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- Hybrid wireless network with SDN and legacy devices in ad-hoc environmentsPublication . Sousa, Daniela; Sargento, Susana; Luís, MiguelOn temporary events, like concerts or emergency scenarios, where a communication infrastructure may not be sufficient or even present, networks can be built in a spontaneous way with the available network elements and radio access technologies, to support proper communication and data access. However, these ad-hoc networks, without a centralized view, can be inefficient when compared to a detached centralized control approach like in Software Defined Networks (SDNs). Moreover, SDNs can bring several advantages to these environments, such as adaptability and performance increase, despite not supporting wireless interfaces. However, in these scenarios, not all nodes are able to support SDN. This paper proposes a Spontaneous Heterogeneous Wireless Software Defined Network with a hybrid approach that is able to opportunistically use all available elements that may compose the network, regardless of whether they are legacy or SDN nodes. The proposed approach is tested in several scenarios with a different ratio of legacy to SDN nodes. We conclude that the network is able to work with hybrid nodes, and that when more Hybrid SDN (H-SDN) devices are used to forward packets, the network performance increases or is maintained when compared to a pure ad-hoc solution.
- 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.
- 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.
- LoRa connectivity analysis for urban coverage in real mobile environmentsPublication . Oliveira, Rui; Luís, Miguel; Sargento, SusanaFor the last few years, LoRa technology has been affirming itself as one of the most prominent and widely adopted low power wide area technologies. Very compatible with Internet of Things (IoT) applications and urban environments, this technology is capable of long range communications although with small bandwidths, and consequently, low data rates. Nevertheless, the quality of LoRa communications, like many other wireless technologies, are highly dependent on the transmission's context. In this work, we evaluate the performance of LoRa communications in a mobile sensing scenario, and study its capability to give wireless coverage to a small-size city. Experimental results show that velocity has a consistent and increasing impact on the packet delivery ratio, and that the coverage capability is much more dependent on the terrain distribution and Line-of-Sight (LoS), than on the distance between the mobile node and the gateway.
- Using aerial and vehicular NFV infrastructures to agilely create vertical servicesPublication . Nogales, Borja; Silva, Miguel; Vidal, Ivan; Luís, Miguel; VALERA, FRANCISCO; Sargento, Susana; Azcorra, Arturo5G communications have become an enabler for the creation of new and more complex networking scenarios, bringing together different vertical ecosystems. Such behavior has been fostered by the network function virtualization (NFV) concept, where the orchestration and virtualization capabilities allow the possibility of dynamically supplying network resources according to its needs. Nevertheless, the integration and performance of heterogeneous network environments, each one supported by a different provider, and with specific characteristics and requirements, in a single NFV framework is not straightforward. In this work we propose an NFV-based framework capable of supporting the flexible, cost-effective deployment of vertical services, through the integration of two distinguished mobile environments and their networks: small sized unmanned aerial vehicles (SUAVs), supporting a flying ad hoc network (FANET) and vehicles, promoting a vehicular ad hoc network (VANET). In this context, a use case involving the public safety vertical will be used as an illustrative example to showcase the potential of this framework. This work also includes the technical implementation details of the framework proposed, allowing to analyse and discuss the delays on the network services deployment process. The results show that the deployment times can be significantly reduced through a distributed VNF configuration function based on the publish-subscribe model.
- 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.
- 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.
- 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.
- When backscatter communication meets vehicular networks: boosting crosswalk awarenessPublication . Pereira, Felisberto; Sampaio, Hugo; Chaves, Ricardo; Correia, Ricardo; Luís, Miguel; Sargento, Susana; Jordão, Marina; Almeida, Luís; Senna, Carlos; Oliveira, Arnaldo S. R.; Carvalho, Nuno BorgesThe research of safety applications in vehicular networks has been a popular research topic in an effort to reduce the number of road victims. Advances on vehicular communications are facilitating information sharing through real time communications, critical for the development of driving assistance systems. However, the communication by itself is not enough to reach the most desired target as we need to know which safety-related information should be disseminated. In this work, we bring passive sensors and backscatter communication to the vehicular network world. The idea is to increase the driver (or vehicle) awareness regarding the presence of pedestrians in a crosswalk. Passive sensors and backscatter communication technologies are used for the pedestrians’ detection phase, while the vehicular network is used during the dissemination of the detection information to surrounding vehicles. The proposed solution was validated through end-to-end experimentation, with real hardware and in a real crosswalk with real pedestrians and vehicles, demonstrating its applicability.
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