A Study on Next-Generation Wireless Systems: Analog-Filtered OFDMA and LEO Satellite Networks = 차세대 무선 시스템에 관한 연구: 아날로그 필터드 OFDMA 및 LEO 위성 네트워크

다국어 초록 (Multilingual Abstract)

Recent advances in stochastic geometry have provided powerful tools for analyzing large-scale low Earth orbit (LEO) satellite constellations by treating satellite positions as spatial point processes. Unlike earlier studies that mainly assumed a reference user fixed at the polar regions, this work accounts for arbitrary user locations, which is particularly relevant for modern constellations such as OneWeb where inclined orbital planes converge near the poles. We develop a location-aware analytical model that generalizes previous frameworks to handle polar-intersecting multi-orbit scenarios. Based on this model, we derive a closed-form characterization of the visible orbital arc length as a function of user latitude and use it to quantify the resulting coverage probability under an opportunistic access scheme. Our results indicate that users situated at higher latitudes benefit from longer visibility spans, thereby improving their chances of maintaining satellite connectivity. Furthermore, incorporating orbit diversity consistently enhances coverage performance across different geographic locations. These outcomes provide a tractable and flexible foundation for the design and optimization of next-generation LEO satellite networks and demonstrate the effectiveness of stochastic geometry as a modeling tool.

다국어 초록 (Multilingual Abstract)

One-bit analog-to-digital converters (ADCs) have emerged as an attractive low-power solution, and although they introduce non-linear distortion, their achievable capacity can remain close to that of high-resolution ADCs in narrowband channels under low to moderate signal-to-noise ratios (SNRs). However, applying such ADCs to discrete Fourier transform (DFT)-based orthogonal frequency-division multiple access (OFDMA) systems poses difficulties, as the coarse quantization severely degrades discrete-time processing, particularly at mid to high SNR levels. To overcome this challenge, we introduce a receiver design that combines one-bit ADCs with an analog low-pass filter (LPF), enabling improved compatibility with OFDMA while suppressing quantization-induced distortion. This design provides a practical and efficient framework for wideband multicarrier systems by supporting simplified symbol detection, determining the optimal LPF cutoff bandwidth, and identifying the best detection timing. Simulation results confirm that the proposed scheme significantly outperforms conventional digital-domain OFDMA when both employ one-bit ADCs, especially under the ideal LPF assumption. Moreover, even with a simple first-order LPF, the system attains performance on par with advanced deep learning-based receivers, despite requiring far less structural complexity.

목차 (Table of Contents)

• Part I An Analog-Filtered OFDMA Design for Receivers Utilizing One-Bit ADCs in Wideband Channels 1
• Abstract 1
• 1. Introduction 2
• 2. System Model 5
• (i) Channel model 5
• (ii) Baseline receiving structure: conventional commercial OFDMA in standards, which uses DFT for frequency-domain equalization (FDE) 8
• 3. Proposed Scheme: Analog-Filtered OFDMA 11
• (i) Overall process 11
• (ii) Calculation of zm(t) with the ideal LPF 14
• (iii) Calculation of zm(t) with the first-order LPF 14
• (iv) Optimal values for Td and wo 15
• (iv)-1 Case of first-order LPF 15
• (iv)-2 Case of ideal LPF 16
• (v) Channel estimation and equalization 18
• 4. Simulation Results 20
• 5. Conclusion 25
• Part II Generalized Coverage Modeling for Multi-Orbit Low Earth Orbit Satellite Networks 26
• Abstract 26
• 1. System Model 32
• (i) Network Model 32
• (ii) Channel Model 33
• (iii) Performance Metric 35
• 2. Coverage Probability Analysis 38
• (i) Derivation for the coverage probability 41
• 3. Simulation Results 44
• *Appendix 48
• A. Proof of Lemma 1 48
• References 50