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

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

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

The relentless expansion of deep learning applications in recent years has prompted a pivotal shift toward on-device execution, driven by the urgent need for real-time processing, heightened privacy concerns, and reduced latency across diverse domains. This article addresses the challenges inherent in optimising the execution of deep neural networks (DNNs) on mobile devices, with a focus on device heterogeneity, multi-DNN execution, and dynamic runtime adaptation. We introduce CARIn , a novel framework designed for the optimised deployment of both single- and multi-DNN applications under user-defined service-level objectives. Leveraging an expressive multi-objective optimisation framework and a runtime-aware sorting and search algorithm ( RASS ) as the MOO solver, CARIn facilitates efficient adaptation to dynamic conditions while addressing resource contention issues associated with multi-DNN execution. Notably, RASS generates a set of configurations, anticipating subsequent runtime adaptation, ensuring rapid, low-overhead adjustments in response to environmental fluctuations. Extensive evaluation across diverse tasks, including text classification, scene recognition, and face analysis, showcases the versatility of CARIn across various model architectures, such as Convolutional Neural Networks and Transformers, and realistic use cases. We observe a substantial enhancement in the fair treatment of the problem’s objectives, reaching 1.92× when compared to single-model designs and up to 10.69× in contrast to the state-of-the-art OODIn framework. Additionally, we achieve a significant gain of up to 4.06× over hardware-unaware designs in multi-DNN applications. Finally, our framework sustains its performance while effectively eliminating the time overhead associated with identifying the optimal design in response to environmental challenges.

Cascade systems comprise a two-model sequence, a lightweight model processing all samples and a heavier model conditionally refining harder samples to improve accuracy. By placing the light model on the device side and the heavy model on a server, model cascades constitute a widely used distributed inference approach. With the rapid expansion of intelligent indoor environments, the new setting of Multi-Device Cascade is emerging where multiple and diverse devices are simultaneously using a shared heavy model on the same server, typically located close to the consumer environment. This work presents Multi-TASC, a multi-tenancy-aware scheduler that adaptively controls the forwarding decision functions of the devices in order to maximize the system throughput, while sustaining high accuracy and low latency. By explicitly considering device heterogeneity, our scheduler improves the latency service-level objective (SLO) satisfaction rate over state-of-the-art cascade methods in highly heterogeneous setups, while serving over 40 devices, showcasing its scalability.

Deep learning (DL) is characterised by its dynamic nature, with new deep neural network (DNN) architectures and approaches emerging every few years, driving the field's advancement. At the same time, the ever-increasing use of mobile devices (MDs) has resulted in a surge of DNN-based mobile applications. Although traditional architectures, like CNNs and RNNs, have been successfully integrated into MDs, this is not the case for Transformers, a relatively new model family that has achieved new levels of accuracy across AI tasks, but poses significant computational challenges. In this work, we aim to make steps towards bridging this gap by examining the current state of Transformers' on-device execution. To this end, we construct a benchmark of representative models and thoroughly evaluate their performance across MDs with different computational capabilities. Our experimental results show that Transformers are not accelerator-friendly and indicate the need for software and hardware optimisations to achieve efficient deployment.

The unprecedented performance of deep neural networks (DNNs) has led to large strides in various Artificial Intelligence (AI) inference tasks, such as object and speech recognition. Nevertheless, deploying such AI models across commodity devices faces significant challenges: large computational cost, multiple performance objectives, hardware heterogeneity and a common need for high accuracy, together pose critical problems to the deployment of DNNs across the various embedded and mobile devices in the wild. As such, we have yet to witness the mainstream usage of state-of-the-art deep learning algorithms across consumer devices. In this paper, we provide preliminary answers to this potentially game-changing question by presenting an array of design techniques for efficient AI systems. We start by examining the major roadblocks when targeting both programmable processors and custom accelerators. Then, we present diverse methods for achieving real-time performance following a cross-stack approach. These span model-, system- and hardware-level techniques, and their combination. Our findings provide illustrative examples of AI systems that do not overburden mobile hardware, while also indicating how they can improve inference accuracy. Moreover, we showcase how custom ASIC- and FPGA-based accelerators can be an enabling factor for next-generation AI applications, such as multi-DNN systems. Collectively, these results highlight the critical need for further exploration as to how the various cross-stack solutions can be best combined in order to bring the latest advances in deep learning close to users, in a robust and efficient manner.

Radical progress in the field of deep learning (DL) has led to unprecedented accuracy in diverse inference tasks. As such, deploying DL models across mobile platforms is vital to enable the development and broad availability of the next-generation intelligent apps. Nevertheless, the wide and optimised deployment of DL models is currently hindered by the vast system heterogeneity of mobile devices, the varying computational cost of different DL models and the variability of performance needs across DL applications. This paper proposes OODIn, a framework for the optimised deployment of DL apps across heterogeneous mobile devices. OODIn comprises a novel DL-specific software architecture together with an analytical framework for modelling DL applications that: (1) counteract the variability in device resources and DL models by means of a highly parametrised multi-layer design; and (2) perform a principled optimisation of both model- and system-level parameters through a multi-objective formulation, designed for DL inference apps, in order to adapt the deployment to the user-specified performance requirements and device capabilities. Quantitative evaluation shows that the proposed framework consistently outperforms status-quo designs across heterogeneous devices and delivers up to 4.3× and 3.5× performance gain over highly optimised platform- and model-aware designs respectively, while effectively adapting execution to dynamic changes in resource availability.

Recent advances in IoT and pervasive computing have led to the introduction of a plethora of devices, featuring enhanced intelligence in sensing, understanding context and reacting to situations. In the case of smart home environment, the result is the introduction of smart, connected domotic devices, featuring enhanced intelligence. In combination with enhanced capabilities for sensing, controlling and automatic, the power of these devices can be further exploited by the use of a semantic connection layer that can facilitate a goal-oriented collaboration between devices and a meaningful interaction with humans. This paper proposes an integrated platform, enabling dynamic injection of automation rules based on semantic web technologies, in a collective intelligence environment. The role of the human - end user in this environment is supported through a user friendly IDE enabling the easy discovery, access and operation, through the introduction of automation rules.

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

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

As the number of available web services increases, the development of web applications that integrate existing web services becomes more and more popular. This class of web applications can be seen as the composition of web services around a user interface flow. In this paper, the application of model-driven techniques for the development of such user-centric web applications is presented. An approach for the modeling of the application using UML class and state transition diagrams and the transformation to appropriate platform specific code is presented. The service design is based on the introduced UML profiles, whereas on code level frameworks implementing the Model-View- Controller architectural pattern are targeted. © 2008 ACM.

Context-awareness constitutes an important aspect in mobile environments, especially when user-centric services are considered. However, user and service related data as part of context information are sensitive and their disclosure should not be performed unconditionally. In this paper a Privacy-aware Context Profile (PCP) in UML notation that takes into account privacy and quality, as well as other functional and non-functional properties is presented. The profile can be exploited in the application design phase leading to the model-driven development of context-aware applications for different context domains.

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

Mobile and pervasive computing is gaining significant importance in the latest years. Context-awareness constitutes an essential aspect - almost a requirement - of mobile services in these environments. In this paper, we propose an architecture that supports the development and provision of context-aware services. The described approach provides means for the context adaptation of software components exposed as Web services independently of their specific implementation allowing for added flexibility concerning the adaptation itself or whether it is performed at all. As the service logic is clearly separated from the context adaptation, the same principle can be applied to composite Web services. Specifically, we show that different services and context sources can be combined to provide a Web application separating completely the application logic from the context adaptation. Context plugins loaded on runtime are responsible for invoking the right context sources to retrieve the necessary context information and complete the service adaptation to context.

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

As technology develops, people are using an ever broader and heterogeneous range of ICT devices and network-based services. The result is an enormous burden of complexity on the shoulders of users, service providers and network operators. The goal of the Simplicity project, supported by the European Union, is to reduce this complexity by: (i) providing automatic customization of user access to services and the network; (ii) automatically adapting services to terminal characteristics and user preferences; (iii) orchestrating network capabilities. The Simplicity approach is based on a personalization device, the so-called Simplicity device, which, together with a brokerage framework, offers transparent service configuration and runtime adaptation, according to user preferences and computing/networking context conditions. This paper presents the Simplicity project, briefly discusses its architecture and introduces the Simplicity demonstrator: a proof of concept implementation used to verify our approach, through diverse usage scenarios. In addition, we introduce the main aspects of a follow-up project of Simplicity, named SMS.

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

Location-based services (LBS) constitute one of the most attractive services' categories for cellular networks. 3GPP defines the "Le" interface for external LBS provision and access to the core network of mobile operators. Multiple proprietary and commercial protocols and APIs can be used to implement this interface. The paper examines the realization of "Le" interface according to the proposed 3GPP standards, namely the mobile location protocol (MLP) over HTTP and the mobility API of OSA/Parlay using middleware technologies. The performance of both approaches is evaluated. Furthermore, with respect to the mobility API of OSA/Parlay, three implementations, based on respective middleware technologies (CORBA, RMI and Web Services over SOAP), are examined, for evaluating the performance of each OSA/Parlay gateway. The results of the experiments provide useful performance indicators concerning the efficiency of the internal architecture of each implementation as well as the anticipated speed of the user-service interaction.

While handover management has been traditionally using radio technology specific mechanisms, the need for integration of this diverse network environment has obviated the 'push' of the handover functionality to the access-agnostic IP layer. In this context, we study and analyze the implications of the link-layer agnostic operation of the IP handover control on the handoff performance, having as a reference the fast mobile IPv6 protocol. We show that the behavior of the protocol is highly dependent on the timely availability of link layer information - this determines whether a reactive or a proactive operation is executed. Last, we provide some quantitative results for performance metrics such as the disruption time and the packet loss perceived, by a single mobile host under varying conditions of link-layer trigger time availability, buffering capabilities and beacon intervals.

The adoption of packet-switched technologies in mobile communication systems has enabled the provision of IP-based services to mobile users. Yet, these systems, such as the UMTS network, are unable to meet the stringent delay requirements imposed by the enhanced multimedia services due to the anchor point that introduce into the user's data path. Moreover, such applications will rely on IP-based control protocols for session and mobility management, resulting in duplication of functionality in the network at both the bearer and the application level. For the above reasons, the SAILOR network architecture is presented in this paper, proposing an evolution to the standard UMTS network, where GSNs are integrated into a single entity. Furthermore, the SIP protocol is adopted, for performing mobility and session management procedures currently undertaken by the UMTS non-access stratum protocols. Both modifications to the UMTS network and protocol architecture result in the smooth evolution of the UMTS core network towards IP as well as accomplish a significant performance gain.

The support of multicasting as a network layer service poses stringent requirements to next generation mobile networks. But for the fact that IP multicasting has been considered in wireless networks, not until recently has there been a first attempt for the multimedia broadcast/multicast service (MBMS) support in UMTS. The investigation of MBMS architectural and functional design in respect to session and mobility management is the major focus of this paper. We approach mobility management support for idle- and connectedmode users with activated MBMS sessions as an extension to the existing mechanisms applicable to point-to-point communication. Moreover, we move one step further to the integration of the UMTS with the IP world, by replacing the UMTS core network with a fully IP-enabled network and propose mobility management mechanisms, in this integrated environment, for users receiving MBMS data.

Resource provisioning mechanisms play a crucial role in determining the level of quality of service offered by a network. Based on the current research activities, this paper presents a scalable and dynamic set of resource allocation mechanisms applied in the context of the AQUILA intra-domain architecture for providing QoS guarantees. We are focusing on the details of the interworking among the proposed resource allocation mechanisms, which take place at a different time-scale and are applied at different levels of the network architecture, highlighting the scalability features they convey. Finally, the presented trial results underline the performance and scalability offered by those mechanisms, which succeed in providing the expected QoS guarantees keeping simultaneously complexity and simplicity at a low level.

This paper evaluates the performance of a distributed intelligent network (D-IN), enhanced with a middleware-based service and resource management functionality. We test its performance by building and emulating its basic functionality, based on distributed object technology (DOT), in a real environment. Resource management functionality mainly aims at avoiding congestion and balancing its load and is implemented by the incorporation of the ICALB algorithm (V. M. Stathopoulos and I. S. Venieris, November 2002). This incorporation is succeeded through the use and implementation of a generic and distributed middleware-based service. It is a CORBA-based service that is used for successfully managing resource management algorithms, such as ICALB, facilitate their operation, and solving classes of problems related to communications over the distributed network, sharing of resources spread over the network, scheduling, synchronization, and management of various tasks. By this means we argue that the method that we use can be employed for operating in various distributed networks. We also evaluate the network's performance by measuring the contents of a queue of an IN node with critical meaning and by showing the improvements that appeared to the D-IN from the operation of both the ICALB algorithm and the proposed service.

IP technology will play a key role in beyond 3G systems, which face the great challenge of integration so as to provide seamless services to users anywhere and anytime. Apart from its natural role as a unifier, IP also comprises the main drive for network evolution towards all-IP network infrastructures. In this regard, we exploit IP as an enabler for the evolution of the UMTS packet-switched core network, eliminating its duality at user and transport level. We focus on mobility management in the core network, which is handled by pure IP mechanisms, and on the support of fast handoff across UMTS access networks by means of a hybrid Fast and Hierarchical Mobile IPv6 (F/HMIPv6) proposal. Emphasis is also put on identifying the proper points of interaction between the F/HMIPv6 operation and the UMTS-specific serving radio network subsystem (SRNS) relocation procedure in order to provide a seamless handoff service to the user while not compromising the network's performance and scalability.

Next generation Internet architectures will consider the differentiated services paradigm for the provision of quality of service to the individual customer needs and applications. This paper addresses the definition and deployment of specific network services in a DiffServ environment. The proposed network services and the underlying traffic engineering methods are analyzed and simulated. Simulation outcomes prove that the fundamental principles of the network services are fulfilled.

The differentiated service architecture (DiffServ) is currently a popular research topic as a low-cost method to provide quality of service to the different applications in the Internet. This paper addresses the definition and deployment of specific network services in a DiffServ environment. Each network service is appropriate for a specific type of traffic and is realized through its own network mechanisms, which are the traffic classes. The focus of the paper is the services appropriate for real time delay-sensitive applications such as voice and video. Different traffic control algorithms are studied for the implementation of the proposed services. Simulation results show that the proposed traffic control mechanisms provide hard performance guarantees to different flows.

The Internet is widely known for lacking any kind of mechanism for the provisioning of quality of service guarantees. An overlay resource control management layer on top of a differentiated services core network is introduced for managing and adjusting the resources among network elements. This layer realises an algorithm which provides a dynamic approach for resource distribution. Our experimental results show that this algorithm can allocate network resources according to the traffic load and provide an adaptive and efficient way for re-distributing the resources among network elements.

The evolution of intelligent networks (IN) passes through the distributed networking environments, made possible by the introduction of advance software technologies like CORBA and software agents. The starting point of this paper is the broadband intelligent network which adopts a centralised approach in processing IN service requests. The performance bottlenecks of the IN architecture, centred around the core service processing unit, (i.e. service control point (SCP)) are studied and compared to alternative architectures enabling distribution of intelligence to others than the SCP entities of the IN. We consider a distributed intelligent network architecture based on CORBA and mobile agents technology. We evaluate the performance of this architecture by simulation using a set of detailed models developed to represent the internal operations of the system. Results given provide insight on critical design issues like the selection of physical entities for the migration of software, the service software objects to be transferred as well as the selection of software platforms. Overall the paper provides useful guidelines for the design and implementation of advanced IN architectures.

The logic ruling the user and network authentication as well as the data ciphering in the GSM architecture has been inherited by the General Packet Radio Services (GPRS) and the Universal Mobile Telecommunication System (UMTS) as well. So, in all these systems, three nodes are involved in the corresponding processes, namely, the mobile station (MS), the visitors location register (VLR), and the home location register (HLR). Moreover, the methods of the conventional cryptography have been adopted by all the three systems. A description of the subscriber authentication is given, as well as of the data ciphering, as they are recommended by the specifications regarding the aforementioned systems. Based on this analysis, we pinpoint the vulnerable points of the VLR-HLR and MS-VLR links, exposed to third party attacks, and we propose for their coverage asymmetric cryptography procedures, consisting of the introduction of public-private key pairs for the transactions between the VLR-HLR, as well as the MS-VLR.

We evaluate a variation of random early detection (RED) for IP gateways (G/Ws), which drops/marks packets by controlling the average queue delay than the average queue size. The new algorithm is applied when the bandwidth of the outgoing connection varies over time and the service rate is explicitly advertised to the boundary G/W, such as in the available bit rate (ABR) transfer capability. The mechanism embodies the features of RED for congestion avoidance, and additionally guarantees the required queue delay commitments. The mechanism is proposed as complementary to RED, for delay sensitive traffic classes. Performance results using the OPNET simulation package proven that the mechanism is adaptive to changes in the backbone available bandwidth and offers the target QoS in terms of delay.

In next-generation IP networks, there will be a mixture of traffic classes with different QoS requirements. Differentiated Services (DiffServ) has evolved from the IETF's earlier Integrated Services (IntServ) standard as a solution to the service quality challenges. In this paper, a novel buffer management scheme called CBQ priority buffer management (CPBM) is presented for IP routers, using the class based queueing (CBQ) scheduler, in a combined IntServ and DiffServ architecture. The objectives of the CPBM scheme are to cope with the various QoS requirements of the IP layer service classes, to utilize the buffer space as efficiently as possible and to successfully coordinate with the CBQ scheduling mechanism in order to improve packet loss performance. The proposed CPBM scheme has been compared with conventional buffer management schemes as complete partitioning (CP), push-out (PO) and push-out with threshold (POT), using OPNET release 5.1.D as a simulation platform.

The design of a buffer management algorithm, with controllable quality-of-service (QoS) commitments in terms of packet loss, is addressed for IP routers in a differentiated services architecture. The objectives of the proposed policy are to utilize the buffer space efficiently to coordinate with the class-based queuing (CBQ) scheduling algorithm adopted by the IP routers, and mainly to be able to adjust the quality spacing between the different QoS traffic classes. Using OPNET Modeler 6.0.L as a simulation platform, the proposed scheme is compared along with conventional buffer management policies, such as complete partitioning (CP), push-out (PO) and push-out with threshold (POT). Numerical results demonstrate the controllable relative differentiation between classes achieved by the proposed scheme.

In this short paper an approach to the ATM hierarchical (PNNI) routing issue is presented based on a simple algorithm that chooses a route for a connection request out of a predefined list of possible routes between a specific source-destination pair in a probabilistic way. A route fitness (cost) function is used to assign selection probabilities to every candidate path and arriving connection requests are routed independently according to these path probabilities. This cost function has been chosen in a way to achieve a successful trade-off between the use of minimum-hop routes and the application of the load-balancing concept. Moreover we show that the performance of the proposed algorithm and other probabilistic routing algorithms can be enhanced with the application of scaling techniques that are used in genetic algorithms (GAs) maximizing the network revenue. Simulation results over a wide range of uniform, time-varying and skewed loading conditions show the effectiveness of the proposed routing algorithm.

The wireless network evolution, delineated during the last years, has urged the necessity to extend the up-to-now static business environment to a mobile and wireless one. However, the current and forthcoming wireless technologies are characterized by different attributes regarding the coverage area, offered bandwidth and delay. The transparent conjunction of various wireless technologies into a single mobile terminal can further boost the wireless explosion. This paper presents the architectural approach and the results concerning the continuous connectivity and seamless switching between two complementary wireless networks, one 802.11-compliant in the short area and a CSM in the wide area. The described experiments were performed on an open, IP-based wireless architecture that can be easily extended to accommodate future wireless networks.

Novel services increase the call processing complexity which often impacts on the maximum number of admitted calls. We consider a broadband network in which service requests are processed by intelligent network (IN) functions. We develop a congestion control algorithm that protects the network from overload and evaluate its performance using well defined models that are able to represent complex higher level protocols and IN functional entities. It is shown that the proposed mechanism maximises the number of admitted calls with acceptable call set up delay.

In this paper an efficient heuristic routing algorithm is proposed that increases the network throughput irrespective of the network traffic load. Its effectiveness is based on an efficient cost metric, which achieves a successful trade-off between the use of the minimum-hop routes and the load balancing. Moreover, it employs the known trunk reservation concept according to probability that increases linearly as the traffic load increases. This results in an effective compromise of the performance of the algorithm between light and heavy loads. Finally its simplicity and its suitability for a real-time application render it as an efficient routing algorithm for ATM networks.

A wireless intelligent ATM access system is explored from a signaling protocol viewpoint. The proposed architecture is consistent with the B-ISDN user-network interface (UNI) signaling structure as a wireless local area network to access the ATM core network infrastructure, and can be adapted to cater also for a wireless broadband access network for future mobile telecommunication systems. Emphasis is placed on taking advantage of well-developed protocol standards, where appropriate, to allow the easy introduction of the proposed architecture in the real world. The evaluation of the signaling performance of the system captures the effect of the proposed structure on the performance of call and mobility control and yields results, which fall within acceptable signaling performance measures.

Time division multiple access (TDMA) multiplexing of ATM cells from thousands of residential customers toward the common feeder of a passive optical network (SuperPON) tree obviates the need for an equal number of optical line terminations (OLTs). All upstream transmissions converge by means of the passive splitters/combiners to just one OLT unit which serves all by time sharing. The ability to reach such a high splitting ratio became possible by the development of bursty mode optical amplifiers (OAs). In addition, OAs make possible a 100-km-long feeder which can bypass the local exchange into the first core switch, bringing further savings to both initial and running costs. These techniques allow SuperPONs to lower the access cost per customer, holding for the promise of ushering into domestic local loops the photonics revolution which has already transformed the transmission plant. These savings, however, can only be realized under the assumption that the system can accept high loading before exceeding the limits of quality of service (QoS) requirements and without distorting the egress traffic in a way that jeopardizes the statistical estimates on which ATM connection acceptance was based. Solutions to the problem of traffic arbitration, respecting the idiosyncrasies of each traffic class and suitable for fast implementation, are offered.

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.

In the current ATM LAN emulation (LANE) standard the issues of flow control and bandwidth allocation in the access units have not been adequately addressed. This paper investigates ways to enhance the functionality of typical legacy LAN-ATM access units (AUs) with the addition of low-level flow control mechanisms. The scheme proposed is based on the available bit rate (ABR) control mechanism currently standardized for ATM. Backpressure flow control is not terminated in the AU but is further extended to reach the nonATM legacy LAN stations. This is achieved by using a subset of the logical link control (LLC) protocol functionality executed between the AU and the legacy LAN stations. Apart from the QoS guarantees, the proposed method is transparent to the upper transport layer protocols and as such it does not require fundamental modifications to existing AUs and LAN stations.

Advanced architectures integrating intelligent network (IN) signaling are proposed for the support of multimedia services. We present the main elements of an IN-based signaling configuration and introduce a set of models for representing their protocols and internal processes. An IN-based methodology is established to derive the workload for each network element, protocol and functional entity. We study the performance of an IN-based signaling network by applying this methodology to a typical broadband video on demand (B-VoD) service. The results of our study give useful guidelines for the design and implementation of IN signaling architectures.

The dynamic operation of ATM access networks (ANs) calls for the incorporation of advanced signalling functionality also in the access part of the ATM core network. Instead of implementing the entire control plane in the AN, we take advantage of the separation between call, bearer and channel control and we proceed with a simple, standard compliant bearer channel control architecture for the ATM AN. We evaluate our proposal in terms of additional call set-up delay by means of analysis. Results demonstrate the benefits of our approach as opposed to the complexity and performance degradation brought about with the use of Q.2931 in the AN.

The asynchronous transfer mode (ATM)-based broadband integrated services digital network (B-ISDN) dominates the research interest in telecommunications. Traffic and network modeling are the techniques used for performance evaluation and assessment of B-ISDN design alternatives and planning. The specific nature of the ATM technique requires new approaches for traffic modeling. Selecting appropriate traffic source models is an important issue, since it is closely related to the successful design and efficient performance of the networks to be built in the future. The source (multilevel, multiservice structured Markovian) model presented provides a simple way for characterizing the behavior of a telecommunication user recognizing the multilevel discipline of a telecommunication session. The traffic model is general enough to fit a variety of different services by appropriately varying the values of the parameters defining it, but also it is simple enough because it is described by a small number of parameters and the defining parameters make a good intuitive sense by being closely related to actual physical quantities.

The paper models and evaluates key design issues for the Adaptation Layer in ATM networks. The role and efficient design of the adaptation layer is crucial for future B-ISDN based on ATM. We concentrate on packet-mode adaptation services analyzing and simulating relevant protocols employed for narrowband ISDN signaling and packet data. Processing and transmission resources are modeled. In particular we investigate the performance of software based solution resident in microprocessors and interfaces to the ATM world via a generic interface component. This set-up which is currently under development is found adequate to handle narrowband ISDN signaling and data traffic. It offers a cost effective and readily available solution for the transition phase towards fully customized broadband components.

Connectionless (CL) services as already developed in LANs, have to interwork with emerging asynchronous transfer mode (ATM) connection-oriented (CO) networks. MANs are a significant evolutionary step and CO MANs, in particular, constitute a technically appealing method to integrate both environments and provide shared medium access for all services. The functions required for enhancing distributed-queue dual-bus (DQDB) MANs with CO services in a way compatible with ATM are described. Within the integrating framework of B-ISDN, the practically useful scenarios for interworking LANs, CO and CL MANs, and ATM are investigated and classified in order to exploit the advantages of an efficient protocol relay utilizing the resources of the lowest possible layer. This is aimed at assisting interworking unit (IWU) designers and implementors to decide on key options in this versatile and evolving environment. The CO DQDB case emerges as the most advantageous development in terms of interworking simplicity and robustness.>

The authors examine the internetworking of the distributed queue dual bus (DQDB) metropolitan area network (MAN) with asynchronous transfer mode (ATM) of broadband integrated services digital network (B-ISDN). Several scenarios are discussed. It is suggested that the best solution is through the use of a connection-oriented (CO) DQDB service. Some of the provisions of the CO DQDB service necessary for an efficient and simple interworking are provided.>

The cost of a dedicated fiber access to the B-ISDN is too high for small business and residential customers, necessitating some form of resource sharing. Combining ATM over a passive optical network (APON) with a suitable medium access control (MAC) protocol can provide significant cost savings and a reasonable bandwidth. In this way, this customer section can also enjoy introduction of broadband services at a relatively early stage. The emphasis of the MAC protocol presented is placed on service transparency with an aim to incur minimal changes to the local exchange (LEX) when an APON is attached. Sharing is effected by a reservation-based time division multiple access method.>

The problem of resource allocation for future integrated broadband communication networks (IBCNs) is addressed. It mainly involves resource allocation at the connection level. The resource allocation problem is decomposed into the following interdependent tasks: given that a network can accommodate the bandwidth demand of a call request, determine a route for the corresponding asynchronous transfer mode (ATM) virtual connection; and allocate bandwidth, i.e. links inside the trunks of the chosen route, to this connection according to predefined limits on bandwidth use by various service calls. Various link allocation schemes combined with routing algorithms are examined. Their performance in terms of service call blocking is evaluated using a software package developed, for that purpose. It is shown that the traditional complete sharing (CS) and complete partitioning (CP) policies are not adequate for IBCNs. Movable boundary (MB) policies are more flexible and present near-optimal performance when access of broadband service to narrowband service resources is allowed and suitable routing algorithms are dynamically applied.>

The asynchronous transfer mode (ATM) adaptation layer provides functions for mapping source traffic into ATM cells as required in recent standardization work for packet switched integrated broadband networks. Functions, services, and protocols suitable for signaling and other packet mode traffic are studied. The resulting protocol stacks are critically examined for two important and differing applications: signaling in broadband ISDN and the IEEE 802.3-5 series of standards for LAN interconnection. The emphasis is on the second case, which is currently considered as an imminent application area for broadband communication networks.>