https://ir.lib.ncu.edu.tw/handle/987654321/397 Search the Channel s https://ir.lib.ncu.edu.tw/simple-search https://ir.lib.ncu.edu.tw/handle/987654321/99377 title: 基於 Actor-Critic 及資訊幾何優化之多低軌衛星下鏈波 束切換設計及模擬;Design and Simulation of Multi-Agent LEO Satellite Downlink Beam-Switching Based on Actor-Critic and Information Geometric Optimization abstract: 6G 通訊技術是一個下世代的行動通訊技術，其提供比現今 5G 的速度、低延遲、高頻譜效率、高傳輸能力，由於低地球軌道 (LEO) 衛星運行在地球軌道上，可以避免如地面通訊般受到地形及地理位置的情況，此外，由於低軌衛星的運行速度非常快，通訊品質會受到都卜勒效應的影響，因此使用波束成形(Beamforming) 技術進行波束追蹤可以有效的應對。但隨著地面用戶數及波束數量的增加，地面下鏈多用戶間訊號干擾問題日漸嚴重，因此本篇論文針對低軌衛星和地面用戶間的通訊環境進行設計及建模，藉由分析單衛星及多衛星兩種不同狀況下的分佈機率，改善波束控制係數及策略。因此，吾人提出一種基於資訊幾何優化演算法 (IGO) 的 Actor-Critic 演算法，其方法是將 Actor 網路以 IGO 演算法替換，藉此以高斯分佈作為機率分布，予以優化，並且追求如何最大化總體傳輸速率 (Sum-Rate)。實驗數據結果顯示，吾人所提出的做法經過一定次數的迭代，兩種狀況均可以趨於穩定並且收斂。;6G communication technology, as a next-generation mobile communication technology, offers higher speeds, lower latency, greater spectral efficiency, and higher throughput compared to the current 5G. Low-Earth-Orbit (LEO) satellites, operating in Earth’s orbit, can overcome the limitations of terrestrial communications, such as constraints imposed by terrain and geographical locations. However, due to the extremely high operational velocity of LEO satellites, communication quality is significantly impacted by the Doppler effect. Beamforming, specifically beam tracking, is employed to effectively compensate for this challenge. Nevertheless, as the number of ground users and beams increases, downlink multi-user interference (MUI) becomes an increasingly severe problem. This thesis, therefore, designs and models the communication environment between LEO satellites and ground users. By analyzing probability distributions under both single-satellite and multi-satellite scenarios, we aim to improve beam control coefficients and strategies. <br> Fri, 06 Mar 2026 10:50:32 GMT https://ir.lib.ncu.edu.tw/handle/987654321/99375 title: 雙 RIS 輔助整合感測與通訊系統中具 CRB 約束的波束 成形與反射相位聯合設計;Joint Transmit Beamforming and RIS Phase Shift Design for Dual-RIS-Aided ISAC Systems Under CRB Constraints abstract: 傳統無線通訊網路主要聚焦於資訊傳輸，然而隨著自動駕駛、智慧交通等應 用興起，高精準度感測與高速率通訊的整合問題成為關鍵。隨著使用毫米波等高頻段的感測，雖然能夠提供更高精準度的感測能力，但其訊號也容易受到建築物、障礙物等等的遮蔽而發生嚴重衰減，導致出現覆蓋盲區與感測精度下降。可重構智慧表面 (Reconfigurable Intelligent Surface, RIS) 因為其低功耗與元件上可調控的反射相位，能有效建立視距 (Line of Sight, LoS) 路徑，因此利用 RIS 輔助整合感測與通訊 (Integrated Sensing and Communication, ISAC) 成為熱門的主題。在本研究中探討由一個多天線發射基地台 (TX)、一個多天線接收基地台 (RX)、兩個 RIS、多個單天線通訊用戶 (User)、多個單天線感測目標 (Target) 組成的雙 RIS 輔助 ISAC 的問題，其中發射基地台由兩個子陣列 (subarray) 組成，分別發射感測與通訊訊號，並透過兩個 RIS 分別對目標進行感測以及對用戶提供通訊。在考慮感測性能克萊姆-饒歐界 (Cramér-Rao bound, CRB) 限制、發射總功率限制、RIS 單 位模量 (Unit-modulus) 限制下，聯合設計發射波束成形 (Beamforming) 與 RIS 反射相位的最佳化問題，並將此最佳化問題拆解為兩個子問題，並利用連續凸逼近 (Successive Convex Approximation, SCA) 與交替優化 (Alternative Optimization, AO) 求解，透過優化發射波束成形與 RIS 的反射相位能有效降低通訊用戶間、感測與通訊雙方的干擾，實現最大化通訊用戶總速率。;Traditional wireless communication networks primarily focus on information transmission. However, with the rise of applications such as autonomous driving and intelligent transportation systems, the integration of high-precision sensing and high-rate communication has become a critical challenge. Although sensing at high-frequency bands, such as millimeter-wave (mmWave), provides superior resolution, signals are highly susceptible to severe attenuation caused by blockages from buildings and other obstacles, leading to coverage dead zones and degraded sensing accuracy. Reconfigurable Intelligent Surfaces (RIS), characterized by low power consumption and tunable reflection phases, can effectively establish line-of-sight (LoS) paths. Consequently, RIS assisted Integrated Sensing and Communication (ISAC) has emerged as a prominent research topic. This thesis investigates an dual-RIS assisted ISAC system comprising a multi-antenna transmitter (TX), a multi-antenna receiver (RX), two RIS, multiple single-antenna communication users, and multiple single-antenna sensing targets. The TX is equipped with two subarrays dedicated to transmitting sensing and communication signals, respectively. These signals are reflected by two RIS to perform target sensing and provide communication services to users independently. Under constraints including the Cramér-Rao Bound (CRB) for sensing performance, total transmit power limits, and unit-modulus constraints of the RIS elements, we formulate a joint optimization problem for transmit beamforming and RIS reflection phases. The formulated problem is decomposed into two sub-problems and solved using Successive Convex Approximation (SCA) and Alternative Optimization (AO) techniques. By optimizing the transmit beamforming and RIS reflection phases, the proposed scheme effectively mitigates interference among communication users as well as the mutual interference between sensing and communication functionalities, thereby maximizing the system′s sum-rate. <br> Fri, 06 Mar 2026 10:50:12 GMT https://ir.lib.ncu.edu.tw/handle/987654321/99373 title: 基於GPS與銣原子鐘Multi-site雷達時間同步機制：RFSoC 平台之設計與實現;Time Synchronization for Multi-Site Radar System Using GPS and Rubidium Atomic Clocks on RFSoC Platforms abstract: 異地多輸入多輸出（Multi-site MIMO）雷達可透過空間分集與多視角觀測提升偵測與定位潛力，但其系統能否發揮效益，關鍵取決於分散站點間是否能建立高精度且可長時間維持的時間與頻率同步。為解決 GPS 1PPS 具備絕對時間基準但存在短期抖動、以及各站點本地振盪器長時間累積漂移等問題，本論文提出並實作一套「GPS 1PPS + 銣原子鐘」的混合式同步架構，並以有限狀態機（FSM）導入容差式校準機制，使系統在多數時間維持本地穩定時脈域運行，僅在相位偏差超過門檻時進行校正，以兼顧短期穩定性與長期準確性。本系統以 Xilinx ZCU111 RFSoC 平台為核心，整合基頻即時處理與收發控制，並將 GPS 1PPS 經由邊緣化與同步化電路轉換為 FPGA 內部觸發事件，進一步生成對齊 PRI 的關鍵控制訊號以驅動發射閘控與接收擷取窗。在戶外 2T2R 多站點實證中，所提同步機制透過有限狀態機設定 28 ns 為漂移之容許門檻 (Maximum Drift Threshold)，確保系統在長時間運作下，站間時序偏移被嚴格限制在此邊界之內。此機制有效抑制了發散風險，並結合後端校正算法，成功支撐異地同調收發與後續資料融合流程，並完成對遠距離無人機目標之偵測與定位驗證。;Multi-site Multiple-Input Multiple-Output (MIMO) radar can significantly enhance detection and localization by exploiting spatial diversity and multi-aspect observations. However, practical deployment is fundamentally limited by the ability to achieve and sustain high-precision time and frequency synchronization across geographically separated stations. This thesis presents and implements a hybrid synchronization architecture that combines a GPS one-pulse-per-second (1PPS) signal as an absolute time reference with a rubidium atomic clock as a highly stable frequency reference. To balance GPS short-term jitter and long-term oscillator drift, an FSM-based, tolerance-driven calibration strategy is developed: the radar primarily operates in a locally stable clock domain and performs phase realignment only when the monitored offset exceeds a predefined threshold. The prototype is realized on a Xilinx ZCU111 RFSoC platform, integrating real-time baseband processing and transceiver control. The external 1PPS input is conditioned and converted into an internal trigger event, which is then used to generate PRI-aligned control signals for precise transmit gating and repeatable receive window capture. Outdoor 2T2R field experiments validate that the proposed scheme maintains inter-site synchronization within 28 ns, enabling coherent multisite operation and supporting subsequent data fusion. The system further demonstrates successful detection and localization of a long-range UAV target, confirming the feasibility of the proposed synchronization-enabled distributed sensing framework. <br> Fri, 06 Mar 2026 10:49:53 GMT https://ir.lib.ncu.edu.tw/handle/987654321/99371 title: 以RFSoC平台設計與實現應用同步通道建構多站點同步雷達系統;Design and Implementation of a Synchronized Multi-Site Radar System Using Synchronous Channel on an RFSoC Platform abstract: 本論文聚焦於RFSoC 平台以同步通道實現的 Multi-site Radar System，結合軟體定義無線電架構，建構一套可重構之多站雷達發射與接收系統。系統中以 Pseudo-Random Noise (PN) Sequence 為脈衝雷達測距碼元，藉由可程式化的目標模擬器在FPGA平台上產生可控制之延遲、振幅與 Doppler 頻移，模擬不同距離之目標情境。透過RF Cable應用Sync Channel配合 Frequency and Time Synchronizer模組，可在兩台ZCU111之間建立時間基準與載波頻率同步，使各站接收端能以奈秒等級的時間精度進行量測，驗證多站協同偵測與分散式處理之可行性。 在數位訊號處理設計上，本系統於 RFSoC內部整合Radar Signal Generator、Matched Filter、Peak Detector等關鍵模組，利用高效能DSP Slice與板上RAM實現即時PN匹配濾波與回波峰值偵測，並透過多站量測的時間差與頻率偏移資訊，支援目標定位。以實驗結果顯示，透過RF Cable同步而非GPS/原子鐘的方式，仍能在實驗室環境中達到穩定的跨站時頻一致性，證明RFSoC平台與軟體定義無線電技術適合作為多站雷達的模擬驗證工具。 ;This paper focuses on a multi-site radar system implemented on an RFSoC platform using a synchronized channel architecture. By integrating a software-defined radio (SDR) framework, a reconfigurable multi-station radar transmitter and receiver system is realized on FPGA hardware. In the proposed system, a pseudo-random noise (PN) sequence is employed as the pulse radar ranging waveform. A programmable target emulator implemented on the FPGA fabric is used to generate controllable propagation delay, amplitude scaling, and Doppler frequency shift, enabling the emulation of target scenarios at different ranges. Through RF cable interconnection combined use Synchronous Channel with a frequency and time synchronizer module, a common time reference and carrier frequency synchronization are established between two ZCU111 RFSoC boards. This hardware-based synchronization approach allows each receiver to perform measurements with nanosecond-level timing accuracy, thereby validating the feasibility of cooperative multi-site sensing and distributed signal processing. From a digital signal processing and hardware design perspective, the RFSoC integrates key radar processing modules, including a radar signal generator, matched filter, and peak detector. High-performance DSP slices and on-chip memory resources are utilized to implement real-time PN matched filtering and echo peak detection. By exploiting time-of-arrival differences and frequency offset information obtained from multi-site measurements, the proposed system supports target localization. Experimental results demonstrate that RF cable–based synchronization, without relying on GPS or atomic clock references, can achieve stable inter-site time and frequency coherence in a laboratory environment, validating the RFSoC platform and SDR-based hardware architecture as an effective emulation and verification tool for multi-site radar systems. <br> Fri, 06 Mar 2026 10:49:43 GMT