www.gusucode.com > LTE基带收发仿真系统matlab源码程序 > LTE baseband simulation/de_precoding.m
function recLayerSymb = de_precoding(recPrecodedSymb,HfreqCell,iUE,SNRdB)
% 功能：根据估计的信道矩阵和发端预编码向量，计算等效的信道，并是用MMSE、ZF算法估计发送信号
% 输入：
% recPrecodedSymb：接收的预编码符号
% HfreqCell：信道的频域矩阵
% iUE：第i个用户
% SNRdB：信噪比，dB表示
% 输出：
% recLayerSymb：解预编码的输出，得到每一层的符号
%
% Author: 程式小组（徐萌 张妙 张晓庆）
% Date: 2010-07-11
% ==============================================
global LTE_par
nTx = LTE_par.BS_par.nAnt;
nRx = LTE_par.UE_par.nAnt;
CFI = LTE_par.CFI;
scPerRB = LTE_par.scPerRB;
nOfdmSymb = LTE_par.nOfdmSymb;
nRB = LTE_par.UE_par.nRB(iUE);
M_0_SYMB = LTE_par.UE_par.M_0_SYMB(iUE);
cellID = LTE_par.BS_par.cellID; % 小区ID号
iSubFrame = LTE_par.iSubFrame; % 当前子帧号 取值为0~9
ns = iSubFrame*2; % 时隙号
nLayer = LTE_par.UE_par.nLayer(iUE); % 层数
detecAlg = LTE_par.UE_par.detecAlg; % MIMO检测算法 'MMSE' 或 'ZF'
% 预处理模式
% - 'singleAnt'：单天线
% - 'spatialMultiplexing'：空间复用
% - 'tranmitDiversity'： 传输分集
preProcess = LTE_par.UE_par.preProcess;
% ============== 测试使用 =================================
% nTx = 1;
% CFI = 2;
% scPerRB = 12;
% nOfdmSymb = 14;
% nRB = 5;
% M_0_SYMB = 660;
% cellID = 0;
% ns = 2;
% ===========================================================
nSubCarr = nRB*scPerRB; % 第iUE个用户占用的子载波数
% 导频占用位置
pilotLocation = find_pilot(cellID,nTx,scPerRB,nOfdmSymb,nRB,ns);
if strcmp(preProcess,'singleAnt')
% 单天线情形下的频域均衡
% 经过时域或频域信道时，接收端进行频域均衡
recLayerSymb = zeros(nLayer,M_0_SYMB);
iSymb = 1;
for iOfdm = CFI+1:nOfdmSymb
for iCarr = 1:nSubCarr
if pilotLocation(iCarr,iOfdm) == 0
r = zeros(nRx,1); % 载波上接收符号
H = HfreqCell{iCarr}; % 载波上的信道矩阵
for iRx = 1:nRx
r(iRx) = recPrecodedSymb{iRx}(iCarr,iOfdm);
end
if strcmp(detecAlg,'MMSE')
xEst = mmse_detect(r,H,SNRdB); % MMSE检测
elseif strcmp(detecAlg,'ZF')
xEst = zf_detect(r,H); % ZF检测
end
recLayerSymb(:,iSymb) = xEst;
iSymb = iSymb+1;
end
end
end
elseif strcmp(preProcess,'spatialMultiplexing')
recLayerSymb = zeros(nLayer,M_0_SYMB);
%载入预编码码本 W_SM_2Tx（2天线码本）和W_SM_4Tx（4天线码本）
load CodeBook
% 第iUE个用户预编码序号
PMI = LTE_par.UE_par.PMI(iUE);
% 2天线端口配置，空间复用的码本大小：2*2*8 W_SM_2Tx
% 4天线端口配置，空间复用的码本大小：4*4*64 W_SM_4Tx
% 码本使用举例 W_SM_4Tx(:,1:3,33) 第一维表示天线数 第二维表示层数 第三维表示属于层3的第2个码字
PMI = PMI+1+(nLayer-1)*2^nTx;
if nTx == 2
iSymb = 1;
for iOfdm = CFI+1:nOfdmSymb
for iCarr = 1:nSubCarr
if pilotLocation(iCarr,iOfdm) == 0
% 载波上的信道矩阵
H = HfreqCell{iCarr};
% 实际信道矩阵乘以预编码，得到等效信道
W = W_SM_2Tx(:,1:nLayer,PMI);
Heq = H*W;
% 载波上接收符号
r = zeros(nRx,1);
for iRx = 1:nRx
r(iRx) = recPrecodedSymb{iRx}(iCarr,iOfdm);
end
if strcmp(detecAlg,'MMSE')
xEst = mmse_detect(r,Heq,SNRdB); % MMSE检测
elseif strcmp(detecAlg,'ZF')
xEst = zf_detect(r,H); % ZF检测
end
recLayerSymb(:,iSymb) = xEst;
iSymb = iSymb+1;
end
end
end
elseif nTx == 4
iSymb = 1;
for iOfdm = CFI+1:nOfdmSymb
for iCarr = 1:nSubCarr
if pilotLocation(iCarr,iOfdm) == 0
% 载波上的信道矩阵
H = HfreqCell{iCarr};
% 实际信道矩阵乘以预编码，得到等效信道
W = W_SM_4Tx(:,1:nLayer,PMI);
Heq = H*W;
% 载波上接收符号
r = zeros(nRx,1);
for iRx = 1:nRx
r(iRx) = recPrecodedSymb{iRx}(iCarr,iOfdm);
end
if strcmp(detecAlg,'MMSE')
xEst = mmse_detect(r,Heq,SNRdB); % MMSE检测
elseif strcmp(detecAlg,'ZF')
xEst = zf_detect(r,H); % ZF检测
end
recLayerSymb(:,iSymb) = xEst;
iSymb = iSymb+1;
end
end
end
end
elseif strcmp(preProcess,'tranmitDiversity')
if nTx == 2
iSymb = 1;
recLayerSymb = zeros(nLayer,M_0_SYMB/2);
for iOfdm = CFI+1:nOfdmSymb
availableDataCarr = find(pilotLocation(:,iOfdm)==0); % 得到第iOfdm个OFDM符号上数据可用载波
len = length(availableDataCarr);
groupSize = 2; % 一组SFBC 编码占用的载波数
for iGroup = 1:2:len
tempPre = zeros(groupSize*nTx,1); % 存放相邻两个载波上的取MIMO估计符号
for itd = 1:groupSize
% 提取载波上符号,信道
r = zeros(nRx,1);
for iRx = 1:nRx
r(iRx) = recPrecodedSymb{iRx}(availableDataCarr(iGroup+itd-1),iOfdm);
end
H = HfreqCell{availableDataCarr(iGroup+itd-1)};
if strcmp(detecAlg,'MMSE')
xEst = mmse_detect(r,H,SNRdB); % MMSE检测
elseif strcmp(detecAlg,'ZF')
xEst = zf_detect(r,H); % ZF检测
end
tempPre((itd-1)*nTx+1:itd*nTx) = xEst;
end
U = sqrt(2)*[1 0 0 1;0 -1 1 0;1 0 0 -1;0 1 1 0]; % ZF MMSE下去预编码矩阵
tempPre = U*tempPre;
tempPre = tempPre/2;
iLayerSymb = [real(tempPre(1))+1i*imag(tempPre(3));real(tempPre(2))+1i*imag(tempPre(4))];
recLayerSymb(:,iSymb) = iLayerSymb;
iSymb = iSymb+1;
end
end
elseif nTx == 4
if mod(M_0_SYMB,4) ~= 0
recLayerSymb = zeros(nLayer,(M_0_SYMB+2)/4);
else
recLayerSymb = zeros(nLayer,M_0_SYMB/4);
end
iSymb = 1;
for iOfdm = CFI+1:nOfdmSymb
availableDataCarr = find(pilotLocation(:,iOfdm)==0); % 得到第iOfdm个OFDM符号上数据可用载波
len = length(availableDataCarr);
groupSize = 4; % 一组SFBC 编码占用的载波数
for iGroup = 1:4:len
tempPre = zeros(groupSize*nTx,1); % 存放相邻两个载波上的取MIMO估计符号
for itd = 1:groupSize
% 提取载波上符号,信道
r = zeros(nRx,1);
for iRx = 1:nRx
r(iRx) = recPrecodedSymb{iRx}(availableDataCarr(iGroup+itd-1),iOfdm);
end
xEst = zeros(1,groupSize);
if itd<=2;
H = HfreqCell{availableDataCarr(iGroup+itd-1)}(:,[1 3]);
if strcmp(detecAlg,'MMSE')
xEst([1 3]) = mmse_detect(r,H,SNRdB); % MMSE检测
elseif strcmp(detecAlg,'ZF')
xEst([1 3]) = zf_detect(r,H); % ZF检测
end
else
H = HfreqCell{availableDataCarr(iGroup+itd-1)}(:,[2 4]);
if strcmp(detecAlg,'MMSE')
xEst([2 4]) = mmse_detect(r,H,SNRdB); % MMSE检测
elseif strcmp(detecAlg,'ZF')
xEst([2 4]) = zf_detect(r,H); % ZF检测
end
end
tempPre((itd-1)*nTx+1:itd*nTx) = xEst;
end
U = sqrt(2)*[1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0;
0 0 -1 0 1 0 0 0 0 0 0 0 0 0 0 0;
0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1;
0 0 0 0 0 0 0 0 0 0 0 -1 0 1 0 0;
1 0 0 0 0 0 -1 0 0 0 0 0 0 0 0 0;
0 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0;
0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 -1;
0 0 0 0 0 0 0 0 0 0 0 1 0 1 0 0];% ZF MMSE下去预编码矩阵
tempDepre = U*tempPre;
tempDepre = tempDepre/2;
iLayerSymb = real(tempDepre(1:4))+1i*imag(tempDepre(5:8));
recLayerSymb(:,iSymb) = iLayerSymb;
iSymb = iSymb+1;
end % end for SFBC解码组
end % end for ofdm符号循环
end % end if 发端天线数判断
end % end if 预处理模式判断