20 research outputs found
Istunnon aloitusprotokollaan pohjautuvat mobiilivertaisverkot
This work continues on my Master's Thesis work done between July 2005 and January 2006. In my Master's Thesis, we presented how a mobile peer-to-peer file-sharing application can be implemented using the Session Initiation Protocol (SIP) as the underlying signaling protocol.
The main objective of this thesis is to evaluate what kind of special requirements mobile environment poses for peer-to-peer application design, and present how peer-to-peer based services can be efficiently realized in next-generation mobile networks by using SIP with some enhancements as the peer-to-peer signaling protocol.
This thesis is divided into two parts. In the first part, we present different peer-to-peer architectures and search algorithms, and evaluate their suitability for mobile use. We also review some mobile peer-to-peer middleware and file-sharing applications. Then, in the second part, we present our hybrid mobile peer-to-peer architecture consisting of a Symbian based mobile client and a SIP Application Server based super-peer.
Key findings of this thesis are that the mobile peer-to-peer application based on SIP signaling and hybrid peer-to-peer architecture is suitable for mobile use as it minimizes overhead in mobile nodes and allows mobile operator to have control on its users in multi-operator environment. Also, the performance of the application satisfies user requirements.TĂ€mĂ€ työ on jatkoa diplomityölleni, joka tehtiin HeinĂ€kuu 2005 â Tammikuu 2006 vĂ€lisenĂ€ aikana. DiplomityössĂ€ni esitimme kuinka mobiilivertaisverkkosovellus voidaan toteuttaa kĂ€yttĂ€en Session Initiation Protocol (SIP) protokollaa allaolevana signalointiprotokollana.
TÀmÀn työn pÀÀtavoite on selvittÀÀ, mitÀ erikoisvaatimuksia mobiiliympÀristö vertaisverkkosovelluksen suunnittelulle asettaa sekÀ kuinka vertaisverkkopalveluita voidaan tehokkaasti toteuttaa seuraavan sukupolven mobiiliverkoissa kÀyttÀmÀllÀ laajennettua SIP protokollaa sovelluksen merkinantoprotokollana.
TÀmÀ työ on jaettu kahteen osaan. EnsimmÀisessa osassa kÀsittelemme eri vertaisverkkoarkkitehtuureja ja hakualgoritmeja, sekÀ arvioimme nÀiden sopivuutta mobiilikÀyttöön. KÀymme myös lÀpi joitain mobiilivertaisverkkotiedostojako-ohjelmia sekÀ middleware-alustoja. Työn toisessa osassa esittelemme oman mobiilivertaisverkkoarkkitehtuurimme, joka koostuu Symbian mobiilisovelluksesta sekÀ SIP sovelluspalvelin super-peer solmusta.
Tutkimuksen pÀÀlöydökset ovat seuraavat: SIP protokollaa kÀyttÀvÀ hybridi-vertaisverkkosovellus toimii hyvin matkapuhelinympÀristössÀ, koska se minimoi puhelimeen kohdistuvan rasituksen ja tekee mahdolliseksi matkapuhelinoperaattorin hallita sovelluksen kÀyttÀjiÀ myöskin monioperaattoriympÀristössÀ. TÀmÀn lisÀksi ohjelmiston suorituskyky tÀyttÀÀ kÀytÀjien sille asettamat vaatimukset
A semantic approach for scalable and self-organized context-aware systems
Ph.DDOCTOR OF PHILOSOPH
Distributed resource discovery: architectures and applications in mobile networks
As the amount of digital information and services increases, it becomes increasingly important to be able to locate the desired content. The purpose of a resource discovery system is to allow available resources (information or services) to be located using a user-defined search criterion. This work studies distributed resource discovery systems that guarantee all existing resources to be found and allow a wide range of complex queries. Our goal is to allocate the load uniformly between the participating nodes, or alternatively to concentrate the load in the nodes with the highest available capacity.
The first part of the work examines the performance of various existing unstructured architectures and proposes new architectures that provide features especially valuable in mobile networks. To reduce the network traffic, we use indexing, which is particularly useful in scenarios, where searches are frequent compared to resource modifications. The ratio between the search and update frequencies determines the optimal level of indexing. Based on this observation, we develop an architecture that adjusts itself to changing network conditions and search behavior while maintaining optimal indexing. We also propose an architecture based on large-scale indexing that we later apply to resource sharing within a user group. Furthermore, we propose an architecture that relieves the topology constraints of the Parallel Index Clustering architecture. The performance of the architectures is evaluated using simulation.
In the second part of the work we apply the architectures to two types of mobile networks: cellular networks and ad hoc networks. In the cellular network, we first consider scenarios where multiple commercial operators provide a resource sharing service, and then a scenario where the users share resources without operator support. We evaluate the feasibility of the mobile peer-to-peer concept using user opinion surveys and technical performance studies. Based on user input we develop access control and group management algorithms for peer-to-peer networks. The technical evaluation is performed using prototype implementations. In particular, we examine whether the Session Initiation Protocol can be used for signaling in peer-to-peer networks. Finally, we study resource discovery in an ad hoc network. We observe that in an ad hoc network consisting of consumer devices, the capacity and mobility among nodes vary widely. We utilize this property in order to allocate the load to the high-capacity nodes, which serve lower-capacity nodes. We propose two methods for constructing a virtual backbone connecting the nodes
Hoverlay : a peer-to-peer system for on demand sharing of capacity across network applications
EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Hoverlay : a peer-to-peer system for on demand sharing of capacity across network applications
EThOS - Electronic Theses Online ServiceGBUnited Kingdo
DeMMon Decentralized Management and Monitoring Framework
The centralized model proposed by the Cloud computing paradigm mismatches the decentralized
nature of mobile and IoT applications, given the fact that most of the data
production and consumption is performed by end-user devices outside of the Data Center
(DC). As the number of these devices grows, and given the need to transport data to and
from DCs for computation, application providers incur additional infrastructure costs,
and end-users incur delays when performing operations.
These reasons have led us into a post-cloud era, where a new computing paradigm
arose: Edge Computing. Edge Computing takes into account the broad spectrum of
devices residing outside of the DC, closer to the clients, as potential targets for computations,
potentially reducing infrastructure costs, improving the quality of service (QoS)
for end-users and allowing new interaction paradigms between users and applications.
Managing and monitoring the execution of these devices raises new challenges previously
unaddressed by Cloud computing, given the scale of these systems and the devicesâ
(potentially) unreliable data connections and heterogenous computational power. The
study of the state-of-the-art has revealed that existing resource monitoring and management
solutions require manual configuration and have centralized components, which
we believe do not scale for larger-scale systems.
In this work, we address these limitations by presenting a novel Decentralized Management
and Monitoring (âDeMMonâ) system, targeted for edge settings. DeMMon provides
primitives to ease the development of tools that manage computational resources
that support edge-enabled applications, decomposed in components, through decentralized
actions, taking advantage of partial knowledge of the system. Our solution was
evaluated to amount to its benefits regarding information dissemination and monitoring
capabilities across a set of realistic emulated scenarios of up to 750 nodes with variable
failure rates. The results show the validity of our approach and that it can outperform
state-of-the-art solutions regarding scalability and reliabilityO modelo centralizado de computação utilizado no paradigma da Computação na Nuvem
apresenta limitaçÔes no contexto de aplicaçÔes no domĂnio da Internet das Coisas
e aplicaçÔes móveis. Neste tipo de aplicaçÔes, os dados são produzidos e consumidos
maioritariamente por dispositivos que se encontram na periferia da rede. Desta forma,
transportar estes dados de e para os centros de dados impÔe uma carga excessiva nas
infraestruturas de rede que ligam os dispositivos aos centros de dados, aumentando a
latĂȘncia de respostas e diminuindo a qualidade de serviço para os utilizadores.
Para combater estas limitaçÔes, surgiu o paradigma da Computação na Periferia, este
paradigma propÔe a execução de computaçÔes, e potencialmente armazenamento de
dados, em dispositivos fora dos centros de dados, mais perto dos clientes, reduzindo
custos e criando um novo leque de possibilidades para efetuar computaçÔes distribuĂdas
mais prĂłximas dos dispositivos que produzem e consomem os dados.
Contudo, gerir e supervisionar a execução desses dispositivos levanta obståculos não
equacionados pela Computação na Nuvem, como a escala destes sistemas, ou a variabilidade
na conectividade e na capacidade de computação dos dispositivos que os compÔem.
O estudo da literatura revela que ferramentas populares para gerir e supervisionar aplicaçÔes
e dispositivos possuem limitaçÔes para a sua escalabilidade, como por exemplo,
pontos de falha centralizados, ou requerem a configuração manual de cada dispositivo.
Nesta dissertação, propÔem-se uma nova solução de monitorização e disseminação
de informação descentralizada. Esta solução oferece operaçÔes que permitem recolher
informação sobre o estado do sistema, de modo a ser utilizada por soluçÔes (também
descentralizadas) que gerem aplicaçÔes especializadas para executar na periferia da rede.
A nossa solução foi avaliada em redes emuladas de vårias dimensÔes com um måximo
de 750 nós, no contexto de disseminação e de monitorização de informação. Os nossos
resultados mostram que o nosso sistema consegue ser mais robusto ao mesmo tempo que
Ă© mais escalĂĄvel quando comparado com o estado da arte
Advanced methods for query routing in peer-to-peer information retrieval
One of the most challenging problems in peer-to-peer networks is query routing: effectively and efficiently identifying peers that can return high-quality local results for a given query. Existing methods from the areas of distributed information retrieval and metasearch engines do not adequately address the peculiarities of a peer-to-peer network. The main contributions of this thesis are as follows: 1. Methods for query routing that take into account the mutual overlap of different peers\u27; collections, 2. Methods for query routing that take into account the correlations between multiple terms, 3. Comparative evaluation of different query routing methods. Our experiments confirm the superiority of our novel query routing methods over the prior state-of-the-art, in particular in the context of peer-to-peer Web search.Eines der drĂ€ngendsten Probleme in Peer-to-Peer-Netzwerken ist Query-Routing: das effektive und effiziente Identifizieren solcher Peers, die qualitativ hochwertige lokale Ergebnisse zu einer gegebenen Anfrage liefern können. Die bisher bekannten Verfahren aus dem Bereich der verteilten Informationssuche sowie der Metasuchmaschinen werden den Besonderheiten von Peer-to-Peer-Netzwerken nicht gerecht. Die HautbeitrĂ€ge dieser Arbeit teilen sich in folgende Schwerpunkte: 1. Query-Routing unter BerĂŒcksichtigung der gegenseitigen ĂŒberlappung der Kollektionen verschiedener Peers, 2. Query-Routing unter BerĂŒcksichtigung der Korrelationen zwischen verschiedenen Termen, 3. Vergleichende Evaluierung verschiedener Methoden zum Query-Routing. Unsere Experimente bestĂ€tigen die Ăberlegenheit der in dieser Arbeit entwickelten Verfahren gegenĂŒber den bisher bekannten Verfahren, insbesondere im Kontext von Peer-to-Peer-Websuche
Efficient Passive Clustering and Gateways selection MANETs
Passive clustering does not employ control packets to collect topological information in ad hoc networks. In our proposal, we avoid making frequent changes in cluster architecture due to repeated election and re-election of cluster heads and gateways. Our primary objective has been to make Passive Clustering more practical by employing optimal number of gateways and reduce the number of rebroadcast packets
A COGNITIVE ARCHITECTURE FOR AMBIENT INTELLIGENCE
LâAmbient Intelligence (AmI) Ăš caratterizzata dallâuso di sistemi pervasivi per
monitorare lâambiente e modificarlo secondo le esigenze degli utenti e rispettando
vincoli definiti globalmente. Questi sistemi non possono prescindere da requisiti
come la scalabilitĂ e la trasparenza per lâutente. Una tecnologia che consente di
raggiungere questi obiettivi Ăš rappresentata dalle reti di sensori wireless (WSN),
caratterizzate da bassi costi e bassa intrusivitĂ . Tuttavia, sebbene in grado di
effettuare elaborazioni a bordo dei singoli nodi, le WSN non hanno da sole le capacitĂ
di elaborazione necessarie a supportare un sistema intelligente; dâaltra parte
senza questa attivitĂ di pre-elaborazione la mole di dati sensoriali puĂČ facilmente
sopraffare un sistema centralizzato con unâeccessiva quantitĂ di dettagli superflui.
Questo lavoro presenta unâarchitettura cognitiva in grado di percepire e controllare
lâambiente di cui fa parte, basata su un nuovo approccio per lâestrazione
di conoscenza a partire dai dati grezzi, attraverso livelli crescenti di astrazione.
Le WSN sono utilizzate come strumento sensoriale pervasivo, le cui capacitĂ computazionali
vengono utilizzate per pre-elaborare i dati rilevati, in modo da consentire
ad un sistema centralizzato intelligente di effettuare ragionamenti di alto
livello.
Lâarchitettura proposta Ăš stata utilizzata per sviluppare un testbed dotato degli
strumenti hardware e software necessari allo sviluppo e alla gestione di applicazioni
di AmI basate su WSN, il cui obiettivo principale sia il risparmio energetico. Per
fare in modo che le applicazioni di AmI siano in grado di comunicare con il mondo
esterno in maniera affidabile, per richiedere servizi ad agenti esterni, lâarchitettura
Ăš stata arricchita con un protocollo di gestione distribuita della reputazione.
Ă stata inoltre sviluppata unâapplicazione di esempio che sfrutta le caratteristiche
del testbed, con lâobiettivo di controllare la temperatura in un ambiente
lavorativo. Questâapplicazione rileva la presenza dellâutente attraverso un modulo
per la fusione di dati multi-sensoriali basato su reti bayesiane, e sfrutta questa
informazione in un controllore fuzzy multi-obiettivo che controlla gli attuatori sulla
base delle preferenze dellâutente e del risparmio energetico.Ambient Intelligence (AmI) systems are characterized by the use of pervasive
equipments for monitoring and modifying the environment according to usersâ
needs, and to globally defined constraints. Furthermore, such systems cannot ignore
requirements about ubiquity, scalability, and transparency to the user. An
enabling technology capable of accomplishing these goals is represented by Wireless
Sensor Networks (WSNs), characterized by low-costs and unintrusiveness. However,
although provided of in-network processing capabilities, WSNs do not exhibit
processing features able to support comprehensive intelligent systems; on the other
hand, without this pre-processing activities the wealth of sensory data may easily
overwhelm a centralized AmI system, clogging it with superfluous details.
This work proposes a cognitive architecture able to perceive, decide upon, and
control the environment of which the system is part, based on a new approach to
knowledge extraction from raw data, that addresses this issue at different abstraction
levels. WSNs are used as the pervasive sensory tool, and their computational
capabilities are exploited to remotely perform preliminary data processing. A central
intelligent unit subsequently extracts higher-level concepts in order to carry on
symbolic reasoning. The aim of the reasoning is to plan a sequence of actions that
will lead the environment to a state as close as possible to the usersâ desires, taking
into account both implicit and explicit feedbacks from the users, while considering
global system-driven goals, such as energy saving. The proposed conceptual architecture
was exploited to develop a testbed providing the hardware and software
tools for the development and management of AmI applications based on WSNs,
whose main goal is energy saving for global sustainability. In order to make the
AmI system able to communicate with the external world in a reliable way, when
some services are required to external agents, the architecture was enriched with
a distributed reputation management protocol.
A sample application exploiting the testbed features was implemented for addressing
temperature control in a work environment. Knowledge about the userâs
presence is obtained through a multi-sensor data fusion module based on Bayesian
networks, and this information is exploited by a multi-objective fuzzy controller
that operates on actuators taking into account usersâ preference and energy consumption
constraints