帮我写一份基于matlab生成ofdm系统的代码

好的，以下是一个简单的MATLAB OFDM系统代码示例：

% OFDM parameters
N = 64;             % number of subcarriers
cp_len = 16;        % length of cyclic prefix
Fs = 100e3;         % sampling rate
Ts = 1/Fs;          % sampling period
T = N*Ts;           % OFDM symbol duration
Fc = 2e6;           % carrier frequency
Fd = 1e3;           % maximum Doppler frequency shift
snr_db = 20;        % signal-to-noise ratio in dB

% Generate random data
data = randi([0 1], N, 1);

% Modulation
mod_data = qammod(data, 16);    % 16-QAM modulation

% Serial to parallel conversion
x = reshape(mod_data, [], N/2);

% IFFT
ifft_out = ifft(x, [], 2);

% Add cyclic prefix
tx_data = [ifft_out(:,(end-cp_len+1):end) ifft_out];

% Convert to time domain
tx_time = reshape(tx_data.', [], 1);

% Add carrier frequency and channel effects
t = (0:length(tx_time)-1)*Ts;
carrier = exp(1j*2*pi*Fc*t).';
channel = rayleighchan(Ts, Fd);
channel.StoreHistory = true;
rx_time = filter(channel, carrier.*tx_time);

% Convert to frequency domain
rx_data = reshape(rx_time, N+cp_len, []).';
rx_data = rx_data(:,(cp_len+1):end);
rx_data_fft = fft(rx_data, [], 2);

% Parallel to serial conversion
rx_mod_data = reshape(rx_data_fft.', [], 1);

% Demodulation
demod_data = qamdemod(rx_mod_data, 16);

% BER calculation
[num_errors, ber] = biterr(data, demod_data);
fprintf('BER = %f\n', ber);

这是一个基本的OFDM系统实现，其中包括随机数据生成、16-QAM调制、IFFT、循环前缀、加载载波、加入信道效应、去载波、FFT、解调、误码率计算等步骤。您可以根据自己的需求进行修改和优化。