9 research outputs found

    Flooding control in route discovery for reactive routing in mobile ad hoc networks

    Get PDF
    Routing is a very important function in the network layer of the OSI model for wired and wireless networks. Mobile Ad hoc Networks (MANETs) are a collection of wireless nodes forming a temporary network that is supposed to be constructed on the fly without infrastructure and prior setup. This fashion of setup demands that the nodes act as routers for other nodes. This necessitates the need of a robust dynamic routing scheme. Routing protocols are classified into three main categories: proactive, reactive, and hybrid. Reactive routing has been the focus of research in recent years due to its control traffic overhead reduction. Reactive routing operation involves three main steps: route discovery, packet delivery, and route maintenance. If a source node, initiating the message, knows the route to the destination, this route is used to transmit the message; otherwise, the source node will initiate a route discovery algorithm to build the route, which highlights the importance of this phase of the on-demand routing process. This thesis work will present a route discovery algorithm that will try to find the route between the sender and the intended receiver in relatively short periods of end-to-end delay, least amount of control traffic overhead, and a loop free path between the two communicating parties. Furthermore, performance comparison between the proposed algorithm and other standard algorithms, namely basic flooding and flooding with self-pruning, will be conducted. The proposed route discovery algorithm can be used in several approaches serving ad hoc network setup, where connectivity establishment and maintenance is important

    Cross-Layer Design for QoS Routing in Multi-Hop Wireless Networks

    Get PDF
    Mobile Ad Hoc Networks (MANETs) are gaining increasing popularity in recent years because of their ease of deployment. They are distributed, dynamic, and self-configurable without infrastructure support. Routing in ad hoc networks is a challenging task because of the MANET dynamic nature. Hence, researchers were focused in designing best-effort distributed and dynamic routing protocols to ensure optimum network operations in an unpredictable wireless environment. Nowadays, there is an increased demand on multimedia applications (stringent delay and reliability requirements), which makes a shift from best-effort services to Quality of Services. Actually, the challenge in wireless ad hoc networks is that neighbor nodes share the same channel and they take part in forwarding packets. Therefore, the total effective channel capacity is not only limited by the raw channel capacity but is also limited by the interactions and interferences among neighboring nodes. Thus, such factors should be taken in consideration in order to offer QoS routing. While, some of the distributed QoS route selection algorithms assume the availability of such information, others propose mechanisms to estimate them. The goals of this thesis are: (i) to analyze the performance of IEEE 802.11 MAC mechanism in non-saturation conditions, (ii) to use the analysis in the context of multi-hop ad hoc networks, (iii) to derive theoretical limits for nodes performance in multi-hop ad hoc networks, (iv) to use the multi-hop analysis in QoS route selection. We start the thesis by proposing a discrete-time 3D Markov chain model to analyze the saturation performance of the RTS/CTS access mode. This model integrates the backoff countdown process, retransmission retry limits, and transmission errors into one model. The impact of system parameters (e.g., number of nodes, packet size, retry limits, and BERs) are analyzed. Next, we extend the 3D model to analyze the performance under non-saturation conditions and finite buffer capacity using two different approaches. First, we extend the 3D model into a 4D model to integrate the transmission buffer behavior. Second, we replace the 4D model by an M/G/1/K queueing system model with independent samples from the saturation analysis. The latter model gives similar results as the former but with a reduction in the analysis complexity. Next and by means of the non-saturation analysis, we proposed an approximate mathematical model for multi-hop ad hoc networks. Furthermore, we proposed an iterative mechanism to estimate the throughput in the presence of multiple flows. Finally, we used the multi-hop analysis to propose a QoS route selection algorithm. In this algorithm, we concentrate on the throughput as a QoS parameter. However, the proposed algorithm is valid to be used with other QoS parameters, such as packet delay, packet loss probability, and fairness. Analytical and simulation results show the deficiency of the current route selection algorithm in AODV and at the same time verifies the need for QoS route selection algorithms

    Mobile Ad-Hoc Networks

    Get PDF
    Being infrastructure-less and without central administration control, wireless ad-hoc networking is playing a more and more important role in extending the coverage of traditional wireless infrastructure (cellular networks, wireless LAN, etc). This book includes state-of-the-art techniques and solutions for wireless ad-hoc networks. It focuses on the following topics in ad-hoc networks: quality-of-service and video communication, routing protocol and cross-layer design. A few interesting problems about security and delay-tolerant networks are also discussed. This book is targeted to provide network engineers and researchers with design guidelines for large scale wireless ad hoc networks

    Collaborative Data Access and Sharing in Mobile Distributed Systems

    Get PDF
    The multifaceted utilization of mobile computing devices, including smart phones, PDAs, tablet computers with increasing functionalities and the advances in wireless technologies, has fueled the utilization of collaborative computing (peer-to-peer) technique in mobile environment. Mobile collaborative computing, known as mobile peer-to-peer (MP2P), can provide an economic way of data access among users of diversified applications in our daily life (exchanging traffic condition in a busy high way, sharing price-sensitive financial information, getting the most-recent news), in national security (exchanging information and collaborating to uproot a terror network, communicating in a hostile battle field) and in natural catastrophe (seamless rescue operation in a collapsed and disaster torn area). Nonetheless, data/content dissemination among the mobile devices is the fundamental building block for all the applications in this paradigm. The objective of this research is to propose a data dissemination scheme for mobile distributed systems using an MP2P technique, which maximizes the number of required objects distributed among users and minimizes to object acquisition time. In specific, we introduce a new paradigm of information dissemination in MP2P networks. To accommodate mobility and bandwidth constraints, objects are segmented into smaller pieces for efficient information exchange. Since it is difficult for a node to know the content of every other node in the network, we propose a novel Spatial-Popularity based Information Diffusion (SPID) scheme that determines urgency of contents based on the spatial demand of mobile users and disseminates content accordingly. The segmentation policy and the dissemination scheme can reduce content acquisition time for each node. Further, to facilitate efficient scheduling of information transmission from every node in the wireless mobile networks, we modify and apply the distributed maximal independent set (MIS) algorithm. We also consider neighbor overlap for closely located mobile stations to reduce duplicate transmission to common neighbors. Different parameters in the system such as node density, scheduling among neighboring nodes, mobility pattern, and node speed have a tremendous impact on data diffusion in an MP2P environment. We have developed analytical models for our proposed scheme for object diffusion time/delay in a wireless mobile network to apprehend the interrelationship among these different parameters. In specific, we present the analytical model of object propagation in mobile networks as a function of node densities, radio range, and node speed. In the analysis, we calculate the probabilities of transmitting a single object from one node to multiple nodes using the epidemic model of spread of disease. We also incorporate the impact of node mobility, radio range, and node density in the networks into the analysis. Utilizing these transition probabilities, we construct an analytical model based on the Markov process to estimate the expected delay for diffusing an object to the entire network both for single object and multiple object scenarios. We then calculate the transmission probabilities of multiple objects among the nodes in wireless mobile networks considering network dynamics. Through extensive simulations, we demonstrate that the proposed scheme is efficient for data diffusion in mobile networks

    DISTRIBUTED INTELLIGENT SPECTRUM MANAGEMENT IN COGNITIVE RADIO AD HOC NETWORKS

    Get PDF
    The rapid growth of the number of wireless devices has brought an exponential increase in the demand of the radio spectrum. However, according to the Federal Communications Commission (FCC), almost all the radio spectrum for wireless com- munications has already been allocated. In addition, according to FCC, up to 85% of the allocated spectrum is underutilized due to the current fixed spectrum alloca- tion policy. To alleviate the spectrum scarcity problem, FCC has suggested a new paradigm for dynamically accessing the allocated spectrum. Cognitive radio (CR) technology has emerged as a promising solution to realize dynamic spectrum access (DSA). With the capability of sensing the frequency bands in a time and location- varying spectrum environment and adjusting the operating parameters based on the sensing outcome, CR technology allows an unlicensed user to exploit the licensed channels which are not used by licensed users in an opportunistic manner. In this dissertation, distributed intelligent spectrum management in CR ad hoc networks is explored. In particular, four spectrum management issues in CR ad hoc networks are investigated: 1) distributed broadcasting in CR ad hoc networks; 2) distributed optimal HELLO message exchange in CR ad hoc networks; 3) distributed protocol to defend a particular network security attack in CR ad hoc networks; and 4) distributed spectrum handoff protocol in CR ad hoc networks. The research in this dissertation has fundamental impact on CR ad hoc network establishment, net- work functionality, network security, and network performance. In addition, many of the unique challenges of distributed intelligent spectrum management in CR ad hoc networks are addressed for the first time in this dissertation. These challenges are extremely difficult to solve due to the dynamic spectrum environment and they have significant effects on network functionality and performance. This dissertation is essential for establishing a CR ad hoc network and realizing networking protocols for seamless communications in CR ad hoc networks. Furthermore, this dissertation provides critical theoretical insights for future designs in CR ad hoc networks

    Proceedings of the Third Edition of the Annual Conference on Wireless On-demand Network Systems and Services (WONS 2006)

    Get PDF
    Ce fichier regroupe en un seul documents l'ensemble des articles accéptés pour la conférences WONS2006/http://citi.insa-lyon.fr/wons2006/index.htmlThis year, 56 papers were submitted. From the Open Call submissions we accepted 16 papers as full papers (up to 12 pages) and 8 papers as short papers (up to 6 pages). All the accepted papers will be presented orally in the Workshop sessions. More precisely, the selected papers have been organized in 7 session: Channel access and scheduling, Energy-aware Protocols, QoS in Mobile Ad-Hoc networks, Multihop Performance Issues, Wireless Internet, Applications and finally Security Issues. The papers (and authors) come from all parts of the world, confirming the international stature of this Workshop. The majority of the contributions are from Europe (France, Germany, Greece, Italy, Netherlands, Norway, Switzerland, UK). However, a significant number is from Australia, Brazil, Canada, Iran, Korea and USA. The proceedings also include two invited papers. We take this opportunity to thank all the authors who submitted their papers to WONS 2006. You helped make this event again a success

    Protocolo adaptativo de disseminação de dados para aplicações de segurança no trânsito em rodovias

    Get PDF
    Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia de Automação e Sistemas, Florianópolis, 2013.As VANETs (Vehicular Ad hoc Networks) são formadas por sistemas de comunicação entre veículos que fazem parte de um ambiente de trânsito e têm seus nós compostos por veículos e por equipamentos fixos que estão presentes ao longo das vias. Estas redes objetivam proporcionar conforto e segurança aos passageiros, por meio de informações sobre acidentes na pista, condição da estrada e aplicações de entretenimento. A disponibilidade e o tempo em que as mensagens trafegam nesta rede são essenciais para tais aplicações. Por isso, as VANETs requerem métodos eficientes e confiáveis para a comunicação de dados. Para prover confiabilidade à difusão de dados em redes veiculares deve-se transpassar alguns problemas como, por exemplo, broadcast storm, nós ocultos, alta colisões de pacotes, redundância de informação, entre outros. Muitos destes problemas persistem em estudos realizados anteriormente. Este trabalho tem por objetivo prover confiabilidade na disseminação de mensagens em aplicações voltadas a segurança no trânsito por meio de um protocolo adaptativo e eficiente. O protocolo proposto é adaptativo pois adapta o período entre transmissões de mensagens de controle de acordo com a densidade da rodovia, a fim de diminuir o número de mensagens geradas na rede. Também visa ser eficiente pois diminui a quantidade de colisões frente a quantidade de pacotes gerados na rede, oferece menor atraso no envio das mensagens e diminui a quantidade de retransmissões em cenários com mais de um alerta na rede. O trabalho envolveu (I) a definição do protocolo proposto, a integração e o uso deste pela aplicação, (II) a implementação de uma aplicação para rodovias com simuladores de redes e de tráfego bidirecionalmente acoplados, (III) avaliação da confiabilidade do protocolo proposto e dos impactos decorrentes do uso do protocolo na aplicação de disseminação de alertas por meio de simulações realizadas em diferentes cenários de densidade de veículos, e (IV) as análises dos resultados experimentais obtidos. Os resultados dos experimentos comprovam que o protocolo proposto, para os cenários simulados é 100 % confiável e que os impactos decorrentes do seu uso não prejudicam as funcionalidades da aplicação, comprovando a eficiência do protocolo.Abstract : The VANETs (Vehicular Ad hoc Networks) are formed by communication systems among vehicles which are part of the same traffic environment. Their nodes are composed of vehicles and fixed equipment present along the traffic ways. The aim of these networks is to provide comfort and safety to passengers through information about accidents on the road, road conditions and entertainment applications. The availability and the time span in which these messages move through the network are essential for these applications. Consequently, the VANETs require eficient and reliable methods for data communication. To ensure that data transmission in vehicular networks is reliable certain problems must be overcome, such as broadcast storm, hidden nodes, high collision of packages, information redundancy, among others. Many of these problems persist in previous studies. Thus, this work aims at providing, through an adaptive and eficient protocol, reliability to message transmission in applications targeted at traffic safety. The proposed protocol is adaptive as it adapts the time span between the transmissions of messages according to the road density, in order to decrease the number of messages generated in the network. It also aims at efficiency as it decreases the amount of collisions due to the number of packages generated in the network, presents less delay in message transmission and decreases the amount of retransmissions in scenarios with more than one alert in the network. This research involved (I) the definition of the proposed protocol, its integration and use by the application, (II) the implementation of an application for motorways with network and traffic simulators directionally attached, (III) evaluation of the reliability of the proposed protocol and of the impacts resulting from the use of the protocol in the application of spread of alerts through simulations carried out in diverse scenarios of vehicle density, (IV) the analyses of the experimental results. These results prove that the proposed protocol is 100 % reliable for simulated scenarios and that the impacts produced by its use do not harm the functionalities of the application, proving the eficiency of the protocol

    Enabling Censorship Tolerant Networking

    Get PDF
    Billions of people in the world live under heavy information censorship. We propose a new class of delay tolerant network (DTN), known as a censorship tolerant network (CTN), to counter the growing practice of Internet-based censorship. CTNs should provide strict guarantees on the privacy of both information shared within the network and the identities of network participants. CTN software needs to be publicly available as open source software and run on personal mobile devices with real-world computational, storage, and energy constraints. We show that these simple assumptions and system constraints have a non-obvious impact on the design and implementation of CTNs, and serve to differentiate our system design from previous work. We design data routing within a CTN using a new paradigm: one where nodes operate selfishly to maximize their own utility, make decisions based only on their own observations, and only communicate with nodes they trust. We introduce the Laissez-faire framework, an incentivized approach to CTN routing. Laissez-faire does not mandate any specific routing protocol, but requires that each node implement tit-for-tat by keeping track of the data exchanged with other trusted nodes. We propose several strategies for valuing and retrieving content within a CTN. We build a prototype BlackBerry implementation and conduct both controlled lab and field trials, and show how each strategy adapts to different network conditions. We further demonstrate that, unlike existing approaches to routing, Laissez-faire prevents free-riding. We build an efficient and reliable data transport protocol on top of the Short Message Service (SMS) to serve a control channel for the CTN. We conduct a series of experiments to characterise SMS behaviour under bursty, unconventional workloads. This study examines how variables such as the transmission order, delay between transmissions, the network interface used, and the time-of-day affect the service. We present the design and implementation of our transport protocol. We show that by adapting to the unique channel conditions of SMS we can reduce message overheads by as much as 50\% and increase data throughput by as much as 545% over the approach used by existing applications. A CTN's dependency on opportunistic communication imposes a significant burden on smartphone energy resources. We conduct a large-scale user study to measure the energy consumption characteristics of 20100 smartphone users. Our dataset is two orders of magnitude larger than any previous work. We use this dataset to build the Energy Emulation Toolkit (EET) that allows developers to evaluate the energy consumption requirements of their applications against real users' energy traces. The EET computes the successful execution rate of energy-intensive applications across all users, specific devices, and specific smartphone user-types. We also consider active adaptation to energy constraints. By classifying smartphone users based on their charging characteristics we demonstrate that energy level can be predicted within 72% accuracy a full day in advance, and through an Energy Management Oracle energy intensive applications, such as CTNs, can adapt their execution to maintain the operation of the host device
    corecore