1,002 research outputs found
Prediction-enhanced Routing in Disruption-tolerant Satellite Networks
This thesis introduces a framework for enhancing DTN (Delay-/Disruption-Tolerant Networking) routing in dynamic LEO satellite constellations based on the prediction of contacts.
The solution is developed with a clear focus on the requirements imposed by the 'Ring Road' use case, mandating a concept for dynamic contact prediction and its integration into a state-of-the-art routing approach.
The resulting system does not restrict possible applications to the 'Ring Road,' but allows for flexible adaptation to further use cases.
A thorough evaluation shows that employing proactive routing in concert with a prediction mechanism offers significantly improved performance when compared to alternative opportunistic routing techniques
Coherent, automatic address resolution for vehicular ad hoc networks
Published in: Int. J. of Ad Hoc and Ubiquitous Computing, 2017 Vol.25, No.3, pp.163 - 179. DOI: 10.1504/IJAHUC.2017.10001935The interest in vehicular communications has increased notably. In this paper, the use of the address resolution (AR) procedures is studied for vehicular ad hoc networks (VANETs). We analyse the poor performance of AR transactions in such networks and we present a new proposal called coherent, automatic address resolution (CAAR). Our approach inhibits the use of AR transactions and instead increases the usefulness of routing signalling to automatically match the IP and MAC addresses. Through extensive simulations in realistic VANET scenarios using the Estinet simulator, we compare our proposal CAAR to classical AR and to another of our proposals that enhances AR for mobile wireless networks, called AR+. In addition, we present a performance evaluation of the behaviour of CAAR, AR and AR+ with unicast traffic of a reporting service for VANETs. Results show that CAAR outperforms the other two solutions in terms of packet losses and furthermore, it does not introduce additional overhead.Postprint (published version
Previous hop routing: exploiting opportunism in VANETs
Routing in highly dynamic wireless networks such as Vehicular Ad-hoc Networks
(VANETs) is a challenging task due to frequent topology changes. Sustaining
a transmission path between peers in such network environment is difficult. In
this thesis, Previous Hop Routing (PHR) is poposed; an opportunistic forwarding
protocol exploiting previous hop information and distance to destination to
make the forwarding decision on a packet-by-packet basis. It is intended for use in
highly dynamic network where the life time of a hop-by-hop path between source
and destination nodes is short. Exploiting the broadcast nature of wireless communication
avoids the need to copy packets, and enables redundant paths to be
formed. To save network resources, especially under high network loads, PHR
employs probabilistic forwarding. The forwarding probability is calculated based
on the perceived network load as measured by the arrival rate at the network
interface. We evaluate PHR in an urban VANET environment using NS2 (for
network traffic) and SUMO (for vehicular movement) simulators, with scenarios
configured to re
ect real-world conditions. The simulation scenarios are configured
to use two velocity profiles i.e. Low and high velocity. The results show that the
PHR networks able to achieve best performance as measured by Packet Delivery
Ratio (PDR) and Drop Burst Length (DBL) compared to conventional routing
protocols in high velocity scenarios
Design and implementation of simulation tools, protocols and architectures to support service platforms on vehicular networks
Tesis por compendioProducts related with Intelligent Transportation Systems (ITS) are becoming
a reality on our roads.
All car manufacturers are starting to include Internet
access in their vehicles and to integrate smartphones directly from the
dashboard, but more and more services will be introduced in the near future.
Connectivity through "vehicular networks" will become a cornerstone of every
new proposal, and offering an adequate quality of service is obviously desirable.
However, a lot of work is needed for vehicular networks to offer performances
similar to those of the wired networks.
Vehicular networks can be characterized by two main features: high variability
due to mobility levels that can reach up to 250 kilometers per hour,
and heterogeneity, being that various competing versions from different vendors
have and will be released. Therefore, to make the deployment of efficient
services possible, an extensive study must be carried out and adequate tools
must be proposed and developed. This PhD thesis addresses the service deployment
problem in these networks at three different levels: (i) the physical
and link layer, showing an exhaustive analysis of the physical channel and
models; (ii) the network layer, proposing a forwarding protocol for IP packets;
and (iii) the transport layer, where protocols are proposed to improve data
delivery.
First of all, the two main wireless technologies used in vehicular networks
where studied and modeled, namely the 802.11 family of standards, particularly
802.11p, and the cellular networks focusing on LTE. Since 802.11p is a
quite mature standard, we defined (i) a propagation and attenuation model
capable of replicating the transmission range and the fading behavior of real
802.11p devices, both in line-of-sight conditions and when obstructed by small
obstacles, and (ii) a visibility model able to deal with large obstacles, such
as buildings and houses, in a realistic manner.
Additionally, we proposed a
model based on high-level performance indicators (bandwidth and delay) for
LTE, which makes application validation and evaluation easier.
At the network layer, a hybrid protocol called AVE is proposed for packet
forwarding by switching among a set of standard routing strategies. Depending
on the specific scenario, AVE selects one out of four different routing solutions:
a) two-hop direct delivery, b) Dynamic MANET On-demand (DYMO), c)
greedy georouting, and d) store-carry-and-forward technique, to dynamically
adapt its behavior to the specific situation.
At the transport layer, we proposed a content delivery protocol for reliable
and bidirectional unicast communication in lossy links that improves content
delivery in situations where the wireless network is the bottleneck.
It has
been designed, validated, optimized, and its performance has been analyzed
in terms of throughput and resource efficiency.
Finally, at system level, we propose an edge-assisted computing model that
allows reducing the response latency of several queries by placing a computing
unit at the network edge. This way, traffic traversal through the Internet is
avoided when not needed.
This scheme could be used in both 802.11p and
cellular networks, and in this thesis we decided to focus on its evaluation using
LTE networks.
The platform presented in this thesis combines all the individual efforts to
create a single efficient platform. This new environment could be used by any
provider to improve the quality of the user experience obtainable through the
proposed vehicular network-based services.Los productos relacionados con los Sistemas Inteligentes de Transporte (ITS)
se están transformando en una realidad en nuestras carreteras. Todos los
fabricantes de coches comienzan a incluir acceso a internet en sus vehículos y a
facilitar su integración con los teléfonos móviles, pero más y más servicios se
introducirán en el futuro.
La conectividad usando las "redes vehiculares" se
convertirá en la piedra angular de cada nueva propuesta, y ofrecer una calidad
de servicio adecuada será, obviamente, deseable. Sin embargo, se necesita
una gran cantidad de trabajo para que las redes vehiculares ofrezcan un
rendimiento similar al de las redes cableadas.
Las redes vehiculares quedan definidas por sus dos características básicas:
alto dinamismo, pues los nodos pueden alcanzar una velocidad relativa de más
de 250 km/h; y heterogeneidad, por la gran cantidad de propuestas diferentes
que los fabricantes están lanzando al mercado. Por ello, para hacer posible el
despliegue de servicios sobre ellas, se impone la necesidad de hacer un estudio
en profundidad de este entorno, y deben de proponerse y desarrollarse las
herramientas adecuadas.
Esta tesis ataca la problemática del despliegue de servicios en estas redes
a tres niveles diferentes: (i) el nivel físico y de enlace, mostrando varios análisis
en profundidad del medio físico y modelos derivados para su simulación;
(ii) el nivel de red, proponiendo un protocolo de difusión de la información
para los paquetes IP; y (iii) el nivel de transporte, donde otros protocolos son
propuestos para mejorar el rendimiento del transporte de datos.
En primer lugar, se han estudiado y modelado las dos principales tecnologías
inalámbricas que se utilizan para la comunicación en redes vehiculares,
la rama de estándares 802.11, en concreto 802.11p; y la comunicación celular,
en particular LTE. Dado que el estándar 802.11p es un estándar bastante
maduro, nos centramos en crear (i) un modelo de propagación y atenuación
capaz de replicar el rango de transmisión de dispositivos 802.11p reales, en
condiciones de visión directa y obstrucción por pequeños obstáculos, y (ii) un
modelo de visibilidad capaz de simular el efecto de grandes obstáculos, como
son los edifcios, de una manera realista.
Además, proponemos un modelo
basado en indicadores de rendimiento de alto nivel (ancho de banda y retardo)
para LTE, que facilita la validación y evaluación de aplicaciones.
En el plano de red, se propone un protocolo híbrido, llamado AVE, para
el encaminamiento y reenvío de paquetes usando un conjunto de estrategias
estándar de enrutamiento. Dependiendo del escenario, AVE elige entre cuatro
estrategias diferentes: a) entrega directa a dos saltos, b) Dynamic MANET
On-demand (DYMO) c) georouting voraz, y d) una técnica store-carry-and-
forward, para adaptar su comportamiento dinámicamente a cada situación.
En el plano de transporte, se propone un protocolo bidireccional de distribución
de contenidos en canales con pérdidas que mejora la entrega de contenidos
en situaciones en las que la red es un cuello de botella, como las redes
inalámbricas.
Ha sido diseñado, validado, optimizado, y su rendimiento ha
sido analizado en términos de productividad y eficiencia en la utilización de
recursos.
Finalmente, a nivel de sistema, proponemos un modelo de computación
asistida que permite reducir la latencia en la respuesta a muchas consultas
colocando una unidad de computación en el borde de la red, i.e., la red de
acceso. Este esquema podría ser usado en redes basadas en 802.11p y en redes
celulares, si bien en esta tesis decidimos centrarnos en su evaluación usando
redes LTE.
La plataforma presentada en esta tesis combina todos los esfuerzos individuales
para crear una plataforma única y eficiente. Este nuevo entorno puede
ser usado por cualquier proveedor para mejorar la calidad de la experiencia de
usuario en los servicios desplegados sobre redes vehiculares.Els productes relacionats amb els sistemes intel · ligents de transport (ITS)
s'estan transformant en una realitat en les nostres carreteres. Tots els fabri-
cants de cotxes comencen a incloure accés a internet en els vehicles i a facilitar-
ne la integració amb els telèfons mòbils, però en el futur més i més serveis s'hi
introduiran. La connectivitat usant les xarxes vehicular esdevindrà la pedra
angular de cada nova proposta, i oferir una qualitat de servei adequada serà,
òbviament, desitjable.
No obstant això, es necessita una gran quantitat de
treball perquè les xarxes vehiculars oferisquen un rendiment similar al de les
xarxes cablejades.
Les xarxes vehiculars queden definides per dues característiques bàsiques:
alt dinamisme, ja que els nodes poden arribar a una velocitat relativa de més
de 250 km/h; i heterogeneïtat, per la gran quantitat de propostes diferents
que els fabricants estan llançant al mercat.
Per això, per a fer possible el
desplegament de serveis sobre aquestes xarxes, s'imposa la necessitat de fer un
estudi en profunditat d'aquest entorn, i cal proposar i desenvolupar les eines
adequades.
Aquesta tesi ataca la problemàtica del desplegament de serveis en aquestes
xarxes a tres nivells diferents: (i) el nivell físic i d'enllaç , mostrant diverses
anàlisis en profunditat del medi físic i models derivats per simular-lo; (ii) el
nivell de xarxa, proposant un protocol de difusió de la informació per als
paquets IP; i (iii) el nivell de transport, on es proposen altres protocols per a
millorar el rendiment del transport de dades.
En primer lloc, s'han estudiat i modelat les dues principals tecnologies
sense fils que s'utilitzen per a la comunicació en xarxes vehiculars, la branca
d'estàndards 802.11, en concret 802.11p; i la comunicació cel · lular, en partic-
ular LTE. Atès que l'estàndard 802.11p és un estàndard bastant madur, ens
centrem a crear (i) un model de propagació i atenuació capaç de replicar el
rang de transmissió de dispositius 802.11p reals, en condicions de visió directa
i obstrucció per petits obstacles, i (ii) un model de visibilitat capaç de simular
l'efecte de grans obstacles, com són els edificis, d'una manera realista. A més,
proposem un model basat en indicadors de rendiment d'alt nivell (ample de
banda i retard) per a LTE, que facilita la validació i l'avaluació d'aplicacions.
En el pla de xarxa, es proposa un protocol híbrid, anomenat AVE, per
a l'encaminament i el reenviament de paquets usant un conjunt d'estratègies
estàndard d'encaminament.
Depenent de l'escenari , AVE tria entre quatre
estratègies diferents: a) lliurament directe a dos salts, b) Dynamic MANET
On-demand (DYMO) c) georouting voraç, i d) una tècnica store-carry-and-
forward, per a adaptar-ne el comportament dinàmicament a cada situació.
En el pla de transport, es proposa un protocol bidireccional de distribució
de continguts en canals amb pèrdues que millora el lliurament de continguts
en situacions en què la xarxa és un coll de botella, com les xarxes sense fils.
Ha sigut dissenyat, validat, optimitzat, i el seu rendiment ha sigut analitzat
en termes de productivitat i eficiència en la utilització de recursos.
Finalment, a nivell de sistema, proposem un model de computació assistida
que permet reduir la latència en la resposta a moltes consultes col · locant una
unitat de computació a la vora de la xarxa, és a dir, la xarxa d'accés. Aquest
esquema podria ser usat en xarxes basades en 802.11p i en xarxes cel · lulars, si
bé en aquesta tesi decidim centrar-nos en la seua avaluació usant xarxes LTE.
La plataforma presentada en aquesta tesi combina tots els esforços indi-
viduals per a crear una plataforma única i eficient. Aquest nou entorn pot ser
usat per qualsevol proveïdor per a millorar la qualitat de l'experiència d'usuari
en els serveis desplegats sobre xarxes vehiculars.Báguena Albaladejo, M. (2017). Design and implementation of simulation tools, protocols and architectures to support service platforms on vehicular networks [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/85333TESISCompendi
SSOPS based Solution to Improve QoS in VANET
Vehicular Ad-hoc Networks (VANETs) is an emerging network technology derived from ad-hoc networks. This paper provides the state-of-the-art of VANETs and provides optimum proposal by improving Quality of Service (QoS.) Today, wireless systems are preferred over wired systems and these are gaining popularity as it provides wireless connectivity to the users irrespective of their geographic position, VANET is one of them. VANETs are installed to minimize the risk of road accidents and to improve passenger comfort by permitting the vehicles to exchange various types of data. In this paper, the Signal Strength based Optimum Path Selection (SSOPS) based solution on how to mitigate the QoS issues that exists while using the existing methods are discussed. Moreover, the solution has been tested using NS2 software using various parameters
Efficient and adaptive congestion control for heterogeneous delay-tolerant networks
Detecting and dealing with congestion in delay-tolerant networks (DTNs) is an important and challenging problem. Current DTN forwarding algorithms typically direct traffic towards more central nodes in order to maximise delivery ratios and minimise delays, but as traffic demands increase these nodes may become saturated and unusable. We pro- pose CafRep, an adaptive congestion aware protocol that detects and reacts to congested nodes and congested parts of the network by using implicit hybrid contact and resources congestion heuristics. CafRep exploits localised relative utility based approach to offload the traffic from more to less congested parts of the network, and to replicate at adaptively lower rate in different parts of the network with non-uniform congestion levels. We extensively evaluate our work against benchmark and competitive protocols across a range of metrics over three real connectivity and GPS traces such as Sassy [44], San Francisco Cabs [45] and Infocom 2006 [33]. We show that CafRep performs well, independent of network connectivity and mobility patterns, and consistently outperforms the state-of-the-art DTN forwarding algorithms in the face of increasing rates of congestion. CafRep maintains higher availability and success ratios while keeping low delays, packet loss rates and delivery cost. We test CafRep in the presence of two application scenarios, with fixed rate traffic and with real world Facebook application traffic demands, showing that regardless of the type of traffic CafRep aims to deliver, it reduces congestion and improves forwarding performance
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