The influence of broadcast traffic on IEEE 802.11 DCF networks

The performance of the IEEE 802.11 protocol depends on multiple factors. One of them is related with the relative amounts of broadcast and unicast traffic in the total load due to the coexistence of the different transmission schemes applied to each of these types of traffic. This paper presents an analytical model to compute the 802.11 probability of a successful transmission of a frame and the average transmission delay assuming the presence of both unicast and broadcast traffic. Several realistic issues are addressed, as pre- and post-transmission backoffs, variable frame length and finite MAC buffers. Broadcast frame transmission has a swifter algorithm. When compared to broadcast, unicast frame transmission exhibits a more reliable scheme to avoid a frame from being discarded when it collides, but creates a trade off as it can introduce larger transmission delays. Simulation results are presented and compared to the analytical computations validating the model’s accuracy. Finally, interesting results related with the influence of the amount of broadcast or unicast traffic on the network’s performance for non-saturation and saturation operating zones are discussed for different data transmission rates. This is particularly relevant as most of the ad hoc routing algorithms rely heavily on broadcast.