用matlab编写一段程序实现OFMD功能并对每行程序代码进行解释
时间: 2024-01-17 12:03:11 浏览: 94
好的,以下是用MATLAB编写OFDM系统的代码,并对每一行进行了解释。
```matlab
% OFDM system simulation
clc; clear all; close all;
%% Define parameters
N = 64; % Number of subcarriers
cp_len = 16; % Length of cyclic prefix
EbN0dB = 0:5:30; % Eb/N0 values to be simulated
num_frames = 10^2; % Number of OFDM frames to be simulated
SNR = EbN0dB + 10*log10(N/(N+cp_len)); % SNR values
%% Generate data symbols
data = randi([0 1],N,num_frames); % Generate random bits
data_mod = 2*data-1; % BPSK modulation
```
这一段代码主要定义了OFDM系统中需要使用的参数,其中N为子载波数量,cp_len为循环前缀长度,EbN0dB为信噪比范围,num_frames为OFDM帧数,SNR为信噪比,data为随机数据位,data_mod为BPSK调制后的数据。
```matlab
%% OFDM transmission
for k = 1:length(EbN0dB)
for frame_cnt = 1:num_frames
% Serial to parallel conversion
data_mod_p = reshape(data_mod(:,frame_cnt),N,1);
% QAM modulation
x = ifft(data_mod_p);
% Cyclic prefix addition
x_with_cp = [x(end-cp_len+1:end);x];
% Channel
h = 1/sqrt(2)*(randn(cp_len+N,1)+1j*randn(cp_len+N,1)); % Rayleigh channel
y = conv(h,x_with_cp);
y = y(cp_len+1:end-cp_len);
% AWGN addition
noise = 1/sqrt(2)*(randn(N,1)+1j*randn(N,1)); % Complex Gaussian noise
noise_power = norm(noise)^2/N;
signal_power = norm(y)^2/N;
noise_energy = noise_power*10^(-SNR(k)/10);
scale_factor = sqrt(noise_energy/signal_power);
y_noise = y + scale_factor*noise;
% Receiver
% Remove cyclic prefix
y_no_cp = y_noise(cp_len+1:end);
% FFT operation
y_fft = fft(y_no_cp);
% Parallel to serial conversion
y_p2s = reshape(y_fft,N,1);
% QAM demodulation
y_demod = real(y_p2s)>0;
% Bit error calculation
err = sum(xor(data(:,frame_cnt),y_demod));
ber(k,frame_cnt) = err/N;
end
end
```
这一段代码是OFDM系统的传输过程,包括串并转换、QAM调制、循环前缀加入、信道传输、AWGN添加以及接收端的处理。其中,通过循环遍历每个信噪比和每个OFDM帧,来模拟整个系统的性能。最后,计算误码率(BER)并将其存储在ber矩阵中。
```matlab
%% Plot results
ber_avg = mean(ber,2); % Average BER over all frames
ber_theory = 0.5*erfc(sqrt(10.^(EbN0dB/10))); % Theoretical BER
figure;
semilogy(EbN0dB,ber_avg,'bo-','LineWidth',2,'MarkerSize',8);
hold on;
semilogy(EbN0dB,ber_theory,'rx--','LineWidth',2,'MarkerSize',8);
axis([0 30 10^-6 1]);
grid on;
legend('Simulation','Theory');
xlabel('Eb/N0 (dB)');
ylabel('BER');
title('OFDM system performance');
```
这一段代码主要是绘制结果,包括绘制平均BER和理论BER的semilogy图,并设置图例、坐标轴和标题。
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