Delay/Disruption Tolerant Networks Routing Research Articles

Geo-DMP: A DTN-Based Mobile Prototype for Geospatial Data Retrieval

Geospatial information is gaining immense interest and importance as we enter the era of highly developed transportation and communication. Despite the proliferation of cellular network and WiFi, on some occasions, users still face barriers to accessing geospatial data. In this paper, we design and implement a distributed prototype system with a delay/disruption tolerant network (DTN), named Geo-DMP, for cooperatively and opportunistically sharing and exchanging named geospatial contents in a device-to-device fashion. First of all, we construct a lightweight “content agent” module to bridge the gap between the application layer and the underlying DTN protocol stack. Afterwards, to profile the mobility history of users in practical geospatial environments, we present a map segmentation scheme based on road network and administrative subdivision information. Subsequently, we associate the regional movement history information with the content retrieval process to devise a hierarchical and region-oriented DTN routing scheme for both requests and responses. Finally, we conduct extensive experiments with real-world trajectories and complete implementations on the emulation platform composed of virtual machines. The experiments corroborate that Geo-DMP has the capability of successfully retrieving geospatial contents for users for most of the time under mobile circumstances with episodic connectivity. Moreover, en-route caches can be efficiently exploited to provision contents from multiple sources with less network resource consumption and shorter user-perceived latencies.

A Greedy Routing Strategy Based on Euclidean Geometry for Vehicular Delay Tolerant Network

Delay/Disruption-Tolerant Networks (DTN) was initially used for Inter-Planetary Networks (IPN) and it was extended to many different scenarios characterized by the high mobility of nodes, the constant disconnection and high delays, such as Vehicular Networks (VANETs), Sensor Networks, Military Ad Hoc Networks and Networks in catastrophic scenarios, Pocket Switched Networks (PSN) and Under-Water Networks. A key challenge in an DTN-based environment is the message routing protocol that enables communication between any two nodes (at any time) because it must deal with possible unconnected end-to-end paths at the time of sending a message to a destination. This paper presents a Greedy DTN Routing Strategy Based on Euclidean Geometry (GREG) for Vehicular Delay Tolerant Network, where a mathematical model is employed to predict the position of the nodes. GREG algorithm computes, based on prediction positions computed, the distance between the node currently holding the message and the destination node. An Euclidean Geometry distance between two points is used. Results show that the GREG protocol has a good trade-off between routing efficacy and network resource consumption.

DCAR: DTN Congestion Avoidance Routing Algorithm Based on Tokens in an Urban Environment

When a delay/disruption tolerant network (DTN) is applied in an urban scenario, the network is mainly composed of mobile devices carried by pedestrians, cars, and other vehicles, and the node’s movement trajectory is closely related to its social relationships and regular life; thus, most existing DTN routing algorithms cannot show efficient network performance in urban scenarios. In this paper, we propose a routing algorithm, called DCRA, which divides the urban map into grids; fixed sink stations are established in specific grids such that the communication range of each fixed sink station can cover a specific number of grids; these grids are defined as a cluster and allocated a number of tokens in each cluster; the tokens in the cluster are controlled by the fixed sink station. A node will transmit messages to a relay node that has a larger remaining buffer size and encounters fixed sink stations or the destination node more frequently after it obtains a message transmit token. Simulation experiments are carried out to verify the performance of the DCAR under an urban scenario, and results show that the DCAR algorithm is superior to existing routing algorithms in terms of delivery ratio, average delay, and network overhead.

Delay/Disruption Tolerant Network-Based Message Forwarding for a River Pollution Monitoring Wireless Sensor Network Application.

Communications from remote areas that may be of interest is still a problem. Many innovative projects applied to remote sites face communications difficulties. The GOLDFISH project was an EU-funded project for river pollution monitoring in developing countries. It had several sensor clusters, with floating WiFi antennas, deployed along a downstream river’s course. Sensor clusters sent messages to a Gateway installed on the riverbank. This gateway sent the messages, through a backhaul technology, to an Internet server where data was aggregated over a map. The communication challenge in this scenario was produced by the antennas’ movement and network backhaul availability. Since the antennas were floating on the river, communications could be disrupted at any time. Also, 2G/3G availability near the river was not constant. For non-real-time applications, we propose a Delay/Disruption Tolerant Network (DTN)-based solution where all nodes have persistent storage capabilities and DTN protocols to be able to wait minutes or hours to transmit. A mechanical backhaul will periodically visit the river bank where the gateway is installed and it will automatically collect sensor data to be carried to an Internet-covered spot. The proposed forwarding protocol delivers around 98% of the messages for this scenario, performing better than other well-known DTN routing protocols.

A Survey on Geographic Routing Protocols in Delay/Disruption Tolerant Networks

Delay/Disruption Tolerant Networks (DTNs) have been attracting great interest from research community, where data communication naturally does not require contemporaneous end-to-end connectivity. Although they are suffering from a large variation of network topology, numerous previous routing protocols proposed for DTNs still make effort to qualify delivery potential, via network topology information. Geographic routing is an alternative, conceptually, by relying on the geographic information instead of topological information. In the literature, since this technique branch has not been extensively investigated in DTNs, our paper identifies the motivation and challenges for applying geographic routing in DTNs with the state of the art. Also, we highlight the future research directions for this branch.

A DTN-based architecture for public transport networks

Delay/disruption-tolerant networking has been exploited in a variety of communication scenarios to provide basic delay-tolerant Internet services. In this paper, we propose a delay/disruption-tolerant networking (DTN)-based architecture for dense urban environments that exploits the existing infrastructure of public transport networks to provide Internet services through applications that can withstand certain delays without significantly affecting user experience. To achieve data delivery within the delay tolerance threshold that each user defines, we couple the proposed architecture with the enhanced connectivity plan routing protocol (CARPOOL+) that includes smart mechanisms for route calculation. In particular, the proposed architecture exploits both scheduled and opportunistic contact opportunities and mitigates the impact of typical delays caused by traffic, road accidents, etc. Our simulation results show that the proposed architecture achieves high delivery ratio with low latency, even when significant delays occur. We also compare CARPOOL+ with the most well-known DTN routing solutions and show that CARPOOL+ achieves the highest delivery ratio with the lowest overhead.

Delay and Lifetime Performance of Underwater Wireless Sensor Networks with Mobile Element Based Data Collection

Underwater Wireless Sensor Networks (UWSNs) may be easily partitioned due to resource constraints and sparse deployment, and such UWSNs need to be treated as Delay/Disruption Tolerant Networks (DTN). The principal objective of DTN routing is to maximize the possibility of eventual data delivery, which can be achieved only at the cost of high energy consumption and/or increased message latency. The energy efficiency and network lifetime are more important than data collection latency for certain underwater applications. We consider energy-efficient data collection using mobile elements, which is suitable for long-term sensing applications that are not time-critical. Using different analytical models, we investigate energy efficiency, network lifetime, packet delivery ratio, and message latency in a mobility-assisted data collection framework for UWSNs. The analytical models are validated with the experimental setup developed using the NS-2 based Aqua-Sim simulator. The results demonstrate that the proposed framework shows superior performance in terms of energy efficiency, network lifetime, and packet delivery ratio at the cost of increased message latency. The analytical models for delay performance are compared to see that the polling model is more effective in modelling the mobility-assisted data collection framework for UWSNs and more flexible in implementing different service policies.

Local information-based congestion control scheme for space delay/disruption tolerant networks

The storage resources and communication opportunities in space delay/disruption tolerant networks (DTN) are usually very limited. Moreover, as the links in space DTN are often subject to long delay, intermittent connectivity and asymmetric bandwidth, end-to-end continuous path may not be guaranteed and messages may stay at intermediate nodes for a long time. Thus, congestion in space DTN, which takes the form of persistent storage exhaustion, is inevitable. Due to the intrinsic features of space DTN, congestion control should be performed with local information before congestion occurs and limited storage and communication resources should be allocated to messages that have the highest probability to be delivered to destination. Based on these principles, a local information-based congestion control (LCC) scheme for space DTN is proposed in this paper. Firstly, LCC attempts to relieve the storage pressure by using alternative paths i.e. non-best paths when the network is about to congest. Secondly, LCC adopts a utility function based on the reciprocal of hop counts to destination to assist forwarding decision and queue management. Simulation results show that with the combination of LCC typical space DTN routing algorithm can achieve higher message delivery ratio and more uniform traffic distribution.

Survey on underwater delay/disruption tolerant wireless sensor network routing

Underwater wireless sensor networks (UWSNs) have recently received a significant amount of attention. Since they have delay/disruption-tolerant networks (DTNs) characteristics, the design of any UWSN scheme must take DTN influences into account, especially in routing protocols. Many researchers have proposed various DTN routing techniques for different types of DTN routing schemes in UWSNs. The authors survey state-of-the-art DTN routing protocols, and use the definition of DTN to classify these proposals into scheduled contact, opportunistic contact and predicted contact. Furthermore, the authors analyse the detailed information in order to draw up a comparison table and also expect to inspire more research into this topic in the future.

A blind mechanism to improve content distribution in delay/disruption tolerant networks

In Delay/Disruption Tolerant Networks (DTNs), content distribution is performed leveraging on the transient and dynamic contacts between moving users. Such a best effort mechanism is prone to unbounded downloading delays and bad user experience. To cope with these occurrences, this paper introduces a novel mechanism to improve content distribution in DTNs. The proposed mechanism is based on the Delay Tolerant Transport Protocol (DTTP)and aims at controlling the diversity in the coded information transmission without increasing the use of network resources or including any feedback messages. In order to validate the proposed mechanism, different scenarios have been evaluated using known DTNs routing protocols. The results show significant gains achieved in terms of delivery ratio in all evaluated scenarios, confirming the efficiency and effectiveness of our protocol independently of the lower layer protocols in use.

Converge-and-Diverge: A Geographic Routing for Delay/Disruption-Tolerant Networks Using a Delegation Replication Approach

Routing in delay/disruption-tolerant networks (DTNs) is without the assumption of contemporaneous end-to-end connectivity to relay messages. Geographic routing is an alternative approach using real-time geographic information instead of network topology information. However, if considering the mobility of destination, its real-time geographic information is often unavailable due to sparse network density in DTNs. Using historical geographic information to overcome this problem, we propose the converge-and-diverge (CaD) by combining two routing phases that depend on the proximity to the movement range estimated for destination. The key insight is to promote message replication converging to the edge of this range and diverging to the entire area of this range to achieve fast delivery, given limited message lifetime. Furthermore, the concept of delegation replication (DR) is explored to overcome the limitation of routing decisions and the local maximum problem. Evaluation results under the Helsinki city scenario show an improvement of CaD in terms of delivery ratio, average delivery latency, and overhead ratio. Since geographic routing in DTNs has not received much attention, apart from the design of CaD, our novelty also focuses on exploring DR to overcome the limitation of routing decision and the local maximum problem, in addition to enhancing efficiency, as DR originally intended.

Routing in Delay/Disruption Tolerant Networks: A Taxonomy, Survey and Challenges

The introduction of intelligent devices with short range wireless communication techniques has motivated the development of Mobile Ad hoc NETworks (MANETs) during the last few years. However, traditional end-to-end based routing algorithms designed for MANETs are not much robust in the challenged networks suffering from frequent disruption, sparse network density and limited device capability. Such challenged networks, also known as Intermittently Connected Networks (ICNs) adopt the Store-Carry-Forward (SCF) behavior arising from the mobility of mobile nodes for message relaying. In this article, we consider the term ICNs as Delay/Disruption Tolerant Networks (DTNs) for the purpose of generalization, since DTNs have been envisioned for different applications with a large number of proposed routing algorithms. Motivated by the great interest from the research community, we firstly review the existing unicasting issue of DTNs because of its extensive research stage. Then, we also address multicasting and anycasting issues in DTNs considering their perspectives. A detail survey based on our taxonomy over the period from 2006 to 2010 is not only provided but also a comparison is given. We further identify the remaining challenges and open issues followed by an evaluation framework proposed for routing in DTNs. Finally, we summarize our contribution with three future research topics highlighted.

Reach-and-Spread: A historical geographic routing for delay/disruption tolerant networks

Although geographic routing is an alternative approach to topology routing in delay/disruption tolerant networks (DTNs), sparse network density and high mobility result in challenges to obtain the real time geographic information of destination if taking its mobility into account. Furthermore, sparse network density is also in contrast with high-network density, for handling the local maximum problem that the message carrier cannot find a better candidate node to relay a message. In this article, the authors investigate geographic routing in DTNs from another perspective, assuming the real time geographic information of mobile destination is always unavailable. The key insight is to estimate the movement range of the destination using its historical geographic information, to promote message replication reaching the edge of this range using a Reach Phase and spreading within this range using a Spread Phase. Then, these two phases are combined to promote message delivery within the limited message lifetime. The evaluation of results under the Helsinki city scenario show the advantage of our proposed Reach-and-Spread in terms of delivery ratio and average delivery latency as well as overhead ratio.

도시 환경에서 지역적 주기성을 이용한 DTN 라우팅 기법

Delay/Disruption Tolerant Network (DTN)은 엔드-투-엔드 연결이 없더라도 중간 노드들의 이동성과 저장공간을 활용하여 궁극적으로 데이터를 전달시켜 주는 네트워크 패러다임으로써 장시간 전송을 요하는 고용량 데이터전송 또는 높은 이동성의 무선통신, 행성간 통신 같은 불완전한 망 연결에 적합하다. 본 논문에서는 노드의 지역적 주기성을 이용하는 새로운 DTN 라우팅 기법을 제안한다. 각각의 노드가 주기적으로 방문하는 고유의 영역을 가지는 성질을 지역적 주기성이라 정의하고 실제 상하이 4000대의 택시 데이터를 분석하여 이를 실험적으로 입증한다. 또한 각 차량 고유의 지역적 주기성을 대표하는 값으로써 Weighted Center (WC)의 개념을 소개한다. 도시 환경에서 곳곳에 고르게 분포되어 있는 Access Point (AP) 들을 통해 차량들이 자신이 속한 그리드의 정보를 얻고 이를 통해 자신의 WC를 계산할 때, 자신과 주변 차량들의 WC정보만을 이용해 메시지의 경로를 결정 하는 분산화된 Diff WC라우팅 기법을 제안한다. 신뢰도 높은 데이터를 제공하는 1486대의 상하이 택시 환경에서의 시뮬레이션을 통해 ECT, LET 등의 기존 DTN 라우팅 방식과 비교하여 10%~110%의 전달률 개선이 가능함을 검증한다. The Delay/Disruption Tolerant Network (DTN) is a network designed to operate effectively using the mobility and storage of intermediate nodes under no end-to-end guaranteed network. This new network paradigm is well-suited for networks which have unstable path and long latencies (e.g. interplanetary network, vehicular network). In this paper, we first found that each taxi has its own regularly visiting area and define this property as spatial regularity. We analyze 4000 taxi trace data in Shanghai and show the existence of spatial regularity experimentally. Based on a spatial regularity in urban environment, we present a new DTN routing method. We introduce a Weighted Center (WC) which represents spatial regularity of each node. Through the association with evenly distributed access points (APs) in urban environment, most of vehicles get their grid locations and calculate their WCs. Since our routing method only uses neighbors' WCs for building routing paths, it can be regarded as distributed and practical protocols. Our experiments involving realistic network scenarios created by the traces of about 1500 Shanghai taxies show that our routing method achieves the higher performance compared to ECT, LET by 10%~110%.

Reasonable routing in delay/disruption tolerant networks

Delay/disruption tolerant networking (DTN) is an approach to networking where intermittent connectivity exists: it is often afforded by a store and forward technique. Depending on the capability of intermediary nodes to carry and forward messages, messages can be eventually delivered to their destination by mobile nodes with an appropriate routing protocol. To have achieved a successful delivery, most DTN routing protocols use message duplication methods. Although messages are rapidly transferred to the destination, the redundancy in the number of message copies increases rapidly. This paper presents a new routing scheme based on a stochastic process for epidemic routing. Message redundancy is efficiently reduced and the number of message copies is controlled reasonably. During the contact process of nodes in the network, the number of message copies changes, and according to the variability in the number of copies, we construct a special Markov chain, birth and death process, on the number of message copies then calculate and obtain a stationary distribution of the birth and death process. Comparing the theoretical model with the simulation we have performed we see similar results. Our method improves on time-to-live (TTL) and antipacket methods, in both redundancy and delivery success efficiency.

HYMAD: Hybrid DTN-MANET routing for dense and highly dynamic wireless networks

Delay/Disruption-Tolerant Network (DTN) protocols typically address sparse intermittently connected networks whereas Mobile Ad-hoc Network (MANET) protocols address the fairly stable and fully connected ones. But many intermediate situations may occur on mobility dynamics or radio link instability. In such cases, where the network frequently splits into evolving connected groups, none of the conventional routing paradigms (DTN or MANET) are fully satisfactory. In this paper we propose HYMAD, a Hybrid DTN-MANET routing protocol which uses DTN between disjoint groups of nodes while using MANET routing within these groups. HYMAD is fully decentralized and only makes use of topological information exchanges between the nodes. The strength of HYMAD lies in its ability to adapt to the changing connectivity patterns of the network. We evaluate the scheme in simulation by replaying synthetic and real life mobility traces which exhibit a broad range of connectivity dynamics. The results show that HYMAD introduces limited overhead and outperforms the multi-copy Spray-and-Wait DTN routing protocol it extends, both in terms of delivery ratio and delay. This hybrid DTN-MANET approach offers a promising venue for the delivery of elastic data in mobile ad-hoc networks as it retains the resilience of a pure DTN protocol while significantly improving performance.

Routing Techniques on Delay/Disruption Tolerant Networks

作为一种新型的体系结构,容延容断网络(delay/disruption tolerant network,简称DTN)近年来得到了广泛的研究与应用.由于其面临的应用环境极为特殊,传统网络的路由协议无法适用于DTN,各种针对DTN的路由技术相继提了出来.在对DTN路由进行形式化分析以后,提出了路由技术的分类方法,然后着重分析并比较了当前一些较为重要的路由技术的核心路由机制和特点.最后总结DTN路由技术的研究现状以及存在的问题,指出未来路由研究的重点.;In the recent years, as a new emerging network architecture, Delay/Disruption Tolerant Networks (DTNs) have received extensive attention and are widely investigated. Since the major application scenarios of DTN are extremely particular routing protocols designed for the traditional networks are not suitable for DTN. Therefore, numerous routing protocols have been proposed for DTN. In this paper, the formulation issues of DTN routing protocols are firstly studied, and the classification concerns are then proposed for those protocols. Thereafter, this paper focuses on analyzing and comparing existing representative DTN routing protocols. Finally, current research status and the existing problems about DTN routing protocols are summarized, the key issues and future trends in DTN routing are pointed out.

Delay/disruption tolerant mobile ad hoc networks: latest developments

AbstractThere is much research activity in the emerging area of delay/disruption tolerant networks (DTN) in the past few years. DTNs pose many new challenges, and protocols designed for wired Internet or wireless mobile ad hoc networks do not work properly in DTNs. Routing is one of the key components in DTNs and the message ferry (MF) approach has been drawn a lot of attention to support routing in DTNs. Besides the underlying routing protocols, issues in transport layer are also very important and need to be addressed for DTNs. Recently, many new routing protocols, including unicast using the MF approach, inter‐region routing and multicast, have appeared in the literature. There are also a few works addressing issues in the transport layer. This paper provides an overview on recent developments including message ferrying, multicast support, inter‐region routing, and transport layer issues. It also points out some open research issues and intends to motivate new research and development in this area. Copyright © 2007 John Wiley & Sons, Ltd.