main.m

OFDM的详细仿真代码

    FrameTiming = 1;         
    Window1 = 128;          % 帧定时算法的窗口宽度
    Threshold1 = 0.4;       % 帧定时算法门限
    Delay1 = 128;            % 帧定时延时相关算法的延时样点数
    
    % 载波频偏粗估计
    WinStart = 128*4;
    WinSize = 128;
    Delay2 = 128*4;
    
    % 符号定时算法
    Window2 = 256;         % 和已知序列求相关,序列的长度
    TimingAhead = 0;        % 定时提前的样点数
    
    % 载波频偏粗估计
    WinStart2 = 256; 
    WinSize2 = 512;
    Delay3 = 512;
    
end

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% 二. 仿真主体程序部分


% Eb/No信噪比循环
snr_idx = 1;
for Eb_No_dB = Eb_NoStart:Eb_NoInterval:Eb_NoEnd  
    Eb_No_dB
    Eb_No = 10^(Eb_No_dB/10); 
    var_noise = Eb/(2*Eb_No);       % 噪声样点的功率
    %var_noise = 0.01;              % 测试
    tic;                            % 计算时间开始
    
    % OFDM帧/数据包循环
    for frame = 1:N_frame                       
        
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        % 1. 信道参数产生部分
        % 产生不同用户(cell区分), 不同收发天线对(矩阵的第三维区分),不同OFDM符号
        % 时间(矩阵列区分), 多径信道不同时延径(矩阵行区分)的时域信道响应
        h_time = cell(1,N_user);
        H_freq = cell(1,N_user);
        
        for u = 1:N_user
            
            % 得到时域信道的参数
            h_time{u} = time_channel_para( ch{u}, N_Tx_ant, N_Rx_ant,N_sym, T_sym, fs, N_subc, ...
                PrefixRatio,N_frame,frame,N_tran_sym);
            
            % 由信道时域响应,得到信道的频域响应
            H_freq{u} = to_freq_channel( h_time{u}, ch{u} ,N_subc ,N_sym, N_Tx_ant,...
                N_Rx_ant,N_tran_sym);
            
        end
        
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        % 2. 发射机部分
        
        % 多用户数据生成模块
        [user_bit,user_bit_cnt]  = user_bit_gen( N_user, N_data ,N_sym , Modulation );
        
        % 信道编码模块, 包括RS编码, 卷积编码等
        coded_user_bit = channel_coding( user_bit , UserRS_Coding , ...
            UserTrellis,TraceBackLen, TurnOn.ChannelCoding );
        
        % 自适应调制和多用户复用模块
        % 有自适应调制 , 使用固定或动态子载波分配
        if TurnOn.AdptMod           
            [user_subc_alloc , mod_subc ,pwr_subc, pad_bit_cnt] = adpt_mod_para... 
                ( coded_user_bit,N_sym,Idx_data,AllocMethod,AdptMethod ,...
                H_freq,var_noise,TargetBer );
            
            % 无自适应调制 , 使用固定子载波分配            
        else                        
            [user_subc_alloc , mod_subc ,pwr_subc, pad_bit_cnt]  = adpt_mod_para...
                ( coded_user_bit,N_sym,Idx_data ,AllocMethod ); 
        end
        
        % 按照给定的每用户,每子载波的调制方式,进行自适应调制
        mod_sym =  modulator(coded_user_bit,user_subc_alloc,mod_subc,...
            pwr_subc, pad_bit_cnt ,N_subc, N_sym,TurnOn.AdptMod );
        
        % 发送分集, 使用空时编码
        st_coded = st_coding( mod_sym,N_Tx_ant,ST_Code);
        
        % 加导频
        pilot_added = pilot_insert(st_coded,Idx_pilot,PilotValue);
        
        % OFDM调制,加前导序列. 如果使用发送分集,则输出多条天线的信号
        [transmit_signal known_training] = ofdm_mod(st_coded,PrefixRatio,N_subc,N_sym,N_used,...
            Idx_used,N_Tx_ant,N_tran_sym);
        
        % 加发送机相位噪声, 下一步完成               
        %       transmit_signal = phase_noise(transmit_signal,TurnOn.PhaseNoise);
        
        % clear mod_sym, coded_user_bit;
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        % 3. 多天线多径信道部分
        for u = 1:N_user        % 多个用户接收机的循环
            
            % 信道和接收机区分开不同用户的原因:
            % 1) 每个用户(移动台)的信道功率时延谱和衰落系数是不同的, 需要区别
            % 2) 自适应调制和子载波分配算法中, 需要知道每个用户的信道响应
            
            recv_signal = channel( transmit_signal,h_time{u}, ch{u}, N_Tx_ant, N_Rx_ant,...
                PreNoiseLen,PostNoiseLen , var_noise,N_subc,PrefixRatio,N_sym,...
                delta_fc,T_sample,N_tran_sym,TurnOn.FreqSyn );
            
            %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
            % 4. 接收机部分
            
            % 加接收机相位噪声, 下一步完成    
            % recv_signal = phase_noise(recv_signal ,TurnOn.PhaseNoise);
            
            % 接收机帧定时(包检测,粗定时)
            [recv_frame, err_frame_timing] = frame_timing( recv_signal ,Window1, Threshold1,...
                Delay1,PreNoiseLen, PostNoiseLen, N_subc, PrefixRatio, N_sym, FrameTiming, N_tran_sym, N_Rx_ant ,...
                TurnOn.Timing);
            
            % 粗频偏估计 (整数倍的频偏估计). 也可以在频域做,使用freq_syn_freqdomain模块
            [coarse_freq_out, offset1] = freq_syn_timedomain( recv_frame, WinStart, WinSize, Delay2, T_sample,...
                N_Rx_ant,TurnOn.FreqSyn );
            
            % 符号定时（精定时）
            [timed_sym , err_sym_timing] = sym_timing( coarse_freq_out ,N_subc, PrefixRatio, N_sym, N_tran_sym,...
                known_training,Window2,TimingAhead, N_Rx_ant, TurnOn.Timing);
            
            % 精频偏估计(分数倍的频偏估计),如果粗频偏估计已经满足估计器的MSE要求， 则可以不使用此模块
            % 调用和粗频偏估计相同的函数，只是输入参数不同
            [fine_freq_out,offset2] = freq_syn_timedomain( timed_sym,WinStart2, WinSize2, Delay3, T_sample,...
                N_Rx_ant,TurnOn.FreqSyn );
            
            % 可选的时域均衡器,下一步完成.如果使用了频域均衡, 则不需要
            % equalized_sym = equalizer_timedomain(timed_sym ,TurnOn.TimeDomainEq);
            
            % OFDM解调,去前导序列
            [training_sym ,data_sym] = ofdm_demod(fine_freq_out,PrefixRatio,N_subc,N_sym,N_tran_sym,N_Rx_ant);
            
            % 如果在时域不进行整数倍的频偏估计, 则在频域进行.下一步完成.
            %             freq_offset_corrected = freq_syn_freqdomain( data_sym,TurnOn.FreqSyn );
            
            % 频域信道估计器, 如果使用了时域均衡, 则不使用此模块
            % channel_est = zeros(N_subc,1);
            % [channel_est(Idx_used,1) , mse_ce] = estimator( training_sym(Idx_used,1) , known_training(Idx_used,2) , ...
            %              CE_Method , CE_SubcRemain , H_freq{u}(Idx_used,2));
            
            [channel_est , mse_ce] = channel_estimator( training_sym ,CE_Method,CE_Method2,...
                CE_SubcRemain,H_freq{u},known_training,N_Tx_ant,N_Rx_ant, N_subc,N_used,Idx_used,...
                Modulation,var_noise,TurnOn.ChannelEst );
            
            % 使用数据OFDM符号中的导频进行载波相位跟踪和补偿,下一步完成
            % phase_err_corrected = phase_tracing( data_sym,freq_offset_corrected ,TurnOn.PhaseTrace );
            
            % 使用数据OFDM符号中的导频抽样频偏的估计和补偿, 下一步完成         
            %             sampling_err_corrected = sampling_syn( data_sym,phase_err_corrected ,TurnOn.SamplingSyn );
            
            % 在频域加入理想信道响应,测试目的
            %             rev = zeros(N_subc, N_sym  , N_Rx_ant );
            %             for n_r = 1:N_Rx_ant
            %                 for n_t = 1:N_Tx_ant
            %                     rev(:,:,n_r) = rev(:,:,n_r) + data_sym(:,:,n_t).*...
            %                                     repmat(H_freq{u}(:,1,(n_t-1)*N_Rx_ant + n_r), 1, N_sym );
            %                 end
            %             end
            %              data_sym = rev;
            
            % 接收机分集处理和空时解码
            
            st_decoded = st_decoding( data_sym,channel_est,N_Tx_ant, N_Rx_ant ,ST_Code ,Idx_data);
            
            % 根据每用户,每子载波的调制方式,进行解调
            demod_user_bit = demodulator( st_decoded, user_subc_alloc{u} ,mod_subc{u} ,...
                pad_bit_cnt(u),N_sym,TurnOn.AdptMod);            
            
            % 信道解码, 包括RS解码, 卷积码Viterbi编码等
            decoded_user_bit{u} = channel_decoding ( demod_user_bit , UserRS_Coding(:,u) ,... 
                UserTrellis(u) ,TraceBackLen, user_bit_cnt(u) , TurnOn.ChannelCoding );
            
            % 本帧,本信噪比下,本用户的性能统计
            bit_err = sum(abs(decoded_user_bit{u} - user_bit{u}));
            
            if TurnOn.FreqSyn 
                freq_err = delta_fc - (offset1 + offset2);
            else
                freq_err = 0;
            end   
            
            user_bit_err{u}(frame,snr_idx) = bit_err ;
            mse_ce_acc{u}(frame,snr_idx) = mse_ce;
            frame_timing_acc{u}(frame,snr_idx) = err_frame_timing ;
            freq_syn_acc{u}(frame,snr_idx) = freq_err ;
            
            
        end                  % 多个用户接收机的循环结束 
        
        % 实时显示仿真性能
        fprintf('Eb/No:%d dB\tFrame No.:%d  Err Bits:%d\tCh.Est. MSE:%f  Timing Err(Sample):%d\tFreq.Syn. Err(Hz):%d\n',...
            Eb_No_dB, frame, bit_err, mse_ce, err_frame_timing , freq_err);
        
    end                      % OFDM帧/数据包循环结束     
    
    timer(snr_idx) = toc     % 计算时间结束
    snr_idx = snr_idx + 1;
    
    save saved_data.mat;     % 保存数据
    
end                      % Eb/No信噪比循环结束                     

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% 5. 性能评估部分,可以保存需要的数据,并对目标性能数据进行操作
% 如画图, 比较,进一步计算得到结论等
performance_eval;


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% 仿真程序结尾