Performance Analysis And Optimization On Heterogeneous Vehicular Networks

In the recent years, traffic congestion and accidents, as well as environmental pollution caused by road traffic and fuel consumption have become important global issues. Both developing and developed countries are plagued by traffic problems. High traffic accident rates claim huge losses of life and property. Moreover, traffic congestion decreases the efficiency of transportation system, and hence hinders economic growth. As an emerging technology, vehicular networks are designed to provide information exchange via Vehicle-to-Vehicle (V2V)and Vehicle-to-Infrastructure (V2I) communications to improve the current transportation systems. However, in the dynamic vehicular environments, current wireless communication technologies are difficult to guarantee the Quality of Service (QoS) of vehicular services. Thus,how to guarantee the performance of vehicular services has become an urgent issue. Therefore, in this dissertation, on the basis of various wireless radio access technologies, we propose the Heterogeneous Vehicular Network (HetVNETs) and focuse on the performance analysis and optimization of it. Firstly, this dissertation works on the urban mulit-cell scenarios; And then analyzes the performance of cluster-based transmission scheme; Finally, it investigates on the performance optimization on HetVNETs from the cooperative transmission and wireless resources allocation. The major contributions of this dissertation include:1. Architecture design for Heterogeneous Vehicular NetworkAlthough there is a plethora of reported studies on either Dedicated Short Range Communication (DSRC) or cellular networks, the requirements of services that require stringent real-time safety cannot always be guaranteed by single communication technology. Therefore,based on the analysis of the requirements of vehicular services, this paper presents the HetVNETs, which integrates cellular networks with DSRC,to meet the communication requirements of the ITS services and discusses the advantages and challenges of key technologies in HetVENTs, including DSRC and cellular networks. Secondly, the detailed analysises on classic application scenarios are presented. And then, to deal with the dynamic characteristics and rapid increasing requirements of HetVNETs, the cloud-based three-layer HetVENTs is proposed, in terms of Software-Defined HetVNETs (SERVICE), the characteristics, such as centralized and fast configuration, can obviously improve the its performance. Finally, we give deep designs and difinitions on its framework and logical interface.2. Performance analysis for cluster-based transmission scheme in HetVNETsIn this dissertation, we put forward an analysis model for cluster-based transmission scheme in HetVENTs. Firstly, based on the HetVNETs, we develop the framework of Cluster-based HetVNET by employing the cluster mechanism, which can obviously reduce the signaling overhead and the frequency of handover. Secondly, the performance analysis models of intra-cluster and inter-cluster communications are designed based on Markov queuing model, in which the Markov chain is applied to depict the features of transmission channel.Thirdly, due to the explosion of state space, the model decomposition and iteration techniques are proposed to handle this problem, which transforms the exponential complexity into linear complexity. Based on the developed analytical model, the performance metrics of different scheduling schemes, in term of throughput, delay, dropping probability and queue length, are studied and compared which give a useful guideline for network configuration of future vehicular networks.3. Cooperative transmission optimization for HetVNETsFirstly, cooperative communications are introduced in HetVNETs to improve its performance. Secondly, considering the differnent QoS requirements and the channel state, we formulate the problem of link scheduling and resource allocation as a non-convex optimization problem,for the sake of maximizing sum throughput (MST) and maximizing sum utility (MSU) of the networks, respectly. Thirdly, to reduce the complexity of the considered problem, the original problem is transformed into an integer programming problem, and based on knapsack problem (KP), we propose two cooperative transmission schemes: link scheduling scheme and joint optimization of link scheduling and resource allocation scheme. Fianlly, we build the simulation plaform which intergers traffic and communication simulations via OPNET simuation tool and simulation results indicate that the proposed scheme significantly improves the average utility and average data rates with sustainable computational complexity. Moreover,the designed cooperative communication system achieves higher spectral efficiency and better fairness.4. Virtualized radio resource scheduling in SERVICEFirstly, we introduce the idea of wireless virtualization into HetVNETs and propose a logical architecture for virtual resource manmagement. In the proposed architecture, both the network infrastructure and radio resources are virtualized as virtual resources,which can be allocation to vehicular users dynamically. Secondly, in allusion to the virtual radio resource, we formulate the problem of virtual resource allocation as an infinite-horizon average cost Partially Observed Markov Decision Process (POMDP). Thirdly, to reduce the complexity,we solve it in two stages, i.e., Macro Virtualization Resource Allocation(MaVRA) and Micro Virtualization Resource Allocation (MiVRA). The former is executed based on large time scale variables (traffic density)while the later is operated according to short time-scale variable (channel state and queue state). During the process, online learning and linear approximation are employed and the low-complexity and sub-optimal scheme is obtained. Finally, simulation results show that the proposed scheme outperforms traditional ones.