| 摘要: | 在未來的全球無線通訊佈局中，低軌衛星（LEO）系統將扮演關鍵角色，特別是在傳統基地台覆蓋困難的地區，例如海洋、山區、沙漠與偏遠地區。隨著低軌衛星的大量部署每年超過千顆的發射數量，使得星座密度迅速提升，使得衛星資源管理與通訊效率成為亟需解決的重要課題。
根據 3GPP 的標準化進程，Release 18 已於近期正式凍結，並首次納入對非地面網路（NTN）之 MIMO 支持；接下來的 Release 19 亦預期將更進一步加強對多衛星協同與高頻段資源調度的研究與規範，特別是在功率效率、使用者排程與傳輸策略方面會有更深入的探討。
為了呼應此趨勢，本論文提出一種新穎的低軌衛星資源分配模型，旨在以最小化傳送功率為目標，採用多模式設計，將使用者選擇和子載波分配與衛星傳輸模式分配選擇結合，為篩選出的每個使用者分配最合適的子載波與傳輸方式。傳統 LEO 衛星系統大多採用單衛星傳輸策略，忽略多衛星協同所帶來的潛力。本研究引入「衛星作為可配置資源」的概念，讓衛星能根據通道品質與使用者需求，動態選擇由單衛星或雙衛星傳輸模式為使用者服務，並進行子載波配置，以提升系統效率並降低發射功率。最後，我們考慮較為實際的情況，我們引入了切換等級表，使用者可以在其中為不同的衛星選擇適當的調製和編碼方案（MCS）。我們推導出每個MCS相應的SNR閾值，以計算衛星所需的發射功率，確保用戶達到其期望的數據速率，同時保持10%的塊錯誤率（BLER）以確保一定水平的服務品質。
本研究首先透過使用者選擇策略（User Selection），自動篩選出通道條件較佳的使用者，確保系統維持在最佳運作狀態。為進一步提升系統效能，提出一套基於混合遺傳–粒子群（Hybrid GA–PSO）演算法的聯合優化機制，同步處理子載波配置與衛星傳輸模式選擇。該演算法結合遺傳演算法的全域搜尋能力與粒子群演算法的快速收斂特性，能在高維參數空間中維持群體多樣性，並兼顧探索與利用，有效降低運算複雜度與求解時間，在滿足 QoS 要求的前提下，實現最小總傳送功率以達成目標傳輸速率。模擬結果顯示，三階段整合方法（用戶選擇+衛星傳輸模式選擇+子載波分配）顯著降低了發射功率。
;In the future global wireless communication landscape, Low Earth Orbit (LEO) satellite systems are expected to play a pivotal role, especially in regions where traditional base station coverage is challenging—such as oceans, mountainous areas, deserts, and remote locations. With the massive deployment of LEO satellites—exceeding thousands of launches per year—the density of satellite constellations is rapidly increasing. This makes satellite resource management and communication efficiency pressing issues that need to be addressed.
According to the 3GPP standardization process, Release 18 has recently been officially frozen, and for the first time includes support for MIMO in Non-Terrestrial Networks (NTN). The upcoming Release 19 is also expected to further enhance research and standardization efforts related to multi-satellite coordination and high-frequency band resource scheduling, particularly focusing on power efficiency, user scheduling, and transmission strategies.
To respond to this trend, this paper proposes a novel resource allocation model for LEO satellites. The goal is to minimize transmission power through a multi-mode design that integrates user selection, subcarrier allocation, and satellite transmission mode assignment. Each selected user is allocated the most suitable subcarrier and transmission strategy. Traditional LEO satellite systems often adopt a single-satellite transmission approach, overlooking the potential of multi-satellite coordination. This study introduces the concept of “satellites as configurable resources,” allowing satellites to dynamically select between single-satellite or dual-satellite transmission modes for each user, based on channel quality and user demand, and to perform subcarrier allocation accordingly. This approach aims to improve system efficiency and reduce transmission power.
Furthermore, to reflect more practical scenarios, we introduce a Modulation and Coding Scheme (MCS) switching table. Users can select appropriate MCS levels for different satellites. We derive the corresponding SNR thresholds for each MCS in order to compute the required satellite transmission power, ensuring that users achieve their desired data rates while maintaining a 10% Block Error Rate (BLER), thereby guaranteeing a certain level of Quality of Service (QoS).
This study first employs a user selection strategy to automatically filter out users with better channel conditions, ensuring optimal system operation. To further enhance system performance, a hybrid Genetic Algorithm–Particle Swarm Optimization (GA–PSO) based joint optimization mechanism is proposed. This mechanism simultaneously handles subcarrier allocation and satellite transmission mode selection. By combining the global search capability of genetic algorithms with the fast convergence of particle swarm optimization, the proposed algorithm maintains population diversity in high-dimensional parameter spaces while balancing exploration and exploitation. This effectively reduces computational complexity and solution time. Under the premise of meeting QoS requirements, it minimizes total transmission power to achieve the target data rates. Simulation results show that the proposed three-stage integrated method (user selection + satellite transmission mode selection + subcarrier allocation) significantly reduces transmission power. |
