Papers by Christophoros Christophorou
ML-Aided Dynamic Clustering and Classification of UEs as VBs in D2D Communication Networks
2023 International Conference on Wireless Communications Signal Processing and Networking (WiSPNET)
International Journal of Information Security
Advancements in the field of wireless and mobile communication motivate academia, industry, and s... more Advancements in the field of wireless and mobile communication motivate academia, industry, and standardization organizations to explore new technologies to improve overall efficiency, spectrum utilization, power consumption, and security. One of the most important technologies proposed for short-range communications which will play a key role in 5G wireless networks is Device-to-Device (D2D) Communications. D2D communication enables direct communication between two devices when they are in close proximity without requiring the help of a fixed infrastructure like Base This research is part of a project that has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement Nº739578 and the government of the Republic of Cyprus through the Directorate General for European Programmes, Coordination and Development.
A distributed AI/ML framework for D2D Transmission Mode Selection in 5G and beyond
Computer Networks
In this paper we build on the Distributed Artificial Intelligence (DAI) Framework, which makes us... more In this paper we build on the Distributed Artificial Intelligence (DAI) Framework, which makes use of Belief-Desire-Intention extended (BDIx) agents residing on Device-to-Device (D2D) Mobile Devices in order to establish D2D communication in an efficient, distributed, autonomous and flexible way. To demonstrate the potentials of this framework, in this work we focus on D2D Transmission Mode Selection in 5G. Specifically, we build on our previous work and develop an enhanced version of DAIS, a specific plan executed by the BDIx agents, for selecting the D2D Transmission mode that the D2D Devices will operate, aiming to offer improved Spectral Efficiency (SE) and Power Consumption (PC). To set a benchmark and allow for a fairer comparison we also enhance the Distributed Sum Rate (DSR), a distributed algorithmic approach that focuses on maximizing the aggregated data rate of all the links established in the network, with similar functionality as DAIS. Furthermore, an extensive comparative evaluation of the enhanced DAIS and DSR with a number of unsupervised ML clustering approaches adapted for D2D Communication(i.e., GMEANS, Fuzzy ART, MEC, and DBSCAN) is provided. Specifically, for each approach the following have been collected and compared: QoE and QoS Fairness, SE and PC achieved, efficiency of clusters created, signalling overhead caused (i.e., volume of messages exchanged), time execution delay, D2D Effectiveness, D2D Stability and D2D Productivity. Based on the insight gained into the performance of the enhanced DAIS, DSR and the unsupervised ML techniques, we discuss performance gain trade-offs in terms of SE and PC versus signaling overhead and control delay in responding to changes.
This paper investigates the preferences and the expectations of endusers related to the appearanc... more This paper investigates the preferences and the expectations of endusers related to the appearance and personality of a Virtual Support Partner (VSP); namely an Embodied Conversational Agent (ECA) that attends to the daily activities of the seniors. The results presented in this paper, reveal that end users are in favor of an emphatic, emotional and friendly companion, preferably represented by a human-like or an animal-like body, that provides to them both social support and assistance through a guiding attitude.
International Journal of Information Security, Oct 4, 2022
Advancements in the field of wireless and mobile communication motivate academia, industry, and s... more Advancements in the field of wireless and mobile communication motivate academia, industry, and standardization organizations to explore new technologies to improve overall efficiency, spectrum utilization, power consumption, and security. One of the most important technologies proposed for short-range communications which will play a key role in 5G wireless networks is Device-to-Device (D2D) Communications. D2D communication enables direct communication between two devices when they are in close proximity without requiring the help of a fixed infrastructure like Base This research is part of a project that has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement Nº739578 and the government of the Republic of Cyprus through the Directorate General for European Programmes, Coordination and Development.
A novel Distributed AI framework with ML for D2D communication in 5G/6G networks
Computer Networks
Inspired by the adoption of Artificial Intelligence (AI) and Machine Learning (ML) approaches in ... more Inspired by the adoption of Artificial Intelligence (AI) and Machine Learning (ML) approaches in 5G and 6G networks, in this paper we propose a novel ML based Distributed AI (DAI) framework able to attain the ambitious goals set for emerging 5G/6G networks. The novelty of the DAI framework is that it is implemented in an autonomous, dynamic and flexible fashion, utilising Belief Desire Intention (BDI) agents, extended with ML capabilities, which reside on the mobile devices (User Equipment). We refer to these as BDIx agents. This provides a component-based framework (likened to LEGO-based building blocks), which can build on and utilise execution plans, by composing and arranging ML techniques in flexible ways within the framework, in order to achieve the desired goals. More specifically, we form a modular BDIx agent at a multi-agent system (MAS), integrated with Fuzzy Logic for the perception/cognitive part of the agents. By exploiting the capabilities of the BDIx agents in our DAI framework, we allow mobile devices to intercommunicate and cooperate in an autonomous manner, thus offering a number of attractive features, including improved performance in terms of network control execution time and message exchange, fast response in handling dynamic aspects in the network, self-organizing network functionalities, and a framework that can act as the glue platform in employing one or more intelligent approaches to tackle the diverse 5G/6G technical requirements. To demonstrate the potential of the DAI framework we focus on Device to Device (D2D) communication and illustrate its flexibility in addressing diverse D2D challenges. Through example Plan Libraries and enhanced metrics, we outline DAI implementation specifics to achieve a number of identified 5G/6G D2D requirements. To embed the concept further, the specific problem of D2D transmission mode selection is expanded upon, from problem description to solution approach (DAIS) and implementation specifics, and hence comparatively evaluate over other approaches (i.e., Unsupervised learning ML techniques, centralised control techniques, random techniques). The results demonstrated that DAIS provides, among other performance metrics, improved mobile network Spectral Efficiency (SE) and Power Consumption (PC), better and more efficient cluster formation and reduced control decision delay.
A Two-Stage Machine Learning Approach for 5g Mobile Network Augmentation Through Dynamic Selection and Activation of Ue-Vbss
SSRN Electronic Journal, 2022
Dynamic selection of Virtual Small Base Station in 5G Ultra-Dense Network using Initializing Matching Connection Algorithm
2019 IEEE International Conference on Advanced Networks and Telecommunications Systems (ANTS), 2019
The 5G cellular network is the new generation of mobile networks that will play a key role in sup... more The 5G cellular network is the new generation of mobile networks that will play a key role in supporting current and forthcoming demands for wireless access by various devices in an Ultradense network. Small Cells is the most encouraging technological feature of the 5G. This paper builds on the idea of the User Equipment-based Virtual Base Station (UE-VBS) concept that enhances the Smartphones of the general population into Virtual Small Base Stations, referred as eligible-UEs, and embeds them in the Mobile Network Infrastructure. Part of these eligible-UEs are activated on the-fly into UE-VBSs to support the network infrastructure in stressful or overloaded situations in Ultra-dense 5G networks. To process the initial connection between the client UEs and eligible-UEs, the Initializing Matching Connection Algorithm (IMCA) is implemented based on the SINR preference of the client UEs to eligible-UEs. The IMCA algorithm results in the formation of clusters. The proposed Virtual Small Cell (VSC) activation algorithm optimizes the clusters based on the upper and lower bound constraints on the size of the cluster, which results in the formation of UE-VBS. The IMCA and VSC activation algorithms are implemented in MATLAB, and the results are validated using the NS3 networking simulator.
IEEE Access
This paper focuses on D2D communication for 5G/6G in dynamic environments where the D2D network t... more This paper focuses on D2D communication for 5G/6G in dynamic environments where the D2D network topology changes through time due to D2D Devices' mobility. Specifically, we consider a scenario within the coverage area of a Base Station (BS) serving a number of User Devices (UEs), with variations in speed and direction causing changes in the D2D network topology, either via direct connections or via D2D single-hop or D2D Multi-hop paths. Based on this scenario, we formulate a problem aiming to maximise the total Spectral Efficiency (SE) whilst minimising the total Power Consumption (PC), by selecting the best transmission mode that the D2D devices will operate. In order to address the aforementioned problem, the Distributed Artificial Intelligence Solution (DAIS) plan proposed in our earlier work and designed for static environments is extended to consider the mobility (i.e., speed, direction and indirectly link distance change) of the D2D Device, targeting the dynamic creation of stable and efficient clusters and good backhauling links towards the gateway. The enhanced DAIS performance is comparatively evaluated in terms of SE and PC against selected variations in UE speed and direction, changes in the link Transmission Power (TP), and an increase in the number of Devices in the D2D network. Overall, the results obtained demonstrated superior performance of enhanced DAIS over all the other related investigated approaches (i.e., Distributed Sum Rate (DSR), Single Hop Relay Approach (SHRA), Distributed Random (DR)), in terms of Spectral Efficiency (SE) and Power Consumption (PC). Also, the ability of enhanced DAIS to react and adapt quickly and efficiently to D2D network topology changes, with reduced signalling overhead and control delay in responding to changes, shows that it is a well-poised approach to be used in a Dynamic D2D Environment.
Detection of DDoS attacks in D2D communications using machine learning approach
Computer Communications
Using UE-VBS for dynamic virtual small cells deployment and backhauling in 5G Ultra-Dense networks
Computer Networks
Avatar-based systems provide an intuitive way of interacting with users in the context of Ambient... more Avatar-based systems provide an intuitive way of interacting with users in the context of Ambient Assisted Living (AAL). These systems are typically supported by a diverse set of services for, e.g, social daily activities, leisure, education and safety. This paper studies the importance of specific services for two organizations, namely MRPS in Geneva, Switzerland and ORBIS in Sittard, Netherlands. Based on this study, we present the design of a backend framework that supports Avatar interaction by means of a comprehensive set of services for safe and independent living.
Specification, Development, and Verification
Recent years, from about the early 2000s, have been characterized by global broadband penetration... more Recent years, from about the early 2000s, have been characterized by global broadband penetration, Fixed-Mobile-Convergence, Triple Play, and content provisioning over All-IP multimedia networks. Increasing demands in group-based multimedia sessions and market forces are fuelling the design of the future Internet, which is expected to fundamentally change the networking landscape in the upcoming years. Context, understood as sensed information that changes over time, has already led, to some extent, to service adaptation in terms of recognizing and using simple context, e.g. location. Context may also include network or personal state, location, or weather. To allow for session adaptation, it is important to use network and user context to enhance the existing service, keeping the user satisfied throughout the session.
Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2010
The increase of networking complexity requires the design of new performance optimization schemes... more The increase of networking complexity requires the design of new performance optimization schemes for delivering different types of sessions to users under different conditions. In this scope, special attention is given to multi-homed environments, where mobile devices cross areas with overlapping access technologies (Wi-Fi, 3G, WiMax). In such scenario, efficient multiparty delivery depends upon the grouping operation (creation of a set of users to receive a given session), which must be done based on several parameters. We propose sub-grouping of content-based service groups, so that the same service session can be delivered using different codings of the same content, to adapt to the current network, users, session and environment context. The context-aware information is used to improve the sub-grouping process. This paper aims to describe these sub-grouping techniques, in particular how they improve network performance and user experience in the future Internet, in the scope of cognitive autonomic networks.
Proceedings of the 5th International Mobile Multimedia Communications Conference, 2009
Telecommunication and Internet services are constantly subject to changes, seeking customer's sat... more Telecommunication and Internet services are constantly subject to changes, seeking customer's satisfaction. Enriching services with innovative approaches such as context-aware, mobile, adaptable and interactive mechanisms, enables users to experience personalized services seamlessly across different technologies. Aiming at evolving mobile multimedia multicasting to exploit the increasing integration of mobile devices with our everyday physical world, a context-aware multiparty delivery needs to research into two important frameworks: context detection and distribution and context-aware multiparty networking, encompassing adaptations at the session, transport, and network layers. The paper diverges into the second by focusing on the user perceived Quality of Experience and efficient network support of real-time group communications, allowing dynamic adaptation of the multiparty delivery, group communications optimization and maximization of group member's overall satisfaction.
2009 International Conference on Ultra Modern Telecommunications & Workshops, 2009
Future networks are envisioned to satisfy the user needs and improve their quality of experience.... more Future networks are envisioned to satisfy the user needs and improve their quality of experience. This requires the networks to support context-aware information, where context of the user, session, network and environment will greatly influence the way the session is delivered: new approaches are required to deal with the overall context information and network reaction to constantly context changes. This paper presents a context-aware architecture that provides delivery of multiparty services in heterogeneous and mobile environments. The architecture, its elements and functionalities are described through a specific application to a context-driven use case scenario. We show that this architecture is able to provide personalized and multiparty services to the users, addressing their characteristics and preferences, and optimizing network support while mobility and heterogeneous environments are in place.
Selection of UE-based Virtual Small Cell Base Stations using Affinity Propagation Clustering
2018 14th International Wireless Communications & Mobile Computing Conference (IWCMC), 2018
5G will require a number of Key Technological Components to meet its very ambitious goals, includ... more 5G will require a number of Key Technological Components to meet its very ambitious goals, including Heterogeneous Networks a nd Small Cells. The Dense Deployme nt of Small Cell Base Stations (SBSs) will play a major role as they can be installed in a more targeted manner to relieve traffic in hot spot areas, increase coverage, and spectral efficiency. However, the current deployment of the SBS is static (examples include Femto, Pico, and Nano cells), normally deployed on demand around hotspots. In the scenario of unpredictable crowd movement, these static deployment of small cell can be inefficient with high CAPEX and OPEX. This paper focuses on the scenario where UE-based Virtual Small Cell Base Stations (UE-VBSs) can be dynamically selected among UEs to deal effectively with the non-stationary, non-uniform distribution of mobile traffic with respect to time and space domain. To implement this concept, we propose an efficient clustering technique (Affinity Propagation Clustering) to select the best set of UE-VBSs to supplement an overlay loaded SBS. Simulative evaluation highlights salient features of the technique, as well as its limitations with regard to scalability. Further, we discuss the modification of the algorithm according to our objec tive sc enario focusing on red ucing the message passing procedure to and from only a number of eligible UE-VBSs using the power received by a UE from the eligible UE-VBSs as a parameter. The algorithm is implemented and evaluated in MATLAB and, also validated using NS3 simulator.
With MBMS, a mobile Terminal (MT) that is on the move and receive an MBMS service may have to han... more With MBMS, a mobile Terminal (MT) that is on the move and receive an MBMS service may have to handover from a Common to a Dedicated Channel when crossing the cell’s edge. In previous work, we highlighted the possible inefficiencies which might arise if the existing 3GPP handover control approach is adopted to execute these types of handovers and proposed a specific MBMS handover control approach that compensated for them. This approach, although effective in terms of capacity and QoS, was not very viable. Thus in this paper, using a different approach, we enhance previous work in order to address its deficiencies and make the whole solution practical. The performance evaluation showed that our enhanced proposed approach even with the enhancements made simplifying the whole handover procedure, still outperforms the existing 3GPP handover control approach in terms of capacity and QoS efficiency.
Power Counting for Optimized Capacity in MBMS Enabled UTRAN
MBMS bearer services can be provided in each cell by either Point-to-Point or Point-to-Multipoint... more MBMS bearer services can be provided in each cell by either Point-to-Point or Point-to-Multipoint transmission mode but for efficiency a decision has to be made between the two approaches. Initially, the fundamental criterion used to make this decision was the number of MBMS users in a cell (UE Counting). In this paper we extend our previous work, which proposed the power transmitted by the Base Station (BS) as the channel switching criterion (Power Counting). We evaluate our approach and illustrate its capability to dynamically adapt to continuously varying cell conditions by selecting the transmission mode in a more efficient way, preserving in this way the network’s resources. At the same time we demonstrate the limitations of the conventional approach, in terms of radio resource efficiency. We show that by having the power used by the BS as the limiting factor we achieve optimized capacity during the transmission of MBMS bearer services in UTRAN.
Handover Control in MBMS Enabled 3G Mobile Cellular Networks
– Handover Control in a cellular infrastructure aims to provide continuity of mobile services to ... more – Handover Control in a cellular infrastructure aims to provide continuity of mobile services to a user traveling over cell boundaries. Using the existing Handover Control algorithm in 3rd Generation (3G) Mobile Cellular Networks supporting multicast and broadcast multimedia services (MBMS) might prove inefficient due to the new aspects introduced. In this paper we investigate and highlight the inefficiencies caused when a PMM (Packet Mobility Management)-Connected mobile user is receiving an MBMS service and performs a handover using the existing handover approach. We therefore propose and evaluate a specific MBMS handover approach to address the issues highlighted in our analysis.
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Papers by Christophoros Christophorou