www.gusucode.com > MC-CDMA系统的仿真matlab源码程序 > mc-cdma/rayleigh(移动信道)/preamble.m
% 清除内存，计时开始 5径瑞利信道 %jakes
clear
tic;
%设置参数
totalframe=1; %帧长
totalwords=totalframe*100*12;%每帧60个数据符号，每个符号里12个用户数据
%numsymb=totalframe*64;%每帧共64个符号，4个导频符号，60个数据符号
numusers=1;
wordsize=2;
linktype=0; %上行链路
NumCarr=256;
procgain=16; %扩频码的长度
guardtime=64;
guardtype=2;
frameguard=NumCarr+guardtime; % Guard Time between successive frames (one symbol period)
Fc = 900e+06; % carrier frequency (Hz) --> ISM band
wc = 2*pi*Fc; % carrier frequency (rad/sec)
V = 3000/3600; % mobile speed (= 3 Km/hr) in m/sec
N0 = 24; % The number of paths
lambda = 3e+08/Fc; % wavelength at Fc
Fm = V/lambda % Doppler shift
Fs = 8*Fm; % sampling frequency
M = 10000; % number of samples
paths = 16;
Ts = 1/Fs; % sampling period
t = [0:Ts:(M-1)*Ts]; % time array
fading = jakes(Fm,Fs,M,N0,paths);
% 产生要发送的双极性二进制随机数
seed=1234;
rand('seed',seed); % Set to new seed
seqnumlist = randperm(procgain);
Datatx = zeros(numusers,totalwords);
RxSignal0=zeros(1,totalwords*procgain);
for k = 1:numusers,
Datatx(k,:)=floor(rand(1,totalwords)*2^wordsize);%产生2^wordsize进制发送数据
%进行映射
mapping=get80216map(2^wordsize);
B=Datatx(k,:);
for i=1:length(B),
Datatx1(i)=mapping(1+B(i));
end;
seqnum=seqnumlist(k);%取得用户k的扩频码
%扩频
basesignal_0=tranCDMA(Datatx1,procgain,seqnum,linktype);
% 插入帧头
w1=floor(rand(256,4)*4); %第一个用户的4个帧头
for i=1:(size(w1,1)*size(w1,2))
w1(i)=mapping(1+w1(i));
end;
pm=zeros(256,4); %4个用户，每列一个用户的导频
for m=1:NumCarr
pm(m,:)=w1(m,:)*exp(-j*2*pi*(k-1)*guardtime*(m-1)/NumCarr);
end;
pm(:,2)=pm(:,2)*sqrt(2);
pm(:,4)=pm(:,4)*2;
numsymb = ceil(length(basesignal_0)/200);
%如果传输的数据不是数据载波的整数倍，则在后面补零
if length(basesignal_0)/200 ~= numsymb,
DataPad = zeros(1,numsymb*200);
DataPad(1:length(basesignal_0)) = basesignal_0;
basesignal_0 = DataPad;
end
clear DataPad;
%ofdm调制
%=============
% 每载波要传输多少数据
%=============
%生成数据和导频图案
numsymb=numsymb+4*totalframe;
Pattern=ones(NumCarr,numsymb); % the position of data is set as 1.
Pattern(129,:)=0; % DC=0
Pattern([1:28,230:256],:)=0; % guard band=0
Pattern(:,[1:4])=0;
Data_Pattern=find(Pattern==1); %the pattern of data
Data=zeros(size(Pattern));
Data(Data_Pattern)=basesignal_0; %插入用户数据
Data(:,1)=pm(:,1);
Data(:,2)=pm(:,2);
Data(:,3)=pm(:,3);
Data(:,4)=pm(:,4);
%==================================
%Find the time waveform using IFFT
%==================================
BaseSignal = ifft(Data); %ifft是对列进行ifft变换。
%=================================
%Add a Guard Period
%=================================
BaseSignal=[BaseSignal((end-guardtime+1):end,:); BaseSignal];
%BaseSignal = reshape(BaseSignal0,1,size(BaseSignal0,1)*size(BaseSignal0,2)); %先取第一列，再取第二列，……
%===============
% CHANNEL MODEL， channel have delay
%===============
fc=3.5e9;
V=5; %V km/h
fdmax=V*fc/3e8/3.6 %fmax=V*fc/C
fade=Rayleigh(fdmax);
path1=ones(frameguard,1)*fade(1,[1+1000:numsymb+1000]).*BaseSignal;
path2=ones(frameguard,1)*fade(2,[1+1000:numsymb+1000]).*BaseSignal;
path3=ones(frameguard,1)*fade(3,[1+1000:numsymb+1000]).*BaseSignal;
path4=ones(frameguard,1)*fade(4,[1+1000:numsymb+1000]).*BaseSignal;
path5=ones(frameguard,1)*fade(5,[1+1000:numsymb+1000]).*BaseSignal;
path6=ones(frameguard,1)*fade(6,[1+1000:numsymb+1000]).*BaseSignal;
path01=reshape(path1,1,size(path1,1)*size(path1,2));
path02=reshape(path2,1,size(path2,1)*size(path2,2));
path03=reshape(path3,1,size(path3,1)*size(path3,2));
path04=reshape(path4,1,size(path4,1)*size(path4,2));
path05=reshape(path5,1,size(path5,1)*size(path5,2));
path06=reshape(path6,1,size(path6,1)*size(path6,2));
%the delay is [0 0.31 0.71 1.09 1.73] us,[0 2 3 5 7]; % time delay spread(in sample) of each path
path11=[path01 zeros(1,10)]; % the largest delay is 10 sample
path12=[zeros(1,1) path02 zeros(1,9)];
path13=[zeros(1,3) path03 zeros(1,7) ];
path14=[zeros(1,4) path04 zeros(1,6)];
path15=[zeros(1,7) path05 zeros(1,3)];
path16=[zeros(1,10) path06];
RxSignal00=path11+path12+path13+path14+path15+path16;
RxSignal1=RxSignal00(1:length(path01));
RxSignal0=RxSignal1+RxSignal0;
end;
H_real=zeros(NumCarr,numsymb); % the real channel impulse response
for k=1:NumCarr
H_real(k,:)=H_real(k,:)+fade(1,[1+1000:numsymb+1000])*exp(-j*2*pi*(k-1)*0/NumCarr)+fade(2,[1+1000:numsymb+1000])*exp(-j*2*pi*(k-1)*1/NumCarr)+...
fade(3,[1+1000:numsymb+1000])*exp(-j*2*pi*(k-1)*3/NumCarr)+fade(4,[1+1000:numsymb+1000])*exp(-j*2*pi*(k-1)*4/NumCarr)+...
fade(5,[1+1000:numsymb+1000])*exp(-j*2*pi*(k-1)*7/NumCarr)+fade(6,[1+1000:numsymb+1000])*exp(-j*2*pi*(k-1)*10/NumCarr);
end
ber1=[];
ber2=[];
ber3=[];
berreal=[];
mse1=[];
mse2=[];
mse3=[];
for SNR=0:5:30
RxSignal=awgn(RxSignal0,10^(SNR/10),'measured',1234,'linear');
%==================
% RECEIVER SECTION
%==================
% remove cyclic prefix
symbwaves=reshape(RxSignal,frameguard,numsymb);
symbwaves = symbwaves(guardtime+1:frameguard,:); % Strip off the guard interval
%fft变换
Yf=fft(symbwaves);
%=======================================Estimation===============================================
PL=repmat(pm(:,2),1,numsymb);
Htotal=Yf./PL;
htotal=ifft(Htotal);
hl=htotal;
HL=fft(hl);
mse1=[mse1,mse(abs(H_real-HL))]
Rx1=Yf;
Rxreal=Yf;
Rx1=Rx1./HL;
Rxreal=Rxreal./H_real;
DemSig1=Rx1(Data_Pattern);
DemSigreal=Rxreal(Data_Pattern);
DemSignal1=reshape(DemSig1,1,size(DemSig1,1)*size(DemSig1,2)); %用户1估计值
DemSignalreal=reshape(DemSigreal,1,size(DemSigreal,1)*size(DemSigreal,2));%理想估计值
%解扩
subsignal1=[];
subsignalreal=[];
for k=1:numusers
seqnum = seqnumlist(k);
[data10,subsignal10]=recCDMA(DemSignal1,procgain,seqnum,linktype);
subsignal1=[subsignal1;subsignal10];
[datareal0,subsignalreal0]=recCDMA(DemSignalreal,procgain,seqnum,linktype);
subsignalreal=[subsignalreal;subsignalreal0];
end
%去掉映射
Datarx1=invmapping(subsignal1,mapping,wordsize);
Datarxreal=invmapping(subsignalreal,mapping,wordsize);
%计算误码率
ber10=err(Datatx,Datarx1,totalwords,numusers);
berreal0=err(Datatx,Datarxreal,totalwords,numusers)
ber1=[ber1,ber10]
berreal=[berreal,berreal0]
end;
figure
subplot(2,2,1)
k=0:5:30
semilogy(k,ber1,'-rh')
hold on
semilogy(k,berreal,'-.b')
grid on
axis([0 30 10^(-3) 1])
xlabel('SNR/dB'),ylabel('BER')
legend('用户1','理想')
set (gcf,'color',[1 1 1])
set(gca,'xtick',[0:5:30])
subplot(2,2,2)
k=0:5:30
semilogy(k,mse1,'-rh')
grid on
axis([0 30 10^(-3) 1])
xlabel('SNR/dB'),ylabel('MSE')
set (gcf,'color',[1 1 1])
set(gca,'xtick',[0:5:30])
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