LTE-A與Wi-Fi異質網路下之延遲敏感卸載機制

Delay-Sensitive Offloading in LTE-A and Wi-Fi Heterogeneous Networks

王一智(Yi-Chih Wang)

指導教授 ： 楊峻權

國立暨南國際大學/科技學院/資訊工程學系/碩士(2017年)

摘要

隨著科技的快速發展，行動裝置的普及率越來越高，功能也越來越多元化，導致行動網路的資料流量隨之急遽增加。目前4G網路標準的無線網路接取技術為進階長期演進技術(Long Term Evolution-Advanced, LTE-A)，LTE-A提供了100MHz的頻寬，當使用者在靜止狀態下的傳輸速度可達1Gbps，在高速移動的狀態下的傳輸速度也可達100Mbps。盡管傳輸速率很快但是流量依然有限，LTE-A仍然無法應付急劇增加的行動資料量需求，因而LTE-A基地台仍然發生了壅塞的情形，解決壅塞最直接的方式就是把資料流量轉移到其他的基地台，因此在LTE-A環境之下如何結合資料流量的卸載(Offloading)機制成為一個重要的議題。透過讓使用者裝置(User Equipment, UE)連接到其他的無線網路存取技術(例如Wi-Fi)的基地台進行流量的卸載是最有效且直接的解決辦法。本文中提出了以延遲做為決策依據的卸載與負載平衡機制，利用排隊理論(Queueing Theory)的M/G/1模型模擬網路的資料傳送行為計算基地台的封包延遲時間為UE選擇連接的基地台，並且設定基地台的延遲上限滿足UE服務品質(Quality of Service, QoS)的需求。在最後的效能評估與其他的卸載機制做效能比較，結果顯示本文提出的演算法在基地台平均延遲、延遲標準差與UE的延遲滿意度上都有突出的表現。

關鍵字

流量卸載 ； 長期演進技術進階版 ； Wi-Fi ； 延遲敏感 ； M/G/1 ； 異質網路

並列摘要

Long Term Evolution-Advanced (LTE-A) is one of the most popular radio access technologies (RATs), and it is also the major 4G mobile data transmission technology at present. With the popularity of mobile devices, the mobile data traffic demand has been growing explosively, and makes LTE-A base stations more congested. Therefore, traffic offloading to other networks is considered a promising solution. An effective and direct solution is offloading some User Equipment (UE) connections to different RATs (e.g. Wi-Fi.) Thus, how to make offloading decisions has become a significant issue.
In this thesis, a Delay-Sensitive Offloading scheme is proposed by which aim to satisfy the Quality of Service (QoS) delay demand of UEs. The delay of base station is calculated by M/G/1 queueing model. Besides, an appropriate access network for UEs will also be selected based on the delay of base stations and the packet delay budget of UEs. Moreover, a Multi-Hop Offloading scheme is proposed for reducing the delay of base stations and balancing the load among regional base stations. The simulation results shows that the proposed scheme can largely reduce the delay of base station and improve both load balancing and UE’s delay satisfaction.

並列關鍵字

Offloading ； LTE-A ； Wi-Fi ； Delay-sensitive ； M/G/1 ； Heterogeneous network

參考文獻

[1] S. Sesia, I. Toufik and M.P.J. Baker, LTE – The UMTS Long Term Evolution: From Theory to Practice, Wiley, April 2009.

[2] 3GPP TS 36.300, “Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN),” Rel. 10, v10.3.0, March 2011.

[3] A. Aijaz, H. Aghvami, and M. Amani, “A Survey on Mobile Data Offloading: Technical and Business Perspectives,” IEEE Wireless Communications Magazine, pp. 104-112, April 2013.

[4] IEEE Std. for Information technology - Telecommunications and information exchange between systems; Local and metropolitan area networks - Specific requirements; Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, IEEE Std. 802.11, March 2012.

[5] S. Sesia, I. Toufik, and M. Baker, LTE - The UMTS Long Term Evolution From Theory to Practice, 2nd Edition, Wiley, July 2011.