隨著科技發展日新月異，人們對於網際網路的存取方式早已不同於以往，傳統的家用電腦及膝上型電腦受限於場地及體積限制，逐漸的無法滿足人們接收新資的速度，然而拜硬體設備及通訊產業的革新所賜，各式各樣的行動裝置快速普及，使得網頁瀏覽、電子郵件收發、多媒體串流，及社群通訊交流等服務不再受限於時地，而因為龐大網路通訊需求，所衍生的可觀能源消耗及基地台負載問題，便成為現今高速網路傳輸設計的一大課題。
在Macrocell以及Picocell共存的異質性網路中，由於前者有著較高的發射功率，因此使用者在進行基地台選擇時，往往容易選擇高功率的Macrocell，而非距離使用者較近的Picocell因此3GPP提出了Cell Range Expansion (CRE)此項技術，利用了一個固定偏移值 (Bias)，令使用者進行基地台選擇時，得以連接到Picocell，藉以紓緩Macrocell流量並增進上行服務品質，但由於使用者傳輸需求及分佈情形，狀況通常會因為時間以及地點而有相當不同的變化，因此固定的Bias值勢必無法因應現實環境的需求，便衍生出討論動態CRE調整的相關文獻。
而在3GPP TR36.872中同樣定義了small cell switch on/off的技術，使環境中的small cell得以在負載量小於一定門檻值時進入睡眠模式，藉以達到降低環境干擾以及省電的目的。然而，在實作了動態CRE以及基地台睡眠的情境中，當某基地台的負載量較小時，會直覺的調大其Bias值，使基地台得以服務較多使用者，然而此舉卻將導致基地台無法進入睡眠，因此如何對負載與省電之tradeoff進行理想設計，便成了本篇論文所要研究的目標。

With the impressive growth rate of rich multimedia and network applications, there is an exponential increasing demand for the mobile broadband in the new technological era. The Third Generation Partnership Project (3GPP) has devoted to some investigations, including the carrier aggregation (CA), coordinated multi-point transmission and reception (CoMP), and the heterogeneous networks (HetNets). The HetNets consists of normal base station and some low power nodes, such as Pico, femtocell, and relay nodes. Instead of the relatively high deployment cost and high transmission power, these nodes which feature some advantages like serving users in coverage holes, low cost and high design flexibility, are seen as a promising way to increase the capacity of the network.
In the HetNet, the Cell Range Expansion (CRE) is proposed to drive more users attaching the small nodes, which assigns a fixed bias value in the traditional way, but it will cause some issues about load balancing between the Macrocell and Picocells. The 3GPP also brings an energy-efficient mechanism to HetNets for switching off the small cells when the loading of them are low.
Hence, we proposed an efficient method to calculate the suitable bias value, and adapt it dynamically with the implement of Small Cell Switch off mechanism. Within this new adaptive method, we can balance the loading between the Macrocell and Picocells with the goal of minimizing energy consumption and improving the total network throughput through a better tradeoff.

學位論文審定書 i
論文公開授權書 ii
論文摘要 iii
Abstract iv
目錄 v
圖目錄 vii
表目錄 ix
第一章 導論 1
1.1 前言 1
1.2 研究動機 4
1.3 論文架構 6
第二章 相關背景與研究 7
2.1 長期演進技術(LTE)架構簡介 7
2.2 LTE無線存取技術 10
2.2.1正交分頻多重存取技術(OFDMA) 10
2.2.2單載波分頻多工存取技術(SC-FDMA) 11
2.2.3資源區塊(Physical Resource Block，PRB) 11
2.2.4通報品質指標(Channel Quality Indicator，CQI) 13
2.3基地台範圍擴展技術(Cell Range Expansion) 15
2.4基地台睡眠省電技術(Small Cell on/off) 17
2.5相關論文 19
第三章 研究方法 22
3.1 系統架構 22
3.2 基地台負載計算 26
3.3使用者分類機制 29
3.3.1 上行連接邊界計算 30
3.4動態Bias調整機制 32
3.4.1 Bias調整量計算 33
3.4.2 能源效率計算 34
第四章 效能與分析 39
4.1 模擬環境與參數設定 39
4.2 模擬結果與效能分析 41
第五章 結論 62
參考文獻 63

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