隨著手持裝置的普及化，使得人們對於網路的需求，逐日增加，像是收信、看臉書動態、使用即時通訊軟體VoIP或影音Video串流的需求。為了去滿足這些需求，LTE就此開始發展，而LTE訴求就是希望能夠達到下行(Downlink)傳輸速率能達到1Gbps，上行(Uplink)傳輸速率能達到500Mbps的要求。再透過異質性網路(HetNets)的建設，也能夠增加網路容納的能力，並去因應這些廣大的使用者需求。

而本篇論文主要是探討在Macrocell和Picocell所構成的異質性網路，而為了能讓Picocell可以達到舒緩的目的，而使用Cell Range Expansion(CRE)技術。但是若沒有考量到本身基地台的資源是否充足以及鄰近使用者的分布，就根據一固定的偏移植(Biased)，就將使用者轉移至Picocell做服務，則會發生Biased設定太小，無法發揮Picocell的舒緩目的，或者是Biased設定太大，導致鄰近過多的使用者與Picocell做服務，導致Picocell的資源競爭激烈。因此本篇論文提出一個機制能夠依照基地台的狀況以及使用者的分布來決定該使用者的Biased。

藉由模擬的呈現，我們的機制相較於CRE更能夠提升有效吞吐量、降低封包延遲時間以及減少封包遺失率，表現出我們的機制能夠隨著使用者的變化，來適時地去調整，幫助使用者能夠達到其對網路需求。

Due to the population of handheld devices, people are more depending on the wireless network. While wireless network is more important, 3GPP proposed a new wireless communication system ”Long Term Evolution” ,so called “4G-LTE”. LTE downlink data rate could be up to 1Gbps, and uplink data rate could be up to 500Mbps. The LTE has recently been investigating heterogeneous networks (HetNet) to deal with traffic demand.

In this paper, we focus on HetNets which consists of Macrocell and Picocells. Picocells use the Cell Range Expansion (CRE) technique to extend the Picocell coverage, so it can ease Macrocell traffic load. The CRE uses the biased to make user equipments (UE) offload to Picocell. However, there are some problems with CRE. First, if the biased is set a small value, the Picocell cannot cover more UEs to ease Macrocell traffic. Second, if the biased is set a large value, it may cover too more UEs such that Picocell cannot handle too many request. In this article, we present the mechanism that concerns the number of resources of the base stations and user conditions, and the mechanism will decide the UE’s biased.

In simulation results, it shows our mechanism can improve the average user goodput and total goodput、reduce the packet delay time and decrease the packet loss rate. According to the results, our mechanism adjusts the UE’s biased appropriately, and satisfy the QoS requirements of users.

學位論文審定書 i
論文摘要 ii
Abstract iii
目錄 iv
圖目錄 v
表目錄 vii
第一章 導論 1
1.1 簡介 1
1.2 研究動機 4
1.3 論文架構 7
第二章 相關背景與研究 8
2.1 長期演進技術架構介紹 8
2.2 LTE無線存取技術 11
2.2.1 正交分頻多重存取技術(OFDMA) 11
2.2.2 單載波分頻多工存取(SC-FDMA) 13
2.2.3 資源區塊(Physical Resource Block，PRB) 14
2.2.4 通道品質指標(Channel Quality Indicator，CQI) 16
2.3基地台範圍擴展(Cell Range Expansion) 18
第三章 協定機制制定 21
3.1機制所需資訊 23
3.1.1參考訊號接收能量 23
3.1.2 基地台所需資訊 28
3.2流程架構 31
3.3調整Biased機制 33
3.4舒緩Picocell機制 50
3.5分時機制 54
3.6 分析 54
第四章 模擬與分析 55
4.1 模擬環境與參數設定 56
4.2 模擬結果與效能分析 58
第五章 結論 73
參考文獻 74

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