基于matlab的多径信道下OFDM通信系统误码率仿真

close all clear all %% ====================仿真基本参数==================== f_delta = 15e3; %子载波间隔15KHz pilot_interval = 5; %插入导频间隔 M = 2; %每星座符号比特数，对应QPSK调制 ce_method = 1; %信道估计方法，1和2分别对应LS和MMSE symbol_len = 1000; %OFDM符号数 p=1; %% ====================仿真可配置参数==================== awgn_en = 0; %信道类型，为1表示AWGN信道，为0表示 ETU信道 fd = 300; %最大多普勒扩展 sta_num = 10; %仿真次数统计 num_carriers = input('请输入子载波数:'); %子载波数 cp_length = input('请输入循环前缀长度:'); %循环前缀长度 %% ====================仿真过程======================= % 产生0-1随机序列 =>（交织）=> 符号映射 => 串并转换 => 插入导频 % => IFFT变换 => 加循环前缀CP => 并串转换 => （信道编码） => 多径信道% => 加AWGN => （信道译码）=> 串并转换 =>去循环前缀CP => 去导频 => % FFT变换 / 信道估计与频域均衡 => 并串转换 => 解映射 =>（解交织） % => 计算误码率 => 绘制误码率曲线 % ================================================== %% ================产生随机序列======================= sr0=sourcebits(symbol_len*num_carriers*M);%随即序列长度为子载波数目×ofdm符号数×M %% 卷积编码 [sr,tre1,tblen,p]=conv(sr0); %% ================交织======================= sr = interlace(sr,M); %% ================符号映射======================= ak=qpsk_modulation(sr); %% ================串并转换======================= parallel_ak = reshape(ak,num_carriers,symbol_len/p); %% ================插入导频======================= pilot_bit = ones(num_carriers*2,1);%生成导频序列 [insert_pilot_out,count,pilot_seq] = ... insert_pilot_f(parallel_ak,pilot_bit,pilot_interval,num_carriers); %% ================IFFT变换======================= OFDMmoddata_out = ifft (insert_pilot_out,num_carriers)*sqrt(num_carriers);%离散傅立叶变换点数为子载波数 %% ================加循环前缀CP======================= CP_output=Inset_CP(OFDMmoddata_out,cp_length); %% ================并串转换======================= [m,n] = size(CP_output);%并行数据的长度为加cp后的数据矩阵的元素总数m*n OFDMmoddata_out_serial = reshape(CP_output,m*n,1); %% ================多径信道======================= %信道参数为36.101协议指定 SNR = 0:2:34; % 用于检测的信噪比值 for snr_index = 1:length(SNR) fs = num_carriers * f_delta; ts = 1/fs; tau = [0,50,120,200,230,500,1600,2300,5000]/(10^9); pdb = [-1.0 ,-1.0 ,-1.0 ,0, 0, 0, -3.0, -5.0, -7.0]; chan = rayleighchan(ts,fd,tau,pdb); chan.ResetBeforeFiltering = 0; Channel_data = OFDMmoddata_out_serial; %经过多径信道 if (awgn_en == 1) Add_Multipath_data = Channel_data; else if (fd ~= 0) Add_Multipath_data = filter(chan,Channel_data); end end Add_noise_data = awgn(Add_Multipath_data,SNR(snr_index),'measured'); %% ================串并转换,去循环前缀CP======================= Delete_CP_out = Delete_CP(Add_noise_data,cp_length,num_carriers,p); %% ================去导频，取出导频矩阵======================= [DeletePolit_out,H_ifft] = Get_pilot(Delete_CP_out,pilot_interval,num_carriers,p); %% ====================直接解调，无信道补偿======================= fft_out = fft (DeletePolit_out)/sqrt(num_carriers); %并串转换 serial_ak_1 = reshape(fft_out,num_carriers*symbol_len/p,1); %解映射 demod_sr_1 = qpsk_demodulation(serial_ak_1); %解交织 demod_sr_1 = delete_interlace(demod_sr_1,M); % %viterbi译码 demod_sr_1 = viterbi(demod_sr_1,tblen,tre1); %% ==================信道估计与频域均衡======================= estimation_output = ls_estimation(DeletePolit_out,H_ifft,pilot_seq,num_carriers,p); %并串转换 serial_ak_2 = reshape(estimation_output,num_carriers*symbol_len/p,1); %解映射 demod_sr_2 = qpsk_demodulation(serial_ak_2); %解交织 demod_sr_2 = delete_interlace(demod_sr_2,M); %viterbi译码 demod_sr_2 = viterbi(demod_sr_2,tblen,tre1); %% ===================计算误码率======================= errorbit_num_1(snr_index) = length(find(demod_sr_1~= sr0));%统计直接解调错误比特数 BER_1(snr_index) = errorbit_num_1(snr_index) / (symbol_len*num_carriers*M); errorbit_num_2(snr_index) = length(find(demod_sr_2 ~= sr0));%统计信道估计与频域均衡错误比特数 BER_2(snr_index) = errorbit_num_2(snr_index) / (symbol_len*num_carriers*M); end %% ================绘制 SNR-BER 曲线================ semilogy(SNR,BER_1,'b*-.'); hold on; semilogy(SNR,BER_2,'m+-'); xlabel('SNR (dB)'); ylabel('BER'); grid on; legend('直接解调','信道估计与频域均衡') axis([SNR(1) SNR(end) 0.01 1])