Vehicle to Vehicle Communications at Suburban Environment using IEEE 802.11af compliant Devices

Vehicle-to-vehicle (V2V) communications where vehicles exchange data such as traffic information had been developed to support the goals of the intelligent transportation system in providing smarter traffic management to lessen road congestions and vehicular accidents. Traditionally, V2V communications operate at ITS band of 5.9 GHz (5.85 - 5.925 GHz) which is more susceptible to attenuation and limited to shorter-range communications. Owing to its better propagation characteristics and wider coverage, V2V communications in the television white space (TVWS) spectrum has been exploited and already been demonstrated. In this paper, V2V communications over TVWS at suburban environment using the IEEE 802.11af-compliant devices were evaluated and characterized in terms of received signal strength and throughput as a function of the separation distance between the two vehicles. The experiments were conducted at a hilly University of San Carlos Talamban Campus located in Cebu City, Philippines which mimic the suburban environment due to buildings, terrains and vegetation present. By utilizing 20 dBm or 100 mW of transmit power with 64-QAM payload modulation and 2/3 coding rate, a maximum of 4.87 Mbps throughput has been measured at -51 dBm of received power. The said data were obtained when the effective speed of the vehicles and the distance between them are 8.68 m/s and 37 m, respectively. Throughput was affected by the packet loss rate and in this study, the packet loss rate of less than 10% was obtained at received signal strength between -88 to -33 dBm in every MCS. In addition, received signal strength and throughput were affected by the non-line of sight communication and multipath propagation influenced by locations, terrains, buildings and other infrastructures present in the area. The results suggested the feasibility of utilizing TVWS in vehicular wireless communications supporting the goals of the intelligent transportation system.