Hybrid, Proactive In-Network Caching for Mobile On-Demand Video Streaming

Mobile video streaming has become an essential application in mobile wireless networks,making up most of the mobile data of today’s Internet traffic. Studies have shown that mobile video data is projected to make up about 78 percent of the global mobile data traffic, and that global mobile data traffic is expected to increase sevenfold by 2021.Massive small cell base station (SBS) deployments have emerged as a potential solution promising to fulfill these unprecedented mobile data demands, by offering great coverage enhancements and maintaining high quality of video streaming. However, due to relatively small cell sizes and high user mobility, mobile video streaming in dense SBS networks faces fundamental challenges such as intermittent connectivity and frequent handoffs, causing degradation in video streaming quality. In this thesis, we tackle this issue by introducing a hybrid proactive in-network caching framework that stores some popular videos at the edge of the network, namely at the SBSs, while also pre-caching video contents in advance to better service mobile users. The proposed framework essentially reduces the need for bringing every requested video from the core (original)network, which results in alleviating network congestion by reducing back-haul traffic and in improving mobile video streaming experience by avoiding service discontinuity during handoffs. We develop a simulation framework using MATLAB to study the performance of the proposed hybrid proactive caching technique, and show using simulations that the proposed technique can effectively improve video quality of experience and reduce back-haul traffic.Keywords: hybrid proactive caching, Video Quality of Experience, Small-cell Base Station (SBS)., Mobile video streamin

Performance metrics and routing in vehicular ad hoc networks

The aim of this thesis is to propose a method for enhancing the performance of Vehicular Ad hoc Networks (VANETs). The focus is on a routing protocol where performance metrics are used to inform the routing decisions made. The thesis begins by analysing routing protocols in a random mobility scenario with a wide range of node densities. A Cellular Automata algorithm is subsequently applied in order to create a mobility model of a highway, and wide range of density and transmission range are tested. Performance metrics are introduced to assist the prediction of likely route failure. The Good Link Availability (GLA) and Good Route Availability (GRA) metrics are proposed which can be used for a pre-emptive action that has the potential to give better performance. The implementation framework for this method using the AODV routing protocol is also discussed. The main outcomes of this research can be summarised as identifying and formulating methods for pre-emptive actions using a Cellular Automata with NS-2 to simulate VANETs, and the implementation method within the AODV routing protocol

Investigating TCP performance in mobile ad hoc networks

Mobile ad hoc networks (MANETs) have become increasingly important in view of their promise of ubiquitous connectivity beyond traditional fixed infrastructure networks. Such networks, consisting of potentially highly mobile nodes, have provided new challenges by introducing special consideration stemming from the unique characteristics of the wireless medium and the dynamic nature of the network topology. The TCP protocol, which has been widely deployed on a multitude of internetworks including the Internet, is naturally viewed as the de facto reliable transport protocol for use in MANETs. However, assumptions made at TCP’s inception reflected characteristics of the prevalent wired infrastructure of networks at the time and could subsequently lead to sub-optimal performance when used in wireless ad hoc environments. The basic presupposition underlying TCP congestion control is that packet losses are predominantly an indication of congestion in the network. The detrimental effect of such an assumption on TCP’s performance in MANET environments has been a long-standing research problem. Hence, previous work has focused on addressing the ambiguity behind the cause of packet loss as perceived by TCP by proposing changes at various levels across the network protocol stack, such as at the MAC mechanism of the transceiver or via coupling with the routing protocol at the network layer. The main challenge addressed by the current work is to propose new methods to ameliorate the illness-effects of TCP’s misinterpretation of the causes of packet loss in MANETs. An assumed restriction on any proposed modifications is that resulting performance increases should be achievable by introducing limited changes confined to the transport layer. Such a restriction aids incremental adoption and ease of deployment by requiring minimal implementation effort. Further, the issue of packet loss ambiguity, from a transport layer perspective, has, by definition, to be dealt with in an end-to-end fashion. As such, a proposed solution may involve implementation at the sender, the receiver or both to address TCP shortcomings. Some attempts at describing TCP behaviour in MANETs have been previously reported in the literature. However, a thorough enquiry into the performance of those TCP agents popular in terms of research and adoption has been lacking. Specifically, very little work has been performed on an exhaustive analysis of TCP variants across different MANET routing protocols and under various mobility conditions. The first part of the dissertation addresses this shortcoming through extensive simulation evaluation in order to ascertain the relative performance merits of each TCP variant in terms of achieved goodput over dynamic topologies. Careful examination reveals sub-par performance of TCP Reno, the largely equivalent performance of NewReno and SACK, whilst the effectiveness of a proactive TCP variant (Vegas) is explicitly stated and justified for the first time in a dynamic MANET environment. Examination of the literature reveals that in addition to losses caused by route breakages, the hidden terminal effect contributes significantly to non-congestion induced packet losses in MANETs, which in turn has noticeably negative impact on TCP goodput. By adapting the conservative slow start mechanism of TCP Vegas into a form suitable for reactive TCP agents, like Reno, NewReno and SACK, the second part of the dissertation proposes a new Reno-based congestion avoidance mechanism which increases TCP goodput considerably across long paths by mitigating the negative effects of hidden terminals and alleviating some of the ambiguity of non-congestion related packet loss in MANETs. The proposed changes maintain intact the end-to-end semantics of TCP and are solely applicable to the sender. The new mechanism is further contrasted with an existing transport layer-focused solution and is shown to perform significantly better in a range of dynamic scenarios. As solution from an end-to-end perspective may be applicable to either or both communicating ends, the idea of implementing receiver-side alterations is also explored. Previous work has been primarily concerned with reducing receiver-generated cumulative ACK responses by “bundling” them into as few packets as possible thereby reducing misinterpretations of packet loss due to hidden terminals. However, a thorough evaluation of such receiver-side solutions reveals limitations in common evaluation practices and the solutions themselves. In an effort to address this shortcoming, the third part of this research work first specifies a tighter problem domain, identifying the circumstances under which the problem may be tackled by an end-to-end solution. Subsequent original analysis reveals that by taking into account optimisations possible in wireless communications, namely the partial or complete omission of the RTS/CTS handshake, noticeable improvements in TCP goodput are achievable especially over long paths. This novel modification is activated in a variety of topologies and is assessed using new metrics to more accurately gauge its effectiveness in a wireless multihop environment

Improving the Performance of Wireless LANs

This book quantifies the key factors of WLAN performance and describes methods for improvement. It provides theoretical background and empirical results for the optimum planning and deployment of indoor WLAN systems, explaining the fundamentals while supplying guidelines for design, modeling, and performance evaluation. It discusses environmental effects on WLAN systems, protocol redesign for routing and MAC, and traffic distribution; examines emerging and future network technologies; and includes radio propagation and site measurements, simulations for various network design scenarios, numerous illustrations, practical examples, and learning aids

Poor Man's Content Centric Networking (with TCP)

A number of different architectures have been proposed in support of data-oriented or information-centric networking. Besides a similar visions, they share the need for designing a new networking architecture. We present an incrementally deployable approach to content-centric networking based upon TCP. Content-aware senders cooperate with probabilistically operating routers for scalable content delivery (to unmodified clients), effectively supporting opportunistic caching for time-shifted access as well as de-facto synchronous multicast delivery. Our approach is application protocol-independent and provides support beyond HTTP caching or managed CDNs. We present our protocol design along with a Linux-based implementation and some initial feasibility checks

Network-aware video streaming for future media Internet

272 p

Incrementando as redes centradas à informaçãopara uma internet das coisas baseada em nomes

The way we use the Internet has been evolving since its origins. Nowadays, users are more interested in accessing contents and services with high demands in terms of bandwidth, security and mobility. This evolution has triggered the emergence of novel networking architectures targeting current, as well as future, utilisation demands. Information-Centric Networking (ICN) is a prominent example of these novel architectures that moves away from the current host-centric communications and centres its networking functions around content. Parallel to this, new utilisation scenarios in which smart devices interact with one another, as well as with other networked elements, have emerged to constitute what we know as the Internet of Things (IoT). IoT is expected to have a significant impact on both the economy and society. However, fostering the widespread adoption of IoT requires many challenges to be overcome. Despite recent developments, several issues concerning the deployment of IPbased IoT solutions on a large scale are still open. The fact that IoT is focused on data and information rather than on point-topoint communications suggests the adoption of solutions relying on ICN architectures. In this context, this work explores the ground concepts of ICN to develop a comprehensive vision of the principal requirements that should be met by an IoT-oriented ICN architecture. This vision is complemented with solutions to fundamental issues for the adoption of an ICN-based IoT. First, to ensure the freshness of the information while retaining the advantages of ICN’s in-network caching mechanisms. Second, to enable discovery functionalities in both local and large-scale domains. The proposed mechanisms are evaluated through both simulation and prototyping approaches, with results showcasing the feasibility of their adoption. Moreover, the outcomes of this work contribute to the development of new compelling concepts towards a full-fledged Named Network of Things.A forma como usamos a Internet tem vindo a evoluir desde a sua criação. Atualmente, os utilizadores estão mais interessados em aceder a conteúdos e serviços, com elevados requisitos em termos de largura de banda, segurança e mobilidade. Esta evolução desencadeou o desenvolvimento de novas arquiteturas de rede, visando os atuais, bem como os futuros, requisitos de utilização. As Redes Centradas à Informação (Information-Centric Networking - ICN) são um exemplo proeminente destas novas arquiteturas que, em vez de seguirem um modelo de comunicação centrado nos dispositivos terminais, centram as suas funções de rede em torno do próprio conteúdo. Paralelamente, novos cenários de utilização onde dispositivos inteligentes interagem entre si, e com outros elementos de rede, têm vindo a aparecer e constituem o que hoje conhecemos como a Internet das Coisas (Internet of Things - IoT ). É esperado que a IoT tenha um impacto significativo na economia e na sociedade. No entanto, promover a adoção em massa da IoT ainda requer que muitos desafios sejam superados. Apesar dos desenvolvimentos recentes, vários problemas relacionados com a adoção em larga escala de soluções de IoT baseadas no protocolo IP estão em aberto. O facto da IoT estar focada em dados e informação, em vez de comunicações ponto-a-ponto, sugere a adoção de soluções baseadas em arquiteturas ICN. Neste sentido, este trabalho explora os conceitos base destas soluções para desenvolver uma visão completa dos principais requisitos que devem ser satisfeitos por uma solução IoT baseada na arquitetura de rede ICN. Esta visão é complementada com soluções para problemas cruciais para a adoção de uma IoT baseada em ICN. Em primeiro lugar, assegurar que a informação seja atualizada e, ao mesmo tempo, manter as vantagens do armazenamento intrínseco em elementos de rede das arquiteturas ICN. Em segundo lugar, permitir as funcionalidades de descoberta não só em domínios locais, mas também em domínios de larga-escala. Os mecanismos propostos são avaliados através de simulações e prototipagem, com os resultados a demonstrarem a viabilidade da sua adoção. Para além disso, os resultados deste trabalho contribuem para o desenvolvimento de conceitos sólidos em direção a uma verdadeira Internet das Coisas baseada em Nomes.Programa Doutoral em Telecomunicaçõe

Mobile Ad-Hoc Networks

Being infrastructure-less and without central administration control, wireless ad-hoc networking is playing a more and more important role in extending the coverage of traditional wireless infrastructure (cellular networks, wireless LAN, etc). This book includes state-of the-art techniques and solutions for wireless ad-hoc networks. It focuses on the following topics in ad-hoc networks: vehicular ad-hoc networks, security and caching, TCP in ad-hoc networks and emerging applications. It is targeted to provide network engineers and researchers with design guidelines for large scale wireless ad hoc networks

Enhanced Forwarding Strategies in Information Centric Networking

Content Centric Networking (CCN), a Clean Slate architecture to Information Centric Networking (ICN) , uses new approaches to routing named content, achieving scalability, security and performance. This thesis proposes a design of an effective multi-path forwarding strategy and performs an evaluation of this strategy in a set of scenarios that consider large scale deployments. The evaluations show improved performance in terms of user application throughput, delays, adoptability and scalability against adverse conditions (such as differing background loads and mobility) compared to the originally proposed forwarding strategies. Secondly, this thesis proposes an analytical model based on Markov Modulated Rate Process (MMRP) to characterize multi-path data transfers in CCN. The results show a close resemblance in performance between the analytical model and the simulation model

A Cross-Layer Modification to the DSR Routing Protocol in Wireless Mesh Networks

A cross-layer modification to the DSR routing protocol that finds high throughput paths in WMNs has been introduced in this work. The Access Efficiency Factor (AEF) has been introduced in this modification as a local congestion avoidance metric for the DSR routing mechanism as an alternative to the hop count (Hc) metric. In this modification, the selected path is identified by finding a path with the highest minimum AEF (max_min_AEF) value. The basis of this study is to compare the performance of the Hc and max_min_AEF as routing metrics for the DSR protocol in WMNs using the OPNET modeler. Performance comparisons between max_min_AEF, Metric Path (MP), and the well known ETT metrics are also carried out in this work. The results of this modification suggest that employing the max_min_AEF as a routing metric outperforms the Hc, ETT, and MP within the DSR protocol in WMNs in terms of throughput. This is because the max_min_AEF is based upon avoiding directing traffic through congested nodes where significant packet loss is likely to occur. This throughput improvement is associated with an increment in the delay time due to the long paths taken to avoid congested regions. To overcome this drawback, a further modification to the routing discovery mechanism has been made by imposing a hop count limit (HCL) on the discovered paths. Tuning the HCL allows the network manager to tradeoff throughput against delay. The choice of congestion avoidance metric exhibits another shortcoming owing to its dependency on the packet size. It penalises the smaller packets over large ones in terms of path lengths. This has been corrected for by introducing a ModAEF metric that explicitly considers the size of the packet. The ModAEF metric includes a tuning factor that allows the operator determine the level of the weighting that should be applied to the packet size to correct for this dependence