Analysis of SFR´s impaction on delay time based DMMAC for VANETs

Vehicular Ad-hoc NETworks (VANETs) are networks rely on short-range communication technology to facilitate Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) communications. Various Media Access Control (MAC) protocols are proposed by recent researches to support efficient and reliable wireless access for VANETs. Particularly, Dedicated Multichannel MAC (DMMAC) distinguished itself as a collision-free and delay-bounded MAC protocol with the advantage of adapting its framework to different traffic density. Since MAC protocol is critical for VANETs, a detail analysis of its performance is clearly required to provide references for future deployment. In this paper, a novel analytical model using probabilistic method is proposed to evaluate the time-delay performance of DMMAC through a function of Slots For Reservation (SFR) value and vehicular nodes number within two-hop neighborhood. This model supplies a new approach to optimize the value of SFR to DMMAC protocol according to the network requirements such as the traffic density. Simulation results carried out in Matlab are consistent with theoretical analyses, which confirms the correctness of the proposed analytical model. Numerical relationship can be derived from the simulation results that the delay time is adversely influenced when the value of SFR or the density of traffic increases, while the differentiations brought by different SFRs become minor when encountering a denser traffic.