Theofanis Orphanoudakis

Dr. Theofanis Orphanoudakis

orcid

Research Focus & Metrics

Academic Career Length

23Years (2004-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 February 2023 in Sensors
Verified
Journal Article
Open access
PDF file
AFAnastasios Fanariotis
Anastasios Fanariotis
TOTheofanis Orphanoudakis
Theofanis Orphanoudakis
KKKonstantinos Kotrotsios
Konstantinos Kotrotsios
VFVassilis Fotopoulos
Vassilis Fotopoulos
Georgios KeramidasGeorgios Keramidas
Georgios Keramidas
Panagiotis KarkazisPanagiotis Karkazis
Panagiotis Karkazis
Computing has undergone a significant transformation over the past two decades, shifting from a machine-based approach to a human-centric, virtually invisible service known as ubiquitous or pervasive computing. This change has been achieved by incorporating small embedded devices into a larger computational system, connected through networking and referred to as edge devices. When these devices are also connected to the Internet, they are generally named Internet-of-Thing (IoT) devices. Developing Machine Learning (ML) algorithms on these types of devices allows them to provide Artificial Intelligence (AI) inference functions such as computer vision, pattern recognition, etc. However, this capability is severely limited by the device’s resource scarcity. Embedded devices have limited computational and power resources available while they must maintain a high degree of autonomy. While there are several published studies that address the computational weakness of these small systems-mostly through optimization and compression of neural networks- they often neglect the power consumption and efficiency implications of these techniques. This study presents power efficiency experimental results from the application of well-known and proven optimization methods using a set of well-known ML models. The results are presented in a meaningful manner considering the “real world” functionality of devices and the provided results are compared with the basic “idle” power consumption of each of the selected systems. Two different systems with completely different architectures and capabilities were used providing us with results that led to interesting conclusions related to the power efficiency of each architecture.

12 March 2024 in Information
Verified
Journal Article
Open access
PDF file
AFAnastasios Fanariotis
Anastasios Fanariotis
TOTheofanis Orphanoudakis
Theofanis Orphanoudakis
VFVassilis Fotopoulos
Vassilis Fotopoulos
Having as a main objective the exploration of power efficiency of microcontrollers running machine learning models, this manuscript contrasts the performance of two types of state-of-the-art microcontrollers, namely ESP32 with an LX6 core and ESP32-S3 with an LX7 core, focusing on the impact of process acceleration technologies like cache memory and vectoring. The research employs experimental methods, where identical machine learning models are run on both microcontrollers under varying conditions, with particular attention to cache optimization and vector instruction utilization. Results indicate a notable difference in power efficiency between the two microcontrollers, directly linked to their respective process acceleration capabilities. The study concludes that while both microcontrollers show efficacy in running machine learning models, ESP32-S3 with an LX7 core demonstrates superior power efficiency, attributable to its advanced vector instruction set and optimized cache memory usage. These findings provide valuable insights for the design of power-efficient embedded systems supporting machine learning for a variety of applications, including IoT and wearable devices, ambient intelligence, and edge computing and pave the way for future research in optimizing machine learning models for low-power, embedded environments.

1 February 2024 in Sensors
Verified
Journal Article
Open access
PDF file
TKTHEODOROS KARACHALIOS
THEODOROS KARACHALIOS
PMPanagiotis Moschos
Panagiotis Moschos
TOTheofanis Orphanoudakis
Theofanis Orphanoudakis
Maritime emissions contribute significantly to global pollution, necessitating accurate and efficient monitoring methods. Traditional methods for tracking ship emissions often face limitations in real-time data accuracy, with wind measurement being a critical yet challenging aspect. This paper introduces an innovative mission planner module for unmanned aerial vehicles (UAVs) that leverages onboard wind sensing capabilities to enhance maritime emission monitoring. The module’s primary objective is to assist operators in making informed decisions by providing real-time wind data overlays, thus optimizing flight paths and data collection efficiency. Our experimental setup involves the testing of the module in simulated maritime environments, demonstrating its efficacy in varying wind conditions. The real-time wind data overlays provided by the module enable UAV operators to adjust their flight paths dynamically, reducing unnecessary power expenditure and mitigating the risks associated with low-battery scenarios, especially in challenging maritime conditions. This paper presents the implementation of real-time wind data overlays on an open-source state-of-the-art mission planner as a C# plugin that is seamlessly integrated into the user interface. The factors that affect performance, in terms of communication overheads and real-time operation, are identified and discussed. The operation of the module is evaluated in terms of functional integration and real-time visual representation of wind measurements, and the enhanced situational awareness that it can offer to mission controllers is demonstrated. Beyond presenting a novel application of UAV technology in environmental monitoring, we also provide an extensive discussion of how this work will be extended in the context of complete aerial environmental inspection missions and the future directions in research within the field that can potentially lead to the modernization of maritime emission monitoring practices.

8 November 2004 in IEEE Micro
Verified
Journal Article
Closed access
Ioannis PapaefstathiouIoannis Papaefstathiou
Ioannis Papaefstathiou
SPS. Perissakis
S. Perissakis
TOTheofanis Orphanoudakis
Theofanis Orphanoudakis
NNN.A. Nikolaou
N.A. Nikolaou
GKG. Komaros
G. Komaros
KVK. Vlachos
K. Vlachos
As the telecommunications industry recovers from the severe downturn of recent years, data traffic continues to exhibit a rate of increase that outpaces advances in VLSI technology. Therefore, lowering overall system cost at network processing nodes and maximizing network utilization - hence revenues - remain extremely important objectives. To address these issues, new semiconductor devices called network processing units (NPUs) have emerged. They are optimized to provide programmable processing of protocol data units (PDUs) in networks with diverse requirements while efficiently supporting current and emerging protocols and services. NPUs promise to deliver an ASICs speed with a CPU's programmability, thus augmenting the capacity and features of network nodes that forward and manipulate data traffic. The Programmable Protocol Processor (PRO3) system reduces the overhead incurred by common "BRUTE-FORCE" architectures by using the least-required hardware resources for certain common well-defined tasks.

12 January 2022 in Sensors
Verified
Journal Article
Open access
PDF file
KKKonstantinos Kotrotsios
Konstantinos Kotrotsios
AFAnastasios Fanariotis
Anastasios Fanariotis
HLHelen-Catherine Leligou
Helen-Catherine Leligou
TOTheofanis Orphanoudakis
Theofanis Orphanoudakis
In this paper, we present the results of a performance evaluation and optimization process of an indoor positioning system (IPS) designed to operate on portable as well as miniaturized embedded systems. The proposed method uses the Received Signal Strength Indicator (RSSI) values from multiple Bluetooth Low-Energy (BLE) beacons scattered around interior spaces. The beacon signals were received from the user devices and processed through an RSSI filter and a group of machine learning (ML) models, in an arrangement of one model per detected node. Finally, a multilateration problem was solved using as an input the inferred distances from the advertising nodes and returning the final position approximation. In this work, we first presented the evaluation of different ML models for inferring the distance between the devices and the installed beacons by applying different optimization algorithms. Then, we presented model reduction methods to implement the optimized algorithm on the embedded system by appropriately adapting it to its constraint resources and compared the results, demonstrating the efficiency of the proposed method.

31 January 2023 in IJCCS (Indonesian Journal of Computing and Cybernetics Systems)
Verified
Journal Article
Open access
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RSRisna Sari
Risna Sari
KKKusrini Kusrini
Kusrini Kusrini
THTonny Hidayat
Tonny Hidayat
TOTheofanis Orphanoudakis
Theofanis Orphanoudakis
As cryptocurrencies develop, it cannot be denied that crypto prices are volatile. One of the influencing factors is the increasing volume of transactions which attracts the interest of researchers to conduct research in developing coin price predictions from cryptocurrencies. The method, algorithm and amount of data affect the prediction results. In this study, prediction modelling will be carried out using the LSTM method and short-term data. This study will conduct two experiments using the simple LSTM method and utilising multivariate time series with LSTM. The smallest predicted value is obtained using an 80/20 data allocation distribution scenario, input layer LSTM = 360, Epoch = 500, a Solana coin with RMSE = 0.111, R2 = 0.9962. It can be interpreted that short-term data can be used in making predictive models. Still, special attention needs to be paid to the characteristics of the dataset used and the modelling methodology, and it is hoped that the results of this study can be used in further research.