An enhanced MAC protocol to prioritize channel assignment for safety message broadcast in VANET

Spectrum shortage in Vehicular Communications has become an area of concern due to the diverse nature of applications served. Though the allocated 5.9GHz Dedicated Short Range Communication (DSRC) spectrum for vehicular communication is inefficiently utilized, the problem of congestion creates an impression that there is always a scarcity in the spectrum. The criticality of the issue becomes high when a safety message is unable to access the channel or is dropped due to congestion. This paper proposes an approach to prioritize channel access to safety messages through dynamic spectrum sharing. In case, when a safety message finds all the DSRC sub-channels occupied, then any one of the ongoing non-safety messages is switched over to the adjacent 5.8GHz ISM/UNII-3 band allowing the former to access the DSRC band. The proposed approach shows an increased QoS and reduced channel access delay for safety messages compared to the previous works.