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Near-Field Wideband Extremely Large-scale MIMO Transmission with Holographic Metasurface Antennas

Jie Xu, Li You, George C. Alexandropoulos, Xinping Yi, Wenjin Wang, Xiqi Gao

Abstract

Extremely large-scale multiple-input multiple-output (XL-MIMO) is the development trend of future wireless communications. However, the extremely large-scale antenna array could bring inevitable nearfield and dual-wideband effects that seriously reduce the transmission performance. This paper proposes an algorithmic framework to design the beam combining for the near-field wideband XL-MIMO uplink transmissions assisted by holographic metasurface antennas (HMAs). Firstly, we introduce a spherical-wave-based channel model that simultaneously takes into account both the near-field and dual-wideband effects. Based on such a model, we then formulate the HMA-based beam combining problem for the proposed XL-MIMO communications, which is challenging due to the nonlinear coupling of high dimensional HMA weights and baseband combiners. We further present a sum-mean-square-error-minimization-based algorithmic framework. Numerical results showcase that the proposed scheme can effectively alleviate the sum-rate loss caused by the near-field and dual-wideband effects in HMA-assisted XL-MIMO systems. Meanwhile, the proposed HMA-based scheme can achieve a higher sum rate than the conventional phase-shifter-based hybrid analog/digital one with the same array aperture.

Near-Field Wideband Extremely Large-scale MIMO Transmission with Holographic Metasurface Antennas

Abstract

Extremely large-scale multiple-input multiple-output (XL-MIMO) is the development trend of future wireless communications. However, the extremely large-scale antenna array could bring inevitable nearfield and dual-wideband effects that seriously reduce the transmission performance. This paper proposes an algorithmic framework to design the beam combining for the near-field wideband XL-MIMO uplink transmissions assisted by holographic metasurface antennas (HMAs). Firstly, we introduce a spherical-wave-based channel model that simultaneously takes into account both the near-field and dual-wideband effects. Based on such a model, we then formulate the HMA-based beam combining problem for the proposed XL-MIMO communications, which is challenging due to the nonlinear coupling of high dimensional HMA weights and baseband combiners. We further present a sum-mean-square-error-minimization-based algorithmic framework. Numerical results showcase that the proposed scheme can effectively alleviate the sum-rate loss caused by the near-field and dual-wideband effects in HMA-assisted XL-MIMO systems. Meanwhile, the proposed HMA-based scheme can achieve a higher sum rate than the conventional phase-shifter-based hybrid analog/digital one with the same array aperture.
Paper Structure (23 sections, 1 theorem, 43 equations, 9 figures, 2 algorithms)

This paper contains 23 sections, 1 theorem, 43 equations, 9 figures, 2 algorithms.

Table of Contents

  1. Introduction
  2. System Model
  3. Holographic Metasurface Antennas
  4. Spherical-Wave-based Channel Model
  5. Problem Formulation
  6. Proposed Algorithm for HMA-Assisted Beam Combining
  7. Equivalent Matrix-Weighted MMSE
  8. Matrix Vectorization
  9. Optimization of HMA Weights
  10. Unconstrained Weight Case
  11. Amplitude-Only Weight Case
  12. Binary Amplitude Weight Case
  13. Lorentzian-Constrained Phase Case
  14. Convergence and Complexity Analysis
  15. Simulation Results
  16. ...and 8 more sections

Key Result

Lemma 1

Define $\mathbf{T}$ as a $N_\text{R} \times N_\text{R}$ Hermitian matrix such that $\mathbf{T} \succeq \mathbf{S}$. For any given $\mathbf{p}^{(\ell)}$ at the $(\ell-1)$th iteration, we have

Figures (9)

  • Figure 1: The considered HMAs-assisted XL-MIMO uplink system.
  • Figure 2: Convergence performance of Algorithm \ref{['alg:overallalg']} with different power budgets: (a) amplitude-only weights; (b) Lorentzian-constrained phases.
  • Figure 3: The comparison between the sum-rate performance of the proposed algorithms and baselines for HMA-assisted XL-MIMO communications versus the transmission bandwidth.
  • Figure 4: The comparison between the sum-rate performance of the proposed algorithms and baselines for HMA-assisted XL-MIMO communications versus the array length.
  • Figure 5: The comparison of the sum-rate performance between the proposed algorithms derived under spherical and plane wavefront assumptions versus the transceiver distance.
  • ...and 4 more figures

Theorems & Definitions (1)

  • Lemma 1