為了讓UE能夠同時使用LTE (Long Term Evolution)與5G NR (New Radio)的無線資源，3GPP (3rd Generation Partnership Project)提出了EN-DC (E-UTRAN New Radio - Dual Connectivity)的技術，但是當eNB發生壅塞時，如果沒有使用動態分流會導致eNB的PLR (Packet Loss Ratio)上升與UE的Throughput下降，為了解決這些問題，本論文在EN-DC網路下提出一個動態分流的機制(Dynamic Stream-Splitting Scheme, DSSS)，在此機制中，我們分別在eNB、 EPC與gNB新增負載計算演算法、動態分流演算與接收分流演算法。在負載計算演算法中，當UE向影音串流伺服器發送一個Data Rate要求時，eNB會攔截此要求並計算自己的負載百分比，當eNB的負載百分比大於一個閥值時，eNB會向EPC發送影音串流的分流要求。在動態分流演算法中，當EPC收到eNB所發送的分流要求時，動態分流演算法會產生一個分流訊息並廣播給所有的gNB，此時EPC會等待符合分流條件的gNB的回報，當EPC接收到gNB的回報時，EPC會將需分流的Data Rate發送到這些gNB。在接收分流演算法中，當gNB接收到EPC所發送的分流廣播訊息時，符合分流條件的gNB會向EPC回報gNB ID與負載百分比來做分流。最後我們使用OAI平台實作DSSS並使用NS-3來模擬DSSS的效能，從模擬結果中，我們證明本機制可以達到負載平衡，並且有效改善排隊延遲、封包遺失率與Throughput。

In order to enable UE to use both LTE (Long Term Evolution) and 5G NR (New Radio), 3GPP (3rd Generation Partnership Project) proposed EN-DC (E-UTRAN New Radio-Dual Connectivity). When congestion occurs in the eNB and dynamic splitting is not used, the PLR (Packet Loss Ratio) of the eNB will increase and the throughput of the UE will decrease. In order to solve these problems, in this thesis we present a DSSS (Dynamic Stream-Splitting Scheme) in the EN-DC networks. In this scheme, we add load computing algorithm, dynamic splitting algorithm, and split-receiving algorithm to eNB, EPC, and gNB, respectively. When the UE sends a data rate request to the streaming server, the eNB will intercept the request and compute its load ratio. When the eNB's load ratio exceeds a threshold, the eNB will send a splitting request to the EPC. In the dynamic splitting algorithm, when the EPC receives the splitting request sent by the eNB, the dynamic splitting algorithm will generate a splitting message and broadcast to all gNBs. The EPC will wait for the reply from the gNB that meets the splitting conditions. When receiving the gNB's reply, the EPC will send the data rate to split to these gNBs. In the split-receiving algorithm, when the gNB receives the splitting broadcast message sent by the EPC, the gNB that meets the splitting conditions will reply the gNB ID and the load ratio to the EPC. Finally, we use the OAI platform to implement DSSS and use NS-3 to simulate the performance of DSSS. From the simulation results, we prove that this scheme can achieve load balance and significantly improve queuing delay, PLR and throughput.

論文審定書 i
致謝 ii
摘要 iii
Abstract iv
目錄 v
圖目錄 vii
表目錄 ix
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　EN-DC的4G/5G網路 4
2.1 4G LTE vs 5G NR 4
2.1.1 SA vs NSA 6
2.1.2 EN-DC 8
2.2 LTE與NR的多工技術 9
2.2.1 LTE的OFDMA Frame架構 9
2.2.2 NR的OFDMA Frame架構 12
2.3 頻域上的RB分配 17
2.4 影音串流的動態分流 19
2.5 相關研究 21
2.6 本論文機制 23
第三章　EN-DC的動態分流機制 26
3.1 動態分流的系統架構 26
3.2 三種控制訊息 29
3.2.1 Split-Notification Message 29
3.2.2 Load Status Report Message 30
3.2.3 Split-Decision Message 30
3.3 eNB的負載計算演算法 31
3.4 EPC的動態分流演算法 35
3.5 gNB的接收分流演算法 38
第四章 實作與模擬 43
4.1 實驗環境與設備規格 43
4.1.1修改sub-6 GHz的程式 45
4.1.2 新增負載百分比的程式 47
4.2 NS-3模擬 48
4.2.1 NS-3的軟體架構 48
4.2.2 NS-3模擬拓樸與參數設定 50
4.2.3 模擬結果與討論 52
4.2.3.1 負載百分比的變化 53
4.2.3.2 改變Arrival Rate的效能 54
4.3 時間複雜度 57
第五章 結論與未來工作 58
5.1 結論 58
5.2 遭遇問題 59
5.3 未來工作 59
Reference 60
Acronyms 65
Index 66

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