Modelling Delay on IEEE 802.11 MAC Protocol for Unicast and Broadcast Non-saturated Traffic


Rodolfo Oliveira, Luis Bernardo, Paulo Pinto

Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, P-2829-516 Caparica, Portugal
Email: rado(@), lflb(@), pfp(@)

Abstract:        The existing models for IEEE 802.11 DCF networks only consider unicast frames, ignoring the existence of broadcast traffic. In a real scenario, the stations are most of the times non-saturated and unicast and broadcast frames exist. These specific characteristics influence the service time which consequently affects the queue behaviour. In this paper, we model the total frame’s delay for IEEE 802.11 DCF networks in presence of both unicast and broadcast traffic. Our theoretical analysis proposes a model able to compute the time between the instant when a new frame is inserted on the transmission queue and the instant when its transmission finishes. The time needed to serve a frame (service time) is formally deduced from the IEEE 802.11 transmission procedure, conceptually using the view of one network’s node. We use an M/M/1/K queue model in order to model each frame’s queueing delay. We validate the total frame’s delay using several simulations and present some results. These are analysed for different scenarios of broadcast/unicast network loads and different number of nodes.

To appear in:

IEEE Wireless Communications & Networking Conference (WCNC 2007), Hong Kong, 11-15 March, 2007