Demosthenes Vouyioukas

University of the Aegean, Kastro, North Aegean, Greece

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Publications (61)13.35 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: In this work, we study a cooperative network with multiple full-duplex buffer-aided relays. A hybrid cooperative relaying policy is proposed that employs power adaptation and consists of two alternative schemes: (i) full-duplex transmission through the relay which requires the least total power expenditure and loop interference is mitigated through power adaptation; (ii) buffer-aided max - link selection with power adaptation, when full-duplexity is not feasible. Aiming to reduce the overhead of channel state information (CSI) acquisition and processing, we propose a suboptimal distributed method for relay selection, for which the network performance is not degraded significantly. We show that power adaptation offers reduced overhead of CSI acquisition. Numerical results and comparisons with other state-of-the-art relaying schemes are provided and performance evaluation in terms of throughput, power minimization and switching rate, show the benefits of the proposed hybrid scheme.
    IEEE International Conference on Communications (ICC) 2014, Sydney, Australia; 06/2014
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    ABSTRACT: In future wireless mobile networks, data rate and quality of service are expected to be comparable to those of wired deployments. To achieve this target, novel architectures must be adopted, successfully countering the disadvantages of the wireless transmission. Inspired by that, cooperative relaying was proposed because of the various gains it introduces to the network. In this work we propose a scheme consisting of multi-mode decode and forward relays facilitating the communication between a base station and a user terminal (UT). By equipping the relays with two interfaces, we can exploit the plethora of the available wireless protocols. Also, instead of performing multi-relay transmissions, we adopt an opportunistic relaying scheme due to its simplicity and outage-optimality. Additionally, we incorporate successive transmissions to improve the spectral efficiency, thus recovering the half-duplex loss in capacity due to the two-hop transmission. However, as inter-relay interference arises from successive transmissions, we propose mitigation techniques through interference cancellation and out-band transmissions using the multi-mode relays. At the same time, an energy-aware mechanism is implemented in the selected relay’s transmission, opting for power reduction, as the channel state information is acquired prior to the signal’s forwarding to the UT. Finally, we give numerical results by comparing the proposed energy-aware multi-mode relaying (EA-MMR) scheme, with two other schemes in terms of average end-to-end capacity, outage probability, delay distribution and power gain.
    Wireless Personal Communications 01/2014; · 0.43 Impact Factor
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    ABSTRACT: In this work, we present a buffer-aided successive opportunistic relaying scheme (herein called BA-SOR) that aims at improving the average capacity of the network when inter-relay interference (IRI) arises between relays that are selected for simultaneous transmission and reception.We propose a relay selection policy that, by exploiting the benefits of buffering at the relays, decouples the receiving relay at the previous time slot to be the transmitting relay at the next slot. Furthermore, we impose an interference cancellation (IC) threshold allowing the relay that is selected for reception, to decode and subtract the IRI. The proposed relaying scheme selects the relaying pair that maximizes the average capacity of the relay network. Its performance is evaluated through simulations and comparisons with other state-of-the-art half- and full-duplex relay selection schemes, in terms of outage probability, average capacity and average delay. The results reveal that a tradeoff has to be made between improving the outage at the cost of reduced capacity and increased delay and vice versa. Finally, conclusions are drawn and future directions are discussed, including the need for a hybrid scheme incorporating both half and full-duplex characteristics.
    European Transactions on Telecommunications 08/2013; · 1.05 Impact Factor
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    ABSTRACT: Next generation wireless communication networks intend to take advantage of the integration of terrestrial and aerospace infrastructures. Besides, multiple-input multiple-output (MIMO) architecture is the key technology, which has brought the wireless gigabit vision closer to reality. In this direction, high-altitude platforms (HAPs) could act as relay stations in the stratosphere transferring information from an uplink to a downlink MIMO channel. This paper investigates the performance of a novel transmission scheme for the delivery of mobile-to-mobile (M-to-M) services via a stratospheric relay. It is assumed that the source, relay, and destination nodes are equipped with multiple antennas and that amplify-and-forward (AF) relaying is adopted. The performance is analyzed through rigorous simulations in terms of the bit-error rate (BER) by using a recently proposed 3D geometry-based reference model in spatially correlated flat-fading MIMO channels, employing a hierarchical broadcast technique and minimum mean square error (MMSE) receivers.
    International Journal of Antennas and Propagation 06/2013; 2013. · 0.68 Impact Factor
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    ABSTRACT: Future Internet is expected to sustain a huge number of devices, many orders of magnitude higher than state-of-the-art network architectures and handle larger and unconventional information flows. Machine Type communications (MTC) will play a critical role in this evolution and thus both architectural and algorithmic enhancements to existing converged mobile and fixed network infrastructures are needed. In this paper, we focus on resource management issues for combined Human-to-Human (H2H) and Machine-to-Machine (M2M) traffic. The proposed Context-Aware Backhaul Management (CABM) scheme is applicable for M2M gateways, which can provide the interconnection between cellular and capillary networks both via wired and wireless backhaul alternatives. CABM scheme adopts efficient QoS provisioning procedures, by taking into consideration the diverse QoS requirements of novel MTC services. Simulation results show that the proposed MTC Request Admission Control (MTCR-AC) algorithm is resilient regarding QoS-related metrics in overload-state situations, while its inherent prediction-based decision-making procedures can offer significant performance gains, too.
    IEEE International Conference on Computer, Information and Telecommunication Systems (CITS); 05/2013
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    ABSTRACT: In today’s heterogeneous networking (HetNet) environments, where end users are provided with universal connectivity opportunities, femtocell deployments can become key players in the enhancement of critical performance indicators such as capacity, coverage, QoS, etc. In order to confront the up-to-date LTE femtocell challenges, we propose a context-aware framework that provides a controlled environment from the femtocell point of view, which is required for applicable functionality. More specifically, we aim to (a) control the local environment where the femtocell is placed within, by efficiently managing the total incoming traffic load and by continuously adjusting the distribution of the backhaul capacity among the coexisting networks and (b) control the macro–femto interference caused by macrocell users transmitting close to the femtocell by investigating the “femtocell as a relay” concept. Finally, the performance of the proposed framework is evaluated via simulation results showing that the overall performance of a HetNet environment can be leveraged in terms of QoS requirements, energy saving and data rate enhancement.
    EURASIP Journal on Wireless Communications and Networking 03/2013; 62. · 0.54 Impact Factor
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    ABSTRACT: In this paper we consider a simple cooperative network consisting of a source, a destination and a cluster of decode-and-forward half-duplex relays. At each time-slot, the source and (possibly) one of the relays transmit a packet to another relay and the destination, respectively, resulting in inter-relay interference (IRI). In this work, with the aid of buffers at the relays, we mitigate the detrimental effect of IRI through interference cancellation. More specifically, we propose the min-power scheme that minimizes the total energy expenditure per time slot under an IRI cancellation scheme. Apart from minimizing the energy expenditure, the min-power selection scheme, also provides better throughput and lower outage probability than existing works in the literature. It is the first time that interference cancellation is combined with buffer-aided relays and power adaptation to mitigate the IRI and minimize the energy expenditure. The new relay selection policy is analyzed in terms of outage probability and diversity, by modeling the evolution of the relay buffers as a Markov Chain (MC). We construct the state transition matrix of the MC, and hence obtain the steady state with which we can characterize the outage probability. The proposed scheme outperforms relevant state-of-the-art relay selection schemes in terms of throughput, diversity and energy efficiency, as demonstrated via examples.
    02/2013;
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    ABSTRACT: In this work, we propose a buffer-aided successive opportunistic relaying scheme that aims to improve the average capacity of the network when inter-relay interference arises between relays that are selected for transmission and reception. In order to exploit the benefits of buffering at the relays, we propose a relay-pair selection policy that decouples the receiving relay at the previous time slot from being the transmitting relay at the next slot. Furthermore, we impose an interference cancellation threshold allowing the relay that is selected for reception, to decode and subtract the inter-relay interference. The proposed relaying scheme selects the relaying pair that maximizes the average capacity of the relay network. The performance of the proposed scheme is evaluated via simulation and comparisons with other state-of-the-art half and full-duplex relay selection schemes, in terms of outage probability, average capacity and average delay. The results reveal the need for a tradeoff between improving the outage on the cost of reduced capacity and increased delay, and vice versa. Finally, conclusions are drawn and future directions are discussed, including the need for a hybrid scheme incorporating both half and full-duplex characteristics.
    Wireless Communications, Vehicular Technology, Information Theory and Aerospace & Electronic Systems (VITAE), 2013 3rd International Conference on; 01/2013
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    ABSTRACT: In this paper we consider a simple cooperative network consisting of a source, a destination and a cluster of decode-and-forward relays characterized by the half-duplex constraint. At each time-slot the source and (possibly) one of the relays transmit a packet to another relay and the destination, respectively. When the source and a relay transmit simultaneously, inter-relay interference is introduced at the receiving relay. In this work, with the aid of buffers at the relays, we mitigate the detrimental effect of inter-relay interference through either interference cancellation or mitigation. More specifically, we propose the min-power opportunistic relaying protocol that minimizes the total energy expenditure per time slot under an inter-relay interference cancellation scheme. The min-power relay-pair selection scheme, apart from minimizing the energy expenditure, also provides better throughput and lower outage probability than existing works in the literature. The performance of the proposed scheme is demonstrated via illustrative examples and simulations in terms of outage probability and average throughput.
    Personal Indoor and Mobile Radio Communications (PIMRC), 2013 IEEE 24th International Symposium on; 01/2013
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    Demosthenes Vouyioukas
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    ABSTRACT: In this paper, we study the spectrum usage efficiency by applying wideband methods and systems to the existing analog systems and applications. The essential motivation of this work is to define the prospective coexistence between analog FM and digital Spread Spectrum systems in an efficient way sharing the same frequency band. The potential overlaid Spread Spectrum (SS) system can spectrally coincide within the existing narrowband Frequency Modulated (FM) broadcasting system upon several limitations, originating a key motivation for the use of the FM radio frequency band in many applications, encompassing wireless personal and sensors networks. The performance of the SS system due to the overlaying analog FM system, consisting of multiple narrowband FM stations, is investigated in order to derive the relevant bit error probability and maximum achievable data rates. The SS system uses direct sequence (DS) spreading, through maximal length pseudorandom sequences with long spreading codes. The SS signal is evaluated throughout theoretical and simulation-based performance analysis, for various types of spreading scenarios, for different carrier frequency offset ({\Delta}f) and signal-to-interference ratios, in order to derive valuable results for future developing and planning of an overlay scenario.
    11/2012;
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    ABSTRACT: Adaptive Radio Resource Allocation is essential for guaranteeing high bandwidth and power utilization as well as satisfying heterogeneous Quality-of-Service requests regarding next generation broadband multicarrier wireless access networks like LTE and Mobile WiMAX. A downlink OFDMA single-cell scenario is considered where heterogeneous Constant-Bit-Rate and Best-Effort QoS profiles coexist and the power is uniformly spread over the system bandwidth utilizing a Uniform Power Loading (UPL) scenario. We express this particular QoS provision scenario in mathematical terms, as a variation of the well-known generalized assignment problem answered in the combinatorial optimization field. Based on this concept, we propose two heuristic search algorithms for dynamically allocating subchannels to the competing QoS classes and users which are executed under polynomially-bounded cost. We also propose an Integer Linear Programming model for optimally solving and acquiring a performance upper bound for the same problem at reasonable yet high execution times. Through extensive simulation results we show that the proposed algorithms exhibit high close-to-optimal performance, thus comprising attractive candidates for implementation in modern OFDMA-based systems.
    Telecommunication Systems 11/2012; · 1.03 Impact Factor
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    ABSTRACT: The fast emerging technology of femtocells, by utilizing existing IP infrastructures, is promising to improve critical performance indicators of cellular networks, such as coverage and capacity, with minimum cost. However, the placement of femtocells can be completely unrelated to the structure of the cellular network, raising thus interference management challenges. In order to reduce interference at the forward link of femtocells caused by the macrocell Base Station (BS) and to improve the Signal-to-Interference plus Noise ratio (SINR) of macrocell users located in the vicinity of femtocells, we propose a Cooperation Framework for LTE Femtocells' Efficient Integration (COF-FEI) in cellular infrastructures. COF-FEI introduces a novel merging of relaying and femtocells (i.e. femto-relays) and sets the base for an efficient cooperation between macro BS and femtocells through wireless links. As confirmed through simulations results, COF-FEI is able improve the overall Quality of Service provided to the macro and femto end users.
    17th International Workshop on Computer-Aided Modeling Analysis and Design of Communication Links and Networks (CAMAD); 09/2012
  • Nikolaos Nomikos, Demosthenes Vouyioukas
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    ABSTRACT: In this work, we present a successive opportunistic relaying protocol with an inter-relay interference (IRI) mitigation scheme, in a quasi-static environment with Rayleigh fading. In order to recover the half duplex loss of the transmission, we adopt a successive relaying (SR) strategy, coupled with reactive relay selection considering the Signal to Noise Ratio (SNR) and the Signal to Interference plus Noise Ratio (SINR) of each hop, after every source transmission. The main degrading factor in this scheme is the IRI introduced by the best relay which is selected to forward the previous frame, while the rest of the relays are receiving the current source frame. Trying to cancel the effect of IRI, we employ interference cancelation (IC) to subtract the interference signal depending on the capacity of the interference channel.
    IWCMC2012, IEEE International Wireless Communications and Mobile Computing Conference; 08/2012
  • Nikolaos Nomikos, Demosthenes Vouyioukas
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    ABSTRACT: Cooperative relaying with Distributed Space-Time Coding (DSTC) and cooperative Opportunistic Relaying (OR) are the two main relaying techniques that are typically employed in current wireless systems. However, OR is less complex and proven to be outage optimal compared to DSTC. Thus, in this paper we propose a Multi-Mode Relaying (MMR) technique that is based on OR and combined with the Successive Relaying (SR) technique in order to deal with the half-duplex constraint of the relay nodes. MMR, by employing Multi-Mode Decode-and-Forward (MMDF) relay nodes and incorporating two interference mitigation algorithms, not only combines the merits of OR and SR but also is able to alleviate the increased inter-relay interference caused by SR. The performance of MMR is evaluated through simulation and the results shown that it is able to increase the average end-to-end capacity of the wireless path as well as the percentage of high quality packets received at the terminal of the user.
    IEEE (ICC 2012) Workshop in Convergence among Heterogeneous Wireless Systems in Future Internet (CONWIRE 2012), Ottawa, Canada; 06/2012
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    ABSTRACT: Cooperative relaying with Distributed Space-Time Coding (DSTC) and cooperative Opportunistic Relaying (OR) are the two main relaying techniques that are typically employed in current wireless systems. However, OR is less complex and proven to be outage optimal compared to DSTC. Thus, in this paper we propose a Multi-Mode Relaying (MMR) technique that is based on OR and combined with the Successive Relaying (SR) technique in order to deal with the half-duplex constraint of the relay nodes. MMR, by employing Multi-Mode Decode-and-Forward (MMDF) relay nodes and incorporating two interference mitigation algorithms, not only combines the merits of OR and SR but also is able to alleviate the increased inter-relay interference caused by SR. The performance of MMR is evaluated through simulation and the results show that it is able to increase the average end-to-end capacity of the wireless path as well as the percentage of high quality packets received at the terminal of the user.
    Communications (ICC), 2012 IEEE International Conference on; 01/2012
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    ABSTRACT: The present paper studies the performance of a high-speed third-generation (3.5G) networking technology (Enhanced Uplink), in collaboration with well known personal area networks (i.e. Zigbee and Bluetooth) and wireless local area network (WLAN) technology, for delivering pervasive healthcare applications. The association of personal and local area networks along with the 3.5G network is a critical factor for successful development of pervasive e-health services perceived by end-users. In this paper, we propose a methodology for performance assessment based on the joint uplink transmission of voice, real-time video and biomedical data, such us electrocardiogram, vital signals and heart sounds. Various scenarios were concerned for point of care applications in real-time and near-real-time modes and in random locations, where no other system but 3.5G is available. The accomplishment of quality of service (QoS) was explored through the delay and the jitter of the networks' parameters, attributing the joint network system for best performance in the context of the desired e-health services.
    Communications (ICC), 2011 IEEE International Conference on; 07/2011
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    N. Moraitis, D. Vouyioukas, P. Constantinou
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    ABSTRACT: This paper is focused on a detailed coverage and performance analysis of wireless metropolitan area networks based on the IEEE 802.16 standard, which is the basis of WiMAX technology. A coverage study and performance evaluation of a mobile WiMAX system in an urban and suburban environment with the help of a software simulation tool is presented. All the required parameters are given to the program focusing only in suitable propagation models e.g. ITU-R 525/526, or COST231-HATA. The total coverage of the area was 67% from which 52% provides QAM modulation offering higher data rates to the users. Very promising results were also extracted, when utilizing multiple antennas. It is also found that in a 4 2 system the average received power at the limits of each cell is enhanced about 6.1 dB in comparison with the SISO case.
    Communications (ICC), 2011 IEEE International Conference on; 07/2011
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    D. Komnakos, D. Vouyioukas, I. Maglogiannis
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    ABSTRACT: The present paper studies the performance of a high-speed third- generation (3.5G) networking technology, HSPA (High Speed Packet Access), for delivering crisis management and emergency e-health applications under urgent situations via satellite backhauling. The performance of a joint network comprised by wireless sensors, the 3.5G and satellite networks is a critical factor for successful development of emergency services perceived by end-users during a disaster situation. In this paper, we propose an emergency system architecture for performance assessment based on the joint transmission of voice, real-time video, vital data and healthcare records file transfer between the disaster-site and the safe-site. Three scenarios were concerned in terms of real-time, non-real- time and emergency applications in random locations, where no other system but 3.5G is available in case of crisis or disaster. The accomplishment of quality of service (QoS) was explored through a step-by-step improvement of the HSPA and satellite system's parameters, attributing the network system for best performance in the context of the desired emergency services.
    Vehicular Technology Conference (VTC Spring), 2011 IEEE 73rd; 06/2011
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    N. Moraitis, D. Vouyioukas, P. Constantinou
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    ABSTRACT: This paper presents a power angle profile (PAP) measurement campaign at the millimetre-wave band. Angular profiles were measured in different indoor topographies such as offices, corridors and a residence. Detailed angle-of-arrival (AoA) shape factors were derived, describing the spatial properties of the millimeter wave channel. The measurement results were related to the site-specific environments and correlation between the propagation condition and the multipath channel structure was observed. Finally, from the measurement results, it is found that the PAPs can be modeled as a finite scatterer model with a direct component plus multipath arriving within a variable sector α.
    Antennas and Propagation (EUCAP), Proceedings of the 5th European Conference on; 05/2011
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    Demosthenes Vouyioukas, Alexandros Karagiannis
    01/2011; , ISBN: 978-953-307-354-5

Publication Stats

69 Citations
13.35 Total Impact Points

Institutions

  • 2007–2014
    • University of the Aegean
      • Department of Information and Communication Systems Engineering
      Kastro, North Aegean, Greece
  • 1998–2011
    • National Technical University of Athens
      • • School of Electrical and Computer Engineering
      • • Laboratory of Telecommunications
      Athens, Attiki, Greece