Fifth Generation (5G) networks and beyond are envisioned to provide user-focused communications, supporting diverse services with enhanced Quality of Service (QoS). Pivotal to this evolution is user equipment, which is increasingly performing advanced computational tasks beyond the edge of the network, known as the Extreme-Edge. Seamless integration of Extreme-Edge devices (EEDs) into the 5 G framework is however hindered, due to challenges in terms of device management, resource restrictions and interoperability issues. To address these barriers, we realize the Extreme-Edge Orchestrator (EEO), a management and orchestration framework enabling the extension of the 5 G cloud-to-edge continuum towards the Extreme-Edge. The EEO enables real-time resource monitoring and lifecycle management of network applications, including Artificial Intelligence/Machine Learning (AI/ML) tasks, deployed on EEDs. Unlike existing theoretical studies, our solution is deployed on an operational research-center-wide 5 G testbed and evaluated using an AI/ML-based network QoS prediction application, in the automotive domain. Our results show that the EEO supports efficient resource utilization, dynamic EED selection under device mobility scenarios and maintains robust service performance under computational stress-demonstrating its capability to support next-generation network services.

Advanced fifth generation (5 G) and beyond (B5G) communication networks have revolutionized wireless technologies, supporting ultra-high data rates, low latency, and massive connectivity. However, they also introduce vulnerabilities, particularly in decentralized Industrial Internet of Things (IIoT) environments. Traditional cryptographic methods struggle with scalability and complexity, leading researchers to explore Artificial Intelligence (AI)-driven physical layer techniques for secure communications. In this context, this paper focuses on the utilization of Machine and Deep Learning (ML/DL) techniques to tackle with the common problem of eavesdropping detection. To this end, a simulated industrial B5G heterogeneous wireless network is used to evaluate the performance of various ML/DL models, including Random Forests (RF), Deep Convolutional Neural Networks (DCNN), and Long Short-Term Memory (LSTM) networks. These models classify users as either legitimate or malicious ones based on channel state information (CSI), position data, and transmission power. According to the presented numerical results, DCNN and RF models achieve a detection accuracy approaching $100 \backslash \%$ in identifying eavesdroppers with zero false alarms. In general, this work underlines the great potential of combining AI and Physical Layer Security (PLS) for next-generation wireless networks in order to address evolving security threats.

Stacked intelligent metasurfaces (SIM) transceiver design enables precoding in the wave domain while enjoying reduced energy consumption and hardware cost. On this ground and contrary to previous works studying various achievable rates, we derive the ergodic mutual information (EMI) at the large system region in closed form for SIM-assisted multiple-input-multiple-output (MIMO) systems based on statistical channel state information (CSI). Next, by applying a gradient ascent algorithm, we maximize the EMI with respect to the phase shifts of the two SIMs of the transceiver simultaneously, which saves significant overhead compared to a traditional alternating optimization (AO) approach. Simulations shed light in the performance of the proposed system at the large system limit and provide a comparison under different CSI conditions.

Although reconfigurable intelligent surface (RIS) is a promising technology for shaping the propagation environment, it consists of a single-layer structure within inherent limitations regarding the number of beam steering patterns. Based on the recently revolutionary technology, denoted as stacked intelligent metasurface (SIM), we propose its implementation not only on the base station (BS) side in a massive multiple-input multiple-output (mMIMO) setup but also in the intermediate space between the base station and the users to adjust the environment further as needed. For the sake of convenience, we call the former BS SIM (BSIM), and the latter channel SIM (CSIM). To this end, we achieve hybrid wave-based combining at the BS and wave-based configuration at the intermediate space. Specifically, we propose a channel estimation method with reduced overhead, being crucial for SIM-assisted communications. Next, we derive the uplink sum spectral efficiency (SE) in closed form in terms of statistical channel state information (CSI). Notably, we optimize the phase shifts of both BSIM and CSIM simultaneously by using the projected gradient ascent method (PGAM). Compared to previous works on SIMs, we study the uplink transmission in a mMIMO setup, channel estimation in a single phase, a second SIM at the intermediate space, and simultaneous optimization of the two SIMs. Simulation results show the impact of various parameters on the sum SE, and demonstrate the superiority of our optimization approach compared to the alternating optimization (AO) method.

The advent of 5G and beyond systems is expected to shape the automotive vertical, as safety-critical vehicular applications rely on the network to meet their stringent Quality of Service (QoS) requirements. Predictive QoS (pQoS) has been proposed as a mechanism that allows automotive applications to proactively adapt in view of forthcoming QoS changes. Although pQoS is typically facilitated via classical (centralized) Machine Learning (ML) methods, the demand for data privacy has led to the emergence of distributed ML schemes. Efficient training of ML models however requires large volumes of (kinematic-state and connectivity) QoS data, so as to capture the involved spatio-temporal effects.To that end we hereby present and publicly share NordicDat, a QoS dataset collected during a two-week measurement campaign, driving across three European countries. NordicDat contains over 90K samples of physical layer, network and mobility-related features. Contrary to prior works, it includes multiple instances of cross-boarder roaming, diverse vehicle speed profiles and radio access technologies (generations). Further, we provide a thorough NordicDat data analysis, highlighting the dependencies between the NordicDat’s features and the resulting QoS values (throughput, delay). To showcase its broad usability, we train pQoS ML models over NordicDat in classical and distributed fashion. Our results demonstrate for the first time the viability of distributed pQoS with real-word data, which achieves similar (within a margin of 10%) accuracy to that of classical ML, cropping privacy-preserving benefits.

Fifth-generation (5G) heterogeneous networks provide a promising perspective as of the increasing demands for mass access to the medium and dense machine type communications. Therefore, advanced physical layer techniques are enabled in order to meet various and diverse aspects of high bandwidth and zero latency applications. In this framework, relaying-assisted transmission can improve network performance, as it increases throughput levels, decreases interference impact and extends the coverage area of a cellular orientation. In this paper, we jointly consider the problem of subcarrier allocation and power management in 5G millimeter wave systems, where multiple-input-multiple-output antennas are used in base stations, relay nodes (RNs), as well as in mobile terminals. To this end, the performance of various relaying-assisted transmission approaches has been evaluated. According to the presented results, total system capacity can be improved by up to 110%, compared to the case where no RNs are deployed. In addition, spectral and energy efficiency, as well as cell edge throughput, are significantly improved.

In the modern enterprise world, collaboration has emerged as a standard of best business practice. In order to build competitive advantages and minimize inefficiencies, organizations nowadays pursuit strategic alliances with partners outside the comfort of familiar security zones, loosen their hierarchical structures, exploit edge competencies, and aggregate diverse and heterogeneous sources of information. Nevertheless, such techniques dictate the concentration, use, and circulation of corporate information and sensitive personal data and, thus, ignite severe information confidentiality and privacy concerns. Hence, the employment of the appropriate collaboration technology is not sufficient; potential lack of successful protection mechanisms limits the effectiveness of partnerships and denies the respective investments to reach their full potential. In this paper, an authorization framework toward the protection of sensitive resources in the context of cross-enterprise scenarios is presented. The proposed framework is founded on the utilization of a semantic information model, which integrates individual privacy preferences, organizational access control rules and information handling policies into the authorization determination procedure. Partners within the framework are organized in a bridged federated architecture in order to build a secure communication network, within which semantic and trust interoperability is guaranteed. Copyright © 2014 John Wiley & Sons, Ltd.

Abstract Power control has been a standard issue in modern wireless communications. As a result, several cooperative schemes have been developed towards reducing the downlink transmission power. One possible approach is the use of relays that forward information from the base station (BS) to the mobile stations (MSs). However, up to now, the proposed relaying schemes are focusing solely on channel characteristics. In this work, a novel, content‐aware relaying scheme is introduced, where the MSs can act as active relays based on their requested content and channel quality. Content awareness is achieved with a cross‐layer algorithm, which considers an information‐centric networking layer. The performance of the proposed approach has been evaluated considering a multiple input multiple output (MIMO) cellular configuration with one tier of cells around the central cell, where the downlink transmission power (in terms of mean values) has been compared to the typical non‐content‐aware case. For this reason, a hybrid system—link level simulator has been developed that executes independent Monte Carlo (MC) simulations in parallel. Moreover, the orthogonal frequency division multiple access (OFDMA) physical layer protocol has been employed as well, in order to comply with fourth generation standards. The derived results indicate that, compared to the non‐content‐aware case, the proposed relay transmission algorithm can provide up to 7/17% transmission power gain in medium or highly loaded networks (i.e., 10% and 40% blocking probabilities, respectively) in a symmetric 2 × 2 MIMO configuration (i.e., equal number of transmit and receive antennas). Moreover, compared to the case where no relay transmission is supported, then the aforementioned gain can reach up to 20%. Finally, the proposed algorithm can provide up to 25% reduction on the overall transmission delay from the relay node to the destination compared to the non‐content‐aware case. Copyright © 2014 John Wiley & Sons, Ltd.

ABSTRACT This paper investigates the performance of different transmission strategies for multiple input multiple output (MIMO) networks with the wideband code division multiple access (WCDMA) air interface as the physical layer protocol. Performance is evaluated statistically with extended Monte Carlo (MC) simulations in terms of achievable bit‐error (BER) rate in frequency selective fading cellular environments. As results indicate, for a MIMO configuration withMtantennas at the base station (BS),Mrantennas per mobile station (MS) andLresolvable multipath components, the transmission strategy based on signal to noise ratio (SNR) enhancement is the optimum transmit solution forMt ≤ Mr. However, the pre‐RAKE maximal ratio combining transmission strategy outerperforms the SNR enhancement strategy with post‐RAKE processing forMt > Mr, high number of resolvable multipath components and channel estimation error up to 40%. Moreover, a transmission scheme based on the maximization of the ratio of the desired MS's signal to the total amount of interference that causes to the network is proposed, and is shown that outerperforms the conventional transmission schemes for high data rate services. For symmetric MIMO configurations (Mt = Mr) and two resolvable multipath components, this strategy provides 30% BER gain compared to the maximization of SNR strategy. This gain can be further improved by 25% with a proposed adjacent sector cooperation algorithm. Copyright © 2011 John Wiley & Sons, Ltd.

The margin adaptive problem for the downlink of Orthogonal Frequency Division Multiple Access is tackled in this work. A subcarrier allocation algorithm is presented, which formulates the issue of subcarrier allocation as a combinatorial auction, where the base station auctions the OFDM subcarriers and the users compete for their allocation. A major feature of the proposed algorithm is its distributed nature, since each user decides independently which subcarriers to bid for, informs the base station for his preferences, and the base station is the entity that makes the decision on the allocation, based on power criteria. The presentation of the algorithm is followed by a series of simulations. The simulations indicate that the performance of the proposed algorithm approaches the performance of the optimal, Hungarian algorithm: the offered bit rate is at least 98.77% of the optimal while the transmit power lies within the range 0.20dB-1.62dB higher than the optimal one. Additionally, based on execution time measurements, it is shown that the necessary execution time is much lower than that of the optimal algorithm, indicating thus a much lower computational complexity.

Fractional frequency reuse for the downlink of multicellular WiMAX networks is examined in this work. Three different schemes are evaluated through simulations, including distance-based and SINR-based approaches, as well as a new scheme which is based on load-balancing between different reuse regions. The proposed load-balancing scheme overcomes the main weakness of the SINR-based approach, namely its inability to manage efficiently the available resources of both Reuse-1 and Reuse-3 zones, as their size varies. The simulation results exhibit a clearly better performance of the proposed algorithm compared to distance-based and SINR-based approaches. It is shown that the employment of fractional frequency reuse with the proposed load-balancing approach improves the performance of WiMAX networks in terms of a variety of metrics, such as blocking probability and achievable bit rate.

The opportunistic beamforming (OB) technique in multicellular OFDMA networks is investigated in this paper. For this reason, three cross-layer radio resource management (RRM) algorithms for OFDMA operational scenarios that are based on typical resource allocation targets such as minimization of transmit power, maximization of throughput and interference averaging are considered. The OB concept is combined with the considered RRM algorithms and a comparative performance analysis between the two types of resulted networks (omni and OB) is performed in terms of throughput, blocking probability and fairness. The simulation results suggest that OB is preferred for OFDMA systems with opportunistic rate adaptation rather than power controlled systems which offer QoS provision. According to the presented results, OB provides to OFDMA systems with opportunistic rate adaptation a ~13% throughput gain and ~75% gain in terms of blocking probability. In addition, it is shown that the combination of OB with interference averaging RRM algorithms has a minor beneficial impact only on the system fairness.

Mobile and wireless technology has revolutionized people’s lives by enabling data delivery anytime, anywhere, liberating the users from the restrictions of wired networks. In addition broadband communications permit high speed data connections. Since multimedia content delivered on-line requires reasonably high data rates and today’s wireless networks (3G, Wi-Fi, WiMAX etc) can support the quality requirements of media streaming delivery, while mobile devices handheld or not (Pocket PC, smart phones, laptop pc etc) are able to accommodate a variety of content formats, content delivery has become an indisputable trend. This paper presents such a content delivery network, the ENAMORADO architecture, which is the outcome of the work carried out in the IST project ENAMORADO (Enabling Nomadic Agents in a Multimedia Oriented Architecture of Distributed Objects). The ENAMORADO architecture covers the full content delivery chain from the media producers to the end users incorporating the content production, annotation, aggregation, adaptation and delivery. The paper describes the reference architecture of the infrastructure as well as the testbed used in the components integration and validation process. In addition further system evaluation results are presented.

Orthogonal Frequency Division Multiple Access (OFDMA) techniques are investigated in this paper. Five sub-channel allocation algorithms are analysed and their performance in a multicellular environment is evaluated with simulations. Four schemes of lower complexity, suitable for the early deployment of wireless systems, are compared with a more computationally demanding scheme with respect to their blocking probability, loading factor, and offered bit rate. The channel condition of each carrier is calculated and its knowledge is used for power controlled adaptive modulation, as an essential feature of the OFDMA technique. The results show that a wireless system in its early deployment phase (up to 15%-30% blocking probability) can employ simple OFDMA techniques capable of achieving high throughput.

This paper presents a problem solving environment (PSE) for the grid-enabled execution of Monte Carlo simulations. Our main concern during the design and development of the PSE was to hide the complexity of using the grid infrastructure from the actual users and simplify the way users run their application on grid resources. In order to assist non grid-expert users to execute their simulations on the grid, we have implemented transparent mechanisms that automatically create the appropriate scripts and components required for grid execution by taking as input plain Matlab files. The PSE sets up a temporary distributed Matlab environment on grid resources by using the Matlab compiler and allows the concurrent execution of standard Matlab code. The PSE has been used for several wideband code division multiple access (WCDMA) system simulation scenarios in the production grid provided by the EGEE infrastructure. Simulation results regarding performance of the PSE are presented.

Passive network monitoring is required for the operation and maintenance of communication networks as well as to detect frauds and attacks. Typically, raw packet-level traffic traces are collected using suitable traffic probe devices and fed to monitoring applications (IDSs, antivirus, etc.) for analysis, with potential risks for the legitimate privacy rights of the customers. This paper aims to discuss the technical feasibility and the underlying research challenges of a two-tiered privacy-preserving network monitoring system, where carefully designed data protection mechanisms can coexist with suitably adapted monitoring applications.

The potential invasion of individuals' privacy constitutes the flip side of the advanced services' provision, boosted by the recent advances in mobile communications, location and sensing technologies and data processing. Being situated in the realms of legal and social studies, the notion of privacy is mainly left, concerning its protection, to legislation and service providers' self-regulation by means of privacy policies. However, all laws and codes of conduct are useless without enforcement. Based on this concept, this paper presents a framework that formally models the privacy principles that regulate the services' provision and incorporates them into a privacy enhancing middleware system. The mediation of the considered architecture between the users and the service providers, guarantees the enforcement of a privacy policy that is defined by the technical translation of the privacy principles and regulations and overrides the service providers' ones.

In this paper the impact of the position of user's hand holding a multiple-input-multiple-output (MIMO) terminal on system performance and more specifically on channel capacity is investigated. We consider a 4times4 MIMO system with a personal digital assistant (PDA) equipped with a compact array of 4 patch elements. Radiation field patterns of the antenna elements in the presence of the other elements as well as in the presence of a user's hand are simulated. Different positions of the user's hand are taken into account. The covariance matrix of the receiving antennas is evaluated by means of the obtained patterns. A correlation-based channel model is considered, where the antenna patterns are incorporated. Extensive simulations showed that the performance of the MIMO systems varies significantly with the position of the user's hand.

This paper presents an adaptive admission control (AC) strategy for WCDMA multicellular networks which employ antenna arrays (AAs) at the base station (BS). The adaptive AC strategy generates beams that focus the transmitted power in the directions of desired users, thus minimizing interference and increasing capacity. A WCDMA system level simulator has been developed in order to evaluate the performance of the proposed adaptive AC strategy by means of Monte Carlo(MC) simulations. Results for different traffic scenarios with up to four tiers of interfering cells show that a network with the adaptive AC strategy can achieve almost two times higher throughput per beam when compared to the traditional AC in a multirate multicellular environment with hotspot areas.

The adoption of packet-switched technologies in mobile communication systems has enabled the provision of IP-based services to mobile users. Yet, these systems, such as the UMTS network, are not flexible enough to leave space for IP-oriented protocols to dominate nor are they able to meet the stringent QoS requirements imposed by multimedia services. This paper presents an innovative Beyond 3G network architecture, denoted as SIPRAN, posing an evolution to the standard UMTS network. According to the proposed concept, the GPRS Support Nodes are integrated into a single entity, while the Session Initiation Protocol is adopted for performing mobility and session management; these modifications result in the smooth evolution of the UMTS Core Network towards IP, while accomplishing a significant performance gain. In order to evaluate the target architecture and substantiate its actual effectiveness, a series of experiments was carried out, by utilizing a fully-functional emulator.

The design and development of two novel dual-band coplanar waveguide (CPW)-fed slot antennas for broadband wireless applications is presented. The first antenna operates in GSM (1.7-1.9 GHz) and IEEE 802.11b (2.4-2.5 GHz WLAN) frequency bands, while the second antenna operates in the 802.11b (2.4-2.5 GHz) and 802.11b (5.1-5.9 GHz) frequency bands. These antennas are aimed to cover the gap in the multiband wireless applications domain. Simulation work has been performed using commercially available three-dimensional electromagnetic tools and prototypes have been built in order to explore the actual performance of these two antennas. Satisfactory agreement in simulation and experimental results is shown. These antennas can easily be attached on the backplane of PDAs, smartphones or notebooks, to meet users' needs for wireless connectivity in a small form factor.

This paper describes a novel single feed dual-band inverted-F antenna (IFA) operating in the ISM and UNNI bands. The antenna is printed on a PC card and is suitable for Bluetooth and wireless LAN 802.11a applications. The three-dimensional finite element method (FEM) electromagnetic simulator, HFSS, is used in the design simulation of the IFA/PC card system. The results exhibit a proper operation of the antenna in terms of return loss, bandwidth and efficiency at both bands.