Fairness and its Impact on Delay in 802.11 Networks. Gaudoin, O., Sabbatel, G. B., Duda, A., Heusse, M., & Rousseau, F. In Proceedings of the IEEE Global Telecommunications Conference (GLOBECOM'04), volume 5, pages 2967--2973, Dallas, USA, November, 2004.
doi  abstract   bibtex   
We analyze in this paper the fairness of the 802.11 DCF (Distributed Coordination Function) access method. Short- term fairness is an important property of a MAC layer for obtaining short delays. We show that contrary to the common wisdom, a 802.11 cell with two hosts does not exhibit short- term unfairness. Many papers considered 802.11 as short-term unfair by referring to a study of the Wavelan CSMA/CA access method [1]. The confusion comes from the extrapolation of its results to 802.11. Actually, these two access methods are very different: the Wavelan CSMA/CA access method performs exponential backoff when the channel is sensed busy, whereas 802.11 does the same only after a collision. We propose a new fairness index: the number of inter- transmissions that other hosts may perform between two trans- missions of a given host. By means of this index we analyze the fairness of 802.11 for the case of two hosts and derive the probability distribution of the number of inter-transmissions. Our results show that even on the short term time scale the 802.11 DCF access method provides fairness to competing hosts. When compared with Slotted ALOHA, a multiple access randomized protocol with good fairness properties, 802.11 presents even better fairness. To validate the model, we compare the analytical results with experimental histograms obtained via simulations and measurements.
@inproceedings{ gaudoin_fairness_2004,
  address = {Dallas, USA},
  title = {Fairness and its {Impact} on {Delay} in 802.11 {Networks}},
  volume = {5},
  isbn = {0-7803-8794-5},
  doi = {http://dx.doi.org/10.1109/GLOCOM.2004.1378897},
  abstract = {We analyze in this paper the fairness of the 802.11 DCF (Distributed Coordination Function) access method. Short- term fairness is an important property of a MAC layer for obtaining short delays. We show that contrary to the common wisdom, a 802.11 cell with two hosts does not exhibit short- term unfairness. Many papers considered 802.11 as short-term unfair by referring to a study of the Wavelan CSMA/CA access method [1]. The confusion comes from the extrapolation of its results to 802.11. Actually, these two access methods are very different: the Wavelan CSMA/CA access method performs exponential backoff when the channel is sensed busy, whereas 802.11 does the same only after a collision. We propose a new fairness index: the number of inter- transmissions that other hosts may perform between two trans- missions of a given host. By means of this index we analyze the fairness of 802.11 for the case of two hosts and derive the probability distribution of the number of inter-transmissions. Our results show that even on the short term time scale the 802.11 DCF access method provides fairness to competing hosts. When compared with Slotted ALOHA, a multiple access randomized protocol with good fairness properties, 802.11 presents even better fairness. To validate the model, we compare the analytical results with experimental histograms obtained via simulations and measurements.},
  booktitle = {Proceedings of the {IEEE} {Global} {Telecommunications} {Conference} ({GLOBECOM}'04)},
  author = {Gaudoin, Olivier and Berger Sabbatel, Gilles and Duda, Andrzej and Heusse, Martin and Rousseau, Franck},
  month = {November},
  year = {2004},
  pages = {2967--2973}
}
Downloads: 0