H.C. Leligou

Technological Educational Institute of Chalkida , Khalkís, Central Greece, Greece

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Publications (43)18.36 Total impact

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    ABSTRACT: During the last decades Intelligent Transportation Systems ITS have been attracting the interest of an increasing number of researchers, engineers and entrepreneurs, as well as citizens and civil authorities, since they can contribute towards improving road transport safety and efficiency and ameliorate environmental conditions and life quality. Emerging technologies yield miniaturized sensing, processing and communication devices that enable a high degree of integration and open the way for a large number of smart applications that can exploit automated fusion of information and enable efficient decisions by collecting, processing and communicating a large number of data in real-time. The cornerstone of these applications is the realization of an opportunistic wireless communication system between vehicles as well as between vehicles and infrastructure over which the right piece of information reaches the right location on time. In this paper, the authors present the design and implementation of representative safety and traffic management applications. Specifically the authors discuss the hardware and software requirements presenting a use case based on the NEC Linkbird-MX platform, which supports IEEE 802.11p based communications. The authors show how the functionality of IEEE 802.11p can be exploited to build efficient road safety and traffic management applications over mobile opportunistic systems and discuss practical implementation issues.
    International Journal of Wireless Networks and Broadband Technologies. 01/2014; 3(1):1-17.
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    ABSTRACT: The networking of sensing devices has fuelled the development of a great variety of applications which lead to the wide deployment of Wireless Sensor Networks. Nowadays, as the sensor population becomes constantly denser, the exploitation of the vastly installed WSN infrastructure to feed with data additional applications is pursued. The research community currently designs architectures and protocol that virtualise the service and resources of the available sensors, which can belong to different administrative domains and can be of different technologies. The aim is to allow different applications to use/share the same WSN infrastructure, improving efficiency. In this paper, we review the virtualization attempts witnessed so far and we discuss how virtualisation assists the development of novel smart applications targeting an enhanced user experience.
    WSEAS 17th International Conference on Communications (part of CSCC ’13), Rhodes, Greece; 07/2013
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    ABSTRACT: Free space optical (FSO) communications links is a promising solution for the provision of high data rate point to point communications. The FSO links due to their huge bandwidth and license free spectrum provide a viable communication solution between Unmanned Aerial Vehicles (UAVs) and fixed Ground Stations (GS). It is of great importance to characterize the quality of the optical channel with a proper model, taking into consideration the interesting challenges of the mobility and the slanted path of the optical beam in order to design a high performance communication link. In this paper we investigate the performance of a mobile link between a fixed GS and an UAV in terms of Bit Error Rate (BER) and average Signal to Noise Ratio (SNR). It deals with modelling the influence of the scintillation index and the received optical power with noise on link performance, separating the slanted path into small intervals assuming a Gaussian-beam wave. An extensive comparative analysis among different FSO configurations links considering the altitude of the UAV, the wavelength and the atmospheric conditions is provided. The results show that there is degradation at the BER over a slanted path compared to a horizontal path at the same conditions.
    Transparent Optical Networks (ICTON), 2013 15th International Conference on; 01/2013
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    ABSTRACT: In this paper, we evaluate the performance gains of a novel hybrid 2-stage TDM/WDM PON access network over state-of-the-art Long-Reach WDM PONs. The proposed network architecture exploits very low cost end-user ONUs and achieves energy efficiency, reduced complexity and high-level scalability. The scheme allows a group of users to share an ultra-wide band long reach WDM-PON, in a fiber to the cabinet configuration, leading to core node consolidation and access-core integration. We quantify the benefits evaluating its application in large metropolitan area configurations using network planning techniques to reduce the number of nodes that are required to serve the expected capacity demand.
    Transparent Optical Networks (ICTON), 2013 15th International Conference on; 01/2013
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    ABSTRACT: Recently, Routing Protocol for Low Power and Lossy Networks (RPL) has been proposed by IETF ROLL WG in order to cope with Low Power and Lossy Networks (LLN) requirements implied by different application domains. In this paper, we present RPL modeling in J-Sim simulation environment, providing a complete simulation framework for performance evaluation as well as experimentation on open issues, such as the support of multiple instances and the definition of routing strategies based on the composition of several metrics.
    Networked Sensing Systems (INSS), 2012 Ninth International Conference on; 01/2012
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    ABSTRACT: The continuous evolution in mobile access technologies supporting faster data rates lead to dramatic increases of OPEX backhaul costs. It seems inevitable that the edge of the telecom network will be based on a combination of a wireless part, but also fiber for adequate capacity which is not possible with the wireless infrastructure alone. In this light, PONs offer the significant advantage of cost-effective port and traffic consolidation particularly in their TDM variant. Recently advanced PON technologies based on WDM have appeared. The additional feature of WDM-PONs is their increased flexibility in dynamic resource allocation. In this paper we review different architectures that have been proposed in the literature allowing for dynamic resource allocation via the configuration of Virtual PONs. A virtual PON (VPON) can be created for (potentially dynamically formed) subscriber groups using multiple waves on a single fiber potentially increasing utilization and scalability leading to a converged network architecture.
    Telecommunications and Multimedia (TEMU), 2012 International Conference on; 01/2012
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    ABSTRACT: Wireless sensor networks offer inexpensive solutions in a wide variety of applications ranging from health, home, roads and public area monitoring to industry and aircraft control. As sensors proliferate, scalable communication protocols with low implementation requirements are pursued. Another key issue for the wider deployment of these solutions is security since the wireless sensor networks themselves are prone to security attacks. In this paper, we review geographical routing protocols, which allow for high scalability due to their localised operation while they also support mobility consuming less node and network resources since they operate on very limited overhead. We also investigate their vulnerabilities to security attacks (Sybil and selective forwarding attacks) and report efficient coutermeasures.
    Telecommunications and Multimedia (TEMU), 2012 International Conference on; 01/2012
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    ABSTRACT: The diversity of applications that current and emerging Wireless Sensor Networks (WSNs) are called to support imposes different requirements on the underlying network with respect to delay and loss, while at the same time the WSN imposes its own intricacies. The satisfaction of these requirements highly depends on the metric upon which the forwarding routes are decided. In this view, the IETF ROLL group has proposed the RPL routing protocol, which can flexibly work on various routing metrics, as long as they hold specific properties. The system implementer/user is free to decide whether to use one or multiple routing metrics, as well as the way these metrics can be combined. In this paper, we provide ways to quantify the routing metrics so that they can be combined in an additive or lexical manner. We use extensive simulation results to evaluate the impact of several routing metrics on the achieved performance.
    Telecommunications and Multimedia (TEMU), 2012 International Conference on; 01/2012
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    ABSTRACT: As the applications of Wireless Sensor Networks proliferate, security issues raised in this uncontrolled, self- organised systems comprising a large number of nodes with very low processing, buffering and communication capabilities become mandatory as they need to cooperate with each other, even for routing data messages to the desired destination. A solution that has been widely pursued to detect and avoid nodes that perform denial of service (refuse their forwarding services) is trust management, i.e. each node monitors the forwarding behavior of its neighbours in order to detect any node that behaves selfishly and does not forward the packets it receives. To accelerate trust knowledge gathering, nodes exchange their opinions about their common neighbours. This exchange is beneficial mainly in the case of node mobility. The more often this information is exchanged, the faster the trust information is built. However, as the transmission of this information consumes energy (which is a scarce resource in these settings), there is an interplay between the trust building speed and the energy consumption. This interplay is at the focus of the current paper, which investigates the performance of WSNs using computer simulations.
    01/2011;
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    ABSTRACT: As the applications of wireless sensor networks proliferate, the efficiency in supporting large sensor networks and offering security guarantees becomes an important requirement in the design of the relevant networking protocols. Geographical routing has been proven to efficiently cope with large network dimensions while trust management schemes have been shown to assist in defending against routing attacks. Once trust information is available for all network nodes, the routing decisions can take it into account, i.e. routing can be based on both location and trust attributes. In this paper, we investigate different ways to incorporate trust in location-based routing schemes and we propose a novel way of balancing trust and location information. Computer simulations show that the proposed routing rule exhibits excellent performance in terms of delivery ratio, latency time and path optimality.
    Wireless Communications and Mobile Computing 01/2010; · 0.86 Impact Factor
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    ABSTRACT: Security is currently a weak point of wireless sensor networks (WSN) impeding their proliferation although they offer flexible and low cost solutions for many every-day life applications. In WNSs, routing of data from the sensor nodes towards the destination/base station relies on the cooperation among neighbouring nodes. The realization of a trust management system which allows each node to define a trust value for each neighbour has been proposed as a powerful tool towards defending against the routing attacks. In this paper, we investigate how the trust information can be incorporated in the routing protocol and we compare based on simulation results three different trust-aware geographical routing algorithms.
    ELMAR2009, Zadar Croatia; 09/2009
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    ABSTRACT: It is increasingly recognized that the Internet is transforming into a platform providing services beyond todaypsilas expectations. To successfully realize this transformation, the structural limitations of current networking architectures must be raised so that information transport infrastructure gracefully evolves to address transparent core-access integration, optical flow/packet transport, and end-to-end service delivery capability, overcoming the limitations of segmentation between access, metro, and core networks and domains. We propose and evaluate an integrated control plane for optical access and core networks, which addresses the above consideration. The proposed control plane can lead to a unified transport infrastructure integrating state-of-the-art components and technologies including wavelength division multiplexing, passive optical networking, and optical packet routers with inherent traffic grooming capabilities. The performance of the proposed architecture is assessed by means of simulation in terms of cost, resource utilization, and delay.
    Journal of Optical Communications and Networking 08/2009; · 1.43 Impact Factor
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    ABSTRACT: As Wireless Sensor Network-based solutions are proliferating they are facing new challenges: they must be capable of adapting to rapidly changing environments and requirements while their nodes should have low power consumption as they usually run on batteries. Moreover, the security aspect is crucial since they frequently transmit and process very sensitive data, while it is important to be able to support real-time video or processed images over their limited bandwidth links. SMART targets to design and implement a highly reconfigurable Wireless Visual Sensor Node (WVSN) defined as a miniaturized, light-weight, secure, low-cost, battery powered sensing device, enriched with video and data compression capabilities.
    Sensor, Mesh and Ad Hoc Communications and Networks Workshops, 2009. SECON Workshops '09. 6th Annual IEEE Communications Society Conference on; 07/2009
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    ABSTRACT: A lot of effort has been spent in securing the routing procedure in wireless sensor network (WSNs) since this is accomplished in a cooperative way and is vital for the communication of the sensors with the base station which collects the sensed data. The communication over wireless links in combination with the ad hoc organization introduces vulnerabilities. Each node monitors the behaviour of its neighbours in order to check whether they behave maliciously or not. Nodes with low trustworthiness are then avoided during routing decisions which are based on location and trust information. The efficiency of the proposed approach in defending against black-hole, grey-hole and integrity attacks is evaluated using computer simulations.
    Systems, Signals and Image Processing, 2009. IWSSIP 2009. 16th International Conference on; 07/2009
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    ABSTRACT: The evolution towards packet-based access networks and the importance of quality of experience brings the need for access networks that support the offer of a wide range of multimedia services not currently available to the desired extent. Legacy networks based on circuit switching used explicit signalling that travelled to all nodes along the path to book resources before the launce of the media stream. This approach does not scale well and is not in line with the philosophy of packet networks. Still, the need to reserve resources in advance remains since real-time services have limited if any means of adjusting their rates to the prevailing network conditions and to preserve customer satisfaction the traditional preventive approach that needs accurate estimates of resource needs for the duration of the session is the only option. The paper describes a possible CAC solution based on measuring flows and enriches the network with implicit admission control (without obviating explicit control if available) and can manage resource allocation to protect quality-demanding services from degradation. The basis is a flow measurement system, which will estimate the traffic load produced by the flow and activate admission control. However, because in most cases these initial indication may well be misleading, it will be cross checked against a database of previously recorded flows per customer interface which can provide long term data on the flows leaving only a few cases that have to be corrected on the fly. The overall product is a self-learning autonomic system that supports QoS in the access network for services that do not communicate with the network layer such as, for example, peer-to-peer real-time multimedia applications.
    11/2008;
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    ABSTRACT: The range of applications of wireless sensor networks is so wide that it tends to invade our every-day life. In the future, a sensor network will surveil our health, our home, the roads we follow, the office or the industry we work in, or even the aircrafts we use, in an attempt to enhance our safety. However, the wireless sensor networks themselves are prone to security attacks. The list of security attack is already very long and will impede the deployment of these solutions, if not efficiently addressed. In this paper, we focus on the security threats against routing, which is a basic networking service, required for any sensor network communication. Preventing the integrity and data freshness of the exchanged packets is a requirement but is not enough to secure the routing procedure. It is required to set-up a trust management scheme which allows the nodes to select trusted paths rather than secure routes in the network by observing the sincerity in participation by other nodes. A trust management system can be useful for detecting a node which is not behaving as expected (either faulty or maliciously). Current trends in trusted routing for ad-hoc networks are reviewed, followed by comments on their applicability in sensor network and guidelines for trust model design for new sensor applications.
    ELMAR, 2008. 50th International Symposium; 10/2008
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    ABSTRACT: Ad-hoc wireless sensor networks (AWSN) are quickly gaining popularity due to the fact that they are potentially low-cost solutions that can be used in a variety of application areas including emergency response, medical monitoring, homeland security and environmental monitoring. On the other hand, AWSN introduce severe node resource constraints due to their lack of data storage capabilities, power limitation, low bandwidth, restricted transmission range. All these factors represent major obstacles to the implementation of traditional security techniques in AWSN. In this paper, we present AWSN security and operational requirements, sensor node constraints affecting security requirements and finally the goals of AWISSENET, an EU funded project aiming at further securing AWSN.
    ELMAR, 2008. 50th International Symposium; 10/2008
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    ABSTRACT: Wireless Sensor Networks (WSN) are quickly gaining popularity due to the fact that they are potentially low‐cost solutions that can be used in a variety of application areas including emergency response, medical monitoring, homeland security and environmental monitoring. However, due to their wireless nature, the relevant security requirements form a quite extensive list. An important subset of their security threats can be addressed implementing a trust management system, which establishes trust relationships among the network nodes. The methods for calculating trust via concatenation and multipath propagation are referred to as trust models. For a complete estimation of such a scheme not only computational complexity, but also the level of increase of the total network throughput and the impact on energy consumption must be thoroughly examined in order to evaluate its effective applicability in AWSN networks.
    AIP Conference Proceedings. 08/2008; 1048(1):420-423.
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    ABSTRACT: The primary requirements of a successful wireless sensor network security architecture are confidentiality, integrity and authentication. Most of these security objectives can be addressed using appropriate hash functions and cryptography schemes. By applying these mechanisms, the energy consumption increases, shortening the sensor node lifetime. On the other hand, the selection of a highly secure encryption algorithm might lead to unacceptable computational time, taking into account the constrained processor power of the sensor nodes. This paper presents an overview of the results published in the literature regarding time and energy consumption overhead of hashing and encryption mechanisms in wireless sensor networks. The evaluation of these results helps on the selection of the appropriate algorithms, depending on the application.
    Systems, Signals and Image Processing, 2008. IWSSIP 2008. 15th International Conference on; 07/2008
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    ABSTRACT: Todaypsilas core networks deploy wavelength division multiplexing (WDM) to offer high capacity of the order of 1 Tb/sec and long reach transmission of the order of 1000 km. In such systems, the information is transmitted optically on different wavelengths but it is transferred across the network through fibre links that are terminated by SONET/SDH equipment. In such networks, layer crossing is inevitable, requiring deep data inspection and complex protocol processing, resulting in limited scalability and high installation, operation and maintenance cost. It is however the only reliable end-to-end service delivery scenario available today that utilises the optical bandwidth and guarantees provisioning of resources. In this paper we review the alternative concept of CANON (clustered architecture for nodes in optical networks), a scenario that utilises clustering of nodes in ring topologies to create a hierarchy in transporting traffic in a dynamic, future proof and scalable manner. Here we emphasize on the optical crossconnect architectures that can serve such a network scenario.
    Transparent Optical Networks, 2008. ICTON 2008. 10th Anniversary International Conference on; 07/2008