Improving vehicular delay-tolerant network performance with relay nodes

“Copyright © [2009] IEEE. Reprinted from Next Generation Internet Network. NGI '09). ISBN:978-1-4244-4244-7. This material is posted here with permission of the IEEE. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.”Vehicular Delay-Tolerant Networking (VDTN) is an extension of the Delay-Tolerant Network (DTN) architecture concept to transit networks. VDTN architecture handles non-real time applications, exploiting vehicles to enable connectivity under unreliable scenarios with unstable links and where an end-to-end path may not exist. Intuitively, the use of stationary store-and-forward devices (relay nodes) located at crossroads where vehicles meet them and should improve the message delivery probability. In this paper, we analyze the influence of the number of relay nodes, in urban scenarios with different numbers of vehicles. It was shown that relay nodes significantly improve the message delivery probability on studied DTN routing protocols.Part of this work has been supported by the Instituto de Telecomunicações, Next Generation Networks and Applications Group, Portugal, in the framework of the Project VDTN@Lab, and by the Euro-NF Network of Excellence of Seven Framework Programme of EU

Evaluating the impact of storage capacity constraints on vehicular delay-tolerant networks

“Copyright © [2009] IEEE. Reprinted from Second International Conference on Communication Theory Reliability, and Quality of Service, 2009. CTRQ'09. ISBN:978-1-4244-4423-6. This material is posted here with permission of the IEEE. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.”Vehicular Delay-Tolerant Network (VDTN) was proposed as a particular application of a mobile Delay-Tolerant Network (DTN), where vehicles act as the communication infrastructure for the network, relaying messages between the network nodes. In this paper, we consider the use of a VDTN to provide low-cost asynchronous communication between sparse populations spread over a remote vast region. We analyze the influence of the VDTN network node’s storage capacity (buffer size), on the efficiency of four DTN routing protocols, in terms of message delivery probability. Our scenarios show that the routing protocols message replication strategies react differently to the increase of buffer size in specific network nodes. Epidemic and MaxProp protocols benefit from the increase of the storage capacity on all network nodes. Spray and Wait protocol only takes advantage on the increase of the vehicle’s buffer capacity. We expect that this paper will provide a deep understanding of the implications of storage constraints over the performance of a VDTN, leading to insights for future routing algorithm and buffer management theoretic studies and protocol design.Part of this work has been supported by the Instituto de Telecomunicações, Next Generation Networks and Applications Group, Portugal, in the framework of the Project VDTN@Lab, and by the Euro-NF Network of Excellence of Seven Framework Programme of EU

Scheduling and drop policies for traffic differentiation on vehicular delay-tolerant networks

“Copyright © [2009] IEEE. Reprinted from 17th International Conference on Software, Telecommunications & Computer Networks, 2009. SoftCOM 2009.ISBN:978-1-4244-4973-6. This material is posted here with permission of the IEEE. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.”Vehicular Delay-Tolerant Networks (VDTNs) are a promising technology for vehicular communications, creating application scenarios that enable non-real time services with diverse performance requirements. Because of scarce network resources (e.g. bandwidth and storage capacity) and node’s short contact durations, the underlying VDTN network infrastructure must be capable of prioritizing traffic. This paper investigates several scheduling and drop policies, which can be used to implement traffic differentiation. Priority Greedy, Round Robin, and Time Threshold scheduling polices are proposed. In terms of drop policy, the message with the lowest priority and the lowest remaining time-to-live is discarded first. We evaluate their efficiency and tradeoffs, through simulation. The results presented in this paper can be used as a starting point for further studies in this research field, and give helpful guidelines for future VDTN protocol design.Part of this work has been supported by Instituto de Telecomunicações, Next Generation Networks and Applications Group (NetGNA), Portugal, in the framework of the Project VDTN@Lab, and by the Euro-NF Network of Excellence of the Seventh Framework Programme of EU

Impact analysis of the shortest path movement model on routing strategies for VDTNs in a rural region

Vehicular Delay-Tolerant Network (VDTN) appears as a particular application of the Delay-Tolerant Network (DTN) concept to transit networks. In this paper we analyze the use of a VDTN to provide asynchronous Internet access on a rural remote region scenario. Through simulation we evaluate the impact of a shortest path based movement model on the performance of four DTN routing protocols in respect to message delivery probability and message average delay.Part of this work has been supported by the Instituto de Telecomunicações, Portugal, in the framework of the Project VDTN@Lab, and by the Euro-NF Network of Excellence of Seven Framework Programme of EU

Performance analysis of scheduling and dropping policies in vehicular delay-tolerant networks

Vehicular Delay-Tolerant Networking (VDTN) was proposed as a new variant of a delay/disruptive-tolerant network, designed for vehicular networks. These networks are subject to several limitations including short contact durations, connectivity disruptions, network partitions, intermittent connectivity, and long delays. To address these connectivity issues, an asynchronous, store-carry-and-forward paradigm is combined with opportunistic bundle replication, to achieve multi-hop data delivery. Since VDTN networks are resource-constrained, for example in terms of communication bandwidth and storage capacity, a key challenge is to provide scheduling and dropping policies that can improve the overall performance of the network. This paper investigates the efficiency and tradeoffs of several scheduling and dropping policies enforced in a Spray and Wait routing scheme. It has been observed that these policies should give preferential treatment to less replicated bundles for a better network performance in terms of delivery ratio and average delivery delay.Part of this work has been supported by Instituto de Telecomunicações, Next Generation Networks and Applications Group (NetGNA), Portugal, in the framework of the Project VDTN@Lab, and by the Euro-NF Network of Excellence of the Seventh Framework Programme of EU, in the framework of the Project VDTN

Spontaneous Behavior Relationship Management by speed of Information Flow

The strategy implementation, strategic control, spontaneous behavior and successful measurement literature develop a conceptual model and research propositions. In fact, without organizational customers organizations would not exist. The strategic importance of organizational customers is discussed as an asset. Also this paper describes the approach to organizational relationship management at organizations. This paper proposes a relation of organizational relationship management by speed of information flow and reviews the spontaneous behavior strategies and performance measurement literature to develop a conceptual model and research propositions. In fact, organizations influence whether or not those organizations engage in spontaneous behavior strategies. In this field, the focus is on the special characteristics of speed of information flow such as education type and level. The facilitator manager's characteristics showing a significant association with a commitment to organizational relationship management and also organizational relationship management showed a positive association with those speed of information flow with a growth orientation. It is concluded that facilitator manager's characteristics can be important in explaining and compilation the organizational relationship management within the organizations for implementation. This paper is to explore the ways in which certain characteristics of speed of information flow of organizations generate a tendency to prepare formal written spontaneous behavior strategies

VDTNsim: a simulation tool for vehicular delay-tolerant networks

“Copyright © [2010] IEEE. Reprinted from 15th IEEE International Workshop on Computer-Aided Modeling Analysis and Design of Communication Links and Networks.(IEEE CAMAD 2010) ISBN:978-1-4244-7634-3. This material is posted here with permission of the IEEE. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.”Developing an adequate network architecture for supporting data communications in vehicular networks is critical to overcome the challenges caused by highly dynamic network topology, connectivity disruption, and intermittent connectivity issues. Among several approaches available in the literature proposed to address these problems, vehicular delay-tolerant networking (VDTN) architecture appears as a recent and innovative solution that integrates the concepts of end-to-end, asynchronous, and variable-length bundle oriented communication; Internet protocol over VDTN; and out-of-band signaling. VDTN architecture, protocols and services are in a fairly early stage of development. Therefore, simulation appears as an important tool providing a highly flexible, low-cost, and fast answer for research questions, and furnishes important inputs for exploring through prototyping. This paper presents and describes the proposal and construction of a simulation tool for VDTN networks, called VDTNsim.Part of this work has been supported by Instituto de Telecomunicações, Next Generation Networks and Applications Group (NetGNA), Portugal, in the framework of the Project VDTN@Lab, and by the Euro-NF Network of Excellence of the Seventh Framework Programme of EU, in the framework of the Specific Joint Research Project VDTN

Traffic differentiation support in vehicular delay-tolerant networks

Vehicular Delay-Tolerant Networking (VDTN) is a Delay-Tolerant Network (DTN) based architecture concept for transit networks, where vehicles movement and their bundle relaying service is opportunistically exploited to enable non-real time applications, under environments prone to connectivity disruptions, network partitions and potentially long delays. In VDTNs, network resources may be limited, for instance due to physical constraints of the network nodes. In order to be able to prioritize applications traffic according to its requirements in such constrained scenarios, traffic differentiation mechanisms must be introduced at the VDTN architecture. This work considers a priority classes of service (CoS) model and investigates how different buffer management strategies can be combined with drop and scheduling policies, to provide strict priority based services, or to provide custom allocation of network resources. The efficiency and tradeoffs of these proposals is evaluated through extensive simulation.Part of this work has been supported by Instituto de Telecomunicações, Next Generation Networks and Applications Group (NetGNA), Portugal, in the framework of the Project VDTN@Lab, and by the Euro-NF Network of Excellence of the Seventh Framework Programme of EU

Detecting Intra-Fraction Motion in Patients Undergoing Radiation Treatment Using a Low-Cost Wireless Accelerometer

The utility of a novel, high-precision, non-intrusive, wireless, accelerometer-based patient orientation monitoring system (APOMS) in determining orientation change in patients undergoing radiation treatment is reported here. Using this system a small wireless accelerometer sensor is placed on a patient’s skin, broadcasting its orientation to the receiving station connected to a PC in the control area. A threshold-based algorithm is developed to identify the exact amount of the patient’s head orientation change. Through real-time measurements, an audible alarm can alert the radiation therapist if the user-defined orientation threshold is violated. Our results indicate that, in spite of its low-cost and simplicity, the APOMS is highly sensitive and offers accurate measurements. Furthermore, the APOMS is patient friendly, vendor neutral, and requires minimal user training. The versatile architecture of the APOMS makes it potentially suitable for variety of applications, including study of correlation between external and internal markers during Image-Guided Radiation Therapy (IGRT), with no major changes in hardware setup or algorithm

Exploiting node localization for performance improvement of vehicular delay-tolerant networks

“Copyright © [2010] IEEE. Reprinted from IEEE International Conference on Communications (IEEE ICC 2010) - General Symposium on Selected Areas in Communications (ICC'10 SAS).ISSN:1550-3607. This material is posted here with permission of the IEEE. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.”Vehicular Delay-Tolerant Networks (VDTNs) are characterized by high node mobility, intermittent connectivity, and short contact durations. Such factors cause incomplete transmissions and the waste of link capacity. To address these issues, this paper explores the use of node localization in VDTNs. The exchange of signaling information related to nodes’ real-time location, current trajectory, velocity, and transmit range allows a Contact Prediction Algorithm to estimate contact durations. This information can be used in conjunction with additional signaling information (e.g. link data rate), to determine the maximum number of bytes that can be transmitted during contact opportunities. A Contact Duration Scheduling Policy can use this information to prevent incomplete transmissions, while increasing the number of successfully relayed bundles and improving data link utilization. Through a simulation study, we investigate the benefits of introducing the concept of node localization, and evaluate the performance of the proposed Contact Prediction Algorithm and Contact Duration Scheduling Policy. We demonstrate the gains introduced by this approach in comparison with an environment where VDTN nodes have no access to localization information.Part of this work has been supported by Instituto de Telecomunicações, Next Generation Networks and Applications Group (NetGNA), Portugal, in the framework of the Project VDTN@Lab, and by the Euro-NF Network of Excellence from the Seventh Framework Programme of EU