pilot = uniformPilotsGen(pilot_l); pilot = pilot{1,1}; pilot_user = repmat(pilot,[1 users])';
时间: 2023-12-11 13:32:22 浏览: 41
根据提供的引用内容,pilot = uniformPilotsGen(pilot_l)是生成长度为pilot_l的均匀pilot序列,pilot = pilot{1,1}是将生成的pilot序列从cell数组中提取出来。而pilot_user = repmat(pilot,[1 users])'是将pilot序列按照用户数进行复制并转置,生成一个大小为[users, pilot_l]的矩阵pilot_user。
因此,pilot_user是一个大小为[users, pilot_l]的矩阵,其中每一行都是一个长度为pilot_l的均匀pilot序列。
相关问题
给出一个mimo-ofdm信道估计的代码
以下是一个基于最小二乘法的MIMO-OFDM信道估计的MATLAB代码示例:
```matlab
% OFDM参数设置
N = 64; % 子载波数
cp_len = 16; % 循环前缀长度
qam_size = 4; % 星座大小
n_symbols = 100; % OFDM符号数
pilot_spacing = 4; % 导频间隔
% 生成QPSK调制的随机数据
data = randi([0 qam_size-1], N-4, n_symbols);
mod_data = qammod(data, qam_size);
% 生成导频序列
pilot_seq = zeros(N, 1);
pilot_seq(1:pilot_spacing:end) = 1;
pilot_seq = repmat(pilot_seq, 1, n_symbols);
pilot_seq = qammod(0:pilot_spacing:(n_symbols-1)*pilot_spacing, qam_size);
% 将数据和导频序列合并
tx_data = zeros(N, n_symbols);
tx_data(3:end-2, :) = mod_data;
tx_data(1:2, :) = tx_data(end-1:end, :);
tx_data(end-1:end, :) = tx_data(3:4, :);
tx_data(5:pilot_spacing:end, :) = pilot_seq;
% 生成信道矩阵
H = randn(2, 2) + 1i*randn(2, 2);
% 发送信号并加噪声
rx_data = zeros(N, n_symbols);
for ii = 1:n_symbols
% OFDM调制
tx_ofdm = ifft(tx_data(:, ii));
% 加循环前缀
tx_cp = [tx_ofdm(end-cp_len+1:end); tx_ofdm];
% 通过信道
rx_cp = H * tx_cp;
% 去除循环前缀
rx_ofdm = rx_cp(cp_len+1:end);
% OFDM解调
rx_data(:, ii) = fft(rx_ofdm);
end
% 提取导频并计算信道估计
pilot_idx = 5:pilot_spacing:N;
pilot_data = rx_data(pilot_idx, :);
pilot_seq = pilot_seq(pilot_idx, :);
H_est = zeros(2, 2);
for ii = 1:n_symbols
H_est = H_est + pilot_data(:, ii) * pilot_seq(:, ii)';
end
H_est = H_est / (n_symbols * pilot_spacing);
% 计算误差
H_error = H - H_est;
mse = mean(abs(H_error(:)).^2);
```
此代码生成了一个基于QPSK调制的OFDM信号,通过随机信道传输,并在接收端使用最小二乘法估计信道。
帮我用matlab写出一个ofdm系统的仿真
好的,以下是一个简单的OFDM系统仿真代码,其中包含了基本的参数设置、信道模型、调制解调、信道估计、FFT/IFFT等主要部分:
```matlab
%% OFDM系统仿真
clear all; close all; clc;
%% 参数设置
N = 64; % 子载波数
cp_len = 16; % 循环前缀长度
mod_order = 4; % 调制阶数
num_symbols = 10000; % 发送符号数
snr_vec = 0:5:30; % 信噪比向量
%% 信道模型
EbNo_vec = 10.^(snr_vec/10);
for i = 1:length(EbNo_vec)
snr = EbNo_vec(i)*log2(mod_order)*N/(N+cp_len); % 等效信噪比
chan = comm.AWGNChannel('NoiseMethod', 'Signal to noise ratio (SNR)', 'SNR', snr);
%% 调制解调
mod = comm.QAMModulator('ModulationOrder', mod_order, 'BitInput', true);
demod = comm.QAMDemodulator('ModulationOrder', mod_order, 'BitOutput', true);
%% 信道估计
ofdm_demod = comm.OFDMDemodulator('FFTLength', N, 'CyclicPrefixLength', cp_len);
pilot_symbols = mod(randi([0 1], N/4, 1));
pilot_pos = [12; 26; 40; 54];
pilot_symbols_pos = zeros(N, 1);
pilot_symbols_pos(pilot_pos) = pilot_symbols;
pilot_symbols_pos = ifft(pilot_symbols_pos, N);
pilot_symbols_pos = [pilot_symbols_pos(N-cp_len+1:N); pilot_symbols_pos];
pilot_symbols_pos = repmat(pilot_symbols_pos, num_symbols, 1);
pilot_symbols_pos = chan(pilot_symbols_pos);
pilot_symbols_pos = ofdm_demod(pilot_symbols_pos);
pilot_symbols_pos = pilot_symbols_pos(pilot_pos, :);
h_est = interp1(pilot_pos, pilot_symbols_pos, 1:N, 'linear', 'extrap');
h_est = fft(h_est, N);
h_est = repmat(h_est, num_symbols, 1);
%% 发送和接收
data_symbols = mod(randi([0 1], (N-mod_order)/2*num_symbols, 1));
data_symbols = reshape(data_symbols, [], (N-mod_order)/2);
data_symbols = [zeros(num_symbols, mod_order/2) data_symbols zeros(num_symbols, mod_order/2)];
data_symbols = [data_symbols(:, 1:(N-mod_order)/2-mod_order/2) pilot_symbols data_symbols(:, (N-mod_order)/2-mod_order/2+1:end)];
data_symbols_pos = ifft(data_symbols, N, 2);
data_symbols_pos = [data_symbols_pos(:, N-cp_len+1:N) data_symbols_pos];
data_symbols_pos = chan(data_symbols_pos);
data_symbols_pos = ofdm_demod(data_symbols_pos);
data_symbols_pos = data_symbols_pos(:, mod_order/2+1:N-mod_order/2);
data_symbols_pos = data_symbols_pos./h_est;
data_symbols_pos = demod(data_symbols_pos(:));
%% BER计算
[~, ber(i)] = biterr(data_symbols_pos, randi([0 1], size(data_symbols_pos)));
end
%% BER曲线绘制
figure; semilogy(snr_vec, ber, '-o'); grid on;
xlabel('SNR (dB)'); ylabel('BER');
title('OFDM系统仿真');
```
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