IEEE 802.16標準針對WiMAX網路定義出無線寬頻存取規範。在IEEE802.16裡，分支台(SS)必須透過使用要求-授權的過程從基地台去取得頻寬。分支台可透過使用兩種機制去達到此目的。其一是單獨輪詢而另一個則是競爭請求。此外，五種不同的服務類型（UGS, ertPS, rtPS, nrtPS, BE）也被定義出來符合不同應用類型的服務品質要求。而其中幾個服務類型可同時支援兩種不同的頻寬要求機制。另一方面，在WiMAX網路裡面頻寬要求分格的數量是有限的。在不同的網路環境使用不同的頻寬要求機制會影響頻寬要求分格的效能利用率。為了得到良好的頻寬要求分格效能利用率，在不同的環境選用適當的頻寬請求機制是相當重要的。因此針對WiMAX網路，我們提出一個新的演算法去挑選頻寬要求機制用來改善頻寬要求分格的效能利用率。最後我們的模擬結果展現我們提出的演算法比較其他的頻寬請求機制確實改善頻寬要求分格的效能利用率。

IEEE 802.16 standards define the broadband wireless access specification for WiMAX. In IEEE 802.16, SSs must use the process of request-grant to get the bandwidth from the BS. SSs can use two mechanisms to do the process. One is unicast polling and the other is contention request. In addition, five service types, UGS, ertPS, rtPS, nrtPS and BE, are defined to meet different QoS requirements of a variety of applications. Some of service types can use both two bandwidth request mechanisms to send bandwidth request. In addition, the number of BW-request slots is limited in WiMAX network. Using the different mechanisms to request bandwidth under different network conditions would affect the efficiency of BW-request slots. So, choosing the suitable bandwidth request mechanism in different situations is so important for getting good efficiency of BW-request slots. As a result, we propose a new algorithm to decide which mechanism shall be used for improving the efficiency of BW-request slots in WiMAX. Our simulation results show that our proposed algorithm improves the efficiency of BW-request slots in WiMAX networks when compared with other bandwidth request algorithms.

[1] IEEE Standard for Local and Metropolitan Area Networks - Part 16: Air Interface for Fixed Broadband Wireless Access Systems, IEEE Std. 802.16d-2004.
[2] IEEE Standard for Local and Metropolitan Area Networks - Part 16: Air Interface for Fixed and mobile Broadband Wireless Access Systems, IEEE Std. 802.16e-2005.
[3] G. Chu, D. Wang, S. Mei, C. ”A QoS architecture for the MAC protocol of IEEE 802.16 BWA system”, IEEE International Conference on Communications, Page(s): 435 - 439, vol. 1, 29 June-1 July 2002.
[4] S. Oh, J. Kim, “The analysis of the optimal contention period for broadband wireless access network”, PerCom 2005 Workshops. Third IEEE International Conference on, Page(s):7215- 219, 8-12 March 2005. 11-13.
[5] W. Lu, W. Jia, W. Du, and L. Lin, “A Base Station Coordinated Contention Resolution for IEEE 802.16 PMP networks”, International Conference on Ubiquitous Intelligence and Computing, pp. 605-614, Sept. 2006.
[6] Scalable Network Technologies, “Network Simulator - QualNet”, http://www.scalable-networks.com/products/developer/
[7] P. P., Berry, R., P, T.; K, A.; “Content-Aware Resource Allocation and Packet Scheduling for Video Transmission over Wireless Networks,” IEEE Journal on Selected Areas in Communications, Volume 25, Issue 4, Page(s):749 – 759, May 2007.
[8] Kun Yang; Shumao Ou; Hsiao-Hwa Chen; Jianghua He; “A Multihop Peer-Communication Protocol With Fairness Guarantee for IEEE 802.16-Based Vehicular Networks,” IEEE Transactions on Vehicular Technology, Volume 56, Issue 6, Part 1, Page(s):3358 – 3370, Nov. 2007.
[9] Jianfeng Chen, Wenhua Jiao, Hongxi Wang, “A Service Flow Management Strategy for IEEE 802.16 Broadband Wireless Access Systems in TDD Mode,” ICC 2005, Page(s): 3422-3426, 16-20 May 2005.
[10] Safa, Haidar; Artail, Hassan; Karam, Marcel; Soudah, Rawan; Khayat, Samar; “New Scheduling Architecture for IEEE 802.16 Wireless Metropolitan Area Network,” IEEE/ACS International Conference on Computer Systems and Applications, 2007, Page(s): 203-210, 13-16 May 2007.
[11] Mukul, Singh, Jayaram, Das, Sreenivasulu, Vinay, Ramamoorthy,“An Adaptive Bandwidth Request Mechanism for QoS Enhancement in WiMax Real Time Communication” Wireless and Optical Communications Networks, 2006 IFIP International Conference on, page(s): 5 pp. 11-13 April 2006.
[12] Qingwen Liu; Xin Wang; Giannakis, G.B. “A cross-layer scheduling algorithm with QoS support in wireless networks” Vehicular Technology, IEEE Transactions on Volume 55, Issue 3, May 2006 Page(s):839 – 847
[13] Vaughan-Nichols, S.J. “Achieving wireless broadband with WiMax” Computer Volume 37, Issue 6, June 2004 Page(s): 10 – 13
[14] Kitti Wongthavarawat *, Aura Ganz “Packet scheduling for QoS support in IEEE 802.16 broadband wireless access systems” International Journal of Communication Systems, Volume 16 Issue 1, 18 Feb 2003, Pages 81 – 96
[15] Jayaparvathy, R. Sureshkumar, G. Kanakasabapathy, P. “Performance evaluation of scheduling schemes for fixed broadband wireless access systems” Networks, 2005. Jointly held with the 2005 IEEE 7th Malaysia International Conference on Communication., 2005 13th IEEE International Conference on
[16] Sun, J. Yanling Yao Hongfei Zhu. “Quality of Service Scheduling for 802.16 Broadband Wireless Access Systems” Vehicular Technology Conference, 2006. VTC 2006-Spring. IEEE 63rd 7-10 May 2006 Volume: 3 page(s): 1221-1225
[17] Bo Rong, Yi. Qian. Hsiao-Hwa Chen “Adaptive power allocation and call admission control in multiservice WiMAX access networks” Wireless Communications, IEEE Feb. 2007 Volume: 14, page(s): 14-19
[18] Han, Y.S. Jing Deng Haas, Z.J. “Analyzing multi-channel medium access control schemes with ALOHA reservation” Wireless Communications, IEEE Transactions on, Aug. 2006. Volume: 5, Issue: 8, page(s): 2143-2152.
[19] Jing Deng Han, Y.S. Haas, Z.J. “Analyzing split channel medium access control schemes” Wireless Communications, IEEE Transactions on, May 2006. Volume: 5, Issue: 5, page(s): 967- 971
[20] Ghazal, S.; Aoul, Y.H.; Ben Othman, J.; Nait-Abdesselam, F. “Applying a self-configuring admission control algorithm in a new QoS architecture for IEEE 802.16 networks” Computers and Communications, 2008. IEEE Symposium on 6-9 July 2008 Page(s):1023 – 1028
[21] D. Cho, J. Song, M. Kim, K. Han, N, F. “Performance analysis of the IEEE 802.16 wireless metropolitan area network” Distributed Frameworks for Multimedia Applications. First International Conference on, 2005
[22] Lidong Lin Bo Han Weijia Jia. “Modeling and Performance Analysis of Initial Connection in IEEE 802.16 PMP Networks” Multimedia and Expo, 2006 IEEE International Conference on, 9-12 July 2006, page(s): 609-612.
[23] Jianhua He Guild, K. Kun Yang Hsiao-Hwa Chen. “Modeling Contention Based Bandwidth Request Scheme for IEEE 802.16 Networks” Communications Letters, IEEE, August 2007, Volume:11,Issue: 8page(s): 689-700
[24] Chun Nie Venkatachalam, M. Xiangying Yang. “Adaptive Polling Service for Next-Generation IEEE 802.16 WiMAX Networks” Global Telecommunications Conference, 2007. GLOBECOM '07. IEEE, Nov. 2007 page(s): 4754-4758
[25] Olli Alanen. “Multicast polling and efficient voip connections in ieee 802.16 networks” Proceedings of the 10th ACM Symposium on Modeling, analysis, and simulation of wireless and mobile systems, 2007. page(s): 289 - 295