%CALCSNRS_DUAL calculates the signal to noise ratio in each subchannel %for dual-path receiver structure.% [initSNRi,MFBi,noiseSpec,channelGain,inputSpec] = ...%   calcsnrs_dual(initInputSpec,initChannelGain,initNoiseSpec,gamma,usedChannels)% returns the SNRs in initSNRi and the  matched filter bound in the used subchannels % in MFBi. The used channels are returned in Ui, the used noise spectrum in noiseSpec, the% used channel gains in ChannelGain and the used input spectrum in inputSpec.% %The used channel are those which can support at least 2 bits with the given SNR gap in G,% which is manually selected by system operator.%initInputSpec is the raw input power spectrum, initChannelGain the channel gain squared, %initNoiseSpec is the channel noise power spectrum and gamma the snr gap in dB.% 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 and Ming Ding % Version:        %W% %G%% % The authors are with the Department of Electrical and Computer% Engineering, The University of Texas at Austin, Austin, TX.% They can be reached at ming@ece.utexas.edu.% Ming Ding is also with the Embedded Signal Processing% Laboratory in the Dept. of ECE., http://anchovy.ece.utexas.edu.function [initSNRi,MFBi,noiseSpec,channelGain,inputSpec] = ...   calcsnrs_dual(initInputSpec,initChannelGain,initNoiseSpec,gamma,usedChannels)N = (length(initInputSpec)-1)*2;%calculate SNRi for Sx = 1;initSNRi = initInputSpec.*initChannelGain./initNoiseSpec; %Eliminate useless channels, first assume all usuable channels%SNR required to carry 2 bits with given gapSNR2bits = gamma*(2^2-1);%Do not use subchannels which cannot carry 2 bits%usedChannels = initSNRi >= SNR2bits;%Do not use DC and Nyquist sunchannelsif sum(usedChannels) == 0    warning('Not enough transmitt power to transmit any bits through the channel');    warning('RESULTS ARE NOT VALID');    usedChannels(1) = 1;end   noiseSpec = zeros(size(initNoiseSpec));   inputSpec = noiseSpec;   channelGain = noiseSpec;      noiseSpec(usedChannels) = initNoiseSpec(usedChannels);   channelGain(usedChannels) = initChannelGain(usedChannels);      %input power equally distributed over the entire channel   inputSpec(usedChannels) = initInputSpec(usedChannels);%noise and channel gain in used channels %noiseSpec = initNoiseSpec(usedChannels);%channelGain = initChannelGain(usedChannels);%inputSpec = initInputSpec(usedChannels);%matched filter bound if available power would be distributed %over the entire bandwidthMFBi = inputSpec.*channelGain./(noiseSpec+eps);%MFBiall = initInputSpec.*initChannelGain./initNoiseSpec;