Spelling suggestions: "subject:"adhoc networks"" "subject:"ad'hoc networks""
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Συγκριτική μελέτη της απόδοσης αλγορίθμων δρομολόγησης αυτοοργανούμενων δικτύωνΠαπαδόπουλος, Χαράλαμπος 01 August 2014 (has links)
Στα αυτοοργανούμενα ασύρματα δίκτυα, αυτόνομοι κόμβοι με κάρτες ασύρματης μετάδοσης σχηματίζουν ένα δίκτυο χωρίς προυπάρχουσα δομή. Η δρομολόγηση σε ένα συμβατικό δίκτυο γίνεται από ειδικούς δρομολογητές, είτε υλοποιημένους σε υλικό ειδικά για αυτό το σκοπό, ή κατάλληλους υπολογιστές. Αντίθετα, σε ένα adhoc δίκτυο, η δρομολόγηση διεκπεραιώνεται από τους ίδιους τους κόμβους. Κάθε κόμβος έχει τη δυνατότητα να προωθεί δικτυακό φορτίο στους υπόλοιπους. Οι κόμβοι σε ένα ad hoc δίκτυο προσφέρονται να προωθήσουν την δικτυακή κίνηση εκ μέρους άλλων κόμβων. Η λειτουργικότητα του ad hoc δικτύου εξαρτάται σημαντικά από την ικανότητα προώθησης πακέτων των κόμβων του. Συνεπώς καταλαβαίνουμε ότι ο αλγόριθμος δρομολόγησης του ad-hoc δικτύου διαδραματίζει σημαντικό ρόλο στην απόδοσή του. Βασικός σκοπός αυτής της διπλωματικής εργασίας είναι να μελετήσει την απόδοση μερικών βασικών αλγορίθμων δρομολόγησης ως προς κάποιες μετρήσιμες παραμέτρους. / In ad hoc wireless networks, autonomous nodes with wireless transmission cards form a network without pre-existing structure. Routing in a conventional network is performed by special routers , either in hardware implementations specifically for this purpose, or by appropriate computers. Conversely, in an adhoc network, routing is handled by the nodes themselves. Each node has the ability to forward the other nodes' load. The nodes in an ad hoc network offer to promote the network traffic from other nodes. The functionality of the ad hoc network depends significantly on the performance of packet forwarding of the nodes. Therefore we understand that the routing algorithm of ad-hoc network plays an important role in performance. The main purpose of this thesis is to study the performance of some key routing algorithms for some measurable parameters.
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Performance analysis of new algorithms for routing in mobile ad-hoc networks : the development and performance evaluation of some new routing algorithms for mobile ad-hoc networks based on the concepts of angle direction and node densityElazhari, Mohamed S. January 2010 (has links)
Mobile Ad hoc Networks (MANETs) are of great interest to researchers and have become very popular in the last few years. One of the great challenges is to provide a routing protocol that is capable of offering the shortest and most reliable path in a MANET in which users are moving continuously and have no base station to be used as a reference for their position. This thesis proposes some new routing protocols based on the angles (directions) of the adjacent mobile nodes and also the node density. In choosing the next node in forming a route, the neighbour node with the closest heading angle to that of the node of interest is selected, so the connection between the source and the destination consists of a series of nodes that are moving in approximately the same direction. The rationale behind this concept is to maintain the connection between the nodes as long as possible. This is in contrast to the well known hop count method, which does not consider the connection lifetime. We propose three enhancements and modifications of the Ad-hoc on demand distance vector (AODV) protocol that can find a suitable path between source and destination using combinations and prioritization of angle direction and hop count. Firstly, we consider that if there are multiple routing paths available, the path with the minimum hop count is selected and when the hop counts are the same the path with the best angle direction is selected. Secondly, if multiple routing paths are available the paths with the best angle direction are chosen but if the angles are the same (fall within the same specified segment), the path with minimum hop count is chosen. Thirdly, if there is more than one path available, we calculate the average of all the heading angles in every path and find the best one (lowest average) from the source to the destination. In MANETs, flooding is a popular message broadcasting technique so we also propose a new scheme for MANETS where the value of the rebroadcast packets for every host node is dynamically adjusted according to the number of its neighbouring nodes. A fixed probabilistic scheme algorithm that can dynamically adjust the rebroadcasting probability at a given node according to its ID is also proposed; Fixed probabilistic schemes are one of the solutions to reduce rebroadcasts and so alleviate the broadcast storm problem. Performance evaluation of the proposed schemes is conducted using the Global Mobile Information System (GloMoSim) network simulator and varying a number of important MANET parameters, including node speed, node density, number of nodes and number of packets, all using a Random Waypoint (RWP) mobility model. Finally, we measure and compare the performance of all the proposed approaches by evaluating them against the standard AODV routing protocol. The simulation results reveal that the proposed approaches give relatively comparable overall performance but which is better than AODV for almost all performance measures and scenarios examined.
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City Mobility Model with Google Earth VisualizationAndersson, Henrik, Oreland, Peter January 2007 (has links)
<p>Mobile Ad Hoc Networks are flexible, self configuring networks that do not need a fixed infrastructure. When these nets are simulated, mobility models can be used to specify node movements. The work in this thesis focuses on designing an extension of the random trip</p><p>mobility model on a city section from EPFL (Swiss federal institute of technology). Road data is extracted from the census TIGER database, displayed in Google Earth and used as input for the model. This model produces output that can be used in the open source network simulator ns-2.</p><p>We created utilities that take output from a database of US counties, the TIGER database, and convert it to KML. KML is an XML based format used by Google Earth to store geographical data, so that it can be viewed in Google Earth. This data will then be used as input to the modified mobility model and finally run through the ns-2 simulator. We present some NAM traces, a network animator that will show node movements over time.</p><p>We managed to complete most of the goals we set out, apart from being able to modify node positions in Google Earth. This was skipped because the model we modified had an initialization phase that made node positions random regardless of initial position. We were also asked to add the ability to set stationary nodes in Google Earth; this was not added due to time constraints.</p>
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A Middleware for Targeted Marketing in Spontaneous Social CommunitiesTian, Zhao 27 September 2012 (has links)
With the proliferation of mobile devices and wireless connectivity technologies, mobile social communities offer novel opportunities for targeted marketing by service or product providers. Unfortunately, marketers are still unable to realize the full potential of these markets due to their inability to effectively target right audiences. This thesis presents a novel middleware for identifying spontaneous social communities (SSCs) of mobile users in ad hoc networks in order to facilitate marketers' advertisements. The contributions of the presented work are two fold; the first is a novel model for SSCs that captures their unique dynamic nature, in terms of community structure and interest in different \textit{hot-topics} over time. These time-varying interests are represented through an inferred \textit{community profile prototype} that reflects dominant characteristics of community members. This prototype is then employed to facilitate the identification of new potential members. The selected community prototypes are also used by marketers to identify the right communities for their services or products promotions. The second contribution of this paper is novel distributed techniques for efficient calculation of the community prototypes and identification of potential community links. In contrast to traditional models of detecting fixed and mobile social networks that rely on pre-existing friendships among its members to predict new ones, the proposed model focuses on measuring the degree of similarity between the new user's profile and the profiles of members of each community in order to predict new users' relationships in the community. The adopted model of SSCs can foster many existing and new socially-aware applications such as recommender systems for social events and tools for collaborative work. It is also an ideal target for business-oriented applications such as short-message-service (SMS) advertisement messages, podcasting news feeds in addition to location/context-aware services. The performance of the proposed work was evaluated using the NetLogo platform where obtained experimental results demonstrate the achieved high degree of stability in the resulting communities in addition to the effectiveness of the proposed middleware in terms of the reduction in the number of routing messages required for advertisements.
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Improving fairness and utilisation in ad hoc networksArabi, Mohamed January 2012 (has links)
Ad hoc networks represent the current de-facto alternative for infrastructure-less environments, due to their self-configuring and resilience characteristics. Ad hoc networks flexibility benefits, such as unrestrained computing, lack of centralisation, and ease of deployment at low costs, are tightly bound with relevant deficiencies such as limited resources and management difficulty. Ad hoc networks witnessed high attention from the research community due to the numerous challenges faced when deploying such a technology in real scenarios. Starting with the nature of the wireless environment, which raises significant transmission issues when compared with the wired counterpart, ad hoc networks require a different approach when addressing the data link problems. Further, the high packet loss due to wireless contention, independent of network congestion, requires a different approach when considering quality of service degradation and unfair channel resources distribution among competing flows. Although these issues have already been considered to some extent by researchers, there is still room to improve quality of service by reducing the effect of packet loss and fairly distributing the medium access among competing nodes. The aim of this thesis is to propose a set of mechanisms to alleviate the effect of packet loss and to improve fairness in ad hoc networks. A transport layer algorithm has been proposed to overcome the effects of hidden node collisions and to reduce the impact of wireless link contention by estimating the four hop delay and pacing packet transmissions accordingly. Furthermore, certain topologies have been identified, in which the standard IEEE 802.11 faces degradation in channel utilisation and unfair bandwidth allocation. Three link layer mechanisms have been proposed to tackle the challenges the IEEE 802.11 faces in the identified scenarios to impose fairness in ad hoc networks through fairly distributing channel resources between competing nodes. These mechanisms are based on monitoring the collision rate and penalising the greedy nodes where no competing nodes can be detected but interference exists, monitoring traffic at source nodes to police access to the channel where only source nodes are within transmission range of each other, and using MAC layer acknowledgements to flag unfair bandwidth allocation in topologies where only the receivers are within transmission range of each other. The proposed mechanisms have been integrated into a framework designed to adapt and to dynamically select which mechanism to adopt, depending on the network topology. It is important to note that the proposed mechanisms and framework are not alternatives to the standard MAC protocol but are an enhancement and are triggered by the failure of the IEEE 802.11 protocol to distribute the channel resources fairly. All the proposed mechanisms have been validated through simulations and the results obtained from the experiments show that the proposed schemes fairly distribute channel resources fairly and outperform the performance of the IEEE 802.11 protocol in terms of channel utilisation as well as fairness.
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Bounded Dynamic Source Routing in Mobile Ad Hoc NetworksGeorge, Glyco 08 1900 (has links)
A mobile ad hoc network (MANET) is a collection of mobile platforms or nodes that come together to form a network capable of communicating with each other, without the help of a central controller. To avail the maximum potential of a MANET, it is of great importance to devise a routing scheme, which will optimize upon the performance of a MANET, given the high rate of random mobility of the nodes. In a MANET individual nodes perform the routing functions like route discovery, route maintenance and delivery of packets from one node to the other. Existing routing protocols flood the network with broadcasts of route discovery messages, while attempting to establish a route. This characteristic is instrumental in deteriorating the performance of a MANET, as resource overhead triggered by broadcasts is directly proportional to the size of the network. Bounded-dynamic source routing (B-DSR), is proposed to curb this multitude of superfluous broadcasts, thus enabling to reserve valuable resources like bandwidth and battery power. B-DSR establishes a bounded region in the network, only within which, transmissions of route discovery messages are processed and validated for establishing a route. All route discovery messages reaching outside of this bounded region are dropped, thus preventing the network from being flooded. In addition B-DSR also guarantees loop-free routing and is robust for a rapid recovery when routes in the network change.
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Reliable Multicast in Mobile Ad Hoc Wireless NetworksKlos, Lawrence 20 December 2009 (has links)
A mobile wireless ad hoc network (MANET) consists of a group of mobile nodes communicating wirelessly with no fixed infrastructure. Each node acts as source or receiver, and all play a role in path discovery and packet routing. MANETs are growing in popularity due to multiple usage models, ease of deployment and recent advances in hardware with which to implement them. MANETs are a natural environment for multicasting, or group communication, where one source transmits data packets through the network to multiple receivers. Proposed applications for MANET group communication ranges from personal network apps, impromptu small scale business meetings and gatherings, to conference, academic or sports complex presentations for large crowds reflect the wide range of conditions such a protocol must handle. Other applications such as covert military operations, search and rescue, disaster recovery and emergency response operations reflect the "mission critical" nature of many ad hoc applications. Reliable data delivery is important for all categories, but vital for this last one. It is a feature that a MANET group communication protocol must provide. Routing protocols for MANETs are challenged with establishing and maintaining data routes through the network in the face of mobility, bandwidth constraints and power limitations. Multicast communication presents additional challenges to protocols. In this dissertation we study reliability in multicast MANET routing protocols. Several on-demand multicast protocols are discussed and their performance compared. Then a new reliability protocol, R-ODMRP is presented that runs on top of ODMRP, a well documented "best effort" protocol with high reliability. This protocol is evaluated against ODMRP in a standard network simulator, ns-2. Next, reliable multicast MANET protocols are discussed and compared. We then present a second new protocol, Reyes, also a reliable on-demand multicast communication protocol. Reyes is implemented in the ns-2 simulator and compared against the current standards for reliability, flooding and ODMRP. R-ODMRP is used as a comparison point as well. Performance results are comprehensively described for latency, bandwidth and reliable data delivery. The simulations show Reyes to greatly outperform the other protocols in terms of reliability, while also outperforming R-ODMRP in terms of latency and bandwidth overhead.
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[en] LOCATION BASED ROUTING IN AD-HOC NETWORKS / [pt] ROTEAMENTO BASEADO EM LOCALIZAÇÃO EM REDES AD HOCJOSE ANTONIO CASEMIRO NETO 26 March 2008 (has links)
[pt] Um avanço importante gerado pela tecnologia de TV digital
é
a possibilidade de interatividade com os usuários,
realizada por meio do assim chamado canal de retorno. As
redes ad hoc têm um grande potencial para atender esse
tipo
de serviço, pois podem ser empregadas em diversas áreas
geográficas e idealmente de forma independente de infra-
estrutura. Isso diminui o seu custo e propícia o aumento
da
velocidade de implantação deste tipo de rede. Uma das
principais questões técnicas a serem resolvidas no
contexto
das redes móveis ad hoc é a necessidade de algoritmos
eficientes para a realização do roteamento dos pacotes. O
projeto Terminodes, desenvolvido pelo Instituto Federal
de
Tecnologia da Suíça, desenvolveu um protocolo de
roteamento
que utiliza a informação de localização. Este método de
roteamento é freqüentemente proposto como um meio para
prover escalabilidade em redes ad hoc distribuídas sobre
áreas geográficas extensas. O roteamento baseado em
localização é difícil quando há áreas de exclusão na
topologia da rede e os nós são móveis ou freqüentemente
desconectados para fins de economia de bateria. Portanto,
a
investigação da robustez do protocolo para esses casos é
fundamental para avaliar seu uso em redes que podem
servir
como canal de retorno de TV digital. / [en] An important advance generated by the technology of digital
TV is the possibility of interactivity with the users, what
is done by means of the return channel. The mobile ad hoc
networks have a great potential to provide this type of
service, because it can ideally be used in diverse
geographic areas and independent of any infrastructure.
This minimizes the costs and the time needed to implement
the network for this canal. One of the main questions
techniques in the context of the mobile ad hoc networks is
the necessity of efficient routing algorithms. The
Terminodes project, developed by the Federal Institute of
Technology of Switzerland, developed a routing protocol
that is based in location information. This routing method
frequently is a way to provide scalability in
large ad hoc networks. The routing based on location is
difficult when it has areas of exclusion in the topology of
the network and the nodes are mobile or they are
frequently disconnected to save battery. Therefore, assess
the robustness of the protocol for these cases is basic to
evaluate its use in networks for the digital TV return
channel.
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Conditional Privacy-Preserving Authentication Protocols for Vehicular Ad Hoc NetworksLi, Jiliang 17 May 2019 (has links)
No description available.
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Smart Adaptive Beaconing Schemes for VANETUnknown Date (has links)
Vehicular Ad hoc Networks (VANET) is a wireless ad-hoc network that includes
two types of communications, Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure
(V2I). In VANET there are two types of messages. The first type is the event-driven
messages that are only triggered in case of emergency. The second type is the periodical
messages named beacons that are exchanged frequently between vehicles. A
beacon message contains basic information about the sending vehicle such as id, location
and velocity. Beacons are frequently exchanged to increase the cooperative
awareness between vehicles. Increasing beacon frequency helps increasing neighborhood
awareness and improving information accuracy. However, this causes more
congestion in the network, specially when the number of vehicles increases. On the
other hand, reducing beacon frequency alleviates network congestion, but results in
out-dated information.
In this dissertation, we address the aforementioned challenges and propose a
number of smart beaconing protocols and evaluate their performance in di↵erent environments
and network densities. The four adaptive beaconing protocols are designed
to increase the cooperative awareness and information freshness, while alleviating the network congestion. All the proposed protocols take into account the most important
aspects, which are critical to beaconing rate adaptation. These aspects include channel
status, traffic conditions and link quality. The proposed protocols employ fuzzy
logic-based techniques to determine the congestion rank, which is used to adjust beacon
frequency.
The first protocol considers signal to interference-noise ratio (SINR), number
of neighboring nodes and mobility to determine the congestion rank and adjust the
beacon rate accordingly. This protocol works well in sparse conditions and highway
environments. The second protocol works well in sparse conditions and urban environments.
It uses channel busy time (CBT), mobility and packet delivery ratio
(PDR) to determine the congestion rank and adjust the beacon rate. The third protocol
utilizes CBT, SINR, PDR, number of neighbors and mobility as inputs for the
fuzzy logic system to determine the congestion rank and adjust the beacon rate. This
protocol works well in dense conditions in both highway and urban environments.
Through extensive simulation experiments, we established that certain input
parameters are more e↵ective in beacon rate adaptation for certain environments
and conditions. Based on this, we propose a high awareness and channel efficient
scheme that adapts to di↵erent environments and conditions. First, the protocol
estimates the network density using adaptive threshold function. Then, it looks at
the spatial distribution of nodes using the quadrat method to determine whether
the environment is highway or urban. Based on the density conditions and nodes
distribution, the protocol utilizes the appropriate fuzzy input parameters to adapt
the beaconing rate. In addition, the protocol optimizes the performance by adapting
the transmission power based on network density and nodes distribution.
Finally, an investigation of the impact of adaptive beaconing on broadcasting
is conducted. The simulation results confirm that our adaptive beaconing scheme
can improve performance of the broadcast protocols in terms of reachability and bandwidth consumption when compared to a fixed rate scheme. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection
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