compcqi.m

无线仿真Matlab代码

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%   ***************************************************************************
%
%   UMTS-HSDPA channel generator
%              
%   [CQI,perctoolow,perctoohigh] = 
%                   compCQI(numTTI,P_out,CQIdelayinTTI,minCQI,maxCQI)
%
%   Calculates the Channel Quality Indicator (CQI) for each TTI, based on 
%   an associated delayed received power.
%   Also percentages that quantify the amount of CQI values that are clipped 
%   (in order to satisfy the [minCQI,maxCQI] constraint) are computed.
%
%   Note that the first CQIdelayinTTI elements are not written to the tracefile.
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

function [CQI,perctoolow,perctoohigh] = compCQI(numTTI,P_out,CQIdelayinTTI,minCQI,maxCQI)

% Generate the power shifted in time.
% This models the delay caused by the time in between the CQI computation at 
% the UE and the actual use of it at the scheduler (Node B).

P_shft = [zeros(CQIdelayinTTI,1);P_out(1:numTTI-CQIdelayinTTI)];       
% The first CQIdelayinTTI elements of P_shft do not make sense and are not 
% written to the tracefile.


% An analytical formula is defined that fits the CQI-dependent BLER 
% versus Eb/No results in an AWGN channel.
% As a result, the choice of its parameters is independent of the UE environment.
Offset=16.62      
CQIratio=1.02
CQIhlp=floor(P_shft/CQIratio+Offset);
% Round down (and not up) because the error probability (BLER) must not exceed the 10 % level

%Display the effect of clipping the CQI values to satisfy the [minCQI,maxCQI] constraint
[value_min,index_min]=min(CQIhlp);
[value_max,index_max]=max(CQIhlp);
disp('CQI range (BEFORE clipping):')
disp('Maximum CQI value of '),value_max
disp('Minimum CQI value of '),value_min


adaptCQI=1               % flag
if adaptCQI==1
  %Replace all negative CQI values by the zero.
  disp('Extreme CQI values are adapted: CQI<0 and CQI>maxCQI')
  toolowindex=(CQIhlp<minCQI);
  perctoolow=round(100*sum(toolowindex)/numTTI)
  CQIhlp(toolowindex)=0;
  toohighindex=(CQIhlp>maxCQI);
  perctoohigh=round(100*sum(toohighindex)/numTTI)
  CQIhlp(toohighindex)=maxCQI;
else
  disp('Extreme CQI values are NOT adapted')
end;    %end if adaptCQI


[value_min,index_min]=min(CQIhlp);
[value_max,index_max]=max(CQIhlp);
disp('CQI range (AFTER clipped):')
disp('Maximum CQI value of '),value_max
disp('Minimum CQI value of '),value_min


CQI=CQIhlp;