OFDM多径时延估计MATLAB代码

以下是一个基于MATLAB的OFDM多径时延估计代码示例：

clear all;
close all;

% 设计OFDM系统参数
N = 64; %子载波数
cp_len = 16; %循环前缀长度
fft_size = N + cp_len; %FFT点数
num_ofdm_symbols = 100; %OFDM符号数

% 生成随机发送信号
tx_signal = randn(1, N*num_ofdm_symbols);

% 建立多径信道
channel_taps = [0.8, 0.6, 0.4, 0.2]; % 4个多径的衰落系数
channel_delays = [0, 1, 3, 5]; % 4个多径的时延
channel = zeros(1, 100*N+4*cp_len); % 初始化频域信道
for i = 1:length(channel_taps)
    channel_tap = channel_taps(i);
    channel_delay = channel_delays(i);
    channel_freq_resp = zeros(1, fft_size);
    channel_freq_resp(channel_delay+1) = channel_tap;
    channel_freq_resp(fft_size-channel_delay+1) = channel_tap;
    channel_imp_resp = ifft(channel_freq_resp);
    channel_conv = conv(tx_signal, channel_imp_resp);
    channel(1+(i-1)*cp_len : i*N+(i-1)*cp_len) = channel_conv(1+(i-1)*N : i*N+(i-1)*N+cp_len);
end

% 加入噪声
noise_power = 0.001;
noise = sqrt(noise_power/2) * (randn(size(channel)) + 1j*randn(size(channel)));

% 接收信号
rx_signal = channel + noise;

% 时域信号转到频域
rx_signal_reshape = reshape(rx_signal(1:N*num_ofdm_symbols), N, num_ofdm_symbols);
rx_signal_fft = fft(rx_signal_reshape);

% 计算自相关矩阵
auto_corr_mat = zeros(N, N);
for i = 1:N
    for j = 1:N
        auto_corr_mat(i,j) = dot(rx_signal_fft(i,:), conj(rx_signal_fft(j,:)));
    end
end

% 估计时延
[eig_vec, eig_val] = eig(auto_corr_mat);
eig_val = diag(eig_val);
[~, max_eig_val_idx] = max(eig_val);
delay_estimate = mod(max_eig_val_idx-1, N);

该代码生成随机发送信号，建立了一个具有4个多径的信道，并加入了噪声。然后将接收信号转换为频域信号，计算了自相关矩阵，并利用最大特征值法估计了时延。