matlab_16QAM数字基带信号系统仿真，包括发射机程序和接收端程序

close all; clc; clear all; tic; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %系统函数调用与自编函数调用控制,字符A为系统函数调用；字符B为自编函数调用 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% rcos_filter_c='A'; error_bit_expr='A'; qammod_sel='A'; awgn_sel='A'; qamdemod_sel='A'; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %仿真序列长度控制 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% N=10000; %产生一帧内的0/1序列总比特数 frame=200; %传输的总帧数 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %发端成型滤波器设计 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% M=16; %16QAM调制 fd=1; %符号采样频率 fs=8; %滤波器采样频率 rolloff=0.8; %滚降系数因子 delay=3; %滤波器半边带数 if strcmp(rcos_filter_c,'A') [b,den]=rcosine(fd,fs,'sqrt',rolloff,delay); %设计滤波器系数(系统函数调用) else b=sqrtcos_filter(rolloff,delay,fs); %设计滤波器系数(自编函数调用) end %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %载波参数设计 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% N_insert=16; fc=10; %载波频率为信号符号频率10倍 ts=1/(fc*(N_insert-1)); t=0:ts:((2*N+2*delay*fs)*20-1)*ts; %一个符号周期内的载波时间控制 cos_c=cos(2*pi*fc.*t); %载波正弦公式 sin_c=sin(2*pi*fc.*t); %载波正弦公式 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %滤波之前与滤波之后信号信噪比 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% SNR_out=[0 1 2 3 4 5 6 7 8 9 10 11 12]; %滤波之后的Eb/N0比特信噪比 SNR_in=SNR_out+10*log10(log2(M))-10*log10(fs); %滤波之前的Es/N0符号信噪比 snr_in=10.^(SNR_in/10); %滤波之前的Es/N0的线性值 snr_out=10.^(SNR_out/10); %滤波之后的Eb/N0的线性值 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %理论误码率公式 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% if strcmp(error_bit_expr,'A') ber1=berawgn(SNR_out,'qam',M); %理论误码率公式(系统函数调用) else P4=2*(1-1/sqrt(M))*qfunc(sqrt(3*snr_out*log2(M)/(M-1))); %单边PAM调制的误符号率 ser1=1-(1-P4).^2; %QAM看作两个PAM调制时的误符号率 ber1=1/log2(M)*ser1; %理论误码率公式-将误符号率除以每符号比特数 end %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% for k=1:length(SNR_in) error_bit_num=0; for l=1:frame x=randint(1,N); %产生一帧内的N个0/1比特序列 y=bittosymbol(x,log2(M)); %串并转化，4个二进制序列编程一个十进制数 symbol_in=y; %保存串并转换的十进制数据，便于后面误码率计算 y=BintoGray(y); %二进制转换成格雷码 if strcmp(qammod_sel,'A') y=qammod(y,M); %16QAM调制(系统函数调用) else y=dectocomp(y); %16QAM调制(自编函数调用) end y_real=real(y); %取出调制信号实部 y_imag=imag(y); %取出调制信号虚部 y_real=upsample(y_real,fs); %对实部进行fs倍上采样 y_imag=upsample(y_imag,fs); %对虚部进行fs倍上采样 y_real_pulse=conv(b,y_real); %实部信号成型 y_imag_pulse=conv(b,y_imag); %虚部信号成型 y_real_interp=interp(y_real_pulse,fc*N_insert/fs); %成型信号实部加载波 y_imag_interp=interp(y_imag_pulse,fc*N_insert/fs); %成型信号虚部加载波 y_real_carry=y_real_interp.*cos_c; y_imag_carry=y_imag_interp.*sin_c; if strcmp(awgn_sel,'A') s_noise_real=awgn(y_real_pulse,SNR_in(1,k),'measured'); s_noise_imag=awgn(y_imag_pulse,SNR_in(1,k),'measured'); else s_pow_avg=(y_real_pulse*y_real_pulse'+y_imag_pulse*y_imag_pulse')/length(y_imag_pulse); %计算每个符号的平均功率 sigma=sqrt(s_pow_avg/(2*snr_in(1,k))); %计算每个传输序列的噪声幅度值 s_noise_real=y_real_pulse+sigma*randn(1,length(y_real_pulse)); %实部序列加高斯噪声 s_noise_imag=y_imag_pulse+sigma*randn(1,length(y_imag_pulse)); %虚部序列加高斯噪声 end s_filter_real_pulse=conv(s_noise_real,b); %实部信号滤波 s_filter_imag_pulse=conv(s_noise_imag,b); %虚部信号滤波 s=zeros(1,N); %新建接受端复数序列数组 s_real_r=downsample(s_filter_real_pulse,fs); %滤波之后实部信号下采样 s_imag_r=downsample(s_filter_imag_pulse,fs); %滤波之后虚部信号下采样 s_r_real=s_real_r((2*delay+1):(end-2*delay)); %去掉由于卷积产生的延时 s_r_imag=s_imag_r((2*delay+1):(end-2*delay)); %去掉由于卷积产生的延时 s=s_r_real+i*s_r_imag; %实部与虚部组成复数信号 if strcmp(qamdemod_sel,'A') r=qamdemod(s,M); %接收信号解调成符号序列 else r=demod(s); %将有噪声的星座点映射到标准星座点 r=comptodec(r); %将星座点映射成对应的十进制实数 end r=Graytobin(r); %格雷编码逆映射 [errorBit(1,k),BER(1,k)]=biterr(symbol_in,r,log2(M)); %计算误码比特数和误码率 error_bit_num=errorBit(1,k)+error_bit_num; %多帧误码比特数的累加 if error_bit_num>100 || l==frame %判断帧循环条件，以加速程序运行速度 BER(1,k)=error_bit_num/(N*l); %多帧误码率计算结果 break; end if k==13 && l==1 figure(1); scatterplot(y); figure(2); subplot(211); plot(y_real(1:400)); subplot(212); plot(y_imag(1:400)); figure(3); subplot(211); plot(y_real_pulse(1:400)); subplot(212); plot(y_imag_pulse(1:400));d figure(4); plot(y_real_carry(400:1400)); hold on plot(y_real_interp(400:1400),'--r'); figure(5); subplot(211); plot(s_filter_real_pulse(1:500)); subplot(212); plot(s_filter_imag_pulse(1:500)); scatterplot(s); figure(6); w=-5:0.1:5; subplot(211); hist(s_r_real,w); subplot(212); hist(s_r_imag,w); else end end end figure(7); semilogy(SNR_out,BER,'-r*',SNR_out,ber1,'--bo'); %红色的是实际误码率，蓝色是理论误码率曲线 title('16QAM在AWGN信道下的性能'); xlabel('SNR/dB'); ylabel('BER'); legend('实际BER','理论BER'); toc;