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：

%% 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');