@article{christidis_sikeridis_wang_devetsikiotis_2021, title={A framework for designing and evaluating realistic blockchain-based local energy markets}, volume={281}, ISSN={["1872-9118"]}, DOI={10.1016/j.apenergy.2020.115963}, abstractNote={A growing customer base for solar-plus-storage at the grid edge has resulted in stronger interest at the regulatory level towards energy markets at the distribution level. Local energy markets (LEMs) running on blockchains are being studied as a possible direction, but the relevant literature treats the blockchain component as a black box. We make the case that this approach is flawed because the choices in this layer affect the market’s performance significantly. We explicitly identify the design space that the blockchain layer introduces, and analyze how the design choices made therein affect the performance, governance, and degree of decentralization of these markets. As an exercise, we consider three distinct configurations for a next-generation LEM, and compare their performance on both the blockchain and the market layer via a case study. We demonstrate that simple changes in the data model can decrease the market efficiency by up to 90%. We also show that changes in the way bids get encrypted may result in economic improvements, but they do so at the risk of subverting the proper operation and resilience of the market. The simulations for our case study are conducted via a framework that we developed and open-sourced as part of this work.}, journal={APPLIED ENERGY}, author={Christidis, Konstantinos and Sikeridis, Dimitrios and Wang, Yun and Devetsikiotis, Michael}, year={2021}, month={Jan} }
 @article{christidis_devetsikiotis_2016, title={Adaptive multi-tiered resource allocation policy for microgrids}, volume={4}, ISSN={["2333-8334"]}, DOI={10.3934/energy.2016.2.300}, abstractNote={We consider a cluster of buildings within proximity that share a large-capacity battery for peak-shaving purposes, and draw power from the grid at a premium once they reach a certain threshold. Our goal is to identify a resource allocation policy that minimizes the amount of energy the cluster draws at a premium, while also ensuring fair access to all of its members. We introduce an adaptive policy that allows for maximum energy savings when the network load is low, and ensures fairness when the aggregate power level is high. We compare this adaptive policy with two standard resource allocation strategies with complementary advantages, and demonstrate through an extensive performance evaluation, that it combines the benefits of both. It is therefore suitable for a microgrid operator where equal weight is given to both cluster-wide cost minimization and fairness among all customers.}, number={2}, journal={AIMS ENERGY}, author={Christidis, Konstantinos and Devetsikiotis, Michael}, year={2016}, pages={300–312} }
 @article{christidis_devetsikiotis_2016, title={Blockchains and smart contracts for the internet of things}, volume={4}, DOI={10.1109/access.2016.2566339}, abstractNote={Motivated by the recent explosion of interest around blockchains, we examine whether they make a good fit for the Internet of Things (IoT) sector. Blockchains allow us to have a distributed peer-to-peer network where non-trusting members can interact with each other without a trusted intermediary, in a verifiable manner. We review how this mechanism works and also look into smart contracts-scripts that reside on the blockchain that allow for the automation of multi-step processes. We then move into the IoT domain, and describe how a blockchain-IoT combination: 1) facilitates the sharing of services and resources leading to the creation of a marketplace of services between devices and 2) allows us to automate in a cryptographically verifiable manner several existing, time-consuming workflows. We also point out certain issues that should be considered before the deployment of a blockchain network in an IoT setting: from transactional privacy to the expected value of the digitized assets traded on the network. Wherever applicable, we identify solutions and workarounds. Our conclusion is that the blockchain-IoT combination is powerful and can cause significant transformations across several industries, paving the way for new business models and novel, distributed applications.}, journal={IEEE Access}, author={Christidis, K. and Devetsikiotis, M.}, year={2016}, pages={2292–2303} }
 @article{wang_becvarik_devetsikiotis_2016, title={Modeling of Managed Resources in a Location Aware Smart Building}, DOI={10.1109/ict.2016.7500382}, abstractNote={We model the performance of the resources in a smart or intelligent building, such as a library or future museum, which relies on advanced localization, complex sensing and actuating, and possibly higher level cognitive modeling or artificial intelligence. Our focus is on establishing a quantitative link between the localization accuracy and the customer quality of service from their interaction with such an intelligent space. We describe a quantitative service model for the intelligent interaction between users and smart IT resources, which is directly affected by the localization accuracy. We provide stochastic simulation results which quantify this interplay between localization resolution and overall smart system performance (or user “quality of experience”).}, journal={2016 23RD INTERNATIONAL CONFERENCE ON TELECOMMUNICATIONS (ICT)}, author={Wang, Yun and Becvarik, Megan and Devetsikiotis, Michael}, year={2016} }
 @inproceedings{becvarik_devetsikiotis_2016, title={Modeling of user quality of experience in location aware smart spaces}, DOI={10.1109/dmiaf.2016.7574934}, abstractNote={The increasing use of interactive technologies, digital media, and dynamic content in smart spaces such as libraries and museums is improving the user experience substantially. In well-designed learning spaces, digital content can itself become a service, possibly with creative and social output to interact with users. In this paper we study the quantitative modeling of the Quality of Experience (QoE) in immersive multi-media smart spaces, such as a library or future museum. Our focus is on combining the physical world with the digital world in order to obtain a single, combined QoE.}, booktitle={2016 Digital Media Industry and Academic Forum (DMIAF)}, author={Becvarik, M. and Devetsikiotis, M.}, year={2016}, pages={207–212} }
 @article{kong_bayram_devetsikiotis_2015, title={Revenue Optimization Frameworks for Multi-Class PEV Charging Stations}, volume={3}, ISSN={["2169-3536"]}, DOI={10.1109/access.2015.2498105}, abstractNote={The charging power of plug-in electric vehicles (PEVs) decreases significantly when the state of charge (SoC) gets closer to the fully charged state, which leads to a longer charging duration. Each time when the battery is charged at high rates, it incurs a significant degradation cost that shortens the battery life. Furthermore, the differences between demand preferences, battery types, and charging technologies make the operation of the charging stations a complex problem. Even though some of these issues have been addressed in the literature, the charging station modeling with battery models and different customer preferences have been neglected. To that end, this paper proposes two queueing-based optimization frameworks. In the first one, the goal is to maximize the system revenue for single class customers by limiting the requested SoC targets. The PEV cost function is composed of battery degradation cost, the waiting cost in the queue, and the admission fee. Under this framework, the charging station is modeled as a $M/G/S/K$ queue, and the system performance is assessed based on the numerical and simulation results. In the second framework, we describe an optimal revenue model for multi-class PEVs, building upon the approach utilized in the first framework. Two charging strategies are proposed: 1) a dedicated charger model and 2) a shared charger model for the multi-class PEVs. We evaluate and compare these strategies. Results show that the proposed frameworks improve both the station performance and quality of service provided to customers. The results show that the system revenue is more than doubled when compared with the baseline scenario which includes no limitations on the requested SoC.}, journal={IEEE ACCESS}, author={Kong, Cuiyu and Bayram, Islam Safak and Devetsikiotis, Michael}, year={2015}, pages={2140–2150} }
 @inproceedings{sbordone_di pietra_carlini_devetsikiotis_2015, title={The future interaction between virtual aggregator-TSO-DSO to increase DG penetration}, DOI={10.1109/icsgce.2015.7454296}, abstractNote={The increasing integration of massive quantities of generation from Renewable Energy Sources (RES) constitutes a challenge for the pan-European system. Reserve provision for the balancing of the network is an important service that, in principle, should be provided by all the units connected to the network, including RES generators themselves as well as flexible loads and storage systems. However, these resources have big peculiarities tied with their relevant technologies and could, beyond providing local services within the distribution grids (e.g. voltage regulation, congestion management), be available to provide reserve for the entire system, through the connection points to the transmission grid. This paper shows a more advanced dispatching management of distribution systems by resorting to more advanced Information and Communications Technology(ICT) systems able to transform distribution from a “passive” into an “active” system and market architectures able to incorporate scattered bids coming from distributed generation and active load. A delicate point is the interface between transmission and distribution that has to be managed in a coordinated manner between Transmission System Operators (TSO) and Distribution System Operators (DSOs) in order to achieve an overall efficiency target. ICT should also be key to allow a strict real-time coordination of the different subjects that are in charge to actuate the provision of ancillary services. Further, the paper shows as new actors could appear in the system like the “aggregators” who interface with the Market Operator to submit the bids for the provision of the services, with the local TSO to receive the consequent dispatching orders, with to the aggregated distributed resources (generation, flexible demand, storage) and with to the involved DSOs, in order to communicate how each dispatching order will in turn be dispatched among the distributed resources it aggregates.}, booktitle={2015 International Conference on Smart Grid and Clean Energy Technologies (ICSGCE)}, author={Sbordone, D. A. and Di Pietra, B. and Carlini, E. M. and Devetsikiotis, M.}, year={2015}, pages={201–205} }
 @article{bayram_michailidis_devetsikiotis_2015, title={Unsplittable Load Balancing in a Network of Charging Stations Under QoS Guarantees}, volume={6}, ISSN={["1949-3061"]}, DOI={10.1109/tsg.2014.2362994}, abstractNote={The operation of the power grid is becoming more stressed, due to the addition of new large loads represented by electric vehicles (EVs) and a more intermittent supply due to the incorporation of renewable sources. As a consequence, the coordination and control of projected EV demand in a network of fast charging stations becomes a critical and challenging problem. In this paper, we introduce a game theoretic based decentralized control mechanism to alleviate negative impacts from the EV demand. The proposed mechanism takes into consideration the nonuniform spatial distribution of EVs that induces uneven power demand at each charging facility, and aims to: 1) avoid straining grid resources by offering price incentives, so that customers accept being routed to less busy stations; 2) maximize total revenue by serving more customers with the same amount of grid resources; and 3) provide charging service to customers with a certain level of quality-of-service (QoS), the latter defined as the long term customer blocking probability. We examine three scenarios of increased complexity that gradually approximate real world settings. The obtained results show that the proposed framework leads to substantial performance improvements in terms of the aforementioned goals when compared to current state of affairs.}, number={3}, journal={IEEE TRANSACTIONS ON SMART GRID}, author={Bayram, Islam Safak and Michailidis, George and Devetsikiotis, Michael}, year={2015}, month={May}, pages={1292–1302} }
 @article{bayram_michailidis_devetsikiotis_granelli_2013, title={Electric Power Allocation in a Network of Fast Charging Stations}, volume={31}, ISSN={["1558-0008"]}, DOI={10.1109/jsac.2013.130707}, abstractNote={In order to increase the penetration of electric vehicles, a network of fast charging stations that can provide drivers with a certain level of quality of service (QoS) is needed. However, given the strain that such a network can exert on the power grid, and the mobility of loads represented by electric vehicles, operating it efficiently is a challenging and complex problem. In this paper, we examine a network of charging stations equipped with an energy storage device and propose a scheme that allocates power to them from the grid, as well as routes customers. We examine three scenarios, gradually increasing their complexity. In the first one, all stations have identical charging capabilities and energy storage devices, draw constant power from the grid and no routing decisions of customers are considered. It represents the current state of affairs and serves as a baseline for evaluating the performance of the proposed scheme. In the second scenario, power to the stations is allocated in an optimal manner from the grid and in addition a certain percentage of customers can be routed to nearby stations. In the final scenario, optimal allocation of both power from the grid and customers to stations is considered. The three scenarios are evaluated using real traffic traces corresponding to weekday rush hour from a large metropolitan area in the US. The results indicate that the proposed scheme offers substantial improvements of performance compared to the current mode of operation; namely, more customers can be served with the same amount of power, thus enabling the station operators to increase their profitability. Further, the scheme provides guarantees to customers in terms of the probability of being blocked (and hence not served) by the closest charging station to their location. Overall, the paper addresses key issues related to the efficient operation, both from the perspective of the power grid and the drivers satisfaction, of a network of charging stations.}, number={7}, journal={IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS}, author={Bayram, I. Safak and Michailidis, George and Devetsikiotis, Michael and Granelli, Fabrizio}, year={2013}, month={Jul}, pages={1235–1246} }
 @inproceedings{saovapakhiran_michailidis_devetsikiotis_2012, title={An algorithm for joint guidance and power control for electric vehicles in the smart grid}, DOI={10.1109/icc.2012.6364112}, abstractNote={A massive amount of energy consumption currently stems from the transportation sector. Therefore, improvements in power usage by commuting vehicles are being studied and becoming an increasingly popular research topic. In particular, there is a growing need to model the envisioned smart infrastructure, including charging stations, some of which might include energy storage devices and swappable, pre-charged batteries. For such new stations, power management is indeed crucial for operation costs, driver convenience, and overall smart grid efficiency. Information technology, communications and vehicle intelligence need to play a crucial role in this process. In this paper, we describe a quantitative model and propose a guiding and control system for the charging of PHEVs in a future smart infrastructure. Specifically, we describe an algorithm that can be used for the joint guidance and power control of smarter electric vehicles in the smart grid. We envision it as part of a larger Smart Guide for the Smart Grid (SGSG) system. Its function is to guide PHEV drivers, directing them to the appropriate charging station, while attempting to achieve an optimization goal at the same time. Our algorithm aims at a joint guiding and power control, in order to heuristically maximize the weighted sum of the average of throughput and energy cost consumption from multiple vehicle charging stations, while satisfying a cost constraint at each station, as well as system stability.}, booktitle={2012 ieee international conference on communications (icc)}, author={Saovapakhiran, B. and Michailidis, G. and Devetsikiotis, M.}, year={2012} }
 @inproceedings{saovapakhiran_devetsikiotis_michailidis_viniotis_2012, title={Average delay SLAs in cloud computing}, DOI={10.1109/icc.2012.6364548}, abstractNote={In this paper, we conduct feasibility studies on the average delay space for Cloud computing, and we propose a heuristic method to control the vector of average delays, subject to predefined delay constraints. Our work is strongly motivated by the fact that delay control plays a critical role to improve Service Level Agreements (SLA) between users and Cloud service providers, which is necessary for empowering online business. Specifically, our main contributions are two-fold: First, the feasible regions of various routing algorithms for the system's dispatcher are investigated in depth. Second, a simple heuristic algorithm is designed, to move the average delay point along the feasible direction until achieving the delay constraints. Average delay is dependent on multiple factors such as job size, inter-arrival time, flow rate, and the dispatching rules of the system. Therefore, we vary their distribution, parameters and routing rules to examine how the feasible regions move or change. After establishing the feasible delay space, then by moving along the feasible directions, we show that a simple heuristic algorithm can achieve the delay constraints for a two queue system.}, booktitle={2012 ieee international conference on communications (icc)}, author={Saovapakhiran, B. and Devetsikiotis, M. and Michailidis, G. and Viniotis, Y.}, year={2012} }
 @inproceedings{ban_devetsikiotis_2012, title={Balancing network connectivity and the life-time of sensors through percolation and consensus}, DOI={10.1109/icc.2012.6364130}, abstractNote={Due to replacement infeasibility, methods to extend the life-time of sensors have been an issue in Wireless Sensor Networks (WSNs) and these should consider network connectivity simultaneously. Controlling the sleep/awake of sensors is one simple way to reduce their energy consumption. However, this causes a network connectivity degradation by varying network connection topology. For this reason, we propose a simple and autonomous sensor sleep/awake method to achieve their balance. The size of clusters can be a metric to measure network connectivity in that a path exists among any cluster node. From percolation theory, we observe that a cluster size suffers a sharp transition based on edge connection patterns. This allows us to design a sensor sleep/awake algorithm which has an immense simplicity, but still requires global topology information. In many cases, sensors are not aware of the global topology. Further, managing the information becomes challenging under physical topology changes such as sensor add/drop. We show that the global knowledge requirement can be resolved by using a consensus algorithm. Through several graph tests, we show that our method achieves a network balancing between connectivity and life-time with preserving its simplicity. Also, the balancing is autonomous even under physical topology variations.}, booktitle={2012 ieee international conference on communications (icc)}, author={Ban, D. and Devetsikiotis, M.}, year={2012} }
 @inproceedings{papapanagiotou_callaway_devetsikiotis_2012, title={Chunk and object level deduplication for web optimization: A hybrid approach}, DOI={10.1109/icc.2012.6363843}, abstractNote={Proxy caches or Redundancy Elimination (RE) systems have been used to remove redundant bytes in WAN links. However, they come with some inherited deficiencies. Proxy caches provide less savings than RE systems, and RE systems have limitations related to speed, memory and storage overhead. In this paper we advocate the use of a hybrid approach, in which each type of cache acts as a module in a system with shared memory and storage space. A static scheduler precedes the cache modules and determines what types of traffic should be forwarded to which module. We also propose several optimizations for each of the modules, such that the storage and memory overhead are minimized. We evaluate the proposed system by performing a trace driven emulation. Our results indicate that a hybrid system is able to provide better savings than a proxy cache, or a standalone RE system. The hybrid system requires less memory, less disk space and provides a speed-up ratio equal to three compared to an RE system.}, booktitle={2012 ieee international conference on communications (icc)}, author={Papapanagiotou, I. and Callaway, R. D. and Devetsikiotis, M.}, year={2012} }
 @inproceedings{ban_devetsikiotis_2011, title={A content freshness enhancement with infrastructures in mobile opportunistic networks}, DOI={10.1109/milcom.2011.6127811}, abstractNote={In mobile opportunistic networks, we investigate the effect of infrastructures on content update process. In the network, an information provider continuously generates a time-sensitive content (e.g., news, twits or military commands) whose freshness decreases with time. This information is propagated to users throughout opportunistic contacts. Users prefer to have the more recently generated (i.e., up-to-date) content. In that, they utilize a content age to compare their freshness and share only the smaller age content when an opportunistic contact occurs.}, booktitle={2011 - Milcom 2011 Military Communications Conference}, author={Ban, D. and Devetsikiotis, M.}, year={2011}, pages={997–1002} }
 @article{papapanagiotou_granelli_kliazovich_devetsikiotis_2011, title={A metamodeling approach for cross-layer optimization: A framework and application to Voice over WiFi}, volume={19}, ISSN={["1878-1462"]}, DOI={10.1016/j.simpat.2011.06.005}, abstractNote={Cross-layer design has been proposed to optimize the performance of networks by exploiting the interrelations among parameters and procedures at different levels of the protocol stack. This paper introduces a quantitative framework for the study of cross-layer interactions, which enables design engineers to analyze and quantify interlayer dependencies and to identify the optimal operating point of the system, by using network economic theory principles. The framework is then used for performance optimization of a single-cell Voice over WiFi (VoWiFi) system. Insights gained from the considered scenario enable us to define a novel cross-layer Call Admission Control (CAC) scheme. The multistage CAC takes into account Quality of Service (QoS) criteria, which provide satisfaction to the end user, as well as revenue criteria that maximize the possible profit of the WiFi provider.}, number={9}, journal={SIMULATION MODELLING PRACTICE AND THEORY}, author={Papapanagiotou, Ioannis and Granelli, Fabrizio and Kliazovich, Dzmitry and Devetsikiotis, Michael}, year={2011}, month={Oct}, pages={2117–2129} }
 @inproceedings{saovapakhiran_michailidis_devetsikiotis_2011, title={Aggregated-DAG Scheduling for Job Flow Maximization in Heterogeneous Cloud Computing}, DOI={10.1109/glocom.2011.6133611}, abstractNote={Heterogeneous computing platforms such as Grid and Cloud computing are becoming prevalent and available online. As a result, resource management in these platforms is fundamentally critical to their global performance. Under the assumption of jobs comprised of subtasks forming DAG jobs, we focus on how to increase utilization and achieve near-optimal throughput performance on heterogeneous platforms. Our analysis and proposed algorithm are analytically derived and establish that, by aggregating multiple jobs using good scheduling, a near-optimal throughput can be achieved. Consequently, its limit is asymptotically converging to a certain value and can be written in the form of the service time of subtasks. Furthermore, our analysis shows how to explicitly compute the optimal throughput of computing systems, an important task for such a complex scheduling problem. In addition, we derive a simple super-job scheduling and show that its performance in term of throughput is better than the well-known Heterogeneous Earliest-Finish-Time (HEFT) algorithm.}, booktitle={2011 ieee global telecommunications conference (globecom 2011)}, author={Saovapakhiran, B. and Michailidis, G. and Devetsikiotis, M.}, year={2011} }
 @article{gossett_papapanagiotou_devetsikiotis_2010, title={An apparatus for P2P classification in Netflow traces}, ISSN={["2166-0069"]}, DOI={10.1109/glocomw.2010.5700160}, abstractNote={Application classification from Netflow traces is a challenging process due to the lack of payload information. It is even becoming more challenging when the applications running in the network tend to hide under well known ports, encrypt packets and are distributed. In this paper, we propose an in-the-box apparatus for Netflow classification of Bit Torrent applications. The apparatus includes several device optimizations and requires low processing power. It was developed by reverse engineering the Bit Torrent protocol and by identifying connection patterns. The accuracy of the algorithm reaches high values specifically for Bit Torrent peers that use the DHT protocol.}, journal={2010 IEEE GLOBECOM WORKSHOPS}, author={Gossett, Andrew M. and Papapanagiotou, Ioannis and Devetsikiotis, Michael}, year={2010}, pages={1361–1366} }
 @article{devetsikiotis_granelli_2010, title={Guest Editors' Introduction: Special Issue on Modeling and Simulation of Cross-Layer Interactions in Communication Networks}, volume={21}, ISSN={["1049-3301"]}, DOI={10.1145/1870085.1870086}, abstractNote={Cross-layering represents an important emerging design approach to overcome limitations and lack of flexibility of the layering principle, which is the basis of today’s communication networks. Indeed, in specific scenarios, such as Qualityof-Service provisioning and wireless networks, deeper integration and interaction among different layers is envisioned. Despite the widespread adoption of the general cross-layer design principle, not much attention has been placed on solid, quantitative, systematic study of the system behavior and interactions between different protocols at different layers. In fact, even though several cross-layering architectures are available in the literature, very few works address the problem of providing frameworks for modeling cross-layering interactions and support the proper definition of cross-layering solutions. Quantitative cross-layer formulations and models are still needed to provide effective guidelines on the impact of the design parameters in terms of overall system performance. Simulation-based methods represent indispensable tools to provide further insight in this direction given the analytical intractability of the complex cross-layer system. This special issue of ACM Transactions on Modeling and Computer Simulation (TOMACS) focuses on relevant novel contributions in the development of models for cross-layering interactions and computational solutions. We received several worthy articles that we considered for inclusion in this issue. In addition to the ones appearing in the special issue, certain articles required more extensive revision than could be completed in time for publication of the special issue. Therefore some of these articles will appear in future regular issues of TOMACS. The first article is titled “Steepest-Ascent Constrained Simultaneous Perturbation for Multi-Objective Optimization” and is authored by Daniel W. McClary, Violet R. Syrotiuk, and Murat Kulahci. The authors consider the problem of optimizing multiple responses in which the gradient is known for only one response. They propose a hybrid approach for this problem, called simultaneous perturbation stochastic approximation steepest ascent (SPSA-SA), which is abbreviated as SP(SA)2. SP(SA)2 is an SPSA technique that leverages information about the known gradient to constrain the perturbations used to approximate the others. The authors apply SP(SA)2 to the cross-layer optimization of throughput, packet loss, and end-to-end delay in a mobile adhoc network (MANET), a self-organizing wireless network. The results show that SP(SA)2 achieves higher throughput, lower packet loss, and lower endto-end delay than the steepest ascent, SPSA, and the Nelder-Mead stochastic}, number={1}, journal={ACM TRANSACTIONS ON MODELING AND COMPUTER SIMULATION}, author={Devetsikiotis, Michael and Granelli, Fabrizio}, year={2010}, month={Dec} }
 @article{gavaskar_kallitsis_devetsikiotis_michailidis_montoya_2010, title={Performance Modeling of Virtual Collaborative Environments}, ISSN={["2166-0069"]}, DOI={10.1109/glocomw.2010.5700165}, abstractNote={In this paper, we present a framework for performance modeling of virtual collaborative environments (VCE). Our model could be used as benchmarking tool for assessing the quality of experience of participants in a virtual environment. Our framework is designed to assess Second Life type of environments but could easily be extended to any kind of virtual worlds. We examine the case of users communicating via chatting and voice. We capture the performance for both cases and using response surface methodology techniques we derive a utility function that yields the performance of the examined environment given the available computing and communication resources. We propose a pricing scheme and based on this we formulate optimization problems for optimal resource allocation for VCEs.}, journal={2010 IEEE GLOBECOM WORKSHOPS}, author={Gavaskar, Nilesh and Kallitsis, Michael G. and Devetsikiotis, Michael and Michailidis, George and Montoya, Mitzi}, year={2010}, pages={1383–1387} }
 @article{papapanagiotou_toumpakaris_lee_devetsikiotis_2009, title={A Survey on Next Generation Mobile WiMAX Networks: Objectives, Features and Technical Challenges}, volume={11}, ISSN={["1553-877X"]}, DOI={10.1109/SURV.2009.090402}, abstractNote={In order to meet the requirements of 4G mobile networks targeted by the cellular layer of IMT-advanced, next generation mobile WiMAX devices based on IEEE 802.16m will incorporate sophisticated signal processing, seamless handover functionalities between heterogeneous technologies and advanced mobility mechanisms. This survey provides a description of key projected features of the physical (PHY) and medium access control (MAC) layers of 802.16m, as a major candidate for providing aggregate rates at the range of Gbps to high-speed mobile users. Moreover, a new unified method for simulation modeling, namely the evaluation methodology (EVM), introduced in 802.16m, is also presented.}, number={4}, journal={IEEE COMMUNICATIONS SURVEYS AND TUTORIALS}, author={Papapanagiotou, Ioannis and Toumpakaris, Dimitris and Lee, Jungwon and Devetsikiotis, Michael}, year={2009}, pages={3–18} }
 @article{feng_huang_devetsikiotis_2009, title={FISTE: A Black Box Approach for End-to-End QoS Management}, volume={19}, ISSN={["1558-1195"]}, DOI={10.1145/1596519.1596521}, abstractNote={The goal of traffic engineering is to achieve a target Quality of Service (QoS) while maximizing network utilization. While determining the QoS for end-to-end paths in a network under self-similar traffic models is difficult, end-to-end network performance analysis is still essential in providing QoS to networks such as Virtual Private Networks (VPN) and Peer-to-Peer (P2P) networks. The Fast Importance Sampling based Traffic Engineering (FISTE) approach proposed in this article is a prediction-based approach that maps the ingress traffic levels of a network to the QoS of end-to-end path(s) in the network. Because FISTE is a hybrid of simulation analysis and closed-form analysis, it can treat a complex network as a black box. When we combined Simulated Annealing (SA) with FISTE, the resulting approach can provide a traffic engineering solution so that multiple end-to-end QoS requirements are satisfied while the network resource utilization is maximized. FISTE originated from the concept of Importance Sampling (IS), and our approach differs from the previous Importance Sampling based approaches since this is the first time that IS is applied to multi-queue systems under Fractional Gaussian Noise (FGN) input and traffic engineering.}, number={4}, journal={ACM TRANSACTIONS ON MODELING AND COMPUTER SIMULATION}, author={Feng, Benjamin Zhong Ming and Huang, Changcheng and Devetsikiotis, Michael}, year={2009}, month={Oct} }
 @article{kallitsis_michailidis_devetsikiotis_2009, title={Measurement-based optimal resource allocation for network services with pricing differentiation}, volume={66}, ISSN={["1872-745X"]}, DOI={10.1016/j.peva.2009.03.003}, abstractNote={In this paper, we introduce a model for allocating available resources in service-oriented network, with particular focus on delay sensitive services. The model is based on a pricing scheme for the offered services and also takes into consideration the quality of service requirements of each service class through a probabilistic delay-bound constraint. The proposed policy is dynamic in nature and relies on online measurements of the incoming traffic for adjusting the class allocations. We illustrate its performance and its robustness to various tuning parameters through an extensive simulation study that considers various simulation scenarios including experiments based on real network traces.}, number={9-10}, journal={PERFORMANCE EVALUATION}, author={Kallitsis, M. G. and Michailidis, G. and Devetsikiotis, M.}, year={2009}, month={Sep}, pages={505–523} }
 @article{wang_devetsikiotis_2009, title={Special Issue on Advances in Broadband Wireless Networks}, volume={14}, ISSN={["1383-469X"]}, DOI={10.1007/s11036-009-0159-4}, number={4}, journal={MOBILE NETWORKS & APPLICATIONS}, author={Wang, Wenye and Devetsikiotis, Michael}, year={2009}, month={Aug}, pages={365–367} }
 @article{drummond_fonseca_devetsikiotis_2008, title={A multiobjective fuzzy bandwidth partitioning model for self-sizing networks}, volume={191}, ISSN={["1872-6860"]}, DOI={10.1016/j.ejor.2007.07.014}, abstractNote={The ability to cope with dynamic bandwidth demands is a special feature for Quality of Service provisioning in networks carrying bandwidth hungry applications. This paper introduces a novel approach based on multiobjective fuzzy optimization for dynamic bandwidth allocation. This new approach deals with uncertain bandwidth demands more efficiently than approaches based on Classical Optimization Theory and yet supports Quality of Service commitments.}, number={3}, journal={EUROPEAN JOURNAL OF OPERATIONAL RESEARCH}, author={Drummond, A. C. and Fonseca, N. L. S. and Devetsikiotis, M.}, year={2008}, month={Dec}, pages={1161–1174} }
 @article{hsu_devetsikiotis_2008, title={An adaptive approach to accelerated evaluation of highly available services}, volume={18}, ISSN={["1558-1195"]}, DOI={10.1145/1315575.1315576}, abstractNote={
            We motivate and describe improved fast simulation techniques for the accelerated performance evaluation of highly available services. In systems that provide such services, service unavailability events are rare due to a low component failure rate or high resource capacity. Using traditional Monte Carlo simulation to evaluate such services requires a large amount of runtime. Importance sampling (IS) has been applied to certain instances of such systems, focusing on single-class and/or homogeneous resource demands. In this article, we formulate highly available services as multiresource losstype systems, and we present two IS methods for fast simulation, extending to multiple classes and nonhomogeneous resource demands. First, for the cases in which component failure rates are small, we prove that
            static
            IS using the Standard Clock (S-ISSC) method exhibits the bounded relative error (BRE) property. Second, for estimating failure probabilities due to large capacity or fast service in systems that have nonrare component failure rates, we propose adaptive ISSC (A-ISSC), which estimates the relative probability of reaching each possible state of system failure in every step of the simulation. Using A-ISSC, IS methods which are proven to be efficient can be extended to
            multidimensional
            cases, while still retaining a very favorable performance, as supported by our validation experiments.
          }, number={1}, journal={ACM TRANSACTIONS ON MODELING AND COMPUTER SIMULATION}, author={Hsu, Chih-Chieh and Devetsikiotis, Michael}, year={2008} }
 @article{hui_devetsikiotis_2008, title={The use of metamodeling for VoIP over WiFi capacity evaluation}, volume={7}, ISSN={["1558-2248"]}, DOI={10.1109/TWC.2008.05754}, abstractNote={The increasing popularity of wireless fidelity (Wi-Fi) networks at home, in public areas and in the enterprise motivates extensive modeling and analysis of their performance measures, such as network capacity and quality of service (QoS) capabilities. Some of the easier performance problems can be solved by analytical modeling methods, but most of the complicated ones, involving several design parameters from multiple layers, can only be answered through simulation studies that are typically implicit and less suitable for design and optimization. Hence, we believe it is crucial to obtain explicit mathematic models, that are effective in representing system behavior and a basis for performance optimization. Here, we first advocate the application of formal empirical modeling techniques to performance studies of Wi-Fi networks, in order to find usable, if approximate, closed-form mathematical models. Subsequently, by applying these metamodeling techniques, we perform a case study with very useful results: our VoWiFi (voice over Wi-Fi) admission capacity metamodel gives a much tighter bound than those existing in the literature and leads to a more effective admission control scheme. Our work, therefore, points out a new direction for future performance studies of Wi-Fi networks.}, number={1}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Hui, Jie and Devetsikiotis, Michael}, year={2008}, month={Jan}, pages={1–5} }
 @inproceedings{kallitsis_michailidis_devetsikiotis_2007, title={Pricing and measurement-based optimal resource allocation in next generation network services}, booktitle={2007 IEEE Globecom Workshops, Proceedings}, author={Kallitsis, M. G. and Michailidis, G. and Devetsikiotis, M.}, year={2007}, pages={189–194} }
 @inproceedings{kallitsis_michailidis_devetsikiotis_2007, title={Pricing and optimal resource allocation in next generation network services}, booktitle={2007 IEEE Sarnoff Symposium}, author={Kallitsis, M. G. and Michailidis, G. and Devetsikiotis, M.}, year={2007}, pages={457–461} }
 @article{nalatwad_devetslkiotis_2007, title={Wavelet-based neighborhood control for self-sizing networks}, volume={83}, ISSN={["1741-3133"]}, DOI={10.1177/0037549707081187}, abstractNote={ The exponential growth of the Internet has turned it into a multiservice complex network of heterogeneous elements with dynamically changing traffic conditions. To regulate such a large scale network it is necessary to place intelligence in the nodes and find simple distributed rules and strategies that can produce meaningful and consistent behavior. These control mechanisms must be adaptive to effectively respond to continually changing network conditions. A “self-sizing” network can allocate link/switch capacity automatically and adaptively using online traffic data. Such adaptive, distributed, localized mechanisms are crucial to provide a scalable solution for controlling large, complex networks. In this paper, we propose a new, distributed self-sizing framework for locally controlled networks, which can support the stringent requirements of real-time applications in the Internet. Our unified and critical study of online resource allocation algorithms of two different classical approaches, led us to the use of adaptive multi-resolution decomposition (“wavelet”) algorithms. Our results show that by performing online resource allocation at each node based on their local knowledge, we can achieve considerable bandwidth savings and also satisfy QoS at the packet level. In our novel “neighborhood control” technique, we establish that by increasing the knowledge of some nodes so that higher self-sizing gains can be attained. }, number={3}, journal={SIMULATION-TRANSACTIONS OF THE SOCIETY FOR MODELING AND SIMULATION INTERNATIONAL}, author={Nalatwad, Srikant and Devetslkiotis, Michael}, year={2007}, month={Mar}, pages={229–244} }
 @inproceedings{callaway_rodriguez_devetsikiotis_cuomo_2006, title={Challenges in service-oriented networking}, DOI={10.1109/glocom.2006.419}, abstractNote={We believe that application-aware networks will be a core component in the development and deployment of emerging network services. However, previous attempts at enabling application-awareness in the network have failed due to issues with security, resource allocation, and cost of deployment. The emergence of the Extensible Markup Language (XML), an open standard that enables data interoperability, along with advances in hardware, software, and networking technologies, serves as the catalyst for the development of service-oriented networking (SON). SON enables network components to become application-aware, so that they are able to understand data encoded in XML and act upon that data intelligently to make routing decisions, enforce QoS or security policies, or transform the data into an alternate representation. This paper describes the motivation behind service-oriented networking, the potential benefits of introducing application-aware network devices into service-oriented architectures, and discusses research challenges in the development of SON-enabled network appliances.}, booktitle={Globecom 2006 - 2006 ieee global telecommunications conference}, author={Callaway, R. D. and Rodriguez, A. and Devetsikiotis, M. and Cuomo, G.}, year={2006} }
 @inproceedings{hui_devetsikiotis_2006, title={Metamodeling of Wi-Fi Performance}, DOI={10.1109/icc.2006.254849}, abstractNote={The increasing popularity of Wireless Fidelity (Wi-Fi) networks at home, in public areas and in the enterprise motivates extensive modeling and analysis of their performance measures, such as network capacity, resource requirements and quality of service (QoS) capabilities. Some of the easier performance problems can be solved by analytical modeling methods, but most of the complicated ones, involving too many factors from multiple layers, can only be answered through validated simulation models. However, an explicit mathematic model is always the most effective way to represent the system behavior and the most convenient basis for performance optimization. Here, we first advocate the application of metamodeling techniques to performance studies of Wi-Fi networks, in order to find usable, if approximate, closed-form mathematical models. Subsequently, we formulate a general metamodeling framework for Wi-Fi networks. Our results in two relevant case studies, after applying this framework, support the validity of our metamodeling methodology: our capacity metamodel for 802.11 Distributed Coordination Function (DCF) is validated by a well-known analytical model and displays an interesting log-linear relationship between capacity and number of users; our voice over Wi-Fi admission capacity metamodel gives a much tighter bound than bounds existing in the literature and composes a more practical admission control scheme. Our work, therefore, points out a new direction for future performance studies of Wi-Fi networks.}, booktitle={2006 ieee international conference on communications, vols 1-12}, author={Hui, J. and Devetsikiotis, M.}, year={2006}, pages={527–534} }
 @article{xu_michailidis_devetsikiotis_2006, title={Profit-oriented resource allocation using online scheduling in flexible heterogeneous networks}, volume={31}, ISSN={["1572-9451"]}, DOI={10.1007/s11235-006-6525-7}, abstractNote={In this paper, we discuss a generalized measurement-based adaptive scheduling framework for dynamic resource allocation in flexible heterogeneous networks, in order to ensure efficient service level performance under inherently variable traffic conditions. We formulate our generalized optimization model based on the notion of a “profit center” with an arbitrary number of service classes, nonlinear revenue and cost functions and general performance constraints. Subsequently, and under the assumption of a linear pricing model and average queue delay requirements, we develop a fast, low complexity algorithm for online dynamic resource allocation, and examine its properties. Finally, the proposed scheme is validated through an extensive simulation study.}, number={2-3}, journal={TELECOMMUNICATION SYSTEMS}, author={Xu, P and Michailidis, G and Devetsikiotis, M}, year={2006}, month={Mar}, pages={289–303} }
 @article{oruganti_devetsikiotis_2005, title={A  study of robust Active Queue Management schemes for correlated traffic}, volume={28}, number={1}, journal={Computer Communications}, author={Oruganti, S. S. and Devetsikiotis, M.}, year={2005}, pages={11-} }
 @article{hui_devetsikiotis_2005, title={A unified model for the performance analysis of IEEE 802.11e EDCA}, volume={53}, ISSN={["1558-0857"]}, DOI={10.1109/tcomm.2005.855013}, abstractNote={Rapid deployment of IEEE 802.11 wireless local area networks (WLANs) and their increasing quality of service (QoS) requirements motivate extensive performance evaluations of the upcoming 802.11e QoS-aware enhanced distributed coordination function (EDCA). Most of the analytical studies up-to-date have been based on one of the three major performance models in legacy distributed coordination function analysis, requiring a large degree of complexity in solving multidimensional Markov chains. Here, we expose the common guiding principle behind these three seemingly different models. Subsequently, by abstracting, unifying, and extending this common principle, we propose a new unified performance model and analysis method to study the saturation throughput and delay performance of EDCA, under the assumption of a finite number of stations and ideal channel conditions in a single-hop WLAN. This unified model combines the strengths of all three models, and thus, is easy to understand and apply; on the other hand, it helps increase the understanding of the existing performance analysis. Despite its appealing simplicity, our unified model and analysis are validated very well by simulation results. Ultimately, by means of the proposed model, we are able to precisely evaluate the differentiation effects of EDCA parameters on WLAN performance in very broad settings, a feature which is essential for network design.}, number={9}, journal={IEEE TRANSACTIONS ON COMMUNICATIONS}, author={Hui, J and Devetsikiotis, M}, year={2005}, month={Sep}, pages={1498–1510} }
 @article{devetsikiotis_fonseca_2005, title={Modeling network traffic with long range dependence: characterization, visualization and tools}, volume={48}, ISSN={["1872-7069"]}, DOI={10.1016/j.comnet.2005.01.001}, number={3}, journal={COMPUTER NETWORKS}, author={Devetsikiotis, M and Fonseca, NLS}, year={2005}, month={Jun}, pages={289–291} }
 @article{sheikh_wan_alakhdhar_lambadaris_devetsikiotis_2004, title={Performance analysis of buffered R-ALOHA systems using tagged user approach}, volume={27}, ISSN={["1084-8045"]}, DOI={10.1016/j.jnca.2003.11.002}, abstractNote={In this paper, R-ALOHA systems with propagation delay, finite buffer capacity and finite user population are analyzed using Tagged User Approach. The system throughput, message response time, message delay-time distribution and message blocking probability are obtained. It is assumed that each message consists of a random number of packets with a general distribution, and each user have a finite buffer capacity. To maintain the fairness to all users, it is assumed that each message in the buffer is transmitted independently that is, a user has to release the reserved slot after finishing the transmission of a message even if it has more messages waiting in the buffer. The analysis can be extended to R-ALOHA systems with infinite buffer capacity straightforwardly. The accuracy of the analysis is verified by simulations.}, number={3}, journal={JOURNAL OF NETWORK AND COMPUTER APPLICATIONS}, author={Sheikh, AUH and Wan, T and Alakhdhar, SZ and Lambadaris, I and Devetsikiotis, M}, year={2004}, month={Aug}, pages={131–150} }
 @article{laskin_lambadaris_harmantzis_devetsikiotis_2002, title={Fractional Levy motion and its application to network traffic modeling}, volume={40}, ISSN={["1872-7069"]}, DOI={10.1016/s1389-1286(02)00300-6}, abstractNote={We introduce a general non-Gaussian, self-similar, stochastic process called the fractional Levy motion (fLm). We formally expand the family of traditional fractal network traffic models, by including the fLm process. The main findings are the probability density function of the fLm process, several scaling results related to a single-server infinite buffer queue fed by fLm traffic, e.g., scaling of the queue length, and its distribution, scaling of the queuing delay when independent fLm streams are multiplexed, and an asymptotic lower bound for the probability of overflow (decreases hyperbolically as a function of the buffer size).}, number={3}, journal={COMPUTER NETWORKS}, author={Laskin, N and Lambadaris, I and Harmantzis, FC and Devetsikiotis, M}, year={2002}, month={Oct}, pages={363–375} }