MATLAB直序扩频

毕业设计选题目Low snr system design，这个题目还是挺有趣的，这几天也顺便把matlab的扩频这一部分仿真重新研究了下，以下部分代码是综合了下博文视点出了MATLAB/Simulink书中的部分代码，学习了一下，还是挺不错的。

% main_DSCDMA.m % 北京理工大学珠海学院 % 徐方鑫 % 信息工程 %+++++++++++++++++++++++准备部分+++++++++++++++++++++++++++ clear all; clc sr = 256000.0; % 符号速率 ml = 2; % 调制阶数 br = sr * ml; % 比特速率 nd = 100; % 符号数 SNR=-5:1:10; % Eb/No %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %+++++++++++++++++++++滤波器初值设定+++++++++++++++++++++++ irfn = 21; % 滤波器阶数 IPOINT = 8; % 过采样倍数 alfs = 0.5; % 滚降因子 [xh] = hrollfcoef(irfn,IPOINT,sr,alfs,1); [xh2] = hrollfcoef(irfn,IPOINT,sr,alfs,0); %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %++++++++++++++++++++++++扩频码初值设定+++++++++++++++++++ user = 1; % 用户数 seq = 1; % 1:m序列 2:Gold序列 3:正交Gold序列 stage = 3; % 序列阶数 ptap1 = [1 3]; % 第一个线性移位寄存器的系数 ptap2 = [2 3]; % 第二个线性移位寄存器的系数 regi1 = [1 1 1]; % 第一个线性移位寄存器的初始化 regi2 = [1 1 1]; % 第二个线性移位寄存器的初始化 %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ disp('--------------start-------------------'); fprintf('%4s\t%4s\t%4s\t%4s\n','信噪比','误码数','总码数','误码率'); %+++++++++++++++++扩频码的产生+++++++++++++++++ for ebn0=-5:1:10 switch seq case 1 % m序列 code = mseq(stage,ptap1,regi1,user); case 2 % Gold序列 m1 = mseq(stage,ptap1,regi1); m2 = mseq(stage,ptap2,regi2); code = goldseq(m1,m2,user); case 3 % 正交Gold序列 m1 = mseq(stage,ptap1,regi1); m2 = mseq(stage,ptap2,regi2); code = [goldseq(m1,m2,user),zeros(user,1)]; end code = code * 2 - 1; clen = length(code); %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %+++++++++++++++++++++信道衰减初值设定+++++++++++++++++++++++ rfade = 0; % 瑞利衰减 0:不考虑 1:考虑 itau = [0,8]; % 延时 dlvl1 = [0.0,40.0]; % 衰减电平 n0 = [6,7]; % 用于产生衰落的波数 th1 = [0.0,0.0]; % 延迟波形的初始相位 itnd1 = [3001,4004]; % 设置衰落计数 now1 = 2; % 主径和延迟波形总数 tstp = 1 / sr / IPOINT / clen; % 时间分辨率 fd = 160; % 多普勒频移[Hz] flat = 1; % 平坦瑞利衰落环境 itndel = nd * IPOINT * clen * 30; %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %++++++++++++++++++++++仿真运算开始++++++++++++++++++++++++ nloop = 1000; % 仿真循环次数 noe = 0; nod = 0; for ii=1:nloop %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %++++++++++++++++++++++++发射机++++++++++++++++++++++++++++ data = rand(user,nd*ml) > 0.5; [ich, qch] = qpskmod(data,user,nd,ml); % QPSK 调制 [ich1,qch1] = spread(ich,qch,code); % 扩频 [ich2,qch2] = compoversamp2(ich1,qch1,IPOINT); % 过采样 [ich3,qch3] = compconv2(ich2,qch2,xh); % 滤波 if user == 1 ich4 = ich3; qch4 = qch3; else ich4 = sum(ich3); qch4 = sum(qch3); end %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %+++++++++++++++++++++++衰减信道++++++++++++++++++++++++++ if rfade == 0 ich5 = ich4; qch5 = qch4; else [ich5,qch5] = sefade(ich4,qch4,itau,dlvl1,th1,n0,itnd1, ... now1,length(ich4),tstp,fd,flat); itnd1 = itnd1 + itndel; end %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %+++++++++++++++++++++++++接收机++++++++++++++++++++++++++++ spow = sum(rot90(ich3.^2 + qch3.^2)) / nd; % 衰减计算 attn = sqrt(0.5 * spow * sr / br * 10^(-ebn0/10)); [ich6,qch6] = comb2(ich5,qch5,attn); % 添加高斯白噪声(AWGN) [ich7,qch7] = compconv2(ich6,qch6,xh2); % 滤波 sampl = irfn * IPOINT + 1; ich8 = ich7(:,sampl:IPOINT:IPOINT*nd*clen+sampl-1); qch8 = qch7(:,sampl:IPOINT:IPOINT*nd*clen+sampl-1); [ich9 qch9] = despread(ich8,qch8,code); % 解扩 demodata = qpskdemod(ich9,qch9,user,nd,ml); % QPSK解调 %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %++++++++++++++++++++误码率分析++++++++++++++++++++ noe2 = sum(sum(abs(data-demodata))); nod2 = user * nd * ml; noe = noe + noe2; nod = nod + nod2; % fprintf('%d\t%e\n',ii,noe2/nod2); end %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %+++++++++++++++++++++++++数据文件++++++++++++++++++++++++++ ber = noe / nod; fprintf('%4d\t%4d\t%4d\t%4e\n',ebn0,noe,nod,noe/nod); fid = fopen('BER.dat','a'); fprintf(fid,'%4d\t%4e\t%4f\t%4f\t\n',ebn0,noe/nod,noe,nod); fclose(fid); err_rate_final(ebn0+6)=ber; end %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %+++++++++++++++++++++++++性能仿真图++++++++++++++++++++++++++ figure semilogy(SNR,err_rate_final,'b-*'); xlabel('信噪比/dB') ylabel('误码率') axis([-5,10,0,1]) grid on disp('--------------end-------------------'); %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++