在這篇論文，我們提出一個動態服務差異的機制去改進在IEEE 802.11 ad-hoc無線網路的服務品質(QoS)。我們所提出一個稱為DADB (Dynamic Age-Depend Backoff)的機制，是由ADB機制所改進的。本機制是希望能夠改善ADB機制在網路負載很重的情形。本篇的改進主要在於：能夠動態調整高優先權Traffic Category (TC)的persistent factor的大小，此動態的調整希望能夠同時考量到訊框的等待時間以及網路的狀態。

我們藉由模擬來比較DADB與ADB兩機制的效能。模擬的結果顯示：我們的方法與ADB機制有一樣的優點，可以改善無線網路中訊框的Delay與Jitter。特別在網路負載很大的狀態之下，DADB機制更能夠比ADB機制優越。我們的機制相對於ADB機制可以改善高優先權TC的效能以及減少無線網路中碰撞的機率。

This paper describes an adaptive service differentiation scheme for QoS enhancement in IEEE 802.11 wireless ad-hoc networks. Our approach is called Dynamic Age-Dependent Backoff (DADB) which is derived from the ADB scheme and aims to improve the ADB scheme when the traffic load is high. Improvement of our scheme are provisioned by adjusting the size of the persistent factor of high traffic categories taking into account both age time of frame and network conditions.


We evaluate the performance of DADB through simulations and compare it with the ADB scheme proposed in the 802.11e. Results show that our scheme DADB is similar to ADB scheme which can improve the delay and jitter in wireless network. Especially at high traffic load conditions, DADB outperforms the basic ADB: our scheme improve the throughput of high priority traffic category and decrease collision rate when traffic load is heavy.

第一章 簡介........................................................1
第二章 背景知識與文獻探討..........................................4
2-1 IEEE 802.11: 無線區域網路標準................................4
2-2 針對IEEE 802.11的DCF的研究與改進..........................10
2-2-1 針對媒介存取層改進仲裁的方法...........................10
2-2-2 改進IEEE 802.11無線網路CSMA/CA機制的運作參數...........13
2-3 IEEE 802.11e標準...........................................16
2-4 針對EDCF的改進與研究......................................18
第三章 所提出的方法...............................................22
第四章 模擬.......................................................27
第五章 結論.......................................................41
第六章 參考文獻...................................................42

[1] IEEE 802.11 WG, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specification, Standard, IEEE, Aug. 1999.
[2] F. Micó, P. Cuenca, and L. Orozco-Barbosa, "QoS in IEEE 802.11 wireless LAN: current research activities," IEEE Canadian Conference on Electrical and Computer Engineering, vol. 1, pp 447-452, May 2004
[3] Hua Zhu, Ming Li, Imrich Chlamtac, and B. Prabhakaran, “A Survey of Quality of Service in IEEE 802.11 Networks,” IEEE WIRELESS COMMUNICATIONS, AUGUST 2004, pp. 6-14.
[4] IEEE 802.11e WG, Draft Supplement to Part 11: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications: Medium Access Control (MAC) Enhancements for Quality of Service (QoS), IEEE Std 802.11e/D3.3.2, Nov. 2002.
[5] P. Chevillat, J. Jelitto, A. N. Barreto, and H. L. Truong, “A dynamic link adaptation algorithm for IEEE 802.11a wireless LANs,” in: IEEE International Conference on Communications (ICC), 2003, pp. 1141-1145.
[6] A. Banchs, X. Perez, M. Radimirsch, and H. Stuttgen, “Service Differentiation Extensions for Elastic and Real-Time Traffic in 802.11 Wireless LAN,” IEEE Workshop on High Performance Switching and Routing, May 2001, pp. 245-249.
[7] W. T. Chen, B. B. Jian, and S. C. Lo, “An Adaptive Retransmission Scheme with QoS Support for the IEEE 802.11 MAC Enhancement,” IEEE 55th Vehicular Technology Conference, VTC/Spring, Vol. 1, pp. 70 -74, 2002.
[8] Lillykutty Jacob, Li Xiang, and Zhou Luying, “A MAC Protocol with QoS Guarantees for Real-Time Traffics in Wireless LANs,” Fourth International Conference on Information, Communications & Signal Processing (ICICS-PCM 2003), Singapore, December 2003.
[9] J. L. Sobrinho, and A. S. Krishnakumar, “Real-Time Traffic over the IEEE 802.11 Medium Access Control Layer,” Bell Labs Technical Journal, vol. 1, no. 2, pp. 172-187, Autumn 1996.
[10] J. L. Sobrinho, and A. S. Krishnakumar, “Quality-of-Service in Ad Hoc Carrier Sense Multiple Access Networks,” IEEE J. Selected Areas in Comm., vol. 17, no. 8, pp. 1353-1368, Aug. 1999.
[11] J. P. Sheu, C. H. Liu, S. L. Wu, and Y. C. Tseng, “A priority MAC protocol to support real-time traffic in ad hoc networks,” Wireless Networks, vol.10, no.1, pp.61-69, 2004/01.
[12] R. O. Baldwin, N. J. Davis IV, and S. F. Midkiff, “A Real-time Medium Access Control Protocol for ad hoc Wireless Local Area Networks,” ACM Mobile Computing and Communications Review, April 1999, vol. 3, No. 2, pp. 20-27.
[13] S. T. Sheu and T. F. Sheu, “A bandwidth allocation / sharing / extension protocol for multimedia over IEEE 802.11 ad hoc wireless LANs,” IEEE Journal on Selected Areas in Communications, vol. 19, no. 10, pp. 2065-2080, Oct. 2001.
[14] J. Deng and R. S. Chang, “A Priority Scheme for IEEE 802.11 DCF Access Method,” IEICE Trans. Commun. , vol. 82-B, no. 1, Jan. 1999.
[15] I. Aad and C. Castelluccia, “Differentiation Mechanisms for IEEE 802.11,“ in Proc. IEEE INFOCOM’01, April 2001
[16] A. T. Veres, M. Barry Campbell, and L. H. Sun, “Supporting service differentiation in wireless packet networks using distributed control,” IEEE Journal on Selected Areas in Communications, Oct. 2001, vol. 19, no. 10, pp. 2081 -2093.
[17] M. Barry, A. T. Campbell, and A. Veres, “Distributed control algorithms for service differentiation in wireless packet networks,” in Proceedings of IEEE INFOCOM, Anchorage, AK, Apr. 2001, pp. 582–590.
[18] M. Benveniste, “Tiered Contention Multiple Access' (TCMA), A QoS-Based Distributed MAC Protocol,” Personal, indoor and Mobile Radio Communications, The 13th IEEE International Symposium, 2002
[19] G. Bianchi, L. Fratta, and M. Olivefi, "Performance evaluation and enhancement of the CSMA/CA MAC protocol for 802.11 wireless LANs," in Proc. PIMRC, Taipei, Taiwan, Oct. 1996, pp. 392-3.96.
[20] G. Bianchi, “Performance Analysis of the IEEE 802.11 Distributed Coordination Function,” IEEE Journal on Selected Areas in Communications, vol. 18, no. 3, pp. 535-547, Mar. 2000.
[21] F. Cali, M. Conti, and E. Gregori, “IEEE 802.11Wireless LAN: Capacity Analysis and Protocol Enhancement,” in Proc. IEEE INFOCOM’98, March 1998.
[22] F. Cali, M. Conti, and E. Gregori, “Dynamic Tuning of the IEEE 802.11 Protocol to Achieve a Theoretical Throughput Limit,” IEEE/ACM Trans. on Networking, December 2000, Vol. 8, No. 6, pp. 785–799.
[23] F. Cali, M. Conti, and E. Gregori, “IEEE 802.11 Protocol: Design and Performance Evaluation of an Adaptive Backoff Mechanism,” IEEE JSAC, September 2000, Vol. 18, No. 9, pp. 1774–1786.
[24] L. Gannoune, and S. Robert,“Dynamic tuning of the contention window minimum (CWmin) for enhanced service differentiation in IEEE 802.11 wireless ad-hoc networks,” Proc. IEEE PIMRC, Barcelona, Spain, 2004/09.
[25] Jun Zhao, Zihua Guo, Qian Zhang, and Wenwu Zhu, “Distributed MAC adaptation for WLAN QoS differentiation,” GLOBECOM 2003 - IEEE Global Telecommunications Conference, vol. 22, no. 1, Dec 2003 pp. 3442-3446
[26] An-Tai Lin, and Shie-Jue Lee, “A modified Distributed Coordination Function for real-time traffic in IEEE 802.11 wireless LAN,” AINA 2003, March 2003, pp. 794 - 797
[27] I. Aad and C. Castelluccia, “Priority in WLANs,” computer networks, vol. 41, member 4, pp505-526, March 2003
[28] Y. M. Ghamri Doudane, R. Naja, G. Pujolle and S. Tohme, "P3-DCF: Service Differentiation in IEEE 802.11 WLANs using Per-Packet Priorities," IEEE Semi-annual Vehicular Technology Conference, VTC 2003, Orlando, USA, 4-9 October, 2003
[29] L. Romdhani, Qiang Ni, and T. Turletti, “Adaptive EDCF: enhanced service differentiation for IEEE 802.11 wireless ad-hoc networks,” IEEE Wireless Communications and Networking, vol. 2, pp. 1373 – 1378, March 2003.
[30] H. Zhu, G. Cao, A. Yener and A. D. Mathias “EDCF-DM: A Novel Enhanced Distributed Coordination Function for Wireless Ad Hoc Networks,” IEEE ICC, Paris, France, June 2004.
[31] Xin Wang, Qianli Zhang, and Xing Li, “Protocol enhancement for IEEE 802.11e EDCF,” Networks, Proceedings. 12th IEEE International Conference, Nov. 2004 vol.1 pp. 80 - 84
[32] G. W. Wong, and R. W. Donaldson, “Improving the QoS performance of EDCF in IEEE 802.11e wireless LANs,” Communications, Computers and signal Processing, Aug. 2003 vol.1 pp. 392 – 396
[33] Hiroyuki Yamada, Hiroyuki Morikawa and Tomonori Aoyama, “Decentralized Control Mechanism Suppressing Delay Fluctuation in Wireless LANs,” IEEE VTC2003-Fall, October 2003.
[34] The Network Simulator - ns-2. http://www.isi.edu/nsnam/ns/.
[35] Fedora Project. http://fedora.redhat.com/
[36] An IEEE 802.11e EDCF and CFB Simulation Model for ns-2. http://www.tkn.tu-berlin.de/research/802.11e_ns2/