IEEE 802.16e無線都會型網路針對行動用戶站 (Mobile Station)提供了寬頻無線網路存取 (Broadband Wireless Internet Access)的支援，鑑於使用者具有行動能力，故如何節省電池能源的耗損以延長工作時間，成為很值得關注的議題。在IEEE 802.16e標準中，能源的節省是藉由令行動用戶站進入睡眠模式來達成，並因應不同的傳輸型態訂立了三種能源節省類型，其中能源節省類型I適用於非即時性 (Non-Real-Time)服務連線，然而在同一行動用戶站中，亦可能同時共存著即時性 (Real-Time)服務連線，因此僅考慮單一連線類型並不能反應行動用戶站的真實情境，其他能源節省類型理應加入考慮。
本論文針對此點探討能源節省類型I所需的規劃，並提出了考量多種省電類別共存之預測式省電機制，本機制藉由對能源節省類型I及II進行同步規劃，得到最大化的共同睡眠區間，而在單一非即時性傳輸連線時，則對封包抵達間隔與能源節省類型II之出現間隔作預測，藉此規劃能源節省類型I所採用的睡眠區間大小。模擬的結果顯示，本論文所提出的方法於封包延遲時間與節能省電部份皆優於IEEE 802.16e中的標準睡眠機制；而即使標準機制亦加入對能源節省類型II的同步操作，本機制仍有較佳的表現。

The IEEE 802.16e wireless metropolitan area network provides broadband wireless Internet access for mobile stations (MSs). Due to user mobility, how to save batteries to prolong the lifetime is an issue receiving much attention. Specified in the IEEE 802.16e standard, energy conservation is reached by allowing MSs to enter the sleep mode according to the three defined power saving classes for different traffic, for example, the power saving class of type I is suitable for the non-real-time traffic. However, non-real-time and real-time traffic may coexist in a MS. Therefore, other power saving classes should be simultaneously considered to reflect the real situation instead of considering the individual traffic type.
Aiming at this goal, we propose a predictive power saving mechanism for the power saving class of type I considering coexistence of the power saving class of type II. Through synchronizing power saving classes I and II, the unavailability interval is maximized by our proposed scheme. Predicting the inter-packet arrival time as well as the time interval between two occurrences of the power saving class of type II, the sleep interval of the power saving class of type I is suitably designed based on the predicted result when only the power saving class of type I is under consideration. Via simulations, we show that the proposed scheme outperforms the standard mechanism for the power saving class of type I in IEEE 802.16e in terms of packet delay and energy conservation. Even the standard mechanism works with the synchronization operations, our scheme still performs better than the combined mechanism.

[1] J. F. Kurose and K. W. Ross, 2005, "Computer Networking," 3rd ed. pp. 589 - 590, Addison Wesley, United States.
[2] L. Burgstahler and M. Neubauer, "New modifications of the exponential moving average algorithm for bandwidth estimation," in Proc. ITC Specialist Seminar '02, 2002.
[3] S. K. Cho and Y. G. Kim, "Improving power savings by using adaptive initial-sleep window in IEEE802.16e," in Proc. IEEE VTC '07, 2007, pp. 1321 - 1325.
[4] R. Cohen, L. Katzir, and R. Rizzi, "On the trade-off between energy and multicast efficiency in 802.16e-like mobile networks," IEEE Trans. Mobile Computing, vol. 7, no. 3, pp. 346 - 357, Mar. 2008.
[5] K. Han and S. Choi, "Performance analysis of sleep mode operation in IEEE 802.16e mobile broadband wireless access systems," in Proc. IEEE VTC '06, 2006, pp. 1141 - 1145.
[6] IEEE Computer Society LAN MAN Standards Committee, "IEEE Std 802.11: Wireless LAN medium access control and physical layer specifications," 1999.
[7] IEEE 802.16-2001, "IEEE standard for local and metropolitan area networks - Part 16: Air interface for fixed broadband wireless access systems," 2002.
[8] IEEE 802.16-2004, "IEEE standard for local and metropolitan area networks - Part 16: Air interface for fixed broadband wireless access systems," 2004.
[9] IEEE 802.16e-2005, "IEEE standard for local and metropolitan area networks Part 16: Air interface for fixed and mobile broadband wireless access systems amendment 2: physical and medium access control layers for combined fixed and mobile operation in licensed bands and corrigendum 1," 2006.
[10] D. G. Jeong and W. S. Jeon, "Performance of adaptive sleep period control for wireless communications systems," IEEE Trans. Wireless Communications, vol. 5, no. 11, pp. 3012 - 3016, Nov. 2006.
[11] K. Lei and D. H. K. Tsang, "Performance study of power saving classes of type I and II in IEEE 802.16e," in Proc. IEEE LCN '06, 2006, pp. 20 - 27.
[12] K. Lei and D. H. K. Tsang, "Optimal selection of power saving classes in IEEE 802.16e," in Proc. IEEE WCNC '07, 2007, pp. 1836 - 1841.
[13] D. T. T. Nga, M. G. Kim, and M. Kang, "Delay-guaranteed energy saving algorithm for the delay-sensitive applications in IEEE 802.16e systems," IEEE Trans. Consumer Electronics, vol. 53, no. 4, pp. 1339 - 1347, Nov. 2007.
[14] O. J. Vatsa, M. Raj, K. Ritesh, D. Panigrahy, and D. Das, "Adaptive power saving algorithm for mobile subscriber station in 802.16e," in Proc. IEEE COMSWARE '07, 2007, pp. 1 - 7.
[15] Y. Xiao, "Energy saving mechanism in the IEEE 802.16e wireless MAN," IEEE Commun. Lett., vol. 9, no. 7, pp. 595 - 597, Jul. 2005.
[16] S. Q. Zhu and T. L. Wang, "Enhanced power efficient sleep mode operation for IEEE 802.16e based WiMAX," in Proc. IEEE MWS '07, 2007, pp. 43 - 47.
[17] Y. Zhang and M. Fujise, "Energy management in the IEEE 802.16e MAC," IEEE Commun. Lett., vol.10, no.4, pp. 311 - 313, Apr. 2006.
[18] N. M. P. Nejatian, M. M. Nayebi, and F. Ashtiani, "Effect of different traffic patterns on power consumption of sleep mode in the IEEE 802.16e MAC," in Proc. IEEE ICTMICC '07, 2007, pp. 649 - 653.
[19] J. Xue, Z. Yuan, H. Chen, A. Zhang, and W. Xu, "A traffic-aware adaptive sleep mode operation for IEEE 802.16e based WiMAX," in Proc. IEEE NSWCTC '09, 2009, pp. 304 - 307.
[20] L. Meng, D. Zhu, "A hybrid algorithm in IEEE 802.16e sleep mode operation," in Proc. IEEE WiCOM '08, 2008, pp. 1 - 3.
[21] H. Y. Li, 2008, "Design of predictive and dynamic power saving mechanisms for the IEEE 802.16e wireless MAN," Master thesis, Department of Computer Science, National Taiwan University of Science and Technology, TW.
[22] Y. P. Hsu and K. T. Feng, "Performance modeling of power saving classes with multiple connections for broadband wireless networks," in Proc. IEEE WCNC '08, 2008, pp. 1477 - 1482.
[23] T. C. Chen, Y. Y. Chen and J. C. Chen, "An efficient energy saving mechanism for IEEE 802.16e wireless MANs," IEEE Trans. Mobile Computing, vol. 7, no. 10, pp. 3708 - 3712, Oct. 2008.
[24] T. C. Chen, J. C. Chen and Y. Y. Chen, "Maximizing unavailability interval for energy saving in IEEE 802.16e wireless MANs," IEEE Trans. Mobile Computing, vol. 8, no. 4, pp. 475 - 487, Apr. 2009.
[25] T. C. Chen and J. C. Chen, "Energy management in the IEEE 802.16e MAC," IEEE Commun. Lett., vol.13, no.2, pp. 151 - 153, Feb. 2009.