An adaptive approach to opportunistic data forwarding in underwater acoustic sensor networks

Reliable data transfer for underwater acoustic sensor networks (UASNs) is a major research challenge in applications such as pollution monitoring, oceanic data collection, and surveillance due to the long propagation delay and high error rate of the acoustic channel. To address this issue, an opportunistic data forwarding protocol was proposed which achieves high packet delivery success ratio with less routing overhead and energy consumption by selecting the next hop forwarder among a set of candidates based on its link reliability and data transfer reach ability. However, the protocol relies on fixed data hold time approach, i.e., Each node holds data packets for a fixed amount of time before a forwarder discovery process is initiated. Depending on the value of the fixed hold time and deployment contextual scenario, this may incur large end-to-end delay. Moreover, lack of consideration of network condition in hold time limits its performance. In this paper, we propose an adaptive technique to improve its performance. The adaptive approach calculates data hold time at each node dynamically considering a number of 'node and network' metrics including current buffer occupancy, delay experienced by stored data packets, arrival and service rate, neighbors' data transmissions and reach ability. Simulation results show that compared with fixed hold time approach, our adaptive technique reduces end-to-end delay significantly, achieves considerably higher data delivery and less energy consumption per successful packet delivery

Content Management in Mobile Wireless Networks

Approximately one billion users have access to mobile broadband, through which they intend to obtain the same data they can reach using a wired connection. Because of the cost of transmitting data over a mobile-broadband connection and given that 3G networks are quickly reaching their data-transfer capacity, some researchers envision the inter-connection of mobile devices using Wi-Fi, forming a challenged network. Such networks suffer from high latency, low data rates, and frequent disconnections; because end to end paths between pairs of nodes may not always exist, a mobile device must store content before delivering it to the intended receivers. We designed the content-optimal delivery algorithm (CODA) for distributing named data over a delay-tolerant network (DTN), which is a network of challenged networks. Current content-dissemination techniques for DTNs consist mainly of the following items: a content store, for caching and indexing retrieved content, and a query and response mechanism to search the network for matching content. Some algorithms attempt to optimize an objective function, such as the total delivery-delay. While disseminating content, CODA maximizes the network throughput by computing the utility of each item published: a device with a full buffer drops content in order of increasing utility and transmits content in order de- creasing utility. We implemented CODA over the CCNx protocol, which provides the basic tools for querying, caching, and transmitting content

Opportunistic Networks: Present Scenario- A Mirror Review

Opportunistic Network is form of Delay Tolerant Network (DTN) and regarded as extension to Mobile Ad Hoc Network. OPPNETS are designed to operate especially in those environments which are surrounded by various issues like- High Error Rate, Intermittent Connectivity, High Delay and no defined route between source to destination node. OPPNETS works on the principle of “Store-and-Forward” mechanism as intermediate nodes perform the task of routing from node to node. The intermediate nodes store the messages in their memory until the suitable node is not located in communication range to transfer the message to the destination. OPPNETs suffer from various issues like High Delay, Energy Efficiency of Nodes, Security, High Error Rate and High Latency. The aim of this research paper is to overview various routing protocols available till date for OPPNETs and classify the protocols in terms of their performance. The paper also gives quick review of various Mobility Models and Simulation tools available for OPPNETs simulation

INTERMITTENTLY CONNECTED DELAY-TOLERANT WIRELESS SENSOR NETWORKS

Intermittently Connected Delay-Tolerant Wireless Sensor Networks (ICDT-WSNs), a branch of Wireless Sensor Networks (WSNs), have features of WSNs and the intermittent connectivity of Opportunistic Networks. The applications of ICDT-WSNs are increasing in recent years; however, the communication protocols suitable for this category of networks often fall short. Most of the existing communication protocols are designed for either WSNs or Opportunistic Networks with sufficient resources and tend to be inadequate for direct use in ICDT-WSNs. In this dissertation, we study ICDT-WSNs from the perspective of the characteristics, chal- lenges and possible solutions. A high-level overview of ICDT-WSNs is given, followed by a study of existing work and our solutions to address the problems of routing, flow control, error control, and storage management. The proposed solutions utilize the utility level of nodes and the connectedness of a network. In addition to the protocols for information transmissions to specific destinations, we also propose efficient mechanisms for information dissemination to arbitrary destinations. The study shows that our proposed solutions can achieve better performance than other state of the art communication protocols without sacrificing energy efficiency

Delay Tolerant Networks for Efficient Information Harvesting and Distribution in Intelligent Transportation Systems

[EN] Intelligent Transportation Systems (ITS) can make transportation safer, more efficient, and more sustainable by applying various information and communication technologies. One of these technologies are \acfp{VN}. \acp{VN} combine different communication solutions such as cellular networks, \acfp{VANET}, or IEEE 802.11 technologies to provide connectivity among vehicles, and between vehicles and road infrastructure. This thesis focuses on VNs, and considers that the high speed of the nodes and the presence of obstacles like buildings, produces a highly variable network topology, as well as more frequent partitions in the network. Therefore, classical \ac{MANET} protocols do not adapt well to VANETs. Under these conditions, \ac{DTN} have been proposed as an alternative able to cope with these adverse characteristics. In DTN, when a message cannot be routed to its destination, it is not immediately dropped but it is instead stored and carried until a new route becomes available. The combination of VN and DTN is called \acp{VDTN}. In this thesis, we propose a new VDTN protocol designed to collect information from vehicular sensors. Our proposal, called \ac{MSDP}, combines information about the localization obtained from a GNSS system with the actual street/road layout obtained from a Navigation System (NS) to define a new routing metric. Both analytical and simulation results prove that MSDP outperforms previous proposals. Concerning the deployment of VNs and VANET technologies, technology already left behind the innovation and the standardization phases, and it is about time it reach the first early adopters in the market. However, most car manufacturers have decided to implement VN devices in the form of On Board Units (OBUs), which are expensive, heavily manufacturer dependent, and difficult to upgrade. These facts are delaying the deployment of VN. To boost this process, we have developed the GRCBox architecture. This architecture is based on low-cost devices and enables the establishment of V2X, \emph{i.e.} V2I and V2V, communications while integrating users by easing the use of general purpose devices like smartphones, tablets or laptops. To demonstrate the viability of the GRCBox architecture, we combined it with a DTN platform called Scampi to obtain actual results over a real VDTN scenario. We also present several GRCBox-aware applications that illustrate how developers can create applications that bring the potential of VN to user devices.[ES] Los sistemas de transporte inteligente (ITS) son el soporte para el establecimiento de un transporte más seguro, más eficiente y más sostenible mediante el uso de tecnologías de la información y las comunicaciones. Una de estas tecnologías son las redes vehiculares (VNs). Las VNs combinan diferentes tecnologías de comunicación como las redes celulares, las redes ad-hoc vehiculares (VANETs) o las redes 802.11p para proporcionar conectividad entre vehículos, y entre vehículos y la infraestructura de carreteras. Esta tesis se centra en las VNs, en las cuales la alta velocidad de los nodos y la presencia de obstáculos como edificios producen una topología de red altamente variable, así como frecuentes particiones en la red. Debido a estas características, los protocolos para redes móviles ad-hoc (MANETs) no se adaptan bien a las VANETs. En estas condiciones, las redes tolerantes a retardos (DTNs) se han propuesto como una alternativa capaz de hacer frente a estos problemas. En DTN, cuando un mensaje no puede ser encaminado hacia su destino, no es inmediatamente descartado sino es almacenado hasta que una nueva ruta esta disponible. Cuando las VNs y las DTNs se combinan surgen las redes vehiculares tolerantes a retardos (VDTN). En esta tesis proponemos un nuevo protocolo para VDTNs diseñado para recolectar la información generada por sensores vehiculares. Nuestra propuesta, llamada MSDP, combina la información obtenida del servicio de información geográfica (GIS) con el mapa real de las calles obtenido del sistema de navegación (NS) para definir una nueva métrica de encaminamiento. Resultados analíticos y mediante simulaciones prueban que MSDP mejora el rendimiento de propuestas anteriores. En relación con el despliegue de las VNs y las tecnologías VANET, la tecnología ha dejado atrás las fases de innovación y estandarización, ahora es el momento de alcanzar a los primeros usuarios del mercado. Sin embargo, la mayoría de fabricantes han decidido implementar los dispositivos para VN como unidades de a bordo (OBU), las cuales son caras y difíciles de actualizar. Además, las OBUs son muy dependientes del fabricante original. Todo esto esta retrasando el despliegue de las VNs. Para acelerar la adopción de las VNs, hemos desarrollado la arquitectura GRCBox. La arquitectura GRCBox esta basada en un dispositivo de bajo coste que permite a los usuarios usar comunicaciones V2X (V2V y V2I) mientras utilizan dispositivos de propósito general como teléfonos inteligentes, tabletas o portátiles. Las pruebas incluidas en esta tesis demuestran la viabilidad de la arquitectura GRCBox. Mediante la combinación de nuestra GRCBox y una plataforma de DTN llamada Scampi hemos diseñado y probado un escenario VDTN real. También presentamos como los desarrolladores pueden crear nuevas aplicaciones GRCBox para llevar el potencial de las VN a los dispositivos de usuario.[CA] Els sistemes de transport intel·ligent (ITS) poden crear un transport més segur, més eficient i més sostenible mitjançant l'ús de tecnologies de la informació i les comunicacions aplicades al transport. Una d'aquestes tecnologies són les xarxes vehiculars (VN). Les VN combinen diferents tecnologies de comunicació, com ara les xarxes cel·lulars, les xarxes ad-hoc vehiculars (VANET) o les xarxes 802.11p, per a proporcionar comunicació entre vehicles, i entre vehicles i la infraestructura de carreteres. Aquesta tesi se centra en les VANET, en les quals l'alta velocitat dels nodes i la presència d'obstacles, com els edificis, produeixen una topologia de xarxa altament variable, i també freqüents particions en la xarxa. Per aquest motiu, els protocols per a xarxes mòbils ad-hoc (MANET) no s'adapten bé. En aquestes condicions, les xarxes tolerants a retards (DTN) s'han proposat com una alternativa capaç de fer front a aquests problemes. En DTN, quan un missatge no pot ser encaminat cap a la seua destinació, no és immediatament descartat sinó que és emmagatzemat fins que apareix una ruta nova. Quan les VN i les DTN es combinen sorgeixen les xarxes vehicular tolerants a retards (VDTN). En aquesta tesi proposem un nou protocol per a VDTN dissenyat per a recol·lectar la informació generada per sensors vehiculars. La nostra proposta, anomenada MSDP, combina la informació obtinguda del servei d'informació geogràfica (GIS) amb el mapa real dels carrers obtingut del sistema de navegació (NS) per a definir una nova mètrica d'encaminament. Resultats analítics i mitjançant simulacions proven que MSDP millora el rendiment de propostes prèvies. En relació amb el desplegament de les VN i les tecnologies VANET, la tecnologia ha deixat arrere les fases d'innovació i estandardització, ara és temps d'aconseguir als primers usuaris del mercat. No obstant això, la majoria de fabricants han decidit implementar els dispositius per a VN com a unitats de bord (OBU), les quals són cares i difícils d'actualitzar. A més, les OBU són molt dependents del fabricant original. Tot això està retardant el desplegament de les VN. Per a accelerar l'adopció de les VN, hem desenvolupat l'arquitectura GRCBox. L'arquitectura GRCBox està basada en un dispositiu de baix cost que permet als usuaris usar comunicacions V2V mentre usen dispositius de propòsit general, com ara telèfons intel·ligents, tauletes o portàtils. Les proves incloses en aquesta tesi demostren la viabilitat de l'arquitectura GRCBox. Mitjançant la combinació de la nostra GRCBox i la plataforma de DTN Scampi, hem dissenyat i provat un escenari VDTN pràctic. També presentem com els desenvolupadors poden crear noves aplicacions GRCBox per a portar el potencial de les VN als dispositius d'usuari.Martínez Tornell, S. (2016). Delay Tolerant Networks for Efficient Information Harvesting and Distribution in Intelligent Transportation Systems [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/68486TESI

H3N - Analysewerkzeuge für hybride Wegewahl in heterogenen, unterbrechungstoleranten Ad-Hoc-Netzen für Rettungskräfte

Rettungskräfte müssen unter widrigen Bedingungen zuverlässig kommunizieren können, um in Rettungseinsätzen effizient arbeiten zu können und somit Leben zu retten. Idealerweise ist dazu ein selbstorganisiertes Ad-Hoc-Netz notwendig, weil die Kommunikationsinfrastruktur ggf. beschädigt oder überlastet sein kann. Um die geforderte Robustheit der Kommunikation auch in Szenarien mit größeren zu überbrückenden Entfernungen zu gewährleisten, werden zusätzlich Mechanismen benötigt, die eine Unterbrechungstoleranz ermöglichen. Verzögerungstolerante Netze (engl. Delay Tolerant Networks, kurz: DTN) stellen solche Mechanismen bereit, erfordern aber zusätzliche Verzögerungen, die für Rettungskommunikation nachteilig sind. Deshalb werden intelligente hybride Wegewahlverfahren benötigt, um die Verzögerung durch DTN-Mechanismen zu begrenzen. Außerdem sollten entsprechende Verfahren heterogene Netze unterstützen. Das ermöglicht zusätzlich eine effizientere Weiterleitung durch die Nutzung von Geräten mit unterschiedlichen Kommunikationstechnologien und damit auch Reichweiten. Um solche Systeme und die dafür benötigten Kommunikationsprotokolle zu entwickeln, werden verschiedene Analysewerkzeuge genutzt. Dazu gehören analytische Modelle, Simulationen und Experimente auf der Zielsystemhardware. Für jede Kategorie gibt es verschiedene Werkzeuge und Frameworks, die sich auf unterschiedliche Aspekte fokussieren. Dadurch unterstützen diese herkömmlichen Analysemethoden jedoch meistens nur einen der oben genannten Punkte, während die Untersuchung von hybriden und/oder heterogenen Ansätzen und Szenarien nicht ohne weiteres möglich ist. Im Falle von Rettungskräften kommt hinzu, dass die charakteristischen Merkmale hinsichtlich der Bewegung der Knoten und des erzeugten Datenverkehrs während eines Einsatzes ebenfalls nicht modelliert werden können. In dieser Arbeit werden deshalb verschiedene Erweiterungen zu existierenden Analysewerkzeugen sowie neue Werkzeuge zur Analyse und Modelle zur Nachbildung realistischer Rettungsmissionen untersucht und entwickelt. Ziel ist es, die Vorteile existierender Werkzeuge miteinander zu kombinieren, um ganzheitliche, realitätsnahe Untersuchungen von hybriden Protokollen für heterogene Netze zu ermöglichen. Die Kombination erfolgt in Form von gezielten Erweiterungen und der Entwicklung ergänzender komplementärer Werkzeuge unter Verwendung existierender Schnittstellen. Erste Ergebnisse unter Verwendung der entwickelten Werkzeuge zeigen Verbesserungspotentiale bei der Verwendung traditioneller Protokolle und erlauben die Bewertung zusätzlicher Maßnahmen, um die Kommunikation zu verbessern. Szenarien zur Kommunikation von Rettungskräften werden dabei als ein Beispiel verwendet, die Tools sind jedoch nicht auf die Analyse dieses Anwendungsfalls beschränkt. Über die reine Analyse verschiedener existierender Ansätze hinaus bildet die entwickelte Evaluationsumgebung eine Grundlage für die Entwicklung und Verifikation von neuartigen hybriden Protokollen für die entsprechenden Systeme.Communication between participating first responders is essential for efficient coordination of rescue missions and thus allowing to save human lives. Ideally, ad hoc-style communication networks are applied to this as the first responders cannot rely on infrastructure-based communication for two reasons. First, the infrastructure could be damaged by the disastrous event or not be available for economic reasons. Second, even if public infrastructure is available and functional, it might be overloaded by users. To guarantee the robustness and reliability requirements of first responders, the Mobile Ad Hoc Networks (MANETs) have to be combined with an approach to mitigate intermittent connectivity due to otherwise limited connectivity. Delay Tolerant Networks (DTNs) provide such a functionality but introduce additional delay which is problematic. Therefore, intelligent hybrid routing approaches are required to limit the delay introduced by DTN mechanisms. Besides that, the approach should be applicable to heterogeneous networks in terms of communication technologies and device capabilities. This is required for cross multi-agency and volunteer communication but also enables the opportunistic exploitation of any given communication option. To evaluate such systems and develop the corresponding communication protocols, various tools for the analysis are available. This includes analytical models, simulations and real-world experiments on target hardware. In each category a wide set of tools is available already. However, each tool is focused on specific aspects usually and thus does not provide methods to analyze hybrid approaches out of the box. Even if the tools are modular and allow an extension, there are often other tools that are better suited for partial aspects of hybrid systems. In addition to this, few tools exist to model the characteristics of first responder networks. Especially the generalized movement during missions and the generated data traffic are difficult to model and integrate into analyses. The focus of this project is therefore to develop selected extensions to existing analysis and simulation tools as well as additional tools and models to realistically capture the characteristics of first responder networks. The goal is to combine the advantages of existing specialized simulation tools to enable thorough evaluations of hybrid protocols for heterogeneous networks based on realistic assumptions. To achieve this, the tools are extended by specifically designing tools that enable the interaction between tools and new tools that complement the existing analysis capabilities. First results obtained via the resulting toolbox clearly indicate further research directions as well as a potential for protocol enhancements. Besides that, the toolbox was used to evaluate various methods to enhance the connectivity between nodes in first responder networks. First responder scenarios are used as an example here. The toolbox itself is however not limited to this use case. In addition to the analysis of existing approaches for hybrid and heterogeneous networks, the developed toolbox provides a base framework for the development and verification of newly developed protocols for such use cases

Subjective logic based trust model for geographic routing in mobile ad hoc networks

Uobičajeni modeli pouzdanosti ne uspijevaju izraziti pojam nesigurnosti tijekom uspostavljanja pouzdanih odnosa između pokretnih čvorova. Nadalje, nedostaje im uvažavanje značajki okoline u ocjeni pouzdanosti. U radu se predlaže model pouzdanosti zasnovan na subjektivnoj logici u POR (SLT-POR) koji u modelu integrira pouzdanost zasnovanu na kontekstu i onu zasnovanu na ponašanju. Pouzdanost zasnovana na ponašanju uključuje fuziju evidencije zasnovane na subjektivnoj logici u evaluaciji indirektne pouzdanosti kako bi se eksplicitno predstavilo i upravljalo neznanjem kao nesigurnošću. Odnos pouzdanosti između čvorova ne može uvijek odražavati stvarni odnos te stoga provedena odluka iz izvedenog odnosa pouzdanosti nije uvijek točna. Teorija subjektivne logike uključuje dinamičkog operatora osnovne brzine koji procjenjuje očekivanje mišljenja i bavi se nesigurnošću u skupljanju podataka. U mjerenju pouzdanost zasnovane na obilježjima konteksta, SLT-POR procjenjuje vrijednost pouzdanosti zasnovane na kontekstu uporabom kontekstualnih obilježja svakog čvora u nizu pozitivnog pouzdanog djelovanja. SLT-POR u procjeni pouzdanosti pazi da snaga baterije uključuje vijek trajanja čvora, pridaje važnost pouzdanosti zasnovanoj na kontekstu kao i onoj zasnovanoj na ponašanju kako bi učinkovito izračunao ukupnu pouzdanost čvora. Rezultati simulacije pokazuju da je omjer isporuke paketa predloženog SLT-POR visok, čak i ako je 50 % svih čvorova maliciozno te da je bolji od sustava CAST - Context-Aware Security and Trust.In the past decades, several trust models have been proposed to enhance the security of Mobile Ad hoc Networks (MANETs). The conventional trust models fail to express the notion of uncertainty during the establishment of trust relationships between mobile nodes. Furthermore, they lack in considering the context attributes in trust evaluation. This paper proposes a subjective logic based trust model in POR (SLT-POR) that integrates both the behavioural and context based trust in trust model. The behavioural based trust incorporates subjective logic based evidence fusion in indirect trust evaluation to explicitly represent and manage ignorance as uncertainty. The trust relationship between nodes cannot always reflect the actual relationship and consequently the executed decision from the extracted trust relationship is not always accurate. The subjective logic theory includes a dynamic base rate operator that evaluates an expectation of an opinion and handles the uncertainty in evidence collection. In context, attributes based trust measurement, the SLT-POR estimates a context based trust value using the contextual attributes of each node in the trusted positive progress set. The SLT-POR considers the battery power to include node’s lifetime in the trustworthiness estimation. It assigns a weight for both behaviour and context based trust to efficiently calculate total trustworthiness of a node. The simulation results demonstrate that the packet delivery ratio of the proposed SLT-POR is high even if 50 % of total nodes are malicious and outperforms Context-Aware Security and Trust (CAST) framework