1. Πτυχιακές και Διπλωματικές Εργασίες
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Πλοήγηση 1. Πτυχιακές και Διπλωματικές Εργασίες ανά Συγγραφέα "Efstathiou, Dimitrios"
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Τεκμήριο Medium Access Control (MAC) Standards for Wireless Body Area Networks (WBANs) and Security Considerations(Τ.Ε.Ι. Κεντρικής Μακεδονίας, 2016-03) Gavouchidis, Kiriakos; Γαβουχίδης, Κυριάκος; Efstathiou, Dimitrios; Ευσταθίου, Δημήτριος; Σχολή Τεχνολογικών Εφαρμογών, Τμήμα Μηχανικών Πληροφορικής Τ.Ε.; Master’s Degree in Communication and Information SystemsWBANs are a key element to the ubiquitous healthcare revolution. From the communication point of view, they are one of the most challenging elements for this application and also other application areas such as military, sport, or entertainment. New applications and requirements force the development of the WBAN technology, e.g. the MAC sublayer protocol and its existing and future standards. Every standard described in this Master Thesis represents an evolution of the previous standard according to the application needs with the goal to find solutions for the existing challenges in WBANs. One main issue in WBANs is to minimize energy consumption due to the fact that the nodes may be implanted in the human body, so batteries can not be replaced after a small time period. Minimal energy consumption is a critical factor for the survive of WBAN technology. This work consists of two parts. The first part describes the MAC sublayer standards for WBANs. The second part of the work analyzes the security of WBANs. The first part starts with the description of the different types of existing WBANs, we present the main application areas of WBANs and analyze their manifold requirements. Some of these requirements, mentioned here as an example, are: Long battery life, power consumption, scalability, network topology to be implemented, and WBAN co-existence. Then we refer to the services and the functionality of the MAC sublayer protocol for WBANs and to the different channel access methods such as TDMA and CSMA/CA. The analysis and description of the existing MAC sublayer protocol standards follows. The MAC sublayer is part of the Data Link Layer of the ISO-OSI standard. The MAC protocol is mainly responsible and regulates the WBAN access to the channel. We study the ΙΕΕΕ 802.15.1, the Bluetooth LE, the ΙΕΕΕ 802.15.4, the IEEE 802.15.4a, the IEEE 802.14.4j, the IEEE 802.15.6, and the SmartBAN standard. After their detailed description, especially of the IEEE 802.15.6 standard, we compare them with each other, and emphasize their advantages and disadvantages. The explanation of more than thirty MAC sublayer protocol implementations for WBANs are the next part of the work. Implementations like H-MAC, BodyMAC, TRAMA, LEACH, STEM, P-MAC, and also RuBee, and ANT+, complete the picture. The last section of the first part is dedicated to the challenges of this exciting technology. Security and privacy for WBANs are defined at the second part of this Master Thesis. We analyze three different types of WBAN attacks, the DoS attack type, attacks on secrecy and authentication, and attacks on service integrity. For the first and second type of attacks we describe concrete attacks from the WBAN praxis. Some of the presented attacks are the Flooding attack, the De-synchronization attack, the Sinkhole attack, the Misdirection attack, the Homing attack, the Collision attack, and the Unfairness attack. After every attack description we discuss the countermeasures against them and the weakness if any, to act against them successful. We analyze the differences between Wireless Sensor Networks (WSN) and WBANs having security in focus. At the end of part two we present the security characteristics of the MAC sublayer standards, with reference to their advantages, their disadvantages, and the challenges. A summary of the MAC sublayer protocol standards and the WBAN security concludes the Master Thesis.Τεκμήριο Study and simulation of LTE physical uplink shared channel (PUSCH)(Τ.Ε.Ι. Κεντρικής Μακεδονίας, 2013-12) Zachos, Athanasios; Ζάχος, Αθανάσιος; Efstathiou, Dimitrios; Ευσταθίου, Δημήτριος; Σχολή Τεχνολογικών Εφαρμογών, Τμήμα Μηχανικών Πληροφορικής Τ.Ε.; Master’s Degree in Communication and Information SystemsThe purpose of this thesis is the study and simulation of LTE’s Physical Uplink Shared Channel (PUSCH), a physical channel for data transfer. This thesis is structured in five chapters. The first chapter makes an introduction to LTE and its evolution. It also gives a discussion of the reasons and driving forces behind the LTE evolution. Furthermore, some interesting features of LTE (spectrum and bandwidth flexibility) described in depth. In chapter two LTE network and protocol architecture are described. Chapter three provides a deeper insight in the physical uplink layer and the PUSCH channel. In chapter four, a new improved system which extended the capabilities of LTE and called LTE-Advanced is described. This chapter covers the new features of LTE-Advanced by focusing on Carrier Aggregation, enhancements to multiple antenna transmission to the uplink and downlink (MIMO), Relaying, Heterogeneous Deployments and Coordinated MultiPoint (CoMP) Transmission and Reception. Finally, in chapter five laid down and analyzed simulations results made through the MATLAB program and relating at measurement of BER in the PUSCH channel. Comparisons are made for various parameters taken into account (FFT size, Modulation Scheme, Bandwidth etc.).