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Sparse Array of Sub-surface Aided Anti-blockage mmWave Communication Systems

Weicong Chen, Xi Yang, Shi Jin, Pingping Xu

TL;DR

A sparse array of sub-surface (SAoS) architecture for RIS is proposed, which contains several rectangle shaped sub-surfaces termed as RIS tiles that can be sparsely deployed and verified the tightness of the approximated ergodic spectral efficiency and demonstrate the great system performance.

Abstract

Recently, reconfigurable intelligent surfaces (RISs) have drawn intensive attention to enhance the coverage of millimeter wave (mmWave) communication systems. However, existing works mainly consider the RIS as a whole uniform plane, which may be unrealistic to be installed on the facade of buildings when the RIS is extreme large. To address this problem, in this paper, we propose a sparse array of sub-surface (SAoS) architecture for RIS, which contains several rectangle shaped sub-surfaces termed as RIS tiles that can be sparsely deployed. An approximated ergodic spectral efficiency of the SAoS aided system is derived and the performance impact of the SAoS design is evaluated. Based on the approximated ergodic spectral efficiency, we obtain an optimal reflection coefficient design for each RIS tile. Analytical results show that the received signal-to-noise ratios can grow quadratically and linearly to the number of RIS elements under strong and weak LoS scenarios, respectively. Furthermore, we consider the visible region (VR) phenomenon in the SAoS aided mmWave system and find that the optimal distance between RIS tiles is supposed to yield a total SAoS VR nearly covering the whole blind coverage area. The numerical results verify the tightness of the approximated ergodic spectral efficiency and demonstrate the great system performance.

Sparse Array of Sub-surface Aided Anti-blockage mmWave Communication Systems

TL;DR

A sparse array of sub-surface (SAoS) architecture for RIS is proposed, which contains several rectangle shaped sub-surfaces termed as RIS tiles that can be sparsely deployed and verified the tightness of the approximated ergodic spectral efficiency and demonstrate the great system performance.

Abstract

Recently, reconfigurable intelligent surfaces (RISs) have drawn intensive attention to enhance the coverage of millimeter wave (mmWave) communication systems. However, existing works mainly consider the RIS as a whole uniform plane, which may be unrealistic to be installed on the facade of buildings when the RIS is extreme large. To address this problem, in this paper, we propose a sparse array of sub-surface (SAoS) architecture for RIS, which contains several rectangle shaped sub-surfaces termed as RIS tiles that can be sparsely deployed. An approximated ergodic spectral efficiency of the SAoS aided system is derived and the performance impact of the SAoS design is evaluated. Based on the approximated ergodic spectral efficiency, we obtain an optimal reflection coefficient design for each RIS tile. Analytical results show that the received signal-to-noise ratios can grow quadratically and linearly to the number of RIS elements under strong and weak LoS scenarios, respectively. Furthermore, we consider the visible region (VR) phenomenon in the SAoS aided mmWave system and find that the optimal distance between RIS tiles is supposed to yield a total SAoS VR nearly covering the whole blind coverage area. The numerical results verify the tightness of the approximated ergodic spectral efficiency and demonstrate the great system performance.

Paper Structure

This paper contains 12 sections, 1 theorem, 23 equations, 4 figures.

Table of Contents

  1. Introduction
  2. System model
  3. Channel Model
  4. Uplink Ergodic Spectral Efficiency
  5. Ergodic spectral efficiency analysis
  6. Approximation of Ergodic Spectral Efficiency
  7. Effects of the SAoS Design
  8. The reflection coefficient design
  9. The scale of the SAoS
  10. The deployment of the RIS tiles
  11. Numerical results
  12. Conclusion

Key Result

Proposition 1

The ergodic spectral efficiency of sparse array of the sub-surface aided anti-blockage mmWave communication system is approximated by where ${\sigma ^2}$ is the noise power, where $T=({{{K_{\rm{M}}} + 1}})^{-1}({{{K_{\rm{B}}} + 1}})^{-1}$, $T_1=T{K_{\rm{M}}}{K_{\rm{B}}}$, $V_{m,n}$ and ${\Omega _{n,c,m,s}}$ are given in eq:V_m,n and eq:Omega_k,k, respectively.

Figures (4)

  • Figure 1: Sparse array of sub-surface aided anti-blockage mmWave communication systems
  • Figure 2: Comparison of Monte Carlo results and ergodic spectral efficiency approximations when the reflection coefficients are optimally and randomly designed, respectively.
  • Figure 3: Received SNR versus the scale of SAoS.
  • Figure 4: Ergodic spectral efficiency versus horizontal distance of RIS tiles for different horizontal RIS tiles number.

Theorems & Definitions (1)

  • Proposition 1