53 research outputs found
Spray Router with Node Location Dependent Remaining-TTL Message Scheduling in DTNs
Delay and disruption tolerant networks (DTNs) adopt the store-carry-and-forward paradigm. Each node stores messages in a buffer storage and waits for either an appropriate forwarding opportunity or the message\u27s expiration time, i.e., its time-to-live (TTL). There are two key issues that influence the performance of DTN routing: the forwarding policy that determines whether a message should be forwarded to an encountered node, and the buffer management policy that determines which message should be sent from the queue (i.e., message scheduling) and which message should be dropped when the buffer storage is full. This paper proposes a DTN routing protocol, called spray-and hop-distance-based with remaining-TTL consideration (SNHD-TTL) which integrates three features: (1) binary spray; (2) hop-distance-based forwarding; and (3) node location dependent remaining-TTL message scheduling. The aim is to better deliver messages which are highly congested especially in the “island scenario.” We evaluate it by simulation-based comparison with other popular protocols, namely Epidemic as a baseline and PRoPHETv2 that performs well according to our previous study. Our simulation results show that SNHD-TTL is able to outperform other routing protocols, significantly reduce overhead, and at the same time, increase the total size of delivered messages.Special Issue of Applications and the Internet in Conjunction with Main Topics of COMPSAC 201
Medium access control, error control and routing in underwater acoustic networks: a discussion on protocol design and implementation
The journey of underwater communication which began from Leonardo’s era took four and a half centuries to find practical applications for military purposes during World War II. However, over the last three decades, underwater acoustic communications witnessed a massive development due to the advancements in the design of underwater communicating
peripherals and their supporting protocols. Successively, doors are opened for a wide range of applications to employ in the underwater environment, such as oceanography, pollution
monitoring, offshore exploration, disaster prevention, navigation assistance, monitoring, coastal patrol and surveillance. Different applications may have different characteristics and hence, may require different network architectures. For instance, routing protocols designed for unpartitioned multi-hop networks are not suitable for Delay-Tolerant Networks. Furthermore, single-hop networks do not need routing protocols at all. Therefore, before
developing a protocol one must study the network architecture properly and design it accordingly.
There are several other factors which should also be considered with the network architecture while designing an efficient protocol for underwater networks, such as long propagation delay, limited bandwidth, limited battery power, high bit error rate of the channel and several other adverse properties of the channel, such as, multi-path, fading and refractive behaviors. Moreover, the environment also has an impact on the performance of the protocols designed for underwater networks. Even temperature changes in a single day have an impact on the performance of the protocols. A good protocol designed for any network should consider some or all of these characteristics to achieve better performance.
In this thesis, we first discuss the impact of the environment on the performance of MAC and routing protocols. From our investigation, we discover that even temperature changes within a day may affect the sound speed profile and hence, the channel changes and the protocol performance vary. After that we discuss several protocols which are specifically designed for underwater acoustic networks to serve different purposes and for different network architectures. Underwater Selective Repeat (USR) is an error control protocol designed to assure reliable data transmission in the MAC layer. One may suspect that employing an error control technique over a channel which already suffers from long propagation delays is a burden. However, USR utilizes long propagation by transmitting multiple packets in a single RTT using an interlacing technique. After USR, a routing protocol for surveillance networks is discussed where some sensors are laid down at the bottom of the sea and some sinks are placed outside the area. If a sensor detects an asset within its detection range, it announces the presence of intruders by transmitting packets to the sinks. It may happen
that the discovered asset is an enemy ship or an enemy submarine which creates noise to jam the network. Therefore, in surveillance networks, it is necessary that the protocols have
jamming resistance capabilities. Moreover, since the network supports multiple sinks with similar anycast address, we propose a Jamming Resistance multi-path Multi-Sink Routing
Protocol (MSRP) using a source routing technique. However, the problem of source routing is that it suffers from large overhead (every packet includes the whole path information) with
respect to other routing techniques, and also suffers from the unidirectional link problem. Therefore, another routing protocol based on a distance vector technique, called Multi-path
Routing with Limited Cross-Path Interference (L-CROP) protocol is proposed, which employs a neighbor-aware multi-path discovery algorithm to support low interference multiple paths
between each source-destination pair. Following that, another routing protocol is discussed for next generation coastal patrol and surveillance network, called Underwater Delay-Tolerant
Network (UDTN) routing where some AUVs carry out the patrolling work of a given area and report to a shore based control-center. Since the area to be patrolled is large, AUVs
experience intermittent connectivity. In our proposed protocol, two nodes that understand to be in contact with each other calculate and divide their contact duration equally so that
every node gets a fair share of the contact duration to exchange data. Moreover, a probabilistic spray technique is employed to restrict the number of packet transmissions and for error correction a modified version of USR is employed.
In the appendix, we discuss a framework which was designed by our research group to realize underwater communication through simulation which is used in most of the simulations in this thesis, called DESERT Underwater (short for DEsign, Simulate, Emulate and Realize Test-beds for Underwater network protocols). It is an underwater extension of the
NS-Miracle simulator to support the design and implementation of underwater network protocols. Its creation assists the researchers in to utilizing the same codes designed for the
simulator to employ in actual hardware devices and test in the real underwater scenario
Hybrid Satellite-Terrestrial Communication Networks for the Maritime Internet of Things: Key Technologies, Opportunities, and Challenges
With the rapid development of marine activities, there has been an increasing
number of maritime mobile terminals, as well as a growing demand for high-speed
and ultra-reliable maritime communications to keep them connected.
Traditionally, the maritime Internet of Things (IoT) is enabled by maritime
satellites. However, satellites are seriously restricted by their high latency
and relatively low data rate. As an alternative, shore & island-based base
stations (BSs) can be built to extend the coverage of terrestrial networks
using fourth-generation (4G), fifth-generation (5G), and beyond 5G services.
Unmanned aerial vehicles can also be exploited to serve as aerial maritime BSs.
Despite of all these approaches, there are still open issues for an efficient
maritime communication network (MCN). For example, due to the complicated
electromagnetic propagation environment, the limited geometrically available BS
sites, and rigorous service demands from mission-critical applications,
conventional communication and networking theories and methods should be
tailored for maritime scenarios. Towards this end, we provide a survey on the
demand for maritime communications, the state-of-the-art MCNs, and key
technologies for enhancing transmission efficiency, extending network coverage,
and provisioning maritime-specific services. Future challenges in developing an
environment-aware, service-driven, and integrated satellite-air-ground MCN to
be smart enough to utilize external auxiliary information, e.g., sea state and
atmosphere conditions, are also discussed
Mobility entropy and message routing in community-structured delay tolerant networks
Many message routing schemes have been proposed in the context of delay tolerant networks (DTN) and intermittently connected mobile networks (ICMN). Those routing schemes are tested on specific environments that involve particular mobility complexity whether they are random-based or soci-ologically organized. We, in this paper, propose community structured environment (CSE) and mobility entropy to dis-cuss the effect of node mobility complexity on message rout-ing performance. We also propose potential-based entropy adaptive routing (PEAR) that adaptively carries messages over the change of mobility entropy. According to our simu-lation, PEAR has achieved high delivery rate on wide range of mobility entropy, while link-state routing has worked well only at small entropy scenarios and controlled replication-based routing only at large entropy environments
Hybrid Routing in Delay Tolerant Networks
This work addresses the integration of today\u27s infrastructure-based networks with infrastructure-less networks. The resulting Hybrid Routing System allows for communication over both network types and can help to overcome cost, communication, and overload problems. Mobility aspect resulting from infrastructure-less networks are analyzed and analytical models developed. For development and deployment of the Hybrid Routing System an overlay-based framework is presented
Hybrid routing in delay tolerant networks
This work addresses the integration of today\\u27s infrastructure-based networks with infrastructure-less networks. The resulting Hybrid Routing System allows for communication over both network types and can help to overcome cost, communication, and overload problems. Mobility aspect resulting from infrastructure-less networks are analyzed and analytical models developed. For development and deployment of the Hybrid Routing System an overlay-based framework is presented
The Impact of Rogue Nodes on the Dependability of Opportunistic Networks
Opportunistic Networks (OppNets) are an extension to the classical Mobile Ad hoc Networks
(MANETs) where the network is not dependent on any infrastructure (e.g. Access Points or
centralized administrative nodes). OppNets can be more flexible than MANETs because an end
to end path does not exist and much longer delays can be expected. Whereas a Rogue Access
Point is typically immobile in the legacy infrastructure based networks and can have considerable
impact on the overall connectivity, the research question in this project evaluates how the pattern
and mobility of a rogue nodes impact the dependability and overall "Average Latency" in an
Opportunistic Network Environment. We have simulated a subset of the mathematical modeling
performed in a previous publication in this regard.
Ad hoc networks are very challenging to model due to their mobility and intricate routing
schemes. We strategically started our research by exploring the evolution of Opportunistic
networks, and then implemented the rogue behavior by utilizing The ONE (Opportunistic
Network Environment, by Nokia Research Centre) simulator to carry out our research over rogue
behavior. The ONE simulator is an open source simulator developed in Java, simulating the layer
3 of the OSI model. The Rogue behavior is implemented in the simulator to observe the effect of
rogue nodes. Finally we extracted the desired dataset to measure the latency by carefully
simulating the intended behavior, keeping rest of the parameters (e.g. Node Movement Models,
Signal Range and Strength, Point of Interest (POI) etc) unchanged. Our results are encouraging,
and coincide with the average latency deterioration patterns as modeled by the previous
researchers, with a few exceptions. The practical implementation of plug-in in ONE simulator has
shown that only a very high degree of rogue nodes impact the latency, making OppNets more
resilient and less vulnerable to malicious attacks
Content storage and retrieval mechanisms for vehicular delay-tolerant networks
Vehicular delay-tolerant networks (VDTNs) were proposed as a novel disruptive network concept based on the delay tolerant networking (DTN) paradigm. VDTN architecture uses vehicles to relay messages, enabling
network connectivity in challenging scenarios. Due to intermittent connectivity, network nodes carry messages in their buffers, relaying them only when a proper contact opportunity occurs. Thus, the storage capacity and message retrieving of intermediate nodes directly affects the network performance. Therefore, efficient and robust caching and forwarding mechanisms are needed. This dissertation proposes a content storage and retrieval (CSR) solution for VDTN networks. This solution consists on storage
and retrieval control labels, attached to every data bundle of aggregated network traffic. These labels define cacheable contents, and apply cachecontrol and forwarding restrictions on data bundles. The presented mechanisms gathered several contributions from cache based technologies
such as Web cache schemes, ad-hoc and DTN networks. This solution is fully automated, providing a fast, safe, and reliable data transfer and storage management, while improves the applicability and performance of VDTN
networks significantly. This work presents the performance evaluation and validation of CSR mechanisms through a VDTN testbed. Furthermore it presents several network performance evaluations and results using the
well-known DTN routing protocols, Epidemic and Spray and Wait (including its binary variant). The comparison of the network behavior and performance on both protocols, with and without CSR mechanisms, proves
that CSR mechanisms improve significantly the overall network performance
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
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