The integration of Terrestrial Networks (TN) and Non Terrestrial Networks (NTN) has been explored within the 3GPP standardization forum, and it is now being extended toward discussions on the future 6G vision. An integrated T/NTN is highly heterogeneous and requires different communication protocols and links for each layer, resulting in increased network management and control complexity. The Software Defined Networking (SDN) paradigm can enable unified and efficient T/NTN management, allowing full resource optimization of the satellites, radio access and core network. This paper proposes an optimized SDN-based T/NTN architecture, where Low Earth Orbit (LEO) satellites are dynamically selected to act as multiple SDN controllers if the terrestrial network becomes saturated or unavailable, or to jointly operate with the terrestrial controllers under the coordination of a central terrestrial controller. From this perspective, the number of the SDN controllers and their placement are of paramount importance. A multi-controller placement strategy is evaluated for theintegratedT/NTN using the Simulated Annealing (SA) plus Tabu Search methods to search for the optimal solution in terms of average latency and SDN controllers load, while accounting for the frequent topology variations inherent to LEO satellites. In addition, the design of the SDN architecture for an integrated T/NTN system, and in particular the definition of a distributed SDN control plane (CP) across both the terrestrial and satellite segments, including the specific mechanisms required to enable LEO satellites to operate as controllers, is also addressed. Extensive simulations based on realistic T/NTN topologies, specifically, the terrestrial Agis network and the Iridium NEXT satellite constellation, show that the use of multiple controllers in optimized placements both in terrestrial and satellite segments decreases the average latency and balances the load of each controller. In addition, the proposed controller switching policy adopted for the LEO segment helps to avoid frequent reassignments and improves the reliability of the overallintegratedsystem.

Software-Defined Networking (SDN) represents a disruptive paradigm with significant potential to enhance the Internet of Things (IoT) wireless domain. However, the design and implementation guidelines for this advanced framework remain an open challenge. While adaptation of centralised protocols for low-power wireless sensor and actuator networks (WSANs) led to basic Software-Defined WSAN (SDWSAN) architectures, this approach exhibits notable limitations, particularly in large-scale and dynamic scenarios. For instance, the centralised SDN controller does not only introduce a Single Point of Failure (SPoF) for the managed network but also generates substantial overhead due to control protocols and messages (often inspired by the OpenFlow standard), which can significantly degrade Data Plane (DP) performance. This paper addresses these challenges by proposing Software-Defined Hybrid Dual Stack (SOHS), a novel hybrid architecture that integrates the distributed nature of traditional WSANs within a centralised SDN management framework. By harmonising these paradigms, SOHS optimises scalability and adaptability. Furthermore, we conduct a comprehensive comparison of the proposed hybrid dual-stack control plane architecture against existing alternatives (specifically SDN-WISE, IT-SDN, and uSDN frameworks) evaluating key metrics such as availability, overhead, and end-to-end delay. Our analysis demonstrates that SOHS achieves significant performance improvements, particularly in large-scale networks with dynamic topology changes.

The modern vision of “smarter” factory processes requires the adoption of Industrial Internet of Things (IIoT) ecosystems, where the large scale use of sensors, actuators, and connected devices enable a high amount of heterogeneous data gathering and sending to data centers for analysis and monitoring purposes. However, the foundation of the Web of Industrial Things (WoIT) faces open issues due to the constraints imposed by the involved devices, the technological heterogeneity, and the complex interactions and, hence, communications patterns. Toward this paradigm, a general framework inspired by the software defined networking (SDN) principle have been here proposed, in order to jointly optimize the application requirements by minimizing end-to-end delay and, thus, prolonging the lifetime of the IIoT ecosystem. This article derives a general SDN based architecture to handle data flows in order to support industrial applications that extend the basic publish-and-subscribe scheme. Specifically, the MQTT-SN standard have been considered, since it represents a solution suited for WoIT in the presence of resources constrained devices. The proposed integrated solution has been validated in practical scenarios, pointing out remarkable performance w.r.t. the end-to-end message delivery latency, always with a limited overhead.

Satellites and aerial platforms can be significant in the development of new telecommunications networks, allowing to deploy networks with extremely high performance even in remote areas. Recently, considering the development of quantum communication technologies, many studies are concentrated on Free Space Optic (FSO) Non-Terrestrial links, also considering that the studies performed so far on Optical Fibers (OFs) have not pointed out significant results, especially in terms of coverage. Moreover, the decrease of launch costs and the use of new satellite technologies such as CubeSats make the deployment of satellite constellations affordable. Thanks to the deployment of Non-Terrestrial Quantum Networks (NTQNs), the novel services offered by the Quantum Internet (QI) could be made easily accessible to all. In particular, Quantum Computers (QCs) can perform beyond the capabilities of any classical processor, and the interconnection of these devices on a global scale makes it possible to achieve extremely high computational capabilities, thus opening the way to new applications, such as Quantum Cloud (QCloud). Therefore, the recent studies in this area motivate this survey, which in addition to providing some base concept of quantum information, describes the current technologies needed to create quantum NT backbones. Specifically, this survey examines some studies over the period 2010–2023, which are related to the realization of quantum communications using satellites and other aerial platforms such as High Altitude Platforms (HAPS) and quantum drones. Some of the architectures that are described in this survey make use of the Software-Defined Networking (SDN) paradigm, which can be envisaged as a key enabler for the management of heterogeneous QNs in general. Furthermore, through the description of various experiments, the paper shows the applications that can be enabled by the future quantum NT backbones. In particular, in addition to improving the security of current systems through the Quantum Key Distribution (QKD), it could be possible to interconnect clusters of QCs over long distances and create extremely reliable positioning systems. Finally, the paper outlines some possible future developments.

This paper describes the integration of Terrestrial and Non-Terrestrial Networks, wherein space-based network entities collaborate with traditional and emerging terrestrial communication frameworks to furnish pervasive, resilient, and three-dimensional wireless connectivity worldwide toward the 6th Generation of communication networks. This integration supports heterogeneous services, such as enhancing coverage, user experience, system capacity, service reliability, and availability, while also providing high-speed connectivity in remote or disaster-affected areas, improving existing 5th Generation technologies. Various Use Cases are detailed, highlighting the pivotal roles that Non-Terrestrial Networks play in distinguishing between urban/suburban and rural environments, with particular emphasis on transportation ecosystems. Through this analysis, Key Performance Indicators and requirements are delineated to characterize the requisite service quality for these diverse Use Cases. The paper further presents an overview of potential and standards-compliant integrated Terrestrial/Non-Terrestrial architectures, delineating their roles both in backhauling and access across different layers of Non-Terrestrial systems and elements. These insights are derived from studies conducted within the Integrated Terrestrial And Non-Terrestrial Networks (ITA-NTN) project, part of the European Union initiative defined as the Italian National Recovery and Resilience Plan (NRRP) RESTART Research Program.

In the recent year, quantum computing and communications (QCC) represented two revolutionary technologies that are rapidly developing and integrating to interconnect heterogeneous quantum devices within the so-called Quantum Internet (QI). Despite several investigations and developments have been performed on terrestrial quantum communications over typical optical fiber links, there are some limitations in terms of extremely high losses that can be faced by deploying several repeaters, which in turns involves impractical costs for network management, especially in terms of forwarding procedures. Quantum Satellite Networks (QSNs) is capable to overcome the constraints of terrestrial optical networks, i.e., the remarkable attenuations over long distances which makes the intercontinental communications unaffordable. The recent technological developments in terms of quantum satellite communications motivated our investigation on an ad hoc quantum satellite backbone interconnecting quantum on Earth Servers in order to achieve an unprecedented computational capacity. Our aim is to investigate existing constellations, spanning from Low Earth Orbit (LEO) up to micro-satellites, to properly derive some guidelines for designing an efficient backbone. Specifically, the focus is on evaluating the impact of forwarding approaches on the end-to-end capacity (i.e., the entanglement generation rate) to achieve a trade-off between performance and cost.

This paper analyzes the end-to-end delay performance in an edge-computing scenario where a set of Internet of Things devices (IoTDs) access the computation facilities of an Edge Node by means of a 5G based network. In particular, the paper deals with a two power levels slotted Aloha non-orthogonal-multiple-access (NOMA) scheme and formulates a stochastic end-to-end delay bound, in terms of complementary cumulative probability distribution, by resorting to the application of the martingale theory. In order to validate the proposed analysis, the paper proposes comparisons between the achieved analytical predictions and actual values derived by resorting to extensive computer simulations. Furthermore, the well known Boole bound has been formulated and compared with the proposed Martingale approach to highlight the better behavior of the proposed solution.

The increasing diffusion of smart devices has triggered new Internet of Things (IoT) applications, where communications patterns are often in an autonomous mode. Key enabling technologies, such as relaying communications, cell size reduction and multicast communications have been identified to bring the next‐generation IoT to a complete fruition. In particular, the use of relay nodes is expected to be useful for coverage and capacity improvements, as well as to support point‐to‐multipoint services for data disseminating to subscribers communities. To this end, this study proposes a dynamic quorum links selection (DQ m ) procedure to optimise the throughput for the case of buffer‐aided relaying multicast communications. A theoretical analysis based on the Markov chain framework is provided and validated through simulation results in terms of multicast throughput and relay buffer occupancy for different sizes of the multicast group. The advantages of the proposed DQ m procedure have been highlighted by comparing the achieved performance with respect to classical conventional relay scheme. Finally, a protocol for channel state estimation is presented and the impact of the requested overhead on the performance of DQ m procedure is shown.

Securing Internet of Things (IoT) devices and protecting their applications from privacy leaks is a challenge, due to their weak (computational and storage) capabilities, and their proximity with sensitive data. Considering the resource-constrains of such devices, their long lifetime, and the intermittent connections, classical security approaches are often too difficult or impractical to apply. Moving target defense is an established technique whose goal is to lower the attack surface to malicious users by constantly modifying device footprint. Changing the address to an IoT device without privacy leaks is, however, a nontrivial task. In this paper, we propose a novel method to perform a network-wide (Internet protocol and medium access control) address shuffling procedure, called address shuffling algorithm with HMAC (AShA), which is simple to implement, and whose network overhead is minimal. To demonstrate its effectiveness, we analyze our approach via theoretical analysis and simulations. Our analysis shows how AShA parameters can be adapted to various network sizes while our simulations results show how AShA can be used to successfully perform a global collision-free address renewal on networks of more than 2000 nodes using 16-bit addresses.

This paper proposes a channel allocation scheme for Wide-Area Low-Rate Wireless Personal Area Networks (LR-WPAN) based on a cooperative centralized spectrum sensing approach. We refer here to a three-tiers LR-WPAN architecture, where we can distinguish the sensor devices level, the Child-coordinators level and, finally, the super LR-WPAN coordinator level. In the proposed scheme, channels allocation is performed by the LR-WPAN coordinator upon receiving the spectrum sensing reports from the Child-coordinators. The performance of the proposed scheme is evaluated in terms of resulting detection probability and throughput, in a scenario where Industrial, Scientific and Medical (ISM) bands are saturated and different LR-WPANs compete to the channel access. Performance comparisons with a classical scheme where the channel allocation is accomplished without performing spectrum sensing, are also presented in order to highlight the advantages of the proposed scheme.

With the increasing use of Wireless Sensor Networks, the privacy of the user is of main concern. The sensors maintain a layer 2 address that lasts for the node lifetime. As a consequence, an eavesdropper can easy trace the user and his activities, even in case the nodes send ciphered traffic.We propose a 6LoWPAN-ND extension to improve privacy and overcome the traceability of the user. With our method all the nodes change periodically all their addresses, both at layer 2 and 3. The method requires a small overhead and leverages on existing 6LoWPAN messages. The security is analyzed to show the effectiveness of our work and its energy requirements.

Simple connectivity and data requirements together with high lifetime of battery are the main issues for the machine-to-machine (M2M) communications. 3GPP focuses on three main licensed standardizations based on Long Term Evolution (LTE), GSM and clean-slate technologies. The paper considers the last one and proposes a modified slotted-Aloha method to increase the capability of supporting a massive number of low-throughput devices. The proposed method increases the access rate of users belonging to each class considered in the clean-slate standard and consequently the total throughput offered by the system. To derive the mean access rate per class, we use the Markov chain approach and simulation results are provided for scenarios with different data rate and also in terms of cell average delay.

Device-to-device (D2D) communications enable the proximity communications among users with or without the use of the network infrastructure. D2D communications can increase the overall spectrum efficiency and reduce the power consumption thus a massive utilization of D2D is expected in the future 5G networks. The paper proposes a D2D resource allocation method based on the reuse of primary uplink resources. The method guarantees both a fixed quality of service (QoS) for D2D communication as well as the assigned QoS for cellular communications. It relies on the estimation of distances of all the actors related to D2D position: D2D pairs, base station and the primary devices. These distances are used to evaluate the minimum D2D transmission power which guarantees the D2D reception and jointly produces a controlled and acceptable level of interference on the primary system. The performance of primary system achieved by the proposed method is compared with the one of an unaware interference approach. The results obtained for the scenario with a D2D pair show how the method can limit the interference on primary system. For the scenario with different D2D pairs, the results highlight a better scalability with respect to the other method.

This paper proposes and compares different policies to perform the optimal link selection in the presence of buffer-aided relay for multicast communications. These policies are based on the knowledge of the instantaneous link quality indicators as well as the status of the relay buffer, and dynamically select the more suited link according to a deterministic or random criterion, whose parameters are optimized via a Markov chain theoretical framework. The performance for all the proposed methods are analytically derived and validated through intensive computer simulations for different multicast scenarios. The advantages of the proposed schemes are pointed out in terms of multicast throughput, buffer occupancy for different buffer size and multicast group size.

A simple diamond half-duplex relay network composed of a source, two decode-and-forward half-duplex relays, and a destination is considered, where a direct link between the source and the destination does not exist. For this network, we study the case of buffer-aided relays, where the relays are equipped with buffers. Each relay can receive data from the source, store it in the buffer, and forward it to the destination, when the channel conditions are advantageous. Thereby, buffering enables adaptive scheduling of the transmissions and receptions over time, which allows the network to exploit the diversity offered by the fading channels. For the considered half-duplex network, four transmission modes are defined based on whether the relay nodes receive or transmit. In this paper, we derive the locally optimal scheduling of the transmission modes over time and investigate the achievable average rate, when the relays are affected by inter-relay interference. Since the proposed buffer-aided transmission policies introduce unbounded delay, we provide a sub-optimal buffer-aided transmission policy with limited delay. Moreover, for inter-relay interference cancellation, we consider two coding schemes with different complexities. In the first scheme, we employ dirty paper coding, which entails a high complexity, whereas in the second scheme, we adopt a low-complexity technique based on successive interference cancellation at the receiving relay nodes and optimal power allocation at the transmitting nodes. Our numerical results show that the proposed protocols, with and without delay constraints, outperform existing protocols for the considered network from the literature.

A simple diamond half-duplex relay network composed of a source, two half-duplex relays, and a destination is considered, where no direct link between the source and the destination is exists. For this network, we investigate the achievable rate when the relays are equipped with buffers. Buffer-aided relays can receive data from the source, store it in their buffers, and forward it to the destination when the channel conditions are more advantageous. Thereby, buffering enables adaptive scheduling of the transmissions and receptions over time, which allows the network to better exploit the diversity offered by the fading channel. For the considered network, because of the half-duplex relays, four transmission modes are employed based on whether the relay nodes receive or transmit. Considering these four transmission modes, in this paper, we derive the optimal transmission mode selection policy such that the received data rate at the destination is maximized. Furthermore, based on numerical examples, we show that the proposed protocol outperforms the existing protocols for the considered network in the literature.

This paper proposes an energy efficient antennas allocation method for network-coded MIMO multicast communications. By means of the definition of a suitable objective function it is shown that it is possible to select the optimal number of antennas in transmission/reception and the most convenient modulation scheme in order to minimize both the overall mean energy consumption and delivery delay. Simulation results are provided in the paper in order to validate the proposed optimization method and to highlight its advantages in comparison with similar rate-based approaches already proposed in literature, where symbol error rate is evaluated as a comparing metric for MIMO performance.

Confidentiality of the communication is extremely important in wireless networks due to the broadcast nature of the radio channel. The secrecy of the communication can be achieved via secure PHY layers or by using crypto techniques which need a pre-shared secret between the sender and the legal receiver. A technique has been proposed in literature to avoid preshared secrets based on the noise-pattern of the radio channel. However, when the channel frequency selectivity is low or the eavesdropper is located near to the victim, the key exchange may fail to achieve security. The eavesdropper can gain access to the secure communication and steal the identity of one of the two communicating nodes. In this paper, a technique for identity theft detection is proposed: the receiving node can detect unintended change of sender's identity. A Feed-Foward Neural Network is used to identify the non-linearities of the OFDM radio transceiver which are unique and characteristic of the transmitting and receiving devices. The simulation results show that the NN correctly detects the non linearities coefficients for pedestrian and high mobility terminals in the presence of severe fading and noise, providing a strong mean for radio signal identification to detect broken security.

Location awareness in wireless sensor network (WSNs) application is often too expensive to be achieved by endowing each node with use a GPS receiver. Approach based on range-free methods, where nodes can estimate their location basing on neighbors and nodes that known their position (anchors), can be envisaged. This paper deals with the optimization of APIT algorithm in wide area WSN scenario for critical scenarios applications.

HSDPA (High Speed Downlink Packet Access) is drawing great attention as the 3.5G technology capable of providing higher data rate packet switch services over Universal Mobile Telecommunication System (UMTS) to support broadband services like multimedia conferencing, VoIP, or high-speed internet access. The paper proposes the use of a Learning Vector Quantization (LVQ) Neural Network able to estimate the quality of service (QoS) across analysis of Key Performance Indicators (KPIs) and to provide automatically a possible classification of warnings related to the load status of HSDPA radio resources or to the bad radio channel quality condition.

Cooperative Localization of rescue entities (persons and means) is essential in emergency situations.The identification of the Direction of Arrival (DoA) of the different users can simplify the knowledge of the position of users improving advanced cooperative localization methods and the global network management. DoA techniques can be applied by using antenna array systems. In literatures many efforts are focused on the optimization problem for antenna array with elements uniformly spaced at integer multiples of a suitably chosen basic spacing. Antenna array with non uniformly spaced elements (sparse array) are interesting but the unequally spaced positions of elements lead to a nonlinear optimization problem. In the paper, an integration of evolutionary techniques, such as genetic algorithms (GAs) with the use of antenna array systems is analyzed to optimally identify the DoA signals in different antenna configurations. Results are also provided for the case of sparse array with elements randomly placed in a specific region of space.

Abstract This paper deals with an efficient secure communication system based on a speech watermarking approach. The main goal of the system is to efficiently support air traffic control (ATC) communications by improving safety and security of the existing ATC equipment embedding digital side information into speech signals in order to allow anautomatic identification of the talker. An implementation based on the use of the well known LPC (linear predictive coding) principle is discussed. The LPC residual is split up into voiced and unvoiced segments; while the voiced segments cross the system unmodified, the watermarking data are embedded into the unvoiced segments, spectrally similar to a white noise. The watermark signal is decoded by a very similar scheme. We provide also a statistical analysis on the unvoiced parts of the ATC communications that demonstrates the system feasibility. In addition to this, an optimization of the entire system has been also performed to increase performance. The obtained results highlight that the watermark data are nearly imperceptible and providea data channel with rate from 2000 to 5000 kbits/s, withhigh robustness to channel noise; the system requires only modular, low‐cost and easy‐to‐install encoders and decoders, maintaining compatibility with legacy RF DSB‐AM transceivers. Moreover, it is well suited both for the actual 25 kHz RF channels and for the new 8.33 kHz European RF channels. Copyright © 2008 John Wiley & Sons, Ltd.

This paper focuses on the problem of ensuring quality of service (QoS) to 4G network users. An adaptive cross-layer (ACL) strategy, that jointly optimizes the parameters of physical (PHY) and medium access control (MAC) layers using queueing theory, is proposed and applied to mobile user communications in an OFDM-based wireless network. PHY and MAC layers are referring to IEEE 802.16 standard, supporting, respectively, different modulations and the automatic repeat request (ARQ) protocol. PHY and MAC layer parameters are here optimally combined by ACL strategy to meet the QoS requirements. The main contribution of the paper is the evaluation of the impact of mobility on ACL strategy performance, by using an accurate channel model that accounts for shadowing effects. The simulation results show that the ACL strategy outperforms non-adaptive or single-layer strategies, in terms of bandwidth savings. Also, ACL strategy is able to guarantee the requested QoS in the different mobility scenarios with different degrees of performance.

In this paper, a selection of different multiantenna (MIMO) systems will be presented. The adopted MIMO configurations with four and two transmit antennas and two receive antennas are selected according to the IEEE 802.16e standard: diversity scheme, hybrid diversity scheme and spatial multiplexing. Computer results present an adaptive selection strategy among the considered MIMO schemes along with their performance.

Recent research addresses towards multitransmit, multireceive antenna scheme to improve the performance in high data rate wireless communications. In this paper, we examine the combination of Bell-Labs layered space time (BLAST) wireless architecture and the iterative demapping and decoding, the turbo decoding principle. This structure, known as T-BLAST, was evaluated according to the IEEE 802.11b standard requirements for wireless LAN. The paper considers the design of the modified 'soft' Complementary Code Keying (CCK) modulation/demodulation scheme more suitable for the iterative interference cancellation receiver and shows the performance evaluation of this T-BLAST and SOFT CCK MODEM in the specific environment of the IEEE 802.11b standard. The paper also presents the throughput versus distance to receiver varying the number of transmit antennas in the indoor environment.

The availability of broadband networks and the advent of standards and technologies for real time multi-point communications allow a new educational system. The paper describes a live remote educational service in satellite/terrestrial environments and an educational tele-medicine service in the Ku/Ka band.

The paper presents a Euclidean distance maximum likelihood sequence estimation (MLSE) receiver, based on the Viterbi algorithm (VA), suitable for fading and noisy communications channels, as that specified by the Group Special Mobiles (GSM). In a mobile cellular system, the fast varying channel characteristics, due to the fading and Doppler effects, require adaptive methods to update the channel coefficients to the MLSE receiver. The proposed technique continuously estimates the channel characteristics directly within the metric calculation of the VA. At each step of the VA, the sequence associated to the path with the best metric value (minimum-survivor method) among the survivor paths is used to update the channel estimate (employing conventional adaptive algorithms) throughout the entire informative sequence. However, the detection of the transmitted data sequence is performed by the VA only at the end of each burst. The proposed technique allows simpler receiver implementation and the simulation results show a good performance of this adaptive MLSE receiver in typical GSM environments.

Neural networks have been successfully applied in many fields thanks to their learning and generalization capabilities and to the parallel processing and fault tolerance properties. Typical applications concern images processing, pattern recognition and digital signal processing, such as adaptive filtering and channel equalization. The authors propose the use of neural networks as digital receivers for continuous phase modulation (CPM). Simulation results refer to the European GSM digital cellular radio system. The neural receiver performance has been evaluated for coherent detection, considering an additive white Gaussian noise (AWGN) channel and compared with a maximum likelihood sequences estimator (MLSE) receiver based on the Viterbi algorithm. The paper also presents a hardware implementation of the proposed network based on a digital signal processor (DSP) and on a programmable gate array (PGA).>

A simplified structure concerning the implementation of an adaptive digital receiver suitable for the pan-European cellular system Group Special Mobile (GSM) is described. In the GSM system, the performance of the received information is strongly affected by the multipath typical of the mobile communications channel. The proposed maximum-likelihood sequence estimation (MLSE) receiver based on the Viterbi algorithm compensates for selective distortion due to the multipath propagation and Doppler shift also in the case of fast channel variations using an adaptive tracking mode method.>

The authors present a multi-DSP (digital signal processing) system based on commercial chips. The structure is a MIMD (multiple-instruction multiple-data) machine with a data-driven organization. A locally parallel link based on a memory shared between two adjacent nodes assures the asynchronous exchange of data. The system is also characterized by a global serial channel useful for program-loading purposes and noncritical data paths. A mathematical model is used to evaluate the performance of the multi-DSP system. The apparatus is used in ultrasound Doppler parameter estimation but the processing architecture is suitable for general real-time applications.>