Performance Analysis Of Autonomous Vehicle Based Multiplatooning Communication System Model

The fast growth of metropolitan areas has caused an increasing influx of vehicular traffic to and from big cities.As a result,urban roads and highways are plagued by traffic congestions and road crashes,resulting in serious commuter time waste and economic losses.Platooning has been identified as a promising vehicle traffic management strategy to reduce traffic conges-tions,increase vehicle traffic capacity,improve driving safety,and reduce fuel consumption and exhaust emissions.For the practical applications of platoon,platoon control is always one of the key issues,which aims at maintaining a constant speed and inter-vehicle spacing within the platoon.Existing researches indicate that inter-vehicle communications are important to pla-toon control.First of all,enabling the prompt exchange of vehicle's velocity and acceleration information within a platoon through wireless communications is one of the important factors to maintain the string stability,wherein,the platoon control system needs to aggregate vehicles'sensing,velocity and acceleration information to make the control decision for each vehicle.On the other hand,when a vehicle leaves/enters a platoon,sending a message to alert its fol-lowing vehicles in the multiplatoon can allow simultaneous reactions,thus enhancing platoon control and road safety.Designing an efficient communication system for multiplatoon(a chain of platoons)is the key for achieving the platoon applications.In this thesis,combining with two major vehicular communication technologies,i.e,the Dedicated Short Range Communications(DSRC)and Long-Term Evolution-Vehicular(LTE-V)technologies,we focus on analyzing the inter-vehicle communications in multiplatoons.Among this two technologies,DSRC is well-developed and widely accepted,while LTE-V is a booming technology.To share the information about vehicle's velocity,acceleration,leav-ing/entering platoon timely and successfully,the specific topics of this thesis are shown below:First of all,DSRC-based communication system model is designed.Considering the lim-ited number of channels that can be used by DSRC,we design that intra-platoon communica-tion and inter-platoon communication will use two different channels.This design can limit the number of required channels to be two and won't increase with the number of platoons within the multiplatoon.Based on the Markov Chain model,we analyze the communication performance of this communication system model with saturated data traffic and ideal channel condition,propose a probabilistic performance analysis of distributed coordination function(DCF)based communications,and derive the expressions for the transmission attempt proba-bility,collision probability,network throughput and packet delay.Numerical results show that the performance of inter-platoon communications depends on the vehicle's role in one platoon and its platoon position within the multiplatoon and that the end-to-end delay of platoons can be reduced by adjusting the contention window size.Secondly,we further analyze the communication performance of the DSRC-based com-munication system model with unsaturated data traffic and nonideal channel condition.By considering each vehicle has unsaturated data traffic and their packets may loss due to channel errors,the analyzed communication performance under this condition meets the actual circ-s better.Based on the first work,a probabilistic analysis method is presented for nonideal communication environment.Furthermore,the expressions of leader vehicle and tail vehicle's transmission attempt probability,collision probability,pocket drop probability,pocket trans-mission delay,average packet transmission rate,and the packet delay and throughput of the inter-platoon communication are derived.The analysis results of this work provide a reference communication delay standard for the study of platoon control algorithm.Furthermore,the communication performance for three typical multiplatooning application scenarios is inves-tigated,and the results indicate that the DSRC-based communication can support the timely delivery of vehicles,information among platoons for diverse on-road applications,while guar-antee the lower delay of communication links.Lastly,a cellular-based multiplatoon communication system model is designed,in which,the LTE-V technology is used for sharing of vehicles' information in multiplatoon.To reduce the number of communication hops of the information of leaving/joining platoon from one to other platoon,this type of information is relayed by leader vehicles and the eNB.Two com-munication models,the evolved Multimedia Broadcast Multicast Services(eMBMS)-based and Device to Device(D2D)multicast-based communication models,are designed for the communications between leader vehicle and the eNB.To realize the sharing of vehicle's ve-locity and acceleration information,a D2D unicast based model is designed for each platoon,in which,a cut-off vehicle is designed to reduce the number of transmission hops of velocity and acceleration information.In addition,a resource allocation scheme,including subchannel allocation and power control schemes,is proposed to improve the channel efficiency and node's power efficiency,which balances the trade-off between the number of required subchannels and the communication delay.Numerical results of this work show that the proposed approaches outperform a D2D-unicast communication-based RA approach in terms of transmission delay,especially in a multiplatoon with a large number of vehicles in its platoons.