Learning How to Transfer from Uplink to Downlink via Hyper-Recurrent Neural Network for FDD Massive MIMO

Yusha Liu, Osvaldo Simeone

Research output: Contribution to journalArticlepeer-review

Abstract

In order to unlock the full advantages of massive multiple-input multiple-output (MIMO) in the downlink, the base station (BS) must leverage information about the downlink fading channels. However, in frequency division duplex (FDD) systems, full channel reciprocity does not hold, and acquiring information about the downlink channels generally requires downlink pilot transmission followed by uplink feedback. Prior work proposed to design pilot transmission, feedback, and channel state information (CSI) estimation, or directly downlink beamforming, via deep learning in an end-to-end manner. While previous work only used downlink pilots in a single slot, in this work, we introduce an enhanced end-to-end design that leverages partial uplink-downlink reciprocity and temporal correlation of the fading processes by utilizing jointly downlink and uplink pilots across multiple time slots. The proposed method is based on a novel deep learning architecture – HyperRNN – that combines hypernetworks and recurrent neural networks (RNNs) to optimize the transfer of long-term invariant channel features from uplink to downlink. Simulation results demonstrate that the HyperRNN achieves a lower normalized mean square error (NMSE) performance in terms of channel estimation, and that it attains a larger achievable sum-rate when applied to multi-user beamforming, as compared to the state of the art.

Original languageEnglish (US)
JournalIEEE Transactions on Wireless Communications
DOIs
StateAccepted/In press - 2022
Externally publishedYes

ASJC Scopus subject areas

  • Computer Science Applications
  • Electrical and Electronic Engineering
  • Applied Mathematics

Keywords

  • Array signal processing
  • Channel estimation
  • Correlation
  • Downlink
  • FDD
  • Fading channels
  • Training
  • Uplink
  • deep learning
  • hypernetwork
  • massive MIMO

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