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Ad Hoc Networking Workshop (Med-Hoc-Net), 2011 The 10th IFIP Annual Mediterranean

Date 12-15 June 2011

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Displaying Results 1 - 25 of 32
  • Index

    Page(s): i
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    Freely Available from IEEE
  • Program

    Page(s): ii - vii
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  • Committees

    Page(s): viii
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  • Fast randomized algorithm for hierarchical clustering in Vehicular Ad-Hoc Networks

    Page(s): 1 - 8
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (674 KB) |  | HTML iconHTML  

    Vehicular Ad-Hoc Networks (VANETs) offer communication between vehicles and infrastructure. Warning messages, among others, can be used to alert drivers, and thus improve road safety. To adapt to the unique nature of VANETs, which demands the delivery of time sensitive messages to nearby vehicles, fast topology control and scheduling algorithms are required. A clustering approach, which was initially offered for Mobile Ad-Hoc Networks (MANETs), can be adapted to VANETs to solve this problem. In this paper we present Hierarchical Clustering Algorithm (HCA), a fast randomized clustering and scheduling algorithm. HCA creates hierarchical clusters with a diameter of at most four hops. Additionally, the algorithm handles channel access and schedules transmissions within the cluster to ensure reliable communication. Unlike other clustering algorithms for VANETs, HCA does not rely on localization systems which contributes to its robustness. The running time of the algorithm was analyzed analytically and HCA was evaluated by simulation. We compared our algorithm with 2-ConID, a clustering algorithm for MANETs, under several mobility scenarios. The simulation results confirm that the algorithm behaves well under realistic vehicle mobility patterns and outperforms 2-ConID in terms of cluster stability. View full abstract»

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  • Performance of Dynamic-Frame-Aloha protocols: Closing the gap with tree protocols

    Page(s): 9 - 16
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (339 KB) |  | HTML iconHTML  

    The Dynamic-Frame-Aloha protocol, largely studied in the 60s in the field of random access satellite systems, is nowadays commonly applied also to Radio Frequency Identification systems to orchestrate the transmissions from the tags to the reader. In a nutshell, tags respond to reader's interrogation in slots randomly chosen in a frame whose size is dynamically set by the reader according to the current backlog (remaining tags to be resolved). In this paper, we explore the performance of the DFA protocol under Poisson-distributed population of tags when different strategies are adopted in setting the frame length and estimating the traffic backlog. We further analytically characterize the best strategy in the two cases where the frame is entirely explored or a new frame can be restarted at any slot. View full abstract»

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  • A centralized inter-network resource sharing (CIRS) scheme in IEEE 802.22 cognitive networks

    Page(s): 17 - 24
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1043 KB) |  | HTML iconHTML  

    IEEE 802.22 is a standard for Wireless Regional Area Network (WRAN) based on cognitive radio techniques. It allows sharing of geographically unused spectrum allocated to the Television Broadcast Service, without causing harmful interference to the licensed users. An open issue in cognitive 802.22 networks is represented by the resource distribution among WRANs. The contribution of this paper is a resource sharing algorithm which assigns resources to overlapped WRANs in such a way to avoid harmful interference among them. Specifically, we propose a collision free resource sharing method which, working in a multichannel environment, aims to assign band to the coexisting WRANs, satisfying their spectrum demand and determining a fair spectrum scheduling. The novel method adapts to the continuous changes of the spectrum availability due to necessity of vacating a channel in case of the incumbent primary users or otherwise due to the addition of unused band. Moreover, the introduced allocation scheme takes into account the issue of spatial diversity, i.e. the case where some channels do not spatially cover all the WRANs. The effectiveness of the proposed multichannel resource sharing scheme is proved through simulations, and the results, compared with other methods already known in literature, show that the algorithm makes a resource assignment which satisfies the requests and improve the use of the available channels, increasing the spectral efficiency. View full abstract»

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  • Delay performance of a Publish Subscribe system deployed over a memory-constrained, Delay Tolerant Network

    Page(s): 25 - 32
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (797 KB) |  | HTML iconHTML  

    In this work we assess the delay performance of a Publish Subscribe system built on top of a Delay Tolerant Network (DTN) composed of nodes with limited storage capacities. Many DTN routing protocols replicate the same data over several nodes, in order to deliver data to destination in a faster or in a more reliable way. Of course, increasing the number of replicas has the effect of decreasing the delivery delay perceived by the users, but increases the use of the system memory. Our goal is to investigate the trade-off between reduction of delay and storage requirements when nodes are memory constrained, in a Topic-based, Publish Subscribe system where we have different topics with different popularity. We provide some insights in this trade-off, which implies some unanticipated issues, and propose simple rules to dimension the number of replicas per topic. To this end, we derive analytical models and we validate them with simulations. View full abstract»

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  • DTFR: A geographic routing protocol for wireless Delay Tolerant Networks

    Page(s): 33 - 40
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (516 KB) |  | HTML iconHTML  

    We introduce the Delay Tolerant Firework Routing (DTFR) protocol, a protocol designed for routing in wireless Delay Tolerant Networks (DTNs) that consist of very large numbers of highly mobile nodes. Under DTFR, each packet initially travels, using high priority transmissions, to a target region in the network where the destination is expected to be. Once there, the packet is replicated to a number of copies that spread across the target region, in search of the destination. As soon as a copy finds a known route to the destination, it follows it and gets delivered. To evaluate DTFR's performance, we have developed a simulation tool that can handle networks with numbers of nodes on the order of 104. The simulation is optimized for use in DTNs and is very detailed, taking into account, among other things, the Media Access sublayer and the contents of buffers. Our protocol is compared against (i) Spray and Wait, (ii) GeoCross, (in) GeoDTN+Nav, (iv) a simple flooding protocol (chosen as one extreme of the design space), and (v) Bethlehem Routing (BR), an idealistic protocol that upper bounds the performance of a wide class of protocols. For a wide range of parameters, our protocol is superior (in terms of packet delay and aggregate throughput) to Spray and Wait, GeoCross, GeoDTN+Nav, and the flooding protocol, and performs close to the Bethlehem upper bound. View full abstract»

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  • Green wireless networking: Three questions

    Page(s): 41 - 44
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (225 KB) |  | HTML iconHTML  

    In this short note we briefly discuss three issues related to the relevance and the possible impact of research in the field of green networking, with special attention to the wireless case, since this is the context where energy efficiency is needed most. View full abstract»

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  • A power management algorithm for green femtocell networks

    Page(s): 45 - 49
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (469 KB) |  | HTML iconHTML  

    The femtocell concept is an emerging technology for deploying the next generation of the wireless networks, aiming at increasing capacity and offloading the overlay macrocell traffic. Energy costs account for as much as half of a mobile operator's operating expenses. Thus, finding radio networking solutions that can greatly improve energy-efficiency as well as resource-efficiency (Green Communications) is not only benefit for the global environment but also makes commercial sense for telecommunication operators supporting sustainable and profitable business. In this paper, we propose a green and distributed algorithm to dynamically optimize the coverage of a femtocell group by adjusting their transmitting power in an Administrative Domain. The resulting evolved algorithm shows the ability to optimize the coverage well, and consequently the resultant substantial energy consumption. View full abstract»

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  • Secured Bilateral Rendezvous using self interference cancellation in wireless networks

    Page(s): 50 - 57
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (468 KB) |  | HTML iconHTML  

    Secure transmission among mobile nodes in hostile environments has often been achieved by trading off security with communication latency. However, in time critical applications (e.g., tactical wireless networks, civilian law enforcement operations, homeland security missions, etc.), latency is more critical than any other parameters. Long latency is generally attributed to the time required by authentication in the presence of eavesdroppers and jammers. To address the latency issue, this paper proposes a Secured Bilateral Rendezvous (SBR) protocol that reduces the communication latency while guaranteeing protection. SBR performs neighbor detection before authentication. During detection, nodes exchange a common secret key in plaintext that helps speed up the authentication process. The plaintext message is protected against jammers by allowing nodes to transmit simultaneously and to recover the partner's packets using self interference cancellation technique. Simulation results show that the proposed SBR protocol can effectively withstand various jamming attacks. View full abstract»

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  • Facing man-in-the-middle and route diversion attacks in energy-limited RFID systems based on mobile readers

    Page(s): 58 - 64
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (552 KB) |  | HTML iconHTML  

    Focus of this paper is a large RFID system, where mobile readers detect the presence of RFID tags in the surrounding and, periodically, report the outcome of such operation to a control center interested in localizing all RFID tags. In order to deliver the above reports to the control center, mobile readers establish a mobile ad hoc network. In this context, a possible objective of an attacker may be to make the system believe that the position of a certain RFID tag is different from the actual one. To achieve this, the attacker performs man-in-the-middle and routing diversion attacks. Solutions can be devised for combating such attacks but they involve increased energy consumption. In this paper the problem is stated and the tradeoff between security and energy efficiency discussed. Furthermore, some preliminary results are shown and analyzed. View full abstract»

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  • An efficient distributed privacy-preserving recommendation system

    Page(s): 65 - 70
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (394 KB) |  | HTML iconHTML  

    Implementing a recommendation system on the data of mobile social networks exploits knowledge about behavior and preferences of its users and hence raises serious privacy concerns. Leveraging the wealth of aggregated information in these services promises an immense benefit by allowing suggestions for presumably appreciated, yet previously unseen restaurants, sights, and further types of locations. Privacy preserving recommenders based on homomorphic encryption have been proposed, which have a systematic draw-back: while recommender systems often store their information as real values, all homomorphic encryption schemes used today process only data from other algebraic structures, e.g., the ring of integers modulo some integer n. Therefore, we present a novel distributed recommender and a homomorphic encryption scheme, which works directly on real numbers and which possesses some remarkable properties: it is conceptually simple, efficient, and provably secure. View full abstract»

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  • Secure neighbor position discovery in vehicular networks

    Page(s): 71 - 78
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (583 KB) |  | HTML iconHTML  

    In vehicular ad hoc networks, knowledge of neighbor positions is a requirement in a number of important tasks. However, distributed techniques to perform secure neighbor position discovery, suitable for highly mobile ad hoc environments, are missing. In this paper, we address this need by proposing a lightweight distributed protocol that relies only on information exchange among neighbors, without any need of a-priori trustworthy nodes. We present a detailed security analysis of our protocol in presence of one or multiple adversaries, and we evaluate its performance in a realistic vehicular environment. View full abstract»

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  • Simulative performance evaluation of the simTD Self Organizing Traffic Information System

    Page(s): 79 - 86
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2812 KB) |  | HTML iconHTML  

    The simTD (Safe and Intelligent Mobility: Test Field Germany) research project is another step towards bringing Car-to-X technology to marketability. One of its envisioned applications is a Traffic Information System (TIS) based on self-generated maps for vehicles not equipped with digital maps. To assure reliable operation, the function itself, its performance and the effect of its input parameters was simulatively evaluated before it was validated on real vehicles. In this paper we demonstrate how to adequately parameterize and evaluate such a TIS. We find feasible values for the input parameters for the creation of self-generated maps to ensure solid operation of the function. We further contribute to the community and other projects using similar TIS deployments by introducing applicable metrics for TIS evaluation in general and show our findings for the simTD research project. View full abstract»

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  • A comparison of vehicular trajectory encoding techniques

    Page(s): 87 - 94
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (596 KB) |  | HTML iconHTML  

    The transmission of vehicular trajectory information is one basic building block of car-to-car communication. Frequently, this information is transmitted as raw data, i. e., as a sequence of location measurements. In this paper we argue that, due to the laws of physics and the requirement to follow a road, vehicular mobility has very specific characteristics. Hence, vehicular trajectory information can be compressed very efficiently using domain-specific lossy compression schemes. We discuss and compare three promising approaches that can be used to this end: linear approximation, cubic splines, and clothoids. View full abstract»

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  • VANET mobility modeling challenged by feedback loops

    Page(s): 95 - 102
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (402 KB) |  | HTML iconHTML  

    VANET applications are often providing street traffic information to vehicles and drivers, regarding, for instance, traffic conditions and parking space availability. This information influences in turn the driving behavior in real-world settings. Mobility models used in current VANET simulations are mostly ignoring this feedback entirely. In cases the feedback is included, it is mainly based on ad-hoc approaches with lack of generality. With this paper, we contribute to the investigation of such feedback loops within VANETs by describing the levels at which feedback loops can be introduced, i.e., on strategic, tactical, and operational levels of mobility. We further describe how feedback loops can be introduced in arbitrary mobility models and in particular in elementary mobility models. We exemplify our approach by introducing two types of feedback loops for the Manhattan Mobility model, the Random Trip model, and the Constrained Random Trip model. One feedback loop represents points of interest attracting vehicles, such as free parking spaces attracting vehicles searching for parking. The other feedback loop focuses on repelling vehicles, such as a traffic jam. We discuss the impacts of the feedback in terms of the mobility metrics: vehicle density per area, number of direction changes, and intensity of direction changes. Furthermore, we discuss the effects in terms of information availability and delays of transmission in an opportunistic vehicular network. View full abstract»

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  • Broadcast strategies with probabilistic delivery guarantee in multi-channel multi-interface Wireless Mesh Networks

    Page(s): 103 - 106
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (414 KB) |  | HTML iconHTML  

    Multi-channel multi-interface Wireless Mesh Networks permit to spread the load across orthogonal channels to improve network capacity. Although broadcast is vital for many layer-3 protocols, proposals for taking advantage of multiple channels mostly focus on unicast transmissions. In this paper, we propose broadcast algorithms that fit any channel and interface assignment strategy. They guarantee that a broadcast packet is delivered with a minimum probability to all neighbors. Our simulations show that the proposed algorithms efficiently limit the overhead. View full abstract»

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  • A path tracking Algorithm using the IEEE 802.11 Infrastructure

    Page(s): 107 - 110
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (397 KB) |  | HTML iconHTML  

    We propose a new indoor tracking method which can be used on mobile nodes. Our method uses only the received signal strengths as input information and does not require a cinematic motion model to track the mobile node. We discuss in detail the features of our approach and its resulting algorithm. We evaluate the performances of our algorithm using a real signal map. View full abstract»

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  • Architecture of a communication middleware for VANET applications

    Page(s): 111 - 114
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (249 KB) |  | HTML iconHTML  

    As one of the main tasks of a project for developing an Advanced Cooperative Infomobility System (ACIS), we have devised and partly implemented a communication middleware for infomobility applications on vehicular ad-hoc networks (VANETs). In this paper we illustrate and motivate some of the architectural choices underlying the ACIS middleware. View full abstract»

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  • Effects of anchor placement on mean-CRB for localization

    Page(s): 115 - 118
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (667 KB) |  | HTML iconHTML  

    In this paper we discuss the lower bound i.e. the Cramer-rao-bound (CRB) on the accuracy of localization of nodes in a wireless network. We investigate the effects of anchor (or base station) placement on optimal target node positioning. The optimal and worst anchor positions are determined through extended simulation by comparing their mean CRB. Furthermore the ramifications of an additive and multiplicative noise model on the mean CRB are explored. Finally, the least squares (LS) method for localization is used and its performance is compared with the lower bound for optimal anchor positions. View full abstract»

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  • Uisce: Characteristic-based routing in mobile ad hoc networks

    Page(s): 119 - 122
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (577 KB) |  | HTML iconHTML  

    The goal of communication in computer networks is the delivery of information to endpoints with certain properties. In wired networks, identities such as IP addresses are used to guide information through a network and the properties of network nodes are mapped to these identities by service discovery mechanisms. In mobile ad hoc networks (MANETs), identities lose their guiding ability because of the dynamism of the topology. Instead of identities, we introduce a concept called a characteristic, which describes the properties of nodes. Characteristics are disseminated throughout a network, simulating the flow of water streams. Messages are forwarded to their destinations nodes with given properties following these characteristics like following a water stream to its source. Characteristic-based routing differs from existing content-based routing in that a characteristic describes features of MANET nodes rather than contents of data messages. A trace characteristic is left by data messages along their forwarding path. Subsequent data messages can be forwarded to the same destination node and reply messages can be delivered back to the sender of data messages following the trace characteristic. We demonstrate that a characteristic-based approach increases the rate of successful delivery in comparison to existing identity based approaches in MANETs. Then we analyze the ability of trace characteristics to maintain routes for subsequent data messages in different mobility settings. View full abstract»

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  • Coloring-based resource allocations in ad-hoc wireless networks

    Page(s): 123 - 126
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (259 KB) |  | HTML iconHTML  

    It is well known that CSMA/CA protocols exhibit very poor performance in case of multi-hop transmissions, because of inter-link interference due to imperfect carrier sensing. We propose to control such an interference by preallocating temporal slots in which different sets of network nodes are allowed to contend for the channel access. The approach is based on distributed coloring algorithms with limited signaling overhead that can be customized as a function of the network topology and traffic load. View full abstract»

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  • Comparison of utility functions for routing in cognitive wireless ad-hoc networks

    Page(s): 127 - 130
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3004 KB) |  | HTML iconHTML  

    In Cognitive Radio Ad-Hoc Networks the design of suitable routing solutions is a focal issue to fully unleash the potentials of this networking paradigm. The main challenge is exploiting spectrum holes to build up network paths that remain stable and that achieve specific network performance in terms of delay and percentage of delivered data, even if an opportunistic spectrum access is implemented. In this paper we propose a utility function based on the path connectivity, re-elaborated in a cognitive radio scenario, and we compare it with other utility functions that can be used for routing data in cognitive radio. We show that by using our utility function we select paths for the secondary users transmissions leading to better performance when compared with a utility function that selects paths with the minimum activities of the primary users and an utility function that minimizes the number of hops. These results are derived in great number of topologies and with different primary users activities. View full abstract»

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  • HRAN: Heat routing protocol for Ad-Hoc Networks

    Page(s): 131 - 134
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (254 KB) |  | HTML iconHTML  

    In this paper we propose a new routing protocol for large scale Mobile Adhoc Networks, named HRAN. The protocol supports large networks, requires few resources from devices and lowers the control message overhead associated with discovering new routes. It works by simulating the paradigm of heat trails in a physical environment through the use of bloom filters. In our protocol each node emits a certain quantity of heat and as the node moves a heat trail is formed. After a node leaves a location the heat from surrounding nodes slowly dissipates. This heat information is then used to guide routing queries from the source to the destination. View full abstract»

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