Deep Learning for joint channel estimation and feedback in massive MIMO systems(1)

三省少年發表於2020-12-17

1.Introduction

In this paper, a comprehensive research is carried out to establish a joint channel estimation and feedback framework for the FDD massive MIMO systems based on DL techniques. The main contributions of this paper are summarized as follows.

  1. The DL based joint channel estimation and feedback framework of downlink channels in FDD massive MIMO systems is proposed in this paper, which is the first to the best of our knowledge. Two networks are constructed to perform explicit and implicit channel estimation and feedback, respectively. The channel estimation and feedback network (CEFnet) employs a lightweight CNN structure to explicitly obtain the refined estimate of channels and utilizes a denoising autoencoder structure (DAE) to compress and reconstruct the noisy channel matrices. The other pilot compression and feedback network (PFnet) compresses and sends back the pilot information directly to the BS without estimating the channels.
    第一次在FDD的模式下設計了基於DL的聯合通道估計和通道資訊反饋,之前的paper大多數只做feedback。提出了顯式和隱式的網路架構,使用了輕量級的CNN架構,使用了去噪模組。
  2. A multi-signal-to-noise-ratios (SNRs) training technique is proposed to cope with multiple SNR cases so that the construction of multiple individual models for each single SNR can be avoided, which significantly reduces the storage space and makes the trained network robust to channel noise. Moreover, quantization module is enrolled into the whole network to generate data-bearing bitstreams and observe the robustness of the two networks to the quantization distortion.
    使網路適應了不同訊雜比的情況(這還是很重要的),同時測試了量化噪聲的影響
  3. Performance analysis of the proposed two networks is provided. Both proposed networks demonstrate excellent reconstruction capacity while the CEFnet works a little better than PFnet but PFnet generates less parameters that needs storing than CEFnet. Moreover, the two networks are also proved to be robust to the quantization errors and noise.
    提供了效能分析

2.System model

2.1 Massive MIMO system

主要考慮FDD的下行鏈路,第 i i i根天線的下行鏈路
y i = X i h i ~ y_i=X_i\tilde{h_i} yi=Xihi~其中, X i ∈ C k ^ × k ^ X_i\in C^{\hat k\times \hat k} XiCk^×k^是一個對角陣, h i ~ ∈ C K ^ × 1 \tilde{h_i}\in C^{\hat K\times 1} hi~CK^×1是通道頻域響應,這麼建模的原因詳見關於Y=HX的一些思考,看懂這篇這樣寫公式就好理解了。
總的建模可以寫為
y = ∑ i = 1 N t X i h i ~ + n y=\sum_{i=1}^{N_t}X_i\tilde{h_i}+n y=i=1NtXihi~+n其中 H ~ = [ h 1 ~ , h 2 ~ , . . . , h N t ~ ] \tilde{H}=[\tilde{h_1},\tilde{h_2},...,\tilde{h_{N_t}}] H~=[h1~,h2~,...,hNt~]

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