传真(Fax)编程

开发平台：
Matlab

channel.m：源码内容
							function recv_signal = channel( transmit_signal,h_time, ch, N_Tx_ant, N_Rx_ant ,...
    PreNoiseLen,PostNoiseLen, var_noise,N_subc,PrefixRatio,N_sym,...
    delta_fc,T_sample,FreqSyn,AddChFreq)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% 多径多天线信道
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
if ~AddChFreq
    
    len = length(transmit_signal) + max(ch.Delay_sample) + PreNoiseLen + PostNoiseLen;
    
    recv_signal = zeros(1,len,N_Rx_ant);
    tmp_recv = zeros(1,length(transmit_signal) + max(ch.Delay_sample),N_Rx_ant);
    
    % 对每条接收天线的信号, 是N_tx_ant个数据的叠加
    for n_r = 1:N_Rx_ant
        tmp_signal = zeros(1,length(transmit_signal) + max(ch.Delay_sample) );
        for n_t = 1:N_Tx_ant
            
            % 对单天线信道, 是N_path条径的延时叠加. h_time是时域信道的系数矩阵
            % 首先取一对天线,h_time(:,:,(n_t-1)*N_Tx_ant + n_r)是N_path行, N_sym列的矩阵
            % 把h_time扩展为每个OFDM符号有N_subc*(1 + PrefixRatio)个衰落系数
            % 乘上对应的时域样点.
            
            max_d = max(ch.Delay_sample);
            for p = 1:ch.N_path
                
                % 信道响应的使用：如4发2收天线，先取h_time的第1到第4行，作为第1~4发送天线，第1条接收天线
                % 的信道响应。然后取h_time的第5到第8行，作为第1~4发送天线，第2条接收天线的信道响应
                
                ch_coeff = h_time( p ,:, n_t + N_Tx_ant*(n_r - 1));
                
                ch_coeff = reshape( repmat(ch_coeff, N_subc*(1 + PrefixRatio),1) ,...
                    1,N_subc*(1 + PrefixRatio)*N_sym );
                
                delay = ch.Delay_sample(p);
                
                % 然后把N_path条路径延时叠加,得到长度为length(transmit_signal) + max(ch.Delay_sample)的向量
                tmp_signal = tmp_signal + ...
                    [zeros(1, delay)  transmit_signal(1,:,n_t).*ch_coeff  zeros(1,max_d - delay)];
            end
            
            % 把不同发送天线的信号叠加
            tmp_recv(1,:,n_r) = tmp_recv(1,:,n_r) + tmp_signal;
            
        end
    end
    
    % 在每条接收天线的信号加噪声,并加前噪声和后噪声,用于定时同步算法
    recv_signal = [ zeros(1,PreNoiseLen,N_Rx_ant) tmp_recv zeros(1,PostNoiseLen,N_Rx_ant) ];
    noise = sqrt(var_noise)*( randn(1,len,N_Rx_ant) + j*randn(1,len,N_Rx_ant) );
    recv_signal = recv_signal + noise;
    
    % 加载波频偏
    if FreqSyn
        idx = repmat([0:length(recv_signal)-1],[1,1,N_Rx_ant]);
        recv_signal = recv_signal.*exp(j*2*pi*delta_fc*idx*T_sample);
    end
    
    % 加抽样频偏, 下一步完成
    
else
    recv_signal = NaN;
end

						