based on planConvertion.m)
%% ===========================================================================

if nargin<2,
    error('Not enough input arguments.');
end

if nargin<3
   guardband = 0;
end;

if length(frequencies) ~= length(directions)+1,
    error('planConvertion2Band: length mismatch');
end;

ui=1;
di=1;
endi=length(frequencies);
i=1;
while i <= length(directions),
    stopi=i+1;
    while ((stopi<endi) && (directions(i) == directions(stopi))),
        stopi=stopi+1;
    end;

    % define guard bands based on switch freqencies
    
    if guardband<1
        % Frequency dependent guard bands
        gbl = frequencies(i)*guardband/2;                    % Guard band low
        gbh = frequencies(stopi)*guardband/2;                % Guard band high
    else
        % Absolute guard bands
        gbl = guardband/2;                                   % Guard band low
        gbh = gbl;                                           % Guard band high
    end;
    if i == 1,     % Do not move first band
        gbl = 0;
    end;
    if stopi==endi % Do not move last band
        gbh = 0;
    end        
    startf = frequencies(i) + gbl; 
    stopf  = frequencies(stopi) - gbh;

    switch directions(i),
     case 'u'
      upband(ui,:) = [startf,stopf];
      ui=ui+1;
     case 'd'
      downband(di,:) = [startf,stopf];
      di=di+1;
     case 'n'
      ui=ui; % Do Nothing
     otherwise
      errstr=sprintf('planConvertion2Band: unknown direction char "%s"',directions(i));
      error(errstr);
    end;
    
    i=stopi;
end;