Percorrer por autor "Sargento, Susana"
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- Bringing network coding into SDN: architectural study for meshed heterogeneous communicationsPublication . Cohen, Alejandro; Esfahanizadeh, Homa; Sousa, Bruno; Vilela, João P.; Luís, Miguel; Raposo, Duarte; Michel, François; Sargento, Susana; Medard, MurielModern communications have moved away from point-to-point models to increasingly heterogeneous network models. In this article, we propose a novel controller-based architecture to deploy adaptive causal network coding in heterogeneous and highly meshed communication networks. Specifically, we consider using the software-defined network as the main controller. We first present an architecture for highly meshed heterogeneous multi-source multi-destination networks that represent the practical communication networks encountered in the fifth generation of wireless networks and beyond. Next, we present a promising solution to deploy network coding over the new architecture. We also present a new controller-based setting with which network coding modules communicate to attain the required information. Finally, we briefly discuss how the proposed architecture and network coding solution provide a good opportunity for future technologies.
- Complementing vehicular connectivity coverage through cellular networksPublication . Rocha, Filipe; Luís, Miguel; Zúquete, André; Sargento, SusanaVehicular Ad hoc Networks (VANETs) support the development of safety and infotainment applications, allowing vehicles to communicate between each other and with the infrastructure, assuring their connection and of its occupants to the Internet These VANETs may rely on different technologies for their deployment, such as IEEE 802.11p/WAVE, C-V2X or Wi-Fi; however, complete coverage and full connectivity may not be assured. This work integrates, in a seamless approach, an additional communication interface via cellular networks into an existing VANET with mobility and multihoming support in order to increase its connection availability. The proposed solution makes use of commercial cellular networks without the need of any contribution by network providers, and maintaining transparency to the end-user. The validation and evaluation of the proposed solution was performed with a real network in real- world scenarios. The results showed that the proposed approach is able to maintain and increase the VANET connectivity.
- Consumer mobility awareness in named data networksPublication . Caldeira Hernandez, Diego; Luís, Miguel; Sargento, SusanaMobile data traffic has increased significantly due to the evolution of wireless communication technologies. The Information Centric Network paradigm is considered as an alternative to bypass the restrictions imposed by the traditional IP networks, especially those related with the mobility of its users. Despite the potential advantages of this paradigm regarding mobile wireless environments, several research challenges remain unaddressed, more specifically the ones related with the communication damage caused by handovers. This work presents a Named Data Network (NDN) based solution that supports Consumer mobility. The proposed scheme addresses a mobility manager entity that monitors and anticipates trajectories, while compelling the infrastructure to adjust to the new paths. This process results in an efficient way to manage the Consumers' mobility, and therefore, in a better quality of service to its users. The implementation and evaluation of the proposed solution uses the ndnSIM, through functional and non-functional scenarios, and with real traces of urban vehicular mobility and connectivity. The results show that the proposed solution is superior to the native NDN workflow with respect to content delivery ratio and number of timeouts.
- Context-based caching in mobile information-centric networksPublication . Leira, Luís; Luís, Miguel; Sargento, SusanaWireless networking is expected to sustain the direct interaction between personal users’ devices, and to provide connectivity on large-scale resource-constrained devices. However, conventional networking protocols fail in large scale mobile wireless environments, due to node mobility, dynamic topologies, and intermittent connectivity. Information-Centric Networking (ICN) has been considered the most promising candidate to overcome the drawbacks of host-centric architectures where Named Data Networking (NDN) is one of the well-known and studied architectures within the ICN paradigm. The main objective of this work is to improve both content availability and network performance in mobile environments regarding the ICN paradigm. This is provided through a context-based approach for the caching admission policy providing in-network caching and content replication, facilitating the efficient and timely delivery of information. Content popularity, freshness, proximity, source mobility type and network density are some of the metrics considered in the caching decision. We conducted a comparative study between our proposal and the NDN caching strategy by using two different datasets with real mobility and connectivity traces, addressing intermittent communication. According to our results, we observed that using a multi-criteria context-based cache admission policy improves cache hits, cache evictions, and request satisfaction ratios in mobile environments, thus improving content delivery and network efficiency.
- Edge virtualization in multihomed vehicular networksPublication . Silva, Miguel; Luís, Miguel; Sargento, SusanaVehicular Networks (VANETs) are a critical component of a Smart City environment. They extended the connectivity plane with support for a wide range of applications, from safety to entertainment. Such services, when deployed outside the vehicular network, may imply an additional delay, which can be critical. In addition, these services become inaccessible whenever the vehicles lose contact with the infrastructure.This paper proposes a practical solution that aims to minimize the impact of the services' location and its inaccessibility in a VANET. The solution focuses on using Network Function Virtualization technologies to support the deployment of the services at the edge of a mobility-enabled multihomed VANET, thus allowing the services to be accessible in intermittent connectivity situations, as well as enabling lower delays for critical services. The results obtained show that the solution is capable of deploying services at the edge of the VANET with low delay and with a fast recovery when in handover and mobility scenarios.
- EmuCD: an emulator for content dissemination protocols in vehicular networksPublication . Chaves, Ricardo; Senna, Carlos; Luís, Miguel; Sargento, Susana; Moreira, André; Recharte, Diogo; Matos, RicardoThe development of protocols for mobile networks, especially for vehicular ad-hoc networks (VANETs), presents great challenges in terms of testing in real conditions. Using a production network for testing communication protocols may not be feasible, and the use of small networks does not meet the requirements for mobility and scale found in real networks. The alternative is to use simulators and emulators, but vehicular network simulators do not meet all the requirements for effective testing. Aspects closely linked to the behaviour of the network nodes (mobility, radio communication capabilities, etc.) are particularly important in mobile networks, where a delay tolerance capability is desired. This paper proposes a distributed emulator, EmuCD, where each network node is built in a container that consumes a data trace that defines the node's mobility and connectivity in a real network (but also allowing the use of data from simulated networks). The emulated nodes interact directly with the container's operating system, updating the network conditions at each step of the emulation. In this way, our emulator allows the development and testing of protocols, without any relation to the emulator, whose code is directly portable to any hardware without requiring changes or customizations. Using the facilities of our emulator, we tested InterPlanetary File System (IPFS), Sprinkler and BitTorrent content dissemination protocols with real mobility and connectivity data from a real vehicular network. The tests with a real VANET and with the emulator have shown that, under similar conditions, EmuCD performs closely to the real VANET, only lacking in the finer details that are extremely hard to emulate, such as varying loads in the hardware.
- Evaluation of content dissemination strategies in urban vehicular networksPublication . Pessoa, Gonçalo; Guardalben, Lucas; Luís, Miguel; Senna, Carlos; Sargento, SusanaThe main drivers for the continuous development of Vehicularad-hoc Networks (VANETs) are safety applications and services. However, in recent years, new interests have emerged regarding the introduction of new applications and services for non-urgent content (e.g., videos, ads, sensing and touristic information) dissemination. However, there is a lack of real studies considering content dissemination strategies to understand when and to whom the content should be disseminated using real vehicular traces gathered from real vehicular networks. This work presents a realistic study of strategies for dissemination of non-urgent contente with the main goal of improving contente delivery as well as minimizing network congestion and resource usage. First, we perform an exhaustive network characterization. Then, several content strategies are specified and evaluated in different scenarios (city center and parking lot). All the obtained results show that there are two content distribution strategies that clearly set themselves apart due to their superior performance: Local Rarest Bundle First and Local Rarest Generation First.
- Exploring software defined networks for seamless handovers in vehicular networksPublication . Silva, Miguel; Teixeira, Pedro; Anjos Gomes, Christian; Dias, Duarte; Luís, Miguel; Sargento, SusanaWith the growing interest in autonomous driving, constant connectivity for vehicles is becoming essential to enable the complete knowledge of the surrounding area, transmit and receive data that is crucial for the autonomous control. The vehicle mobility results in frequent service interruptions, and therefore, seamless handovers are required to mitigate this problem. Several IP-based solutions have been proposed in the literature, but they require tunneling approaches, which present excessive signaling and data overhead, service delay, and packet loss. One of these approaches, the NEMO-enabled Proxy Mobile IPv6 (N-PMIPv6) architecture, supports transparent handovers and simultaneous multi-homing, but at the cost of a high complexity and network overhead. This work explores the flexibility of Software Defined Networks (SDNs) in the management of a Vehicular Ad-hoc NETwork (VANET). In particular, the SDN concept is used to provide a seamless horizontal handover for the vehicle and its end-users. Two different SDN architectures are proposed, evaluating the impact of the depth of the softwarization environment. Real vehicular hardware and emulated mobility scenarios are used in the evaluation process where different application services are exploited. Results show that the lower complexity of the SDN solution allows for a better performance during a handover in a VANET, in terms of delays, packet losses and network overhead, making it seamless for the vehicles and its users.
- Exploring the use of control packets in LoRa medium access: a scalability analysisPublication . Fernandes, Rui; Oliveira, Rui; Luís, Miguel; Sargento, SusanaLoRa technology has been attesting itself as one of the most prominent and widely adopted low power wide area technologies. Highly compatible with Internet of Things (IoT) applications and urban environments, this technology enables large range communications although with small bandwidths and duty cycle restrictions. In this work, we propose a distinct way of dealing with the Medium Access Control (MAC) in LoRa, through the use of control packets to enhance the technology performance in urban city scenarios, where a large number of nodes is expected. The proposed protocol is asynchronous and takes into account the energy expenditure. We compare this scheme with the standard (LoRaWAN) by considering different network densities and packet sizes, and through different LoRa collision models. Performance results, such as network throughput and fairness index, show that, depending on the ratio between data and control packet lengths, it is possible to greatly improve the bit rate and overall network performance, even if increasing the duty-cycle restriction time due to the addition of overhead.
- Handling producer and consumer mobility in IoT publish-subscribe named data networksPublication . Caldeira Hernandez, Diego; Gameiro, Luís; Senna, Carlos; Luís, Miguel; Sargento, SusanaIn recent years, the Internet of Things (IoT) has become a standard facet of modern communications, and information-centric networks have been pointed as an alternative to bypass the restrictions imposed by the traditional Internet protocol networks regarding the mobility of its network elements. However, the improvements imposed by this new paradigm fall short in large scale mobile wireless distributed environments inherent to IoT, due to high node mobility, dynamic topologies and intermittent connectivity. To tackle these issues, we present a named data network (NDN)-based publish-subscribe mechanism with support for both Consumer and Producer mobility. This approach handles the Producer mobility by combining the Data packets with infrastructure specific information, fixing the broken paths between the Producer and the Consumer; and the Consumer mobility by monitoring and anticipating mobile node trajectories while compelling the infrastructure to adjust to new paths. Simulation results, assuming a smart city use case and using real traces of vehicular mobility, have shown that the proposed solution far surpasses the native NDN workflow and traditional publish-subscribe solutions. With respect to the Producer mobility, the proposed solution delivers 79% of Data packets against 14% with the Native implementation, when using 25 mobile Producers; regarding the Consumer mobility, results have shown that our solution achieves almost the same Consumer satisfaction ratio as previous implementations but reducing substantially the network overhead related with the transmission of Interest packets.
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