Maximizing transfer opportunities in bluetooth DTNs

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.

There is a lack of reliable tools for evaluating the performance of Delay Tolerant Networks (DTN). Frequently, the researchers use small-scale real networks or one of the few available DTN simulators. This work presents an alternative approach for conducting performance evaluation studies of DTN, following a recent movement of the scientific community with respect to the use of hybrid environments in order to achieve realism in the studies. We propose, implement and validate the Virtualized DTN Testbed (VDT) as a means to construct a virtualized testbed completely in software that takes into account a real instance of the operating system and applications that run inside the mobile nodes, as well as a robust model of the wireless channel. The results show that VDT can accurately reproduce both the mobility of nodes, and the contact opportunities obtained in experiments of a real testbed. Moreover, we identified some implementation problems in the real experiments, that after some fixing strategies allowed us to identify the occurrence of several contacts not registered previously.

ExMin: A routing metric for novel opportunity gain in Delay Tolerant Networks

We consider a Delay Tolerant Network (DTN) whose users (nodes) are connected by an underlying Mobile Ad hoc Network (MANET) substrate. Users can declaratively express high-level policy constraints on how "content" should be routed. For example, content may be diverted through an intermediary DTN node for the purposes of preprocessing, authentication, etc. To support such capability, we implement Predicate Routing [7] where high-level constraints of DTN nodes are mapped into low-level routing predicates at the MANET level. Our testbed uses a Linux system architecture and leverages User Mode Linux [2] to emulate every node running a DTN Reference Implementation code [5]. In our initial prototype, we use the On Demand Distance Vector (AODV) MANET routing protocol. We use the network simulator ns-2 (ns-emulation version) to simulate the mobility and wireless connectivity of both DTN and MANET nodes. We show preliminary throughput results showing the efficient and correct operation of propagating routing predicates, and as a side effect, the performance benefit of content re-routing that dynamically (on-demand) breaks the underlying end-to-end TCP connection into shorter-length TCP connections.

SummaryIn Delay Tolerant Networks (DTNs), mobile nodes exploit encounter chances to transmit data via the established opportunistic link between encounter nodes. The transmission capacity between two encounter nodes is constrained by the duration of opportunistic links. How to transmit data efficiently is one of the fundamental and most important issues in DTNs. Recently, Random Linear Network Coding (RLNC) is proposed as a promising approach to improve data transmission efficiency in DTNs. To facilitate the development of deployment of RLNC based routing protocols, it is imperative to quantify the performance gain brought by RLNC in a rigorous and systematic way. In this paper, we develop an analytical model to evaluate the data transmission performance of RLNC based epidemic routing in DTNs. In the model, we consider that multiple unicast communication sessions compete for limited \capacity. Numerical results validate the effectiveness of our analytical model and demonstrate the significant performance improvement for data transmission in DTNs brought by RLNC. Our work of this paper provides a general tool for performance evaluation and useful guidelines for designing RLNC based routing protocols in DTNs. Copyright © 2015 John Wiley & Sons, Ltd.

Delay Tolerant Network (DTN) is a network architecture to provide a solution for networks which have intermittent connectivity, long delay, a different data rate and high error rate. DTN is used as an alternative solution for communication networks in remote areas. DTN communications model based on the nodes mobility to transmit data between nodes which geographically separated so if disconnection problem happens when data transfer is running, bundle which already has been sent will remain stored in the last node where the data reached, and then when connection reconnects, the data transfer process can be continued without repeating the process from the beginning until the data reaches the destination node. This paper analyzes the custody transfer on moving bundle protocol of wireless router in a DTN. The analysis uses a delivery data scenario that implements a wireless router moving on a DTN Network by showing custody transfer bundle protocol and takes into account the time of transfer in any data from DTN log. The scenario considers two conditions, namely the LoS (Line of Sight) and n-LoS (near Line of Sight) with distance and data variation. Experimental results show the important role of the custody transfer agent in DTN network.

We consider a delay-tolerant network (DTN) whose mobile nodes are assigned to collect packets from data sources and deliver them to a sink (i.e., a gateway). Each mobile node operates by using energy transferred wirelessly from the gateway. For such a network, two main issues are studied. First, when a mobile node is at the data source, this node must decide on whether to accept the packet received from the data source or not. In contrast, whenever a mobile node is at the gateway, it has to decide on whether to transmit the packets collected from the data sources or to request wireless energy transfer. Second, multiple mobile nodes can cooperate and form coalitions to help one another in the delivery of packets from their associated data sources. However, this cooperation may not be always beneficial due to the limited buffer and energy resources. Moreover, some mobile nodes may secretly decide to deviate from a given coalition, thus taking advantage of the other innocent mobile nodes. To address these two issues, this paper introduces a performance analysis and optimization framework, which is based on a joint optimization and game-theoretic framework. The optimization model is used to obtain the packet delivery policy of each individual mobile node. Then, a novel game-theoretic model, namely a repeated coalition formation game , is developed to analyze the cooperation strategies of multiple mobile nodes.

Nowadays, Delay Tolerant Network plays an important role in improving the communication between the network nodes. Applications of Delay Tolerant Network are disaster recovery, vehicular communication, sensor networks, interplanetary networks, and communication in remote and rural areas. Routing is one of the important tasks for enhancing the energy effectiveness of data transmission among the mobile nodes under network congestion and dynamic topology. Machine Learning-based routing algorithms are used for improving network communication in Delay Tolerant Networks. Its objective is to reduce the delay, minimize the overhead, reduce energy consumption, improve throughput, minimize packet loss, and efficient data transmission. This paper presents a comprehensive review of routing algorithms using machine learning for Delay Tolerant Networks.

The Internet of Things (IoT) is going to develop integrated and organised networks of all things and beings in the world enabling autonomous computing and information communication for the creation of new values in the future. For such networks by IoT that accept a certain level of communication delay, but that must realise highly-reliable message forwarding, Delay Tolerant Network (DTN) gives a possible solution. Recently, DTN has attracted attention as a future network under challenged network environments where communication delay, disruption, and disconnect frequently occurs. In this chapter, we review some routing protocols for efficient message forwarding in DTN. We also review some mobility models often used for simulating motions of mobile nodes to evaluate the performance of DTN. In this review, we propose our mobility model called Homesick Levy Walk that mimics human mobility patterns of an universal scale-free property of the frequency of human contacts. After this, we also propose our utility-based routing protocol which maximises the expected number of selected relay nodes being likely to encounter a destination node under sequential encounters with nodes. We evaluate the performance of our routing protocol by comparing with some performance measures of some existing routing protocols under the condition that the Homesick Levy Walk is adopted as mobility model. We show that our protocol is comparable to others in arrival rate of messages under a smaller number of message forwarding.We also find that the performance of our protocol is stable up to a few hundred mobile nodes and tends to be scalable with the number of nodes.

With the development of mobile Internet, wireless communication via mobile devices has become a hot research topic, which is typically in the form of Delay Tolerant Networks (DTNs). One critical issue in the development of DTNs is routing. Although there is a lot research work addressing routing issues in DTNs, they cannot produce an advanced solution to the comprehensive challenges since only one or two aspects (nodes' movements, clustering, centricity and so on) are considered when the routing problem is handled. In view of these defects in the existing works, we propose a novel solution to address the routing issue in social DTNs. By this solution, mobile nodes are divided into different clusters. The scheme, Spray and Wait, is used for the intra-cluster communication while a new forwarding mechanism is designed for the inter-cluster version. In our solution, the characteristics of nodes and the relation between nodes are fully considered. The simulation results show that our proposed scheme can significantly improve the performance of the routing scheme in social DTNs.

The broadcast diffusion of messages in Delay Tolerant Networks (DTNs) is heavily dependent on nodes mobility, since protocols must rely on contact opportunities among devices to diffuse data. This work is a first effort to study how the dynamics of nodes affect both the effectiveness of the broadcast protocols in diffusing data, and their efficiency in using the network resources. The paper describes three control mechanisms. The mechanisms characterize a family of protocols able to achieve some awareness about the surrounding environment, and to use this knowledge in order to keep the broadcast overhead low, while ensuring high node coverage. Simulation results identify the winning mechanisms to diffuse messages in DTNs under different conditions.

This paper presents a secured communication between mobile nodes in military environments such as a battlefield or a hostile region which are likely to suffer from connectivity issues in an infrastructure less environment. Disruption-tolerant network (DTN) technology is an upcoming successful solution that offers the wireless devices carried by soldiers to communicate with each other and access the confidential information or command reliably by exploiting external storage nodes. DTNs introduce several security and privacy challenges with regard to the attribute revocation, key escrow, and coordination of attributes issued from different authorities. This paper proposes a reliable route selection on the basis of Misbehavior Detection Algorithm and the source encrypts the data using Attribute Specified Identity Based Encryption Algorithm. The DTN is used to authorize the nodes and DTN registers the node details to Trust Authority. The Trust Authority generates Secret Key and the route to transfer packet to destination. The secret key is also automatically changed when the node joins a network and leaves a network based on Fast Randomized Algorithm by which the level of security is increased.

Delay-tolerant networks consist of mobile nodes that communicate in unscheduled opportunity without network infrastructure support. When mobile nodes move in highly dynamic networks, they suffer from many challenging issues such as broken network topology and transient connectivity among nodes. In this paper, we propose a geo-routing scheme with an angle-based decision policy (GRAD) for message delivery in delay-tolerant networks. This scheme can select relay nodes in geographic proximity to perform message delivery towards a destination. After a definite number of relays, the message can be destined to a destination. Simulation results show that GRAD can attain a higher rate of successful message delivery and lower communication cost as compared with a classical Spray and Wait scheme under area-confined random waypoint and SLAW mobility patterns in delay-tolerant networks.

Networks in which nodes are sparsely distributed and, therefore, are disconnected for long periods of time, are termed Delay Tolerant networks (DTN). The intermittent connection, together, with the limited resources of mobile nodes, mainly power and memory, created a challenging environment for data networking in DTN. Routing protocols developed for DTN tend to discover and select the minimum end-to-end delay paths to destinations assuming that these paths provide the highest delivery rate. To achieve this goal, they spread many copies of the same packet, ignoring the limitedness of storage space and power sources. In this paper, we study this problem by building a mathematical model for optimal routing in DTN. We compare the results of implementing three objectives for this model: minimizing the end-to-end delay, minimizing the end-to-end number of hops, and maximizing the delivered messages. We study and analyze the impact of varying the buffer space, the traffic load and the packets time-to-live (TTL) on the three objectives. Results show that minimizing the number of hops provides higher delivery ratio than minimizing the delay, which contradicts the previous assumption. In addition, minimizing the number of hops significantly reduces the number of transmissions which results in saving energy.

Delay tolerant networks (DTNs) are wireless networks where disconnections may occur frequently due to node mobility, power outages and propagation phenomena. To achieve date delivery, store-and-forward protocols are used in DTN and routing protocols based on epidemic message dissemination have been proposed, like epidemic routing. Under epidemic routing, messages can be delivered completely between every two nodes if every node buffer is big enough and the communication time is long enough after one node contacts another. But congestion will occur easily at a node if the buffer of this node is limited under epidemic routing in DTN. To solve this problem, a novel congestion control strategy is introduced. The strategy is called N-DC (drop the copying numbers over N). By using simulations based on a Random Waypoint model, the simulation results proved the improvement of this strategy.