Open Access

CSMA/CCA: A Modified CSMA/CA Protocol Mitigating the Fairness Problem for IEEE 802.11 DCF

EURASIP Journal on Wireless Communications and Networking20062006:039604

DOI: 10.1155/WCN/2006/39604

Received: 15 August 2005

Accepted: 22 December 2005

Published: 16 March 2006


Carrier sense multiple access with collision avoidance (CSMA/CA) has been adopted by the IEEE 802.11 standards for wireless local area networks (WLANs). Using a distributed coordination function (DCF), the CSMA/CA protocol reduces collisions and improves the overall throughput. To mitigate fairness issues arising with CSMA/CA, we develop a modified version that we term CSMA with copying collision avoidance (CSMA/CCA). A station in CSMA/CCA contends for the shared wireless medium by employing a binary exponential backoff similar to CSMA/CA. Different from CSMA/CA, CSMA/CCA copies the contention window (CW) size piggybacked in the MAC header of an overheard data frame within its basic service set (BSS) and updates its backoff counter according to the new CW size. Simulations carried out in several WLAN configurations illustrate that CSMA/CCA improves fairness relative to CSMA/CA and offers considerable advantages for deployment in the 802.11-standard-based WLANs.


Authors’ Affiliations

Department of Electrical and Computer Engineering, University of Minnesota


  1. IEEE 802.11 WG, Wireless LAN medium access control (MAC) and physical layer (PHY) specifications: higher speed physical layer (PHY) extension in the 2.4GHz band, IEEE Std. 802.11b/D5.0, April 1999
  2. IEEE 802.11 WG, Wireless LAN medium access control (MAC) and physical layer (PHY) specifications: higher speed physical layer (PHY) extension in the 5GHz band, IEEE Std. 802.11a/D5.0, April 1999
  3. IEEE 802.11 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 802.11e/D3.3.2, November 2002
  4. Kleinrock L, Tobagi FA: Packet switching in radio channels: part I—carrier sense multiple-access modes and their throughput-delay characteristics. IEEE Transactions on Communications 1975, 23: 1400–1416. 10.1109/TCOM.1975.1092768View ArticleMATHGoogle Scholar
  5. Bianchi G: Performance analysis of the IEEE 802.11 distributed coordination function. IEEE Journal on Selected Areas in Communications 2000,18(3):535–547. 10.1109/49.840210View ArticleGoogle Scholar
  6. Cali F, Conti M, Gregori E: IEEE 802.11 wireless LAN: capacity analysis and protocol enhancement. Proceedings of IEEE 17th Annual Joint Conference of the IEEE Computer and Communications Societies (INFOCOM '98), March-April 1998, San Francisco, Calif, USA 1: 142–149.Google Scholar
  7. Ozugur T: Optimal MAC-layer fairness in 802.11 networks. Proceedings of IEEE International Conference on Communications (ICC '02), April-May 2002, New York, NY, USA 2: 675–681.View ArticleGoogle Scholar
  8. Tinnirello I, Choi S: Temporal fairness provisioning in multi-rate contention-based 802.11e WLANs. Proceedings of 6th IEEE International Symposium on a World of Wireless Mobile and Multimedia Networks (WoWMoM '05), June 2005, Taormina, Italy 220–230.View ArticleGoogle Scholar
  9. Ozugur T, Naghshineh M, Kermani P, Olsen CM, Rezvani B, Copeland JA: Balanced media access methods for wireless networks. Proceedings of 4th Annual ACM/IEEE International Conference on Mobile Computing and Networking (MobiCom '98), October 1998, Dallas, Tex, USA 21–32.View ArticleGoogle Scholar
  10. Wang C, Li B, Li L: A new collision resolution mechanism to enhance the performance of IEEE 802.11 DCF. IEEE Transactions on Vehicular Technology 2004,53(4):1235–1246. 10.1109/TVT.2004.830951View ArticleGoogle Scholar
  11. Cheung EM, Wong GW, Donaldson RW: Probabilistic contention window control in 802.11 WLANs. Proceedings of IEEE Pacific Rim Conference on Communications, Computers and Signal Processing (PACRIM '03), August 2003, Victoria, BC, Canada 2: 654–658.Google Scholar
  12. Kwon Y, Fang Y, Latchman H: Design of MAC protocols with fast collision resolution for wireless local area networks. IEEE Transactions on Wireless Communications 2004,3(3):793–807. 10.1109/TWC.2004.827731View ArticleGoogle Scholar
  13. Golestani SJ: A self-clocked fair queueing scheme for broadband applications. Proceedings of IEEE 13th Networking for Global Communications (INFOCOM '94), June 1994, Toronto, Ontario, Canada 2: 636–646.Google Scholar
  14. Koksal CE, Kassab H, Balakrishnan H: An analysis of short-term fairness in wireless media access protocols. Proceedings of International Conference on Measurement and Modeling of Computer Systems (SIGMETRICS '00), June 2000, Santa Clara, Calif, USA 118–119.Google Scholar
  15. Fang Z, Bensaou B, Wang Y: Performance evaluation of a fair backoff algorithm for IEEE 802.11 DFWMAC. Proceedings of the 3rd ACM International Symposium on Mobile Ad Hoc Networking and Computing (MobiHoc '02), June 2002, Lausanne, Switzerland 48–57.View ArticleGoogle Scholar
  16. Karn P: MACA—a new channel access method for packet radio. Proceedings of the 9th ARRL/CRRL Amateur Radio Computer Networking Conference, September 1990, Ontario, Canada 134–140.Google Scholar
  17. Bharghavan V, Demers A, Shenker S, Zhang L: MACAW: a media access protocol for wireless LAN's. Proceedings of the Conference on Communications Architectures, Protocols and Applications (SIGCOMM '94), August-September 1994, London, UK 212–225.View ArticleGoogle Scholar
  18. Pahlavan K, Krishnamurthy P: Principles of Wireless Networks: A Unified Approach. Prentice-Hall, Upper Saddle River, NJ, USA; 2002.Google Scholar
  19. Mangold S, Choi S, May P, Hiertz G: IEEE 802.11e—fair resource sharing between overlapping basic service sets. Proceedings of the 13th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC '02), September 2002, Lisboa, Portugal 1: 166–171.
  20. Xiao Y, Li H: Voice and video transmissions with global data parameter control for the IEEE 802.11e enhance distributed channel access. IEEE Transactions on Parallel and Distributed Systems 2004,15(11):1041–1053. 10.1109/TPDS.2004.72MathSciNetView ArticleGoogle Scholar


© X.Wang and G. B. Giannakis 2006

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.