Apostolis Xenakis | University of Thessaly (original) (raw)

Papers by Apostolis Xenakis

Lecture notes in networks and systems, Aug 3, 2022

In this research, we design an open, easy-to-use robotics platform for education applications, fo... more In this research, we design an open, easy-to-use robotics platform for education applications, focused on primary education. Our platform is statisti- cally evaluated and is modular, expandable, and scalable in terms of supporting the development of new modules. Our proposed platform, in contrast to other commercial ones, is easy to use, cheap and modular. Additionally, we present initial results regarding the evaluation of the usage of the proposed robotic struc- ture under the Technology Acceptance Model (TAM), in terms of easiness of usage. According to the results, the proposed open educational robotic platform shows a positive effect towards its usage by active teachers.

2022 10th International Conference on Information and Education Technology (ICIET)

In this paper, an open-source, easy-to-use robotics platform for educational applications, focuse... more In this paper, an open-source, easy-to-use robotics platform for educational applications, focused on primary education is presented. The platform is statistically evaluated, is modular, expandable, and scalable in terms of can be equipped with new modules' development. In contrast to other commercial ones, is affordable to buy (cheap), modular, and easy to use. In addition, the initial results regarding the evaluation of its usage are presented, under the Technology Acceptance Model (TAM), specifically in terms of easiness of usage. Based on the results, the proposed educational robotic platform showed a positive effect towards its usage by teachers.

Computers & Electrical Engineering

Abstract In this work, we use an unequal energy distribution algorithm, with which we succeed to ... more Abstract In this work, we use an unequal energy distribution algorithm, with which we succeed to extend network lifetime. In the sequel, we, we provide the best effort coverage by arranging the nodes using topology control principles. We formulate an optimization problem and define an objective function that incorporates both network coverage and lifetime that should be both maximized. Such a complex problem can be solved in polynomial time through Simulated Annealing (SA). An updated topology is evaluated in each convergence point and a near optimal node placement together with near optimal unequal energy allocation charge scheme is achieved. Results reveal that the proposed near optimal topology leads to greater coverage and lifetime as compared to several random deployments. We complete this work by providing a reliability study of the results, which is carried out by analysing the survival function of the derived statistical propertied of the proposed objective function.

2007 International Conference on Sensor Technologies and Applications (SENSORCOMM 2007), 2007

In this paper a new way to build a wireless sensor network is proposed, which is based on measuri... more In this paper a new way to build a wireless sensor network is proposed, which is based on measuring the field's electrical conductivity, staying away from the classic network grid implementation. Furthermore it is explained how a typical WSN works, which are the pros and cons and the technical characteristics, as well as how electrical conductivity can influence the decision to build the WSN topology and the advantage of this approach comparing to the typical ones.

Proceedings of the 6th …, 2007

Production Planning & Control, 1998

... manufacturing concern in India SK MUKHOPADHYAY, JAYANT DWIVEDY and ASHISH KUMAR ... SK Mukhop... more ... manufacturing concern in India SK MUKHOPADHYAY, JAYANT DWIVEDY and ASHISH KUMAR ... SK Mukhopadhyay has been serving as a Professor at National Institute of Industrial Engineering (NITIE), Vihar Lake, Mumbai 400087, India, since 1980. ...

Asia-Pacific Signal and Information Processing Association Annual Summit and Conference, 2012

In a Wireless Sensor Network (WSN) the sensed data must be gathered and transmitted to a base sta... more In a Wireless Sensor Network (WSN) the sensed data must be gathered and transmitted to a base station where it is further processed by end users. Since that kind of network consists of low-power nodes with limited battery power, power efficient methods must be applied for node communication and data gathering in order to achieve long network lifetimes. In such networks where in a round of communication many sensor nodes have data to send to a base station, it is very important to minimize the total energy consumed by the system so that the total network lifetime is maximized. The lifetime of such sensor network is the time until base station can receive data from all sensors in the network. In this work 1 , besides the conventional protocol of direct transmission or the use of dynamic routing protocols proposed in literature that potentially aggregates data, we propose an algorithm based on static routing among sensor nodes with unequal energy distribution in order to extend network lifetime and find a near-optimal node energy charge scheme that leads to both node and network lifetime prolongation. Our simulation results show that our algorithm achieves longer network lifetimes mainly because the final energy charge of each node is not uniform, while each node is free from maintaining complex route information and thus less infrastructure communication is needed. I.

Proceedings of The 2012 Asia Pacific Signal and Information Processing Association Annual Summit and Conference, 2012

In a Wireless Sensor Network (WSN) the sensed data must be gathered and transmitted to a base sta... more In a Wireless Sensor Network (WSN) the sensed data must be gathered and transmitted to a base station where it is further processed by end users. Since that kind of network consists of low-power nodes with limited battery power, power efficient methods must be applied for node communication and data gathering in order to achieve long network lifetimes. In such networks where in a round of communication many sensor nodes have data to send to a base station, it is very important to minimize the total energy consumed by the system so that the total network lifetime is maximized. The lifetime of such sensor network is the time until base station can receive data from all sensors in the network. In this work1, besides the conventional protocol of direct transmission or the use of dynamic routing protocols proposed in literature that potentially aggregates data, we propose an algorithm based on static routing among sensor nodes with unequal energy distribution in order to extend network l...

2018 South-Eastern European Design Automation, Computer Engineering, Computer Networks and Society Media Conference (SEEDA_CECNSM), 2018

Nowadays real application traffic, and especially streaming applications running in multi core en... more Nowadays real application traffic, and especially streaming applications running in multi core environments require more and more bandwidth. Networks on Chips (NoC) should be able not only to provide adequate bandwidth resources but also variable length traffic with multi rate packets, each representing a different class of service (FEC classes) and hence, it should provide QoS support. It is common knowledge that in original networks, QoS provision along with packet forwarding and routing at high rates is supported by the MPLS concept. This paper is a brief and compact survey, that gives a smart look on critical design issues of MPLS technology applied in NoCs, based on recent reference work. All types of MPLS based NoC architectures are presented and their pros and cons are discussed. Moreover, other important issues are pointed out, such as non interference, security and fault management, giving researchers motivation and directions for extended research.

The aim of this research is to suggest a didactic approach as to how students comprehend the grow... more The aim of this research is to suggest a didactic approach as to how students comprehend the growth and the activities of the two most well-known Ancient Greek civilizations (i.e. the Mycenaean and the Cycladic). The teaching approach is based on STEM perspective, the use of several digital technologies, as well as several learning theories. Digital technologies help students delve into the process of scientific discovery. The degree of new technology and STEM – based didactic approach appealing to students is evaluated through questionnaires. In particular, in our survey, 115 students participated and the questionnaires distributed to four schools of Volos and Veria Greece region. The Research was carried out with the consensus of their parents. According to our results, students expressed great interest in STEM activities that they were exposed to. Moreover, they expressed high interest in the integration of a classic history lesson with new technologies and they developed the abi...

Wireless Personal Communications

In this paper, we study the aggregation between the frequency division duplex and time division d... more In this paper, we study the aggregation between the frequency division duplex and time division duplex (TDD) spectrum bands within the context of 3GPP LTE-A system. To be specific, we first provide a cross-layer design analysis to obtain the achievable throughput using the TDD mode for transmission in LTE-A system. Under particular QoS requirements and certain channel conditions, the achievable throughput is derived and evaluated. The QoS requirements required from the upper layers, where the file size, the TCP window size and the latency for efficient transmission are incorporated in the final formulation. Having obtained the formulation, simulation results highlight the impact of the QoS parameters to different TDD frame format, wherein the number of DL and UL subframes vary. Having taken into account this design aspects, we propose a framework for TDD frame adaptation within the LTE-A system. The aim of this framework is to provide the dynamic configuration of different TDD frame formats by calculating the DL:UL subframes ratio under certain channel conditions and QoS requirements. We also provide flowchart procedures of how such a solution could be implemented within the 3GPP LTE-A context. Simulation results are carried out, which reveal the probability of choosing the different TDD frame formats from the system under certain channel conditions and QoS requirements.

A Wireless Sensor Network (WSN) consists of low-cost and low-power nodes with limited battery pow... more A Wireless Sensor Network (WSN) consists of low-cost and low-power nodes with limited battery power and energy efficient communication methods. The network lifetime is defined as the cumulative active time of the network until the first node failure due to energy shortage. In this work, we devise an unequal energy distribution algorithm, which guarantees an energy charge allocation scheme that extends the network lifetime. In the sequel, we provide the best effort coverage by arranging the nodes using topology control principles. In particular, we formulate an optimization problem and define an objective function that incorporates both network coverage and lifetime that should be both maximized. Such a maximization problem that requires nodes placement while maintaining topology related constraints is indeed a complex problem. Thus, we use a meta-heuristic method known as Simulated Annealing (SA) to provide near optimal result in polynomial time. Using SA, an updated topology is eva...

Extending network lifetime is a primary design objective for a wireless sensor network. Efficient... more Extending network lifetime is a primary design objective for a wireless sensor network. Efficient clustering among sensor nodes seems a promising solution to evenly balance energy consumption and thus extend node and network lifetime. One of the most dominant clustering algorithms for energy efficient cluster formation is considered LEACH, because it balances node energy consumption. However, LEACH’s stochastic cluster head election poses problems. In this paper, we analyze the effectiveness of LEACH protocol in cluster – head selection and propose a new clustering algorithm, named Minimum Weighted Clustering Algorithm (MWCLA). MWCLA functions as follows: 1) Selects cluster heads based on a distance criterion among nodes and quantifies the suitability of a candidate cluster head by applying weights and 2) Rotates cluster head roles among nodes in a deterministic and not random (stochastic) way, based on a metric that incorporates cluster head weights and residual energy levels. Usin...

Στην εργασία αυτή παρουσιάζεται ένας αλγόριθμος τοποθέτησης αισθητήρων, ο οποίος με βάση τις ζώνε... more Στην εργασία αυτή παρουσιάζεται ένας αλγόριθμος τοποθέτησης αισθητήρων, ο οποίος με βάση τις ζώνες διαχείρισης που έχουν παραχθεί από τη μέτρηση της αγωγιμότητας σε ένα χωράφι, αρχικά τοποθετεί κόμβους στα κεντροειδή των ζωνών αυτών και μετά με βάση τον υπολογισμό του συνόλου και των τοποθεσιών των πιθανών πατέρων του κάθε κόμβου που απαιτούνται για τη δημιουργία ενόςspanning tree, προτείνει το τελικό πλήθος και την τελική τοποθεσία των κόμβων που θα αποτελούν ουσιαστικά έναν άκυκλο γράφο. Έτσι, με λιγότερους κόμβους από όσους θα απαιτούνταν σε μίαgrid τοπολογία λαμβάνουμε εφάμιλλες ποιοτικές και ποσοτικές μετρήσεις, εξοικονομώντας ενέργεια και μειώνοντας το κόστος της λύσης.

Αν και οι μοντέρνες στρατηγικές σχεδίασης έχουν ώς κύρια κριτήριά τους την εφαρμογή ασφάλειας(sec... more Αν και οι μοντέρνες στρατηγικές σχεδίασης έχουν ώς κύρια κριτήριά τους την εφαρμογή ασφάλειας(security), επιδεξιότητας (manageability), εξελιξιμότητας(scalability), οι περιορισμοί στο εύρος ζώνης αποτελεί μέγιστο παράγοντα μείωσης της απόδοσης του δικτύου διότι όλη η πληροφορία μεταχειρίζεται με τον ίδιο τρόπο. Μία νέα ανερχόμενη τεχνική, που καλείται δικτυακή κωδικοποίηση(network coding) [1],[2],[3],[4] καταρρίπτει της προηγούμενη υπόθεση και αυξάνει τη ρυθμαπόδοση (throughput) με το να επιτρέπει σε ένα κόμβο να συνδυάζει- πολυπλέκει πακέτα που έχει λάβει ή/και έχει ο ίδιος παράγει σε νέα εξερχόμενα πακέτα[5]. Ένα απλό σενάριο στο οποίο απεικονίζεται η τεχνική της δικτυακής κωδικοποίησης είναι το γνωστό“Alice και Bob”

The objective of this paper is to explain how a typical WSN works, which are the pros and cons an... more The objective of this paper is to explain how a typical WSN works, which are the pros and cons and the technical characteristics, as well as the financial benefits by applying sensor technology in the field. Furthermore a new method of network topology construction is proposed based on electrical conductivity and management zones.

Energy-aware connectivity in wireless sensor networks (WSNs) can increase their network lifetime.... more Energy-aware connectivity in wireless sensor networks (WSNs) can increase their network lifetime. This can be achieved by optimizing the power control, a particular communication mechanism and the topology control. To this end, in this paper', an energy-aware joint power, packet and topology optimization for WSNs is provided. More specifically, we assume power control based on feedback information, packet transmission through automatic-repeat-request(ARQ) mechanism and topology control assuming specific coverage constraints. This particular joint optimization problem is considered as NP-complete and heuristic methods are usually applied in such complicated cases. In particular, we employ Simulated Annealing (SA) for a step-by-step evaluation of the average energy consumption of sensor nodes, which is considered the objective function of our optimization problem. In each step of the SA algorithm, the resultant topology is evaluated and at the convergence point the near optimal transmit power and packet as well as node placements are obtained jointly.

Proceedings of the 6th …, 2007

In this paper we are going to propose a new way to build a wireless sensor network which is based... more In this paper we are going to propose a new way to build a wireless sensor network which is based on measuring the field's electrical conductivity, staying away from the classic network grid implementation. Furthermore we are going to explain the way a typical WSN works, which are the pros and cons and the technical characteristics, as well as how electrical conductivity can influence our decision to build the WSN topology and the advantage of this approach comparing to the typical ones.

Sensor …, 2007

In this paper a new way to build a wireless sensor network is proposed, which is based on measuri... more In this paper a new way to build a wireless sensor network is proposed, which is based on measuring the field's electrical conductivity, staying away from the classic network grid implementation. Furthermore it is explained how a typical WSN works, which are the pros and cons and the technical characteristics, as well as how electrical conductivity can influence the decision to build the WSN topology and the advantage of this approach comparing to the typical ones.

Lecture notes in networks and systems, Aug 3, 2022

In this research, we design an open, easy-to-use robotics platform for education applications, fo... more In this research, we design an open, easy-to-use robotics platform for education applications, focused on primary education. Our platform is statisti- cally evaluated and is modular, expandable, and scalable in terms of supporting the development of new modules. Our proposed platform, in contrast to other commercial ones, is easy to use, cheap and modular. Additionally, we present initial results regarding the evaluation of the usage of the proposed robotic struc- ture under the Technology Acceptance Model (TAM), in terms of easiness of usage. According to the results, the proposed open educational robotic platform shows a positive effect towards its usage by active teachers.

2022 10th International Conference on Information and Education Technology (ICIET)

In this paper, an open-source, easy-to-use robotics platform for educational applications, focuse... more In this paper, an open-source, easy-to-use robotics platform for educational applications, focused on primary education is presented. The platform is statistically evaluated, is modular, expandable, and scalable in terms of can be equipped with new modules' development. In contrast to other commercial ones, is affordable to buy (cheap), modular, and easy to use. In addition, the initial results regarding the evaluation of its usage are presented, under the Technology Acceptance Model (TAM), specifically in terms of easiness of usage. Based on the results, the proposed educational robotic platform showed a positive effect towards its usage by teachers.

Computers & Electrical Engineering

Abstract In this work, we use an unequal energy distribution algorithm, with which we succeed to ... more Abstract In this work, we use an unequal energy distribution algorithm, with which we succeed to extend network lifetime. In the sequel, we, we provide the best effort coverage by arranging the nodes using topology control principles. We formulate an optimization problem and define an objective function that incorporates both network coverage and lifetime that should be both maximized. Such a complex problem can be solved in polynomial time through Simulated Annealing (SA). An updated topology is evaluated in each convergence point and a near optimal node placement together with near optimal unequal energy allocation charge scheme is achieved. Results reveal that the proposed near optimal topology leads to greater coverage and lifetime as compared to several random deployments. We complete this work by providing a reliability study of the results, which is carried out by analysing the survival function of the derived statistical propertied of the proposed objective function.

2007 International Conference on Sensor Technologies and Applications (SENSORCOMM 2007), 2007

In this paper a new way to build a wireless sensor network is proposed, which is based on measuri... more In this paper a new way to build a wireless sensor network is proposed, which is based on measuring the field's electrical conductivity, staying away from the classic network grid implementation. Furthermore it is explained how a typical WSN works, which are the pros and cons and the technical characteristics, as well as how electrical conductivity can influence the decision to build the WSN topology and the advantage of this approach comparing to the typical ones.

Proceedings of the 6th …, 2007

Production Planning & Control, 1998

... manufacturing concern in India SK MUKHOPADHYAY, JAYANT DWIVEDY and ASHISH KUMAR ... SK Mukhop... more ... manufacturing concern in India SK MUKHOPADHYAY, JAYANT DWIVEDY and ASHISH KUMAR ... SK Mukhopadhyay has been serving as a Professor at National Institute of Industrial Engineering (NITIE), Vihar Lake, Mumbai 400087, India, since 1980. ...

Asia-Pacific Signal and Information Processing Association Annual Summit and Conference, 2012

In a Wireless Sensor Network (WSN) the sensed data must be gathered and transmitted to a base sta... more In a Wireless Sensor Network (WSN) the sensed data must be gathered and transmitted to a base station where it is further processed by end users. Since that kind of network consists of low-power nodes with limited battery power, power efficient methods must be applied for node communication and data gathering in order to achieve long network lifetimes. In such networks where in a round of communication many sensor nodes have data to send to a base station, it is very important to minimize the total energy consumed by the system so that the total network lifetime is maximized. The lifetime of such sensor network is the time until base station can receive data from all sensors in the network. In this work 1 , besides the conventional protocol of direct transmission or the use of dynamic routing protocols proposed in literature that potentially aggregates data, we propose an algorithm based on static routing among sensor nodes with unequal energy distribution in order to extend network lifetime and find a near-optimal node energy charge scheme that leads to both node and network lifetime prolongation. Our simulation results show that our algorithm achieves longer network lifetimes mainly because the final energy charge of each node is not uniform, while each node is free from maintaining complex route information and thus less infrastructure communication is needed. I.

Proceedings of The 2012 Asia Pacific Signal and Information Processing Association Annual Summit and Conference, 2012

In a Wireless Sensor Network (WSN) the sensed data must be gathered and transmitted to a base sta... more In a Wireless Sensor Network (WSN) the sensed data must be gathered and transmitted to a base station where it is further processed by end users. Since that kind of network consists of low-power nodes with limited battery power, power efficient methods must be applied for node communication and data gathering in order to achieve long network lifetimes. In such networks where in a round of communication many sensor nodes have data to send to a base station, it is very important to minimize the total energy consumed by the system so that the total network lifetime is maximized. The lifetime of such sensor network is the time until base station can receive data from all sensors in the network. In this work1, besides the conventional protocol of direct transmission or the use of dynamic routing protocols proposed in literature that potentially aggregates data, we propose an algorithm based on static routing among sensor nodes with unequal energy distribution in order to extend network l...

2018 South-Eastern European Design Automation, Computer Engineering, Computer Networks and Society Media Conference (SEEDA_CECNSM), 2018

Nowadays real application traffic, and especially streaming applications running in multi core en... more Nowadays real application traffic, and especially streaming applications running in multi core environments require more and more bandwidth. Networks on Chips (NoC) should be able not only to provide adequate bandwidth resources but also variable length traffic with multi rate packets, each representing a different class of service (FEC classes) and hence, it should provide QoS support. It is common knowledge that in original networks, QoS provision along with packet forwarding and routing at high rates is supported by the MPLS concept. This paper is a brief and compact survey, that gives a smart look on critical design issues of MPLS technology applied in NoCs, based on recent reference work. All types of MPLS based NoC architectures are presented and their pros and cons are discussed. Moreover, other important issues are pointed out, such as non interference, security and fault management, giving researchers motivation and directions for extended research.

The aim of this research is to suggest a didactic approach as to how students comprehend the grow... more The aim of this research is to suggest a didactic approach as to how students comprehend the growth and the activities of the two most well-known Ancient Greek civilizations (i.e. the Mycenaean and the Cycladic). The teaching approach is based on STEM perspective, the use of several digital technologies, as well as several learning theories. Digital technologies help students delve into the process of scientific discovery. The degree of new technology and STEM – based didactic approach appealing to students is evaluated through questionnaires. In particular, in our survey, 115 students participated and the questionnaires distributed to four schools of Volos and Veria Greece region. The Research was carried out with the consensus of their parents. According to our results, students expressed great interest in STEM activities that they were exposed to. Moreover, they expressed high interest in the integration of a classic history lesson with new technologies and they developed the abi...

Wireless Personal Communications

In this paper, we study the aggregation between the frequency division duplex and time division d... more In this paper, we study the aggregation between the frequency division duplex and time division duplex (TDD) spectrum bands within the context of 3GPP LTE-A system. To be specific, we first provide a cross-layer design analysis to obtain the achievable throughput using the TDD mode for transmission in LTE-A system. Under particular QoS requirements and certain channel conditions, the achievable throughput is derived and evaluated. The QoS requirements required from the upper layers, where the file size, the TCP window size and the latency for efficient transmission are incorporated in the final formulation. Having obtained the formulation, simulation results highlight the impact of the QoS parameters to different TDD frame format, wherein the number of DL and UL subframes vary. Having taken into account this design aspects, we propose a framework for TDD frame adaptation within the LTE-A system. The aim of this framework is to provide the dynamic configuration of different TDD frame formats by calculating the DL:UL subframes ratio under certain channel conditions and QoS requirements. We also provide flowchart procedures of how such a solution could be implemented within the 3GPP LTE-A context. Simulation results are carried out, which reveal the probability of choosing the different TDD frame formats from the system under certain channel conditions and QoS requirements.

A Wireless Sensor Network (WSN) consists of low-cost and low-power nodes with limited battery pow... more A Wireless Sensor Network (WSN) consists of low-cost and low-power nodes with limited battery power and energy efficient communication methods. The network lifetime is defined as the cumulative active time of the network until the first node failure due to energy shortage. In this work, we devise an unequal energy distribution algorithm, which guarantees an energy charge allocation scheme that extends the network lifetime. In the sequel, we provide the best effort coverage by arranging the nodes using topology control principles. In particular, we formulate an optimization problem and define an objective function that incorporates both network coverage and lifetime that should be both maximized. Such a maximization problem that requires nodes placement while maintaining topology related constraints is indeed a complex problem. Thus, we use a meta-heuristic method known as Simulated Annealing (SA) to provide near optimal result in polynomial time. Using SA, an updated topology is eva...

Extending network lifetime is a primary design objective for a wireless sensor network. Efficient... more Extending network lifetime is a primary design objective for a wireless sensor network. Efficient clustering among sensor nodes seems a promising solution to evenly balance energy consumption and thus extend node and network lifetime. One of the most dominant clustering algorithms for energy efficient cluster formation is considered LEACH, because it balances node energy consumption. However, LEACH’s stochastic cluster head election poses problems. In this paper, we analyze the effectiveness of LEACH protocol in cluster – head selection and propose a new clustering algorithm, named Minimum Weighted Clustering Algorithm (MWCLA). MWCLA functions as follows: 1) Selects cluster heads based on a distance criterion among nodes and quantifies the suitability of a candidate cluster head by applying weights and 2) Rotates cluster head roles among nodes in a deterministic and not random (stochastic) way, based on a metric that incorporates cluster head weights and residual energy levels. Usin...

Στην εργασία αυτή παρουσιάζεται ένας αλγόριθμος τοποθέτησης αισθητήρων, ο οποίος με βάση τις ζώνε... more Στην εργασία αυτή παρουσιάζεται ένας αλγόριθμος τοποθέτησης αισθητήρων, ο οποίος με βάση τις ζώνες διαχείρισης που έχουν παραχθεί από τη μέτρηση της αγωγιμότητας σε ένα χωράφι, αρχικά τοποθετεί κόμβους στα κεντροειδή των ζωνών αυτών και μετά με βάση τον υπολογισμό του συνόλου και των τοποθεσιών των πιθανών πατέρων του κάθε κόμβου που απαιτούνται για τη δημιουργία ενόςspanning tree, προτείνει το τελικό πλήθος και την τελική τοποθεσία των κόμβων που θα αποτελούν ουσιαστικά έναν άκυκλο γράφο. Έτσι, με λιγότερους κόμβους από όσους θα απαιτούνταν σε μίαgrid τοπολογία λαμβάνουμε εφάμιλλες ποιοτικές και ποσοτικές μετρήσεις, εξοικονομώντας ενέργεια και μειώνοντας το κόστος της λύσης.

Αν και οι μοντέρνες στρατηγικές σχεδίασης έχουν ώς κύρια κριτήριά τους την εφαρμογή ασφάλειας(sec... more Αν και οι μοντέρνες στρατηγικές σχεδίασης έχουν ώς κύρια κριτήριά τους την εφαρμογή ασφάλειας(security), επιδεξιότητας (manageability), εξελιξιμότητας(scalability), οι περιορισμοί στο εύρος ζώνης αποτελεί μέγιστο παράγοντα μείωσης της απόδοσης του δικτύου διότι όλη η πληροφορία μεταχειρίζεται με τον ίδιο τρόπο. Μία νέα ανερχόμενη τεχνική, που καλείται δικτυακή κωδικοποίηση(network coding) [1],[2],[3],[4] καταρρίπτει της προηγούμενη υπόθεση και αυξάνει τη ρυθμαπόδοση (throughput) με το να επιτρέπει σε ένα κόμβο να συνδυάζει- πολυπλέκει πακέτα που έχει λάβει ή/και έχει ο ίδιος παράγει σε νέα εξερχόμενα πακέτα[5]. Ένα απλό σενάριο στο οποίο απεικονίζεται η τεχνική της δικτυακής κωδικοποίησης είναι το γνωστό“Alice και Bob”

The objective of this paper is to explain how a typical WSN works, which are the pros and cons an... more The objective of this paper is to explain how a typical WSN works, which are the pros and cons and the technical characteristics, as well as the financial benefits by applying sensor technology in the field. Furthermore a new method of network topology construction is proposed based on electrical conductivity and management zones.

Energy-aware connectivity in wireless sensor networks (WSNs) can increase their network lifetime.... more Energy-aware connectivity in wireless sensor networks (WSNs) can increase their network lifetime. This can be achieved by optimizing the power control, a particular communication mechanism and the topology control. To this end, in this paper', an energy-aware joint power, packet and topology optimization for WSNs is provided. More specifically, we assume power control based on feedback information, packet transmission through automatic-repeat-request(ARQ) mechanism and topology control assuming specific coverage constraints. This particular joint optimization problem is considered as NP-complete and heuristic methods are usually applied in such complicated cases. In particular, we employ Simulated Annealing (SA) for a step-by-step evaluation of the average energy consumption of sensor nodes, which is considered the objective function of our optimization problem. In each step of the SA algorithm, the resultant topology is evaluated and at the convergence point the near optimal transmit power and packet as well as node placements are obtained jointly.

Proceedings of the 6th …, 2007

In this paper we are going to propose a new way to build a wireless sensor network which is based... more In this paper we are going to propose a new way to build a wireless sensor network which is based on measuring the field's electrical conductivity, staying away from the classic network grid implementation. Furthermore we are going to explain the way a typical WSN works, which are the pros and cons and the technical characteristics, as well as how electrical conductivity can influence our decision to build the WSN topology and the advantage of this approach comparing to the typical ones.

Sensor …, 2007

In this paper a new way to build a wireless sensor network is proposed, which is based on measuri... more In this paper a new way to build a wireless sensor network is proposed, which is based on measuring the field's electrical conductivity, staying away from the classic network grid implementation. Furthermore it is explained how a typical WSN works, which are the pros and cons and the technical characteristics, as well as how electrical conductivity can influence the decision to build the WSN topology and the advantage of this approach comparing to the typical ones.