wcdmadespread.m

用matlab程序实现WCDMA系统的仿真

function [y,z]=WCDMADespread(unscrambled_signal,chan_code,N)
%******************************************************************************
%function [y,z]=WCDMADespread(unscrambled_signal,chan_code,N)
%
%Copyright 2002 The Mobile and Portable Radio Research Group
%
%Despeads the incoming chip sequence's (the function can accept multiple 
%sequences in a columnwise format) into the associated control bit 
%sequences and data bit sequences.  For each input chip sequence, this 
%function will return one control bit sequence, y, and N data bit sequences
%where 1<=N<=6 corresponding the number of DPDCH's contained in the signal. 
%The data sequences are stored in 'z'.  The data bit sequences are stored 
%as follows:
%    A_1(d11+jd12)
%    A_1(d13+jd14)
%    A_1(d15+jd16)
%    A_2(d21+jd22)
%    A_2(d23+jd24)
%    A_2(d25+jd26)
%    ...
%    ...
%    A_K(dK1+jdK2)
%    A_K(dK3+jdK4)
%    A_K(dK5+jdK6)
%
%Notice that the above example is for the case were N=6.  The coeficients, A_k,
%are complex coefficients due to gains and rotations found either in the channel
%or due to antenna array response characteristcs.  Note that K=the number of 
%chip sequences containd in "unscrambled_singal", which is also the number of 
%columns.  N is the number of DPDCH's containd %in the chip sequence (This is 
%the same of all K chip sequences)
%
% Parameters
%   Input
%      unscrambled_signal   matrix   Contains chipping sequences in a 
%                                    columnwise format.  Number of columns
%                                    indicate the number of chipping
%                                    sequences
%      chan_code            matrix   Channel code matrix.  If N>1, then
%                                    "chan_code" must be a 4x4 matrix
%      N                    scalar    Number of DPDCH's in the chipping
%                                     sequences
%   Output
%      y                    matrix    Contains the control bit sequence from
%                                     each chipping sequence.  The number 
%                                     of rows equals the number of chipping 
%                                     sequences.  
%      z                    matrix    Contains the databit sequences for each 
%                                     chipping sequence in a row wise fashion.
%                                     The storage format is shown above
%******************************************************************************
ChipLength=38400;
%Only 6 data channels are allowed
if (N<1)|(N>6), error('N must be between 1 and 6'); end

%For the case where N>1, check to see if chan_code is a 4x4 matrix
[nrow,ncol]=size(chan_code);
if N>1
   if nrow~=4
      error(['SF=',int2str(nrow),', N=',int2str(N),'!  spreading factor must equal 4 if N>1']); 
   end      
end

%Determine spreading factor
SF=nrow;

%Determine the number of chipping sequences
[row,K]=size(unscrambled_signal);

%create spreading code for control channel
ControlCode=ones(1,256);

%Despread Control Channel
for k=1:K
   SpreadSignal=reshape(unscrambled_signal(:,k),256,150);
   y(k,:)=ControlCode*SpreadSignal;
end

y = (-j)*y;

%Despread Data Channels
if N>1 %We have more than one DPDCH in the signal
   index=1;
   kk=[1 1 3 3 2 2]+1;
   for k=1:K
      SpreadSignal=reshape(unscrambled_signal(:,k),SF,9600);
      for n=1:2:N
         z(index,:)=chan_code(kk(n),:)*SpreadSignal;
         if rem(n,2)==0, z(index,:)=-j*z(index,:); end
         index=index+1;
      end
   end
else  %Then there is only one DPDCH in the signal
   kk=(SF/4)+1;
   SymbolLength=ChipLength/SF;
   for k=1:K
      SpreadSignal=reshape(unscrambled_signal(:,k),SF,SymbolLength);
      z(k,:)=chan_code(kk,:)*SpreadSignal;
   end
end