在行動無線網路中，由無線傳輸與使用者移動所產生的不確定性，將會導致傳輸鏈路品質的不穩定。要建立並維持一條可靠的無線鏈路，需要對此鏈路其未來的穩定性有進一步的了解。因此如何預估一條鏈路的未來穩定度，成為行動無線網路一個非常重要的課題。由於鏈路穩定度與使用者移動性息息相關，可以將這個課題分成兩個部份進行深入探討：（一）探討無線傳輸效應以及使用者移動參數對於鏈路穩定度變動之影響及相關性分析，（二）探討如何取得使用者之移動參數。對應上述二點，本論文之二大主題為：鏈路穩定度預估與使用者移動性估測。在第一主題中，我們基於當下所取得的鏈路相關資訊與移動性資訊，提出一個鏈路穩定度預估之演算法。在推導穩定度預估子的過程中，我們考慮一個實際的使用者移動模型，與一個符合現實環境的無線傳輸模型，其中包含一相關性遮蔽效應模型。數值分析與模擬結果證明了我們的穩定度預估子可在不同的環境與移動性的條件下，準確預估鏈路穩定度。我們也驗證了此穩定度預估方法，對於在多躍式行動無線網路中搜尋穩定路由具有極重要的幫助。除此之外，穩定度預估子亦可應用在許多技術上，例如鏈路效能預估、系統效能預估或服務品質預估等等。
本論文的第二個主題—使用者移動性估測，是利用接收之參考訊號，其感受無線通道之大範圍衰減與小範圍衰減，進行用戶位置、移動速度以及移動方向之估測。我們使用一個位置追蹤演算法，利用參考訊號之接收訊號強度進行用戶位置與移動方向的計算。由於接收訊號強度極易受到無線通道中遮蔽效應的影響，我們利用真實傳輸環境下遮蔽效應的相關性，來輔助位置追蹤並增加準確率。我們提出的位置追蹤演算法包含一個基於最大似然法則之位置估計子，以及一個基於卡門濾波器之遮蔽效應追蹤器，以期同時追蹤使用者位置與對應之遮蔽效應。模擬結果顯示，在只知道移動速度，而沒有使用者移動模型的情形下，遮蔽效應追蹤器提供給位置估計子有用的遮蔽效應資訊，使得整個位置追蹤演算法能有效地同時追蹤使用者位置與遮蔽效應。
行動用戶之速度，可根據使用者感受到無線通道之小範圍衰減效應進行估測，等同於估測此通道之都普勒擴散值。基於最大似然法則之都普勒擴散估測子能有效率且準確地估測都普勒擴散，然而它卻具有極高的運算複雜度。因此針對平坦的雷利衰減通道，我們提出了一個近似最大似然法則之都普勒擴散估測子，它可以非常顯著地降低運算複雜度，卻仍然保有與原始最大似然估計子極為接近的估測效能。此外，即便使用少量的取樣點進行運算，近似最大似然估計子已經是一個趨近無偏的估計子。

[1] C. K. Toh, “Associativity-based routing for ad hoc networks,” Wireless Personal Commun., Kluwer Academic, vol. 4, pp. 103–109, March 1997.
[2] R. Dube, C. Raia, K-Y Wang and S. Tripathi, “Signal stability based adaptive routing (SSA) for ad hoc networks,” IEEE Personal Commun., vol. 4, no.1, pp. 36–45, Feb. 1997.
[3] K. Paul, S. Bandyopadhyay, A. Mukherjee and D. Saha, “Communication-aware mobile hosts in ad-hoc wireless network,” in Proc. IEEE Int. Conf. Personal Wireless Commun. (ICPWC), pp. 83–87, 17-19 Feb. 1999.
[4] S. Agarwal, A. Ahuja, J. Singh, and R. Shorey, “Route-Lifetime Assessment Based Routing (RABR) Protocol for Mobile Ad-Hoc Networks,” in Proc. IEEE Int. Conf. Commun. (ICC), pp. 1697–1701, 18-22 June 2000.
[5] A. Bruce McDonald and T. F. Znabi, “A path availability model for wireless ad hoc networks,” in Proc. IEEE Wireless Commun. and Networking Conf. (WCNC), vol. 1, pp. 35–40, 21-24 Sept. 1999.
[6] S. M. Jiang, D. J. He, and J. Q. Rao, “A prediction-based link availability estimation for mobile ad hoc networks,” in Proc. 20th Annual Joint Conference of the IEEE Computer and Communications Societies (INFOCOM 2001), vol. 3, pp. 1745–1752, April 2001.
[7] S. M. Jiang, “An enhanced prediction-based link availability estimation for MANETs,” IEEE Trans. on Commun., vol. 52, no. 2, pp. 183–186, Feb. 2004.
[8] M. D. Dikaiakos, A. Florides, T. Nadeem, and L. Iftode, “Location-aware services over vehicular ad-hoc networks using car-to-car communication,” IEEE J. Select. Area Commun., vol. 25, no. 8, pp. 1590–1602, Oct. 2007.
[9] H.-Q. Lai, A. Ibrahim, and K. J. R. Liu, “Wireless network cocast: location-aware cooperative communications with linear network coding,” IEEE Trans. Wireless Commnu., vol. 8, no. 7, pp. 3844–3854, July 2009.
[10] M. Gudmundson, “Correlation model for shadow fading in mobile radio systems,” Electron. Lett., vol. 27, pp. 2145–2146, Nov. 1991.
[11] G. L. Stüber, Principles of Mobile Communication, 2nd Ed., MA: Norwell, Kluwer Academic Publishers, 2001.
[12] D. Giancristofaro, “Correlation model for shadow fading in mobile radio channels,” Electron. Lett., vol. 32, no. 11, pp. 958–959, May 1996.
[13] Z. Wang, E. K. Tameh, and A. R. Nix, and O. Gasparini, “A joint shadowing process model for multihop/ad-hoc networks in urban environment,” in Proc. 11th WWRF meeting, June 2004.
[14] Z. Wang, E. K. Tameh, and A. R. Nix, “Joint shadowing process in urban peer-to-peer radio channels,” IEEE Trans. Veh. Technol., vol. 57, no. 1, pp. 52–64, Jan. 2008.
[15] A. A. Abu-Dayya and N. C. Beaulieu, “Comparison of methods of computing correlated lognormal sumdistributions and outages for digital wireless applications,” in Proc. IEEE Veh. Technol. Conf. (VTC), vol. 1, pp. 175–179, 8-10 June 1994.
[16] William F. Ames, Numerical Methods for Partial Differential Equations, NY: Academic Press, 1977.
[17] M. Kendall and A. Stuart, Advanced Theory of Statistics, 4th Ed., NY: MacMillan Publishing Co., 1977.
[18] J. M. Holtzman, “On using perturbation analysis to do sensitivity analysis: derivatives vs. differences,” in Proc. IEEE Conf. Decision and Control, vol. 3, pp. 2018–2023, 13-15 Dec. 1989.
[19] S. Sakagami, S. Aoyama, K. Kuboi, and A. Akeyama, “ Vehicle position estimation by multibeam antennas in multipath environments,” IEEE Trans. Veh. Technol., vol. 41, pp. 63–68, Feb. 1992.
[20] L. Cong and W. Zhuang, “Hybrid TDOA/AOA mobile user location for wideband CDMA cellular systems,” IEEE Trans. Wireless Commun., vol. 1, pp. 1439–1447, July 2002.
[21] Z. R. Zaidi and B. L. Mark, “Real-time mobility algorithms for cellular networks based on Kalman filtering,” IEEE Trans. Mobile Computing, vol. 4, no.2, pp. 195–208, March/April 2005.
[22] B. L. Mark and Z. R. Zaidi, “Robust mobility tracking for cellular networks,” Proc. IEEE Int. Commun. Conf. (ICC), pp. 445–449, May 2002.
[23] T. Liu, P. Bahl, and I. Chlamtac, “Mobility modeling, location tracking, and trajectory prediction in wireless ATM networks,” IEEE J. Select. Areas Commun., vol. 16, pp. 922–936, Aug. 1998.
[24] L. Xiao, L. J. Greenstein, and N. B. Mandayam, “Sensor-assisted localization in cellular systems,” IEEE Trans. Wireless Commun., vol. 6 no. 12, pp. 4244–4248, Dec. 2007.
[25] J. M. Mendel, Lessons in Estimation Theory for Signal Processing, Communications, and Control, Englewood Cliffs, NJ: Prentice Hall Inc., 1995.
[26] B. Parkinson and J. Spilker, Global Positioning System: Theory and Application, Washington DC: American Institute of Astronautics and Aeronautics, 1996.
[27] W. Sheng and S. D. Blostein, “SNR-independent velocity estimation for mobile cellular communications systems,” in Proc. IEEE Int. Conf. Acoustics, Speech, and Signal Processing (ICASSP), vol. 3, pp. 2469–2472, 13-17 May 2002.
[28] C. Tepedelenlioglu, “Performance analysis of velocity (Doppler) estimators in mobile communications,” in Proc. IEEE Int. Conf. Acoustics, Speech, and Signal Processing (ICASSP), vol. 3, pp. 2201–2204, 13-17 May 2002.
[29] G. Park, S. Nam, T. Yu, D. Hong, and C. Kang, “A modified covariance-based mobile velocity estimation method for Rician fading channels,” IEEE Commun. Lett., vol. 9, no. 8, pp. 706–708, Aug. 2005.
[30] M. D. Austin and G. L. St ¨ uber, “Velocity adaptive handoff algorithms for microcellular systems,” IEEE Trans. Veh. Technol., vol. 43, no. 3, part 1-2, pp. 549–561, Aug. 1994.
[31] G. Park, D. Hong, and C. Kang, “Level crossing rate estimation with Doppler adaptive noise suppression technique in frequency domain,” in Proc. IEEE 58th Veh. Technol. Conf. (VTC 2003-Fall), vol. 2, pp. 1192–1195, 6-9 Oct. 2003.
[32] C. Juncker, P. Toft, and N. Mørch, “Speed estimation for WCDMA based on the channel envelope derivative,” in Proc. 4th IEEE Workshop on Signal Processing Advances in Wireless Commun. (SPAWC 2003), pp. 527–531, 15-18 June 2003.
[33] S. Mohanty, “VEPSD: a novel velocity estimation algorithm for next-generation wireless systems,” IEEE Trans. Wireless Commun., vol. 4, no. 6, pp. 2655–2660, Nov. 2005.
[34] 3GPP TR 25.913 V8.0.0, Universal Mobile Telecommunications System (UMTS); LTE; Requirements for Evolved UTRA (E-UTRA) and Evolved UTRAN (E-UTRAN), Jan. 2009.
[35] A. Dogandzic and B. Zhang, “Estimating Jakes’ Doppler power spectrum parameters using the whittle approximation,” IEEE Trans. Signal Processing, vol. 53, no. 3, pp. 987–1005, Mar. 2005.
[36] L. Krasny, H. Arslan, D. Koilpillai, and S. Chennakeshu, “Doppler spread estimation in mobile radio systems,” IEEE Commun. Lett., vol. 5, no. 5, pp. 197–199, May 2001.
[37] A. Wiesel, J. Goldberg, and H. Messer-Yaron, “SNR estimation in time-varying fading channels ,” IEEE Trans. Commun., vol. 54, no. 5, pp. 841–848, May 2006.
[38] L. Li, L. Fang, and F. B. Gross, “A new polynomial approximation for Jv Bessel functions,” in Proc. Asia-Pacific Microwave Conf., vol. 4, pp. 4–7, Dec. 2005.
[39] R. W. Farebrother, Linear Least Squares Computations, NY: Marcel Dekker, 1988
[40] T. Jiang, N. D. Sidiropoulos, and Georgios B. Giannakis, “Kalman filtering for power estimation in mobile communications,” IEEE Trans. Wireless Commun., vol. 2, no. 1, pp. 151–161, Jan. 2003
[41] I. Gradshteyn and I. Ryzhik, Table of Integrals, Series and Products, CA: Academic Press, 1980.