在5G 無線通訊網路中，傳統的換手機制會根據UE回報的RSRP (Reference Signal Receiving Power)作為換手的依據，當gNB處於負載較高的狀態時，此機制無法將uRLLC (Ultra-reliable and Low Latency Communications)應用的UE換手到適合的基地台來滿足UE的要求，為了要解決這個問題，本論文提出了一個新的uRLLC換手機制，UE會週期性的將BLER與RTT回報給gNB，gNB會根據UE回報的BLER與RTT計算出gNB的品質指標(gNB Quality Index, GQI)，當UE判斷所連接的gNB無法滿足uRLLC應用的需求時，UE會計算出UE的品質指標(UE Quality Index, UQI)並傳送給5GC，5GC根據UE回報的UQI與gNB回報的GQI並透過uRLLC換手演算法找出最適合的gNB，首先我們使用OAI平台實作所提出的uRLLC換手機制，接著我們使用NS-3來模擬此機制，從模擬的結果證明使用我們的機制比使用原本的換手機制更能有效的降低UE的BLER、RTT與封包遺失率。

In 5G wireless communication network, the traditional Handover mechanism use RSRP (Reference Signal Receiving Power) reported by UE as a trigger. However, this mechanism cannot satisfy the uRLLC (Ultra-reliable and Low Latency Communications) requirements when the Serving gNB is in high loading. In order to solve this problem, this thesis propose an uRLLC handover mechanism, In this mechanism, UE will periodically report BLER and RTT to gNB, and the gNB will calculate the GQI (gNB Quality Index) based on the value reported by the UE. When the UE found that the Serving gNB can no longer satisfy the requirements of the uRLLC, UE will calculate the UQI (UE Quality Index) and send it to 5GC. When 5GC receive UQI, it will trigger the uRLLC handover Algorithm and find the best target gNB for UE to handover based on UQI and GQI. We first use OAI platform to implement our uRLLC Handover Mechanism. Then, we use NS-3 to simulate our mechanism. The simulation results prove that our mechanism is more effective to reduce the UE's BLER, RTT, and packet loss rate when comparing with the traditional Handover Mechanism.

論文審定書 i
致謝 ii
摘要 iii
Abstract iv
目錄 v
圖目錄 vi
表目錄 viii
第一章 導論 1
1.1 研究動機 1
1.2 研究方法 2
1.3 章節介紹 3
第二章 5G行動通訊網路與uRLLC 4
2.1 5G行動通訊網路 4
2.1.1 NSA and SA 4
2.1.2 Open-RAN 6
2.1.3 5GC 7
2.2 uRLLC的特性與應用 8
2.2.1 uRLLC的應用 8
2.2.2 uRLLC的特性 9
2.2.2.1 低延遲 9
2.2.2.2 高可靠度 10
2.3 使用RTCP計算RTT 11
2.4 BLER的計算 14
2.5 文獻探討 16
第三章 uRLLC的基地台換手機制 20
3.1基地台換手的系統架構 20
3.2 RTT計算模組 23
3.3 換手要求模組 26
3.4 QI計算模組 27
3.4.1 GQI計算模組 27
3.4.2 UE的QI計算模組 29
3.5 UCM Header的欄位設計 30
3.6 uRLLC換手模組 33
第四章 實作與模擬結果 40
4.1 實驗環境與設備規格 40
4.2 UHA的模擬 42
4.2.1 三種不同應用的拓樸 56
4.2.1.1 三種不同應用的拓樸的參數 57
4.2.1.2 三種不同應用的拓樸的結果 58
4.2.2 三種不同重疊區的拓樸 61
4.2.2.1 三種不同重疊區的拓樸的參數 62
4.2.2.2 三種不同重疊區的拓樸的結果 62
4.3 傳送UCM的Overhead 67
第五章 結論與未來工作 71
5.1 結論 71
5.2 遭遇的困難 72
5.3 未來工作 72
Reference 74
Acronyms 78
Index 80

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