On the Asymptotic Validity of the Decoupling Assumption for Analyzing 802.11 MAC Protocol
2012 (English)In: IEEE Transactions on Information Theory, ISSN 0018-9448, Vol. 58, no 11, 6879-6893 p.Article in journal (Refereed) Published
Performance evaluation of the 802.11 MAC protocol is classically based on the decoupling assumption, which hypothesizes that the backoff processes at different nodes are independent. This decoupling assumption results from mean field convergence and is generally true in transient regime in the asymptotic sense (when the number of wireless nodes tends to infinity), but, contrary to widespread belief, may not necessarily hold in stationary regime. The issue is often related with the existence and uniqueness of a solution to a fixed point equation; however, it was also recently shown that this condition is not sufficient; in contrast, a sufficient condition is a global stability property of the associated ordinary differential equation. In this paper, we give a simple condition that establishes the asymptotic validity of the decoupling assumption for the homogeneous case (all nodes have the same parameters). We also discuss the heterogeneous and the differentiated service cases and formulate a new ordinary differential equation. We show that the uniqueness of a solution to the associated fixed point equation is not sufficient; we exhibit one case where the fixed point equation has a unique solution but the decoupling assumption is not valid in the asymptotic sense in stationary regime.
Place, publisher, year, edition, pages
IEEE Press, 2012. Vol. 58, no 11, 6879-6893 p.
802.11, Decoupling assumption, fixed point equation (FPE), mean field theory, ordinary differential equation (ODE)
IdentifiersURN: urn:nbn:se:kth:diva-104672DOI: 10.1109/TIT.2012.2208582ISI: 000310156500014ScopusID: 2-s2.0-84867750236OAI: oai:DiVA.org:kth-104672DiVA: diva2:566603
FunderICT - The Next Generation
QC 201212112012-11-122012-11-082013-04-11Bibliographically approved