【導(dǎo)讀】通信系統(tǒng)，具有傳輸速率快、抗多徑干擾能力強(qiáng)的優(yōu)點(diǎn)。下系統(tǒng)的誤碼率，并對(duì)其進(jìn)行分析。進(jìn)入21世紀(jì)以來，無線通信技術(shù)正在以前所未有的速度向前發(fā)展。結(jié)構(gòu)也將發(fā)生根本的變化。同時(shí)他把高速數(shù)據(jù)通過串并轉(zhuǎn)換，使得每個(gè)子載波上的數(shù)據(jù)符號(hào)持。在OFDM中引入循環(huán)前綴，克服了OFDM相鄰塊之。史，主要用于軍用的無線高頻通信系統(tǒng)。限制了其進(jìn)一步推廣。直到上世紀(jì)70年代，人們采用離散傅立葉變換來實(shí)現(xiàn)多個(gè)。載波的調(diào)制，簡化了系統(tǒng)結(jié)構(gòu)，使得OFDM技術(shù)更趨于實(shí)用化。目前OFDM技術(shù)已經(jīng)被廣泛應(yīng)用于廣播式的音頻、對(duì)于低速并行的子載波而言，由于符號(hào)周期展寬，多徑效。應(yīng)造成的時(shí)延擴(kuò)展相對(duì)變小。當(dāng)每個(gè)OFDM符號(hào)中插入一定的保護(hù)時(shí)間后，碼間。利用快速反傅立葉變換實(shí)現(xiàn)整個(gè)OFDM通信系統(tǒng)，如圖１所示。在實(shí)際應(yīng)用中，可以采用更加方便快捷的IFFT/FFT實(shí)現(xiàn)?？顾ヂ浜透蓴_能力，同時(shí)由于每個(gè)子載波的正交性，大大提高了頻譜的利用率，所以非常適合移動(dòng)場合中的高速傳輸。

　　

【正文】 ++++++++++++++++++++++++++++++ %+++++++++++++++++++++++++++信道交織編碼 +++++++++++++++++++++++++ interlacedata=interlacecode(encodeDATA,8,24)。 %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %+++++++++++++++++++++++++以下為 QPSK調(diào)制部分 +++++++++++++++++++++ QPSKdata=qpsk(interlacedata)。 %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %+++++++++++++++++++++++++++生成訓(xùn)練序列 +++++++++++++++++++++++++ if seq_num3 trainsp_temp=seq_train()。 end %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %++++++++++++++++++++++++++++插入導(dǎo)頻 ++++++++++++++++++++++++++++ PILOT=(1+j)。 m_QPSKdata=QPSKdata。 data2fft_temp=[m_QPSKdata(1:8),PILOT,m_QPSKdata(9:16), PILOT,m_QPSKdata(17:24),PILOT,m_QPSKdata(25:32),PILOT, m_QPSKdata(33:40),PILOT,m_QPSKdata(41:48),m_QPSKdata (49:56),PILOT,m_QPSKdata(57:64),PILOT,m_QPSKdata(65:72), PILOT,m_QPSKdata(73:80),PILOT,m_QPSKdata(81:88),PILOT, m_QPSKdata(89:end)]。 %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ trainsp_temp2=[trainsp_temp,zeros(1,128)]。 trainsp=[trainsp_temp2(65:256),trainsp_temp2(1:64)]。 %++++++++++++++++++++++++++降 PAPR矩陣變換 ++++++++++++++++++++++++ matix_data=nyquistimp_PS()。 matrix_mult=data2fft_temp*matix_data。 %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ data2fft2=[matrix_mult(65:128),zeros(1,128),matrix_mult(1:64)]。 %++++++++++++++++++++++++++++ifft運(yùn)算 +++++++++++++++++++++++++++ if seq_num==1 ifftin=trainsp。 elseif seq_num==2 ifftin=trainsp。 else 30 ifftin=data2fft2。 end IFFTdata=fft_my(conj(ifftin)/256)。 IFFTdata=conj(IFFTdata)。 % figure % plot(real(IFFTdata)) % xlabel(39。realIFFTdata39。) % figure % plot(imag(IFFTdata)) % xlabel(39。imagIFFTdata39。) %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %+++++++++++++++++++以下為插入循環(huán)前后綴， 2倍升采樣 +++++++++++++++ data2fir=add_CYC_upsample(IFFTdata,2)。 % ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ % +++++++++++++++++++++++++fir低通濾波 ++++++++++++++++++++++++++ guiyi_a=[ ]。 %抽樣截止頻率為 128kHz，通帶截止頻率為 20kHz， 阻帶截止頻率為 40kHz，帶內(nèi)紋波動(dòng) %小于 1dB，帶外衰減 100dB txFIRdatai=filter(guiyi_a,1,real(data2fir))。 txFIRdataq=filter(guiyi_a,1,imag(data2fir))。 % ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ OFDM通信系統(tǒng)仿真程序（ 3） %+++++++++++++++++++++++++發(fā)射機(jī) cic濾波 ++++++++++++++++++++++++++ CICidatai=cic_inter(txFIRdatai,20)。 CICidataq=cic_inter(txFIRdataq,20)。 %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %+++++++++++++++++++++++++++++上變頻 ++++++++++++++++++++++++++++ fwc_up=16。 %控制字可以選擇 DUCdata=up_convert_ofdm(fwc_up,CICidatai,CICidataq)。 %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %++++++++++++++++++++++++++高斯白噪聲信道 ++++++++++++++++++++++++ [DUCdata,datamax]=guiyi_DUCdata(DUCdata)。 awgnawgn_data=awgn(DUCdata,SNR_System)。 %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %*****************************接受機(jī) ***************************** %+++++++++++++++++++++++++++++下變頻 +++++++++++++++++++++++++++++ DUCdata_tmp=awgn_data。 fwc_downfwc_down=fwc_down+(fre_offset*128/2560000)。 r_fre_offset=2560000*((fwc_downfwc_up)/128)。 [DDCdatai,DDCdataq]=down_convert_ofdm(fwc_down,DUCdata_tmp)。 31 %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %++++++++++++++++++++++++++接收機(jī) cic濾波 +++++++++++++++++++++++++ CICddatai=cic_deci(DDCdatai,40,40)。 CICddataq=cic_deci(DDCdataq,40,40)。 %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %++++++++++++++++++++++++++++fir低通濾波 ++++++++++++++++++++++++ guiyi_b=[ ]。 %抽樣截止頻率為 64kHz，通帶截止頻率為 20kHz， 阻帶截止頻率為 30kHz，帶內(nèi)紋波動(dòng)小于 1dB，帶外衰減 60dB rxFIRdatai=filter(guiyi_b,1,CICddatai)。 rxFIRdataq=filter(guiyi_b,1,CICddataq)。 %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %+++++++++++++++++++++++++++++++量化 ++++++++++++++++++++++++++++ q_rxFIRdatai=sign(rxFIRdatai)。 q_rxFIRdataq=sign(rxFIRdataq)。 %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %++++++++++++++++++++++++++++定時(shí)同步檢測 ++++++++++++++++++++++++ if seq_num3 time_syn(q_rxFIRdatai,q_rxFIRdataq)。 end %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %+++++++++++++++++++++++++++++頻率同步 +++++++++++++++++++++++++++ fre_offset=fre_syn(rxFIRdatai,rxFIRdataq)。 %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %+++++++++++++++++++++++++++++fft運(yùn)算 +++++++++++++++++++++++++++ if seq_num2 seq_num2 fftw=32+dingshi。 rxFIRdata_syn=rxFIRdatai(fftw:fftw+255)+j*rxFIRdataq(fftw:fftw+255)。 FFTdata=fft_my(rxFIRdata_syn)。 %++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %++++++++++++++++++++++++++降 PAPR逆矩陣變換 ++++++++++++++++++++++ fftdata_reg=[FFTdata(193:256),FFTdata(1:64)]。 dematrix_data=fftdata_reg*pinv(matix_data)。 %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %++++++++++++++++++++++++++++相位補(bǔ)償 +++++++++++++++++++++++++++ rx_qpsk_din_th=phase_p(dematrix_data)。 %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %+++++++++++++++++++++++++++QPSK解調(diào)部分 ++++++++++++++++++++++++ % figure % plot(rx_qpsk_din_th,39。.39。) 32 % xlabel(39。星座圖 39。) datatemp4=deqpsk(rx_qpsk_din_th)。 datatemp4=sign(datatemp4)。 for m=1:192 if datatemp4(m)==1 datatemp4(m)=1。 elseif datatemp4(m)==1 datatemp4(m)=0。 end end %++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %+++++++++++++++++++++++++信道解交織 ++++++++++++++++++