由於多媒體服務的需求迅速增加，第三代合作夥伴計劃(3GPP)提出了多媒體廣播/群播服務的技術來因應此需求。而多媒體廣播/群播服務也支援多重解析度服務的多媒體資料串流，並且能夠有效地增加系統吞吐量，不同的解析度被視為不同的服務層級。傳送端在彼此間獨立且不同的通道上傳送不同解析度的資料串流，因此會導致資源的使用較沒效率。而在接收端有部分，在高解析度服務通道上傳送的資料裡包含了用來提升低解析度的服務層級的接收訊號品質的可利用資料。於是，我們提出了多階層結合調變和混合式自動重送請求技術來改善資源使用的效率以及增加系統的吞吐量和服務範圍。多階層結合調變法能夠完整地利用所有在不同通道中傳送的重要資訊，而混合式自動重送請求技術在系統的第一次傳送結束後進行第二次傳送，因此可增加多樣性使接收效能能夠有效地改善。在此篇研究中，我們將會討論四種不同的傳送方案，而每一種方案代表傳送端都將會重新傳送一個特定服務層級的訊號。在我們的研究中，主要探討的主題是選擇哪一個服務層級的訊號來重傳能夠得到對整體系統有較好的性能，在我們的模擬結果中可以觀察出混合式自動重送請求技術能夠有效地改善系統的接收品質，並且能夠得到一個對整體系統性能有最大益處的重傳機制。

[1] “Technical specification 3rd generation partnership project; technical specification group services and system aspects; multimedia broadcast/multicast service; stage 1-release 6,” 3GPP TS 22.146, V6.0.0, 2002–2006.
[2] A. M. C. Correia, J. C. M. Silva, N. M. B. Souto, L. A. C. Silva, A. B. Boal, and A. B. Soares,
“Multi-resolution broadcast/multicast systems for MBMS,” IEEE Trans. Broadcast., vol. 53, no. 1, part 2, pp. 224–234, Mar. 2007.
[3] Y. R. Tsai and Y. C. Chen, “Multilevel Coupling Modulation for Multi-Resolution Multimedia Broadcast/Multicast Service in OFDM Systems,” IEEE Trans. Commun., vol. 59, no. 1, pp. 141–150, Jan. 2011.
[4] J. Cheng, “Coding performance of hybrid ARQ schemes,” IEEE Transactions on
Communications, vol. 54, pp. 1017–1029, 2006.
[5] “Technical specification 3rd generation partnership project; technical specification group radio access network; evolved universal terrestrial radio access (E-UTRA); multiplexing and channel coding; stage 1-release 9,” 3GPP TS 36.212, V9.3.0, 2010–09.
[6] M. B. Pursley and J. M. Shea, “Nonuniform phase-shift-key modulation for multimedia multicast transmission in mobile wireless networks,” IEEE J. Sel. Areas Commun., vol. 17, no. 5, pp. 774–783, May 1999.
[7] M.-S. Alouini, X. Tang, and A. J. Goldsmith, “An adaptive modulation scheme for simultaneous voice and data transmission over fading channels,” IEEE J. Sel. Areas Commun., vol. 17, no. 5, pp. 837–850, May 1999.
[8] M. B. Pursley and J. M. Shea, “Multimedia multicast wireless communications with phase-shift-key modulation and convolutional coding,” IEEE J. Sel. Areas Commun., vol. 17, no. 11, pp. 1999–2010, Nov. 1999.
[9] M. B. Pursley and J. M. Shea, “Adaptive nonuniform phase-shift-key modulation for multimedia traffic in wireless networks,” IEEE J. Sel. Areas Commun., vol. 18, no. 8, pp. 1394–1407, Aug. 2000.
[10] C.-S. Hwang and Y. Kim, “An adaptive modulation for integrated voice/data traffic over Nakagami fading channels,” in Proc. IEEE VTCFall, Sep. 2001, pp. 1649–1652.
[11] C.-S. Hwang and Y. Kim, “An adaptive modulation method for multicast communications of hierarchical data in wireless networks,” in Proc. IEEE ICC, Apr. 2002, vol. 2, pp. 896–900.
[12] M. J. Hossain, P. K. Vitthaladevuni, M.-S. Alouini, and V. K. Bhargava, “Hierarchical modulations for multimedia and multicast transmission over fading channels,” in Proc. IEEE VTC-Spring, Apr. 2003, vol. 4, pp. 2633–2637.
[13] M. J. Hossain, P. K. Vitthaladevuni, M.-S. Alouini, V. K. Bhargava, and A. J. Goldsmith, “Adaptive hierarchical modulation for simultaneous voice and multiclass data transmission over fading channels,” IEEE Trans. Veh. Technol., vol. 55, no. 4, pp. 1181–1194, July 2006.
[14] C. Hellge, S. Mirta, T. Schierl, and T. Wiegand, “Mobile TV with SVC and hierarchical modulation for DVB-H broadcast services,” in Proc. IEEE BMSB, May 2009, pp. 1–5.
[15] J. G. Proakis, Digital Communications, 4th edition. McGraw-Hill, 2001.
[16] P. Frenger, S. Parkvall and E. Dahlman . “Performance comparison of HARQ with Chase combining and incremental redundancy for HSDPA,” IEEE 54th VTC, vol. 3, pp. 1829–1833, 2001.