@conference {
	title = {Optimization and Resource Management in NOMA Wireless Networks Supporting Real and Non-real Time Service Bundling},
	author = {Vamvakas, Panagiotis, Tsiropoulou, Eirini Eleni., Papavassiliou, Symeon., Baras, John S.},
	year = {2017},
	month = {07/2017},
	abstract = {In this paper, the problem of joint users{\textquoteright} uplink transmission power and rate allocation in NOMA wireless networks is studied, under the scenario that each user is simultaneously requesting multiple services. Each user is associated with a twovariable utility function that represents his satisfaction from his allocated resources (i.e., power and rate). In order to appropriately reflect the combined needs of the user for bundling different types of services under the same common umbrella, user{\textquoteright}s utility function consists of two parts while different percentages are adopted by each user for each part in order to express his need for real and nonreal-time services. The joint resource allocation problem is directly confronted as a two-variable optimization problem and formulated as a non-cooperative game. The theory of S-modular multivariable games is adopted towards determining the Nash equilibrium point of the game. A distributed, iterative and low complexity algorithm for computing game{\textquoteright}s Nash equilibrium is introduced, while updating user{\textquoteright}s uplink transmission power and rate at the same step. Detailed numerical results exhibit the ability of the proposed framework to simultaneously satisfy diverse multiple services requested by the same user.},
	address = {Crete, Greece},
	booktitle = {22nd IEEE Symposium on Computers and Communication (ISCC 2017)},
	pages = {pp. 699-705}
}
@conference {
	title = {On the Mitigation of Interference Imposed by Intruders in Passive RFID Networks},
	author = {Tsiropoulou, Eirini Eleni., Baras, John S., Papavassiliou, Symeon., Qu, G.},
	year = {2016},
	month = {11/2016},
	abstract = {RFID networks are becoming an integral part of the emerging Internet of Things (IoT) era. Within this paradigm passive RFID networks have emerged as low cost energy-efficient alternatives that find applicability in a wide range of applications. However, such RFID networks and devices, due to their limited capabilities, can easily become vulnerable to several intrusive actions. In this paper, the problem of proactively protecting a passive RFID network from security threats imposed by intruders that introduce high interference to the system resulting in the possible disruption of the network{\textquoteright}s proper operation is investigated. Passive RFID tags are associated with a well-designed utility function reflecting on one hand their goal to have their signal properly demodulated by the reader, and on the other hand their risk level of participating in the network, stemming from their hardware characteristics among others, thus characterizing them as normal or intruder tags. An interference mitigation risk aware (IMRA) problem is introduced aiming at maximizing each tag{\textquoteright}s utility function, thus implicitly enforcing tags to conform to a more social behavior. Due to its nature, the proposed problem is formulated as a non-cooperative game among all the tags (normal and intruders) and its Nash equilibrium point is determined via adopting the theory of supermodular games. Convergence of the game to its Nash equilibrium is also shown. A distributed iterative and low-complexity algorithm is proposed in order to obtain the Nash equilibrium point and the operational effectiveness of the proposed approach is evaluated through modeling and simulation.},
	address = {New York, NY},
	booktitle = {Conference on Decision and Game Theory for Security (GameSec 2016)}
}
@conference {
	title = {On the Mitigation of Interference Imposed by Intruders in Passive RFID Networks},
	author = {Tsiropoulou, Eirini Eleni., Baras, John S., Papavassiliou, Symeon., Qu, G.},
	year = {2016},
	month = {09/2016},
	address = {Garching, Munich},
	booktitle = {International Symposium on Networked Cyber-Physical Systems (NetCPS)}
}
@conference {
	title = {A Reputation based Trust Management System for the Internet of Things},
	author = {Papagianni, Chrysa. , Baras, John S., Papavassiliou, Symeon.},
	year = {2016},
	month = {09/2016},
	address = {Garching, Munich},
	booktitle = {International Symposium on Networked Cyber-Physical Systems (NetCPS)}
}
@conference {
	title = {A Coalitional Game Based Approach for Multi-Metric Optimal Routing in Wireless Networks},
	author = {Stai, Eleni., Papavassiliou, Symeon., Baras, John S.},
	year = {2013},
	month = {09/2013},
	abstract = {Future communications consist of an increasing number of wireless parts, while simultaneously need to support the widespread multimedia applications imposed by social networks. These human-machine systems, driven by both real time social interactions and the challenges of the wireless networks{\textquoteright} design, call for efficient and easy to implement, distributed cross-layer algorithms for their operation. Performance metrics such as throughput, delay, trust, energy consumption, need to be improved and optimized aiming at high quality communications. We investigate the coveted throughput-delay trade-off in static wireless multihop networks based on a {\textquotedblleft}computer-aided{\textquotedblright} design of the backpressure scheduling/routing algorithm for networks embedded in hyperbolic space. Both routing and scheduling exploit the hyperbolic distances to orient the packets to the destination and prioritize the transmissions correspondingly. The proposed design provides us with the freedom of controlling its theoretical throughput optimality and of counterbalancing its practical performance through simulations, leading to significant improvements of the throughput-delay trade-off.},
	address = {London, UK},
	booktitle = {Proceedings of IEEE 22nd International Symposium on Personal, Indoor and Mobile Radio Communications: Mobile and Wireless Networks},
	pages = {pp. 1935-1939}
}
@conference {
	title = {Social Networks over Wireless Networks},
	author = {Stai, Eleni., Baras, John S., Papavassiliou, Symeon.},
	year = {2012},
	month = {12/2012},
	abstract = {We consider the formation, operation and maintenance of dynamic social networks (among human users) supported by technological communication networks such as wireless networks, or hybrid wireline-wireless networks. The technological (physical) networks of interest display dynamic behavior in several dimensions, including variable connectivity, variable congestion, variable link characteristics. As broadband wireless devices and networks are becoming ubiquitous these human-machine systems, that combine the social aspects and behavioral activities of humans with the technological characteristics of the underlying physical networks, provide several important challenges in efforts to model them, evaluate their performance and dynamically control them so certain performance requirements are met. These include combinations of performance, trust, privacy, energy efficiency. In this paper we develop novel models for these complex human-machine systems that incorporate social network behavioral models and wireless network models that are inspired from statistical physics (hyperbolic graphs). We investigate the performance of wireless network protocols that support and respond to the constraints implied by the social network they support.},
	address = {Maui, Hawaii},
	booktitle = {51st IEEE Conference on Decision and Control},
	pages = {pp. 2696-2703}
}
@conference {
	title = {A Class of Backpressure Algorithms for Networks Embedded in Hyperbolic Space with Controllable Delay-Throughput Trade-off},
	author = {Stai, Eleni., Baras, John S., Papavassiliou, Symeon.},
	year = {2012},
	month = {10/2012},
	abstract = {Future communications consist of an increasing number of wireless parts, while simultaneously need to support the widespread multimedia applications imposed by social networks. These human-machine systems, driven by both real time social interactions and the challenges of the wireless networks~design, call for efficient and easy to implement, distributed cross-layer algorithms for their operation. Performance metrics such as throughput, delay, trust, energy consumption, need to be improved and optimized aiming at high quality communications. We investigate the coveted throughput-delay trade-off in static wireless multihop net- works based on a {\textquotedblleft}computer-aided{\textquotedblright} design of the backpressure scheduling/routing algorithm for networks embedded in hyperbolic space. Both routing and scheduling exploit the hyperbolic distances to orient the packets to the destination and prioritize the transmissions correspondingly. The proposed design provides us with the freedom of controlling its theoretical throughput optimality and of counterbalancing its practical performance through simulations, leading to significant improvements of the throughput-delay trade-off.},
	address = {Paphos, Cyprus Island},
	booktitle = {15th ACM International Conference on Modeling, Analysis and Simulation of Wireless and Mobile Systems (MSWiM 2012), pp. no. 15-22, Paphos, Cyprus Island},
	pages = {pp. 15-22}
}
@conference {
	title = {Throughput-Delay Trade-off in Wireless Multi-hop Networks via Greedy Hyperbolic Embedding},
	author = {Stai, Eleni., Baras, John S., Papavassiliou, Symeon.},
	year = {2012},
	month = {07/2012},
	abstract = {Real time applications over wireless multihop networks, demand routing/scheduling algorithms that achieve desirable delay-throughput trade-offs, with high throughput and low end-to-end delay. The backpressure algorithm, has received much attention by the research community in the past few years, as it satisfies the throughput optimal requirement. The backpressure algorithm performs routing and scheduling based on congestion gradients, by allowing transmission to the links that maximize the differential backlog between neighboring nodes. However, by deploying routing without using any information about the position or distance to the destination, it explores all possible source-destination paths leading to undesirable high delays. In this paper, we propose a method of restricting the number of paths used by the backpressure algorithm, with the aid of the greedy embedding of a network in the hyperbolic space. We propose two algorithms, the {\textquotedblleft}Greedy{\textquotedblright} backpressure and the {\textquotedblleft}Greediest{\textquotedblright} backpressure for both static and dynamic networks, which consider the network embedded in the hyperbolic space and combine the greedy routing in hyperbolic coordinates with the backpressure scheduling. We prove analytically their throughput optimality and study through simulations the induced improvement in the delay-throughput trade-off compared with the backpressure algorithm.},
	address = {Melbourne, Australia},
	booktitle = {20th International Symposium on Mathematical Theory of Networks and Systems (MTNS 2012)},
	pages = {pp. 1-8}
}
@article {
	title = {RFID-based Smart Parking Management System},
	author = {Tsiropoulou, Eirini Eleni., Baras, John S., Papavassiliou, Symeon., Sinha, Surbhit. },
	year = {2017},
	month = {08/2017},
	abstract = {In this paper, the adoption of passive Radio Frequency Identification (RFID) tag-to-tag communication paradigm within the context of a smart parking system is evangelised, in terms of achieving improved energy-efficiency and operational effectiveness. To demonstrate that the joint routing and RFID readers{\textquoteright} transmission power minimisation problem is studied, considering tag-to-tag communication. The superiority of the proposed framework against conventional direct RFID reader-tag communication is demonstrated in terms of: (i) reduction of RFID readers{\textquoteright} transmission power to the minimum required to guarantee connectivity, and (ii) expansion of RFID reader{\textquoteright}s coverage area towards communicating with more distant tags, otherwise unreachable through direct communication.},
	pages = {pp. 1-4, 22-41},
	volume = {Vol. 3},
	journal = {Cyber-Physical Systems}
}
@article {
	title = {Performance-Aware Cross-layer Design in Wireless Multihop Networks via a Weighted Backpressure Approach},
	author = {Stai, Eleni., Papavassiliou, Symeon., Baras, John S.},
	year = {2016},
	month = {02/2016},
	abstract = {In this paper, we study, analyze, and evaluate a performance-aware cross-layer design approach for wireless multihop networks. Through network utility maximization (NUM) and weighted network graph modeling, a cross-layer algorithm for performing jointly routing, scheduling, and congestion control is introduced. The performance awareness is achieved by both the appropriate definition of the link weights for the corresponding application{\textquoteright}s requirements and the introduction of a weighted backpressure (BP) routing/scheduling. Contrary to the conventional BP, the proposed algorithm scales the congestion gradients with the appropriately defined per-pair (link, destination) weights. We analytically prove the queue stability achieved by the proposed cross-layer scheme, while its convergence to a close neighborhood of the optimal source rates{\textquoteright} values is proven via an epslon-subgradient approach. The issue of the weights{\textquoteright} assignment based on various quality-of-service (QoS) metrics is also investigated. Through modeling and simulation, we demonstrate the performance improvements that can be achieved by the proposed approach{\textemdash}when compared against existing methodologies in the literature{\textemdash}for two different examples with diverse application requirements, emphasizing respectively on delay and trustworthiness.},
	pages = {pp. 245-258},
	volume = {Vol. 24},
	number = {Issue 1},
	journal = {IEEE ACM Transactions on Networking}
}
