無線網路下具高敏銳度的移動偵測演算法

近年來，各種的無線網路(3G/WLAN/WiMAX)被廣泛的佈建，產生許多可提供不同無線網路服務的重疊區域。而手持系統在未來將會提供多個無線網路接取介面來連接不同的網路，使得多介面的手持系統可以依照移動的方向來選擇最合適的無線網路。然而如何在異質性網路下提供平順的換手機制是重要的議題。雖然移動終端可以透過啟動所有無線網路接取介面來監控所有無線網路服務狀況，並選擇較合適的無線網路進行換手，但是這樣會造成額外的電源浪費，使移動終端可以運作的時間大幅減少。本篇論文針對這樣的情況，提出一個AMRSS（Averaged Momentum of Received Signal Strength）平均動量移動偵測演算法，此演算法可以協助移動終端僅透過接收的訊號強度（Received Signal Strength）來預測移動終端的移動行為，而不用借助定位系統。藉由移動終端行為的資訊，移動終端可以適時的進行可用無線網路的搜尋，而透過敏銳的偵測，可以避免換手的失敗機率以及電源的消耗。另外，AMRSS提供在換手過程中避免乒乓效應的演算法。模擬結果顯示，AMRSS可以敏銳的偵測移動終端行為，降低能源消耗以及避免乒乓效應。而且AMRSS是一般性的動態偵測演算法，異質性無線網路環境也可以透過同樣的設定值來偵測移動終端行為。

關鍵字

換手；網路探索；異質性網路；動態偵測；接收訊號強度；乒乓效應

並列摘要

Recently, wireless networks of various types, such as third-generation Wireless Wide Area Networks (3G), Wireless Local Area Networks (WLANs) and Worldwide Interoperability for Microwave Access (WiMAX) have been deployed widely and cover many areas that are overlapped with one another. In the future, many handsets will be featured with several interfaces to access these networks. Such multi-mode handsets can access to an appropriate wireless network wherever they go. Therefore, it is critical to providing smooth handoff when the mobile users move around in a heterogeneous wireless network environment. Although a mobile node (MN) can enable all its interfaces to constantly monitor surrounding access networks so as to select an appropriate access network whenever possible, the power consumption of these interfaces will quick drain the power of battery. In this thesis, we propose an approach called Averaged Momentum of Received Signal Strength, AMRSS, to detect user’s motion without the assistance of a positioning system. While AMRSS exploits RSS only, it is simple and sensitive in detect users’ motion. With AMRSS, a MN can trigger its interfaces to discover available wireless access networks only when it is moving out of the coverage area of current access point, leading to significant reduction in power consumption and improving in the handoff success rate. To improve sensitivity of motion detection, AMRSS is designed to be adaptive on users’ motion. Furthermore, a ping-pong effect avoidance algorithm (PEA) based on AMRSS is presented to prevent a MN from switching back and forth between APs. Simulation results show that AMRSS has high motion detection sensitivity and accuracy. Furthermore, PEA can also effectively lower the number of handoffs than existing prediction algorithms. Also, AMRSS can detect user motion in various wireless networks without using different set of smoothing factors. Therefore, it offers a general solution for motion detection in heterogeneous networks.

並列關鍵字

Handoff ； Network Discovery ； Heterogeneous Network ； Motion detection ； Received Signal Strength (RSS) ； Ping-Pong Effect

參考文獻

[1] G.P. Pollini, “Trends in Handover design”, IEEE Commun. Mag., vol. 34, no. 3, Mar.1996, pp. 82-90

[3] I. Ramani and S. Savage,“SyncScan: Practical fast handoff for 802.11 infrastructure networks”, Proc. IEEE INFOCOM, vol. 1, 2005, pp. 675-684

[4] A. Mishra, M.-H. Shin, and W.A. Arbaugh, “Context caching using neighbor graphs for fast handoffs in a wireless network,” Proc. IEEE INFOCOM, vol. 1, 2004, pp. 351-361

[5] S.K. Kim, C.G. Kang, and K.S. Kim, “A adaptive handover decision algorithm based on the estimating mobility from signal strength measurements,” IEEE VTC, vol. 60, no. 2, 2004, pp. 1004-1008

[6] S. McCann et al., “Next generation multimode terminals,” IEE International Conference, 2004, pp. 143-147

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無線網路下具高敏銳度的移動偵測演算法

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