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Coverage Performance Analysis of FAS-enhanced LoRa Wide Area Networks under both Co-SF and Inter-SF Interference

Gaoze Mu, Yanzhao Hou, Mingjie Chen, Yuanyu Hu, Yongan Zheng, Qimei Cui, Xiaofeng Tao

TL;DR

This work addresses the challenge of assessing coverage in LoRaWAN when equipped with a Fluid Antenna System (FAS) under both co-SF and inter-SF interference in dense deployments. It develops an analytical framework that combines stochastic geometry for user placement, Jake-based FAS fading with a block-correlation model, and extreme-value theory to approximate the FAS channel envelope, ultimately yielding tractable expressions for the coverage probability. Key advancements include Gamma-channel approximations, LT-based interference analysis, and validated accuracy against Monte Carlo simulations, demonstrating that even a small $1\times1$ FAS aperture can substantially enhance coverage and admissible ED counts, especially at higher SFs. The results offer practical guidance for deploying FAS in LoRaWAN to extend coverage and improve robustness against interference with minimal hardware complexity.

Abstract

This paper presents an analytical framework for evaluating the coverage performance of the fluid antenna system (FAS)-enhanced LoRa wide-area networks (LoRaWANs). We investigate the effects of large-scale pathloss in LoRaWAN, small-scale fading characterized by FAS, and dense interference (i.e., collision in an ALOHA-based mechanism) arising from randomly deployed end devices (EDs). Both co-spreading factor (co-SF) interference (with the same SF) and inter-SF interference (with different SFs) are introduced into the network, and their differences in physical characteristics are also considered in the analysis. Additionally, simple yet accurate statistical approximations of the FAS channel envelope and power are derived using the extreme-value theorem. Based on the approximated channel expression, the theoretical coverage probability of the proposed FAS-enhanced LoRaWAN is derived. Numerical results validate our analytical approximations by exhibiting close agreement with the exact correlation model. Notably, it is revealed that a FAS with a normalized aperture of 1 times 1 can greatly enhance network performance, in terms of both ED numbers and coverage range.

Coverage Performance Analysis of FAS-enhanced LoRa Wide Area Networks under both Co-SF and Inter-SF Interference

TL;DR

This work addresses the challenge of assessing coverage in LoRaWAN when equipped with a Fluid Antenna System (FAS) under both co-SF and inter-SF interference in dense deployments. It develops an analytical framework that combines stochastic geometry for user placement, Jake-based FAS fading with a block-correlation model, and extreme-value theory to approximate the FAS channel envelope, ultimately yielding tractable expressions for the coverage probability. Key advancements include Gamma-channel approximations, LT-based interference analysis, and validated accuracy against Monte Carlo simulations, demonstrating that even a small FAS aperture can substantially enhance coverage and admissible ED counts, especially at higher SFs. The results offer practical guidance for deploying FAS in LoRaWAN to extend coverage and improve robustness against interference with minimal hardware complexity.

Abstract

This paper presents an analytical framework for evaluating the coverage performance of the fluid antenna system (FAS)-enhanced LoRa wide-area networks (LoRaWANs). We investigate the effects of large-scale pathloss in LoRaWAN, small-scale fading characterized by FAS, and dense interference (i.e., collision in an ALOHA-based mechanism) arising from randomly deployed end devices (EDs). Both co-spreading factor (co-SF) interference (with the same SF) and inter-SF interference (with different SFs) are introduced into the network, and their differences in physical characteristics are also considered in the analysis. Additionally, simple yet accurate statistical approximations of the FAS channel envelope and power are derived using the extreme-value theorem. Based on the approximated channel expression, the theoretical coverage probability of the proposed FAS-enhanced LoRaWAN is derived. Numerical results validate our analytical approximations by exhibiting close agreement with the exact correlation model. Notably, it is revealed that a FAS with a normalized aperture of 1 times 1 can greatly enhance network performance, in terms of both ED numbers and coverage range.
Paper Structure (10 sections, 28 equations, 3 figures, 1 table)

This paper contains 10 sections, 28 equations, 3 figures, 1 table.

Table of Contents

  1. Introduction
  2. Network Model
  3. LoRaWAN Model
  4. Channel Model
  5. Coverage Probability
  6. Performance Analysis
  7. Channel Approximation
  8. Performance Analysis
  9. Numerical Results
  10. Conclusion

Figures (3)

  • Figure 1: LoRa receiver decision value. (a) Separated desired signal and interference, where the desired signal is characterized by $\{\text{encoded symbol},SF\}=\{25,8\}$, co-SF interference 1 by $\{125,8\}$, co-SF interference 2 by $\{165,8\}$, inter-SF interference 2 by $\{125,7\}$), inter-SF interference 2 by $\{165,9\}$). (b) Combined signal and interference.
  • Figure 2: Approximations of envelope and power for the FAS channel.
  • Figure 3: Coverage probability of the FAS-enhanced LoRa network under (a) varying numbers of EDs ($SF=9$, $R_2=3000~\mathrm{m}$), and (b) varying network region radius ($W_1\times W_2=1\times1$, $P_\mathrm{t}=10~\mathrm{dBm}$).