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Sarigiannidis P.G.,Aristotle University of Thessaloniki | Louta M.D.,University of Western Macedonia | Chatzimisios P.,CSSN Research Laboratory
2010 International Congress on Ultra Modern Telecommunications and Control Systems and Workshops, ICUMT 2010 | Year: 2010

A novel fair mapping scheme is proposed in this paper for the IEEE 802.16 downlink sub-frame. The mapping process is critical since it allocates the users' requests into the downlink sub-frame in order to be sent to the mobile stations. One of the most noticeable issues in this area lies on the fairness aspect. Giving that the mapping process defines the order and the way that the users' requests are being serviced, some users may be treated unfairly. In this work this issue is considered and a new mapping scheme is introduced. The proposed scheme encloses fair and more efficient mapping process, compared to the leading scheme, according to the presented simulation results. ©2010 IEEE.

Lagkas T.,University of Western Macedonia | Chatzimisios P.,CSSN Research Laboratory
Eurasip Journal on Wireless Communications and Networking | Year: 2011

Cutting-edge wireless networking approaches are required to efficiently differentiate traffic and handle it according to its special characteristics. The current Medium Access Control (MAC) scheme which is expected to be sufficiently supported by well-known networking vendors comes from the IEEE 802.11e workgroup. The standardized solution is the Hybrid Coordination Function (HCF), that includes the mandatory Enhanced Distributed Channel Access (EDCA) protocol and the optional Hybrid Control Channel Access (HCCA) protocol. These two protocols greatly differ in nature and they both have significant limitations. The objective of this work is the development of a high-performance MAC scheme for wireless networks, capable of providing predictable Quality of Service (QoS) via an efficient traffic differentiation algorithm in proportion to the traffic priority and generation rate. The proposed Adaptive Weighted and Prioritized Polling (AWPP) protocol is analyzed, and its superior deterministic operation is revealed. © 2011 Thomas Lagkas and Periklis Chatzimisios.

Lagkas T.D.,University of Western Macedonia | Chatzimisios P.,CSSN Research Laboratory
IEEE International Conference on Communications | Year: 2011

IEEE 802.11e Enhanced Distributed Channel Access (EDCA) is developed to provide Wireless Local Area Networks (WLANs) with Quality of Service (QoS) support. Several solutions have been proposed in order to provide a fair channel access for all competing stations. This paper first studies the QoS capabilities of the Adaptive Weighted and Prioritized Polling (AWPP) protocol that adopts the frame structure and the basic polling scheme of the Priority Oriented Adaptive Polling (POAP) protocol. Our analytical approach is validated by plotting analytical results against simulation outcome. We then explore the fairness provision of the AWPP protocol utilizing Jain's fairness index. Finally, we provide a comparative performance analysis between EDCA, POAP and AWPP protocols and we demonstrate that AWPP outperforms the other two. © 2011 IEEE.

Sgora A.,University of Piraeus | Vergados D.D.,University of Piraeus | Chatzimisios P.,CSSN Research Laboratory
Proceedings - IEEE Symposium on Computers and Communications | Year: 2010

Ubiquitous service delivery requires the selection of the optimal access network in a heterogeneous wireless environment. However, since the selection of an access network in such an environment depends on several parameters with different relative importance (such as the network and the application characteristics, the user preferences, the service cost), it is a difficult task to be achieved. In this paper, an effective access network selection algorithm for heterogeneous wireless networks is proposed that combines two Multi Attribute Decision Making (MADM) methods, the Analytic Hierarchy Process (AHP) method and the Total Order Preference by Similarity to the Ideal Solution (TOPSIS) method. More specifically, the AHP method is used to determine weights of the criteria and the TOPSIS method is used to obtain the final access network ranking. © 2010 IEEE.

Vergados D.J.,National Technical University of Athens | Sgora A.,University of Piraeus | Vergados D.D.,University of Piraeus | Chatzimisios P.,CSSN Research Laboratory
Proceedings - IEEE Symposium on Computers and Communications | Year: 2011

Multihop networks are used in a variety of ways, that include ad-hoc networks, wireless sensor networks, and mesh networks. These networks consist of nodes that connect over a wireless channel, and communicate over multiple links by forwarding each other's messages. The throughput is determined by the contention among the nodes for the wireless resources. Thus routing algorithms, influence the level of contention at each location of the network, and play an important role in the network throughput. Additionally, the sequence of transmission opportunities of each node, which is determined by the scheduling algorithm, should also be carefully designed, since it affects the available resources of each node. In this paper we study the effect of routing and scheduling algorithms on the throughput of multihop networks. We propose a per-flow joint routing/scheduling algorithm that has the property of routing the flows in a way that avoids congested areas with limited availability, and also schedules links, in a way that a) slots are assigned to flows, instead of links or nodes, b) the assignment is fair c) fairness does not lead to underutilization. Simulation results showed that the proposed algorithm increases the average throughput, and the degree of satisfaction of each node, while at the same time it decreases the average delay. © 2011 IEEE.

Barroca N.,University of Beira Interior | Borges L.M.,University of Beira Interior | Velez F.J.,University of Beira Interior | Chatzimisios P.,CSSN Research Laboratory
2014 IEEE International Conference on Communications, ICC 2014 | Year: 2014

IEEE 802.15.4 Medium Access Control (MAC) layer does not include the Request-To-Send/Clear-To-Send (RTS/CTS) handshake mechanism, in order to overcome the hidden node problem that affects Wireless Sensor Networks (WSNs). In this paper we propose and analyse the use of RTS/CTS in IEEE 802.15.4 for the nonbeacon-enable mode. The proposed solution shows that by considering the RTS/CTS mechanism combined with packet concatenation we improve the network performance in terms of maximum throughput, minimum delay and bandwidth effciency. In IEEE 802.15.4 with RTS/CTS, the backoff procedure process is not repeated for each data packet sent unlike the basic access mode of IEEE 802.15.4, but only for each RTS/CTS set. Therefore, the channel utilization is maximized by decreasing the deferral time period before transmitting a data packet. Our work introduces an analytical model capable of accounting the retransmission delay and the maximum number of backoff stages. The successful validation of our analytical model is carried out by comparison against simulation results by using the OMNeT++ simulator. © 2014 IEEE.

Barroca N.,University of Beira Interior | Velez F.J.,University of Beira Interior | Chatzimisios P.,CSSN Research Laboratory
IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC | Year: 2013

One of the fundamental reasons for the IEEE 802.15.4 standard Medium Access Control (MAC) inefficiency is overhead. The current paper proposes and analyses the Sensor Block Acknowledgment MAC (SBACK-MAC) protocol, a new innovative protocol that allows the aggregation of several acknowledgment responses in one special BACK Response packet. Two different solutions are addressed. The first one considers the SBACK-MAC protocol in the presence of BACK Request (concatenation) while the second one considers the SBACK-MAC in the absence of BACK Request (piggyback). The proposed solutions address a distributed scenario with single-destination and single-rate frame aggregation. The throughput and delay performance is mathematically derived under ideal conditions (a channel environment with no transmission errors). The proposed schemes are compared against the basic access mode of IEEE 802.15.4 through extensive simulations by employing the OM-NET++ simulator. We demonstrate that the network performance is significantly improved in terms of throughput and end-to-end delay. © 2013 IEEE.

Androulidakis I.,University of Ioannina | Vlachos V.,Technological Educational Institute of Larissa | Chatzimisios P.,CSSN Research Laboratory
International Conference on Information and Digital Technologies, IDT 2015 | Year: 2015

Unlike confidentiality and privacy concerns, the preservation of mobile phone service availability has not received the same attention from researchers, albeit an important factor, especially in business but also in life threatening situations. In this paper we present a methodology for testing practical battery deprivation denial of service attacks in mobile phones. We focus on attacks against the mobile terminal and not against the network. A variety of scenarios is proposed encompassing stealth Short Message Service messages (SMS), as well as very short calls interrupted before the phone actually rings. Both techniques are invisible to the target under attack and force the mobile phone to continuously transmit, consuming energy up to the point of complete battery depletion. Current flow and thus power consumption can be measured using a hardware based logger while a thermal camera can further measure the rise in temperature. Preliminary results show that it is trivially easy to launch an effective denial of service attack, with minimal cost and resources. © 2015 IEEE.

Kadas G.,CSSN Research Laboratory | Chatzimisios P.,CSSN Research Laboratory
Proceedings - 2011 Panhellenic Conference on Informatics, PCI 2011 | Year: 2011

Vehicular Communication Networks is a subcategory of Mobile Communications Networks which have the special characteristics of high node mobility and fast topology changes. In this paper, we outline the basic characteristics and concepts of vehicular communications while specifically investigating one of the most challenging tasks in vehicular network deployment, which is security provision. We investigate what makes the security provision a hard task in vehicular environment and examine the standardization activities that try to overcome this problem. Moreover, we present the efforts done by the scientific community to solve many critical issues that hold back the vehicular network's deployment but also support the Intelligent Transportation Systems development. Finally, we investigate standardization efforts concerning Vehicular Communications and ITS. © 2011 IEEE.

Chatzimisios P.,CSSN Research Laboratory
IEEE International Conference on Communications | Year: 2012

This paper focuses on the presentation of a simulation framework, prototyping environment and demonstration scenario developed in the context of the Self-NET Future Internet mechanisms. Self management mechanisms of Future Internet elements are introduced, which incorporate the Monitoring, Decision making and Execution cognitive cycles. Such functionality enables the envisaged elements to sense their environment and adapt to it dynamically. The scenario described here is the one related to coverage and capacity optimization. The cognitive framework of the network elements and the implemented Future Internet mechanisms are presented, along with the findings originated by the performance measurements on the developed prototypes. In order to enable the evaluation of the proposed schemes, a set of assessment metrics are identified and the scenario is fragmented in simpler test cases. © 2012 IEEE.

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