On the use of OFDMA for next generation vehicular ad hoc networks

Vehicular ad hoc networks (VANETs) based on IEEE 802.11p are moving new safety and traffic applications beyond the present limitations given by infrastructures. However, due to the high variability in time and position of nodes, the medium access control layer of IEEE 802.11p, which is based on carrier sensing multiple access with collision avoidance (CSMA/CA), could lead to severe performance degradation in terms of delivery delay and delivery ratio as the node density increases. Because of its higher efficiency, we propose the use of orthogonal frequency division multiple access (OFDMA) as access technique in VANETs, discussing and evaluating i) its feasibility, ii) the challenges posed by the distributed allocation of resources, and iii) its performance in terms of resource allocation efficiency (specifically, delivery rate and delivery delay) when compared to CSMA/CA. Results, obtained by means of simulations that jointly take into account realistic road maps, vehicular traffic, and the whole network architecture from the application down to the physical layer, show that OFDMA allows up to four times higher delivery rate and that it also guarantees lower delivery delay in heavy loaded network conditions.