An Improved Routing Algorithm Based on Social Link Awareness in Delay Tolerant Networks

Delay Tolerant Network (DTN) is a sparse and intermittently connected mobile wireless network where reliable communication and end-to-end connectivity cannot be assured. In DTN, a node delivers messages to the destination using store and forward scheme. Messages are copied and transferred to multiple relay-nodes in order to increase the opportunity for that message to reach the intended destination. Contact is the time duration for which two or more mobile nodes encounter each other within their radio transmission ranges, and are able to transfer messages. Due to arbitrary node movement, contact time will be varied, and is unlikely to be predictable. In this paper, we propose a fuzzy decision mechanism we called “fuzzy-spray”, to improve the routing and packet transfer efficiency in DTN environment. Fuzzy-spray can reduce overall latency in DTN by intelligently selecting appropriate messages to send to the relay-node during its next contact time. It uses fuzzy logic to prioritize messages that are stored in the buffer, based only on local parameters from each message, namely forward transmission count and message size. There is no need to know a priori information about network such as node mobility model, or node-distribution across the deployed area. The simulation results show that fuzzy-spray has the best performance in terms of overall speed of delivery, and lowest average message delay compared with other existing algorithms.

Generic prediction assisted single-copy routing in underwater delay tolerant sensor networks

Delay tolerant network (DTN) known as suffering from frequent disruption, high latency and heterogeneous, re­sulting in low network availability. To improve DTN availability, routing protocols typically need to predict the probability of encountering the nodes. In this paper, we use the Bayesian Network (BN) to construct the knowledge base, which is an unique tool for creating a representation of the dependence relationships among DTN parameters. Then developed a Bayesian network- based approach to estimate the contact probability among nodes of DTN. We conducted an experiment to compare our approach against its counterparts in PROPHET routing protocol and power law distribution-based method. The experiment shows our approach is superior to other methods in both recall ratio and precision in all four datasets, including HAGGLE, NUS, REALITY and SASSY.

In recent years, several investigations have been made on "challenged network" [also known as, delay tolerant network (DTN)] architectures highlighting their advantages and disadvantages. In spite of its inherent shortcomings of unreliability and delay, smart-phone based opportunistic network is gaining immense popularity in the research community due to its applicability in different adverse and extreme communication scenarios where traditional communication infrastructure is either unavailable or incapacitated for a long time. Considerable research has been conducted till date to design efficient network architecture for emergency data dissemination in intermittently connected/challenged networks. Different architectures (ranging from flat to multi-tier) are proposed for implementing opportunistic DTN keeping in view of specific application requirements. However, very few of these proposed architectures have been examined from the perspective of a post disaster communication. Moreover, most DTN architectures are designed by aiming towards increasing delivery probability and reducing latency and as a whole, maximizing network throughput; with very little emphasis on its energy efficiency. The impact of different mobility patterns on existing DTN routing algorithms with respect to data dissemination and energy consumption has also not been studied so far. Our objective, in this paper, is to investigate the impact of different mobility patterns on existing DTN routing protocols and existing DTN architectures and subsequently, come up with a suitable energy efficient DTN framework combining suitable architecture and routing protocol that may be used to offer different disaster management services during post-disaster relief operation. We have done an extensive simulation on ONE simulator with different categories of well-known existing DTN architectures, mobility models, DTN routing protocols to study the network performance in terms of delivery probability, energy efficiency and overhead ratio. Based on the simulation results, we have tried to figure out a suitable combination of energy efficient architecture, mobility model and routing protocol that fits well in the post disaster communication scenario.

Currently, the research community in communication networks has given special attention to the study of emerging wireless networks such as sensor networks, mesh networks, ad hoc networks, pervasive computing systems and delay/ disruption tolerant networks (DTNs). The main feature of these networks is not require the presence of a communication infrastructure and, therefore, often present decentralized operation and auto configuration. Additionally, due to the DTN s highly distributed nature, it is desirable that it be also assigned to this type of network some level of awareness of energy consumption. Thus, in this Thesis, we propose an optimization strategy for a routing algorithm that was originally proposed without regard to the issue of energy constraint in delay/disruption tolerant networks (DTNs). The routing algorithm must use some utility function based on a number of different parameters (e.g., encounter history, mobility, sociability, etc.) to discover the better relay nodes. Our proposed strategy is based on modeling of the message forwarding as Bayesian game that aims specifically to capture the dynamic nature of the message replication decisions, the energy constraint of the devices and the uncertainty about the energy of other devices. An adaptive learning framework that allows the nodes to learn the optimal strategies over time is presented. We use a system for belief update about the energy of the other DTN nodes based on the accumulated observations of the destination nodes. Simulation results show that our proposed optimization strategy is able to lead the network to remain operational for a longer period of time and, consequently, to achieve a higher final delivery ratio.

The Delay Tolerant Networks (DTNs), are emerging as one of the most efficient network that allow nodes in intermittently connected networks to communicate with each other. They are designed to overcome high latency and lack in connectivity due to poor infrastructure and short range radios. However, the DTNs relay nodes have limited resources (i.e., low-power RF module, low computation capacity, limited buffer size, short battery power). Moreover, the DTNs routing protocols, which route the message between a source and a target destination, are very numerous, including the famous Epidemic routing, k-hop routing, prophet routing. Consequently, We found that it would be valuable to compare these prominent opportunistic networks protocols under constraint of energy consumption in forwarding activity. We have done this using the ONE simulator and evaluated the schemes with regard to message delivery probability, energy efficiency.

Delay tolerant network (DTN) is an approach that allows the transmission of data in a difficult situation where refined infrastructure are unavailable and the end-to-end path does not exist at the moment of transmission of data. The DTN efficiently improves network communications where the network connectivity is irregular or prone to disruptions. The Bundle Protocol of DTN use Store and Forward approach that facilitates the flow of information. For constructive network communication DTN is being used. The inspection course addresses DTN architecture, bundle protocol, routing protocols, challenges in routing, application, and advantages.

Delay Tolerant Network (DTN) shows some features like link frequent interruptions, long delays, limited resources and so on, while nodes fight each other to win the network resources in the process of communication, which can lead to network congestion in delay tolerant network. Therefore, congestion control is a key issue in delay tolerant network research. The present congestion control strategies are divided into congestion detection, congestion avoidance, congestion handling. In this paper, we qualitatively analyze and compare typical congestion control strategies have been proposed, which are based on the analysis of the basic characteristics of the delay tolerant network. Through the analysis of the advantages and disadvantages of each mechanism, we conducted further research and discovery. Finally, we make a conclusion and propose congestion control technology and the energy constraint balance strategy.

The High-Rate Delay Tolerant Networking (HDTN) project has taken a distributed service-based approach to the development of a highly efficient delay tolerant networking (DTN) implementation. Through the analysis of many DTN implementations, system and mission requirements as well as the DTN protocol specifications, HDTN has worked to infuse modern computing technologies into the NASA approach to interplanetary networking.The initial use case of the HDTN software runs on a hypervisor representative of the International Space Station (ISS) DTN Gateway. In this scenario, multiple emulated payloads will send science data through HDTN to a mission operations center. HDTN will provide store and forward capability as well as network flow management.This paper discusses the infusion path of cognitive networking technologies in the NASA Space Communications and Navigation (SCaN) networks using the DTN architecture and protocols as the basis for cognitive routing and network management capabilities. HDTN has been developing the Bundle Protocol encoding and decoding mechanisms and messaging framework that can be used as the basis for integrating DTN with various learning and decision-making processes. The concepts of distributed computing, network virtualization, software defined networking and delay tolerant networking are basic building blocks which will further the development of cognitive networking. In addition to discussion of the HDTN software development and testing, this paper examines the role that each of these technologies play in the evolution of the current state of space networking into an intelligent network of networks.

Delay tolerant networks (DTNs) are wireless networks in which an end-to-end path for a given node pair can never exist for an extended period. It has been reported as a viable approach in launching multiple message replicas in order to increase message delivery ratio and reduce message delivery delay. This advantage, nonetheless, is at the expense of taking more buffer space at each node. The combination of custody and replication entails high buffer and bandwidth overhead. This paper investigates a new buffer management architecture for epidemic routing in DTNs, which helps each node to make a decision on which message should be forwarded or dropped. The proposed buffer management architecture is characterized by a suite of novel functional modules, including Summary Vector Exchange Module (SVEM), Networks State Estimation Module (NSEM), and Utility Calculation Module (UCM). Extensive simulation results show that the proposed buffer management architecture can achieve superb performance against its counterparts in terms of delivery ratio and delivery delay.KeywordsRoutingBuffer management

Anycast routing is very useful for many applications such as resource discovery in delay tolerant networks (DTNs). In this paper, based on a new DTN model, we first analyze the any-cast semantics for DTNs. Then we present a novel metric named EMDDA (expected multi-destination delay for anycast) and a corresponding routing algorithm for anycast routing in DTNs. Extensive simulation results show that the proposed EMDDA routing scheme can effectively improve the efficiency of anycast routing in DTNs. It outperforms another algorithm, minimum expected delay (MED) algorithm, by 11.3% on average in term of routing delays and by 19.2% in term of average max queue length.

With the development of mobile internet, wireless communications via mobile devices in the form of Delay Tolerant Networks (DTNs), becomes a hot research topic. One critical issue in the DTNs with social characteristics is that there could exist selfish nodes which are unwilling to forward messages from strangers and malicious nodes which intentionally impair normal communication. Although there are a lot research works addressing various issues in the DTNs, most current research works only take communication behavior into account. In view of these defects in the existing works, we propose a novel solution to address the selfish and security issues in the social DTNs. A dynamic trust model is proposed to prevent bad-mouthing and ballot stuffing attacks and the Shannon entropy function is introduced to avoid blackhole and greyhole attacks. The simulation results show that our proposed scheme can significantly improve the performance of the social DTNs.

Delay Tolerant Network (DTN) is a kind of networks that have no fixed path between nodes due to lack of continuous network connectivity. To achieve successful communication and to improve performance in DTN is always a challenge work. Most existing works are based on designing high efficient routing protocols and have not emphasized the MAC layer as well as new technologies available in the Physical layer which may influence the performance for whole networks. In this paper, we consider utilization of Multi-packet Reception (MPR) capability in DTN in order to provide better performance. We introduce our own MPR scheduling scheme, Group Based Scheme (GBS), and compare the performance of DTN with different MPR capabilities. Our works have been evaluated by the simulation using a real vehicular network trace composed of the GPS data of more than 4,000 taxis in Shanghai urban area. The results have demonstrated various impacts of using Multi-Packet Reception (MPR) on performance in DTN. By using MPR in DTN, it outperforms the network without MPR especially when the wireless transmission range increases.

In current routing algorithms based on encounter history in Delay-Tolerant Networks (DTNs), packets are always forwarded to nodes with highest probability to reach destination node. However, to the best of our knowledge, no analytical node transient contact pattern detection to achieve high performance, is reported in the literature. In this letter, DTN-Knca - a novel routing which detects frequently encountered nodes' transient contact patterns by correlation analysis is proposed. The trace-driven simulations demonstrate the higher throughput of DTN-Knca in comparison to the state-of-the-art DTN typical routing algorithms based on the encounter history knowledge.

Delay Tolerant Networks (DTN) present many challenges that are not present in traditional networks.Many stem from the need to deal with disconnections which directly impacts routing and forwarding.However as these networks enable communication between wide range of devices, there are secondary problems that routing strategies may need to take care of such as to deal with limited resources like buffer, bandwidth, power.Most of the routing protocols in DTN assume that the buffer size as infinite which is not the case in reality.In resource constrained environment, buffers will run out of capacity at certain point of time.Moreover due to mobility of the nodes and limited bandwidth, it is not possible to transmit all messages a node has during the short available period of contact.Consequently an efficient buffer management policy is required under resource constrained DTNs.Further, DTNs can be used to support several asynchronous applications simultaneously.Each application may have different priority.For example, an emergency alert in monitoring application is more important than the regular data.Such environment stimulates the need to introduce priority to messages.Therefore in this paper, a policy is proposed which performs buffer management with prioritization.The proposed approach with epidemic routing is evaluated through simulation and compared with other policies.It is shown that the proposed approach results in performance improvement to epidemic routing with preferential delivery.