【扩频通信】基于matlab直接序列扩频通信系统仿真（调制方式BPSK）【含Matlab源码 4012期】.zip

% ************************beginning of file******************************** % Module: Main_DSBPSK.m % Note: 实现直接序列扩频通信系统的仿真，调制方式BPSK. %************************************************************************** clear all; close all; clc; %*******************************仿真参数设定******************************** %宏参设定 Ml = 1; %每个符号所占比特数目（调制阶数） SymNum = 800; %符号数目 SNJ1 = 1:10; %干信比 SNJ = 1:10; %信噪比 NumLoop= 20; %仿真循环次数 %数据编码参数 Encode_type = 2; %编码方式 1、未编码 2、卷积编码 Encode_rate = 0.5; %编码率 Decode_tlen = 5; %译码跟踪长度 %扩频码初值设定 UserNum = 1; %用户数目 SeqType = 1; %序列类型 1：m序列 2：Gold序列 Seqstage = 9; %反馈寄存器的阶数 ptaps1 = [1 3]; %第一个反馈寄存器的系数 ptaps2 = [2 3]; %第二个反馈寄存器的系数 Reg1ini = ones(1,Seqstage); %第一个反馈寄存器初始化 Reg2ini = ones(1,Seqstage); %第二个反馈寄存器初始化 %滤波器参数设定 alpha = 1; %滚降因子 firlen = 4; %滤波器阶数 sample_rate = 4; %采样率 Ts = 4; %信道特性参数设定 delay_tau = 0; %干扰特性参数设定 J_type = 1; %干扰类型 1:宽带干扰 2：余弦单音干扰3：脉冲单音干扰 J_fs = 2048; %单音干扰频率 J_theta = 0; %单音干扰相位 J_tone = 0.5; %脉冲单音干扰占空比 J_p = sqrt(250); %干扰功率 %*******************************模块生成*********************************** %滤波器生成 ht = rcosfir(alpha,firlen,sample_rate,Ts,'sqrt'); %发送或接受滤波器 ht = (1-alpha+alpha*4/pi).*ht./max(ht); %扩频码生成 switch SeqType case 1 code = MSeq(Seqstage,ptaps1,Reg1ini,UserNum); code = [code.*2-1,1]; case 2 m1 = MSeq(Seqstage,ptaps1,Reg1ini,UserNum); m2 = MSeq(Seqstage,ptaps2,Reg2ini,UserNum); code = Goldseq(m1, m2, UserNum); code = [code.*2-1,-1]; end code_len = length(code); %*******************************原始序列生成******************************** %发送端 data = randsrc(UserNum,Ml*SymNum,[0 1]); %产生信息序列 switch Encode_type case 1 %未编码 codedata = data; case 2 % 卷积编码 trel = poly2trellis(3,[4 7]); codedata = convenc(data,trel); end codedata = 2.*codedata-1; %变成双极性 sdata = Enspread(codedata,code,sample_rate); %扩频调制并采样 signalsend = conv2(sdata,ht,'same'); %成型滤波 slen = length(signalsend); Tn = delay_tau:Ts/code_len/sample_rate:Ts*length(codedata)-Ts/code_len/sample_rate+delay_tau; FF=fft(signalsend(1:1000)); plot(abs(FF)); %信道干扰选择 switch J_type case 1 Jatter = 0; SNJ = SNJ1; case 2 Jatter = sqrt(2).*J_p.*cos(2*pi*J_fs*Tn+J_theta); case 3 Jsn = fix(J_tone*code_len*sample_rate); sn = 1:slen; Jatter = zeros(1,slen); Jatter(mod(sn-1,code_len*sample_rate)<Jsn) = J_p; Jatter = Jatter.*cos(2*pi*J_fs*Tn); end %噪声产生 Nn = 3; nlen = Nn*slen; nstate = Nn*slen - slen; nrandseq = randn(1,nlen); error_rate = zeros(1,length(SNJ)); %*******************************开始仿真*********************************** for jns = 1:length(SNJ) error_num = 0; %干扰方差 Jatp = 10^(SNJ(jns)/10); Eb = 512; TbTc=512; spow=sum(abs(signalsend).^2)/SymNum/TbTc; Jsgma = sqrt(Eb*2/Jatp); for ii = 1:NumLoop %计算噪声序列 nstart = randi(nstate); s_noise = Jsgma.*nrandseq(nstart+1:nstart+slen); %加噪声和干扰 rcvsignal = signalsend + s_noise + Jatter; % % rcvsignal = signalsend; %功率限幅法去除单音干扰 if J_type~= 1 fs = fft(rcvsignal); sn = find(abs(fs)>1e5); fs(sn) = 1e5.*exp(j.*angle(fs(sn))); rcvsignal = ifft(fs); end %接收端 rcvsignal = conv2(rcvsignal,ht,'same'); rdata = Despread(rcvsignal,code,sample_rate); rdata = (rdata >= 0); switch Encode_type case 1 decodedata = rdata; case 2 decodedata = vitdec(rdata,trel,Decode_tlen,'trunc','hard'); end %判决，计算无码个数 liminal = data - decodedata; error_num = error_num + length(find(liminal~=0)); end %由于仿真耗时，所以记录下仿真数据 data_len_totel = SymNum*NumLoop; bit_err_rate = error_num/data_len_totel; fprintf('%d\t%d\t%d\t%e\n',SNJ(jns),error_num,data_len_totel,bit_err_rate); error_rate(jns) = bit_err_rate; if bit_err_rate == 0 break; end end %*****************************仿真结束************************************** theo_err_rate = zeros(1,length(SNJ)); %计算理论性能 for the_err = 1:length(SNJ) theo_err_rate(the_err) = qfunc(sqrt(2*10^(SNJ(the_err)/10))); end % save('theo_err_rate.mat','theo_err_rate'); %*****************************性能仿真图示********************************** %模块频谱 figure(1); subplot(3,2,1); plot(signalsend); title('扩频后信号'); subplot(3,2,2); plot(rcvsignal); title('携带干扰信号'); subplot(3,2,3); plot(abs(fft(signalsend))); title('扩频后中频信号频谱图'); subplot(3,2,4); plot(abs(fft(rcvsignal))); title('携带干扰信号频谱图'); subplot(3,2,5); plot(ht); title('滤波器冲击序列'); subplot(3,2,6); plot(abs(fft(ht))); title('滤波器频谱图'); %误码性能 switch J_type case 1 figure(2); semilogy(SNJ,theo_err_rate,'r-.','LineWidth',2); hold on; semilogy(SNJ,error_rate,'b-*','LineWidth',2); grid on; axis([SNJ(1),SNJ(length(SNJ)),0,1]); ylabel('误码率'); xlabel('信干比/dB'); if Encode_type == 1 legend('无编码理论误码率曲线','无编码仿真误码率曲线'); title('仿真性能图(宽带干扰,无编码)'); else legend('无编码理论误码率曲线','1/2卷积编码仿真误码率曲线'); title('仿真性能图(宽带干扰，1/2卷积编码)'); end case 2 filename = ['error_w_' num2str(J_fs) '.mat']; save(filename,'error_rate'); figure(2); semilogy(SNJ,error_rate,'r-*','LineWidth',2); grid on; axis([SNJ(1),SNJ(length(SNJ)),0,1]); ylabel('误码率'); xlabel('信噪比/dB'); if Encode_type == 1 title('仿真性能图(单音干扰,无编码)'); else title('仿真性能图(单音干扰，1/2卷积编码)'); end case 3 filename = ['error_p_' num2str(ceil(J_tone*5)) '.mat']; save(filename,'error_rate'); figure(2); semilogy(SNJ,error_rate,'r-*','LineWidth',2); grid on; axis([SNJ(1),SNJ(length(SNJ)),0,1]); ylabel('误码率'); xlabel('信噪比/dB'); if Encode_type == 1 title('仿真性能图(脉冲单音干扰,无编码)'); else title('仿真性能图(脉冲单音干扰，1/2卷积编码)'); end end %************************end of file***************************************