%% 基于ATG的机载WiFi系统仿真 clear all; close all; clc; rng(2025); % ================ 系统参数配置 ================ carrier_freq = 1.5e9; % 载波频率1.5GHz (L波段) velocity = 1000; % 飞行速度(km/h) num_users = 50; % 接入用户数量 mod_order = 4; % 调制阶数(QPSK) SNR_dB = 15; % 信噪比(dB) fs = 10e6; % 采样率10MHz frame_size = 1024; % 每用户数据长度 % ================ 预处理计算 ================ c = 3e8; % 光速 max_doppler = (velocity/3.6)*carrier_freq/c; % 最大多普勒频移 Ts = 1/fs; % 采样间隔 % ================ 信道模型初始化 ================ rayleigh_chan = comm.RayleighChannel(... 'SampleRate', fs,... 'PathDelays', [0 Ts], ... 'AveragePathGains', [0 -3],... 'MaximumDopplerShift', max_doppler, ... 'RandomStream', 'mt19937ar with seed', ...% 增加随机流设置 'Seed', 2025); % 固定信道模型随机种子 % ================ 数据生成与调制 ================ % 生成随机二进制数据 tx_bits = randi([0 1], num_users, frame_size); % QPSK调制（手动功率归一化） M = mod_order; constellation = qammod(0:M-1, M); norm_factor = sqrt(mean(abs(constellation).^2)); tx_symbols = qammod(tx_bits(:), M, 'InputType','bit') / norm_factor; tx_symbols = reshape(tx_symbols, num_users, []); % ================ 信道传输 ================ % 多径效应 chan_out = rayleigh_chan(tx_symbols(:)); % 添加高斯白噪声 rx_signal = awgn(chan_out, SNR_dB, 'measured'); % ================ 多普勒补偿 ================ t = (0:length(rx_signal)-1)/fs; fd_comp = exp(-1j*2*pi*max_doppler*t.'); compensated_signal = rx_signal .* fd_comp; % ================ 接收机处理 ================ % 信号整形 rx_reshape = reshape(compensated_signal, num_users, []); % 简易均衡（幅度归一化） rx_eq = rx_reshape ./ mean(abs(rx_reshape), 2); % QPSK解调 rx_bits = qamdemod(rx_eq*norm_factor, M, 'OutputType','bit'); % ================ 性能分析 ================ % 误码率计算 [bit_errors, ber] = biterr(tx_bits(:), rx_bits(:)); % 吞吐量计算 valid_bits = sum(rx_bits(:) == tx_bits(:)); throughput = valid_bits / (length(rx_signal)/fs) / 1e6; % Mbps % 结果显示 fprintf('\n======== 仿真结果 ========\n'); fprintf('载波频率: %.1f GHz\n', carrier_freq/1e9); fprintf('飞行速度: %d km/h\n', velocity); fprintf('用户数量: %d\n', num_users); fprintf('信噪比: %d dB\n', SNR_dB); fprintf('误码率: %.4f\n', ber); fprintf('系统吞吐量: %.2f Mbps\n\n', throughput); % ================ 动态TDMA调度演示 ================ traffic_load = 0.8; % 网络负载系数 slot_allocation = dynamicTDMA(num_users, traffic_load); figure; bar(slot_allocation*100); title('TDMA时隙分配比例'); xlabel('用户编号'); ylabel('时隙占比(%)'); grid on; % ================ BER性能曲线绘制 ================ SNR_range = 5:2:20; ber_curve = zeros(size(SNR_range)); for snr_idx = 1:length(SNR_range) % 临时信道传输 temp_signal = awgn(tx_symbols(:), SNR_range(snr_idx), 'measured'); % 多普勒补偿 temp_comp = temp_signal .* fd_comp(1:length(temp_signal)); % 解调 temp_bits = qamdemod(reshape(temp_comp,[],num_users)*norm_factor, M, 'OutputType','bit'); % BER计算 [~, ber_curve(snr_idx)] = biterr(tx_bits(:), temp_bits(:)); end figure; semilogy(SNR_range, ber_curve, 'ro-', 'LineWidth', 2); title('误码率性能曲线'); xlabel('SNR (dB)'); ylabel('BER'); grid on; set(gca, 'YScale', 'log'); % ================ TDMA调度函数 ================ function slots = dynamicTDMA(user_num, traffic) base_slot = 20; % 基准时隙20ms load_factor = 1 + log10(traffic+eps); % 防止log(0) slots = base_slot * load_factor * rand(1, user_num); slots = slots / sum(slots); % 归一化 end 对以上代码进行实验结果对比分析，将飞行速度改为1200km/h,用户数量改为80，信噪比改为10dB，并说明一下为什么要这样对比