| With the rapid development of information technology and communication technology,the driving vehicles communicate with others in Internet of Vehicles(Io Vs)based on mobile data exchange,which achieves convenient and accurate information exchange between vehicle and vehicle,vehicle and infrastructure,vehicle and all kinds of server.It has been the foundation to ensure driving safety,improve the traffic efficiency and provide communication and entertainment services.To be the representative which can best reflect the mobility characteristics of vehicles,the research for related performance and technology of vehicle-to-vehicle communication has been paid more and more attention.As one of the main technologies of vehicle communication,Device-to-Device(D2D)communication is introduced into the process of vehicle data exchange,which could not go through base statios and be direct terminal data exchange.By direct transmission of data between vehicles,the aim can be achieved that reduces the load of network base station and the communication time delay,guarantees the quality of the communication and enhance the overall performance of the Io Vs.Based on the characteristics of vehicles movement and communication in Io Vs,this dissertation,combining with special D2 D channel resources(i.e.subcarriers),should focus on the optimization of vehicles channel resource allocation and data transmission mode,the solution of interference problem caused by resource reuse as well,which is also with the assitance of communication coordination through base stations and clustering vehicles.The main contents of this dissertation are as follows:1)Research on resources allocation and data retransmission mechanism within the cluster based on limited orthogonal frequency division multiplexing D2 D channel resource in the single base station scenario.In view of the existing D2 D channel resource allocation is mainly concentrated on the channel resource reuse with cellular users and the lack of suitable D2 D channel resource allocation mechanism and data transmission mode for the Io Vs environment,which could cause network performance limited.To solve these problems,a mechanism of D2 D dedicated resource allocation and the multicast retransmission with different data is designed,which is based on the limited resources of orthogonal frequency division D2 D channel resource within the cluster in the single base station scenario.According to the existing clustering algorithm to complete the corresponding clustering,the mechanism could allocate only one D2 D communication resource for each vehicle within cluster to eliminate the interference about cellular users and intra-cluster vehicles.Then,a hybrid optimization problem is constructed to maximize the ratio of average spectrum utilization to the retransmission power within the cluster,which can be used to solve the problem of other vehicles within the cluster unable to correctly receive data retransmission request.Cooperative communication is considered to further improve the retransmission result.The simulations show that compared with the method of a fixed retransmission vehicle and not using a relay cooperative transmission,the proposed mechanism can enhance the ratio 59.4% and 30.7%,respectively.2)Research on resources allocation mechanism within the cluster and inter-cluster interference management based on limited orthogonal frequency division multiplexing D2 D channel resource in the single base station scenario.In the multihops Io Vs eironment,it is always ignored that the D2 D communication interference management with a single transmission antenna,cooperative communication used as an effective scheme to improve the reliability of wireless network communication and so on.For these problems,a mechanism is proposed to take into account the D2 D dedicated resource allocation of intra-cluster and inter-cluster,as well as to manage the possible interference.Firstly,a cluster algorithm about D2 D communication architecture is proposed to allocate resources within the cluster in the mechanism.Then,by analyzing the data transmission service of Io Vs,an integer optimization problem is construted to maximize the current spectral efficiency,which could consider the influence factors such as the cooperative communication about resources optimization within the cluster,interference management that each vehicle is equipped with only one communications antenna and so on.The simulations show that with the conditions of random velocity distribution and different vehicle density,network throughput gain with the proposed mechanism has obvious improvement compared with the method without cooperative communication and interference management and the method just with cooperative communication.Generally,the improvement gain can be guaranteed to increase by more than 20% and the maximum gain is up to 75.9%.3)Research on resources allocation mechanism interference management based on orthogonal frequency division multiplexing D2 D channel resource in multiple base stations.With the increase of traffic range and communication service,single base station has been unable to meet full communication coverage of the regional traffic scenarios with many crossroads.Not only that,when the number of vehicles is not limited in one cluster,the D2 D communication resource will be reused for intra-cluster and inter-cluster communication at the same time,which could cause interference management more complex.In this case,a large number of data failed direct transmission will be forwarded through base stations,which will make the network load increase.To this end,a mechanism is designed to manage intra-cluster and inter-cluster interference at the same time by interference alignment in a hybrid base stations scenario.According to the communication load of different traffic area,the deployment of hybrid base stations is considered to meet the demand of traffic load,reduce the deployment cost.The simulations show that,the D2 D direct transmission method with interference alignment could effectively reduce the network load,especially when the whole network data are forwarded through the base stations,which is as a benchmark,the reduction of network load is more obvious. |
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