Proportional fair resource allocation in vehicle-to-infrastructure networks for drive-thru Internet applications

IEEE 802.11p, also known as wireless access in vehicular environment (WAVE), defines amendments to IEEE 802.11 to support Intelligent Transportation Systems applications. In a vehicle-to-infrastructure (V2I) network, the same road side unit (RSU) will be shared by more than one vehicle. When vehicles within the coverage of the same RSU use distinct data rates for transmission, an unfairness problem occurs among them, popularly known as performance anomaly. Essentially, the vehicle with the lowest data rate slows all other vehicles down to its rate, resulting in poor use of the wireless medium and reduced performance for all vehicles. This problem is caused by the 802.11 DCF protocol which provides unfair channel time allocation for vehicles with different data rates. In addition to the performance anomaly caused by the multiple data rates, vehicles in a multi-lane network (where lane i is being used by vehicles of mean velocity @m"v"""i), suffer from an access unfairness problem as well, due to the fact that vehicles having different mean velocities get unequal chances for channel access. Both these unfairness problems can significantly degrade the network performance. In this paper, we investigate the use of proportional fairness (PF) as the basis of resource allocation in a multi-rate multi-lane V2I network for drive-thru Internet applications. In this case, RSU is shared by vehicles that transmit at distinct data rates and moving with different mean velocities. We use the notion of PF resource allocation to resolve the unfairness problems and to improve the aggregate data transferred in the network. We find analytical expressions for the optimal setting of CW"m"i"n values to ensure proportional fair allocation in both single-lane as well as multi-lane multi-rate V2I networks. Through analytical and simulation results, we establish that the notion of proportional fair utility criterion can improve the aggregate data transferred as compared to the default CW"m"i"n setting.