如何用MATLAB生成OFDM时域信号波形
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载波计数= 200；子载波数量%
符号每载波= 12；每个子载波的符号数百分比
每符号位数= 4；每符号%位，16QAM调制
IFFT _宾_长度= 512；FFT点数百分比
prefix ratio = 1/4；保护间隔与OFDM数据的百分比是1/6~1/4。
GI = prefix ratio * IFFT _ bin _长度；%添加到每个OFDM符号的循环前缀的长度是1/4*IFFT_bin_length，即保护间隔的长度是128。
beta = 1/32；%窗口函数的滚降系数
GIP = beta *(IFFT _ bin _长度+GI)；%循环后缀20的长度
SNR = 15；%信噪比dB
%==================================================
% = = = = = = = = = = = = =信号生成= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
基带输出长度=载波计数*符号每载波*比特每符号；输入的位数百分比
carriers =(1:carrier _ count)+(floor(IFFT _ bin _长度/4)-floor(carrier _ count/2))；对应于% * *轭对称副载波映射的复数数据的IFFT点坐标。
共轭_载波= IFFT _ bin _长度-载波+2；% * * *轭对称副载波映射* * *轭复数对应的IFFT点坐标。
rand( 'state '，0)；
基带_out=round(rand(1，基带_ out _ length))；%输出要调制的二进制比特流
% = = = = = = = = = = = 16 QAM调制= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
复数_载波_矩阵=qam16(基带_输出)；%列向量
complex _ carrier _ matrix = reshape(complex _ carrier _ matrix '，carrier_count，symbols _ per _ carrier)'；每个载波的符号百分比*载波计数矩阵
图(1)；
plot(complex_carrier_matrix，' * r ')；%16QAM调制后的星座图
轴([-4，4，-4，4])；
网格打开
% = = = = = = = = = = = = = = = = = IFFT = = = = = = = = = = = = = = = = = = = = = =
IFFT _调制=零(每载波符号，IFFT _ bin _长度)；%加0构成IFFT_bin_length IFFT运算。
IFFT _调制(:，载波)=复数_载波_矩阵；%导频信号不加，副载波映射在此。
IFFT _调制(:，共轭_载波)= conj(复数_载波_矩阵)；% * * *磁轭复杂映射
%========================================================
图(2)；
Stem (0: IFFT _ bin _ length-1，ABS (IFFT _调制(2，1: IFFT _ bin _ length))，' b *-')%第一个OFDM符号的频谱。
网格打开
轴([0 IFFT _ bin _ length-0.5 4.5])；
ylabel('震级')；
xlabel(“IFFT·宾”)；
标题(“OFDM载波频率幅度”)；
图(3)；
plot(0:IFFT_bin_length-1，(180/pi)*角度(IFFT _调制(2，1:IFFT_bin_length))，' go ')
继续
stem(0:载波-1，(180/pi)*角度(IFFT _调制(2，1:载波))，' b *-')；第一个OFDM符号的%相位
stem(0:共轭_载波-1，(180/pi)*角度(IFFT _调制(2，1:共轭_载波))，' b *-')；
坐标轴([0 IFFT _ bin _长度-200 +200])
网格打开
ylabel('相位(度)')
xlabel(“IFFT·宾”)
标题(“OFDM载波相位”)
%=================================================================
信号_ after _ IFFT = IFFT(IFFT _调制，IFFT_bin_length，2)；%OFDM调制是IFFT变换。
时间_波_矩阵=信号_后_ after%时域波形矩阵，表示每个载波的符号数，列出了ITTF点，N个子载波映射在其中，每行是一个OFDM符号。
图(4)；
支线剧情(3，1，1)；
plot(0:IFFT_bin_length-1，时间_波_矩阵(2，))；第一个符号的%波形
轴([0，700，-0.2，0.2])；
网格打开；
ylabel('振幅')；
xlabel(' Time ')；
标题(“OFDM时间信号，一个符号周期”)；
%===========================================================
% = = = = = = = = = = = = =添加一个循环前缀和后缀= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
XX =零(符号_每载波，IFFT _ bin _长度+GI+GIP)；
对于k=1:每载波符号数；
对于I = 1:IFFT _ bin _ length；
XX(k，i+GI)=signal_after_IFFT(k，I)；
结束
对于I = 1:GI；
XX(k，i)=signal_after_IFFT(k，I+IFFT _ bin _ length-GI)；%添加循环前缀
结束
对于j = 1:GIP；
XX(k，IFFT _ bin _ length+GI+j)= signal _ after _ IFFT(k，j)；%添加循环后缀
结束
结束
time _ wave _ matrix _ cp = XX%具有循环前缀和后缀的时域信号矩阵，并且OFDM符号的长度是IFFT_bin_length+GI+GIP=660。
支线剧情(3，1，2)；
plot(0:length(time _ wave _ matrix _ CP)-1，time_wave_matrix_cp(2，)；%第一个符号添加了循环前缀的波形
轴([0，700，-0.2，0.2])；
网格打开；
ylabel('振幅')；
xlabel(' Time ')；
标题(“带CP的OFDM时间信号，一个符号周期”)；
% = = = = = = = = = = = = OFDM符号开窗= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
windowed _ time _ wave _ matrix _ CP = zeros(1，IFFT _ bin _ length+GI+GIP)；
对于i = 1:每载波符号数
windowed_time_wave_matrix_cp(i，)= real(time_wave_matrix_cp(i，))。*rcoswindow(beta，IFFT _ bin _ length+GI)'；%窗口升余弦窗口
结束
支线剧情(3，1，3)；
plot(0:IFFT _ bin _ length-1+GI+GIP，加窗_时间_波形_矩阵_cp(2，)；第一个符号的%波形
轴([0，700，-0.2，0.2])；
网格打开；
ylabel('振幅')；
xlabel(' Time ')；
标题(“OFDM时间信号应用一个窗口，一个符号周期”)；
% = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
windowed_Tx_data=zeros(1，symbols _ per _ carrier *(IFFT _ bin _ length+GI)+GIP)；
windowed _ Tx _ data(1:IFFT _ bin _ length+GI+GIP)= windowed _ time _ wave _ matrix _ CP(1，)；
对于i = 1:符号_每_载波-1；
windowed _ Tx _ data((IFFT _ bin _ length+GI)* I+1:(IFFT _ bin _ length+GI)*(I+1)+GIP)= windowed _ time _ wave _ matrix _ CP(I+1，)；%并串转换，循环后缀和循环前缀叠加。
结束
%=======================================================
tx _ data _ without window = shape(time _ wave _ matrix _ CP '，(symbols _ per _ carrier)*(IFFT _ bin _ length+GI+GIP)，1)'；%串行信号无窗口，仅添加循环前缀和后缀
tx _ data = shape(windowed _ time _ wave _ matrix _ CP '，(symbols _ per _ carrier)*(IFFT _ bin _ length+GI+GIP)，1)'；%窗口化后不叠加带循环前缀和后缀的串行信号
%=================================================================
temp _ time 1 =(symbols _ per _ carrier)*(IFFT _ bin _ length+GI+GIP)；%开窗口后，循环前缀和后缀不重叠发送总位数
图(五)
支线剧情(2，1，1)；
plot(0:temp _ time 1-1，Tx _ data)；%循环前缀和后缀不与发送的信号波形重叠。
网格打开
ylabel('振幅(伏特)')
xlabel('时间(样本)')
标题(“OFDM时间信号”)
temp _ time 2 = symbols _ per _ carrier *(IFFT _ bin _ length+GI)+GIP；
支线剧情(2，1，2)；
plot(0:temp_time2-1，windowed _ Tx _ data)；%循环后缀与循环前缀叠加以发送信号波形。
网格打开
ylabel('振幅(伏特)')
xlabel('时间(样本)')
标题(“OFDM时间信号”)
% = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
symbols _ per _ average = ceil(symbols _ per _ carrier/5)；1/5，10行%符号数
avg _ temp _ time =(IFFT _ bin _ length+GI+GIP)* symbols _ per _ average；%点，10行数据，10个符号
平均值= floor(temp _ time 1/avg _ temp _ time)；
average _ FFT(1:avg _ temp _ time)= 0；%被分成5个部分
对于a = 0:(平均值-1)
subset _ OFDM = Tx _ data _ without window((a * avg _ temp _ time)+1):((a+1)* avg _ temp _ time)；%
subset _ OFDM _ f = ABS(FFT(subset _ OFDM))；%将发送信号段频谱。
average _ FFT = average _ FFT+(subset _ OFDM _ f/averages)；将总* * *数据的%分成五段，对各段进行FFT，并进行平均相加。
结束
average _ FFT _ log = 20 * log 10(average _ FFT)；
图(6)
支线剧情(2，1，1)；
plot((0:(avg _ temp _ time-1))/avg _ temp _ time，average _ FFT _ log)%归一化0/avg _ temp _ time:(avg _ temp _ time-1)/avg _ temp _ log。
继续
plot(0:1/IFFT _ bin _ length:1，-35，' rd ')
网格打开
轴([0 0.5 -40最大值(average_fft_log)])
ylabel('幅度(dB)')
xlabel('归一化频率(0.5 = fs/2)')
标题(“无窗口的OFDM信号频谱”)
% = = = = = = = = = = = =加窗发射信号的频谱= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
symbols _ per _ average = ceil(symbols _ per _ carrier/5)；1/5，10行%符号数
avg _ temp _ time =(IFFT _ bin _ length+GI+GIP)* symbols _ per _ average；%点，10行数据，10个符号
平均值= floor(temp _ time 1/avg _ temp _ time)；
average _ FFT(1:avg _ temp _ time)= 0；%被分成5个部分
对于a = 0:(平均值-1)
subset _ OFDM = Tx _ data((a * avg _ temp _ time)+1):((a+1)* avg _ temp _ time)；%使用循环前缀后缀未叠加的串行加窗信号计算频谱。
subset _ OFDM _ f = ABS(FFT(subset _ OFDM))；%分段频谱
average _ FFT = average _ FFT+(subset _ OFDM _ f/averages)；将总* * *数据的%分成五段，对各段进行FFT，并进行平均相加。
结束
average _ FFT _ log = 20 * log 10(average _ FFT)；
支线剧情(2，1，2)
plot((0:(avg _ temp _ time-1))/avg _ temp _ time，average _ FFT _ log)%归一化0/avg _ temp _ time:(avg _ temp _ time-1)/avg _ temp _ log。
继续
plot(0:1/IFFT _ bin _ length:1，-35，' rd ')
网格打开
轴([0 0.5 -40最大值(average_fft_log)])
ylabel('幅度(dB)')
xlabel('归一化频率(0.5 = fs/2)')
标题(“加窗OFDM信号频谱”)
% = = = = = = = = = = = = = = =添加噪点= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
Tx _ signal _ power = var(windowed _ Tx _ data)；%发射信号功率
linear_snr=10^(snr/10)；%线性信噪比
noise _σ= Tx _ signal _ power/linear _ SNR；
噪声_比例_因子= sqrt(噪声_西格玛)；标准差百分比西格玛
noise=randn(1，((符号_每载波)*(IFFT _ bin _长度+GI))+GIP)* noise _ scale _ factor；%产生正态分布的噪声序列。
%noise=wgn(1，length(windowed_Tx_data)，noise_sigma，'复数')；%产生复杂的高斯白噪声信号。
rx _ data = windowed _ Tx _ data+noise；%接收信号加噪声
% = = = = = = = = = = = = = =接收信号字符串/并行变换去除前缀和后缀= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
Rx_data_matrix=zeros(符号_每载波，IFFT _ bin _长度+GI+GIP)；
对于i=1:每载波符号数；
Rx_data_matrix(i，)=Rx_data(1，(I-1)*(IFFT _ bin _ length+GI)+1:I *(IFFT _ bin _ length+GI)+GIP)；%串行-并行转换
结束
Rx _ data _ complex _ matrix = Rx _ data _ matrix(:，GI+1:IFFT _ bin _ length+GI)；%去除循环前缀和循环后缀，得到有用的信号矩阵。
%============================================================%================================================================
%==============================================================
% OFDM解码16QAM解码
% = = = = = = = = = = = = = FFT变换= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
y 1 = FFT(Rx _ data _ complex _ matrix，IFFT_bin_length，2)；%OFDM解码是FFT变换。
Rx_carriers=Y1(:，carriers)；%除由IFFT/FFT变换添加的零，并选择映射的子载波。
Rx _ phase =角度(Rx _ carriers)；接收信号的相位百分比
Rx _ mag = ABS(Rx _ carriers)；接收信号的%振幅
图(7)；
极坐标(Rx_phase，Rx_mag，' BD ')；用%极坐标画出接收信号的星座图。
%======================================================================
[M，N]=pol2cart(Rx_phase，Rx _ mag)；
Rx_complex_carrier_matrix =复数(M，N)；
图(8)；
plot(Rx_complex_carrier_matrix，' * r ')；%XY坐标下接收信号的星座图
轴([-4，4，-4，4])；
网格打开
% = = = = = = = = = = = = = = = = = 16 QAM解调= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
Rx _ serial _ complex _ symbols = reshape(Rx _ complex _ carrier _ matrix '，size(Rx_complex_carrier_matrix，1)* size(Rx _ complex _ carrier _ matrix，2)，1)'；
Rx _ decoded _ binary _ symbols = demoduqam 16(Rx _ serial _ complex _ symbols)；
%============================================================
基带_输入=接收_解码_二进制_符号；
图(9)；
支线剧情(2，1，1)；
stem(基带_ out(1:100))；
支线剧情(2，1，2)；
stem(基带_ in(1:100))；
% = = = = = = = = = = = = = =错误率计算= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
bit_errors=find(基带_ in ~ =基带_ out)；
位错误计数=大小(位错误，2)
ber =比特错误计数/基带输出长度