The HORSE (Holistic, Omnipresent, Resilient Services for future 6G wireless and computing Ecosystems) framework integrates AI to address the complexity and vulnerabilities of next-generation networks. This paper focuses on an LLM-agent-based subsystem of HORSE that automates the creation and enforcement of security mitigation actions. This subsystem utilizes a specialized Knowledge Base enriched with threat-mitigation pairs from trusted sources like MITRE ATT&CK, through a collaborative workflow between an LLM and human expertise. LLMs translate high-level mitigation actions into executable Ansible commands, while a feedback-driven workflow, powered by LLM agents, ensures accuracy and reliability. One LLM agent (the "translator") generates the commands, while another (the "executor") executes them and provides feedback to the translator in case of unsuccessful execution, allowing the translator to refine the commands for a retry. Experiments with open-source LLMs (like Llama 2 and Falcon) demonstrate rates of up to 73% in execution success, and high accuracy in translating mitigation intentions. This approach automates threat mitigation, reduces human intervention, and scales effectively for the dynamic security demands of 6G networks. Future work will focus on enhancing LLM capabilities for complex environments and improving adaptability in cybersecurity operations.

This paper proposes a scheme for rapidly deploying a UAV-enabled emergency cellular network (UECN) in disaster scenarios, such as earthquakes or floods, to support rescue operations. The unsupervised placement of UAV aerial base stations (ABSs) is achieved through machine learning (ML) techniques. Specifically, the k-medoids algorithm is utilized to cluster ground users in the disaster area and determine the minimum number of ABSs and their position. ABS's altitude is defined based on its capacity capabilities and propagation environment. The UECN cooperates with undamaged cellular infrastructure via joint coordinated multipoint transmission and reception (CoMP) with neighbouring functional terrestrial macrocell base stations (TBSs) to improve end-user signal quality. Finally, the proposed scheme is comparatively evaluated through simulation, and the results demonstrate its efficiency even in the presence of users and ABSs positioning errors.

This article proposes a new approach to the design and assessment of Internet of Things (IoT) systems. Specifically, it identifies the principles that can be derived from the financial technology ecosystem and should be considered when designing an IoT system in order for it to be technically sound, economically efficient, and have the best market acceptance prospects. Considering a specific area of IoT systems, that of the smart agriculture, we then examine whether the proposed design principles are followed by the current state-of-the-art systems. Furthermore, we claim that our proposal can also be utilized as a more comprehensive basis for assessment in comparison to the technology readiness level, which indicates only the technological readiness of a project without grading its market potential.

Nowadays, various techniques and systems have been proposed for the implementation of wireless indoor localization systems. Recently, significant focus has been given to Multiple Input-Multiple Output (MIMO) implementations of Ultra-Wideband (UWB) systems, in order to enhance the localization precision while introducing high communication performance. The main disadvantages of such approaches are the high deployment cost and computational complexity, due to the increased data processing. These facts are compensated by adopting the Time Reversal (TR) transmission scheme, providing scaling capabilities and Spatial Focusing (SF) to the system, at the same time. In this paper, a 2 × 2 Multi-Antenna Time-Reversal Indoor Positioning (MATRIP) system model is proposed to track the mobile Blind Node (BN) in a harsh indoor environment, measuring its time-range from one fixed-position Anchor Node (AN). This kind of implementation overcomes the restrictions imposed by the legacy localization systems, regarding the minimum number of ANs of the system. The efficiency of the MATRIP system is demonstrated through simulation results evaluating the average localization error versus the Signal to Noise Ratio (SNR), the Focusing Gain (FG), and the channel capacity.

The knowledge of direction information of the transmitted signals requires angle-based position estimation techniques, as well as the orientation of the individual nodes of the system. When using omnidirectional antennas, this information is difficult to be calculated in order to find the Blind Node's (BLN or BN) position. Also, the combination of Ultra Wide-Band (UWB) systems with angle-based techniques is not the best option when tracking down an unknown target, especially indoors, due to the large bandwidth of the UWB signals and the huge number of paths. This paper proposes a geometrical angle-based positioning approach for UWB omnidirectional systems which also combines Fingerprint (FP) and Time-of-Flight (ToF), aiming to calculate the BN's position with the minimum positioning error. The efficiency of the proposed positioning scheme is demonstrated through simulation results in terms of error probability and comparisons with other state-of-the-art positioning schemes.

The paper considers a two-way relay network with network coding capabilities and an additional mechanism based on timeouts, used to ensure stability and bound the mean delay experienced by packets through the relay. Modeling of this system leads to simple closed form expressions that illustrate clearly the impact of the timeout parameters on the performance and efficiency metrics associated with the network coding operation. These results are subsequently employed for optimally tuning the timeout parameters, towards achieving the greatest network coding efficiency (and the corresponding throughput and energy efficiency improvement) that is possible for the given traffic profile, subject to a delay-related QoS requirement. Again, simple closed form results are obtained that support intuition and provide additional insight on the involved tradeoffs.

One of the most challenging requirements in cutting-edge Mobile Ad hoc Networks is the need for adaptive and efficient routing. Networks capable of adapting their behavior based on current conditions are often characterized as self-organizing networks, which are lately considered very promising for future applications. This work examines the impact of the different mobility properties on the performance of self-organizing networks. For that purpose, a simulator was developed to model different mobility patterns and study the way they affect the effectiveness of the well-known AODV routing protocol. Particularly, this paper focuses on the effect of the different mobility schemes on network topology and consequently to the overall network performance. The results reveal the tight correlations between node mobility characteristics and network metrics.

ABSTRACT In high‐speed downlink packet access (HSDPA), the combination of adaptive modulation and coding, hybrid automatic repeat request, and an extended multicode operation has replaced two fundamental aspects of wideband code division multiple access systems, namely, variable spreading factor and fast power control. Despite its enhanced characteristics, the HSDPA operation can be problematic when the majority of incoming traffic load consists of low data rate delay‐sensitive services such as mobile voice‐over‐Internet Protocol. To tackle this case, we propose an enhanced HSDPA operation that exploits multiple layers of the channelization code tree through a specifically designed packet scheduling and code allocation process. Enhanced HSDPA, when compared with the conventional HSDPA, provides a more flexible sharing of the available capacity and is able to increase the number of users that can be served with the required quality of service in terms of packet delay. The efficiency of the proposed scheme is confirmed by simulation results. Copyright © 2011 John Wiley & Sons, Ltd.

In this paper, we exploit the characteristics of physical layer network coding (PNC) in multicast short range communication (SRC) networks. We present a scalable scenario of partially overlapping SRC networks, where collisions are resolved through indirect inter-group cooperation based on the features of PNC. Our scenario consists of a central network and several peripheral networks. In our previous work we proved that the central network presents significant gains in terms of throughput, delay and energy efficiency when applying the proposed scheme. Here we explore the impact of that scenario on the peripheral networks through a decomposition approach and we prove that they also present significant performance gains.

In this paper we present an analog-network-coding-aided layout for data dissemination. We propose a game theoretic Medium Access Control (MAC) protocol that exploits the recent developments in network coding domain to enhance the system performance. In particular, random linear network coding is used to eliminate the need of exchanging control packets, while ZigZag decoding techniques are applied to resolve the data packet collisions. Our proposed protocol is proved to enhance both the provided Quality of Service and the energy efficiency of the system.

The paper presents an infrastructure-based cognitive radio network architecture that enables for TV white spaces exploitation, QoS provisioning and policy management, under the real time secondary spectrum market policy. It describes the configuration of a spectrum broker that coordinates the radio resource management process (RRM) among LTE secondary systems as a matter of maximum possible TVWS utilisation and minimum frequency fragmentation, and also administrates the economics of such transactions towards maximum revenue following a fixed-price trading. The validity of the proposed architecture is verified via a number of tests carried under controlled experimental conditions (i.e. simulations) exploiting a decision-making algorithm.

In this paper we introduce a novel Medium Access Control (MAC) protocol for Automatic Repeat reQuest-based (ARQ-based) cooperative wireless networks. Our protocol coordinates the channel access among a set of relays that use network coding techniques to minimize the number of total transmissions, thus enhancing the performance of the network in terms of Quality of Service (QoS) metrics. The proposed solution is compared to other cooperative schemes, while analytical and simulation results are provided to evaluate our protocol.

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.

This paper discusses a Distributed Network Quality of Service (NQoS) provision approach in decentralized interactive DVB-T systems (IDVB-T), enabling for scalable and fault tolerant operation. The paper describes the design and overall architecture of a regenerative IDVB-T infrastructure, where network resource allocation and service classification processes are performed at local level within each intermediate distribution node (Cell Main Node CMN), setting the basis for a CMN-to-CMN NQoS provision. Validity of the proposed approach is experimentally verified, and the test-results are compared against the aggregated and federated NQoS provision approaches, indicating similar performance but better scalability and fault-tolerant design.

It is widely accepted that cloud computing technologies will soon have substantial impact on a broad range of industrial and institutional sectors such as governance, health care, education, agriculture, logistics, manufacturing, media etc. Cloud infrastructures are typically based on virtualized environments to allow physical infrastructure to be shared by multiple and diverse end users. However, the efficient sharing of a cloud infrastructure can be performed only through user-centered service admission control procedure, which should also be flexible enough to adapt to the various real market cloud deployment scenarios. Several conflicting parameters such as the type of the hybrid cloud infrastructure being deployed, multiple user priority groups, security, energy efficiency and financial costs should also be taken into account. Thus, aiming to deal with all these emerging resource management trade-off problems, we propose in this paper a user-oriented, highly customizable infrastructure sharing approach, namely IaaS Request Admission Control (IRAC), designed for Hybrid Cloud Computing Environments.

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.

Cognitive Wireless Ad-Hoc Networks use cooperation in order to sense the spectrum accurately. However, the space diversity provided by the cooperative sensing is only efficient when the sensing users are selected appropriately. This paper proposes a distributed probability-based mechanism that allows the Secondary Users to decide what channels should be sensed by each user in order to reduce the sensing overhead.

In this paper we analyze the performance of a distributed queuing medium access control (MAC) protocol designed to execute cooperative ARQ (C-ARQ) schemes at the MAC layer. Due to the broadcast nature of the wireless channel, a user that receives a data packet with unrecoverable errors can request retransmission from any of the other users in the transmission range of the transmitter that overheard the original transmission. These users can act as spontaneous relays and provide the communication with cooperative diversity gains. Upon retransmission request, the relays have to contend for the access to the channel. The DQCOOP protocol has been proposed in the literature as a high-performance MAC protocol for this kind of scenario. In this paper we theoretically evaluate its performance. The analytical results are supported by computer-based simulation that show the accuracy of the analysis.

In this paper we introduce a connection admission control (CAC) mechanism for IEEE 802.16 broadband wireless access standard. Our scheme is based on the bandwidth reservation concept and has been developed considering the problem of "busy hour" in communications traffic variation during a typical day. The proposed solution, which is compatible to the IEEE 802.16 Standard, provides higher priority to VoIP calls compared to other types of traffic in the network. The performance of the proposed mechanism is evaluated by means of computer simulations and compared to simple traditional admission control schemes, while we provide an analytical solution as well.

This paper presents a novel DVB/IP infrastructure that exploits P2P technology for optimised resource exploitation in interactive services' provision. Building upon a prototype DVB-T regenerative platform, it presents a decentralised architecture that exploits the broadcasting stream as part of the core/backbone network, providing interactive IP services to rural/urban citizens. Users access the provided IP services via intermediate communication nodes (access network), which are responsible for managing/controlling both uplink and downlink flows. Towards enhancing the scalability as well as the performance of the entire network, the paper studies the realisation of IP overlays by exploiting P2P technology, and proposes a prototype configuration for optimum resource exploitation and increased Service/Bandwidth gain both at the core and access segments. Performance evaluation experiments carried-out under real transmission/reception conditions verified the validity of the proposed architecture, besides outlining fields for future research.

Abstract The integration of wireless sensor networks with different network systems gives rise to many research challenges to ensure security, privacy and trust in the overall architecture. The main contribution of this paper is a generic security, privacy and trust framework providing context‐aware adaptability, flexibility and scalability which allows customisation of wireless sensor networks to a diverse set of application spaces. Suitable protocols and mechanisms are identified, which when combined according to the framework form a complete toolbox solution which fits the architecture of Beyond 3G environments. Performance evaluation results demonstrate the feasibility and estimate the benefits of the security framework for a variety of scenarios. Copyright © 2008 John Wiley & Sons, Ltd.

This paper provides details and performance evaluation of the implementation of the Persistent Relay Carrier Sensing Multiple Access (PRCSMA) protocol for Cooperative ARQ (C-ARQ) scenarios using off-the-shelf wireless cards. The underlying idea of PRCSMA is to modify the basic rules of the IEEE 802.11 MAC protocol to execute a distributed C-ARQ scheme in wireless networks in order to enhance their performance and to extend coverage. For the implementation, we modify the HostAP driver for off-the-shelf air-interfaces. HostAP is a Linux based driver for 802.11b WLAN cards based on Intersil's Prism 2.5. Performance evaluation tests provide proof-of-concept of the efficiency, in terms of mean delay, of the PRCSMA in realistic conditions.

It is widely recognized that next generation wireless networks will integrate heterogeneous wireless technologies. Nowadays, the borders among the different wireless network technologies are quickly disappearing. UMTS and WLAN, a popular and representative interworking paradigm, provides a plethora of multimedia services to mobile users with multimode access capability. In this paper, we propose an effective call admission control (CAC) scheme which is based on a multi- threshold bandwidth reservation scheme. Our primary goal is not to develop the optimum CAC algorithm; we want to investigate all the real future market parameters, so that the CAC mechanisms will be flexible enough to face all the possible upcoming scenarios in the next wireless generation era.

The paper targets to demonstrate through a set of experimental studies that the common operation of IP DiffServ and DVB bandwidth management (BM) mechanisms can offer quality gains for prioritized MPEG-4 FGS media delivery across an heterogeneous IP/DVB setting. The experimental studies refer to the delivery of eight YUV QCIF 4:2:0 different video sequences across a heterogeneous IP/DVB testbed that includes two IP autonomous systems interconnected through a DVB MPEG-2 autonomous system acting as a trunk network.

As networks and applications running on them become more complex, there is a need for an efficient framework supporting experimental performance evaluation based on real measurements. Towards this end, this paper presents: a) an advanced architecture for a traffic generation tool capable of producing complex traffic profiles, b) the architecture of a traffic analysis tool, and c) methods that allow for efficient monitoring and measurements of delay and loss-oriented metrics in packet networks. The effectiveness of these tools and the applicability of the measurement methodology are illustrated through experiments that evaluate the performance of vertical handovers between GPRS and WLAN networks.

Sensor networks are set to become a truly ubiquitous technology that will affect the lives of the people in their application environment. While providing the opportunity for sophisticated, context-aware services, at the same time sensor networks impose great privacy risks. This paper discusses privacy issues in sensor networks, by identifying the requirements for privacy preserving deployments, analysing the challenges faced when designing them, and discussing the main solutions that have been proposed.

The evolution of next generation networking middleware (NGNM) yields to the provision of personalized next-generation active services, each one with different traffic characteristics and networking requirements for security, billing, QoS (Quality of Service), mobility, etc. in an efficient and economical usage of network resources. The introduction and well establishment of the active services concept, which will be services capable of dynamically adapting themselves to various underlying networking environment conditions according to the instructions of NGNM and the requirements posed by the end user, constitutes the major goal of this paper. In order to avoid proprietary and custom implementation solutions, an initial and generic active services reference architecture that can be followed by potential active services developers is presented. Finally, an implemented prototype that follows the proposed reference architecture provides a first quick validation of the discussed active service concept.

The information theoretic principles of maximum entropy (ME) and minimum relative entropy (MRE) are employed, as least-based methods of inference, for the analysis of single ad hoc systems with bursty arrivals and blocking. The system consists of MAC and IP layer finite capacity links together with a shared medium which forwards from the MAC to the higher IP layer links in a determined fashion. The traffic at each MAC layer link is assumed to be bursty and is modeled by a compound Poisson process with geometrically distributed batches. The shared medium provides generalized exponential (GE) type of service whilst each output link forms a single GE-type FCFS server queue. To this end, an approximate MRE decomposition algorithm is proposed for the partitioning of the shared medium with its associated MAC layer links into ordinary finite capacity virtual queues with server vacations and modified service times. Consequently, each queue is analyzed in isolation by exploiting a stochastic relationship between polling time and server vacation. Moreover, the IP layer links are analyzed separately as GE-type finite capacity queues. Finally, the individual building block queues, are combined together via an iterative process which is based on a MRE solution for arbitrary open queuing network models with blocking and GE-type flow formulae.

The information theoretic principles of Maximum Entropy (ME) and Minimum Relative Entropy (MRE) are employed, as least-biased methods of inference, towards the analysis of a Internet link carrying realistic TCP traffic, produced by a large number of connections. The analytic approximations are validated against exhaustive simulation experiments. Despite its simplicity, the methodology captures the behavior of the system under study both in the cases of finite and infinite buffers and finally suggests a more elaborate but still cost effective approach even for the analysis of networks of Internet links. This approach can easily be utilized for network management and design, capacity planning, and congestion control.

Abstract This work addresses aspects relevant to the optimal joint exploitation of heterogeneous wireless networks in an ‘all‐IP’ integrated infrastructure, frequently called ‘Beyond 3G Systems’ (B3G) or composite radio networks. After briefly reviewing general architectural aspects pertaining to such systems, the paper focuses to the management functionality possessed by B3G systems and highlights the benefits that stem from sharing intelligence among the hybrid network (through a network management system) and the multimodal wireless terminals. In particular, the paper discusses an appropriate signaling protocol for the exchange of information between management modules at the network and the wireless terminal, investigates associated performance aspects and correlates the relevant findings with measurement results obtained from experiments over a prototype B3G network testbed. Copyright © 2005 John Wiley & Sons, Ltd.