UCI和数据复用在pusch上传输（第六部分）---ldpc编码

ldpc编码针对的是上下行数据的编码，也是5G最重要的一种编码。

1 TB块添加CRC

这个是和UCI POLAR区别的一个地方，UCI是对每个cb块添加crc.

% Get transport block size after CRC attachment according to 38.212
% 6.2.1 and 7.2.1, and assign CRC polynomial to CRC field of output
% structure info
if A > 3824
L
= 24;
info.CRC = '24A';
else
L
= 16;
info.CRC = '16';
end
**此处会对TB块进行crc的添加，具体添加crc的过程已经在上一篇文章
《UCI和数据复用在pusch上传输（第五部分）---polar编码》分享过了，
这里就不在做复述。**

2 graph选择

% LDPC base graph selection
if A <= 292 || (A <= 3824 && R <= 0.67) || R <= 0.25
bgn = 2;
else
bgn = 1;
end

3 cb块分段和cb块添加crc

具体添加crc的过程已经在上一篇文章
《UCI和数据复用在pusch上传输（第五部分）—polar编码》分享过了，
这里就不在做复述。

% Get the maximum code block size
if bgn == 1
Kcb = 8448;
else
Kcb = 3840;
end
% Get number of code blocks and length of CB-CRC coded block
if B <= Kcb
L = 0;
C = 1;
Bd = B;
else
L = 24; % Length of the CRC bits attached to each code block
C = ceil(B/(Kcb-L));
Bd = B+C*L;
end
% Obtain the number of bits per code block (excluding CB-CRC bits)
cbz = ceil(B/C);
% Get number of bits in each code block (excluding filler bits)
Kd = ceil(Bd/C);
% Find the minimum value of Z in all sets of lifting sizes in 38.212
% Table 5.3.2-1, denoted as Zc, such that Kb*Zc>=Kd
if bgn == 1
Kb = 22;
else
if B > 640
Kb = 10;
elseif B > 560
Kb = 9;
elseif B > 192
Kb = 8;
else
Kb = 6;
end
end
Zlist = [2:16 18:2:32 36:4:64 72:8:128 144:16:256 288:32:384];
Zc =
min(Zlist(Kb*Zlist >= Kd));
% Get number of bits (including <NULL> filler bits) to be input to the LDPC
% encoder
if bgn == 1
K = 22*Zc;
%这块为啥一定要是Zc的倍数，这个是个问题？
else
K = 10*Zc;
end

4 UL_SCH的通道编码（这是编码最难的部分需要进一步搞清楚）

% Get lifting set number
ZSets = {[2
4
8
16
32
64 128 256],... % Set 1
[3
6 12
24
48
96 192 384],... % Set 2
[5 10 20
40
80 160 320],...
% Set 3
[7 14 28
56 112 224],...
% Set 4
[9 18 36
72 144 288],...
% Set 5
[11 22 44
88 176 352],...
% Set 6
[13 26 52 104 208],...
% Set 7
[15 30 60 120 240]};
% Set 8
for setIdx = 1:8
% LDPC lifting size set index
if any(Zc==ZSets{setIdx})
break;
end
end
% Pre-stored H types for each BGN and setIdx pair
% 这个是怎么来的不知道，需要进一步看看
Htype = {3, 3, 3, 3, 3, 3, 2, 3;
4, 4, 4, 1, 4, 4, 4, 1};
% Get the matrix with base graph number 'bgn' and set number 'setIdx'.
% The element of matrix V in the following is H_BG(i,j)*V(i,j), where
% H_BG(i,j) and V(i,j) are defined in TS 38.212 5.3.2; if V(i,j) is not
% defined in Table 5.3.2-2 or Table 5.3.2-3, the elements are -1.
% %这个就是协议中的v_ij
switch bgn
case 1
switch setIdx
case 1
V = bgs.BG1S1;
case 2
V = bgs.BG1S2;
case 3
V = bgs.BG1S3;
case 4
V = bgs.BG1S4;
case 5
V = bgs.BG1S5;
case 6
V = bgs.BG1S6;
case 7
V = bgs.BG1S7;
otherwise % 8
V = bgs.BG1S8;
end
Nplus2Zc = Zc*(66+2);
otherwise % bgn = 2
switch setIdx
case 1
V = bgs.BG2S1;
case 2
V = bgs.BG2S2;
case 3
V = bgs.BG2S3;
case 4
V = bgs.BG2S4;
case 5
V = bgs.BG2S5;
case 6
V = bgs.BG2S6;
case 7
V = bgs.BG2S7;
otherwise % 8
V = bgs.BG2S8;
end
Nplus2Zc = Zc*(50+2);%为啥要求这和？
end
P = nr5g.internal.ldpc.calcShiftValues(V,Zc);%根据V和Zc得到P P=mod(V,Zc)
% The element of matrix P in the following is P(i,j) in TS 38.212 5.3.2
% when V(i,j) are defined in Table 5.3.2-2 or Table 5.3.2-3. If not
% defined, the elements are -1.
P = zeros(size(V));
for i = 1:size(V,1)
for j = 1:size(V,2)
if V(i,j) == -1
P(i,j) = -1;
else
P(i,j) = mod(V(i,j),Z);
end
end
end
P1 = P(:,1:(size(P,2) - size(P,1)));%取了P的前面（52-42）或者（67-45）行，为啥要取这个？
C = size(infoBits,2); %获取层数
codewords = zeros(Nplus2Zc,C);
% Get shift values matrix
P = nr5g.internal.ldpc.calcShiftValues(V,Zc);
P1 = P(:,1:(size(P,2) - size(P,1)));
C = size(infoBits,2);
codewords = zeros(Nplus2Zc,C);
for r = 1:C
% Per code-block processing only
infoVec = reshape(infoBits(:,r),Zc,[]);%将信息bit（协议中的C_k）变成Zc行，K/Zc列。
d = blockMultiply(P1,infoVec);
d0 = d(:,1:4);
% Solve 4 equations for Htype * m = d0
switch Htype{bgn,setIdx}
case 1
% H1 = [
1
0 -1 -1;
%
-1
0
0 -1;
%
0 -1
0
0;
%
1 -1 -1
0 ];
m1 = sum(d0, 2);
m2 = d0(:,1) + m1([2:end 1]);
m3 = d0(:,2) + m2;
m4 = d0(:,3) + m1 + m3;
case 2
% H2 = [
0
0 -1 -1;
%
105
0
0 -1;
%
-1 -1
0
0;
%
0 -1 -1
0 ];
m1 = sum(d0, 2);
shift = mod(105, Zc);
if shift > 0
m1 = m1([(end-shift+1):end 1:(end-shift)]);
end
m2 = d0(:,1) + m1;
m4 = d0(:,4) + m1;
m3 = d0(:,3) + m4;
case 3
% H3 = [
1
0 -1 -1;
%
0
0
0 -1;
%
-1 -1
0
0;
%
1 -1 -1
0 ];
m1 = sum(d0, 2);
m2 = d0(:,1) + m1([2:end 1]);
m3 = d0(:,2) + m1 + m2;
m4 = d0(:,3) + m3;
otherwise % == 4
% H4 = [
0
0 -1 -1;
%
-1
0
0 -1;
%
1 -1
0
0;
%
0 -1 -1
0 ];
m1 = sum(d0, 2);
m1 = m1([end 1:(end-1)]);
m2 = d0(:,1) + m1;
m3 = d0(:,2) + m2;
m4 = d0(:,4) + m1;
end
% Get other parity bits
P3 = P(5:end,size(P1,2)+(1:4));
p = blockMultiply(P3, [m1 m2 m3 m4]) + d(:,5:end);
% Form codeword and assign to output
codewords(:,r) = [infoBits(:,r); mod([m1; m2; m3; m4; p(:)],2)];
end
end

5 速率匹配

% Get code block soft buffer size
if ~isempty(Nref)
fcnName = 'nrRateMatchLDPC';
validateattributes(Nref, {'numeric'}, ...
{'scalar','integer','positive'},fcnName,'NREF');
Ncb = min(N,Nref);
else
% No limit on buffer size
Ncb = N;
end
% Get starting position in circular buffer
if bgn == 1
if rv == 0
k0 = 0;
elseif rv == 1
k0 = floor(17*Ncb/N)*Zc;
elseif rv == 2
k0 = floor(33*Ncb/N)*Zc;
else % rv is equal to 3
k0 = floor(56*Ncb/N)*Zc;
end
else
if rv == 0
k0 = 0;
elseif rv == 1
k0 = floor(13*Ncb/N)*Zc;
elseif rv == 2
k0 = floor(25*Ncb/N)*Zc;
else % rv is equal to 3
k0 = floor(43*Ncb/N)*Zc;
end
end
% Get rate matching output for all scheduled code blocks and perform
% code block concatenation according to Section 5.4.2 and 5.5
out = [];
for r = 0:C-1
if r <= C-mod(outlen/(nlayers*Qm),C)-1
E = nlayers*Qm*floor(outlen/(nlayers*Qm*C));
else
E = nlayers*Qm*ceil(outlen/(nlayers*Qm*C));
end
out = [out; cbsRateMatch(in(:,r+1),E,k0,Ncb,Qm)]; %#ok<AGROW>
end
end
function e = cbsRateMatch(d,E,k0,Ncb,Qm)
% Rate match a single code block segment as per TS 38.212 Section 5.4.2
% Bit selection, Section 5.4.2.1
k = 0;
j = 0;
e = zeros(E,1,class(d));
while k < E
if d(mod(k0+j,Ncb)+1) ~= -1
% Filler bits
e(k+1) = d(mod(k0+j,Ncb)+1);
k = k+1;
end
j = j+1;
end
% Bit interleaving, Section 5.4.2.2
e = reshape(e,E/Qm,Qm);
e = e.';
e = e(:);
end

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