Author: Zhang, Chisheng
Title: Quality of services and user experience in wireless vehicular internet access
Advisors: Cao, Jiannong (COMP)
Degree: Ph.D.
Year: 2015
Subject: Mobile communication systems
Wireless communication systems
Vehicular ad hoc networks (Computer networks)
Hong Kong Polytechnic University -- Dissertations
Department: Department of Computing
Pages: xviii, 118 pages : color illustrations
Language: English
Abstract: Vehicular Ad-hoc Networks (VANET) have attracted increasing attentions from both research and industry communities. By equipping vehicles with on-board wireless communication facilities, the vehicular networking technology provides a variety of novel and exciting applications to vehicular users to enhance their road safety and travel comfort, and increase experiences of their on-road life. In the development of vehicular applications and services, we witness the trend of complementary vehicular networks and the Internet. To support high quality applications and services, well-planned network infrastructure and vehicle-oriented application should be jointly considered in designing vehicular Internet access networks.To improve the quality of vehicular Internet access from the above two perspectives,we use Quality of Service (QoS) and Quality of user Experience (QoE) respectively as the measures. Quality of service is a performance indicator for vehicular access networks and characterizes the attributes associated with the networks and their protocols. On the other hand, quality of user experience is a performance metric defined from the end-user's point of view and represents the perceived quality of applications and services. Although with a bright future,the way to ubiquitous and efficient vehicular Internet access still faces with numerous research and engineering challenges. Due to the wireless spectrum crisis in licensed wireless communication channels,the existing well-planned cel-lular networks are not adequate to satisfy the increasing data demand from vehicular appli-cations. It is a challenging issue to efficiently exploit Wi-Fi or other wireless communication technologies to establish or supplement city-wide or nation-wide road-side vehicular Internet access networks. Secondly, to be resilient to performance degradation caused by highly dynamic topology of vehicular networks, packet routing and data dissemination protocols should be adaptive to network partition and link disconnection. Last but not the least, quality of conventional Internet applications and services suffer greatly from the vehicle mobility and intermittent Internet access. To improve the user experience, application-level service enhancement should be considered in designing vehicular applications and services.
In this research, we systematically analyze the above problems and propose effective and efficient solutions to address the afore-mentioned challenges. Our goal is to build a framework to facilitate the multi-user Internet access in wireless vehicular networks with QoS guaranteed network infrastructure and protocols, and QoE enhanced applications and services. Our contribution are summarized as follows. To address the issue of infrastructure planning, we identify the problem how to deploy different types of network components,such as base stations and relays, in a cost-efficient way to maximize the network performance.First,we propose a detailed analytical model for infrastructure-based vehicular Internet access in the presence of different network compo-nents. Then, through extensive simulations based on the proposed model, we obtain some guidelines on choosing and deploying different network components in vehicular Internet access networks. Finally, as a special case study of infrastructure planning, we investigate the incremental and cost-efficient network planning (ICNP) problem in vehicular Internet access networks with the objective of improving network capacity for an existing network under limited deployment cost. After defining a cost efficiency metric,namely incremental upgrade utility (IUU), we develop a heuristic algorithm, called Greedy Link Deployment algorithm (GLiD) with approximation ratio (1-1/{591}e) for deploying additional wireless links to the existing networks to achieve the maximum performance improvement. To address the issue of protocol adaption,we investigate the maximum network connectivity problem in vehicular Internet access networks, in which vehicles adopt both vehicle-to-infrastructure and vehicle-to-vehicle communications. We first analyze the characteristics of network connectivity in vehicular Internet access networks and derive a closed form to represent the connectivity probability under specific road-side units (RSU) deployment model and vehicle arrival rate. Then, we develop a connectivity-oriented data dissemina-tion (CoDA) protocol to maximize the minimum network connectivity in vehicular Internet access systems based on the probabilistic analysis. Finally, we validate the CoDA protocol through extensive simulations and the results show that the CoDA protocol can achieve the maximum connectivity probability in vehicular communications in different network scenarios. To address the issue of service enhancement,we take localization service, a fundamental service in vehicular applications, as an example.We study the vehicular localization problem in urban environments. It is a challenging task to achieve high localization accuracy due to the severe multi-path effects caused by buildings and interfering sources in urban area. First, we perform a series of experiments which shows that the vehicular mobility and multi-path effect impose severe degradation in localization performance of GPS receivers. We then identify the correlation between the similarity of signal-noise ratio (SNR) values of GPS signals from different GPS satellites and relative distance among those GPS receivers. Based on the observation, we design the Networking-GPS algorithm, which constructs atomic redundantly rigid graphs according to the signal similarity and expands atomic triangles to reach anchor points along the road side. Therefore, the local accuracy can be transited to the global accuracy through the redundantly rigid transformation. Our evaluation based on real GPS traces shows that Networking-GPS can achieve higher accuracy against multi-path effect in urban area.
Rights: All rights reserved
Access: open access

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