www.gusucode.com > LTE仿真Matlab源码 > LTE_tx_precoding.m
function [precode_y, UE, D, W, U] = LTE_tx_precoding(LTE_params, layer_x, UE, AtPorts, codebook_index, RI, CDD,rb_numbers)
% Precoding according to 3GPP TS 36.211-820, Section 6.3.4 page 37
% TODO: reorganize this huge tree so it more readable. Check whether
% something can be precalculated and stored
% Author: Stefan Schwarz, sschwarz@nt.tuwien.ac.at
% (c) 2009 by INTHFT
% www.nt.tuwien.ac.at
d = 0;
if (AtPorts ~= 1) % for 1 transmit antenna no precoding is used (precoding matrix = 1)
if (UE.mode == 2) % transmit diversity, Section 6.3.4.3
if (AtPorts == 2)
c = length(layer_x(1,:));
precode_y = zeros(2,2*c);
X =1/sqrt(2)*[1,0,1i,0;0,-1,0,1i;0,1,0,1i;1,0,-1i,0]*[real(layer_x(1,:));real(layer_x(2,:));...
imag(layer_x(1,:));imag(layer_x(2,:))];
precode_y(1,1:2:2*c-1)=X(1,:);
precode_y(2,1:2:2*c-1)=X(2,:);
precode_y(1,2:2:2*c)=X(3,:);
precode_y(2,2:2:2*c)=X(4,:);
D = 0; % these matrices are needed in the receiver for undoing the precoding
W = 0;
U = 0;
else
c = length(layer_x(1,:));
precode_y = zeros(4,4*c); % NOTE: cleanup
Z = [1,0,0,0,1i,0,0,0;0,0,0,0,0,0,0,0;0,-1,0,0,0,1i,0,0;0,0,0,0,0,0,0,0;0,1,0,0,0,1i,0,0;...
0,0,0,0,0,0,0,0;1,0,0,0,-1i,0,0,0;0,0,0,0,0,0,0,0;0,0,0,0,0,0,0,0;0,0,1,0,0,0,1i,0;...
0,0,0,0,0,0,0,0;0,0,0,-1,0,0,0,1i;0,0,0,0,0,0,0,0;0,0,0,1,0,0,0,1i;0,0,0,0,0,0,0,0;...
0,0,1,0,0,0,-1i,0];
X =1/sqrt(2)*Z*[real(layer_x(1,:));real(layer_x(2,:));real(layer_x(3,:));real(layer_x(4,:));...
imag(layer_x(1,:));imag(layer_x(2,:));imag(layer_x(3,:));imag(layer_x(4,:))];
precode_y(1,1:4:4*c-3)=X(1,:);
precode_y(2,1:4:4*c-3)=X(2,:);
precode_y(3,1:4:4*c-3)=X(3,:);
precode_y(4,1:4:4*c-3)=X(4,:);
precode_y(1,2:4:4*c-2)=X(5,:);
precode_y(2,2:4:4*c-2)=X(6,:);
precode_y(3,2:4:4*c-2)=X(7,:);
precode_y(4,2:4:4*c-2)=X(8,:);
precode_y(1,3:4:4*c-1)=X(9,:);
precode_y(2,3:4:4*c-1)=X(10,:);
precode_y(3,3:4:4*c-1)=X(11,:);
precode_y(4,3:4:4*c-1)=X(12,:);
precode_y(1,4:4:4*c)=X(13,:);
precode_y(2,4:4:4*c)=X(14,:);
precode_y(3,4:4:4*c)=X(15,:);
precode_y(4,4:4:4*c)=X(16,:);
D = 0;
W = 0;
U = 0;
end
else % spatial multiplexing
if (AtPorts == 2) % precoding matrix according to Table 6.3.4.2.3-1
switch codebook_index
case 0
if (RI == 2)
W=1/sqrt(2)*[1,0;0,1];
else
W = [1;0];
end
case 1
if (RI == 2)
W=1/(2)*[1,1;1,-1];
else
W = [0;1];
end
case 2
if (RI == 2)
W=1/(2)*[1,1;1i,-1i];
else
W = 1/sqrt(2)*[1;1];
end
case 3
if (RI == 2)
error('codebook index not supported');
else
W = 1/sqrt(2)*[1;-1];
end
case 4
if (RI == 2)
error('codebook index not supported');
else
W = 1/sqrt(2)*[1;1i];
end
case 5
if (RI == 2)
error('codebook index not supported');
else
W = 1/sqrt(2)*[1;-1i];
end
otherwise
error('codebook index not supported');
end
else % precoding matrix according to Table 6.3.4.2.3-2
for i = 1:length(codebook_index) % for open loop spatial multiplexing
% codebook_index = [12,13,14,15]
% see 3GPP TS 36.213-820, Section 7.1.3
% NOTE: store this in some pre-stored variable
switch codebook_index(i)
case 0
u= [1;-1;-1;-1];
case 1
u= [1;-1i;1;1i];
case 2
u= [1;1;-1;1];
case 3
u= [1;1i;1;-1i];
case 4
u= [1;(-1-1i)/sqrt(2); -1i;(1-1i)/sqrt(2)];
case 5
u= [1;(1-1i)/sqrt(2); 1i;(-1-1i)/sqrt(2)];
case 6
u= [1;(1+1i)/sqrt(2); -1i;(-1+1i)/sqrt(2)];
case 7
u= [1;(-1+1i)/sqrt(2); 1i;(1+1i)/sqrt(2)];
case 8
u= [1;-1;1;1];
case 9
u= [1;-1i;-1;-1i];
case 10
u= [1;1;1;-1];
case 11
u= [1;1i;-1;1i];
case 12
u= [1;-1;-1;1];
case 13
u= [1;-1;1;-1];
case 14
u= [1;1;-1;-1];
case 15
u= [1;1;1;1];
otherwise
error('codebook index not supported');
end
W1 = diag(ones(1,4))-2*u*u'/(u'*u);
switch RI
case 1
W = W1(:,1);
case 2
switch codebook_index(i)
case {0,4,5,9}
W(:,:,i) = W1(:,[1 4])/sqrt(2);
case {1,2,3,8,12,15}
W(:,:,i) = W1(:,[1 2])/sqrt(2);
otherwise
W(:,:,i) = W1(:,[1 3])/sqrt(2);
end
case 3
switch codebook_index(i)
case {0,4,5,8}
W(:,:,i) = W1(:,[1 2 4])/sqrt(3);
case {1,2,3,10,12,13,14,15}
W(:,:,i) = W1(:,[1 2 3])/sqrt(3);
otherwise
W(:,:,i) = W1(:,[1 3 4])/sqrt(3);
end
case 4
switch codebook_index(i)
case {0,1,4,5,8,9,12,15}
W(:,:,i) = W1(:,[1 2 3 4])/2;
case {6,7,10,11,13}
W(:,:,i) = W1(:,[1 3 2 4])/2;
otherwise
W(:,:,i) = W1(:,[3 2 1 4])/2;
end
otherwise
error('RI not supported');
end
end
end
switch CDD % cyclic delay diversity, precoding according to Section 6.3.4.2
case 0 % zero delay CDD
D = diag(ones(1,AtPorts));
precode_y = D*W*layer_x;
U = 0;
case 1 % small delay CDD
eta = [128 256 512 1024 2048];
index = find((eta-LTE_params.Nrb*LTE_params.Nsc*ones(1,5))>=0);
n = eta(index(1));
D = zeros(LTE_params.Nsc*length(rb_numbers),AtPorts);
vec = [];
for ii = 1:length(rb_numbers)
if(rb_numbers(ii) > LTE_params.Nrb)
vec =[vec;((rb_numbers(ii)-LTE_params.Nrb-1)*LTE_params.Nsc+1:(rb_numbers(ii)-LTE_params.Nrb)*LTE_params.Nsc).'];
else
vec =[vec;((rb_numbers(ii)-1)*LTE_params.Nsc+1:rb_numbers(ii)*LTE_params.Nsc).'];
end
end
switch AtPorts
case 2
d = 2/n;
D(:,1)=1;
D(:,2) = exp(-1i*2*pi*d*vec);
case 4
d = 1/n;
D(:,1)=1;
D(:,2) = exp(-1i*2*pi*d*vec);
D(:,3) = exp(-1i*2*pi*d*vec*2);
D(:,4) = exp(-1i*2*pi*d*vec*3);
end
precode_y = W*layer_x;
U = 0;
case 2 % large delay CDD
switch RI
case 1
precode_y = W*layer_x;
D =0;
case 2
U = 1/sqrt(2)*[1,1;1,exp(-1i*pi)];
D = [1,0;0,exp(-1i*pi)];
if (AtPorts ==2) % faster encoding (for 2 Antennaports W is not dependent on the time index)
precodey1= W*D*U*layer_x(:,1:2:end);
precodey2= W*D^2*U*layer_x(:,2:2:end);
ende = floor(length(layer_x)/2);
precode_y = reshape([precodey1(:,1:ende);precodey2(:,1:ende)],AtPorts,[]);
if (length(precodey1)>ende)
precode_y=[precode_y,precodey1(:,end)];
end
end
case 3
U = 1/sqrt(3)*[1,1,1;1,exp(-1i*2*pi/3),exp(-1i*4*pi/3);1,exp(-1i*4*pi/3),exp(-1i*8*pi/3)];
D = [1,0,0;0,exp(-1i*2*pi/3),0;0,0,exp(-1i*4*pi/3)];
case 4
U = 1/2*[1,1,1,1;1,exp(-1i*2*pi/4),exp(-1i*4*pi/4),exp(-1i*6*pi/4);...
1,exp(-1i*4*pi/4),exp(-1i*8*pi/4),exp(-1i*12*pi/4);...
1,exp(-1i*6*pi/4),exp(-1i*12*pi/4),exp(-1i*18*pi/4)];
D = [1,0,0,0;0,exp(-1i*2*pi/4),0,0;0,0,exp(-1i*4*pi/4),0;0,0,0,exp(-1i*6*pi/4)];
otherwise
error('RI not supported');
end
if (RI > 1 && AtPorts == 4) % slower encoding version (if W is time dependent)
l = 1:length(layer_x);
k = mod(floor((l-1)/RI),4)+1;
p = mod(l-1,RI)+1;
for i = 1:l(end)
precode_y(:,i) = W(:,:,k(i))*D^(p(i))*U*layer_x(:,i);
end
end
otherwise
error('CDD not supported');
end
end
else % single Antenna Port (SISO)
precode_y = layer_x;
UE.CDD = 0; % no CDD for single antenna transmission
W=1;
D=1;
U = 1;
end
%figure(2)
%plot(precode_y,'x');