Passive Cooperative Collision Warning (PCCW) MAC designs for reliable vehicular safety messaging

This paper presents – Passive Cooperative Collision Warning (PCCW), and enhanced-PCCW (EPCCW) protocol designs for safety message reception reliability improvement in Dedicated Short Range Communications (DSRC). PCCW and EPCCW employ a cooperative warning scheme for reduction of collisions, without increasing packet traffic. EPCCW utilizes the physical layer (PHY) properties to create sub-slots for the purpose of further increasing reliability by both avoiding and minimizing probability of collision at slots that would nominally fail. Full analytical derivation of the relative reliability and delay performances for both PCCW and EPCCW protocols is provided. An accurate and complete simulation model is used, which combines an accurate DSRC PHY, MAC and federated mobility model designed using the Simulation of Urban MObility (SUMO) model. Analytical and simulation results agree and show that PCCW and EPCCW protocols significantly improve reliability performance relative to the leading safety messaging protocols. Under high collision scenarios and at optimal number of repetitions, an improvement of up to 40% in reliability is observed, and up to 80% of improvement is achieved at higher load. Improvement in average timeslots delay is also observed that is well within acceptable delay threshold. Thorough simulation results of the proposed protocols are presented under varying message range, coding rates, modulation schemes, channel models, vehicular densities, safety message lifetimes, and transmission frequencies.