Investigation Of Resource Overheads,Latency,Reliability,and Related Technical Schemes In Vehicular Networks

Internet of Vehicle(IoV)is an essential part for intelligent transportation system(ITS).In vehicular communication network,vehicle-to-everything(V2X)services to are provided to improve the traffic safety and guarantee multimedia requirements.In general,V2X communication require low latency and high reliability,which brings big challenges for vehicular communication network design.In this paper,we investigate the caching strategy,content delivery,transmission scheme and related technologies in IoV.Firstly,in the thesis,a cooperative caching algorithm is proposed for cluster-based vehicular content networks(VCNs)with vehicular caches.Different from the existing noncooperative algorithm,the proposed algorithm is designed based on the mobility of vehicles,globe caching status of vehicular clusters,the caching capacity constraints of vehicles.A novel average accumulated network cost metric is defined,i.e.,a weighted sum of average accumulated normalized backhaul cost and average accumulated normalized vehicular caching cost.Simulation results show that the proposed caching algorithm is efficient to reduce the network cost.Additionally,we propose a cooperative roadside unit(RSU)caching policy for vehicular content delivery networks(VCDNs)in two-way road with a T-junction.In our system model,due to the constraint of base station(BS)transmission capacity,vehicles can achieve better download delay performance if the requested contents are stored in the cacheenabled RSUs.According to the traffic situations,vehicles are classified into four types.With this framework,the closed-from result of the average download delay is derived.The problem of minimizing the average download delay with the proposed cooperative caching policy is formulated subject to the cache capacity constraint of RSUs.Since the optimization problem falls into an NP-hard problem,we adopt a fast simulated anneal(FSA)algorithm for content allocation.Simulation results show that the proposed cooperative algorithms is more efficient for the average download delay reduction compared with the conventional non-cooperative algorithms.Furthermore,a connectivity-aware content caching algorithm is proposed to help cache-enabled moving vehicles managing theirs caches.Considering that the vehicle-to-vehicle(V2V)content delivery process highly depends on the inter-vehicle connectivity,the proposed caching algorithm can avoid unnecessary caching cost and improve the caching utility.Secondly,the performance of video content delivery in IoV is investigated from the perspective of playback delay,video quality and network cost,respectively.For playback delay,a stochastic network calculus(SNC)based method is proposed to obtain the stochastic playback delay upper bounds of vehicular video content delivery networks with cache-enabled RSUs.The stochastic strict service curve of RSU to vehicle(R-V)channel,and equivalent base station(BS)to RSU to vehicle(B-R-V)channel are derived,respectively.With this framework,the stochastic playback delay upper bounds are obtained.For video quality,we investigate the user fairness power allocation(PA)for video transmission in a non-orthogonal multiple access(NOMA)-assisted vehicular communication network,where the video quality can be adaptively adjusted based on the network conditions.A new performance metric,called the average video quality degradation probability,is proposed to describe the adaptive video quality.Based on the principles of NOMA and user queue model,the average video quality degradation probability of users is derived.Next,a bisection search based power allocation(PA)algorithm is proposed to balance the video quality between the NOMA pair.For network cost,mobility-aware proactive delivery scheme(MA-PDS)is proposed to take full advantage of resource in vehicular communication networks.By adopting the proposed MAPDS,the RSU can proactively deliver some unrequested chunks based on the prediction of the network topology change and network condition.To evaluate the performance of content delivery scheme,a network cost is defined as the normalized weighted sum of the MBS cost and the RSU transmission power cost.Simulation results demonstrate that RSU caching,NOMA transmission,and proactive delivery can significantly improve the performance of video transmission.Thirdly,in this thesis,the stochastic delay guarantee for real-time vehicular communications with interference is investigated.Considering the randomness of wireless fading in both data links and interference links,the stochastic service process provided by one-hop Rician fading channel and two-hop channel with a limited-interference is respectively characterized in terms of the moment generation function(MGF).The delay-outage probability is defined as the probability that the actual transmission delay exceeds a threshold value.To evaluate the stochastic delay guarantee,we derive an upper bound on the minimum acceptable delay threshold and a lower bound on the maximum supportable transmitted data size with the constraint of the delay-outage probability,respectively.Simulation results show that the bounds obtained by the theoretical analysis are reasonably tight and well reflect the effect of the interference on the stochastic delay guarantee.Besides,we analyze the stochastic delay of the edge users in V2V communications with full-duplex(FD)user relaying.The delay-outage probability is derived and the optimal PA is calculated to minimize the delay-outage probability.Simulation results show that the proposed NOMA based FD user relaying can effectively improve the delay performance of edge user.Furthermore,the theoretical analysis can provide guideline to the user relaying protocol design.Fourthly,we focus on the power allocation(PA)and the successive interference cancellation(SIC)of a cognitive radio(CR)vehicular communication network with uplink NOMA assisted secondary transmission.Considering the power constraint for secondary transmission in CR system,we propose a min-max power allocation(PA)algorithm to guarantee the secondary user(SU)fairness from the perspective of the achievable rate.Then,an adaptive SIC scheme is designed to improve the spectrum efficiency of uplink NOMA.Numerical results show that the proposed uplink NOMA with the adaptive SIC scheme can significantly enhance the fairness of SUs.Lastly,in this thesis,we propose a NOMA-assisted multicast scheme for V2V transmission in platoon.Specifically,platoon leader(PL)transmit data to platoon members(PMs)with the aid of vehicular relay.According to the network topology,channel condition,MAC protocol,and the principle of NOMA,we analyze the packet loss of different PMs.Furthermore,a PA algorithm is proposed to decrease the average packet loss probability which can be used to measure the reliability of V2V transmission.The simulation results validate that the proposed NOMA-assisted multicast scheme can significantly enhance the transmission reliability.Furthermore,the proposed NOMA-assisted multicast scheme can reduce the number of slots for the successful packet transmission,which can help to improve the V2V transmission delay performance.trigger.Simulation results demonstrate the effectiveness of the proposed algorithm from three aspects:detection accuracy,throughput and energy efficiency.