Carlos Natalino

A quality of experience handover architecture for heterogeneous mobile wireless multimedia networks

The convergence of emerging real-time multimedia services, the increasing coverage of high-speed wireless networks, and the evergrowing popularity of mobile devices are leading to an era of user-centric multimedia wireless services. In this scenario, heterogeneous wireless communications will coexist and ensure that the end user is always best connected. However, the quality of experience supported for highquality applications in multi-operator environments remains a significant challenge and is crucial for the success of wireless multimedia systems. This article proposes a quality of experience handover architecture for heterogeneous mobile wireless multimedia networks. The architecture extends the media independent handover/ IEEE 802.21 proposal with QoE-aware seamless mobility, video quality estimator, dynamic class of service mapping, and a set of content adaptation schemes. The proposed architecture always provides the best connection and considers the QoE needs of mobile clients and available wireless resources in IEEE 802.11e and IEEE 802.16e service classes. Simulation experiments were performed to show the impact and benefits of the proposed solution from the users perception, by using both objective and subjective QoE metrics.

Dimensioning optical clouds with shared-path shared-computing (SPSC) protection

Service relocation represents a promising strategy to provide flexible and resource efficient resiliency from link failures in the optical cloud environment. However, when a failure affects a node hosting a datacenter (DC), service relocation from the affected DC is not possible. One alternative to protect against DC failures relies on using design strategies that duplicate the IT (i.e., storage and processing) resources in a backup DC at the expense of increasing resource overbuild (i.e., cost) of the network. This work proposes a dimensioning strategy based on the shared-path shared-computing (SPSC) concept able to protect against any single link, server, or DC failure scenario with minimal resource overbuild for the network and IT infrastructures. SPSC is based on the intuition that only storage units need complete replication in backup DC, while processing units can be instantiated only after the occurrence of a failure, leaving the design strategy some leeway to minimize their number. As result, the proposed SPSC design shows a considerable reduction in the amount of backup resources when compared to the dedicated protection strategies.

Resource Management in Fog-Enhanced Radio Access Network to Support Real-Time Vehicular Services

With advances in the information and communication technology (ICT), connected vehicles are one of the key enablers to unleash intelligent transportation systems (ITS). On the other hand, the envisioned massive number of connected vehicles raises the need for powerful communication and computation capabilities. As an emerging technique, fog computing is expected to be integrated with existing communication infrastructures, giving rise to a concept of fog-enhanced radio access networks (FeRANs). Such architecture brings computation capabilities closer to vehicular users, thereby reducing communication latency to access services, while making users capable of sharing local environment information for advanced vehicular services. In the FeRANs service migration, where the service is migrated from a source fog node to a target fog node following the vehicles moving trace, it is necessary for users to access service as close as possible in order to maintain the service continuity and satisfy stringent latency requirements of real-time services. Fog servers, however, need to have sufficient computational resources available to support such migration. Indeed, a fog node typically has limited resources and hence can easily become overloaded when a large number of user requests arrive, e.g., during peak traffic, resulting in degraded performance. This paper addresses resource management in FeRANs with a focus on management strategies at each individual fog node to improve quality of service (QoS), particularly for real-time vehicular services. To this end, the paper proposes two resource management schemes, namely fog resource reservation and fog resource reallocation. In both schemes, real-time vehicular services are prioritized over other services so that their respective vehicular users can access the services with only one hop. Simulation results show that the proposed schemes can effectively improve one-hop access probability for real-time vehicular services implying low delay performance, even when the fog resource is under heavy load.

Lifetime-aware provisioning in green optical backbone networks

We present a framework able to limit the device lifetime degradation in optical backbone networks using sleep-mode-based green strategies. Results show that our approach manages the lifetime while not compromising significantly the energy saving performance.

Optimal Lifetime-Aware Operation of Green Optical Backbone Networks

This paper targets the lifetime-aware management of a set of optical line amplifiers (OLAs) in an optical network exploiting sleep mode (SM) in order to save energy. We first present a simple model to predict the OLA lifetime. We then provide different mixed-integer linear programming (MILP) formulations, which jointly consider energy saving and lifetime. The proposed MILP formulations are then solved on different realistic scenarios, by taking into account the spatial and temporal variations of traffic demands. Results show that our lifetime-aware approach outperforms classical energy saving ILP formulations, which instead tend to notably decrease the OLA lifetime. More important, the proposed approaches can achieve a good lifetime performance without consuming significantly more energy than purely energy-aware strategies.

A relocation-based heuristic for restoring optical cloud services

Optical clouds allow for an integrated management of optical transport and cloud resources (e.g., storage and computing resources running on datacenters). In this paradigm the concept of service relocation (i.e., the ability to re-allocate to a different datacenter node an already provisioned cloud service) offers a new way to restore the network upon failure. This paper presents a heuristic (called H_RELOCATION) based on the service relocation concept to be used for the dynamic restoration of optical cloud services. Upon the occurrence of a network failure, H_RELOCATION solves the routing and resource (i.e., transport plus cloud) allocation problem for each disrupted cloud service allowing, if necessary, to relocate some cloud services to different datacenter nodes. The proposed strategy is benchmarked against two optimal restoration strategies based on Integer Linear Programming (ILP) formulations, the first one without and the second one with the ability to use the service relocation idea. Simulation results show that H_RELOCATION offers performance (i.e., blocking probability, restorability levels and number of required relocations) very close to the optimum, offering on the other hand, a significant reduction in the processing time required for each successfully restored cloud service.

Green-fuzzy - An intelligent user allocation model for macro-femto co-channel networks

The concept of femtocell aims to combine fixed-line broadband access with mobile telephony using low cost and power third and fourth generation base stations in the subscribers homes. Femtocells are self-configurable, however, can limit the quality of service (QoS) and reduce the efficiency of the network, since it uses old assignment standards, such as the power level of the signal. Thus, this paper presents a proposal for optimized allocation of users in a macro-femto co-channel network, in order to maximize the QoS of the applications and energy efficiency, toward the concept of green networks. A fuzzy inference system is implemented to define which network the mobile phone should connect; the model is flexible, allowing different analyzes, and adaptable to the specific characteristics of the telephone companies. Results showed that the model proposed can improve energy efficiency up to 25%, when compared to traditional QoS approaches.

Infrastructure upgrade framework for Content Delivery Networks robust to targeted attacks

Abstract Content Delivery Networks (CDNs) are crucial for enabling delivery of services that require high capacity and low latency, primarily through geographically-diverse content replication. Optical networks are the only available future-proof technology that meets the reach and capacity requirements of CDNs. However, the underlying physical network infrastructure is vulnerable to various security threats, and the increasing importance of CDNs in supporting vital services intensifies the concerns related to their robustness. Malicious attackers can target critical network elements, thus severely degrading network connectivity and causing large-scale service disruptions. One way in which network operators and cloud computing providers can increase the robustness against malicious attacks is by changing the topological properties of the network through infrastructure upgrades. This work proposes a framework for CDN infrastructure upgrade that performs sparse link and replica addition with the objective of maximizing the content accessibility under targeted link cut attacks. The framework is based on a newly defined content accessibility metric denoted as μ-ACA which allows the network operator to gauge the CDN robustness over a range of attacks with varying intensity. Two heuristics, namely Content-Accessibility-Aware Link Addition Heuristic (CAA-LAH), and Content-Accessibility-Aware Replica Addition Heuristic (CAA-RAH) are developed to perform strategic link and replica placement, respectively, and hamper attackers from disconnecting users from the content even in severe attack scenarios. Extensive experiments on real-world reference network topologies show that the proposed framework effectively increases the CDN robustness by adding a few links or replicas to the network.

Energy- and fatigue-aware RWA in optical backbone networks

Abstract Connection provisioning in Wavelength Division Multiplexing (WDM) networks needs to account for a number of crucial parameters. On the one hand, operators need to ensure the connection availability requirements defined in Service Level Agreements (SLAs). This is addressed by selecting an appropriate amount of backup resources and recovery strategies for the connections over which services are provisioned. Services requiring less strict availability requirements can be routed over unprotected lightpaths. Services with more strict availability requirements are provisioned over protected lightpaths in order to cope with possible failures in the network. Another important aspect to consider during the provisioning process is energy efficiency. Green strategies leverage on setting network devices in Sleep Mode (SM) or Active Mode (AM) depending on whether or not they are needed to accommodate traffic. However, frequent power state changes introduce thermal fatigue which in turn has a negative effect on the device lifetime. Finally, in multi-period traffic scenarios, it is also important to minimize the number of reconfigurations of lightpaths already established in the network in order to avoid possible traffic disruptions at higher layers. The work presented in this paper tackles the connection provisioning paradigm in an optical backbone network with a multi-period traffic scenario. More specifically the paper looks into the interplay among (i) energy efficiency, (ii) thermal fatigue, and (iii) lightpath reconfiguration aspects. To this end, the Energy and Fatigue Aware Heuristic with Unnecessary Reconfiguration Avoidance (EFAH-URA) is introduced, showing that it is possible to balance the three aspects mentioned above in an efficient way. When compared to the pure energy-aware strategies, EFAH-URA significantly improves the average connection availability for both unprotected and protected connections. On the other hand, it is done at the expense of reduced energy saving.

Assessing the effects of physical layer attacks on content accessibility and latency in optical CDNs

Content Delivery Networks (CDNs) are a major enabler of large-scale content distribution for Internet applications. Many of these applications require high bandwidth and low latency for a satisfactory user experience, e.g., cloud gaming, augmented reality, tactile Internet and vehicular communications [1]. Replication is one of the most prominent solutions to meet the requirements of latency-sensitive applications [1, 2]. However, infrastructure disruptions can greatly degrade the performance of such applications, or even cease their proper execution. The extent of degradation can be exacerbated by malicious attackers that target the critical elements of the CDN physical infrastructure to disconnect or severely degrade services.