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研究生:陳宜玄
研究生(外文):Yi-Hsuan Chen
論文名稱:無線區域網路中改善換手機制效能之研究
論文名稱(外文):Mechanisms for Improving Handoff Performance in IEEE 802.11 WLANs
指導教授:黃政吉黃政吉引用關係
指導教授(外文):Jeng-Ji Huang
學位類別:碩士
校院名稱:國立臺灣師範大學
系所名稱:工業教育學系
學門:教育學門
學類:專業科目教育學類
論文種類:學術論文
論文出版年:2007
畢業學年度:95
語文別:中文
論文頁數:36
中文關鍵詞:無線區域網路網路電話雙向語音狀態排程換手機制
外文關鍵詞:wireless local area networkvoice over internet protocolvoice activityschedulinghandoff
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無線區域網路(wireless local area network, WLAN)中,行動節點在無線存取點(access point,AP) 之間進行換手(handoff)時所產生的延遲時間,將嚴重地影響即時性(realtime)網路應用的服務品質,例如網路語音電話(voice over Internet protocol,VoIP)。主要的原因是由於過長的換手時間,將造成VoIP封包遺失甚至換手失敗。先前的研究顯示換手時所需花費的時間,主要是在於通道掃描(channel scanning)的階段。因此,在本論文中,將針對通道掃描設計排程演算法(scheduling algorithm),以使得行動台在進行換手程序時,不但VoIP封包遺失率可滿足服務品質(quality of service, QoS)之要求,並可有效地降低換手失敗的機率。本論文所提出之排程演算法主要考慮語音電話雙向使用者之通話狀態,並利用不發音時(silent period)安排通道掃描順序。本論文將採用電腦模擬的方式,以分析排程演算法之相關效能指標,其中包含VoIP封包遺失率(packet loss rate)以及換手成功機率(handoff success probability)。本論文所獲得之結果,預期將可作為設計無線區域網路系統時之重要參考。
To guarantee seamless handoffs between access points (APs) is one of the most decisive factors in providing real time applications such as voice over internet protocol (VoIP) in IEEE 802.11 networks. It is because in wireless local area networks (WLANs) there is no specific control channel for executing a handoff process and a mobile station (MS) has to search for new APs from channel to channel by temporarily disconnecting its association with the old AP. While previous studies are mainly focused on how to reduce the handoff latency, in this paper a channel scanning algorithm is proposed to schedule suitable time for performing a handoff process efficiently. In the proposed algorithm, the voice activity is taken into consideration, and the handoff process is performed during silent periods. Extensive simulations are conducted to investigate the performance of the proposed algorithm in terms of the handoff success probability and the packet loss rate, and the results obtained in this paper can serve as a good reference for the system design.
第一章 緒論 6
1.1前言 6
1.2研究動機與目的 6
1.3論文架構 7
第二章 IEEE 802.11通訊協定的簡介 8
2.1 IEEE 802.11無線網路簡介 8
2.2 IEEE 802.11 MAC LAYER 9
2.2.1 Infrastructure Mode與 Ad-Hoc 10
2.2.2 IEEE 802.11的服務方式 10
2.2.3 IEEE 802.11的網路掃瞄 13
2.2.4 由原本的AP切換到另一個AP決定點 15
2.3 相關研究 15
第三章 研究方法 23
3.1 雙向語音狀態(VOICE ACTIVITY) 23
3.2 通道掃描(CHANNEL SCANNING) 25
3.3 排程演算法(SCANNING ORDER) 26
3.4 模擬環境 28
3.5 效能分析 30
3.6 增強效能之演算法 31
第四章 結論 34
參考文獻 35
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[2] IEEE Std 802.11b-1999, Part 11:Wireless LAN Medium Access Control(MAC) and Physical Layer(PHY) specifications: Higher-Speed Physical Layer Extension in the 2.4 GHz Band.
[3] A. Mishra et al., “An Empirical Analysis of the IEEE 802.11 MAC Layer Handoff Process,” ACM SIGCOMM Computer Communications Review, vol. 33, no. 2, Apr. 2003, pp. 93-102.
[4] International Telecommunication Union, General Characteristics of International Telephone Connections and International Telephone Circuits,ITU-TG.114, 1998
[5] http://www.ndc.com.tw/products/nwh4020.htm
[6] Lucent Technologies Inc., “Roaming with WaveLAN/IEEE 802.11,” Tech. Rep. WaveLan Technical Bulletin 021/A, Dec. 1998.
[7] I. Ramani and S. Savage, “SyncScan: Practical fast handoff for 802.11 infrastructure networks,” IEEE Infocom 2005, Mar. 2005,pp. 675-684.
[8] S.-K. Chui and O.-C. Yue, “An Access Point Coordination System for Improved VoIP/WLAN Handover Performance,” IEEE VTC’06-Spring, vol.1, May 2006, pp. 501-505.
[9] S. S. Andrea, G. Forte, A. S. Rawat, and H. Schulzrinne, "Reducing MAC Layer Handoff Latency in IEEE 802.11 Wireless LANs," Proc. ACM WMASH 2004, Oct. 2004.
[10] J. Montavont and Montavont, ”Enhanced schemes for L2 handover in IEEE 802.11 networks and their evaluations,” Personal, Indoor and Mobile Radio Communications, 2005 IEEE 16th International Symposium on, vol.3, Sep. 2005, pp. 1429-1434.
[11] H. Velayos and G. Karlsson, “Techniques to Reduce IEEE 802.11b MAC Layer Handover Time,” Proc. IEEE ICC 2004, June 2004.
[12] K. Kwon and C. Lee, “A Fast Handoff Algorithm Using Intelligent Channel Scan for IEEE 802.11 WLANs,” IEEE 6th International Conference, vol. 1, 2004, pp. 46- 50.
[13] W. Li, Q.-A. Zeng and Agrawal, “A reliable active scanning scheme for the IEEE 802.11 MAC layer handoff,“ Radio and Wireless Conference, Aug. 2003, pp. 71-74.
[14] A. Mishra et al., “Context Caching using Neighbor Graphs for Fast Handoffs in a Wireless Network,” in Proc. IEEE INFOCOM, vol.1, Mar. 2004, pp. 351-361.
[15] C.C. Tseng, K.H. Chi, M.D. Hsieh, and H.H. Chang, “Location-based fast handoff for 802.11 networks,” IEEE Communications letters, vol. 9, no. 4, Apr. 2005, pp. 304- 306.
[16] S. Pack and Y. Choi, “Fast handoff scheme based on mobility prediction in public wireless LAN systems,” Communication IEE proceedings, vol. 151, 24 Oct. 2004, pp. 489-495.
[17] P.-J. Huang, Y.-C. Tseng and K.-C. Tsai, “A Fast Handoff Mechanism for IEEE 802.11 and IAPP Networks,” IEEE VTC’06-Spring, vol. 2, 2006, pp. 966-970.
[18] Manodham, Loyola, G. Atoche, and Hayasaka, “A novel handover scheme for reducing latency in WLANs,“ IEEE VTC’05-Spring, vol.2, Sep. 2005, pp. 1141-1144.
[19] S. Kashihara and Y. Oie,“ Handover Management based on the Number of Retries for VoIP on WLANs,” IEEE VTC’05-Spring, vol. 4, May 2005, pp. 2201-2206.
[20] Y. Liao and L. Cao, “Practical schemes for smooth MAC layer handoff in 802.11 wireless networks,“ IEEE WoWMoM 2006, June 2006, pp. 10.
[21] Jaeouk, Pedro and Hiroyuki, “Using Shared Beacon Channel for Fast Handoff in IEEE 802.11 Wireless Networks,” IEEE VTC’07-Spring.
[22] Singh and D. Hoh,“ Qualitative Study of Intelligent Access Point Handover in WLAN Systems,” IEEE NOMS 2006, pp. 1-4.
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