adsl.m

多载波调制的仿真程序

%DSL Simulate a standard digital subscriber line.
% [Y, H, N] = DSL(X, channelName, P, S) returns the received signal
% Y (without channel noise), channel impulse response in H, and
% channel noise in N. The channel noise consists of NEXT noise 
% and AWGN of power P. 
%
% X is the transmitted signal. channelName is a string containing
% the channel name. The channel data should be in a subdirectory 
% "channel". Currently supported channels are the CSA loops from 1 
% to 8. The name format is "" where # = {1,2,..,8}. P is the
% AWGN power. S is a subsampling factor. The default length of
% H is 512 samples. A shorter channel can be generated by subsampling
% H by a factor of S. 

% Copyright (c) 1999-2002 The University of Texas
% All Rights Reserved.
%  
% This program is free software; you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation; either version 2 of the License, or
% (at your option) any later version.
%  
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU General Public License for more details.
%  
% The GNU Public License is available in the file LICENSE, or you
% can write to the Free Software Foundation, Inc., 59 Temple Place -
% Suite 330, Boston, MA 02111-1307, USA, or you can find it on the
% World Wide Web at http://www.fsf.org.
%  
% Programmers:	Guner Arslan
% Version:        @(#)dsl.m	1.4	07/26/00
% 
% The authors are with the Department of Electrical and Computer
% Engineering, The University of Texas at Austin, Austin, TX.
% They can be reached at [e-mail].
% Guner Arslan is also with the Embedded Signal Processing
% Laboratory in the Dept. of ECE., http://anchovy.ece.utexas.edu.



% open a figure for progress bar

     
channelName='csaloop8';
% set path for channel files 
addpath channels
% load channel data 
channelTime = ['load ',channelName,'.time'];
eval(channelTime)
% put channel data into h and time axis into t
string = ['t = ',channelName,'(:,1); h = ',channelName,'(:,2);'];
eval(string)
% sampling frequency
noisePower=143;
fsample = 2.208e6;
% normalization is required due to the way channel data is stored
h1 = h/2.208e6;
h1 = [h1 ;zeros(2048,1)];
% POTS splitter
[b a] = cheby1(5,1,4.8e3/fsample,'high'); %a=1; b =1;
% channel with splitter
h = filter(b,a,h1);
%h = decimate(h,5);
h = h(1:512);
figure(1)
stem(h);
Ntot=512;
f=-1/2+1/Ntot:1/Ntot:1/2;
Hn = zeros(1,Ntot);
% find Hn vector
for i=1:length(h)
	Hn=Hn+h(i)*exp(j*2*pi*f*(i-1)); 
        % This value will be different depending if P represents 
        % P(1) + P(2)*D^-1 + ....  or P(1) + P(2)*D^+1....,
        % but we'll get same gn, thus same waterfilling result.
        % (Note that both have the same magnitude response!)
end
figure(2)
plot(10.*log10(abs(Hn)))

% find gn vector
%gn=abs(Hn).^2/noisePower;
%gn=20.*log10(abs(Hn));
%plot(gn);
%[b a] = butter(1,0.5);
%h = filter(b,a,h2);
%rampup = linspace(0,1,20);
%rampdown = linspace(1,0,20);
%h(1:20) = h(1:20).*rampup.';
%h(end-19:end) = h(end-19:end).*rampdown.';
%h(512:end) = h(512:end).*(length(h(512:end))-1:-1:0)'/(length(h(512:end)));
% channel with TEQ if TEQ is given
%hw = filter(wteq/(norm(wteq)),1,h2);
% filter transmit data with channel impulse response
%h = decimate(h,5);
%h = [h(1:425); zeros(512-425,1)];