Clustering based cognitive MAC protocol for channel allocation to prioritize safety message dissemination in vehicular ad-hoc network

With the rising demand for vehicular networking through wireless communication for safety as well as non-safety applications, the urge to provide efficient bandwidth utilization along with reliable data delivery is rising significantly. Apparently, various communication services and applications are falling short of radio frequencies to be assigned to them. In addition to that, the IEEE 802.11p standard to enable wireless access in vehicular communication on DSRC frequencies is known to yield insufficient spectrum for reliable exchange of information over congested channels. To address these issues, this paper presents a clustering based cognitive MAC (CCMAC) protocol which allows dynamic allocation of channels in the band adjacent to the DSRC band, known as 5.8 GHz U-NII-3/ISM band. The novelty of CCMAC lies in exploiting the free unlicensed band thereby, eliminating the concept of primary and secondary user. For this purpose, we introduce mobility aware clustering based channel allocation protocol that proactively monitors the channel sensing outcomes. Using these results, vehicles access information about spectrum availability prior to transmission. The protocol ensures immediate channel access to safety messages within DSRC band at the cost of non-safety messages which are switched to U-NII-3/ISM band when falling short of channel access in the DSRC band. This not only results in alleviating access delay but also renders efficient channel utilization. The results demonstrate the effectiveness of the CCMAC protocol in allocating real-time and scalable spectral resources, fast and efficient reception of safety messages compared to existing schemes, and in alleviating the operation of safety application based services in VANET.