由於目前手機、個人電腦、個人數位助理(PDA)、數位電視、影音光碟機、液晶電視等消費電子產品的熱賣，加上數位廣播(digital audio broadcasting, DAB)以及數位電視等服務的陸續開通，未來任何一個具有顯示器的消費電子產品，都可能成為人們接收影音娛樂資訊的媒介。因此，宣稱“最大傳輸速度75Mbit/秒、最大傳輸距離可達50km”的無線都會區域網路(WiMAX)中，我們深信群播視訊將會是未來民生網路的重要應用之一，本篇論文主要目標是在WiMAX平台上，提出保證群播視訊(multicast video)服務品質的控制機制。
群播主要的問題是由於每個接收端的位置都不相同(location-dependent)，位置不同則會造成接收端有不同的SNR(signal to noise ratio)需求，因此傳送端無法依據每個接收端距離它的遠近來決定適當的調變機制，因此如何解決這個問題是本篇論文最主要的目的。
在本篇論文中我們將提出可調適速率分層群播(Rate-Adaptive Layered Multicast, 簡稱RALM)機制。RALM是利用分層分速率傳送的概念，在保證每一個接收端的基本接收品質下，按照目前接收端的分布情況，決定最適當的調變方式使得平均產能(average throughput)最大。最後我們用模擬的方法驗證在不同的接收端分佈底下我們的機制都能得到最大的平均產能。

In the future, any electrical consumption product with monitor may become a medium for receiving information of video-audio entertainment. Therefore, in WiMAX (which aims at providing data rate of 100Mbps and coverage of 50km) environment, the multicast video would be one of the potential killer applications. The main purpose of this thesis is to propose a control mechanism ensuring the quality of service (QoS) of multicast video in WiMAX.
The main problem of multicast is location-dependent characteristic. The location-dependent characteristic may lead inconsistent signal to noise ratio (SNR) requirement. Generally, the transmitter can not appropriately adjust the modulation scheme according to the distance of BS to each receiver. Therefore, this thesis expects to adjust the modulation scheme according to inconsistent SNR requirement of each receiver, to improve the multicast video quality.
This thesis proposes the Rate-Adaptive Layered Multicast scheme (RALM) RALM exploits the adaptive modulation scheme to transmit layered video data. RALM, which ensures the basic video quality, decides the most appropriate modulation scheme via the distribution of receivers to enable the maximum average throughput. This thesis also proceeds with simulation to provide the advanced discussion in different environment. The simulation results describes the RALM could acquire the maximum average throughput in different distribution of receivers.

[1] IEEE 802.16 std., “IEEE standard for local and metropolitan networks Part 16: Air Interfernce for Fixed Broadband Wireless Acess Systems,” Oct 2004.

[2] S. Redana, M. Lott,and A.Capone,”Performance evaluation of point-to-multi-point (PMP) and mesh air-interface in IEEE standard 802.16a,” IEEE Vehicular Technology Conference ( VTC) , pp.3186 – 3190, Sept 2004.

[3] A.Ghosh, D.R.Wolter, J.G. Andrews,and R. Chen, “Broadband wireless access with WiMax/802.16: current performance benchmarks and future potential,”IEEE Communications Magazine, pp.129 – 136, Feb 2005.

[4] S. G.. Lee, ”Performance of concatenated FEC under fading channel in
wireless-MAN OFDM system,” International Conference on Advanced Information Networking and Applications (AINA), pp.781 - 785 , March 2005.

[5] P. Ge, and P. K. McKinley, “Experimental evaluation of error control for video multicast over wireless LANs,” Proceedings of the IEEE International Conference on Distributed Computing Systems Workshop, pp. 301-306, 2001.

[6] N. Nikaein, H. Labiod and C. Bonnet, “MA-FEC: A QoS-Based Adaptive FEC for multicast communication in wireless networks,” Proceedings of the IEEE International Conference on Communications ( ICC), pp.954-958, 2000.

[7] Y. Xu and T. Zhang, “An adpative redundancy technique for wireless indoor multicasting,” Proceedings of the IEEE symbosium on computers and communications, pp. 607-614, 2000.

[8] D. Xu, B. Li, and K. Nahrstedt, “QoS-directed error control of video multicast in wireless networks,” Proceedings of the IEEE International Conference on Computer Communications and Networks, October 1999.

[9] B.Li,J.Liu,”Multirate video multicast over the internet: an overview,”IEEE Network , pp.24 – 29, Jan.-Feb 2003.

[10] U. T Nguyen, and X. Xiong,” Rate-adaptive multicast in mobile ad-hoc networks,”IEEE International Conference on Wireless And Mobile Computing, Networking And Communication , pp.:352 – 360, Aug 2005.

[11] S.McCanne, V.Jacobson, and M.Vetterli, “Receiver-driven layered multicast,”Proceedings of the ACM SIGCOMM, pp. 117–130, 1996.

[12] P. Osterberg, D. Forsgren, and T. Zhang, “Receiver-controlled joint source/channel coding on the application level, for video streaming over WLANs,” IEEE Semiannual Vehicular Technology Conference (VTC), pp. 1558-1561, April 2003.

[13] P. Chou, A. E. Mohr, A.Wang, and S. Mehrotra, “FEC and pseudo-ARQ for
receiver-driven layered multicast of audio and video,” Proceedings of the IEEE Data Compression Conference (DCC), pp. 440–449, Mar 2000.

[14] Q. Guo, Q. Zhang,W. Zhu, and Y.-Q. Zhang, “A sender-adaptive and receiver-driven layered multicast scheme for video over internet,” Proceedings of the IEEE International Symposium on Circuits and Systems (ISCAS), pp. 141–144, 2001.

[15] Q. Zhang, Q. Guo, Q. Ni, W. Zhu, and Y.-Q. Zhang, ”Sender-adaptive and
receiver-driven layered multicast for scalable video over the internet,” IEEE
Transactions on Circuits and Systems for Video Technology, pp.482 – 495, April 2005.

[16] Q. Ni, Q. Zhang, and W. Zhu, “SARLM: Sender-adaptive & Receiver-driven Layered Multicasting for Scalable Video,” Proceedings of the IEEE IEEE International Conference on Multimedia and Expo (ICME), pp. 757–760, Aug 2001.

[17] H.M Radha, M. van der Schaar, Y. Chen,The MPEG-4 fine-grained scalable video coding method for multimedia streaming over IP,” IEEE Transactions on Multimedia, pp.53 – 68, March 2001.

[18] A. Legout, “PLM: Fast convergence for cumulative layered multicast transmission Scheme,” Proceedings of ACM SIGMETRICS, 2000.

[19] C.S. Hwang,and Y. Kim, ”An adaptive modulation method for multicast
communications of hierarchical data in wireless networks,” IEEE International Conference on Communications, pp.896 – 900, 28 April-2 May 2002.

[20] V.S. Abhayawardhana, I.J. Wassell, D. Crosby, M.P. Sellars, M.G. Brown,“Comparison of empirical propagation path loss models for fixed wireless access systems,”IEEE Vehicular Technology Conference (VTC) , pp.73 -77 , May 2005.

[21] S. Sengupta, M. Chatterjee, S. Ganguly, R. Izmailov,” Exploiting MAC flexibility in WiMAX for media streaming,” IEEE International Symposium on World of Wireless Mobile and Multimedia Networks, pp.338 – 343, June 2005.

[22] L. Zhuo, K.M. Lam,and L. Shen,”Adaptive forward error correction for streaming stored MPEG-4 FGS video over wireless channel,” IEEE Workshop on Signal Processing Advances in Wireless Communications, pp.26 – 30, July 2004.

[23] J.R. Ohm, “Advances in scalable video coding,” Proceedings of the IEEE , Jan 2005.

[24] F.S.　Hiller,and G.J. Lieberman, Introduction to opreation reaserch, 7th ed., The McGraw-Hill Companies,2001.

[25] B.J. Kim, Z. Xiong and W. A. Pearlman, “Low bit-rate scalable video coding with 3-D et partitioning in hierarchical trees (3-D SPIHT),” IEEE Trans. on Circuits and Systems for Video Technology, Dec 2000.

[26] D.Pong,and T.Moors,”The impact of random waypoint mobility on infrastructure wireless networks” Proceedings of the IEEE International Conference on Parallel and Distributed Systems, pp.140 – 144, July 2005.