João N. Isento

Vehicular Delay-Tolerant Networks?A Novel Solution for Vehicular Communications

Vehicular Delay-Tolerant Networks (VDTNs) is a breakthrough based DTN-based solution to provide vehicular communications under challenging scenarios characterized by long delays and sporadic connections. VDTN uses a store-carry-and-forward paradigm, inspirited from Delay Tolerant Networks, which allows forward bundles to asynchronously reach the destination hop by hop over traveling vehicles equipped with short-range Wi-Fi devices. The proposed VDTN architecture assumes out-of-band signaling with control and data planes separation. VDTNs also assume datagrams aggregation under the network layer in large size packets, called bundles, following an IP over VDTN approach. This paper presents VDTN networks focusing on their layered architecture, bundle aggregation and de-aggregation mechanisms, network protocols, scheduling and dropping policies, fragmentation mechanisms, and the created tools for VDTNs performance evaluation, demonstration, and validation.

Impact of Scheduling and Dropping Policies on the Performance of Vehicular Delay-Tolerant Networks

Vehicular Delay-Tolerant Networks (VDTNs) are a disruptive network architecture based on delay-tolerant network paradigm, gathering contributions from opportunistic and cooperative networks, and optical burst switching paradigm. VDTNs assume out-of-band signaling and handle non-real time applications with a low cost network infrastructure. In VDTNs, vehicles are opportunistically exploited to carry data between terminal nodes, enabling network connectivity under unreliable conditions with unstable links and where a contemporaneous end-to-end path may not exist. To address this problem VDTN combines routing schemes that replicate bundles at contact opportunities, with long-term bundle storage. However, this combination increases the resources consumption (e.g., bandwidth, storage) and may affect the performance of the entire network. To improve network performance different scheduling and dropping policies can be used. This paper studies the impact of different scheduling and dropping policies on the performance of a VDTN laboratory testbed using Epidemic and Spray and Wait (binary variant) routing schemes. It was shown that network performance increases, in terms of delivery ratio and delivery delay, when these scheduling and dropping policies are based on the bundle lifetime criteria.

Testbed-based performance evaluation of routing protocols for vehicular delay-tolerant networks

As an application of the concept of delay-tolerant network (DTN) for vehicular communications, the vehicular delay-tolerant network (VDTN) architecture was proposed to cope with issues, such as highly dynamic network topology, short contact durations, disruption, intermittent connectivity, variable node density, and frequent network fragmentation. These challenging characteristics of vehicular networks affect the design and performance of routing protocols. This paper presents a testbed performance evaluation of DTN-based routing protocols applied to VDTNs. The objective is to evaluate and understand how popular routing strategies perform in sparse or partitioned opportunistic vehicular network scenarios. It was observed that Spray and Wait routing protocol outperforms all other protocols considered in the study.

Performance assessment of IP over vehicular delay-tolerant networks through the VDTN@Lab testbed

Vehicular delay-tolerant network (VDTN) is a network architecture based on the delay-tolerant network paradigm, which was designed to provide low-cost asynchronous vehicular communications in environments with disruptions, intermittency, variable delays, and network partition. This article proposes a laboratory testbed for VDTNs, called VDTN@Lab. It aims to support research studies related with the design, emulation, performance evaluation, and diagnose of new VDTN protocols, services, and applications. It intends to demonstrate the applicability of VDTNs over multiple application environments. VDTN@Lab features an emulation capability, allowing live experiments with prototyped hardware and software embedded into robotic cards, desktop, and netbooks computers. The proposed prototype is demonstrated and evaluated with Epidemic, and Spray, and Wait routing protocols, using different combinations of scheduling and dropping policies, in scenarios with different vehicular mobility models (bus movement and random movement across roads).

A real-world VDTN testbed for advanced vehicular services and applications

Many investments are being made in vehicular networking due to social and technological benefits that comes with the development of services and applications for the community, including safety issues. Vehicular Delay-Tolerant Networks (VDTNs) appear as innovative network architecture, able to outline communication challenges caused by issues like variable delays, disruption and intermittent connectivity. In this paper, a real-world VDTN testbed is introduced and it demonstrates and validates the technical concepts of the architecture in a real environment. VDTNs characteristics like IP over VDTN and out-of-band signaling concepts will be demonstrated in a safety service where warning messages are exchanged to notify emergency situations and distress signals. The main goals are to prove the applicability of VDTNs over different environments and evaluate the impacts of a real scenario on protocols stacks and services. The testbed considers three cars equipped with a Bluetooth and Wi-Fi devices, exchanging messages in a pre-defined route.

Man4VDTN - A network management solution for vehicular delay-tolerant networks

Vehicular delay-tolerant networks (VDTNs) follow the delay-tolerant networking (DTN) paradigm for vehicular communications in order to offer a network solution handling several issues, such as short contact durations, network disruption, variable node density, and packets fragmentation. All these issues represent a huge challenge for vehicular communications. The design and construction of a network management solution is also conditioned by these particular characteristics. The standard Simple Network Management Protocol (SNMP) is widely used on conventional networks but it is not directly deployable on VDTNs. Then, this paper proposes an SNMP-based solution for VDTNs supporting load-related information collection from VDTN nodes using SNMP. The design, demonstration, performance evaluation and validation of this network management approach through a laboratory-based VDTN testbed are presented. It was shown that SNMP is suitable for being used in challenging environments such as VDTNs.

Bundles fragmentation in Vehicular Delay-Tolerant Networks

Vehicular Delay-Tolerant Networks use the delay-tolerant architecture and protocols to overcome the disruptions in network connectivity. These concepts help in cases where the network is sparse or with large variations in density or there is no end-to-end connectivity, by providing a communications solution for non real-time applications. This paper presents data fragmentation techniques to optimize the efficiency of data delivery for the case of the short node contacts that characterize vehicle networks. The techniques were tested in a laboratory environment with portable digital assistants and Lego Mindstorm NXT robotic cars. If no fragmentation is used, only small messages are successfully transferred. Proactive fragmentation fragments messages to a predefined size in the source node. Reactive fragmentation adjusts the fragment sizes to the real duration of the contact when it is broken. Reactive fragmentation showed a good efficiency in adapting the fragmentation in real time to the contact duration. Proactive fragmentation can perform slightly better if the fragment sizes are carefully chosen as it requires less processing. As this choice is difficult, reactive fragmentation is more practical to use.

Performance assessment of fragmentation mechanisms for vehicular delay-tolerant networks

Vehicular Delay-Tolerant Networks (VDTNs) are a new approach for vehicular communications where vehicles cooperate with each other, acting as the communication infrastructure, to provide low-cost asynchronous opportunistic communications. These communication technologies assume variable delays and bandwidth constraints characterized by a non-transmission control protocol/internet protocol architecture but interacting with it at the edge of the network. VDTNs are based on the principle of asynchronous communications, bundle-oriented communication from the DTN architecture, employing a store-carry-and-forward routing paradigm. In this sense, VDTNs should use the tight network resources optimizing each opportunistic contact among nodes. Given the limited contact times among nodes, fragmentation appears as a possible solution to improve the overall network performance, increasing the bundle delivery probability. This article proposes the use of several fragmentation approaches (proactive, source, reactive, and toilet paper) for VDTNs. They are discussed and evaluated through a laboratory testbed. Reactive and toilet paper approaches present the best results. It was also shown that only the source fragmentation approach presents worst results when compared with non-fragmentation approaches.

Integration of Wearable Solutions in AAL Environments with Mobility Support

The overall demographic profile of current societies point to a significant growth of the elderly people. Associated with the increase of the average hope of life and consequent increase in chronic diseases, there is the need for protection and daily care. Increasing investments in technology, such as Ambient Assisted Living (AAL) solutions, promote the quality of live extending the time people can live in their desired environment. This paper proposes the design, deployment, and real testbed of an e-health wearable monitoring system based on the integration of several AAL tools and platforms for elderly’s bio-signals monitoring. This solution includes electrocardiography (ECG), respiration rate, beats per minute, body temperature, and falls detention and notification. The paper also describes, in detail, the real pilot and analyzes some early results concerning the users quality of experience, and the found results are very promising.

FTP@VDTN — A file transfer application for Vehicular Delay-Tolerant Networks

Vehicular Delay-Tolerant Networks (VDTNs) aim to provide non-real time services and applications, such as electronic mail or file transfer, in environments with sparse and intermittent connectivity, variable delays, or where an end-to-end connection may not exist. Gathering contributions from opportunistic and cooperative networks, VDTN tries to generalize the delay-tolerant networks concept and apply it to vehicular networks. In VDTNs, data is carried between network nodes using vehicles that allow network connectivity. This paper presents a file transfer application for VDTNs, called FTP@VDTN, and studies its performance through a laboratory VDTN testbed using two routing mechanisms (Epidemic, and Spray and Wait) combined with different scheduling and dropping policies. It was demonstrated that FTP@VDTN works properly in a VDTN testbed. In terms of performance evaluation of VDTNs using FTP@VDTN, it was shown that remaining lifetime combination of scheduling and dropping policies perform better for both routing schemes.