chan_generator.m

无线仿真Matlab代码

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%   ***************************************************************************
%
%   UMTS-HSDPA channel generator main function
%              
%   Create input trace(s) and the BLER table that can next be used as 
%   input for the ns-2 network simulator.
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Clear workspace
clear all;
close all;


% Set-up parameters 
parameters;                                                    

% get power profile
[profile,spectrum] = environment(multi,-20);

% Determine parameters for multipath fading
fD = vel_mps/lambda;                                                    % maximum Doppler shift
rayleigh_fades = 2*round(dur*fD/2);                               % fades during simulation (must be even)
samples_per_TTI = ceil(rayleigh_fades*samples_per_fade/numTTI);   % Number of samples per TTI
if (samples_per_TTI > max_samples_per_TTI)
    samples_per_TTI = max_samples_per_TTI;
end
samples = numTTI*samples_per_TTI;                                 % Total number of samples

% Determine parameters for shadowing
alpha = exp(-vel_mps*TTIdur/d_corr);                              %velocity *TTIdur=distance 
beta  = sqrt(1-alpha^2);

% Loop generation of traces
for n = 1:nr_users

display('Output generation for user:'),n

    % Set random generator
    randn('state',n);
    
    % Generate multipath traces per tab
    n_tabs = size(profile,2);
    omega_2 = zeros(numTTI,n_tabs);
    
    for ii = 1:n_tabs
        % Generate multipath
        omega = multipath(samples,rayleigh_fades,fD,spectrum);

        % Average samples per TTI
        omega_2(:,ii) = sum(reshape(omega,samples_per_TTI,numTTI))'*profile(ii)/samples_per_TTI;
    end

    % Find resulting power in Rake receiver (in dB)
    P_ff = 10*log10(sum(omega_2,2));

    % In P_ff the sharp dips are negative, i.e. P_ff is the received power.
    % A high positive value of P_ff indicates a good channel condition

    % We compute the total path loss, containing the 
    % fast fading, slow (=shadow) fading, distance loss and 
    % base station antenna gain (GT, in dBi)
    % The shadowing is changing over time. The other three contributions are constant.

    Ploss = -P_ff + shadowing(numTTI,shadow_std,alpha,beta)+distloss-GT;

    % The received power, P_out, is based on: 
    % transmission power, PTx      (scalar constant; in dBm)
    % intra-cell interference      (scalar constant; in dBm)
    % inter-cell interference      (scalar constant; in dBm)
    % power loss, Ploss            (varying over time; in dB)
    P_out=PTx-10*log10((10^(Iintra/10))+(10.^((Iinter+Ploss)/10))); 


    % Based on the received power, P_out, we next compute the total 
    % received power for the retransmissions(RT).
    % P_1stRT=MRC{P(t),P(t+H)}
    % P_2dnRT=MRC{P(t),P(t+H),P(t+2*H)}
    % with MRC=Maximum Ratio Combining function and H=HARQcycle

    P_1stRT = Power1stRT(numTTI,P_out,HARQcycle);  
    P_2ndRT = Power2ndRT(numTTI,P_out,HARQcycle);   

    % And for the evaluation of the number of HARQ retransmissions, consider what 
    % happens if you introduce a third REtransmission (i.e. a fourth Transmission)

    P_3rdRT = Power3rdRT(numTTI,P_out,HARQcycle);   

    % Compute the CQI vector (integer values)
    % CQI and P_out are vectors
    % CQIdelayinTTI is the number of TTI's that is in between the UE measurement and 
    % the actual moment of using this information at the Scheduler in the Node B. 
    % So, CQI(t) is the CQI based on which TBS (Transport Block Size) of the 
    % transmission at TTI t with channel condition P_out(t) is chosen.
 
    % Define the minimum and maximum CQI value allowed (see 3GPP standards).
    % Note that for some user types, the TBS for CQI values 22 to 30 is the same.
    % But this is implemented in the ns-2 simulator.
    minCQI=0
    maxCQI=30               


    [CQI,perctoolow,perctoohigh] = compCQI(numTTI,P_out,CQIdelayinTTI,minCQI,maxCQI);                         
    
    % Save the traces that will next be used in ns-2 link level simulations
    savetrace

end    %end loop over the number of users