请教下OFDM系统在matlab上的仿真程序！

％实现OFDM传输的仿真程序

para=128； ％并行子信道的个数

fftlen：128； ％FFT的长度

paradata=reshape(seldata，para，nd

*m1)；

％QPSK调制

[ich，qch]=qpskmod(paradata，para，nd，m1)；

kmod=1／sqrt(2)；

ichl=ich．*kmod；

qchl=qch．*kmod；

％In叩(离散傅里叶反变换)

X=ichl+qchl．*i：

y=ifft(x)；

ich2=real(y)；

qch2=imag(y)；

％插入保护间隔

[ich3，qch3]=giins(ich2，qch2，fftlen，gilen，nd)；

fftlen2=fftlen+gilen；

％衰减计算

spow=suln(ich3．2+qch3．“2)／nd．／para；

attn=0．郑敬5*spow*sr／br*10．“(．ebn0／10)；扒档

attn=sqrt(attn)；

％高斯自信道

[ich4，qeh4]=eomb(ich3，qch3，attn)；

％接收部分

％去除保护间隔

[ieh5，，qeh5]=girem(ich4，qch4，fftlen2，gilen，

nd)；

％FFr(离散傅里叶变换)

IX=ich5+qch5．*i：

ry=fit(Ⅸ)；

ich6=real(ry)；

qch6=imag(ry)；

％春丛乱QPSK解调

ieh7=ich6．／kmod；

qch7=qch6．／kmod；

[derrtxtata]=qpskdemod(ich7，qch7，para，nd，m1)；

％并串变换

demodatal=reshape(demodata，I，para*nd*rnl)；

％比特误码率(BER)

bit—errors=find(seldata～=demodatal)；

bit—error—count 2 size(bit—e／TOES，2)；

total—bits=size(demodatal，2)；

bit—error—rate=bit—error—count／total—bits；

fprintf(7％f＼n’，bit—eITor—rate)

％end offile

程序运行结果，输出误码率为：

>>0．037109

clear all

close all

clc

fprintf('OFDM信道估计仿真\n\n')

num_sc = 1200%-----------载波数目 2048简化为正蠢岩1200

num_symbol = 14 %--------------OFDM符号个数

data_symbol = [0,1,2,4,5,6,7,8,9,11,12,13]

pilot_symbol = [3,10]

cp_len = [160,144,144,144,144,144,144,160,144,144,144,144,144,144]

modulation_mode = 16%---------调制方式

q = 20

time_offset = 1 %us

time_offset = ceil(time_offset * 30.72) %20M bandwidth

SNR = 0:2:20%-------------信噪比取值

num_loop = 15%-----------------循环次数

num_ant = 2

num_bit_err=zeros(length(SNR),num_loop)

num_bit_err_dft=zeros(length(SNR),num_loop)

num_bit_err_ls=zeros(length(SNR),num_loop)

MSE=zeros(length(SNR),num_loop)

MSE1=zeros(length(SNR),num_loop)

MSE2=zeros(length(SNR),num_loop)

%%%%%%%%%%%%%%%%%%%%%%%Rx信号产生%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%---------------产生发送的随机序列举御————————————————————-

BitsLen = num_sc * length(data_symbol)

BitsTx = randint(1,BitsLen)

%---------------符号调制---------------------------------------—————

Modulated_Sequence=qammod(BitsTx,modulation_mode)

%---------------产生导档散频序列---------------------------------------———

prime_num = primes(num_sc)

prime_num = max(prime_num)

m = 0 : num_sc-1

xq = exp(-j*(pi*q*m.*(m+1)/prime_num))

pilot_symbols = xq( mod(m, prime_num) +1 )

pilot_symbols = pilot_symbols.'

%----------------导频插入-------------------------------------——————

piloted_ofdm_syms = zeros(num_sc, num_symbol)

piloted_ofdm_syms(:, data_symbol + 1) = reshape(Modulated_Sequence, num_sc, length(data_symbol))

piloted_ofdm_syms(:, pilot_symbol + 1) = repmat(pilot_symbols, 1, length(pilot_symbol))

%----------------IFFT变换—————————————————————————

time_signal = sqrt(num_sc) * ifft(piloted_ofdm_syms)

%----------------加循环前缀------------------------------------—————

Tx_data_trans = []

for k = 1 : num_symbol

add_cyclic_signal = [time_signal(num_sc - cp_len(k)+1 : num_sc, k)time_signal(:, k)].'

Tx_data_trans = [Tx_data_trans,add_cyclic_signal]

end

%%%%%%%%%%%%%%%%%%%%%%%主程序循环%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

for c1 = 1:length(SNR)

fprintf('\n\n\n仿真信噪比为%f\n\n',SNR(c1))

for num1 = 1:num_loop

%----------------信道处理--------------------------------------

%ADD awgn

Tx_signal_power = sum(abs(Tx_data_trans(:)).^2) / length(Tx_data_trans(:))

noise_var = Tx_signal_power/(10^(SNR(c1)/10))

Rx_data(1, :) = awgn(Tx_data_trans, SNR(c1), 'measured')

Rx_data(2, :) = awgn(Tx_data_trans, SNR(c1), 'measured')

%ADD TO 正时偏

Rx_data(1, :) = [zeros(1,time_offset),Rx_data(1, 1:length(Tx_data_trans)-time_offset),]

Rx_data(2, :) = [zeros(1,time_offset),Rx_data(2, 1:length(Tx_data_trans)-time_offset),]

% %ADD TO 负时偏

% Rx_data(1, :) = [Rx_data(1, time_offset+1:length(Tx_data_trans)),zeros(1,time_offset)]

% Rx_data(2, :) = [Rx_data(2, time_offset+1:length(Tx_data_trans)),zeros(1,time_offset)]

%----------------信号接收、去循环前缀、FFT变换-----------------

%Ant0

total_len=0

for k=1 : num_symbol

Rx_signal_matrix(:, k) = Rx_data(1, total_len+cp_len(k)+1 : total_len+cp_len(k)+num_sc).'

total_len = total_len+cp_len(k)+num_sc

end

Rx_carriers_ant0 = fft(Rx_signal_matrix)/sqrt(num_sc)

%Ant1

total_len=0

for k=1 : num_symbol

Rx_signal_matrix(:, k) = Rx_data(2, total_len+cp_len(k)+1 : total_len+cp_len(k)+num_sc).'

total_len = total_len+cp_len(k)+num_sc

end

Rx_carriers_ant1 = fft(Rx_signal_matrix)/sqrt(num_sc)

%----------------导频和数据提取--------------------------------

Rx_pilot_ant0 = Rx_carriers_ant0(:, pilot_symbol+1)

Rx_data_ant0 = Rx_carriers_ant0(:, data_symbol+1)

Rx_pilot_ant1 = Rx_carriers_ant1(:, pilot_symbol+1)

Rx_data_ant1 = Rx_carriers_ant1(:, data_symbol+1)

%----------------导频位置LS信道估计------------------------———

pilot_patt = repmat(pilot_symbols, 1, length(pilot_symbol))

pilot_esti_ant0 = Rx_pilot_ant0.*conj(pilot_patt)

pilot_esti_ant1 = Rx_pilot_ant1.*conj(pilot_patt)

%----------------LS估计的信道系数平铺———————————————

LS_channel_coeff_ant0 = [repmat(pilot_esti_ant0(:, 1), 1, length(data_symbol)/2), ...

repmat(pilot_esti_ant0(:, 2), 1, length(data_symbol)/2)]

LS_channel_coeff_ant1 = [repmat(pilot_esti_ant1(:, 1), 1, length(data_symbol)/2), ...

repmat(pilot_esti_ant1(:, 2), 1, length(data_symbol)/2)]

%----------------导频位置DFT信道估计----------------------------

Tx_pilot_estimate_ifft_ant0 = ifft(pilot_esti_ant0)

Tx_pilot_estimate_ifft_ant1 = ifft(pilot_esti_ant1)

stem(1:1200, Tx_pilot_estimate_ifft_ant0(:,1))

grid on

h_len = cp_len(2)

Tx_pilot_estimate_ifft_ant0(h_len+1 : num_sc-h_len, :) = 0

Tx_pilot_estimate_dft_ant0 = fft(Tx_pilot_estimate_ifft_ant0)

Tx_pilot_estimate_ifft_ant1(h_len+1 : num_sc-h_len, :) = 0

Tx_pilot_estimate_dft_ant1 = fft(Tx_pilot_estimate_ifft_ant1)

%----------------DFT估计的信道系数平铺———————————————

DFT_channel_coeff_ant0 = [repmat(Tx_pilot_estimate_dft_ant0(:, 1), 1, length(data_symbol)/2),...

repmat(Tx_pilot_estimate_dft_ant0(:, 2), 1, length(data_symbol)/2)]

DFT_channel_coeff_ant1 = [repmat(Tx_pilot_estimate_dft_ant1(:, 1), 1, length(data_symbol)/2),...

repmat(Tx_pilot_estimate_dft_ant1(:, 2), 1, length(data_symbol)/2)]

%----------------ZF OR MRC EQ----------------------

Tx_data_estimate_dft = (Rx_data_ant0.*conj(DFT_channel_coeff_ant0) + Rx_data_ant1.*conj(DFT_channel_coeff_ant1))...

./((abs(DFT_channel_coeff_ant0).^2) + (abs(DFT_channel_coeff_ant0).^2))

Tx_data_estimate_ls = (Rx_data_ant0.*conj(LS_channel_coeff_ant0) + Rx_data_ant1.*conj(LS_channel_coeff_ant1))...

./((abs(LS_channel_coeff_ant0).^2) + (abs(LS_channel_coeff_ant1).^2))

%----------------DFT符号解调------------------------------------

demod_in_dft=Tx_data_estimate_dft(:).'

demod_out_dft=qamdemod(demod_in_dft,modulation_mode)

%----------------LS符号解调------------------------------------

demod_in_ls=Tx_data_estimate_ls(:).'

demod_out_ls=qamdemod(demod_in_ls,modulation_mode)

%----------------误码率的计算-----------------------------------

for i=1:length(BitsTx)

if demod_out_dft(i)~=BitsTx(i)

num_bit_err_dft(c1,num1)=num_bit_err_dft(c1,num1)+1

end

if demod_out_ls(i)~=BitsTx(i)

num_bit_err_ls(c1,num1)=num_bit_err_ls(c1,num1)+1

end

end

end

end

BER_dft=mean(num_bit_err_dft.')/length(BitsTx)

BER_ls=mean(num_bit_err_ls.')/length(BitsTx)

%%%%%%%%%%%%%%%%%%%a%%%%%%%%主程序循环换结束%%%%%%%%%%%%%%%%%%%%%%%%%%%%

figure

semilogy(SNR,BER_dft,'-mp',SNR,BER_ls,'-k+')

xlabel('SNR')

ylabel('BER')

legend('DFT信道估计','LS信道估计')

title('OFDM系统的LS和DFT信道估计')

grid on

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