1-bit Precoding Algorithm for Massive MIMO OFDM Downlink Systems with Deep Learning
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摘要: 大规模多输入多输出(MIMO)系统中通过在基站端配备数百根天线,在提高频谱利用效率的同时,也带来了系统成本的增加。本课题组之前提出了一种适用于下行大规模MIMO正交频分复用(OFDM)系统的收敛保证的多载波1比特预编码算法(CG-MC1bit),能够获得较优的系统性能,但相应的计算复杂度较高,阻碍了其在实时系统中的应用。为进一步解决大规模MIMO系统中的成本和功耗问题,该文提出了一个模型驱动的神经网络,在CG-MC1bit算法的基础上迭代展开(Unfolding)得到了一种更加高效的CG-MC1bit-Net算法。具体而言,将迭代算法展开为一个神经网络,并引入可训练的参数来替代前向传播中的高复杂性操作。实验结果表明,该方法能够自动更新参数,与传统的预编码算法相比,收敛速度更快,计算复杂度更低。
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关键词:
- 大规模多输入多输出 /
- 预编码 /
- 正交频分复用(OFDM) /
- 迭代展开 /
- 神经网络
Abstract: The base station of a massive Multiple-Input Multiple-Output (MIMO) system is equipped with hundreds of antennas, enhancing the spectral efficiency of the system and increasing the system costs. To address this problem, our research group proposed a Convergence-Guaranteed Multi-Carrier one-bit precoding (CG-MC1bit) iterative algorithm suitable for Orthogonal Frequency-Division Multiplexing (OFDM) downlink massive MIMO systems, which can ensure superior system performance. However, the corresponding computational complexity is high, hindering the practical application of the algorithm in real-time systems. To address this issue, we propose a model-driven, unfolding neural network, which is based on the CG-MC1bit iterative algorithm and introduces trainable parameters to replace high-complexity operations in forward propagation. In particular, we unfold the iterative algorithm into a neural network and introduce trainable parameters to replace high-complexity operations in forward propagation. Simulation results reveal that this method can automatically update parameters. In addition, compared with the traditional precoding algorithms, the proposed method has a higher convergence speed and lower computational complexity.-
Key words:
- Massive MIMO /
- Precoding /
- Orthogonal Frequency-Division Multiplexing(OFDM) /
- Unfolding /
- Neural Network
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1 CG-MC1bit-Net算法
已知:传输信号矩阵$ {{\boldsymbol{S}}} $,信道矩阵$ {{\boldsymbol{H}}} $,神经网络层数$ K $ 1) 初始化 $ {\boldsymbol{X}}^{\text{0}}={{\bf{1}}},\;{\boldsymbol{R}}^{\text{0}}\text{=}{{\bf{1}}},\;{\boldsymbol{V}}^{\text{0}}={{ {\textit{0}}}},\;\alpha =\text{0}\text{.1} $ 2) for 数据集中的每个样本 do 3) 初始化$k = {\text{0}}$ 4) while $k < K$ do 5) ${\tilde {\boldsymbol{H}}} = {\alpha ^k}{{\boldsymbol{H}}}$ 6) 初始化$l = {\text{0}}$ 7) for $l < L$ do 8) 根据式(4)更新$ {{{\boldsymbol{x}}}^{k + 1}}[l] $,$ l = l + {\text{1}} $ 9) end for 10) $ {{\boldsymbol{R}}}_{\text{T}}^{k + 1} = \eta \tanh \left[ {\delta \dfrac{1}{L}\left( {{{{\boldsymbol{X}}}^{k + 1}} + \dfrac{1}{\lambda }{{{\boldsymbol{V}}}^k}} \right){{\boldsymbol{F}}}_L^{\text{H}}} \right] $ 11) $ {{{\boldsymbol{R}}}^{k + 1}} = {{\boldsymbol{R}}}_{\text{T}}^{k + 1}{{{\boldsymbol{F}}}_L} $ 12) $ {{{\boldsymbol{V}}}^{k + 1}} = {{{\boldsymbol{V}}}^k} + \lambda \left( {{{\boldsymbol{X}}}_{\text{T}}^{k + 1} - {{{\boldsymbol{R}}}^{k + 1}}} \right) $ 13) $ k = k + {\text{1}} $ 14) end while 15) 输出$ {{\boldsymbol{R}}}_{\text{T}}^K $,并根据式(11)计算损失函数$ {\text{los}}{{\text{s}}_{{\text{MSE}}}} $ 16) 执行会话 17) for 隐藏层或输出层的每个神经元 do 18) 更新网络中的每一个权值和偏差 19) end for 20) end for 表 1 运行速度对比
预编码算法 天线数128 天线数512 CG-MC1bit-Net 0.429 s 2.127 s CG-MC1bitx 3.47 s 10.33 s -
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