Analytical modelling in 802.11 ad hoc networks

This paper tries to bring together the physical model and protocol model that have been used to characterize interference relationship in an 802.11 ad hoc network. The physical model (known as the SNR model) is generally considered as a reference model for the physical layer behaviour but its application in wireless ad hoc networks is restricted by its complication. On the other hand, the protocol model (known as the unified disk graph) is straightforward but its validity is doubtful. We propose an analytical model for 802.11 ad hoc wireless networks where both the physical and protocol models are improved and modelled accurately by taking into accounts all emitters in the network and circumventing simplistic assumptions where communications are supposed to systematically fail if non-intended emitters fall in proximity of a receiver node. Our model consists in replacing a finite number of nodes by an equivalent continuum – characterized by a density of nodes – and disseminated in the network according to some distribution function. The key feature of the proposed model is that it permits taking into account the effect of interference, the CSMA/CA mechanism and radio propagation aspects in an easy and clear-cut way. All assumptions in the model are assessed with simulation results. Closed form formula of the signal to noise ratio and the throughput capacity per node will be given, corroborated by extensive simulation results in ns-2.