167 research outputs found
A study of the Destination Guided Mobility models.
Mobility models play a critical role in the simulation studies of Mobile Ad hoc Networks (MANETs). They greatly influence the performance of MANET routing protocols. For MANET simulations, random mobility models have been used in nearly all research studies in the past. In recent times, several studies have criticised the use of random mobility models in the performance studies of MANETs for the lack of realism in modelling mobility. Therefore, questions have been raised regarding the credibility of MANET simulation studies. Realism and simplicity are two attractive properties of mobility models achieving both together in modelling mobility has been a challenging task. Recently, a framework of mobility models called Destination Guided Mobility (DGM) models for MANETs with a basic software tool was proposed. This framework can be used to develop several simple DGM models with improved realism. This thesis is primarily interested in studying DGM models for their suitability in modelling mobility in various MANET scenarios. Our study requires a suitable simulation testbed for DGM models. Designing such a tool, referred to as DGMGen, with suitable functionality to study DGM models is the secondary objective of this thesis. More specifically, after the design and implementation of DGMGen, we study: i) the generality of the DGM models by modelling different real world scenarios ii) the connectivity analysis of three basic DGM models in comparison with the widely used Random Waypoint (RWP) mobility model iii) how to model a real life scenario using DGM models, based on the trace collected from that scenario and iv) the impact of DGM models on the Ad hoc On-demand Distance Vector (AODV) routing protocol using NS2. Our study shows that i) the DGM framework is powerful in capturing various MANET scenarios simply and more accurately, ii) DGM models confirm higher level connectivity prevailed in most real world scenarios, iii) DGM models can generate approximately the similar trace based on the insights of a real traceThe original print copy of this thesis may be available here: http://wizard.unbc.ca/record=b180785
Cross-layer signalling and middleware: a survey for inelastic soft real-time applications in MANETs
This paper provides a review of the different cross-layer design and protocol tuning approaches that may be used to meet a growing need to support inelastic soft real-time streams in MANETs. These streams are characterised by critical timing and throughput requirements and low packet loss tolerance levels. Many cross-layer approaches exist either for provision of QoS to soft real-time streams in static wireless networks or to improve the performance of real and non-real-time transmissions in MANETs. The common ground and lessons learned from these approaches, with a view to the potential provision of much needed support to real-time applications in MANETs, is therefore discussed
Cognition-Based Networks: A New Perspective on Network Optimization Using Learning and Distributed Intelligence
IEEE Access
Volume 3, 2015, Article number 7217798, Pages 1512-1530
Open Access
Cognition-based networks: A new perspective on network optimization using learning and distributed intelligence (Article)
Zorzi, M.a , Zanella, A.a, Testolin, A.b, De Filippo De Grazia, M.b, Zorzi, M.bc
a Department of Information Engineering, University of Padua, Padua, Italy
b Department of General Psychology, University of Padua, Padua, Italy
c IRCCS San Camillo Foundation, Venice-Lido, Italy
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Abstract
In response to the new challenges in the design and operation of communication networks, and taking inspiration from how living beings deal with complexity and scalability, in this paper we introduce an innovative system concept called COgnition-BAsed NETworkS (COBANETS). The proposed approach develops around the systematic application of advanced machine learning techniques and, in particular, unsupervised deep learning and probabilistic generative models for system-wide learning, modeling, optimization, and data representation. Moreover, in COBANETS, we propose to combine this learning architecture with the emerging network virtualization paradigms, which make it possible to actuate automatic optimization and reconfiguration strategies at the system level, thus fully unleashing the potential of the learning approach. Compared with the past and current research efforts in this area, the technical approach outlined in this paper is deeply interdisciplinary and more comprehensive, calling for the synergic combination of expertise of computer scientists, communications and networking engineers, and cognitive scientists, with the ultimate aim of breaking new ground through a profound rethinking of how the modern understanding of cognition can be used in the management and optimization of telecommunication network
Reputation systems and secure communication in vehicular networks
A thorough review of the state of the art will reveal that most VANET applications rely on Public Key Infrastructure (PKI), which uses user certificates managed by a Certification Authority (CA) to handle security. By doing so, they constrain the ad-hoc nature of the VANET imposing a frequent connection to the CA to retrieve the Certificate Revocation List (CRL) and requiring some degree of roadside infrastructure to achieve that connection. Other solutions propose the usage of group signatures where users organize in groups and elect a group manager. The group manager will need to ensure that group members do not misbehave, i.e., do not spread false information, and if they do punish them, evict them from the group and report them to the
CA; thus suffering from the same CRL retrieval problem.
In this thesis we present a fourfold contribution to improve security in VANETs. First and foremost, Chains of Trust describes a reputation system where users disseminate Points of Interest (POIs) information over the network while their privacy remains protected. It uses asymmetric cryptography and users are responsible for the generation of their own pair of public and
private keys. There is no central entity which stores the information users input into the system; instead, that information is kept distributed among the vehicles that make up the network. On top of that, this system requires no roadside infrastructure. Precisely, our main objective with Chains of Trust was to show that just by relying on people¿s driving habits and the sporadic nature of their encounters with other drivers a successful reputation system could be built.
The second contribution of this thesis is the application simulator poiSim. Many¿s the time a new VANET application is presented and its authors back their findings using simulation results from renowned networks simulators like ns-2. The major issue with network simulators is that they were not designed with that purpose in mind and handling simulations with hundreds of nodes requires a massive processing power. As a result, authors run small simulations (between 50 and 100 nodes) with vehicles that move randomly in a squared area instead of using real maps, which rend unrealistic results. We show that by building tailored application simulators we can obtain more realistic results. The application simulator poiSim processes a realistic mobility trace produced by a Multi-agent Microscopic Traffic Simulator developed at ETH Zurich, which accurately describes the mobility patterns of 259,977 vehicles over regional maps of Switzerland for 24 hours. This simulation runs on a desktop PC and lasts approximately 120 minutes.
In our third contribution we took Chains of Trust one step further in the protection of user privacy to develop Anonymous Chains of Trust. In this system users can temporarily exchange their identity with other users they trust, thus making it impossible for an attacker to know in all certainty who input a particular piece of information into the system. To the best of our knowledge, this is the first time this technique has been used in a reputation system.
Finally, in our last contribution we explore a different form of communication for VANETs. The vast majority of VANET applications rely on the IEEE 802.11p/Wireless Access in Vehicular Environments (WAVE) standard or some other form of radio communication. This poses a security risk if we consider how vulnerable radio transmission is to intentional jamming and
natural interferences: an attacker could easily block all radio communication in a certain area if his transmitter is powerful enough. Visual Light Communication (VLC), on the other hand, is resilient to jamming over a wide area because it relies on visible light to transmit information and ,unlike WAVE, it has no scalability problems. In this thesis we show that VLC is a secure and valuable form of communication in VANETs
Design and evaluation of a self-configuring wireless mesh network architecture
Wireless network connectivity plays an increasingly important role in supporting our everyday private and professional lives. For over three decades, self-organizing wireless multi-hop ad-hoc networks have been investigated as a decentralized replacement for the traditional forms of wireless networks that rely on a wired infrastructure. However, despite the tremendous efforts of the international wireless research community and widespread availability of devices that are able to support these networks, wireless ad-hoc networks are hardly ever used.
In this work, the reasons behind this discrepancy are investigated. It is found that several basic theoretical assumptions on ad-hoc networks prove to be wrong when solutions are deployed in reality, and that several basic functionalities are still missing. It is argued that a hierarchical wireless mesh network architecture, in which specialized, multi-interfaced mesh nodes form a reliable multi-hop wireless backbone for the less capable end-user clients is an essential step in bringing the ad-hoc networking concept one step closer to reality.
Therefore, in a second part of this work, algorithms increasing the reliability and supporting the deployment and management of these wireless mesh networks are developed, implemented and evaluated, while keeping the observed limitations and practical considerations in mind. Furthermore, the feasibility of the algorithms is verified by experiment.
The performance analysis of these protocols and the ability to deploy the developed algorithms on current generation off-the-shelf hardware indicates the successfulness of the followed research approach, which combines theoretical considerations with practical implementations and observations. However, it was found that there are also many pitfalls to using real-life implementation as a research technique. Therefore, in the last part of this work, a methodology for wireless network research using real-life implementation is developed, allowing researchers to generate more reliable protocols and performance analysis results with less effort
Reliability and Efficiency of Vehicular Network Applications
The DSRC/WAVE initiative is forecast to enable a plethora of applications, classified in two broad types of safety and non-safety applications. In the former type, the reliability performance is of tremendous prominence while, in the latter case, the efficiency of information dissemination is the key driving factor. For safety applications, we adopt a systematic approach to analytically investigate the reliability of the communication system in a symbiotic relationship with the host system comprising a vehicular traffic system and radio propagation environment. To this aim, the¬ interference factor is identified as the central element of the symbiotic relationship. Our approach to the investigation of interference and its impacts on the communication reliability departs from previous studies by the degree of realism incorporated in the host system model. In one dimension, realistic traffic models are developed to describe the vehicular traffic behaviour. In a second dimension, a realistic radio propagation model is employed to capture the unique signal propagation aspects of the host system. We address the case of non-safety applications by proposing a generic framework as a capstone architecture for the development of new applications and the efficiency evaluation of existing ones. This framework, while being independent from networking technology, enables accurate characterization of the various information dissemination tasks that a node performs in cooperation with others. As the central element of the framework, we propose a game theoretic model to describe the interaction of meeting nodes aiming to exchange information of mutual or social interests. An adaptive mechanism is designed to enable a mobile node to measure the social significance of various information topics, which is then used by the node to prioritize the forwarding of information objects
Cross-layer optimizations in multi-hop ad hoc networks
Unlike traditional wireless networks, characterized by the presence of last-mile, static and
reliable infrastructures, Mobile ad Hoc Networks (MANETs) are dynamically formed by
collections of mobile and static terminals that exchange data by enabling each other's
communication. Supporting multi-hop communication in a MANET is a challenging
research area because it requires cooperation between different protocol layers (MAC,
routing, transport). In particular, MAC and routing protocols could be considered
mutually cooperative protocol layers. When a route is established, the exposed and
hidden terminal problems at MAC layer may decrease the end-to-end performance
proportionally with the length of each route. Conversely, the contention at MAC layer
may cause a routing protocol to respond by initiating new routes queries and routing table
updates.
Multi-hop communication may also benefit the presence of pseudo-centralized virtual
infrastructures obtained by grouping nodes into clusters. Clustering structures may
facilitate the spatial reuse of resources by increasing the system capacity: at the same
time, the clustering hierarchy may be used to coordinate transmissions events inside the
network and to support intra-cluster routing schemes. Again, MAC and clustering
protocols could be considered mutually cooperative protocol layers: the clustering
scheme could support MAC layer coordination among nodes, by shifting the distributed
MAC paradigm towards a pseudo-centralized MAC paradigm. On the other hand, the
system benefits of the clustering scheme could be emphasized by the pseudo-centralized
MAC layer with the support for differentiated access priorities and controlled contention.
In this thesis, we propose cross-layer solutions involving joint design of MAC, clustering
and routing protocols in MANETs.
As main contribution, we study and analyze the integration of MAC and clustering
schemes to support multi-hop communication in large-scale ad hoc networks. A novel
clustering protocol, named Availability Clustering (AC), is defined under general nodes'
heterogeneity assumptions in terms of connectivity, available energy and relative
mobility. On this basis, we design and analyze a distributed and adaptive MAC protocol,
named Differentiated Distributed Coordination Function (DDCF), whose focus is to
implement adaptive access differentiation based on the node roles, which have been
assigned by the upper-layer's clustering scheme. We extensively simulate the proposed
clustering scheme by showing its effectiveness in dominating the network dynamics,
under some stressing mobility models and different mobility rates. Based on these results,
we propose a possible application of the cross-layer MAC+Clustering scheme to support
the fast propagation of alert messages in a vehicular environment.
At the same time, we investigate the integration of MAC and routing protocols in large
scale multi-hop ad-hoc networks. A novel multipath routing scheme is proposed, by
extending the AOMDV protocol with a novel load-balancing approach to concurrently
distribute the traffic among the multiple paths. We also study the composition effect of a
IEEE 802.11-based enhanced MAC forwarding mechanism called Fast Forward (FF),
used to reduce the effects of self-contention among frames at the MAC layer. The
protocol framework is modelled and extensively simulated for a large set of metrics and
scenarios.
For both the schemes, the simulation results reveal the benefits of the cross-layer
MAC+routing and MAC+clustering approaches over single-layer solutions
A Survey on Wireless Sensor Network Security
Wireless sensor networks (WSNs) have recently attracted a lot of interest in
the research community due their wide range of applications. Due to distributed
nature of these networks and their deployment in remote areas, these networks
are vulnerable to numerous security threats that can adversely affect their
proper functioning. This problem is more critical if the network is deployed
for some mission-critical applications such as in a tactical battlefield.
Random failure of nodes is also very likely in real-life deployment scenarios.
Due to resource constraints in the sensor nodes, traditional security
mechanisms with large overhead of computation and communication are infeasible
in WSNs. Security in sensor networks is, therefore, a particularly challenging
task. This paper discusses the current state of the art in security mechanisms
for WSNs. Various types of attacks are discussed and their countermeasures
presented. A brief discussion on the future direction of research in WSN
security is also included.Comment: 24 pages, 4 figures, 2 table
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