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(1) 基于生成对抗网络的智能反射面信道建模方法

智能反射面辅助通信系统中的信道建模是实现高效通信的关键技术基础。由于智能反射面具有无源特性,接入点到智能反射面以及智能反射面到用户之间的信道难以直接获取,而级联后的反射信道概率分布函数极为复杂,传统的信道建模方法难以准确刻画其统计特性。针对这一挑战,本研究提出了一种基于模型驱动生成对抗网络的信道建模框架,该框架充分利用反射信道的结构性特征,通过生成器网络学习信道的概率分布,判别器网络评估生成样本与真实信道的相似度,两者通过对抗训练不断优化,最终实现对复杂信道分布的精确建模。在多用户通信场景下,不同用户的反射信道之间存在空间相关性,本研究基于这种相关性设计了多用户联合信道建模框架,通过共享网络参数的方式同时对多个用户的信道进行建模,大幅减少了网络参数数量,提高了训练效率和建模精度。理论分析表明该框架对应的极大极小博弈问题存在可达的全局最优解,保证了算法的收敛性。仿真实验在单用户和多用户两种场景下验证了该方法的有效性,生成的信道样本在统计特性上与真实信道高度吻合,为后续的信道估计和系统优化提供了可靠的信道模型支撑。

(2) 基于深度残差学习的毫米波波束域信道估计网络

毫米波通信系统采用大规模天线阵列以补偿高频段的路径损耗,但射频链数量有限导致传统空间域信道估计方法面临巨大挑战。本研究引入透镜天线将毫米波空间域信道转换为波束域信道,利用波束域信道固有的稀疏性特征,提出了一种结合物理模型和数据驱动的深度学习信道估计网络。该网络将波束域信道估计问题建模为稀疏信号恢复问题,通过展开近似消息传递算法的迭代过程构建网络主体结构,使网络具有明确的物理意义和良好的可解释性。网络由两个级联的子网络组成,第一个子网络基于近似消息传递算法展开得到,负责获取波束域信道的粗略估计,该子网络的每一层对应算法的一次迭代,层间参数通过训练自适应学习获得。第二个子网络采用深度残差学习架构,通过多层卷积和跳跃连接进一步抑制信道估计中的噪声影响,对粗估计结果进行细化处理。残差学习机制使网络专注于学习估计误差的模式,避免了深层网络训练中的梯度消失问题,提高了网络的训练稳定性和收敛速度。实验结果表明该网络在各种信噪比条件下均能获得优于传统压缩感知方法的信道估计性能,同时具有较低的在线计算复杂度,满足实时通信系统的时延要求。

(3) 基于长短时记忆网络的时变信道跟踪与预测方案

在移动通信场景中,无线信道随时间持续变化,传统方法需要频繁发送导频信号进行信道估计,导致巨大的训练开销和频谱效率损失。本研究针对智能反射面辅助通信系统的时变信道特性,在所有链路信道服从高斯马尔可夫过程的假设下,提出了一种利用信道时间相关性降低训练开销的两阶段传输协议。第一阶段为信道跟踪阶段,根据接收到的导频信号利用卡尔曼滤波算法实时跟踪信道变化,卡尔曼滤波器通过预测和更新两个步骤递归估计信道状态,充分利用信道的时间相关性提高估计精度。第二阶段为信道预测阶段,基于跟踪阶段获得的信道序列,采用长短时记忆网络预测未来时刻的信道状态,从而在不发送导频的情况下获取信道信息。长短时记忆网络通过门控机制有效捕获信道序列中的长期依赖关系,输入门控制新信息的写入,遗忘门决定历史信息的保留程度,输出门调节隐藏状态的输出。

import numpy as np import torch import torch.nn as nn import torch.optim as optim from torch.utils.data import DataLoader, TensorDataset class Generator(nn.Module): def __init__(self, latent_dim, channel_dim): super(Generator, self).__init__() self.model = nn.Sequential( nn.Linear(latent_dim, 256), nn.LeakyReLU(0.2), nn.BatchNorm1d(256), nn.Linear(256, 512), nn.LeakyReLU(0.2), nn.BatchNorm1d(512), nn.Linear(512, channel_dim * 2), nn.Tanh() ) def forward(self, z): return self.model(z) class Discriminator(nn.Module): def __init__(self, channel_dim): super(Discriminator, self).__init__() self.model = nn.Sequential( nn.Linear(channel_dim * 2, 512), nn.LeakyReLU(0.2), nn.Dropout(0.3), nn.Linear(512, 256), nn.LeakyReLU(0.2), nn.Dropout(0.3), nn.Linear(256, 1), nn.Sigmoid() ) def forward(self, x): return self.model(x) class BeamDomainEstimationNet(nn.Module): def __init__(self, num_antennas, num_iterations): super(BeamDomainEstimationNet, self).__init__() self.num_iterations = num_iterations self.theta = nn.ParameterList([nn.Parameter(torch.ones(1) * 0.1) for _ in range(num_iterations)]) self.refinement = nn.Sequential( nn.Conv1d(2, 64, kernel_size=3, padding=1), nn.ReLU(), nn.Conv1d(64, 64, kernel_size=3, padding=1), nn.ReLU(), nn.Conv1d(64, 2, kernel_size=3, padding=1) ) def amp_iteration(self, y, A, x_hat, tau, iteration): z = y - torch.matmul(A, x_hat) r = x_hat + torch.matmul(A.T, z) x_hat = torch.sign(r) * torch.relu(torch.abs(r) - self.theta[iteration]) return x_hat def forward(self, y, A): batch_size = y.shape[0] x_hat = torch.zeros(batch_size, A.shape[1], dtype=torch.complex64) tau = 1.0 for i in range(self.num_iterations): x_hat = self.amp_iteration(y, A, x_hat, tau, i) x_real = torch.stack([x_hat.real, x_hat.imag], dim=1) x_refined = self.refinement(x_real) return torch.complex(x_refined[:, 0, :], x_refined[:, 1, :]) class LSTMChannelPredictor(nn.Module): def __init__(self, input_dim, hidden_dim, num_layers, output_dim): super(LSTMChannelPredictor, self).__init__() self.lstm = nn.LSTM(input_dim, hidden_dim, num_layers, batch_first=True, dropout=0.2) self.fc = nn.Sequential( nn.Linear(hidden_dim, hidden_dim // 2), nn.ReLU(), nn.Linear(hidden_dim // 2, output_dim) ) def forward(self, x): lstm_out, _ = self.lstm(x) predictions = self.fc(lstm_out[:, -1, :]) return predictions class KalmanFilter: def __init__(self, state_dim, obs_dim, process_noise, measurement_noise): self.state_dim = state_dim self.F = np.eye(state_dim) * 0.99 self.H = np.eye(obs_dim, state_dim) self.Q = np.eye(state_dim) * process_noise self.R = np.eye(obs_dim) * measurement_noise self.x = np.zeros(state_dim) self.P = np.eye(state_dim) def predict(self): self.x = self.F @ self.x self.P = self.F @ self.P @ self.F.T + self.Q return self.x def update(self, z): y = z - self.H @ self.x S = self.H @ self.P @ self.H.T + self.R K = self.P @ self.H.T @ np.linalg.inv(S) self.x = self.x + K @ y self.P = (np.eye(self.state_dim) - K @ self.H) @ self.P return self.x def train_gan(generator, discriminator, real_channels, epochs, batch_size, latent_dim): g_optimizer = optim.Adam(generator.parameters(), lr=0.0002, betas=(0.5, 0.999)) d_optimizer = optim.Adam(discriminator.parameters(), lr=0.0002, betas=(0.5, 0.999)) criterion = nn.BCELoss() dataset = TensorDataset(torch.FloatTensor(real_channels)) dataloader = DataLoader(dataset, batch_size=batch_size, shuffle=True) for epoch in range(epochs): for real_batch in dataloader: real_data = real_batch[0] batch_size_curr = real_data.size(0) real_labels = torch.ones(batch_size_curr, 1) fake_labels = torch.zeros(batch_size_curr, 1) d_optimizer.zero_grad() d_real_loss = criterion(discriminator(real_data), real_labels) z = torch.randn(batch_size_curr, latent_dim) fake_data = generator(z) d_fake_loss = criterion(discriminator(fake_data.detach()), fake_labels) d_loss = d_real_loss + d_fake_loss d_loss.backward() d_optimizer.step() g_optimizer.zero_grad() g_loss = criterion(discriminator(fake_data), real_labels) g_loss.backward() g_optimizer.step() return generator, discriminator def train_lstm_predictor(model, train_data, train_labels, epochs, batch_size): optimizer = optim.Adam(model.parameters(), lr=0.001) criterion = nn.MSELoss() dataset = TensorDataset(torch.FloatTensor(train_data), torch.FloatTensor(train_labels)) dataloader = DataLoader(dataset, batch_size=batch_size, shuffle=True) for epoch in range(epochs): total_loss = 0 for batch_x, batch_y in dataloader: optimizer.zero_grad() predictions = model(batch_x) loss = criterion(predictions, batch_y) loss.backward() optimizer.step() total_loss += loss.item() return model if __name__ == "__main__": latent_dim = 100 channel_dim = 64 num_antennas = 64 generator = Generator(latent_dim, channel_dim) discriminator = Discriminator(channel_dim) beam_net = BeamDomainEstimationNet(num_antennas, num_iterations=10) lstm_predictor = LSTMChannelPredictor(input_dim=channel_dim*2, hidden_dim=128, num_layers=2, output_dim=channel_dim*2) kalman = KalmanFilter(state_dim=channel_dim, obs_dim=channel_dim, process_noise=0.01, measurement_noise=0.1)

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