Delay Tolerant Networks Applications Research Articles

Network Path Optimization Strategy using Collaborative Cache for Delay Tolerant Networks

The data transmissions over Delay Tolerant Networks (DTN) and Social-based Opportunistic networks have increased in the last few years due to a higher demand for remote transmissions. The wide applications of DTN have significantly motivated the researchers to focus on finding optimized routing strategies by optimizing various parameters such as energy, cost and congestion. Nonetheless, these parallel research outcomes have reported few further bottlenecks to improve the strategies. Henceforth, this work proposes a novel approach to optimize the routing paths using the cache collaboration method. This proposed method identifies the data-sharing strategies and subsequently identifies the sub-set of the paths between the source and destinations. Further optimizes the path using standard measures such as cost, transmission speed, and the network traffic conditions; lastly Data-Centric and Cost Optimized Routing Path is Identification. This work results in a nearly 20% reduction in the distance between the nodes, a 15% reduction of time in path identification and a nearly 50% reduction in cache allocation demand over multiple iterations compared to the existing models.

A cooperative mobile throwbox-based routing protocol for social-aware delay tolerant networks

In delay tolerant networks (DTNs), nodes have intermittent connectivity patterns due to various factors such as mobility, sparse network topology, and unpredictable movement patterns. In such networks, nodes store messages, carry them along as they move and forward them opportunistically whenever an encounter occurs. In many DTN applications, such as in disaster situations and remote regions with no communications infrastructure, we can envisage a network topology formed by the mobility and contact pattern of people carrying their mobile devices. The social behavior of people (nodes) in Spatio-temporal dimensions governs the formation of such a topology. To improve data dissemination in such networks, several works have proposed to utilize social-aware metrics for the selection of relays. However, existing routing protocols for DTNs may perform poorly in the scenarios in which nodes are localized in multiple small regions, and the topology is sparse such as in co-located villages in remote regions with no communication infrastructure. This work proposes a Cooperative mobile throwbox-based routing protocol (CMTR) for social-aware DTNs. In CMTR, static and mobile ThrowBoxes (TBs) are deployed to improve the efficiency of a DTN. The static and mobile TBs cooperatively relay data to enhance network efficiency. Performance evaluation via simulations in ONE simulator shows that CMTR improves the data delivery ratio, delays, and energy efficiency as compared to Epidemic routing and Bubble Rap routing schemes.

Energy consumption analysis of different routing protocols in a Delay Tolerant Network

In this paper, we use the Opportunistic Network Environment environment to simulate a data collection application using a Delay Tolerant Network (DTN). A group of sensor nodes sense data from the environment and send these data to a destination node that collects them for statistical and data analysis purposes. Pedestrians and cyclist equipped with smart devices moving in Tirana city roads, will relay the sensed data via opportunistic contacts. Different simulations are done to identify among five routing protocols the most suitable for our DTN application.

Time-constrained anycast routing under short contact duration in delay-tolerant networks

Delay-tolerant networks (DTNs) are sparse mobile ad hoc networks, in which there is typically no complete path between the source and destination. Anycast is an important group communication paradigm for numerous DTN applications such as resource discovery and information exchange in emergency or crisis situations. Unlike unicast and multicast, which have been studied extensively in DTNs, few prior works have addressed the DTN anycast routing problem. Furthermore, they often ignore the time constraint and assume long contact durations in formulating the relay selection strategy. In this paper, we study a single-copy time-constrained anycast (TCA) routing under short contact duration. We address two key issues: (1) to which next hop relay node should messages be forwarded and (2) in which order should messages be forwarded. To reduce the transmission cost, we select relay nodes from both current and past contacts based on the one-hop and two-hop delivery probabilities, respectively. We derive the delivery probability from the distribution of inter-contact time and contact duration time. We address the case of exponential and Pareto distribution, which are the most popular assumptions in literature. For the message scheduling, messages with the highest delivery probability are prioritized to be transmitted first. Extensive simulation results based on Cabspotting and MIT Reality traces show that our scheme can achieve up to 29% higher delivery rate, 24% lower delay, and 36% lower transmission cost compared to other anycast routing strategies.

Social contact graph-based group communication schemes for delay tolerant networks

Delay-tolerant networks (DTNs) are sparse mobile ad hoc networks in which there is typically no complete path between the source and destination. Multicast and anycast are important group communication paradigms for numerous DTN applications. For example, multicast is used to disseminate real-time traffic information reporting and software patch to multiple devices, and anycast is used for resource discovery and information exchange in emergency or crisis situation. While multicast and anycast have been studied extensively in the context of the Internet and Mobile Ad-Hoc Networks (MANETs), efficient multicast and anycast in DTNs are significantly different and challenging problems due to frequent partitions and intermittent connectivity among nodes. In this paper, we propose single-copy routing strategies for multicast and anycast based on the multi-hop delivery probabilities. Multicast employs a dynamic tree branching technique that allows routing paths to be efficiently shared among multicast destinations. Anycast selects relay nodes based on social distances to anycast group members. It balances the trade-off between a short path to the closest, single group member and a longer path to the area where many other group members reside. That is, it optimises both the efficiency and robustness of message delivery. Through extensive simulation studies using a real-world mobility trace, we show that our schemes achieve a high delivery ratio, low delay, and low (or comparable) transmission cost compared to other group communication strategies.

Analysis of human mobility patterns for opportunistic forwarding in shopping mall environments

Mobility plays a key role in the forwarding of data in delay-tolerant mobile ad hoc networks, as it is mobility that gives rise to local connection opportunities. Different patterns of mobility may give rise to different opportunity for communication, and different protocols may be more effective in particular situations. It is thus becoming increasingly important to understand user mobility patterns. In this paper, we seek to improve understanding of human mobility patterns in environments having definite and highly organized structure, such as shopping malls. We analyze contact traces between devices carried by people in a medium-scale shopping mall to characterize human mobility in such an environment. This will allow us to design suitable routing algorithms for delay-tolerant network applications for such scenarios as well as to develop and validate a novel mobility model which can be used by the research community to simulate mobile networks in such settings. We show that people’s motion is different according to their relationship to the environment in which they are and present a method to identify individuals expressing different mobility patterns based on delay-tolerant network metrics. From the contact traces, we identify two main groups with different mobility patterns that we name customers and sellers. For these two groups, we observe and quantify mobility characteristics, and present real-world measurement results. Finally, to understand better the role of groups of message carriers expressing different mobility patterns, we perform simulations of a derivative of the Epidemic protocol with real-world mobility traces, which distinguishes between two groups of carriers and entrusts messages through either one or the other. We discuss the implications of our results and make recommendations to guide the design of ad hoc forwarding algorithms for delay-tolerant mobile ad hoc networks in shopping mall environments and to help model realistic simulation scenarios.

GTDM: A DTN Routing on Noncooperative Game Theory in a City Environment

The performance of delay tolerant networks (DTNs) can be influenced by movement model in different application environments. The existing routing algorithms of DTNs do not meet the current city environments due to the large differences in node densities, social characteristics, and limited energy. The key indicators of DTNs such as success delivery ratio, average delivery latency, network lifetime, and network overhead ratio can influence the performances of civil DTNs applications. Aiming to improve the key indicators of DTNs in city environments, this paper presents a fixed sink station based structure and a more proper routing algorithm named Game Theory Based Decision Making (GTDM). GTDM shows decision-making process for neighborhood selection and packet delivering strategy which is based on the noncooperative game theory method and city environment characteristics. GTDM performance is evaluated using numerical simulations under Working Day Movement (WDM) model and the results suggested that GTDM outperforms other traditional DTNs routing approaches, such as Epidemic and Prophet algorithms.

E-ONE:Enhanced ONE for Simulating Challenged Network Scenarios

Delay Tolerant Network (DTN) empowers sparse mobile ad-hoc networks and other challenged network environments, such as interplanetary communication network or deep sea communication network, where traditional networking protocols either fail to work completely or do not work well. The Opportunistic Networking Environment (ONE) Simulator has gained considerable popularity as an efficient tool for validating and analysing DTN routing and application protocols. It provides options for creating different mobility models and routing strategies as per the users’ requirements. Nowadays, challenged networks such as rural internet connection, social networks, post-disaster communication systems, etc. use DTN along with some hybrid infrastructure networks. Incorporating such real life network systems in ONE needs extensive modification of the same. In this paper, we present the enhanced ONE (e-ONE) simulator as an extension of ONE to facilitate simulation of challenged networks and describe the enhancements we have added to the ONE. As a case study, we consider a challenged network, which we call a latency aware 4-tier planned hybrid architecture designed for post-disaster management. We describe, in detail, how this enhanced version of the ONE simulator is useful in analysis and evaluation of the scenario considered.

Particle swarm optimization in intelligent routing of delay-tolerant network routing

Delay-tolerant networks (DTNs) are wireless partitioned networks. Because of intermittency, mobile ad hoc network (MANET) routing protocols are not efficient in DTNs. Wildlife tracking, vehicular networks, interplanetary networks, etc. are different applications of DTN. Regarding DTN applications, different parameters should be considered while designing DTN routing protocols. Message delivery ratio, message delivery delay, overhead, message drop, etc. are some important factors that are usually considered in routing algorithms. This paper proposes a method which tries to reduce overhead and message drop while increasing message delivery ratio. Choosing the appropriate number of message copies to distribute in the network is important. Few numbers of copies can lead to message drop. So, the message cannot be delivered to the destination. On the other hand, increasing the number of copies causes overhead increase in the network. The proposed algorithm uses particle swarm optimization (PSO) in intelligent choosing of number of message copies. Regarding message delivery ratio and network overhead, PSO greatly helps in finding the suitable number of copies. In order to evaluate our method, which is called PSODTN, we compared it with epidemic routing (ER) and probabilistic routing protocol using history of encounters and transitivity (PROPHET). PSODTN helps to reduce overhead, on average, 95.6% compared to ER and PROPHET. While reducing overhead, PSODTN message delivery ratio is on average 98%.

Mobility Models for Delay Tolerant Network: A Survey

Delay Tolerant Network (DTN) is an emerging networking technology that is widely used in the environment where end-to-end paths do not exist. DTN follows store-carry-forward mechanism to route data. This mechanism exploits the mobility of nodes and hence the performances of DTN routing and application protocols are highly dependent on the underlying mobility of nodes and its characteristics. Therefore, suitable mobility models are required to be incorporated in the simulation tools to evaluate DTN protocols across many scenarios. In DTN mobility modelling literature, a number of mobility models have been developed based on synthetic theory and real world mobility traces. Furthermore, many researchers have developed specific application oriented mobility models. All these models do not provide accurate evaluation in the all scenarios. Therefore, model selection is an important issue in DTN protocol simulation. In this study, we have summarized various widely used mobility models and made a comparison of their performances. Finally, we have concluded with future research directions in mobility modelling for DTN simulation.

Delivery ratio- and buffered time-constrained: Multicasting for Delay Tolerant Networks

Almost all multicast routing algorithms for Delay Tolerant Networks (DTNs) mainly focus on improving routing performance, but hardly consider the constraints in actual DTN applications. In this paper, we investigate the constrained multicasting problems in social network scenarios. A pattern of constrained multicasting is defined, and then based on the node mobility in social network scenarios that the pair-wise inter-contact time is exponentially distributed, we propose a Delivery Ratio- and Buffered Time-Constrained Multicast routing algorithm, named as DBCM. DBCM considers the delivery predictability as utility value within the maximum buffered time, and makes routing decisions based on the utilities of current neighbors. To utilize contact more effectively, an enhanced scheme of DBCM, called E_DBCM, is introduced. E_DBCM can increase message delivery ratio without inducing additional overhead. The performance of DBCM is analyzed theoretically in terms of message delivery ratio, average number of hops and end-to-end delay. We also develop the RWP mobility model, and propose a social mobility based version (SM_RWP). Pair-wise inter-contact time in SM_RWP is proven to follow exponential distribution. Simulation results show that DBCM and E_DBCM outperform the most of the existing multicasting algorithms on delivery ratio and routing overhead.

Economy driven content dissemination in Delay Tolerant Networks

Majority of the existing Delay Tolerant Network (DTN) routing protocols attempt to minimize the message delay, forwarding count, or required storage. However, for many DTN applications such as distributing commercial content, targeting the best performance for only one index and neglecting the others is insufficient. A more practical solution would be to strike a balance between multiple of those performance indices. This paper introduces a Gain-aware Dissemination Protocol (GDP) which attempts to reach the maximum economic gain of content delivery by maintaining a balance between the value achieved via message delivery and the involved forwarding costs given out as user rebates. Economic gain from disseminating content is defined as the generated value upon content delivery minus its forwarding costs. The key concept behind the proposed protocol is to adaptively balance between dissemination latency and forwarding costs in order to maximize the economic gain. Using the DTN simulation software ONE, we characterize the GDP protocol with varying mobility models, content sources, and content generation times.

A Survey of Social-Aware Routing Protocols in Delay Tolerant Networks: Applications, Taxonomy and Design-Related Issues

In the past few years, more and more researchers have paid close attention to the emerging field of delay tolerant networks (DTNs), in which network often partitions and end-to-end paths do not exist nearly all the time. To cope with these challenges, most routing protocols employ the store-carry-forward strategy to transmit messages. However, the difficulty of this strategy is how to choose the best relay node and determine the best time to forward messages. Fortunately, social relations among nodes can be used to address these problems. In this paper, we present a comprehensive survey of recent social-aware routing protocols, which offer an insight into how to utilize social relationships to design efficient and applicable routing algorithms in DTNs. First, we review the major practical applications of DTNs. Then, we focus on understanding social ties between nodes and investigating some design-related issues of social-based routing approaches, e.g., the ways to obtain social relations among nodes, the metrics and approaches to identify the characteristics of social ties, the strategies to optimize social-aware routing protocols, and the suitable mobility traces to evaluate these protocols. We also create a taxonomy for social-aware routing protocols according to the sources of social relations. Finally, we outline several open issues and research challenges.

An Optimal Relaying Scheme for Delay-Tolerant Networks With Heterogeneous Mobile Nodes

To provide communication services in delay-tolerant networks (DTNs) where there may exist no end-to-end paths between mobile node pairs, a variety of relaying and routing algorithms have been proposed under the assumption that the mobile nodes are homogeneously distributed in the network with the same contact rate and delivery cost. However, experimental data have revealed the heterogeneous contact rates between node pairs, and various applications of DTNs have shown that the mobile nodes often belong to different types in terms of energy consumption, communication ability, and other properties. Following the philosophy of exploiting the heterogeneous features of nodes to enhance the routing performance, we design an optimal relaying scheme for DTNs, which takes into account the nodes' heterogeneous contact rates and delivery costs when selecting relays to minimize the delivery cost while satisfying the required message delivery probability. We use the trace-driven simulations to demonstrate the effectiveness of our optimal relaying scheme in various distributions of nodes' delivery costs and mobility environments. Simulation results show that our proposed optimal relaying scheme requires the least delivery cost and achieves the largest maximum delivery probability, compared with the schemes that neglect or do not fully take into account nodes' heterogeneity.

Flow-Based Transmission Scheduling in Constrained Delay Tolerant Networks

Abstract—Routing is one of the most challenging problems in Delay-Tolerant Networks (DTNs) due to network partitioning and intermittent connectivity. Most existing protocols are based on unlimited bandwidth and buffer size. Previous protocols based on limited bandwidth or buffer size (e.g., MaxProp, RAPID, etc) only consider the scenario that each node has at most one contact opportunity during any time interval, and discuss the packet scheduling mechanisms for each separate contact to minimize the average delivery delay. However, in many applications of DTNs, more than one contact opportunities with the same source node, which are called as related contact opportunities, may arise in the same time interval. But previous scheduling algorithms cannot apply to such applications. Therefore, we propose a more general scheduling algorithm to optimize the delivery delay in constrained DTNs including the scenario that multiple related contact opportunities may arise in the same interval, called Flow-Based Transmission Scheduling (FBTS). We evaluate it on publicly available data sets against MED, MaxProp and RAPID. The results show that the delivery delay of FBTS is at least 35% shorter than that of existing works.

A dynamic multicast tree based routing scheme without replication in delay tolerant networks

Delay tolerant networks (DTNs) are a special type of wireless mobile networks which may lack continuous network connectivity. Multicast is an important routing function that supports the distribution of data to a group of users: a service needed for many potential DTN applications. While multicasting in the Internet and in mobile ad hoc networks has been studied extensively, efficient multicasting in DTNs is a considerably different and challenging problem due to the probabilistic nature of contact among nodes. This paper aims to provide a non-replication multicasting scheme in DTNs while keeping the number of forwardings low. The address of each destination is not replicated, but is assigned to a particular node based on its contact rate level and active level. Our scheme is based on a dynamic multicast tree where each leaf node corresponds to a destination. Each tree branch is generated at a contact based on the compare–split rule proposed in this paper. The compare part determines when a new search branch is needed, and the split part decides how the destination set should be partitioned. When only one destination is left in the destination set, we use either wait (no further relay) or focus (with further relay) to reach the final destination. The effectiveness of our approach is verified through extensive simulations. Ratio-based-split performs best in the compare–split step, both in synthetic and real traces. Using the wait scheme can reduce the number of forwardings, while using the focus scheme can reduce the latency.

Delegation Forwarding in Delay Tolerant Networks Multicasting (Invited Paper)

Delay tolerant networks (DTNs) are a special type of wireless mobile networks which may lack continuous network connectivity. Multicast supports the distribution of data to a group of users, a service needed for many potential DTNs applications. While multicasting in the Internet and mobile ad hoc networks has been studied extensively, due to the unique characteristic of frequent partitioning in DTNs, multicasting in DTNs is a considerably different and challenging problem. It not only requires new destinations of multicast semantics, but also brings new issues to the design of routing algorithms. In this paper, we propose new forwarding models for DTNs multicast and develop several multicast forwarding algorithms. We use delegation forwarding (DF) in DTNs multicast and compare it with single and multiple copy multicast models, which are also proposed in this paper. From the analytical results, we have the following conclusions: (1) Although the single copy model has the smallest number of forwardings, its latency is much longer than the other two models. (2) Among these three models, the delegation forwarding model has the least delay. The effectiveness of our approach is verified through extensive simulation both in synthetic and real traces.