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Electromagnetic Hybrid Beamforming for Holographic Communications

Ran Ji, Chongwen Huang, Xiaoming Chen, Wei E. I. Sha, Linglong Dai, Jiguang He, Zhaoyang Zhang, Chau Yuen, Mérouane Debbah

Abstract

It is well known that there is inherent radiation pattern distortion for the commercial base station antenna array, which usually needs three antenna sectors to cover the whole space. To eliminate pattern distortion and further enhance beamforming performance, we propose an electromagnetic hybrid beamforming (EHB) scheme based on a three-dimensional (3D) superdirective holographic antenna array. Specifically, EHB consists of antenna excitation current vectors (analog beamforming) and digital precoding matrices, where the implementation of analog beamforming involves the real-time adjustment of the radiation pattern to adapt it to the dynamic wireless environment. Meanwhile, the digital beamforming is optimized based on the channel characteristics of analog beamforming to further improve the achievable rate of communication systems. An electromagnetic channel model incorporating array radiation patterns and the mutual coupling effect is also developed to evaluate the benefits of our proposed scheme. Simulation results demonstrate that our proposed EHB scheme with a 3D holographic array achieves a relatively flat superdirective beamforming gain and allows for programmable focusing directions throughout the entire spatial domain. Furthermore, they also verify that the proposed scheme achieves a sum rate gain of over 150% compared to traditional beamforming algorithms.

Electromagnetic Hybrid Beamforming for Holographic Communications

Abstract

It is well known that there is inherent radiation pattern distortion for the commercial base station antenna array, which usually needs three antenna sectors to cover the whole space. To eliminate pattern distortion and further enhance beamforming performance, we propose an electromagnetic hybrid beamforming (EHB) scheme based on a three-dimensional (3D) superdirective holographic antenna array. Specifically, EHB consists of antenna excitation current vectors (analog beamforming) and digital precoding matrices, where the implementation of analog beamforming involves the real-time adjustment of the radiation pattern to adapt it to the dynamic wireless environment. Meanwhile, the digital beamforming is optimized based on the channel characteristics of analog beamforming to further improve the achievable rate of communication systems. An electromagnetic channel model incorporating array radiation patterns and the mutual coupling effect is also developed to evaluate the benefits of our proposed scheme. Simulation results demonstrate that our proposed EHB scheme with a 3D holographic array achieves a relatively flat superdirective beamforming gain and allows for programmable focusing directions throughout the entire spatial domain. Furthermore, they also verify that the proposed scheme achieves a sum rate gain of over 150% compared to traditional beamforming algorithms.
Paper Structure (18 sections, 1 theorem, 53 equations, 10 figures, 1 table, 1 algorithm)

This paper contains 18 sections, 1 theorem, 53 equations, 10 figures, 1 table, 1 algorithm.

Table of Contents

  1. Introduction
  2. Prior Works
  3. Our Contributions
  4. Organization and Notation
  5. Electromagnetic System Model
  6. Electromagnetic Transmission Signal Model
  7. Radiation Pattern Model
  8. Electromagnetic Channel Model
  9. Holographic Antenna Array Radiation Efficiency
  10. Proposed EHB Scheme
  11. 3D Holographic Antenna Array Structure
  12. Proposed EHB Algorithm
  13. Single-User Case
  14. Multi-User Scheme
  15. Complexity Analysis
  16. ...and 3 more sections

Key Result

Theorem 1

The obtained auxiliary digital precoding matrix $\boldsymbol{F}_k$ and auxiliary analog precoding matrix $\boldsymbol{G}$ in $P5$ and $P6$ satisfy rank($\boldsymbol{F}_k$) $=1$, rank($\boldsymbol{G}$) $=1$.

Figures (10)

  • Figure 1: Electromagnetic Hybrid Beamforming Architecture.
  • Figure 2: Radiation pattern for (a) An isolated antenna; (b) One antenna in holographic antenna array with 0.2$\lambda$ spacing; (c) Spatial beam based on mutual coupling; (d) Spatial beam without considering mutual coupling.
  • Figure 3: Multiple superdirective beams of 3D holographic antenna array.
  • Figure 4: Achievable directivity and realized gain for EHB system.
  • Figure 5: Achievable rate for EHB system with SNR = $20$ dB.
  • ...and 5 more figures

Theorems & Definitions (2)

  • Theorem 1
  • proof