clear all; close all; clc;
format long
%本次仿真載頻為2GHz，帶寬1MHz，子載波數(shù)128個(gè)，cp為16
%子載波間隔為7.8125kHz
%一個(gè)ofdm符號(hào)長(zhǎng)度為128us，cp長(zhǎng)度為16us
%采用16QAM調(diào)制方式
%最大doppler頻率為132Hz
%多徑信道為5徑，功率延遲譜服從負(fù)指數(shù)分布~exp(-t/trms),trms=(1/4)*cp時(shí)長(zhǎng)，各徑延遲取為delay=[0 2e-6 4e-6 8e-6 12e-6]
pilot_inter=5;%導(dǎo)頻符號(hào)間隔為10,可以調(diào)整，看不同導(dǎo)頻間隔下的BER情況，和理論公式比較
pilot_symbol_bit=[0 0 0 1];%導(dǎo)頻為常數(shù)，對(duì)應(yīng)星座點(diǎn)1+3*j
cp_length=16;%cp長(zhǎng)度為16
SNR_dB=[0 2 4 6 8 10 12 14 16];
ls_err_ber=zeros(1,length(SNR_dB));
lmmse_err_ber=zeros(1,length(SNR_dB));
lr_lmmse_err_ber=zeros(1,length(SNR_dB));

for i=1:length(SNR_dB)%每個(gè)SNR點(diǎn)上仿真若干次
    ls_error_bit=0;
    lmmse_error_bit=0;
    lr_lmmse_error_bit=0;
    total_bit_num=0;
   loop_num=5; %共仿真10次
for l=1:loop_num
    ofdm_symbol_num=100;%每次仿真產(chǎn)生100個(gè)ofdm符號(hào),則每次仿真共有100×128個(gè)星座映射符號(hào)；16QAM調(diào)制下，1個(gè)星座映射符號(hào)包含4個(gè)bit
    bit_source=input_b(128,ofdm_symbol_num);%為每次仿真產(chǎn)生100個(gè)ofdm符號(hào)的比特個(gè)數(shù)，128為每個(gè)ofdm符號(hào)的子載波個(gè)數(shù)
    [nbit,mbit]=size(bit_source);
    total_bit_num=total_bit_num+nbit*mbit;
    
    map_out=map_16qam(bit_source);%對(duì)一次仿真符號(hào)塊進(jìn)行16QAM映射    
    [insert_pilot_out,pilot_num,pilot_sequence]=insert_pilot(pilot_inter,pilot_symbol_bit,map_out);%按塊狀導(dǎo)頻結(jié)構(gòu)，對(duì)映射后的結(jié)果插入導(dǎo)頻序列
    
    ofdm_modulation_out=ifft(insert_pilot_out,128);%作128點(diǎn)逆FFT運(yùn)算，完成ofdm調(diào)制
    ofdm_cp_out=insert_cp(ofdm_modulation_out,cp_length);%插入循環(huán)前綴
     
    
    %********************** 以下過(guò)程為ofdm符號(hào)通過(guò)頻率選擇性多徑信道 *************************
    num=5;
    %假設(shè)功率延遲譜服從負(fù)指數(shù)分布~exp(-t/trms),trms=(1/4)*cp時(shí)長(zhǎng)；
    %t在0~cp時(shí)長(zhǎng)上均勻分布
    %若cp時(shí)長(zhǎng)為16e-6s，可以取5徑延遲如下
    delay=[0 2e-6 4e-6 8e-6 12e-6];
    trms=4e-6;
    var_pow=10*log10(exp(-delay/trms));
    fd=132;%最大doppler頻率為132Hz
    t_interval=1e-6;%采樣間隔為1us
    counter=200000;%各徑信道的采樣點(diǎn)間隔，應(yīng)該大于信道采樣點(diǎn)數(shù)。由以上條件現(xiàn)在信道采樣點(diǎn)數(shù)
    count_begin=(l-1)*(5*counter);%每次仿真信道采樣的開(kāi)始位置
    trms_1=trms/t_interval;
    t_max=16e-6/t_interval;
    %信道采樣點(diǎn)數(shù)，每個(gè)調(diào)制符號(hào)采一個(gè)點(diǎn)
    passchan_ofdm_symbol=multipath_chann(ofdm_cp_out,num,var_pow,delay,fd,t_interval,counter,count_begin);
    
    %********************** 以上過(guò)程為ofdm符號(hào)通過(guò)頻率選擇性多徑信道 *************************    
    %********************** 以下過(guò)程為ofdm符號(hào)加高斯白噪聲 *************************
    snr=10^(SNR_dB(i)/10);
    [nnl,mml]=size(passchan_ofdm_symbol);
    spow=0;
    for k=1:nnl
      for b=1:mml
        spow=spow+real(passchan_ofdm_symbol(k,b))^2+imag(passchan_ofdm_symbol(k,b))^2;
      end
    end
    spow1=spow/(nnl*mml);        
    sgma=sqrt(spow1/(2*snr));%sgma如何計(jì)算，與當(dāng)前SNR和信號(hào)平均能量有關(guān)系
    receive_ofdm_symbol=add_noise(sgma,passchan_ofdm_symbol);%加入隨機(jī)高斯白噪聲，receive_ofdm_symbol為最終接收機(jī)收到的ofdm符號(hào)塊
    
    %********************** 以上過(guò)程為ofdm符號(hào)加高斯白噪聲 *************************
    cutcp_ofdm_symbol=cut_cp(receive_ofdm_symbol,cp_length);%去除循環(huán)前綴    
    ofdm_demodulation_out=fft(cutcp_ofdm_symbol,128);%作128點(diǎn)FFT運(yùn)算，完成ofdm解調(diào)
    
    %********************** 以下就是對(duì)接收ofdm信號(hào)進(jìn)行信道估計(jì)和信號(hào)檢測(cè)的過(guò)程************************
    ls_zf_detect_sig=ls_estimation(ofdm_demodulation_out,pilot_inter,pilot_sequence,pilot_num);%采用LS估計(jì)算法及迫零檢測(cè)得到的接收信號(hào)
    lmmse_zf_detect_sig=lmmse_estimation(ofdm_demodulation_out,pilot_inter,pilot_sequence,pilot_num,trms_1,t_max,snr);%采用LMMSE估計(jì)算法及迫零檢測(cè)得到的接收信號(hào)
    low_rank_lmmse_sig=lr_lmmse_estimation(ofdm_demodulation_out,pilot_inter,pilot_sequence,pilot_num,trms_1,t_max,snr,cp_length);%采用低秩LMMSE估計(jì)算法及迫零檢測(cè)得到的接收信號(hào)
    %********************** 以下就是對(duì)接收ofdm信號(hào)進(jìn)行信道估計(jì)和信號(hào)檢測(cè)的過(guò)程************************
    
    ls_receive_bit_sig=de_map(ls_zf_detect_sig);%16QAM解映射
    lmmse_receive_bit_sig=de_map(lmmse_zf_detect_sig);
    lr_lmmse_receive_bit_sig=de_map(low_rank_lmmse_sig);
    
    %以下過(guò)程統(tǒng)計(jì)各種估計(jì)算法得到的接收信號(hào)中的錯(cuò)誤比特?cái)?shù)
    ls_err_num=error_count(bit_source,ls_receive_bit_sig);
    lmmse_err_num=error_count(bit_source,lmmse_receive_bit_sig);
    lr_lmmse_err_num=error_count(bit_source,lr_lmmse_receive_bit_sig);
    
    ls_error_bit=ls_error_bit+ls_err_num;
    lmmse_error_bit=lmmse_error_bit+lmmse_err_num;
    lr_lmmse_error_bit=lr_lmmse_error_bit+lr_lmmse_err_num;
end
%計(jì)算各種估計(jì)算法的誤比特率

ls_err_ber(i)=ls_error_bit/total_bit_num;
lmmse_err_ber(i)=lmmse_error_bit/total_bit_num;
lr_lmmse_err_ber(i)=lr_lmmse_error_bit/total_bit_num;

end
plot(SNR_dB,ls_err_ber,'b-*')
hold on

plot(SNR_dB,lmmse_err_ber,'r-o')
plot(SNR_dB,lr_lmmse_err_ber,'g-+')
hold off