60 research outputs found
Mobile Ad hoc Networking: Imperatives and Challenges
Mobile ad hoc networks (MANETs) represent complex distributed systems that comprise wireless mobile nodes that can freely and dynamically self-organize into arbitrary and temporary, "ad-hoc" network topologies, allowing people and devices to seamlessly internetwork in areas with no pre-existing communication infrastructure, e.g., disaster recovery environments. Ad hoc networking concept is not a new one, having been around in various forms for over 20 years. Traditionally, tactical networks have been the only communication networking application that followed the ad hoc paradigm. Recently, the introduction of new technologies such as the Bluetooth, IEEE 802.11 and Hyperlan are helping enable eventual commercial MANET deployments outside the military domain. These recent evolutions have been generating a renewed and growing interest in the research and development of MANET. This paper attempts to provide a comprehensive overview of this dynamic field. It first explains the important role that mobile ad hoc networks play in the evolution of future wireless technologies. Then, it reviews the latest research activities in these areas, including a summary of MANET\u27s characteristics, capabilities, applications, and design constraints. The paper concludes by presenting a set of challenges and problems requiring further research in the future
IEEE 802.21 in heterogeneous handover environments
Mestrado em Engenharia de Computadores e TelemĂĄticaO desenvolvimento das capacidades tecnolĂłgicas dos terminais mĂłveis, e das
infra-estruturas que os suportam, potenciam novos cenĂĄrios onde estes dispositivos
munidos com interfaces de diferentes tecnologias vagueiam entre
diferentes ambientes de conectividade. Ă assim necessĂĄrio providenciar meios
que facilitem a gestĂŁo de mobilidade, permitindo ao terminal ligar-se da melhor
forma (i.e., optando pela melhor tecnologia) em qualquer altura.
A norma IEEE 802.21 estĂĄ a ser desenvolvida pelo Institute of Electrical and
Electronics Engineers (IEEE) com o intuito de providenciar mecanismos e
serviços que facilitem e optimizem handovers de forma independente da tecnologia.
A norma 802.21 especifica assim um conjunto de mecanismos que
potenciarão cenårios como o descrito acima, tendo em conta a motivação e requerimentos
apresentados por arquitecturas de redes futuras, como as redes
de quarta geração (4G).
Esta dissertação apresenta uma anålise extensiva da norma IEEE 802.21, introduzindo
um conjunto de simulaçþes desenvolvidas para estudar o impacto
da utilização de mecanismos 802.21 em handovers controlados por rede, numa
rede de acesso mista composta por tecnologias 802.11 e 3G. Os resultados
obtidos permitiram verificar a aplicabilidade destes conceitos a ambientes de
próxima geração, motivando tambÊm uma descrição do desenho de integração
de mecanismos 802.21 a arquitecturas de redes de quarta geração.
ABSTRACT: The development of the technological capabilities of mobile terminals, and
the infra-structures that support them, enable new scenarios where these devices
using different technology interfaces roam in different connectivity environments.
This creates a need for providing the means that facilitate mobility
management, allowing the terminal to connect in the best way possible (i.e., by
choosing the best technology) at any time.
The IEEE 802.21 standard is being developed by the Institute of Electrical and
Electronics Engineers (IEEE) to provide mechanisms and services supporting
Media Independent Handovers. The 802.21 standard specifies a set of mechanisms
that enable scenarios like the one described above, considering the
motivation and requirements presented by future network architectures, such
as the ones from fourth generation networks (4G).
This thesis presents an extensive analysis of the IEEE 802.21 standard, introducing
a set of simulations developed for studying the impact of using 802.21
mechanisms in network controlled handovers, in a mixed access network composed
of 802.11 and 3G technologies. The obtained results allow the verification
of the applicability of these concepts into next generation environments,
also motivating the description of the design for integration of 802.21 mechanisms
to fourth generation networks
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Dynamic wireless mobile framework for distributed collaborative real-time information generation and control systems
Intelligent Transportation Systems (ITS) have only recently discovered the exciting possibilities in the nomadic and ubiquitous computing space to build a new generation of information systems by allowing the vehicle to act both as a carrier and consumer of wireless (and thus omnipresent) information. Wide deployment of such ITS systems may eventually allow for more dynamic and efficient transportation systems, which can contribute in several ways towards greater economic growth whilst respecting environmental sustainability. A great number of researchers have dedicated considerable time and resources to tackling traffic related issues by utilising the new wireless capabilities enabled by ITS; such initiatives cover a wide range of applications such as safety, knowledge sharing and infotainment. Indicative of the extent of such efforts is the plethora of research projects initiated by many national and multi-national organisations such as the EU Framework Programme for Research and Technological Development. To achieve their goals, proposed solutions from such organisations depend on the development and deployment of intelligent wireless mobile communication systems, where data dissemination issues make the prospect of efficient and effective communication a challenging proposition. Presently, Car-to-Car and Car-to-Infrastructure communications are two distinct avenues that make possible efficient and reliable delivery of messages via direct radio links in traffic areas. In all cases, high quality of communication performance is desirable for a communication system composed mostly of roaming participants; such a system needs to be dynamic, flexible and infrastructure-less. Consequently, Mobile Ad hoc Network (MANET)-based networks are a natural fit to ITS
Distributed Algorithms for Location Based Services
Real-time localization services are some of the most challenging and interesting mobile broadband applications in the Location Based Services (LBS) world. They are gaining more and more importance for a broad range of applications, such as road/highway monitoring, emergency management, social networking, and advertising.
This Ph.D. thesis focuses on the problem of defining a new category of decentralized peer-to-peer (P2P) algorithms for LBS. We aim at defining a P2P overlay where each participant can efficiently retrieve node and resource information (data or services) located near any chosen geographic position. The idea is that the responsibility and the required resources for maintaining information about position of active users are properly distributed among nodes, for which a change in the set of participants causes only a minimal amount of disruption without reducing the quality of provided services. In this thesis we will assess the validity of the proposed model through a formal analysis of the routing protocol and a detailed simulative investigation of the designed overlay. We will depict a complete picture of involved parameters, how they affect the performance and how they can be configured to adapt the protocol to the requirements of several location based applications. Furthermore we will present two application scenarios (a smartphone based Traffic Information System and a large information management system for a SmartCity) where the designed protocol has been simulated and evaluated, as well as the first prototype of a real implementation of the overlay using both traditional PC nodes and Android mobile devices
Mobility management in IP-Based Networks
Mobile communication networks experience a tremendous development clearly
evident from the wide variety of new applications way beyond classical
phone services. The tremendous success of the Internet along with the
demand for always-on connectivity has triggered the development of All-IP
mobile communication networks. Deploying these networks requires, however,
overcoming many challenges. One of the main challenges is how to manage the
mobility between cells connecting through an IP core in a way that
satisfies real-time requirements. This challenge is the focus of this
dissertation. This dissertation delivers an in-depth analysis of the
mobility management issue in IP-based mobile communication networks. The
advantages and disadvantages of various concepts for mobility management in
different layers of the TCP/IP protocol stack are investigated. In
addition, a classification and brief description of well-known mobility
approaches for each layer are provided. The analysis concludes that network
layer mobility management solutions seem to be best suited to satisfy the
requirements of future All-IP networks. The dissertation, therefore,
provides a comprehensive review of network layer mobility management
protocols along with a discussion of their pros and cons. Analyses of
previous work in this area show that the proposed techniques attempt to
improve the performance by making constraints either on access networks
(e.g. requiring a hierarchical topology, introducing of intermediate nodes,
etc.) or mobile terminals (e.g. undertaking many measurements, location
tracking, etc.). Therefore, a new technique is required that completes
handoffs quickly without affecting the end-to-end performance of ongoing
applications. In addition, it should place restrictions neither on access
networks nor on mobiles. To meet these requirements, a new solution named
Mobile IP Fast Authentication protocol (MIFA) is proposed. MIFA provides
seamless mobility and advances the state of the art. It utilizes the fact
that mobiles movements are limited to a small set of neighboring subnets.
Thus, contacting these neighbors and providing them in advance with
sufficient data related to the mobiles enable them to fast re-authenticate
the mobiles after the handoff. The dissertation specifies the proposal for
both IPv4 and IPv6. The specification of MIFA considers including many
error recovery mechanisms to cover the most likely failures. Security
considerations are studied carefully as well. MIFA does not make any
restrictions on the network topology. It makes use of layer 2 information
to optimize the performance and works well even if such information is not
available.In order to analyze our new proposal in comparison to a wide
range of well-known mobility management protocols, this dissertation
proposes a generic mathematical model that supports the evaluation of
figures such as average handoff latency, average number of dropped packets,
location update cost and packet delivery cost. The generic model considers
dropped control messages and takes different network topologies and
mobility scenarios into account. This dissertation also validates the
generic mathematical model by comparing its results to simulation results
as well as results of real testbeds under the same assumptions. The
validation proves that the generic model delivers an accurate evaluation of
the performance in low-loaded networks. The accuracy of the model remains
acceptable even under high loads. The validation also shows that simulation
results lie in a range of 23 %, while results of real testbeds lie in a
range of 30 % of the generic model?s results. To simplify the analysis
using the generic mathematical model, 4 new tools are developed in the
scope of this work. They automate the parameterization of mobility
protocols, network topologies and mobility scenarios. This dissertation
also evaluates the new proposal in comparison to well-known approaches
(e.g. Mobile IP, Handoff-Aware Wireless Access Internet Infrastructure
(HAWAII), etc.) by means of the generic mathematical model as well as
simulation studies modeled in the Network Simulator 2. The evaluation shows
that MIFA is a very fast protocol. It outperforms all studied protocols
with respect to the handoff latency and number of dropped packets per
handoff. MIFA is suitable for low as well as high speeds. Moreover, there
is no significant impact of the network topology on its performance. A main
advantage of MIFA is its robustness against the dropping of control
messages. It remains able to achieve seamless handoffs even if a dropping
occurs. The performance improvement is achieved, however, at the cost of
introducing new control messages mainly to distribute data concerning
mobile terminals to neighbor subnets. This results in more location update
cost than that resulting from the other mobility management protocols
studied. Due to excluding any constraints on the network topology, MIFA
generates the same packet delivery cost as Mobile IP and less than other
protocols.An additional focus of this dissertation is the development of an
adaptive eLearning environment that personalizes eLearning contents
conveying the topics of this dissertation depending on users?
characteristics. The goal is to allow researchers to quickly become
involved in research on mobility management, while learners such as
students are able to gain information on the topics without excess detail.
Analyses of existing eLearning environments show a lack of adaptivity
support. Existing environments focus mainly on adapting either the
navigation or the presentation of contents depending on one or more
selected users? characteristics. There is no environment that supports both
simultaneously. In addition, many user characteristics are disregarded
during the adaptivity process. Thus, there is a need to develop a new
adaptive eLearning environment able to eliminate these drawbacks. This
dissertation, therefore, designs a new Metadata-driven Adaptive eLearning
Environment (MAeLE). MAeLE generates personalized eLearning courses along
with building an adequate navigation at run-time. Adaptivity depends mainly
on providing contents with their describing metadata, which are stored in a
separate database, thus enabling reusing of eLearning contents. The
relation between the metadata that describe contents and those describing
learners are defined accurately, which enables a dynamic building of
personalized courses at run-time. A prototype for MAeLE is provided in this
dissertation as well
Connecting Vehicles to the Internet - Strategic Data Transmission for Mobile Nodes using Heterogeneous Wireless Networks
With the advent of autonomous driving, the driving experience for users of connected vehicles changes, as they may enjoy their travel time with entertainment, or work productively.
In our modern society, both require a stable Internet access. However, future mobile networks are not expected to be able to satisfy application Quality of Service (QoS) requirements as needed, e.g. during rush hours. To address this problem, this dissertation investigates data transmission strategies that exploit the potential of using a heterogeneous wireless network environment. To this end, we combine two so far distinct concepts, firstly, network selection and, secondly, transmission time selection, creating a joint time-network selection strategy. It allows a vehicle to plan delay-tolerant data transmissions ahead, favoring transmission opportunities with the best prospective flow-network matches.
In this context, our first contribution is a novel rating model for perceived transmission quality, which assesses transmission opportunities with respect to application QoS requirement violations, traded off by monetary cost. To enable unified assessment of all data transmissions, it generalizes existing specialized rating models from network selection and transmission time selection and extends them with a novel throughput requirement model. Based on that, we develop a novel joint time-network selection strategy, Joint Transmission Planning (JTP), as our second contribution, planning optimized data transmissions within a defined time horizon. We compare its transmission quality to that of three predominant state-of-the-art transmission strategies, revealing that JTP outperforms the others significantly by up to 26%. Due to extensive scenario variation, we discover broad stability of JTP reaching 87-91% of the optimum.
As JTP is a planning approach relying on prediction data, the transmission quality is strongly impaired when executing its plans under environmental changes. To mitigate this impact, we develop a transmission plan adaptation as our third contribution, modifying the planned current transmission online in order to comply with the changes. Even under strong changes of the vehicle movement and the network environment, it sustains 57%, respectively 36%, of the performance gain from planning.
Finally, we present our protocol Mobility management for Vehicular Networking (MoVeNet), pooling available network resources of the environment to enable flexible packet dispatching without breaking connections. Its distributed architecture provides broad scalability and robustness against node failures. It complements control mechanisms that allow a demand-based and connection-specific trade-off between overhead and latency. Less than 9 ms additional round trip time in our tests, instant handover and 0 to 4 bytes per-packet overhead prove its efficiency.
Employing the presented strategies and mechanisms jointly, users of connected vehicles and other mobile devices can significantly profit from the demonstrated improvements in application QoS satisfaction and reduced monetary cost
Flexible Application-Layer Multicast in Heterogeneous Networks
This work develops a set of peer-to-peer-based protocols and extensions in order to provide Internet-wide group communication. The focus is put to the question how different access technologies can be integrated in order to face the growing traffic load problem. Thereby, protocols are developed that allow autonomous adaptation to the current network situation on the one hand and the integration of WiFi domains where applicable on the other hand
Multi-layer traffic control for wireless networks
Le reti Wireless LAN, cosĂŹ come definite dallo standard IEEE 802.11, garantiscono connettivitĂ senza fili nei cosiddetti âhot-spotâ (aeroporti, hotel, etc.), nei campus universitari, nelle intranet aziendali e nelle abitazioni. In tali scenari, le WLAN sono denotate come âad infrastrutturaâ nel senso che la copertura della rete è basata sulla presenza di un âAccess Pointâ che fornisce alle stazioni mobili lâaccesso alla rete cablata. Esiste un ulteriore approccio (chiamato âad-hocâ) in cui le stazioni mobili appartenenti alla WLAN comunicano tra di loro senza lâausilio dellâAccess Point.
Le Wireless LAN tipicamente sono connesse alla rete di trasporto (che essa sia Internet o una Intranet aziendale) usando unâinfrastruttura cablata. Le reti wireless Mesh ad infrastruttura (WIMN) rappresentano unâalternativa valida e meno costosa alla classica infrastruttura cablata. A testimonianza di quanto appena affermato vi è la comparsa e la crescita sul mercato di diverse aziende specializzate nella fornitura di infrastrutture di trasporto wireless e il lancio di varie attivitĂ di standardizzazione (tra cui spicca il gruppo 802.11s).
La facilitĂ di utilizzo, di messa in opera di una rete wireless e i costi veramente ridotti hanno rappresentato fattori critici per lo straordinario successo di tale tecnologia. Di conseguenza possiamo affermare che la tecnologia wireless ha modificato lo stile di vita degli utenti, il modo di lavorare, il modo di passare il tempo libero (video conferenze, scambio foto, condivisione di brani musicali, giochi in rete, messaggistica istantanea ecc.).
Dâaltro canto, lo sforzo per garantire lo sviluppo di reti capaci di supportare servizi dati ubiqui a velocitĂ di trasferimento elevate è strettamente legato a numerose sfide tecniche tra cui: il supporto per lâhandover tra differenti tecnologie (WLAN/3G), la certezza di accesso e autenticazione sicure, la fatturazione e lâaccounting unificati, la garanzia di QoS ecc.
LâattivitĂ di ricerca svolta nellâarco del Dottorato si è focalizzata sulla definizione di meccanismi multi-layer per il controllo del traffico in reti wireless. In particolare, nuove soluzioni di controllo del traffico sono state realizzate a differenti livelli della pila protocollare (dallo strato data-link allo strato applicativo) in modo da fornire: funzionalitĂ avanzate (autenticazione sicura, differenziazione di servizio, handover trasparente) e livelli soddisfacenti di QualitĂ del Servizio.
La maggior parte delle soluzioni proposte in questo lavoro di tesi sono state implementate in test-bed reali.
Questo lavoro riporta i risultati della mia attivitĂ di ricerca ed è organizzato nel seguente modo: ogni capitolo presenta, ad uno specifico strato della pila protocollare, un meccanismo di controllo del traffico con lâobiettivo di risolvere le problematiche presentate precedentemente.
I Capitoli 1 e 2 fanno riferimento allo strato di Trasporto ed investigano il problema del mantenimento della fairness per le connessioni TCP. Lâunfairness TCP conduce ad una significativa degradazione delle performance implicando livelli non soddisfacenti di QoS. Questi capitoli descrivono lâattivitĂ di ricerca in cui ho impiegato il maggior impegno durante gli studi del dottorato. Nel capitolo 1 viene presentato uno studio simulativo delle problematiche di unfairness TCP e vengono introdotti due possibili soluzioni basate su rate-control. Nel Capitolo 2 viene derivato un modello analitico per la fairness TCP e si propone uno strumento per la personalizzazione delle politiche di fairness. Il capitolo 3 si focalizza sullo strato Applicativo e riporta diverse soluzioni di controllo del traffico in grado di garantire autenticazione sicura in scenari di roaming tra provider wireless. Queste soluzioni rappresentano parte integrante del framework UniWireless, un testbed nazionale sviluppato nellâambito del progetto TWELVE.
Il capitolo 4 descrive, nuovamente a strato Applicativo, una soluzione (basata su SIP) per la gestione della mobilitĂ degli utenti in scenari di rete eterogenei ovvero quando diverse tecnologie di accesso radio sono presenti (802.11/WiFi, Bluetooth, 2.5G/3G).
Infine il Capitolo 5 fa riferimento allo strato Data-Link presentando uno studio preliminare di un approccio per il routing e il load-balancing in reti Mesh infrastrutturate.Wireless LANs, as they have been defined by the IEEE 802.11 standard, are shared media enabling connectivity in the so-called âhot-spotsâ (airports, hotel lounges, etc.), university campuses, enterprise intranets, as well as âin-homeâ for home internet access.
With reference to the above scenarios, WLANs are commonly denoted as âinfra-structuredâ in the sense that WLAN coverage is based on âAccess Pointsâ which provide the mobile stations with access to the wired network. In addition to this approach, there exists also an âad-hocâ mode to organize WLANs where mobile stations talk to each other without the need of Access Points.
Wireless LANs are typically connected to the wired backbones (Internet or corporate intranets) using a wired infrastructure. Wireless Infrastructure Mesh Networks (WIMN) may represent a viable and cost-effective alternative to this traditional wired approach. This is witnessed by the emergence and growth of many companies specialized in the provisioning of wireless infrastructure solutions, as well as the launch of standardization activities (such as 802.11s).
The easiness of deploying and using a wireless network, and the low deployment costs have been critical factors in the extraordinary success of such technology. As a logical consequence, the wireless technology has allowed end users being connected everywhere â every time and it has changed several things in peopleâs lifestyle, such as the way people work, or how they live their leisure time (videoconferencing, instant photo or music sharing, network gaming, etc.).
On the other side, the effort to develop networks capable of supporting ubiquitous data services with very high data rates in strategic locations is linked with many technical challenges including seamless vertical handovers across WLAN and 3G radio technologies, security, 3G-based authentication, unified accounting and billing, consistent QoS and service provisioning, etc.
My PhD research activity have been focused on multi-layer traffic control for Wireless LANs. In particular, specific new traffic control solutions have been designed at different layers of the protocol stack (from the link layer to the application layer) in order to guarantee i) advanced features (secure authentication, service differentiation, seamless handover) and ii) satisfactory level of perceived QoS. Most of the proposed solutions have been also implemented in real testbeds.
This dissertation presents the results of my research activity and is organized as follows: each Chapter presents, at a specific layer of the protocol stack, a traffic control mechanism in order to address the introduced above issues.
Chapter 1 and Charter 2 refer to the Transport Layer, and they investigate the problem of maintaining fairness for TCP connections. TCP unfairness may result in significant degradation of performance leading to users perceiving unsatisfactory Quality of Service. These Chapters describe the research activity in which I spent the most significant effort. Chapter 1 proposes a simulative study of the TCP fairness issues and two different solutions based on Rate Control mechanism. Chapter 2 illustrates an analytical model of the TCP fairness and derives a framework allowing wireless network providers to customize fairness policies.
Chapter 3 focuses on the Application Layer and it presents new traffic control solutions able to guarantee secure authentication in wireless inter-provider roaming scenarios. These solutions are an integral part of the UniWireless framework, a nationwide distributed Open Access testbed that has been jointly realized by different research units within the TWELVE national project.
Chapter 4 describes again an Application Layer solution, based on Session Initiation Protocol to manage user mobility and provide seamless mobile multimedia services in a heterogeneous scenario where different radio access technologies are used (802.11/WiFi, Bluetooth, 2.5G/3G networks).
Finally Chapter 5 refers to the Data Link Layer and presents a preliminary study of a general approach for routing and load balancing in Wireless Infrastructure Mesh Network. The key idea is to dynamically select routes among a set of slowly changing alternative network paths, where paths are created through the reuse of classical 802.1Q multiple spanning tree mechanisms
Asioiden Internetin tietoturva: ratkaisuja, standardeja ja avoimia ongelmia
Internet of Things (IoT) extends the Internet to our everyday objects, which enables new kind of applications and services. These IoT applications face demanding technical challenges: the number of âthingsâ or objects can be very large, they can be very con-strained devices, and may need to operate on challenging and dynamic environments. However, the architecture of todayâs Internet is based on many legacy protocols and technology that were not originally designed to support features like mobility or the huge and growing number of objects the Internet consists of today. Similarly, many security features of todayâs Internet are additional layers built to fill up flaws in the un-derlying design. Fulfilling new technical requirements set by IoT applications requires efficient solutions designed for the IoT use from the ground up. Moreover, the imple-mentation of this new IoT technology requires interoperability and integration with tra-ditional Internet. Due to considerable technical challenges, the security is an often over-looked aspect in the emerging new IoT technology.
This thesis surveys general security requirements for the entire field of IoT applica-tions. Out of the large amount of potential applications, this thesis focuses on two major IoT application fields: wireless sensor networks and vehicular ad-hoc networks. The thesis introduces example scenarios and presents major security challenges related to these areas. The common standards related to the areas are examined in the security perspective. The thesis also examines research work beyond the area of standardization in an attempt to find solutions to unanswered security challenges. The thesis aims to give an introduction to the security challenges in the IoT world and review the state of the security research through these two major IoT areas
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