本論文在LTE Small Cell中提出一個動態調整Handover臨界值(Dynamic Adjustment in Handover Thresholds, DAHT)的換手機制來卸除某些負載過重的eNB，DAHT換手機制除了考慮User Equipment (UE)是處於靜止或移動狀態，也能夠利用Evolved Node B (eNB)的負載來計算出換手因素(Handover Factor, HF)，Source eNB藉由HF來減小或增大Source eNB與Target eNB的Reference Signal Receiving Power (RSRP)之間的差值(Offset)，因此Source eNB能夠將UE提前或延遲換手到Target eNB。為了實作完成DAHT換手機制，我們在eNB上設計負載量測模組來定期量測與回報eNB的負載，並在eNB上設計UE換手模組來進行UE的提前或延遲換手，另外我們也在Evolved Packet Core (EPC)的Self-Organizing Network (SON)上設計負載狀態分類模組來將每台eNB的負載做高中低的分類，並在SON上設計負載卸除模組來計算eNB所需要卸除負載的大小。為了驗證我們所提出DAHT換手機制的優越性，我們使用工研院(Industrial Technology Research Institute, ITRI)提供的Small Cell平台與EPC軟體來實作完成上述四個模組，在實作完成後，我們量測eNB的負載狀態與UE的居留時間以證明本論文所提出的DAHT換手機制可以達到提前與延遲換手。

This thesis presents a Dynamic Adjustment in Handover Thresholds (DAHT) for off-loading in LTE small cells. The proposed DAHT can distinguish whether an User Equipment (UE) is in static or mobile status. Additionally, DAHT can off-load Evolved Node B (eNB) by calculating a Handover Factor (HF). Based on the HF, source eNB can decrease or increase the offset of Reference Signal Receiving Power (RSRP) between source eNB and target eNB. Therefore, source eNB can advance or delay handover of UE to target eNB. In order to implement the proposed DAHT, we design the load measurement module on eNB to periodically measure and report the load of eNB, and design UE handover module on eNB to advance or delay UE’s handover. Moreover, we design load status module on Self-Organizing Network (SON) of Evolved Packet Core (EPC) to classify the load status of an eNB (i.e., heavy, medium, and low). Finally, we design offloading module on SON to calculate the off-loading amount. To validate the superiority of the proposed DAHT, we implement the aforementioned modules on ITRI’s (Industrial Technology Research Institute) small cell platform. During the experiment, we measure the load status of eNB and the residence time of UE to prove that the proposed DAHT can achieve advance or delay handover.

致謝 i
摘要 ii
Abstract iii
目錄 iv
圖表目錄 vi
第一章　導論 1
1.1 研究動機 1
1.2 研究方法 1
1.3 章節介紹 3
第二章　LTE Small Cell的負載卸除機制 4
2.1 LTE Small Cell架構 4
2.1.1 SON 5
2.1.2 實體資源單位 (Physical Resource Block, PRB) 6
2.1.3 LTE的換手 7
2.2 ITRI-Small Cell 8
2.3 相關研究 9
2.3.1 負載平衡機制 9
2.3.2 負載卸除機制 10
2.4 本論文機制 12
第三章　動態調整Handover的臨界值 14
3.1 DAHT系統架構 14
3.2 負載量測模組 16
3.3 負載狀態分類模組 18
3.4 負載卸除模組 20
3.5 UE換手模組 25
3.6 使用UDP傳送LM與ORM 31
第四章　ITRI平台的實作與結果分析 32
4.1 實作拓樸與設備規格 32
4.2 在ITRI平台上的實作 34
4.2.1 在eNB上的模組 34
4.2.2 在SON上的模組 43
4.3 實作與結果分析 47
4.3.1 Static UE的實作與結果分析 50
4.3.2 Mobile UE的實作與結果分析 55
第五章　結論與未來工作 61
5.1 結論 61
5.2 實作中所遭遇的困難與解決方法 62
5.3 未來工作 63
Reference 64
Acronyms 69
Index 71

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