853 research outputs found
Improving QoS of VANET using Network Coding
Vehicular Ad hoc Networks -VANET as a sub class of Mobile Ad hoc Networks -MANET provides a wireless communication among vehicles and vehicle to road side equipment. VANET allows vehicles to form a self-organized network without the need for permanent infrastructure. With high number of nodes and mobility, ensuring the Quality of Service- QoS in VANET is a challenging task. QoS is essential to improve the communication efficiency in vehicular networks. Thus a study of QoS in VANET is useful as a fundamental for constructing an effective vehicular network. In this paper, we propose Network coding Technique to improve Bandwidth utilization on VANET. When two sources are involved in broadcasting in the same area and at same time , the relay will make use of Network coding to reduce the Bandwidth consumption. While receiving the packet, a relay has to decide whether to send the packet directly to reduce the delay or use Network coding for effective Bandwidth utilization. In order to make trade off, we introduce two kind of protocols named Buffer Size Control Scheme -BSCS and Time Control Scheme -TCS. By this two protocols, we aim to reduce the delay that is experienced by each packet and achieving better bandwidth utilization
Efficient cellular load balancing through mobility-enriched vehicular communications
Supporting effective load balancing is paramount for increasing network utilization efficiency and improving the perceivable user experience in emerging and future cellular networks. At the same time, it is becoming increasingly alarming that current communication practices lead to excessive energy wastes both at the infrastructure side and at the terminals. To address both these issues, this paper discusses an innovative communication approach enabled by the implementation of device-to-device (d2d) communication over cellular networks. The technique capitalizes on the delay tolerance of a significant portion of Internet applications and the inherent mobility of the nodes to achieve significant performance gains. For delay-tolerant messages, a mobile node can postpone message transmission—in a store–carry and forward manner—for a later time to allow the terminal to achieve communication over a shorter range or to postpone communication to when the terminal enters a cooler cell, before engaging in communication. Based on this framework, a theoretical model is introduced to study the generalized multihop d2d forwarding scheme where mobile nodes are allowed to buffer messages and carry them while in transit. Thus, a multiobjective optimization problem is introduced where both the communication cost and the varying load levels of multiple cells are to be minimized. We show that the mathematical programming model that arises can be efficiently solved in time. Furthermore, extensive numerical investigations reveal that the proposed scheme is an effective approach for both energy-efficient communication and offering significant gains in terms of load balancing in multicell topologies
Performance of management solutions and cooperation approaches for vehicular delay-tolerant networks
A wide range of daily-life applications supported by vehicular networks attracted the interest,
not only from the research community, but also from governments and the automotive
industry. For example, they can be used to enable services that assist drivers on the roads (e.g.,
road safety, traffic monitoring), to spread commercial and entertainment contents (e.g., publicity),
or to enable communications on remote or rural regions where it is not possible to have
a common network infrastructure. Nonetheless, the unique properties of vehicular networks
raise several challenges that greatly impact the deployment of these networks.
Most of the challenges faced by vehicular networks arise from the highly dynamic network
topology, which leads to short and sporadic contact opportunities, disruption, variable
node density, and intermittent connectivity. This situation makes data dissemination an interesting
research topic within the vehicular networking area, which is addressed by this study.
The work described along this thesis is motivated by the need to propose new solutions to deal
with data dissemination problems in vehicular networking focusing on vehicular delay-tolerant
networks (VDTNs).
To guarantee the success of data dissemination in vehicular networks scenarios it is important
to ensure that network nodes cooperate with each other. However, it is not possible
to ensure a fully cooperative scenario. This situation makes vehicular networks suitable to the
presence of selfish and misbehavior nodes, which may result in a significant decrease of the
overall network performance. Thus, cooperative nodes may suffer from the overwhelming load
of services from other nodes, which comprises their performance.
Trying to solve some of these problems, this thesis presents several proposals and studies
on the impact of cooperation, monitoring, and management strategies on the network performance
of the VDTN architecture. The main goal of these proposals is to enhance the network
performance. In particular, cooperation and management approaches are exploited to improve
and optimize the use of network resources. It is demonstrated the performance gains attainable
in a VDTN through both types of approaches, not only in terms of bundle delivery probability,
but also in terms of wasted resources.
The results and achievements observed on this research work are intended to contribute
to the advance of the state-of-the-art on methods and strategies for overcome the challenges
that arise from the unique characteristics and conceptual design of vehicular networks.O vasto número de aplicações e cenários suportados pelas redes veiculares faz com que
estas atraiam o interesse nĂŁo sĂł da comunidade cientĂfica, mas tambĂ©m dos governos e da indĂşstria
automĂłvel. A tĂtulo de exemplo, estas podem ser usadas para a implementação de serviços
e aplicações que podem ajudar os condutores dos veĂculos a tomar decisões nas estradas, para
a disseminação de conteúdos publicitários, ou ainda, para permitir que existam comunicações
em zonas rurais ou remotas onde nĂŁo Ă© possĂvel ter uma infraestrutura de rede convencional.
Contudo, as propriedades únicas das redes veiculares fazem com que seja necessário ultrapassar
um conjunto de desafios que tĂŞm grande impacto na sua aplicabilidade.
A maioria dos desafios que as redes veiculares enfrentam advĂŞm da grande mobilidade dos
veĂculos e da topologia de rede que está em constante mutação. Esta situação faz com que este
tipo de rede seja suscetĂvel de disrupção, que as oportunidades de contacto sejam escassas e de
curta duração, e que a ligação seja intermitente. Fruto destas adversidades, a disseminação dos
dados torna-se um tópico de investigação bastante promissor na área das redes veiculares e por
esta mesma razão é abordada neste trabalho de investigação. O trabalho descrito nesta tese é
motivado pela necessidade de propor novas abordagens para lidar com os problemas inerentes
à disseminação dos dados em ambientes veiculares.
Para garantir o sucesso da disseminação dos dados em ambientes veiculares é importante
que este tipo de redes garanta a cooperação entre os nós da rede. Contudo, neste tipo de ambientes
nĂŁo Ă© possĂvel garantir um cenário totalmente cooperativo. Este cenário faz com que
as redes veiculares sejam suscetĂveis Ă presença de nĂłs nĂŁo cooperativos que comprometem
seriamente o desempenho global da rede. Por outro lado, os nĂłs cooperativos podem ver o seu
desempenho comprometido por causa da sobrecarga de serviços que poderão suportar.
Para tentar resolver alguns destes problemas, esta tese apresenta várias propostas e estudos
sobre o impacto de estratégias de cooperação, monitorização e gestão de rede no desempenho
das redes veiculares com ligações intermitentes (Vehicular Delay-Tolerant Networks
- VDTNs). O objetivo das propostas apresentadas nesta tese Ă© melhorar o desempenho global
da rede. Em particular, as estratégias de cooperação e gestão de rede são exploradas para
melhorar e optimizar o uso dos recursos da rede. Ficou demonstrado que o uso deste tipo de
estratégias e metodologias contribui para um aumento significativo do desempenho da rede,
não só em termos de agregados de pacotes (“bundles”) entregues, mas também na diminuição
do volume de recursos desperdiçados.
Os resultados observados neste trabalho procuram contribuir para o avanço do estado
da arte em métodos e estratégias que visam ultrapassar alguns dos desafios que advêm das
propriedades e desenho conceptual das redes veiculares
Hybrid Satellite-Terrestrial Communication Networks for the Maritime Internet of Things: Key Technologies, Opportunities, and Challenges
With the rapid development of marine activities, there has been an increasing
number of maritime mobile terminals, as well as a growing demand for high-speed
and ultra-reliable maritime communications to keep them connected.
Traditionally, the maritime Internet of Things (IoT) is enabled by maritime
satellites. However, satellites are seriously restricted by their high latency
and relatively low data rate. As an alternative, shore & island-based base
stations (BSs) can be built to extend the coverage of terrestrial networks
using fourth-generation (4G), fifth-generation (5G), and beyond 5G services.
Unmanned aerial vehicles can also be exploited to serve as aerial maritime BSs.
Despite of all these approaches, there are still open issues for an efficient
maritime communication network (MCN). For example, due to the complicated
electromagnetic propagation environment, the limited geometrically available BS
sites, and rigorous service demands from mission-critical applications,
conventional communication and networking theories and methods should be
tailored for maritime scenarios. Towards this end, we provide a survey on the
demand for maritime communications, the state-of-the-art MCNs, and key
technologies for enhancing transmission efficiency, extending network coverage,
and provisioning maritime-specific services. Future challenges in developing an
environment-aware, service-driven, and integrated satellite-air-ground MCN to
be smart enough to utilize external auxiliary information, e.g., sea state and
atmosphere conditions, are also discussed
Cooperative control of relay based cellular networks
PhDThe increasing popularity of wireless communications and the higher data
requirements of new types of service lead to higher demands on wireless networks.
Relay based cellular networks have been seen as an effective way to meet users’
increased data rate requirements while still retaining the benefits of a cellular
structure. However, maximizing the probability of providing service and spectrum
efficiency are still major challenges for network operators and engineers because of
the heterogeneous traffic demands, hard-to-predict user movements and complex
traffic models.
In a mobile network, load balancing is recognised as an efficient way to increase
the utilization of limited frequency spectrum at reasonable costs. Cooperative
control based on geographic load balancing is employed to provide flexibility for
relay based cellular networks and to respond to changes in the environment.
According to the potential capability of existing antenna systems, adaptive radio
frequency domain control in the physical layer is explored to provide coverage at
the right place at the right time.
This thesis proposes several effective and efficient approaches to improve
spectrum efficiency using network wide optimization to coordinate the coverage
offered by different network components according to the antenna models and
relay station capability. The approaches include tilting of antenna sectors,
changing the power of omni-directional antennas, and changing the assignment of
relay stations to different base stations. Experiments show that the proposed
approaches offer significant improvements and robustness in heterogeneous traffic
scenarios and when the propagation environment changes. The issue of predicting
the consequence of cooperative decisions regarding antenna configurations when
applied in a realistic environment is described, and a coverage prediction model is
proposed. The consequences of applying changes to the antenna configuration on
handovers are analysed in detail. The performance evaluations are based on a
system level simulator in the context of Mobile WiMAX technology, but the
concepts apply more generally
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