Reliable MAC layer designs for vehicular networks

This paper discusses mobile hidden station (MHS) problem which is a significant source of packet collisions in medium access control (MAC) protocols of vehicular networks due to relatively high node speeds. MHS problem occurs when mobile stations that are not present in the channel reservation period enter and disturb the existing communications. We present effect of MHS problem using Markov model of carrier sense multiple access with collision avoidance (CSMA/CA). Then we present how MHS affects the repetition broadcast protocols using analytical analysis results. Finally, protocols that mitigate effect of MHS at MAC layer for both infotaintment communication and safety broadcast messaging are presented. MAC protocol for infotaintment is Enhanced Sliding Frame Reservation Aloha (ESFRA) and for safety broadcast messaging is Passive Cooperative Collision Warning (PCCW). With these protocols, it is verified that effect of MHS is significantly reduced, which result in lower delay and significant improvement in reliability. Both analytical analysis and simulation results agree.