GreedyAlgOfdmExample.m

% The codes investigate the performance of a greedy algorithm [1] in OFDM which
% allocates the power to subchannel in optimum way to reach the required
% Data rate

% By Hamid Ramezani 23-Mar-2008

% setting the parameters
numOfSubChannels = 16;        % number of subchannels
modBitRate       = [0;1;2;4;6];% the provided bit rate bits/Hz/Sec for 
                               % example based on BPSK, QPSK, 16QAM and 
                               % 64QAM modulation
                               % zero is required to states that
                               % subchannels can convey no data
                               
reqSNR         =10.^(.1*[-Inf;9;12;18;24]); 
                               % Reqired SNR for the receiving the 
                               % the bits through modulation on 10^-4 BER
                               % condition ref[2]
                               % zero is required to states that
                               % subchannels can convey no power
   %Attention
        % The single-side noise power spectral density (N0) is assumed to be 1
        % otherwise the parameter setting must be modified
        % SNR = Pt*CSI^2/(N0*B/N) which is assumed to SNR = Pt*CSI^2 (it is
        % a kind of normalization)
                               
requiredRate     = 23;         % bits/Sec/Hz


% channel coefficient generation
    % rayleigh fading channel (with Rician absulute)
    CSI = 1/sqrt(2) * abs ( randn(numOfSubChannels,1) + ...
        sqrt(-1)*randn(numOfSubChannels,1));

% calling the mex function
[subChannelrequiredPower,subChannelRate] = ...
    greedyAlgSingleUser(requiredRate,CSI,modBitRate ,reqSNR);


% Graphical observation
    f1 = figure(1);
    set(f1,'color',[1 1 1]);
    subplot(2,2,1)
        bar(subChannelRate)
        xlabel('Subchannel Indice');
        ylabel('number of bits conveied by subchannels');
    subplot(2,2,2)
        bar(10*log10(subChannelrequiredPower))
        xlabel('Subchannel Indice');
        ylabel('amount of power required by subchannels in dB');
    subplot(2,2,3)
        bar(20*log10(CSI))
        xlabel('Subchannel Indice');
        ylabel('channel response in different subchannels');
    subplot(2,2,4)
        bar(10*log10(subChannelrequiredPower./(CSI.^2)))
        xlabel('Subchannel Indice');
        ylabel('SNR in different subchannels');
        
% References
% Ref[1] C. Y. Wong, R. S. Cheng, K. B. Letaief and R. Murch, "Multiuser
%        OFDM with Adaptive Subcarrier, Bit, and Power Allocation", IEEE
%        Journal on Selected Areas In Communications, Vol. 17, No. 10,
%        OCTOBER 1999

% Ref[2] Y. Zhang, and K. B. Letaief, Multiuser Adaptive Subcarrier-and-Bit 
%        Allocation With Adaptive Cell Selection for OFDM Systems, IEEE Transaction
%        on wireless communications, Vol. 3, No. 5, Sep 2004