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Impact of Pointing Error on Coverage Performance of 3D Indoor Terahertz Communication Systems

Zhifeng Tang, Nan Yang, Xiangyun Zhou, Salman Durrani, Markku Juntti, Josep Miquel Jornet

TL;DR

This work addresses the sensitivity of 3D indoor THz coverage to pointing errors caused by location estimation inaccuracy. It develops a tractable stochastic-geometry framework combining PPP AP placements, random human blockages, Boolean wall blockages, and MFTR fading, with a Gaussian-like pointing-error model to derive a comprehensive coverage probability expression. The results show that pointing errors significantly degrade coverage and that merely increasing antenna array size cannot fully compensate for misalignment, highlighting the need for accurate angle estimation and location techniques. The findings guide design principles for robust indoor THz networks by underscoring estimation accuracy as a critical performance enabler.

Abstract

In this paper, we develop a tractable analytical framework for a three-dimensional (3D) indoor terahertz (THz) communication system to theoretically assess the impact of the pointing error on its coverage performance. Specifically, we model the locations of access points (APs) using a Poisson point process, human blockages as random cylinder processes, and wall blockages through a Boolean straight line process. A pointing error refers to beamforming gain and direction mismatch between the transmitter and receiver. We characterize it based on the inaccuracy of location estimate. We then analyze the impact of this pointing error on the received signal power and derive a tractable expression for the coverage probability, incorporating the multi-cluster fluctuating two-ray distribution to accurately model small-scale fading in THz communications. Aided by simulation results, we corroborate our analysis and demonstrate that the pointing error has a pronounced impact on the coverage probability. Specifically, we find that merely increasing the antenna array size is insufficient to improve the coverage probability and mitigate the detrimental impact of the pointing error, highlighting the necessity of advanced estimation techniques in THz communication systems.

Impact of Pointing Error on Coverage Performance of 3D Indoor Terahertz Communication Systems

TL;DR

This work addresses the sensitivity of 3D indoor THz coverage to pointing errors caused by location estimation inaccuracy. It develops a tractable stochastic-geometry framework combining PPP AP placements, random human blockages, Boolean wall blockages, and MFTR fading, with a Gaussian-like pointing-error model to derive a comprehensive coverage probability expression. The results show that pointing errors significantly degrade coverage and that merely increasing antenna array size cannot fully compensate for misalignment, highlighting the need for accurate angle estimation and location techniques. The findings guide design principles for robust indoor THz networks by underscoring estimation accuracy as a critical performance enabler.

Abstract

In this paper, we develop a tractable analytical framework for a three-dimensional (3D) indoor terahertz (THz) communication system to theoretically assess the impact of the pointing error on its coverage performance. Specifically, we model the locations of access points (APs) using a Poisson point process, human blockages as random cylinder processes, and wall blockages through a Boolean straight line process. A pointing error refers to beamforming gain and direction mismatch between the transmitter and receiver. We characterize it based on the inaccuracy of location estimate. We then analyze the impact of this pointing error on the received signal power and derive a tractable expression for the coverage probability, incorporating the multi-cluster fluctuating two-ray distribution to accurately model small-scale fading in THz communications. Aided by simulation results, we corroborate our analysis and demonstrate that the pointing error has a pronounced impact on the coverage probability. Specifically, we find that merely increasing the antenna array size is insufficient to improve the coverage probability and mitigate the detrimental impact of the pointing error, highlighting the necessity of advanced estimation techniques in THz communication systems.
Paper Structure (13 sections, 3 theorems, 21 equations, 4 figures, 1 table)

This paper contains 13 sections, 3 theorems, 21 equations, 4 figures, 1 table.

Table of Contents

  1. Introduction
  2. System and Channel Model
  3. System Deployment
  4. Antenna Model
  5. THz Channel Model
  6. Coverage Probability Analysis
  7. Pointing Error Analysis
  8. AP Association and Interference Analysis
  9. Transmit Antenna Gain
  10. Receive Antenna Gain
  11. Coverage Performance Analysis
  12. Numerical Results
  13. Conclusion

Key Result

Lemma 1

The PDF of pointing error loss, $f_{H_{pe}}(h_{pe})$, is approximated as where $\beta = \frac{1.06^2}{2\varsigma_{\theta}^2(N_A^2+N_U^2)}$.

Figures (4)

  • Figure 1: Top and vertical views of the pointing error for an AP-UE link.
  • Figure 2: The PDF of the pointing error loss $f_{H_{pe}}(h_{pe})$.
  • Figure 3: The coverage probability, $P_c$, versus the $\mathrm{SINR}$ threshold, $\gamma_{\mathrm{th}}$ dB.
  • Figure 4: The coverage probability, $P_c$, versus the antenna array size of AP, $N_A$, with the $\mathrm{SINR}$ threshold $\gamma_{\mathrm{th}}=30$ dB.

Theorems & Definitions (3)

  • Lemma 1
  • Lemma 2
  • Theorem 1