DSP OFDM原理实现实验.docx
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DSP OFDM原理实现实验.docx
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DSPOFDM原理实现实验
实验:
OFDM原理与实现
一、实验内容
学习CP-OFDM实现代码
•实现CP-SCFDE
•实现ZP-OFDM
•实现ZP-SCFDE
•比较分析四种技术的识码率性能
• 分析ZP-OFDM/SCFDE两种方案的复杂度
• 探讨是否有降低ZP-OFDM与ZP-SCFDE均衡复杂
的可能性(选做)
1、学习CP-OFDM实现代码
(1)代码
N=256;%载波数,i.e.,fftsize
Ncp=N/4;%循环前缀的长度
Ns=N+Ncp;%每个OFDM符号的整个长度
Ntry=100;%OFDM帧的数量
Nsyb=20;%每帧的OFDM符号的数目
M=16;%M-aryQAM
m=log2(M);%mbitspersubcarrier
Pav=2*(M-1)/3.0;%每个子载波的平均功率
PavdB=10*log10(Pav/N);%时间信号的分贝平均值
SNRdB=[0:
5:
40];%SNRlisttobesimulated
%Setmulti-pathfadingchannelparameters
Np=Ncp/4;%Thenumberofmultipaths
%idxTaps=sort(randperm(Ncp,Np));%Aftermatlab2012a
idxTaps=randperm(Ncp);%beforematlab2012a
idxTaps=sort(idxTaps(1:
Np));%beforematlab2012a
idxTaps-idxTaps
(1)+1;%Movethefirstmultipathto0delay
DPS=exp(-3*idxTaps/Ncp);%powerineachtap:
DelayPowerSpectrum
DPS=DPS/sum(DPS);%Normalize
Ampath=sqrt(DPS);%Amplitudeofeachpath
%%DirectlyuseMatlabchannelobject
%SymbolRate=20e6;%SamplingRate
%Ts=1/SymbolRate;%Symbolperiod
%Tau=(idxTaps-1)*Ts;%tapdelayins
%PdB=10*log10(DPS);%DelayPowerSpectrumindB
%Fdop=0;%Quasi-staticchannels
%ch=rayleighchan(Ts,Fdop,Tau,PdB);
%ch.StorePathGains=1;%Flagtostorepathgain
hzero=zeros(Ncp,1);%zerovectorforchannelimpulseresponse
ErrSymbols=zeros(size(SNRdB));%storethenumberoftheerrorsymbols
tic%theinstantbeginsimulation
fornumSimSymbols=1:
Ntry
curErrSymbols=0;
%Step1:
Generaterandomdigitalmessage
d=randi([0,M-1],N,Nsyb);%Messagesignal
%Step2:
M-QAMmodulation.
X=qammod(d,M);
%Step3:
IFFT,generatetimefieldsignal,
%i.e.,modulateatfrequencyField,
x=ifft(X);
%Step4:
Ìí¼ÓÑ»·Ç°×º
xcp=[x(N-Ncp+1:
end,:
);x];
%Serialize
xcp=xcp(:
);
%Step5a:
TransmitthroughChannel
%MannullyGeneratemultipathchannelimpulseresponse
cir=Ampath.*(randn(1,Np)+1j*randn(1,Np))/sqrt
(2);
h=hzero;h(idxTaps)=cir.';%storechannel
%Channeleffect
xcpch=zeros(Ns*Nsyb+Ncp,1);
forp=1:
Np
idx=[0:
Ns*Nsyb-1]+idxTaps(p);
xcpch(idx)=xcpch(idx)+cir(p)*xcp;
end
xcpch=xcpch(1:
Ns*Nsyb);
%CanalsouseMatlabchanelobject
%xcpch=filter(ch,xcp);
%h=hzero;h(idxTaps)=ch.PathGains;%Savechannel
fork=1:
length(SNRdB)
%Step5b:
AWGN
y=awgn(xcpch,SNRdB(k),'measured');%PavdB);
%Step6:
DeleteCP
y=reshape(y,[Ns,Nsyb]);
y=y([Ncp+1:
end],:
);
%Step7:
FFT,ComebacktoFrequencyField
Y=fft(y);
%Step8:
Frequencydomainequalization
HCP=fft(h,N);%ChannelFrequencyResponseofPrefectchannel
Gzf=1./HCP;%Zero-ForcingEqualizer
Xhat=Y.*repmat(Gzf,[1,Nsyb]);
%Step9:
Demodulate,torecoverthemessage.
dhat=qamdemod(Xhat,M);
%Step10:
Computesymbolerrorrate.
ddif=d-dhat;ddif=ddif(:
);
curErrSymbols=length(find(ddif~=0));
ErrSymbols(k)=ErrSymbols(k)+curErrSymbols;
end
end
toc%simulationtime
%Step10:
Showsimulationresults
cpSER=ErrSymbols/(N*Nsyb*Ntry);
%TheorySERofM-aryQAMinflatFadingChannel
SNR=10.^(SNRdB/10);
EbNo=10*log10(SNR/m);
[thyBER,thySER]=berfading(EbNo,'qam',M,1)
figure;semilogy(SNRdB,[cpSER;thySER],'-o');
xlabel('SNRdB');ylabel('Symbolerrorratio(SER)');
legend('SimulatedCP-OFDMinmultipathfading','TheoreticalM-QAMinflatfading');gridon;
(2)结果
(3)分析
cp-ofdm技术的误码率与理论计算结果基本一致。
2、实现CP-SCFDE
(1)代码
%Programcp_scfde
N=256;%Thenumberofthesubcarriers,i.e.,fftsize
Ncp=N/4;%thelengthofthecyclicprefix
Ns=N+Ncp;%ThewholelengthofeachOFDMsymbol
Ntry=100;%ThenumberofOFDMFrametosimulateperSNRvalue
Nsyb=20;%ThenumberofOFDMsymbolsperframe
M=16;%M-aryQAM
m=log2(M);%mbitspersubcarrier
Pav=2*(M-1)/3.0;%averagepowerofeachsubcarrier
PavdB=10*log10(Pav/N);%averagepoweroftimesignalindBforOFDM
SNRdB=[0:
5:
40];%SNRlisttobesimulated
%Setmulti-pathfadingchannelparameters
Np=Ncp/4;%Thenumberofmultipaths
%idxTaps=sort(randperm(Ncp,Np));%Aftermatlab2012a
idxTaps=randperm(Ncp);%beforematlab2012a
idxTaps=sort(idxTaps(1:
Np));%beforematlab2012a
idxTaps-idxTaps
(1)+1;%Movethefirstmultipathto0delay
DPS=exp(-3*idxTaps/Ncp);%powerineachtap:
DelayPowerSpectrum
DPS=DPS/sum(DPS);%Normalize
Ampath=sqrt(DPS);%Amplitudeofeachpath
hzero=zeros(Ncp,1);%zerovectorforchannelimpulseresponse
ErrSymbols=zeros(size(SNRdB));%storethenumberoftheerrorsymbols
tic%theinstantbeginsimulation
fornumSimSymbols=1:
Ntry
curErrSymbols=0;
%Step1:
Generaterandomdigitalmessage
d=randi([0,M-1],N,Nsyb);%Messagesignal
%Step2:
M-QAMmodulation.
%X=qammod(d,M);
x=qammod(d,M);
%Step3:
IFFT,generatetimefieldsignal,
%i.e.,modulateatfrequencyField,
%x=ifft(X);
%Step4:
Ìí¼ÓÑ»·Ç°×º
xcp=[x(N-Ncp+1:
end,:
);x];
%Serialize
xcp=xcp(:
);
%Step5a:
TransmitthroughChannel
%MannullyGeneratemultipathchannelimpulseresponse
cir=Ampath.*(randn(1,Np)+1j*randn(1,Np))/sqrt
(2);
h=hzero;h(idxTaps)=cir.';%storechannel
%Channeleffect
xcpch=zeros(Ns*Nsyb+Ncp,1);
forp=1:
Np
idx=[0:
Ns*Nsyb-1]+idxTaps(p);
xcpch(idx)=xcpch(idx)+cir(p)*xcp;
end
xcpch=xcpch(1:
Ns*Nsyb);
%CanalsouseMatlabchanelobject
%xcpch=filter(ch,xcp);
%h=hzero;h(idxTaps)=ch.PathGains;%Savechannel
fork=1:
length(SNRdB)
%Step5b:
AWGN
y=awgn(xcpch,SNRdB(k),'measured');%PavdB);
%Step6:
DeleteCP
y=reshape(y,[Ns,Nsyb]);
y=y([Ncp+1:
end],:
);
%Step7:
FFT,ComebacktoFrequencyField
Y=fft(y);
%Step8:
Frequencydomainequalization
HCP=fft(h,N);%ChannelFrequencyResponseofPrefectchannel
Gzf=1./HCP;%Zero-ForcingEqualizer
Xhat=Y.*repmat(Gzf,[1,Nsyb]);
xhat=ifft(Xhat);
%Step9:
Demodulate,torecoverthemessage.
dhat=qamdemod(xhat,M);
%Step10:
Computesymbolerrorrate.
ddif=d-dhat;ddif=ddif(:
);
curErrSymbols=length(find(ddif~=0));
ErrSymbols(k)=ErrSymbols(k)+curErrSymbols;
end
end
toc%simulationtime
%Step10:
Showsimulationresults
cpSER=ErrSymbols/(N*Nsyb*Ntry);
%TheorySERofM-aryQAMinflatFadingChannel
SNR=10.^(SNRdB/10);
EbNo=10*log10(SNR/m);
[thyBER,thySER]=berfading(EbNo,'qam',M,1);
figure;semilogy(SNRdB,[cpSER;thySER],'-o');
xlabel('SNRdB');ylabel('Symbolerrorratio(SER)');
legend('SimulatedCPSCFDEinmultipathfading','TheoreticalM-QAMinflatfading');gridon;
(2)结果
(3)分析
cp-scfde技术相对于理论结果有较大的差别,而相对于cp-ofdm其误码率要低。
3、实现ZP-OFDM
(1)代码
%Programzp_ofdm
N=256;%Thenumberofthesubcarriers,i.e.,fftsize
Ncp=N/4;%thelengthofthecyclicprefix
Ns=N+Ncp;%ThewholelengthofeachOFDMsymbol
Ntry=100;%ThenumberofOFDMFrametosimulateperSNRvalue
Nsyb=20;%ThenumberofOFDMsymbolsperframe
M=16;%M-aryQAM
m=log2(M);%mbitspersubcarrier
Pav=2*(M-1)/3.0;%averagepowerofeachsubcarrier
PavdB=10*log10(Pav/N);%averagepoweroftimesignalindBforOFDM
SNRdB=[0:
5:
40];%SNRlisttobesimulated
SNR=10.^(SNRdB/10);
%Setmulti-pathfadingchannelparameters
Np=Ncp/4;%Thenumberofmultipaths
%idxTaps=sort(randperm(Ncp,Np));%Aftermatlab2012a
idxTaps=randperm(Ncp);%beforematlab2012a
idxTaps=sort(idxTaps(1:
Np));%beforematlab2012a
idxTaps-idxTaps
(1)+1;%Movethefirstmultipathto0delay
DPS=exp(-3*idxTaps/Ncp);%powerineachtap:
DelayPowerSpectrum
DPS=DPS/sum(DPS);%Normalize
Ampath=sqrt(DPS);%Amplitudeofeachpath
hzero=zeros(Ncp,1);%zerovectorforchannelimpulseresponse
ErrSymbols=zeros(size(SNRdB));%storethenumberoftheerrorsymbols
ErrSymbols_zf=zeros(size(SNRdB));%storethenumberoftheerrorsymbols
ErrSymbols_mmse=zeros(size(SNRdB));
tic%theinstantbeginsimulation
fornumSimSymbols=1:
Ntry
curErrSymbols_zf=0;
%Step1:
Generaterandomdigitalmessage
d=randi([0,M-1],N,Nsyb);%Messagesignal
%Step2:
M-QAMmodulation.
X=qammod(d,M);
%Step3:
IFFT,generatetimefieldsignal,
%i.e.,modulateatfrequencyField,
x=ifft(X);
si=size(x);
%Step4:
Ìí¼ÓÑ»·Ç°×º
xcp=[x;zeros(Ncp,si
(2))];
%Serialize
xcp=xcp(:
);
%Step5a:
TransmitthroughChannel
%MannullyGeneratemultipathchannelimpulseresponse
cir=Ampath.*(randn(1,Np)+1j*randn(1,Np))/sqrt
(2);
h=hzero;h(idxTaps)=cir.';%storechannel
%Channeleffect
xcpch=zeros(Ns*Nsyb+Ncp,1);
forp=1:
Np
idx=[0:
Ns*Nsyb-1]+idxTaps(p);
xcpch(idx)=xcpch(idx)+cir(p)*xcp;
end
xcpch=xcpch(1:
Ns*Nsyb);
C=[h;zeros(N,1)];
R=[h
(1),zeros(1,N-1)];
H=toeplitz(C,R);
gzf=pinv(H);%ZF-equalizer
fork=1:
length(SNRdB)
%Step5b:
AWGN
y=awgn(xcpch,SNRdB(k),'measured');%PavdB);
%Step6:
DeleteCP
y=reshape(y,[Ns,Nsyb]);
%Step7a:
ZF-Timedomainequalization
Yhat_zf=gzf*y;
yhat_zf=fft(Yhat_zf);
%Step9:
Demodulate,torecoverthemessage.
dhat_zf=qamdemod(yhat_zf,M);
%Step10:
Computesymbolerrorrate.
ddif_zf=d-dhat_zf;ddif_zf=ddif_zf(:
);
curErrSymbols_zf=length(find(ddif_zf~=0));
ErrSymbols_zf(k)=ErrSymbols_zf(k)+curErrSymbols_zf;
%Step7b:
MMSE-Timedomainequalization
gmmse=inv((1/SNR(k))*eye(N)+(H')*H)*(H');
Yhat_mmse=gmmse*y;
yhat_mmse=fft(Yhat_mmse);
%Step9:
Demodulate,torecoverthemessage.
dhat_mmse=qamdemod(yhat_mmse,M);
%Step10:
Computesymbolerrorrate.
ddif_mmse=d-dhat_mmse;ddif_mmse=ddif_mmse(:
);
curErrSymbols_mmse=length(find(ddif_mmse~=0));
ErrSymbols_mmse(k)=ErrSymbols_mmse(k)+curErrSymbols_mmse;
end
end
toc%simulationtime
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