925 research outputs found
Auction-based Bandwidth Allocation Mechanisms for Wireless Future Internet
An important aspect of the Future Internet is the efficient utilization of
(wireless) network resources. In order for the - demanding in terms of QoS -
Future Internet services to be provided, the current trend is evolving towards
an "integrated" wireless network access model that enables users to enjoy
mobility, seamless access and high quality of service in an all-IP network on
an "Anytime, Anywhere" basis. The term "integrated" is used to denote that the
Future Internet wireless "last mile" is expected to comprise multiple
heterogeneous geographically coexisting wireless networks, each having
different capacity and coverage radius. The efficient management of the
wireless access network resources is crucial due to their scarcity that renders
wireless access a potential bottleneck for the provision of high quality
services. In this paper we propose an auction mechanism for allocating the
bandwidth of such a network so that efficiency is attained, i.e. social welfare
is maximized. In particular, we propose an incentive-compatible, efficient
auction-based mechanism of low computational complexity. We define a repeated
game to address user utilities and incentives issues. Subsequently, we extend
this mechanism so that it can also accommodate multicast sessions. We also
analyze the computational complexity and message overhead of the proposed
mechanism. We then show how user bids can be replaced from weights generated by
the network and transform the auction to a cooperative mechanism capable of
prioritizing certain classes of services and emulating DiffServ and time-of-day
pricing schemes. The theoretical analysis is complemented by simulations that
assess the proposed mechanisms properties and performance. We finally provide
some concluding remarks and directions for future research
vSkyConf: Cloud-assisted Multi-party Mobile Video Conferencing
As an important application in the busy world today, mobile video
conferencing facilitates virtual face-to-face communication with friends,
families and colleagues, via their mobile devices on the move. However, how to
provision high-quality, multi-party video conferencing experiences over mobile
devices is still an open challenge. The fundamental reason behind is the lack
of computation and communication capacities on the mobile devices, to scale to
large conferencing sessions. In this paper, we present vSkyConf, a
cloud-assisted mobile video conferencing system to fundamentally improve the
quality and scale of multi-party mobile video conferencing. By novelly
employing a surrogate virtual machine in the cloud for each mobile user, we
allow fully scalable communication among the conference participants via their
surrogates, rather than directly. The surrogates exchange conferencing streams
among each other, transcode the streams to the most appropriate bit rates, and
buffer the streams for the most efficient delivery to the mobile recipients. A
fully decentralized, optimal algorithm is designed to decide the best paths of
streams and the most suitable surrogates for video transcoding along the paths,
such that the limited bandwidth is fully utilized to deliver streams of the
highest possible quality to the mobile recipients. We also carefully tailor a
buffering mechanism on each surrogate to cooperate with optimal stream
distribution. We have implemented vSkyConf based on Amazon EC2 and verified the
excellent performance of our design, as compared to the widely adopted unicast
solutions.Comment: 10 page
Security and Privacy Issues in Wireless Mesh Networks: A Survey
This book chapter identifies various security threats in wireless mesh
network (WMN). Keeping in mind the critical requirement of security and user
privacy in WMNs, this chapter provides a comprehensive overview of various
possible attacks on different layers of the communication protocol stack for
WMNs and their corresponding defense mechanisms. First, it identifies the
security vulnerabilities in the physical, link, network, transport, application
layers. Furthermore, various possible attacks on the key management protocols,
user authentication and access control protocols, and user privacy preservation
protocols are presented. After enumerating various possible attacks, the
chapter provides a detailed discussion on various existing security mechanisms
and protocols to defend against and wherever possible prevent the possible
attacks. Comparative analyses are also presented on the security schemes with
regards to the cryptographic schemes used, key management strategies deployed,
use of any trusted third party, computation and communication overhead involved
etc. The chapter then presents a brief discussion on various trust management
approaches for WMNs since trust and reputation-based schemes are increasingly
becoming popular for enforcing security in wireless networks. A number of open
problems in security and privacy issues for WMNs are subsequently discussed
before the chapter is finally concluded.Comment: 62 pages, 12 figures, 6 tables. This chapter is an extension of the
author's previous submission in arXiv submission: arXiv:1102.1226. There are
some text overlaps with the previous submissio
QoS multicast routing protocol oriented to cognitive network using competitive coevolutionary algorithm
The human intervention in the network management and maintenance should be reduced to alleviate the ever-increasing spatial and temporal complexity. By mimicking the cognitive behaviors of human being, the cognitive network improves the scalability, self-adaptation, self-organization, and self-protection in the network. To implement the cognitive network, the cognitive behaviors for the network nodes need to be carefully designed. Quality of service (QoS) multicast is an important network problem. Therefore, it is appealing to develop an effective QoS multicast routing protocol oriented to cognitive network.
In this paper, we design the cognitive behaviors summarized in the cognitive science for the network nodes. Based on the cognitive behaviors, we propose a QoS multicast routing protocol oriented to cognitive network, named as CogMRT. It is a distributed protocol where each node only maintains local information. The routing search is in a hop by hop way. Inspired by the small-world phenomenon, the cognitive behaviors help to accumulate the experiential route information. Since the QoS multicast routing is a typical combinatorial optimization problem and it is proved to be NP-Complete, we have applied the competitive coevolutionary algorithm (CCA) for the multicast tree construction. The CCA adopts novel encoding method and genetic operations which leverage the characteristics of the problem. We implement and evaluate CogMRT and other two promising alternative protocols in NS2 platform. The results show that CogMRT has remarkable advantages over the counterpart traditional protocols by exploiting the cognitive favors
Enabling Large-Scale Peer-to-Peer Stored Video Streaming Service with QoS Support
This research aims to enable a large-scale, high-volume, peer-to-peer, stored-video streaming service over the Internet, such as on-line DVD rentals. P2P allows a group of dynamically organized users to cooperatively support content discovery and distribution services without needing to employ a central server. P2P has the potential to overcome the scalability issue associated with client-server based video distribution networks; however, it brings a new set of challenges. This research addresses the following five technical challenges associated with the distribution of streaming video over the P2P network: 1) allow users with limited transmit bandwidth capacity to become contributing sources, 2) support the advertisement and discovery of time-changing and time-bounded video frame availability, 3) Minimize the impact of distribution source losses during video playback, 4) incorporate user mobility information in the selection of distribution sources, and 5) design a streaming network architecture that enables above functionalities.To meet the above requirements, we propose a video distribution network model based on a hybrid architecture between client-server and P2P. In this model, a video is divided into a sequence of small segments and each user executes a scheduling algorithm to determine the order, the timing, and the rate of segment retrievals from other users. The model also employs an advertisement and discovery scheme which incorporates parameters of the scheduling algorithm to allow users to share their life-time of video segment availability information in one advertisement and one query. An accompanying QoS scheme allows reduction in the number of video playback interruptions while one or more distribution sources depart from the service prematurely.The simulation study shows that the proposed model and associated schemes greatly alleviate the bandwidth requirement of the video distribution server, especially when the number of participating users grows large. As much as 90% of load reduction was observed in some experiments when compared to a traditional client-server based video distribution service. A significant reduction is also observed in the number of video presentation interruptions when the proposed QoS scheme is incorporated in the distribution process while certain percentages of distribution sources depart from the service unexpectedly
Desempenho de QoS e mobilidade de sessões multicast em redes dinâmicasMes
Mestrado em Engenharia Electrónica e TelecomunicaçõesThe increasing demand in multimedia group services, contextawareness
and seamless mobility implies strict requirements that
cannot be satisfactorily addressed by the traditional transport control
architectures for session content delivery. Moreover, context-aware
networks introduce personalized concepts: any change in context
can change the overall services and network environments, requiring
the network and multicast sessions to be completely restructured in a
very dynamic way.
Regarding the complexity of maintaining scalability in context-aware
networks, this Thesis has as main goal the development of an
intelligent module, included in C-CAST architecture, capable of
managing the entire network scheme. This mechanism depending on
the scenario and the context of users and sources, and in
cooperation with other network entities, must decide the most
suitable network transport path in order to provide the best multiparty
content delivery to the users, and manage the dynamicity of the
network whenever changes occur. To perform its implementation, it
was used an approach based in the interaction of different network
components, exchanging context information between them. The
intelligent module, using the updated network information, decides
the better network connection to serve each user.
In order to simulate the network behaviour in various situations,
several scenarios were tested to evaluate its performance. The
network is evaluated according to the several configured parameters,
evaluating the improvements achieved in the network performance
concerning different metrics, e.g. delay, lost packets ratio, overhead
introduced by the architecture signalling. Through the implemented
simulation setup, it is possible to conclude that the deployment of the
solution proposed effectively provides an enhanced service to the
users, distributing the multiparty content with QoS assurance using
context information.O aumento da exigência em serviços de grupo, redes baseadas em
contexto e mobilidade transparente implicam requisitos rÃgidos que
não podem ser satisfeitos pelas arquitecturas tradicionais de controlo
de transporte para entrega de conteúdos de sessão. Não obstante,
redes baseadas em contexto introduzem conceitos personalizados:
qualquer mudança no contexto pode mudar completamente os
serviços e a própria rede, sendo necessário que a rede e as sessões
multicast sejam completamente reestruturadas de uma forma
dinâmica.
Tendo em conta a complexidade de manter a escalabilidade em
redes baseadas em contexto, esta Tese tem como principal objectivo
o desenvolvimento de um módulo inteligente, que faz parte da
arquitectura do projecto C-CAST, capaz de gerir toda a rede. Este
mecanismo, dependendo do cenário da rede e do contexto dos
utilizadores e das fontes, e em cooperação com outras entidades da
rede, deve seleccionar a o caminho mais apropriado da rede de
modo a fornecer da melhor forma o conteúdo aos utilizadores, e gerir
a dinâmicidade da rede sempre que ocorrem mudanças. Para o
implementar foi usada um método baseado na interacção de vários
componentes, que trocam informação sobre contextos entre eles. O
componente inteligente, usando informação actualizada da rede
decide qual a melhor conexão da rede para servir cada utilizador.
De forma a simular o comportamento da rede em várias situações,
foram testados diversos cenários para avaliar a sua performance. A
rede é avaliada de acordo com os vários parâmetros configurados,
avaliando as melhorias conseguidas na performance da rede, por
exemplo em termos de atrasos, rácio de pacotes perdidos e a carga
imposta pelas mensagens de controlo da arquitectura. Através das
simulações efectuadas é possÃvel concluir que aplicando a
arquitectura proposta, é fornecido de forma eficiente um serviço
melhorado aos utilizadores, distribuindo o serviço de grupo com
garantias de Qualidade de Serviço e usando informação de contexto
Easy Wireless: broadband ad-hoc networking for emergency services
Wireless ad-hoc networks will enable emergency services to continuously overview and act upon the actual status of the situation by retrieving and exchanging detailed up-to-date information between the rescue workers. Deployment of high-bandwidth, robust, self-organising ad-hoc networks will enable quicker response to typical what/where/when questions, than the more vulnerable low-bandwidth communication networks currently in use. This paper addresses a number of results of the Easy Wireless project that enable high bandwidth robust ad-hoc networking. Most of the concepts presented here have been experimentally verified and/or prototyped
Quasi-omniscient networks: scenarios on context capturing and new services through wireless sensor networks
This paper addresses future scenarios for the telecommunications field, addressing the impact of three important research trends in computer networks: Context, Sensors and Wireless Networks. The proposed scenarios clearly highlight the possible synergies between the defined areas, and describe the role of Users and Network Operators in order to achieve the described goals. The potential danger of an over-encompassing network is identified, with a brief discussion on the challenges associated to the implementation of such a knowledge-aware communications network. The paper finalizes presenting a classification on the typical scenarios to be expected, and highlighting the associated challenges. It also presents a proposal on a scalable network infrastructure for Context processing
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