A Geometric Backoff Time Distribution of IEEE 802.11 DCF: An Analytical Study

Youssef Dehbi, Hafssa Benaboud, Noufissa Mikou

Abstract


Today’s networks, including WLANs, transport
different classes of service. A service differentiation is then
essential to provide QoS. However, IEEE 802.11 for WLANs was
primarily designed for best effort traffic and did not provide QoS
specifications. IEEE 802.11e MAC has been then described to
support QoS in WLAN. In this paper, we propose a new scheme
for service differentiation which is based on the 802.11 standard
and requires minor modifications. In fact, we act on DCF which
uses the backoff procedure to solve contention in WLANs.
For this scheme, we use, instead of the uniform distribution,
a geometric distribution for random backoff time selection.
Using a multi-class system, we propose three parametrizations
of the geometric distribution which imply different dynamic
differentiation modes and we provide an analytical study, using
a Markov chain model, to compare our differentiation modes.
We discuss our numerical results which give the performances
evaluation of the proposed mechanism in term of throughput
and delay.

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International Journal of Communication Networks and Information Security (IJCNIS)          ISSN: 2076-0930 (Print)           ISSN: 2073-607X (Online)