This paper presents a novel game-theoretic approach for efficient resource allocation in Integrated Access and Backhaul (IAB). We model the interactions between multiple decision-makers as a strategic game, defining the strategy spaces and utility functions for the involved players. By employing potential game theory, we discuss the existence of a Nash equilibrium and propose an iterative algorithm to achieve it. Our proposed solution is evaluated against two baselines, namely Soft Actor Critic (SAC) and Max-Rate Backlog Avoidance (MRBA) demonstrating superior performance in resource efficiency and decision-making precision. These findings offer valuable insights for designing scalable and efficient network management frameworks.

The expanded scope and attack surface of the today’s multi-tier heterogeneous wireless network (MHWN), which constitutes the basis of our daily life activities, dictates a deeper understanding of how distributed Denial of Service (DDoS) attacks can impact its performance. In this work, we assess the performance of large-scale MHWNs that are subject of random DDoS attacks, considering that i) each tier may support a different radio access technology and spectrum band, and ii) end terminals have limited access to available tiers. Depending on the capability of end terminals to perfectly detect DDoS actors (or not), we provide a solid analytical framework for assessing the impact of different user association policies on both the service probability and the user load distribution per tier. Among others, our numerical analysis highlights the importance of striking a good balance between optimal system-wide service probability and fair load distribution across the tiers of the MHWN.

Civil protection exercises are deemed highly effective in enhancing the preparedness of civil protection mechanisms to respond to disasters and address emergency needs. In this context, the Region of Attica conducted the Field Exercise "AENEIAS AA 2023" during the 2023 fire season. The objective was to evaluate the operational plans for forest fire emergencies and improve communication and collaboration among participating agencies. The exercise was held in the Hamolia-Vravrona region, part of the Regional Unit of East Attica. Innovative technologies were utilized to support "AENEIAS AA 2023" including the development of a specialized Geographic Information System (G.I.S) for generating scenario maps and facilitating their sharing.Moreover, the system aided in exercise evaluation through online questionnaires and qualitative result analysis. Unmanned Aerial Vehicles (UAVs-drones) were deployed to gather and transmit ground-level information. This comprehensive approach enriched the experience in Civil Protection exercises, contributing to ongoing endeavors to enhance disaster preparedness in the region.

This paper presents AI-SNIPS (AI Support for Network Intelligence-based Pharmaceutical Security), a production-ready platform that enables stakeholder decision-making, secure data sharing, and interdisciplinary research in the fight against Illicit, Substandard, and Falsified Medical Products (ISFMP). AI-SNIPS takes as input cases: a case consists of one or more URLs suspected of ISFMP activity. Cases can be supplemented with ground-truth structured data (labeled keywords) such as seller PII or case notes. First, AI-SNIPS scrapes and stores relevant images and text from the provided URLs without any user intervention. Salient features for predicting case similarity are extracted from the aggregated data using a combination of rule-based and machine-learning techniques and used to construct a seller network, with the nodes representing cases (sellers) and the edges representing the similarity between two sellers. Network analysis and community detection techniques are applied to extract seller clusters ranked by profitability and their potential to harm society. Lastly, AI-SNIPS provides interpretability by distilling common word/image similarities for each cluster into signature vectors. We validate the importance of AI-SNIPS's features for distinguishing large pharmaceutical affiliate networks from small ISFMP operations using an actual ISFMP lead sheet.

The OPTIMIST project is positioned into one of the most challenging and societal impactful innovation paths, by contributing to the design and implementation of a Multi-access Edge Computing-empowered service platform enabling the optimized delivery of the most popular type of traffic in the forthcoming 5G networks: mobile video. Advanced prediction tools (e.g. data analytics), MEC-enabled service provisioning, 5G networking, QoE-driven and model-based service optimization using stochastic modeling and algorithmic optimization, are major components toward a holistic system that combines analytical tools and close-to-market technologies. In addition, despite the considerable amount of valuable academic research conducted in the area of MEC- enabled service provisioning, the vast majority of obtained results remains hardly compatible (in terms of system models and implementation platforms) and are often limited to the scope of academic research with no envisaged market transfer plans. OPTIMIST fosters fruitful collaboration of academia and industry targeting at developing an innovative platform for fully personalized delivery of 5G mobile video content.

During the last decade, various Internet of Things (IoT) networks have emerged as an effort to support the constantly increasing need for IoT applications. Focusing on IoT networks that use unlicensed spectrum bands, Low Power Wide Area Networks (LPWANs) are being developed widely. For these networks, one of the most effective technologies is the combination of Long Range (LoRa) / LoRa Wide Area Network (LoRaWAN) protocol stack. In this context, we set up a LoRa/LoRaWAN network in a campus environment and we conducted thorough measurements that allowed us to produce link-level performance analysis. More precisely, the relation between key link-level performance metrics, namely the Received Signal Strength Indication (RSSI) and the Signal to Noise Ratio (SNR) was derived, considering i) the heterogeneous terrain where the measurements were conducted, and ii) the configuration parameters selected, such as the Spreading Factor (SF).

Cache- and network-agnostic Dynamic Adaptive Streaming over HTTP creates oscillation dynamics upon delivering mobile video content over cache- and slice-enabled data networks. In this paper, we bring to light the problem of user admission control, end-to-end slicing and video bitrate selection in next-generation 5G and Beyond 5G mobile data networks, where some minimum throughput guarantees can be provided for both the user-to-base-station and base-station-to-content-delivery-network links. Accordingly, we propose an exact algorithm to identify feasible bitrates and their minimum throughput requirements when the multi-access edge computing (MEC) cellular base stations has cached a known subset of video segments, potentially encoded at different resolutions, for a tagged video file. Simulation results provide valuable insights for user admission control, end-to-end slicing, video bitrate selection and caching in slice-enabled MEC-empowered cellular networks.

A fundamental technology towards the next generation of mobile networks is the Network Slicing, i.e., the capability to “slice” network resources and functions and to offer isolated end-to-end network services over shared physical infrastructures. From the performance perspective, one of the main challenges in network slicing is the minimisation of the slice set up time; a factor that directly effects a key performance indicator for the 5G networks, namely, the service creation time. Treating a network slice as a set of Virtual Network Functions (VNFs) that are installed in different hosts (central/edge clouds) during the slice creation procedure, we examine a nature-inspired metaheuristic approach for scheduling the VNFs installation process. Simulation results prove that the proposed metaheuristic method can offer high quality solutions for VNF scheduling problems and optimize service creation time for a set of requested network slices, by producing a close-to-optimal scheduling plan, for a large set of VNFs, in reasonable execution time.

The today's heterogeneous wireless network infrastructure is managed by different stakeholders that allow mobile data access to a prescribed set of end users. This network access model not only enforces end users to accept network-driven service provisioning but also raises critical burdens towards flexible utilization of the numerous 5G network assets (content, storage, radio resources, etc.). In this paper, we investigate on-the-fly user-driven network-assisted mobile video content delivery in 5G and Beyond networks using blockchain technologies enabling multi-million transactions per second. To this end, we present the RE-CENT crypto-currency platform enabling infrastructure providers, end users and content providers to be actively engaged in the blockchain consensus. Detailed discussions on the implementation of the proposed platform through smart contracts are provided and analytical results are used to quantify performance gains of the proposed mobile data access model.

This paper presents an overview of the project CASPER, a Marie Curie Research and Innovation Staff Exchange (RISE) project running from 2016 until 2020. The main objective of CASPER is to combine academic and industrial forces towards leveraging the expected benefits of Quality of Experience (QoE) exploitation in future digital networks. In particular, CASPER exploits the most recent advances in communication networks, such as the Software Defined Networking (SDN) and the Network Functions Virtualisation (NFV) in order to design and implement a middleware architecture for QoE-driven service provisioning. CASPER, therefore, addresses the challenges that mobile network operators and service providers face in the current fully digitalized era of communications, concerning the need to provide customer-oriented, reliable, efficient, flexible and dynamic service management.

Wireless networks are currently proliferated by multiple tiers and heterogeneous networking equipment that aims to support multifarious services ranging from distant monitoring and control of wireless sensors to immersive virtual reality services. The vast collection of heterogeneous network equipment with divergent radio capabilities (e.g. multi-GHz operation) is vulnerable to wireless network attacks, raising questions on the service availability and coverage performance of future multi-tier wireless networks. In this paper, we study the impact of black hole attacks on service coverage of multi-tier heterogeneous wireless networks and derive closed form expressions when network nodes are unable to identify and avoid black hole nodes. Assuming access to multiple bands, the derived expressions can be readily used to assess the performance gains following from the employment of different association policies and the impact of black hole attacks in multi-tier wireless networks.

Nowadays, over-the-top (OTT) applications can be accessed via Internet connections over cellular networks. Mobile network operators (MNOs) strive to accommodate mobile traffic through energy efficient shared networks. The OTT service providers (OSPs) need to interact with MNOs and require resources for offering desired quality- of-service (QoS) levels to users of different categories, with different QoS requirements, which imply prioritization of certain OTT flows. Resource scheduling should respect network neutrality, which forbids OSP prioritization. Furthermore, OSPs request resources periodically, according to their performance goals, causing delay in flows' accommodation due to i) the time required for information exchange between OSPs and MNOs, affected by network congestion, and ii) the time required for flows to receive resources, affected by the number of active flows. The intervention of OSPs may induce additional energy cost for the MNOs and affect the mobile network energy efficiency. Acknowledging the lack of OSP- oriented resource management approaches, we introduce a matching theoretic flow prioritization (MTFP) algorithm and investigate delay and energy efficiency through extensive simulations. Our study shows that MTFP improves both metrics comparing to the best effort approach, whereas its performance is affected by the OTT traffic level and the frequency of resource allocation process.

Presents the introductory welcome message from the conference proceedings. May include the conference officers’ congratulations to all involved with the conference event and publication of the proceedings record.

Over the past years there has been a rapid rise of the mobile communications industry which, combined with the limitations of the current communications networks' structure, necessitates the development of new networks with increased capabilities, so that users can be served with optimal quality of service and network resources utilization. Software Defined Networking (SDN) is a networking approach which transforms the network elements to simple forwarding devices, making decisions centrally. The quality of service perceived by the user, or Quality of Experience (QoE), is considered to be a matter of great importance in software defined networks. This paper presents the SDN QoE Monitoring Framework (SQMF), an SDN application that monitors and preserves the QoE for VoIP and video applications, by periodically monitoring various network parameters and using QoE estimation models.

While video streaming has dominated the Internet traffic, video service providers (VSPs) compete on how to assure the best quality of experience (QoE) to their customers. HTTP Adaptive Streaming (HAS) has become the de facto way that helps VSPs work-around potential network bottlenecks that inevitably cause stallings. However, HAS-alone cannot guarantee a seamless viewing experience, since this highly relies on the mobile network operators' (MNOs) infrastructure and evolving network conditions. Software-defined networking (SDN) has brought new perspectives to this traditional paradigm where VSPs and MNOs are isolated, allowing the latter to open their network for more flexible, service-oriented programmability. This paper takes advantage of recent standardization trends in SDN and proposes a programmable QoE-SDN App, enabling network exposure feedback from MNOs to VSPs towards network-aware video segment selection and caching, in the context of HAS. The video selection problem is formulated using Knapsack optimization and relaxed to partial sub-problems that provide segment encodings that can mitigate stallings. Furthermore, a mobility prediction mechanism based on the Self-similar Least-Action Walk model is introduced, toward proactive segment caching. A number of use cases, enabled by the QoE-SDN App, are designed to evaluate the proposed scheme, revealing QoE benefits for VSPs and bandwidth savings for MNOs.

As wearables provide new health-related functionalities, they can be employed in hospitals to monitor patients and notify the medical personnel regarding their status. However, in order to be approved by the medical community, wearables need to have reliable communication and high lifetime. In such scenarios, it is important to know the probability of correct notification which is affected mainly by the deployment of the wireless wearables and their energy supply. Typically, rooms in hospitals host multiple people and, thus, a clustered communication model should be adopted for more trustworthy results. Moreover, by employing wireless charging, it is possible to provide an uninterrupted operation with high reliability. Therefore, in this paper, we study the aforementioned probability in a clustered network while the wearable devices are wirelessly charged. We provide an analytical model for the wearables' ability to inform quickly the medical personnel and discuss different trade-offs via extensive simulations.

Video streaming provided by Over-The-Top (OTT) service providers through a cellular network is a common usage scenario for many people today. While video streaming will work reasonably well in a stationary scenario, several issues arise for mobile users. For instance, travelling through short areas without cellular coverage, such as an automobile tunnel, will often result in quality degradation or video stalling. To combat this, this paper provides an analytical investigation of the video quality degradation problem as it is experienced by mobile users and suggests a context-aware HTTP Adaptive Streaming (HAS) strategy to prevent stalling and minimize the impact on Quality of Experience (QoE). This provides a solution that can completely prevent stalling when appropriate context information (such as positional information from satellite navigation) is present. The collected evaluation results encourage further research on how context-awareness can be exploited to further enhance video service provisioning by OTT service providers.

Multiple asynchronous devices, that exploit a pool of radio resources to communicate, form a key 5G communication scenario. Considering multicarrier transmission for this scenario, the expected multiuser synchronization errors at a receiving node, may be compensated by inserting guard subcarriers between transmissions from different devices. We analyze the radio resource overhead due to the use of guard subcarriers in correlation with the adopted multicarrier waveform and subcarrier allocation scheme. We show that Orthogonal Frequency Division Multiplexing (OFDM) can hardly serve the aforementioned scenario, while, in general case the use of guard subcarriers introduces another strain on the resource allocation procedure, questioning the performance of resource allocators that in conventional scenarios are highly efficient.

Towards the new era of communications, direct communications are intensively studied by industry and academia. One of the major challenges in this communication paradigm is the device discovery problem, referring to the mutual detection of neighboring devices prior the establishment of the direct communication. Recognizing the scarcity of the radio resources and the need for frequent discovery transmissions, we propose a validation approach as a complement to the device discovery process. Building on the idea that the neighboring relationship of some devices may last for long time, an enhanced radio resource allocation is applied for those devices, improving the overall performance of the discovery process.

Device-to-device (D2D) discovery is the inextricable prelude for the direct exchange of local traffic between cellular users in proximity. The D2D discovery process can be based on either autonomous actions taken by D2D-enabled devices, also known as network-assisted D2D discovery or core network functionalities to estimate proximity, also known as network-assisted D2D discovery. A key advantage of network-assisted D2D discovery is its potential to reduce the energy, signaling, and interference required for D2D discovery, by exploiting knowledge of the network layout. We analyze the performance of network-assisted D2D discovery in random spatial networks and derive useful guidelines for its design. We derive approximate expressions for the distance distribution between two D2D peers conditioned on the core network's knowledge of the cellular network layout, assuming that the base stations are distributed according to the Poisson point process. The expressions are used to assess the interplay between the D2D discovery probability and key system parameters, such as network intensity and transmit power, as well as to identify conditions to maximize the D2D discovery probability. Numerical results validate the accuracy of our findings and provide insights on the performance tradeoffs of network-assisted D2D discovery.

Device-to-Device (D2D) communications enable direct exchange of localized traffic between cellular users in proximity. Nonetheless, the employment of D2D communications heavily relies on the capability of the cellular devices to infer on their proximity. In this paper, we analyze the performance of network- assisted D2D discovery in random cellular networks and derive optimal deployment strategies for transforming the today's cellular network, which is optimized for coverage and capacity, into a D2D- centric network where the discovery and communications between cellular devices will be orchestrated by the core network. In this direction, we develop an analytical framework that exploits existing knowledge of the cellular network topology and effectively estimates the probability that two tagged devices are in proximity, a.k.a. D2D discovery probability. Also, we identify conditions under which the D2D discovery probability is maximized and assess the key performance trade-offs inherent to network-assisted D2D discovery.

Currently, cellular networks are evolving towards providing high quality mobile services in a ubiquitous manner. In this direction, increased robustness is required to face fluctuations at the service quality that follow traffic demanding events, such as an earthquake or a blackout. Dealing with this challenge, we propose a cross-layer scheme, which handles the traffic changes by adjusting dynamically the encoding rate at the application layer. The rate adjustments target at controlling the impact on the provided Quality of Experience (QoE), i.e., the key metric for assessing the perceptual quality of a provided service. The performance analysis conducted revealed a smooth QoE adaptation to traffic changes with quite low signaling cost for the exchange of the rate adaptation commands.

Today's heterogeneous wireless network (HWN) is a collection of ubiquitous wireless networking elements (WNEs) that support diverse functional capabilities and networking purposes. In such a heterogeneous networking environment, proximity estimation will play a key role for the seamless support of emerging applications that span from the direct exchange of localized traffic between homogeneous WNEs (peer-to-peer communications) to positioning for autonomous systems using location information from the ubiquitous HWN infrastructure. Since most of the existing wireless networking technologies enable the direct (or indirect) estimation of the distances and angles between their WNEs, the integration of such spatial information is a natural solution for robustly handling the unprecedented demand for proximity estimation between the myriads of WNEs. In this paper, we develop an analytical framework that integrates existing knowledge of the HWN layout to enable proximity estimation between WNE supporting different radio access technologies (RATs). In this direction, we derive closed-form expressions for the distance distribution between two tagged WNEs given partial (or full) knowledge of the HWN topology. The derived expressions enable us to analyze how different levels of location-awareness affect the performance of proximity estimation between WNEs that are not necessarily capable of communicating directly. Optimal strategies for the deployment of WNEs, as means of maximizing the probability of successful proximity estimation between two WNEs of interest, are presented, and useful guidelines for the design of location-aware proximity estimation in the nowadays HWN are drawn.

We consider the problem of determining the structural differences between different types of social networks and using these differences for applications concerning prediction of their structures. Much research on this problem has been conducted in the context of social media such as Facebook and Twitter, within which one would like to characterize and classify different types of individuals such as leaders, followers, and influencers. However, we consider the problem in the context of information gathered from law-enforcement agencies, financial institutions, and similar organizations, within which one would like to characterize and classify different types of persons of interest. The members of these networks tend to form special communities and thus new techniques are required. We propose a new generative model called Cliqster, for unweighted networks, and we describe an interpretable, and efficient algorithm for representing networks within this model. Our representation preserves the important underlying characteristics of the network and is both concise and discriminative. We demonstrate the discriminative power of our method by comparing to a traditional SVD method as well as a state-of-the-art Graphlet algorithm. Our results are general in that they can be applied to “person of interest” networks as well as traditional social media networks.

In this paper, we present a novel framework for virtualizing the Long Term Evolution (LTE) base stations to improve the user performance and lower the downlink interference. Our proposal, referred to as “OpeNB”, is an attempt to utilize the benefits of Software Defined Networking (SDN) and OpenFlow, introducing network virtualization in LTE networks with an adaptable, highly extensible, and less invasive manner. The proposed solution consists of a novel network architecture and a mechanism that allows the virtualization of LTE base stations depending on the network state. Simulation results show that the proposed framework improves the average interference, throughput and packet loss experienced by the end users.

To address the challenging issues of energy-efficiency and seamless connectivity in heterogeneous networks, 3GPP and IEEE have recently incorporated several architectural and functional enhancements to the baseline operation of their standards for cellular and wireless local area network access, respectively. Based on the 3GPP Access Network Discovery and Selection Function (ANDSF) and the advanced measurement capabilities provided by the IEEE 802.11-2012 and the 3GPP Long Term Evolution - Advanced (LTE-A) Standards, we propose an ANDSF-assisted energy-efficient vertical handover decision algorithm for the heterogeneous IEEE 802.11-2012 / LTE-A network. The proposed algorithm enables a multi-mode mobile terminal to select and associate with the network point of attachment that minimizes its average overall power consumption and guarantees a minimum supported quality of service for its ongoing connections. System-level simulation is used to evaluate the performance of the proposed algorithm and compare it to that of other competing solutions.

Device-to-Device (D2D) communications are currently attracting high interest from industry and academia, targeting at new commercial and public safety proximity services (ProSe). A major challenge under consideration is the device discovery problem, i.e., the problem of meeting the communication peers in time, frequency and space. In line with the current standardization efforts from the 3rd Generation Partnership Project (3GPP), we propose a centrally controlled device discovery scheme which consists of an application layer procedure and a set of access level enhancements. The target of the application layer procedure is to enable the ProSe discovery services, while the access level enhancements ensure the spectrum resources required for discovery transmissions. Evaluation results illustrate the impact of consuming cellular resources for device discovery on cellular network performance, while reveal the potential performance gains for the cellular network due to the introduction of the ProSe communications.

Femtocells will play a key role for the wide adoption of the LTE-Advanced system, as they bring the access network closer to the end user in a cost-effective manner. This disruptive communication paradigm, however, dictates the use of advanced interference and mobility management algorithms to cope with the dense yet unplanned network layout. In this paper, we present an interference-aware handover decision algorithm for the LTE-Advanced femtocell network, which utilizes standard signal measurements to select the candidate cell that a) attains the minimum required channel gain for sustaining service continuity and b) minimizes the mean UE transmit power for a prescribed mean SINR target. The proposed algorithm attains backwards compatibility with the LTE-Advanced system, as it is deployed by using the private mechanism for non-standard use. Based on the evaluation methodology of the Small Cell forum, we validate the performance of the proposed algorithm and compare it against that of other state-of-the-art algorithms.

Device-to-Device (D2D) communications provide the means to users of cellular networks for spatially reusing licensed spectrum by establishing direct connections. Considering the benefits for operators and consumers, a plethora of resource and interference management approaches in the literature deal with parallel cellular and D2D transmissions. However, this feature is not yet supported by modern cellular systems, such as the Long Term Evolution (LTE). The current paper targets at filling this gap by enabling D2D transmissions in LTE networks. Standardized LTE capabilities are utilized to provide a comprehensive framework on which existing or future resource and interference management schemes for D2D communications may be applied. The proposed framework is assessed under a moderate scenario where the cellular resource management policy is not affected. Results show that multiple D2D connections can be established in parallel to cellular uplink transmissions, while a satisfactory percentage of the cell region is available for spatial spectrum reuse.

Femtocells are attracting a fast increasing interest nowadays, as a promising solution to improve indoor coverage, enhance system capacity, and lower transmit power. Technical challenges still remain, however, mainly including interference, security and mobility management, intercepting wide deployment and adoption from mobile operators and end users. This paper describes a novel handover decision policy for the two-tier LTE network, towards reducing power transmissions at the mobile terminal side. The proposed policy is LTE backward-compatible, as it can be employed by suitably adapting the handover hysteresis margin with respect to a prescribed SINR target and standard LTE measurements. Simulation results reveal that compared to the widely-adopted strongest cell policy, the proposed policy can greatly reduce the power consumption at the LTE mobile terminals, and lower the interference network-wide.

This paper improves the video prediction mechanism used for prediction of the uplink real-time traffic of an integrated satellite and WiMAX network. After a bibliographic search on mechanisms for video prediction in WiMAX and satellite networks, the NLMS (Normalized Least Mean Square) algorithm is chosen to be used as part of the existing mechanism, studying three possible alternatives that can be used. The first one proposes the implementation of the NLMS algorithm in the WiMAX BS (Base Station), the second one proposes the implementation of the NLMS algorithm in the satellite terminal, while the third one proposes the implementation of the NLMS algorithm in both the WiMAX BS and the satellite terminal. Simulation results show improved performance of all alternatives, while the best results are given by the second one which also has the lowest complexity in computations and memory. This alternative is finally presented and evaluated.

ABSTRACT Modern wireless orthogonal frequency division multiple access (OFDMA) systems incorporate dynamic resource allocation (DRA), adaptive modulation and coding (AMC), and power control (PC) to exploit multiuser diversity and achieve higher system throughput. In the literature, only a few proposed algorithms deal with the contiguous DRA problem according to which a contiguous collection of resources can be allocated to each user. This paper formulates this high complexity problem, provides a suitable decision metric and a simple yet efficient solution. The proposed algorithm allocates in each step a contiguous collection of resources to the pending user that leads to the highest estimated correctly received number of bits. Simulation results show that, in this way, considerably improved performance can be achieved in terms of overall system throughput, spectral efficiency, and served traffic. Copyright © 2010 John Wiley & Sons, Ltd.

Resent measurements and reports show that in most cases licensed spectrum is used sporadically resulting in large unutilized spectrum portions. Opportunistic spectrum access (OSA) is a promising solution providing methods to identify and exploit these portions. Most existing OSA proposals provide ways for unlicensed users to access the licensed spectrum. This paper describes a novel approach where licensed users of an infrastructure-based system exploit features of their system to detect spatial spectrum opportunities. Focusing on an interference-free solution, an alternative opportunistic operation mode is provided, allowing licensed users to increase utilization of their own spectrum.

Current mobile devices are equipped with multi-standard interfaces to fully utilize both the existing and the imminent Public Land Mobile Network infrastructure. This flexibility comes with significant energy consumption overheads at the mobile terminal side and thus, the adopted interface / network selection scheme, a.k.a. Vertical Handover mechanism, should be based on both Quality of Service oriented and energy-efficiency criteria. This paper summarizes the current state of the art on energy-centric vertical handover algorithms, discusses weak aspects of existing approaches and presents a novel context-aware vertical handover framework towards energy-efficiency. Rather than a pure energy-centric vertical handover scheme, this framework is a context-awareness enabler for energy-centric vertical handover decision making.

In this paper, we start with a bibliographic search for slot allocation methods in static MF-TDMA satellite systems, followed by a multi-frequency extension of previous work that describes a prediction-based scheduling mechanism for joint WiMAX/satellite environments. The proposed mechanism consists of three parts. The first part requests satellite bandwidth based on an estimation of the needs of the WiMAX network at the time the bandwidth is granted, the second part allocates bandwidth on the satellite channel, while the third distributes it to the WiMAX users. Simulation results show improved performance of slot allocation in MF-TDMA, especially in terms of throughput and delay.

The IEEE 802.16e standard provides a high degree of flexibility for setting up and operating mobile WiMAX networks in metropolitan environments. While the standard supports differentiated Quality of Service (QoS), crucial functions such as traffic scheduling and slot allocation are left as open issues to the research community. This paper focuses on these two features, that consist an NP-Hard problem, and provides an integrated solution. The key component of the proposal is the “Colored OFDMA Frame Registry Tree Scheduler” (CO-FRTS) that achieves QoS-aware resource allocation by using an advanced tree structure to prepare the creation of time frames, and reduce processing requirements. An extended simulation model reveals the improved performance of the proposed solution, compared to other competent proposals.

A cross-layer mechanism for the performance improvement of real-time applications over IEEE 802.16e networks is proposed. The mechanism coordinates i) adaptation capabilities at different layers of the protocol stack, and ii) the handover initiation procedure. It uses information from the physical (PHY) and medium access control (MAC) layers to determine the appropriate burst profile, transmission power level and media encoding rate for a connection, or initialize a handover. The main contribution of this mechanism is the integration of the handover initiation into an existing cross-layer logic mechanism to improve the overall system performance. Extensive simulation results show that the proposed design achieves significantly improved performance in terms of packet loss rate, power consumption, and throughput, as well as an increased system capacity.

A cross-layer mechanism to improve the performance of real-time applications over IEEE 802.16e metropolitan area networks is presented. The proposed mechanism uses channel quality and service quality information from the physical and medium access control layers, respectively, to determine the most suitable burst profile, transmission power level and media encoding rate for a connection, or even initialize a handover execution. The main contribution of this mechanism is the integration of the handover initiation into the cross layer logic, aiming to improve the overall system performance. Extensive simulation results show that the proposed mechanism offers significant performance improvement in terms of packet loss rate, power consumption, throughput, and system capacity.

Abstract In this paper, an efficient cross‐layer design that performs joint adaptation of the physical (PHY) and application layers of a mobile WiMAX network is proposed. The design takes into account channel state and performance information from the PHY and medium access control (MAC) layers, respectively. It uses a decision algorithm to evaluate this information, specify unfavorable conditions regarding low channel quality and increased congestion, and take measures by coordinating modulation order, transmission power, and media encoding rate, toward improved overall quality of service (QoS) offered to the user. Extensive simulation results show that the proposed design achieves considerably reduced packet loss and power consumption, combined with increased throughput as compared to a typical mobile WiMAX system. Copyright © 2008 John Wiley & Sons, Ltd.

In this paper, we describe and evaluate an advanced traffic scheduler for IEEE 802.16 point-to-multipoint networks, referred to as "Colored Frame Registry Tree Scheduler" (C- FRTS). The main characteristics of this scheduler are i) the use of a tree structure to prepare the creation of time frame maps and reduce processing requirements at the beginning of each frame, and ii) a colored discrimination of packets scheduled for transmission to guarantee the bandwidth reserved for different connections. Simulation results show that C-FRTS can guarantee major QoS parameters, such as the maximum latency and the minimum and maximum reserved bandwidth, as well as provide differentiated treatment to the various service types.

The IEEE 802.16 standard provides a high degree of flexibility for setting up and operating wireless broadband networks in metropolitan environments. The standard supports numerous capabilities, including mesh topologies and multimedia communications. In this paper, we study these two features by investigating how efficiently an IEEE 802.16 mesh network can treat distributed multimedia traffic by providing differentiated quality of service (QoS). A key component of the system is the ldquoenhanced frame registry tree schedulerrdquo (E-FRTS) that provides QoS-aware resource allocation using a tree structure to prepare the creation of time frames and reduce processing requirements at the beginning of each frame. Simulation results show that distributed multimedia traffic can be efficiently supported in mesh 802.16 networks, provided efficient scheduling and a reasonable number of hops.

Abstract In this paper, we address the architecture and the procedures that can enable voice call handover from UMTS to WLAN and we also study how efficiently the WLAN can support the voice calls transferred from UMTS. Our study is based on a practical simulation model that lets us quantify the maximum number of voice calls that can be handed over from UMTS to WLAN, subject to maintaining the same level of UMTS QoS and respecting some WLAN policies. In addition, several other voice call performance metrics are derived. Our results indicate that an IEEE 802.11e access point can support a limited number of voice calls handed over from UMTS, which depends primarily on the applied WLAN bandwidth sharing policy (i.e., how the bandwidth is shared between WLAN voice and data users) and the QoS requirements. The performance of the WLAN scheduling algorithm is also of paramount importance and in our study we consider the so‐called ARROW scheduler. Although the simulation results are derived for a specific bandwidth sharing policy, they can readily be scaled and provide practical upper bounds for the number of UMTS voice calls that can be seamlessly admitted to a WLAN access point. Copyright © 2007 John Wiley & Sons, Ltd.

The proliferation of WLANs and the ubiquitous coverage of cellular networks have resulted in several integration proposals towards 4G networks. Among them, the tight- coupled WLAN/UMTS architectures promise seamless service continuity to users and enhanced network performance. Most of these solutions assume that only one interface is active at a time, while much fewer consider the concurrent use of both WLAN and UMTS interfaces as this is expected to consume more energy. This paper presents a detailed description of power consumption for the two different tight-coupled WLAN/UMTS approaches based on the states of the wireless devices. A simple analytical model is provided for estimating the power consumption in each approach, while a simulation model measures the power needs for more complicated cases. Moreover, the enhancement due to a power-saving mechanism in WLAN is also assumed in the system and useful deductions are provided about the average power consumption per mobile terminal.

Radio resources management in integrated cellular and wireless networks is a very complex and important issue. Although a number of proposals exist in the literature that present considerable improvement in several aspects, they also present some disadvantages that affect their implementation and deployment. In an attempt to tackle this, we propose a simple distributed algorithm that enables terminals to build prioritised lists of target access network independently for each of their connections. The algorithm also provides specific details on how the core network components can treat each connection based on a number of parameters, which are of paramount importance for the operators. The final choice is a trade-off between the user preferences, the terminal capabilities, the network load and the location and speed of the terminal. The algorithm is designed to provide an easy method for defining user preferences. Finally, we provide an initial evaluation of the signalling load required inside the core network to support the proposed decision making mechanism and make suggestions on the best functional architecture of the radio resource management entities.

In this paper we propose and study a cross-layer mechanism that can improve real-time QoS provisioning over IEEE 802.16 metropolitan area networks. This mechanism utilizes information provided by the Physical and MAC layers and using a heuristic algorithm it derives new operational parameters for the Physical and Application layers, which can improve the performance of real-time applications. The main idea is to coordinate the adaptive modulation capability of the Physical layer and the multi-rate data-encoding capability of modern real-time applications in order to avoid inefficiencies caused by their independent operation. Simulations show that the proposed mechanism can assist 802.16 systems better adapt to frequent channel and traffic changes, leading to considerably reduced packet loss rates, especially under heavy traffic conditions.

The proliferation of wireless access technologies, mostly wireless LANs, along with the ubiquitous coverage of cellular networks, has spurred many researchers to consider schemes for integrated network provision. In overlaying network environments, flexible resource management and service continuity during handover play a crucial role in the quality-of-service seen by the user. This paper describes an integrated UMTS/WLAN architecture that manages to establish every connection in a mobile terminal through the most appropriate access network, based on both network policies and user preferences. Moreover, connections are handed over independently between UMTS and WLAN, aiming at seamless service continuity. A detailed simulation model is used to measure the performance of the proposed architecture against existing schemes

In this paper we present a novel traffic scheduling algorithm for IEEE 802.11e, referred to as ARROW (adaptive resource reservation over WLANs), which aims at providing improved performance for the support of multimedia traffic. The novel characteristic of this algorithm, compared to previous proposals, is that it performs channel allocations based on the actual traffic buffered in the various mobile stations, i.e., on the exact transmission requirements. This feature renders ARROW ideal for variable bit rate traffic. However, an enhancement is also presented that improves ARROW performance under constant bit rate traffic. The ARROW algorithm and its enhancement are discussed and evaluated against two other schedulers found in the open technical literature, namely the simple scheduler and SETT-EDD. Results from a detailed simulation model verify that ARROW provides much better channel utilization and considerably improved performance, in terms of mean delay and packet loss

Abstract ‘Always Best Connected’ (ABC) is considered one of the main requirements for next generation networks. The ABC concept allows a person to have access to applications using the devices and network technologies that best suits his or her needs or profile at any time. Clearly, this requires the combination of a set of existing and new technologies, at all levels of the protocol stack, into one integrated system. In this paper, a considerable set of the technologies, that are expected to play a key role towards the ABC vision, are presented. Starting from a reference architecture, the paper describes the required enhancements at certain levels of a traditional protocol stack, as well as technologies for mobility and end‐to‐end Quality of Service (QoS) support. The paper concludes with a case study that reveals the advantages of the ABC concept. This article replaces a previously published version (Wireless Communications and Mobile Computing; 5(2): 175‐191. [DOI: 10.1002/wcm.207]). Retraction notice DOI: 10.1002/wcm.426 . Copyright © 2006 John Wiley & Sons, Ltd.

In this paper we present a novel traffic scheduling algorithm for IEEE 802.11e, referred to as ARROW (adaptive resource reservation over WLANs), able to handle multimedia traffic. The novel characteristic of ARROW is that it performs channel allocations based on the actual traffic (not estimated traffic) buffered in the various mobile stations. Additionally, a variation of ARROW is studied for improving the performance for constant bit rate traffic. The ARROW algorithm and its enhancement are evaluated against two other schedulers found in the literature, namely the simple scheduler and SETT-EDD. Results from a detailed simulation model show that much better channel utilization and considerably improved performance can be provided.

IEEE 802.16 is considered today as the most promising technology, to provide extension of wireless broadband communications into metropolitan environments. One of the main design challenges in 802.16 is the introduction of an efficient traffic scheduler that handles resource allocation in the wireless interface. This paper proposes such a scheduler, referred to as the "frame registry tree scheduler", that aims at providing differentiated treatment to data connections, based on their QoS characteristics. The scheduler uses a tree structure in order to prepare time frame creation and reduce processing needs at the beginning of each time frame. Simulation results show that the proposed scheduler can attain considerable improvement in terms of throughput and packet losses

A flow rejection algorithm for the dynamic resource reservation protocol (dRSVP) protocol is proposed. dRSVP is an enhanced version of RSVP, aiming at providing dynamic quality-of-service (QoS) support in a variable bandwidth environment (e.g., wireless) through guarantees of ranges of bandwidth instead of specific values. Flow rejection occurs when the channel quality decreases to a level that even the minimum bandwidth requirements per flow cannot be fulfilled. The proposed algorithm aims at improving the flow dropping probability of dRSVP, without affecting the bandwidth utilization. Its operation is based on setting priority classes and rejecting the minimum required number of flows per class, in order to guarantee QoS to the remaining. Both mathematical analysis and simulation results show that the overall flow dropping probability can be significantly reduced.

A flow rejection algorithm for the dynamic RSVP (dRSVP) is proposed. dRSVP is an enhanced version of RSVP, aiming at providing dynamic quality of service (QoS) support in a variable bandwidth environment through guarantees of ranges of bandwidth instead of specific values. Flow rejection occurs when the channel quality decreases to a level that even the minimum bandwidth requirements per flow cannot be fulfilled. The proposed algorithm aims at significantly improving the flow dropping probability, without affecting the bandwidth utilization. Its operation is based on setting priority classes and rejecting the minimum required number of flows per class, in order to guarantee QoS to the remaining. Both mathematical analysis and simulation results show that the overall flow rejection probability can be significantly reduced.

The paper focuses on the integration of Internet and wireless LANs (WLANs) and proposes a novel technique that supports seamless and efficient integration. This technique is based on a generic adaptation layer, referred to as wireless adaptation layer (WAL), which is introduced between the IP layer and the WLAN link layer. WAL is designed to: (i) cope dynamically with wireless channel impairments; (ii) provide QoS interworking between the IP infrastructure and the WLAN; (iii) be independent of the WLAN technology. These characteristics account for the advantages of WAL, namely, improved performance, wide applicability and provisioning of differentiated services.

The scarce available bandwidth and the unpredictable, variable bit rate traffic in modern packet-switched wireless LANs, require an efficient channel allocation scheme. In this paper we make an overview of traditional call-by-call dynamic channel assignment (DCA) methods and propose a novel DCA method that aims at assigning channels in a more dynamic way, based on the quality-of-service (QoS) required by different connections. Although the method can be applied in different wireless environments, here it is used in a wireless ATM LAN, in conjunction with a TDMA/TDD medium access control protocol. Simulation results at the end of the paper show that this kind of methods can improve significantly the performance of the system.

A centralized approach for dynamic channel assignment (DCA) in wireless systems is presented. The proposed method applies to structured wireless LANs, where base stations act as hubs to offer wireless access to mobile terminals. We focus on wireless ATM LANs, although the method applies also to other packet-based systems, offering quality-of-service (QoS) guarantees. A central scheduler for DCA (CSDCA) is introduced for the dynamic assignment of resources to the requesting base stations. This scheduler takes into account mutual interference constraints of the base stations, current resource usage, and delay constraints of active connections. Simulation results have shown the improved performance attained by the proposed method.

The medium access control (MAC) protocol and the underlying traffic scheduling mechanism for the radio interface are critical components of a wireless ATM network, aiming to provide ATM-like quality of service (QoS) guarantees over the air. A traffic scheduling algorithm for a wireless ATM customer premises network is proposed. The algorithm operates in the mobile terminals, and complements a centralized scheduling mechanism operating in the base stations, for improved performance. The proposed algorithm is delay oriented to meet the requirements of the various traffic classes defined by the ATM architecture. The system performance improvement attained by the proposed algorithm is evaluated via simulations.

In this paper, a multiservice, local-area, wireless access ATM system is explored from a signaling protocol viewpoint. The signaling architecture considered here follows the signaling structure of broadband ISDN (B-ISDN) user-network interface (UNI), thus offering the possibility for integration of the wireless ATM access system into fixed B-ISDN. It is shown that the use of the employed signaling structure substantially simplifies the call/bearer and handover control. The evaluation of the signaling protocol architecture yields results, which fall within acceptable ATM signaling performance measures. A comparison with alternate access signaling configurations is also carried out to quantify the relative gains.