隨著行動通訊技術的發展，現已邁入第四代行動通訊系統(4G)的新紀元，其中又以長期演進技術(Long Term Evolution - Advanced, LTE-Advanced)為代表。LTE使用正交分頻多工(Orthogonal Frequency-Division Multiplexing, OFDM)及多輸入多輸出(Multi-Input Multi-Output, MIMO)技術以達到更高的資料傳輸速率。

在大樓林立的都會區，在室內或被建築物屏蔽的區域都會有訊號微弱的問題，因此3GPP制訂了femtocell以延伸基地台的覆蓋範圍，並做爲mobile data off-loading的重要解決方案。然而在現有的macrocell內佈建femtocell須克服干擾問題，並做好換手管理及功率控制等。本研究主要針對在LTE macrocell / femtocell的環境下，對干擾問題提出有效的解決方案。文獻中有FFR (Fractional Frequency Reuse)及SFR (Soft Frequency Reuse)兩個較為知名的方法，都是利用頻率重用的概念，以降低干擾並提升傳輸效能。然而它們的吞吐量(throughput)及頻譜使用效率(spectrum utilization)並不突出。此外，它們也未對LTE macrocell / femtocell的環境架構提出較為有效的解決方案。

在本論文中，我們提出一個調適性頻率重用(Dynamic Modification based Frequency Reuse, DMFR)的方法來克服干擾的問題，並能有效提升throughput及spectrum utilization。DMFR能藉由預留區塊的頻譜，避免cell內相鄰扇形區(adjacent sector)因發送相同頻率所造成的干擾；並能因應使用者在cell內實際分佈的情形，結合CoMP (Coordinated Multipoint) (JP及CS/CB)和MIMO的技術強化cell edge及cell sector的傳輸效能。

模擬實驗結果顯示，DMFR與FFR相比，其整體throughput將會比FFR提升將近三成(33.51%)，而頻譜使用率將比FFR提高將近一倍(99.87%)。

With the development of mobile communication technology, we are in the era of the fourth generation mobile communication systems (4G). Long Term Evolution - Advanced (LTE-Advanced) identifies itself as the main 4G system in the world. LTE uses OFDM (Orthogonal Frequency-Division Multiplexing) and MIMO (Multi-Input Multi-Output) technologies to achieve high data transmission rate.

In the urban city, those signals shaded by indoor buildings or outdoor high buildings are usually weak. 3GPP therefore specifies femtocells to extend the coverage of base stations. Moreover, femtocell is definitely a good solution for mobile data off-loading. However, there are some challenges the femtocells have to face given the femtocells are deployed in the coverage of macrocells. Examples are interference reduction, handover management, and power control, etc. This research focuses on the problem of interference avoidance and proposes an effective solution under the LTE microcell / femtocell architecture. In the literature, FFR (Fractional Frequency Reuse) and SFR (Soft Frequency Reuse) are well known methodologies based on the concept of frequency reuse. FFR and SFR are proposed to reduce interference and enhance transmission efficiency. However, their contributions to both throughput and spectrum utilization are not significant. Beside, they are not seem to be effective solutions to the systems under LTE microcell / femtocell architecture.

In this thesis, we propose a Dynamic Modification based Frequency Reuse (DMFR) method to solve the interference problem and is proved to be able to effectively increase throughput and spectrum utilization at the same time. DMRF uses the reserved spectrum to prevent the interference between adjacent sectors of a give cell. Besides, DMFR integrates both CoMP JP and CS/CB and MIMO to enhance the transmission efficiency to cell edge and cell sector.

Simulation results show that DMFR outperforms FFR in terms of throughput and spectrum utilization by 33.51% and 99.87%, respectively.

第一章 緒論 1
1.1 背景簡介 1
1.1.1 無線傳輸技術演進 1
1.1.2　OFDM基本架構 3
1.1.3　OFDMA基本架構 4
1.1.4　訊框格式 5
1.1.5 資源塊格式 6
1.2 MIMO技術簡介 7
1.3 Femtocell簡介 10
1.3.1 為何需要Femtocell 11
1.3.2 功率消耗 12
1.3.3 標準化管理 12
1.3.4 降低干擾 13
1.3.5 Femtocell的存取控制 13
1.4 多點協作傳輸（Coordinated Multipoint Transmission） 14
1.5研究動機 17
1.6論文架構 18
第二章 相關研究 19
2.1 Frequency Reuse 19
2.2軟式頻率重用（SFR） 19
2.3部分頻率重用（PFR） 20
2.4少量頻率重用（FFR） 21
2.5 Fractional Frequency Reuse for Interference Management in LTE-Advanced 22
第三章 研究方法 24
3.1問題分析 24
3.1.1　營運商建構成本太高 24
3.1.2 Femtocell的頻譜分配 24
3.2 DMFR（Dynamic Modification Based Frequency Reuse） 24
3.2.1 Cell整體的頻譜分配 24
3.2.2 Cell內相鄰sector間干擾消除 26
3.2.3 動態頻率分配 28
3.2.4 Cell Edge間的CoMP/JP （方法一） 29
3.2.5 Cell Sector利用CoMP/（CS/CB）和MIMO來重複使用頻譜（方法二） 29
3.2.6 Femtocell頻譜的配置 30
3.2.7方法流程 33
第四章 模擬實驗與結果分析 35
4.1實驗環境與假設 35
4.1.1　評估指標 35
4.1.2　模擬環境 36
4.2實驗數據與分析 37
4.2.1　實驗一 37
4.2.2　實驗二 39
第五章 結論與未來研究 411
5.1結論 411
5.2未來研究 422
參考文獻 43

[1] 3GPP TS 36.300, Evolved Universal Terrestrial Radio Access （E-UTRA）and Evolved Universal Terrestrial Radio Access Network （E-UTRAN）, Overall description; Stage 2, ver. 10.5.0.
[2] Po-Yen Huang, "Energy Saving of LTE-Advanced Network by Adaptive GREEN Operations," National Chengchi University July 2013
[3] Electronic Technology 無線電技術 URL：
http://www.electronictechnology.com/new/mgad.php?sublnk=article&;mcontentid=1314&;contentid=NDA1XzEyL2luZGV4Lmh0bWw=,
（hit 2013.7.16）.
[4] Shih-Jung Wu, "A New Handover Strategy between Femtocell and Macrocell for LTE-based Network," 2011 IEEE, 3-4 July 2011, 203 - 208.
[5] Presentations by ABI Research, Picochip, Arivana, IP access, Gartner, Telefonica Espana, 2nd Int’l Conf. Home Access Points and Femto- cells. [Online]. Available: http://www.avrenevents.com/dallas-femto2007/ purchase presentations.htm
[6] Hyoungwon Kwak,"Mobility Management Survey for Home-eNB Based 3GPP LTE Systems," Journal of Information Processing Systems, Vol.4, No.4, December 2008.
[7] Gavin Horn," 3GPP Femtocells: Architecture and Protocols," 3GPP Femtocells: Architecture and Protocols September 2010.
[8] Broadband forum"TR-069 CPE WAN Management Protocol," July 2011, Protocol Version: 1.3.
[9] A. Ghosh, R. Ratasuk, B. Mondal, N. Mangalvedhe and T. Thomas,
MOTOROLA INC., “LTE-advanced:next-generation wireless broadband
technology,” IEEE Wireless Communication, vol.17, no. 3, June 2010.
[10] Huawei, “Soft Frequency Reuse Scheme for UTRAN LTE,” 3GPP TSG RAN WG1 Meeting #41, R1-050507, May 2005.
[11] Siemens,“Interference Mitigation by Partial Frequency Reuse,” 3GPP TSG-RAN WG1 Meeting #44, R1-060670,February 2006.
[12] Poongup Lee, Taeyoung Lee, Jangkeun Jeong, and Jitae Shin," Interference Management in LTE Femtocell Systems Using Fractional Frequency Reuse" Feb. 7-10 2010, ICACT 2010.
[13] N. Saquib, E. Hossain, and D. I. Kim, “Fractional Frequency Reuse for Interference Management in LTE-Advanced HetNets,” IEEE Wireless Commun., vol. 20, pp. 113-122, Apr. 2013.
[14] “The Network Simulator ns-3” （NS-3）, Retrieved:
http://www.nsnam.org/docs/release/3.13/tutorial/singlehtml/index.html, February 2013.
[15] “Ns-3 LTE Module Documentation-LENA M2 Documentation,” Open Source Project. Retrieved:http://lena.cttc.es/manual/,February 2013.