Papers by Angelos Michalas
ArXiv, 2021
The scenario of an uplink two-user non-orthogonalmultiple access (NOMA) communication system is a... more The scenario of an uplink two-user non-orthogonalmultiple access (NOMA) communication system is analytically studied when it operates in the short packet transmission regime. The considered users support mobility and each is equipped with a single antenna, while they directly communicate with a multi-antenna base station. Power-domain NOMA is adopted for the signal transmission as well as the successive interference cancellation approach is performed at the receiver for decoding. The packet error rate (PER) is obtained in simple closed formulae under independent Rayleigh faded channels and for arbitrary user mobility profiles. The practical time variation and correlation of the channels is also considered. Moreover, useful engineering insights are manifested in short transmission time intervals, which define a suitable setup for the forthcoming ultra-reliable and low latency communication systems. Finally, it turns out that the optimal NOMA power allocation can be computed in a stra...
2018 Global Information Infrastructure and Networking Symposium (GIIS)
Video streaming currently accounts for the majority of Internet traffic. One factor that enables ... more Video streaming currently accounts for the majority of Internet traffic. One factor that enables video streaming is HTTP Adaptive Streaming (HAS), that allows the users to stream video using a bit rate that closely matches the available bandwidth from the server to the client. MPEG Dynamic Adaptive Streaming over HTTP (DASH) is a widely used standard, that allows the clients to select the resolution to download based on their own estimations. The algorithm for determining the next segment in a DASH stream is not part of the standard, but it is an important factor in the resulting playback quality. Nowadays vehicles are increasingly equipped with mobile communication devices, and in-vehicle multimedia entertainment systems. In this paper, we evaluate the performance of various DASH adaptation algorithms over a vehicular network. We present detailed simulation results highlighting the advantages and disadvantages of various adaptation algorithms in delivering video content to vehicular users, and we show how the different adaptation algorithms perform in terms of throughput, playback interruption time, and number of interruptions.
IEEE Access, 2021
This paper presents a novel unmanned aerial vehicle (UAV)-aided mobile edge computing (MEC) archi... more This paper presents a novel unmanned aerial vehicle (UAV)-aided mobile edge computing (MEC) architecture for vehicular networks. It is considered that the vehicles should complete latency-critical computation-intensive tasks either locally with on-board computation units or by offloading part of their tasks to road side units (RSUs) with collocated MEC servers. In this direction, a hovering UAV can serve as an aerial RSU (ARSU) for task processing or act as an aerial relay and further offload the computation tasks to a ground RSU (GRSU). To significantly reduce the delay during data offloading and downloading, this architecture relies on the benefits of line-of-sight (LoS) massive multiple-input–multiple-output (MIMO). Therefore, it is considered that the vehicles, the ARSU, and the GRSU employ large-scale antennas. A three-dimensional (3-D) geometrical representation of the MEC-enabled network is introduced and an optimization method is proposed that minimizes the computation-based...
Dynamic distributed computing environments are comp sed by various entities, which, seeking for t... more Dynamic distributed computing environments are comp sed by various entities, which, seeking for the maximization of th eir welfare while achieving their own goals and aims, may act selfishly, thus, leadin g to a significant deterioration of system’s performance. In general, system entities m ay be classified into two main categories: the Resource Requestors (RRs) wishing t o use and/or exploit resources offered by the other system entities and the Resour ce P oviders (RPs) that offer the resources requested. In this study, a reputation me chanism is proposed which helps estimating RPs trustworthiness, taking into account their past performance in consistently satisfying RRs’ expectations. The trus t management framework is distributed, considers both first-hand information (acquired from the RR’s direct past experiences with the RPs) and second-hand informati on (disseminated from other RRs), while it exhibits a robust behaviour against accurate reputation ratings. The designed mech...
2020 5th South-East Europe Design Automation, Computer Engineering, Computer Networks and Social Media Conference (SEEDA-CECNSM), 2020
Fifth generation (5G) networks use heterogeneous network access technologies to support Mobile No... more Fifth generation (5G) networks use heterogeneous network access technologies to support Mobile Nodes (MNs) with multiple services with different Quality of Service (QoS) constraints. In a 5G architecture, an MN can use Massive Multiple Input Multipole Output (MMIMO) antennas to obtain access to increased telecommunication resources. In these environments the need to support service continuity of MNs is a key issue. Therefore, the design of efficient mobility management schemes for 5G infrastructures is needed. In this paper, a novel mobility management scheme for 5G systems is proposed. Whenever the perceived Quality of Service (QoS) becomes less than a predefined threshold, Vertical Handover (VHO) is initiated. Subsequently, network selection is performed, considering the energy level of the MN. Finally, a MIH-enhanced FPMIPv6 handover approach is performed to achieve service continuity of the MNs. The proposed scheme is applied to a 5G architecture which includes LTE-A Pro FD-MIMO...
The DiffServ architecture provides a scalable mechanism for QoS introduction in a TCP/IP network.... more The DiffServ architecture provides a scalable mechanism for QoS introduction in a TCP/IP network. DiffServ model is based on the aggregation of traffic flows at an ingress (or egress) point of a network and the IP packet marking for different priority flows, according to several classification criteria. Two approaches exist in the DiffServ architecture: the Absolute and the Relative. In Absolute DiffServ, an admission control scheme is used to provide QoS guarantees as absolute bounds of specific QoS parameters. The Relative DiffServ model provides QoS guarantees per service class expressed with reference to guarantees given to other classes defined. Our study presents a QoS Provisioning & Network Management System. This system is based on an extension of the network management architecture followed and implemented within the scope of the European IST Project MANTRIP. MANTRIP network management system supports quality of service configuration and monitoring in IP networks. Our exten...
Cognitive Radio Networks (CRNs) is the key technology to overcome the disadvantages of static spe... more Cognitive Radio Networks (CRNs) is the key technology to overcome the disadvantages of static spectrum allocation and enhance spectrum utilization through Dynamic Spectrum Access (DSA) techniques. One important topic of the development of CRNs is spectrum handoff, which ensures the uninterrupted communication of Secondary Users (SUs). Two types of spectrum handoff approaches exist, namely the proactive and the reactive spectrum handoff. When the Primary User (PU) traffic is high the proactive spectrum handoff approach is more suitable whereas the reactive handoff on light PU traffic achieves better performance. In this paper we evaluate the use of proactive and reactive spectrum handoff policies in CRNs. Simulations are conducted using NS-3 simulator. To the extent of our knowledge, an extensive CRN simulation regarding spectrum handoff on NS-3 simulator has not been carried out. Furthermore, we implemented a hybrid spectrum handoff scheme that selectively uses either reactive or pr...
Drones
In a fifth generation (5G) vehicular network architecture, several point of access (PoA) types, i... more In a fifth generation (5G) vehicular network architecture, several point of access (PoA) types, including both road side units (RSUs) and aerial relay nodes (ARNs), can be leveraged to undertake the service of an increasing number of vehicular users. In such an architecture, the application of efficient resource allocation schemes is indispensable. In this direction, this paper describes a network slicing scheme for 5G vehicular networks that aims to optimize the performance of modern network services. The proposed architecture consists of ground RSUs and unmanned aerial vehicles (UAVs) acting as ARNs enabling the communication between ground vehicular nodes and providing additional communication resources. Both RSUs and ARNs implement the LTE vehicle-to-everything (LTE-V2X) technology, while the position of each ARN is optimized by applying a fuzzy multi-attribute decision-making (fuzzy MADM) technique. With regard to the proposed network architecture, each RSU maintains a local vi...
Electronics
Fifth generation Vehicular Cloud Computing (5G-VCC) systems support various services with strict ... more Fifth generation Vehicular Cloud Computing (5G-VCC) systems support various services with strict Quality of Service (QoS) constraints. Network access technologies such as Long-Term Evolution Advanced Pro with Full Dimensional Multiple-Input Multiple-Output (LTE-A Pro FD-MIMO) and LTE Vehicle to Everything (LTE-V2X) undertake the service of an increasing number of vehicular users, since each vehicle could serve multiple passenger with multiple services. Therefore, the design of efficient resource allocation schemes for 5G-VCC infrastructures is needed. This paper describes a network slicing scheme for 5G-VCC systems that aims to improve the performance of modern vehicular services. The QoS that each user perceives for his services as well as the energy consumption that each access network causes to user equipment are considered. Subsequently, the satisfactory grade of the user services is estimated by taking into consideration both the perceived QoS and the energy consumption. If the...
WTS 2018 - Wireless Telecommunications Symposium, 2018
Fifth Generation Vehicular Cloud Computing (5G-VCC) systems use heterogeneous network access tech... more Fifth Generation Vehicular Cloud Computing (5G-VCC) systems use heterogeneous network access technologies in order to fulfill the requirements of modern services, including medical services with strict constraints. Therefore, the need for efficient Vertical Handover (VHO) management schemes must be addressed. In this paper, a VHO management scheme for supporting medical services in 5G-VCC systems, is described. It consists of the VHO initiation and the network selection processes, while at the same time, the vehicle's velocity, its current connection type, as well as the status of the onboard patient's health, are considered. Specifically, during the VHO initiation process the necessity to perform handover is evaluated. Subsequently, the network selection process selects the appropriate network alternative considering both medical service requirements and patients' health status. The proposed scheme is applied to a 5G-VCC system which includes Long Term Evolution (LTE) a...
IISA 2017 - The 8th International Conference on Information, Intelligence, Systems and Applications, 2017
Healthcare Vehicular Cloud Computing (VCC) systems use heterogeneous network access technologies ... more Healthcare Vehicular Cloud Computing (VCC) systems use heterogeneous network access technologies to fulfill the requirements of medical services and enhance the health monitoring and care of vehicular users. In such a system, efficient network selection algorithms are required to satisfy the constraints of critical medical services such as health monitoring using sensors, live streaming of medical video and clinical data transmission. Therefore, in this paper a network selection scheme for supporting medical services in VCC systems is proposed.
IEEE Symposium on Computers and Communications (ISCC), 2017
Vehicular Cloud Computing (VCC) systems use heterogeneous network access technologies in order to... more Vehicular Cloud Computing (VCC) systems use heterogeneous network access technologies in order to fulfill the requirements of modern services. Therefore, the need for efficient Vertical Handover (VHO) management schemes must be addressed. In this paper a VHO management scheme for VCC systems is described. The proposed method takes into account the vehicle's velocity as well as its current connection type and applies a two step VHO algorithm to reduce operations' costs and optimize mobility management. Accordingly, as a first step a VHO initiation process evaluates the necessity to perform handover and subsequently a network selection process selects the appropriate network alternative considering both vehicular service requirements and operators' policies. The proposed scheme is applied to a VCC system which includes Long Term Evolution (LTE) Macrocells and Femtocells as well as 802.11p Road Side Units (RSUs). Performance evaluation shows that the suggested algorithm ens...
2018 9th International Conference on Information, Intelligence, Systems and Applications (IISA), 2019
Virtual tourism is a novel trend that enhances the experience the users perceive from touristic p... more Virtual tourism is a novel trend that enhances the experience the users perceive from touristic places, such as archaeological sites. Drones are equipped with 360o video cameras and used for video capturing of the heritage sites. The video material is streamed to the users in real time, enriched with additional 3D, Augmented Reality (AR) or Mixed Reality (MR) material. Furthermore, the selection of the appropriate flying route for each drone should be performed, in order to provide a satisfactory tour experience to the user, considering his preferences about specific monuments. To address this issue, this paper describes a heritage route selection scheme for supporting real-time virtual tours in sites with cultural interest using drones. The proposed scheme applies a Fuzzy Multiple Attribute Decision Making (FMADM) algorithm, the Trapezoidal Fuzzy Topsis for Heritage Route Selection (TFT-HRS), to accomplish the ranking of the candidate heritage routes. The algorithm uses Interval-Va...
The recently created IETF 6TiSCH working group combines the high reliability and low-energy consu... more The recently created IETF 6TiSCH working group combines the high reliability and low-energy consumption of IEEE 802.15.4e Time Slotted Channel Hopping with IPv6 for industrial Internet of Things. We propose a distributed link scheduling algorithm, called Local Voting, for 6TiSCH networks that adapts the schedule to the network conditions. The algorithm tries to equalize the link load (defined as the ratio of the queue length over the number of allocated cells) through cell reallocation. Local Voting calculates the number of cells to be added or released by the 6TiSCH Operation Sublayer (6top). Compared to a representative algorithm from the literature, Local Voting provides simultaneously high reliability and low end-to-end latency while consuming significantly less energy. Its performance has been examined and compared to On-thefly algorithm in 6TiSCH simulator by modeling an industrial environment with 50 sensors.
Cloud Computing constitutes an emerging computing paradigm consisting of elements of grid computi... more Cloud Computing constitutes an emerging computing paradigm consisting of elements of grid computing, utility computing and software-defined networks. The aggregation of these technologies offers a new environment for the deployment of services. Cloud computing environment provides capabilities which are unique covering the existing and future needs of organizations and companies. Moreover, this environment supports big data applications usually forming the core elements of research projects. Therefore cloud computing technology and big data are linked to each other. However, the capabilities of cloud computing environment create challenges concerning the security of data applications and its systems. In this respect, security issues are present on big data applications. By adopting the cloud computing environment, the provider has to incorporate security systems and policies in its infrastructure in order to mitigate the security threats. In this paper, multilayered security architecture is defined based on defense in depth. In this architecture the cloud infrastructure is divided into defense zones to achieve better security control. Additionally, intrusion detection system (IDS), honeypots and firewalls are incorporated alongside the defense mechanisms of the cloud infrastructure. In this way, a secure architecture is applied in which the end service is provided uninterrupted, while control over the level of security is maintained.
2014 International Conference on Telecommunications and Multimedia (TEMU), 2014
Following the Always Best Connection (ABC) principle of the 4th generation wireless networks user... more Following the Always Best Connection (ABC) principle of the 4th generation wireless networks users of mobile services would be provided with connectivity to the best access technology all the time. In such a context mobile devices are equipped with multiple radio interfaces allowing connectivity to the most suitable network environment based on users requirements and operators policies. Seamless vertical handover plays the key role for mobility across various access networks offering service continuity to users. In this paper seamless handover solutions are presented between 3GPP (Third Generation Partnership Project) and non-3GPP wireless access technologies utilizing functionalities of the Evolved Packet Core (EPC) network of the LTE-A, as well as, of the IEEE 802.21 standard. The schemes presented provide low latencies while supporting services QoS constraints, as well as, user requirements and provider policies.
Local voting: A new distributed bandwidth reservation algorithm for 6TiSCH networks
Computer Networks
Sensors
Mobile edge computing (MEC) represents an enabling technology for prospective Internet of Vehicle... more Mobile edge computing (MEC) represents an enabling technology for prospective Internet of Vehicles (IoV) networks. However, the complex vehicular propagation environment may hinder computation offloading. To this end, this paper proposes a novel computation offloading framework for IoV and presents an unmanned aerial vehicle (UAV)-aided network architecture. It is considered that the connected vehicles in a IoV ecosystem should fully offload latency-critical computation-intensive tasks to road side units (RSUs) that integrate MEC functionalities. In this regard, a UAV is deployed to serve as an aerial RSU (ARSU) and also operate as an aerial relay to offload part of the tasks to a ground RSU (GRSU). In order to further enhance the end-to-end communication during data offloading, the proposed architecture relies on reconfigurable intelligent surface (RIS) units consisting of arrays of reflecting elements. In particular, a dual-RIS configuration is presented, where each RIS unit serve...
IEEE Transactions on Wireless Communications
A new detection scheme for multiuser multiple-input multiple-output (MIMO) systems is analyticall... more A new detection scheme for multiuser multiple-input multiple-output (MIMO) systems is analytically presented. In particular, the transmitting users are being categorized in two distinct priority service groups, while they communicate directly with a multi-antenna receiver. The linear zero-forcing scheme is applied in two consecutive detection stages upon the signal reception. In the first stage, the signals of one service group are detected, followed by the second stage including the corresponding detection of the remaining signals. An appropriate switching scheme based on specific transmission quality requirements is utilized prior to the detection so as to allocate the signals of a given service group to the suitable detection stage. The objective is the enhancement of the reception quality for both service groups. The proposed approach can be implemented directly in cognitive radio communication assigning the secondary users to the appropriate service group. The exact outage probability of the considered system is derived in closed form. The special case of massive MIMO is further studied yielding some useful engineering outcomes; the effective channel coherence time and a certain optimality condition defining both the transmission quality and effective number of independent transmissions.
Mobility Management on 5G Vehicular Cloud Computing Systems
Vehicular Communications
Fifth generation (5G) Vehicular Cloud Computing (VCC) systems use heterogeneous network access te... more Fifth generation (5G) Vehicular Cloud Computing (VCC) systems use heterogeneous network access technologies to fulfill the requirements of modern services. Multiple services with different Quality of Service (QoS) constraints could be available in each vehicle, while at the same time, user requirements and provider policies must be addressed. Therefore, the design of efficient Vertical Handover (VHO) management schemes for 5G-VCC infrastructures is needed. In this paper, a novel VHO management scheme for 5G-VCC systems is proposed. Whenever the user satisfaction grade becomes less than a predefined threshold, VHO is initiated and network selection is performed, considering the velocity of the vehicle, network characteristic criteria such as throughput, delay, jitter and packet loss, as well as provider policy criteria such as service reliability, security and price. The proposed scheme uses linguistic values for VHO criteria attributes represented by Interval Valued Pentagonal Fuzzy Numbers (IVPFNs) to express the information using membership intervals. The VHO scheme is applied to a 5G-VCC system which includes 3GPP Long Term Evolution (LTE) and IEEE 802.16 Worldwide Interoperability for Microwave Access (WiMAX) Macrocells and Femtocells, as well as IEEE 802.11p Wireless Access for Vehicular Environment (WAVE) Road Side Units (RSUs). Performance evaluation shows that the suggested method ensures the Always Best Connection (ABC) principle, while at the same time outperforms existing VHO management schemes.
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Papers by Angelos Michalas