Transient community detection and its application to data forwarding 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.

Social analysis and community structure detection present a new angle of view in the design of data routing and dissemination in delay tolerant networks (DTNs). However, most community detection schemes developed in the context of sociology cannot be applied to DTNs since they have been designed without the consideration of the dynamic aspect of DTNs where the network topology changes and evolves over times. In this paper, we propose a new community detection algorithm which runs in a distributed and real-time manner and thus can be used in time-varying networks like DTNs. From the performance study, we show that our algorithm well adapts to dynamically changing networks.

While portable and wireless devices are pouring, a new network technology is needed as a breakthrough. The new network technology features large delays, intermittent connectivity, and absence of an end-to-end path from sources to destinations. A network which has one of those characteristics is called DTNs(Delay Tolerant Networks). The main 4 routing methods have been researched so far in extreme environment. In this paper, we look into the reliability of DTMNs(Delay Tolerant Mobile Networks) in several different situations, and propose an algorithm that selects a positive routine by sending the only information of its position when making a connection to a detected node. We simulate the proposed algorithm here in DTN using ONE simulator. As a result, it shows that the algorithm reduces the number of message transmission each node.

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

Disruption tolerant networks (DTNs) are a class of networks in which no contemporaneous path may exist between the source and destination at a given time. In such a network, routing takes place with the help of relay nodes and in a store-and-forward fashion. If the nodes in a DTN are controlled by rational entities, such as people or organizations, the nodes can be expected to behave selfishly and attempt to maximize their utilities and conserve their resources. Since routing is an inherently cooperative activity, system operation will be critically impaired unless cooperation is somehow incentivized. The lack of end-to-end paths, high variation in network conditions, and long feedback delay in DTNs imply that existing solutions for mobile ad-hoc networks do not apply to DTNs. In this paper, we propose the use of pair-wise tit-for-tat (TFT) as a simple, robust and practical incentive mechanism for DTNs. Existing TFT mechanisms often face bootstrapping problems or suffer from exploitation. We propose a TFT mechanism that incorporates generosity and contrition to address these issues. We then develop an incentive-aware routing protocol that allows selfish nodes to maximize their own performance while conforming to TFT constraints. For comparison, we also develop techniques to optimize the system-wide performance when all nodes are cooperative. Using both synthetic and real DTN traces, we show that without an incentive mechanism, the delivery ratio among selfish nodes can be as low as 20% as what is achieved under full cooperation; in contrast, with TFT as a basis of cooperation among selfish nodes, the delivery ratio increases to 60% or higher as under full cooperation. We also address the practical challenges involved in implementing the TFT mechanism. To our knowledge, this is the first practical incentive-aware routing scheme for DTNs.

Delay Tolerant Mobile Networks (DTMNs) provide communication despite the occasional presence of disconnected subnetworks. They rely on finding a set of sequential opportunistic encounters between pairs of mobile nodes. In this context, understanding mobile node behaviour is essential to design effective and efficient network protocols. Previous studies aimed to predict future encounters where predictions depend on exploring the probability/age of encounters and integrated interactions in the mobile data. However, those previous solutions suffer from unstable predicted encounters with lack of routing information such as encounter times. As an alternative to prediction, we propose to exploit periodicity within mobile data to find stable (periodic) encounters for routing in DTMNs. In this thesis, we first present a generic methodology to model and find periodic encounter patterns by using the auto-persistence function and detection techniques derived from it. Secondly, we propose a novel graph model to capture periodic encounter patterns where routing problems can be modelled and solved as optimization problems. Lastly, to connect disconnected subnetworks that are strongly connected inside, e.g., by periodic encounters, in the networks we introduce stationary relay nodes whose deployment is modelled as various k-connectivity problems. Taking advantage of our studies, the experimental results demonstrate that in the environment of DTMNs with the presence of disconnected sub-networks, message delivery can benefit greatly from the underlying periodicity within mobile data. In addition, exploiting periodicity opens up new research frontiers in several aspects such as designing novel routing protocols, query dissemination and collection, and preserving privacy and security in environments with the presence of periodic behaviours.

Performance evaluation of DTN protocols to deliver sms in dense mobile network : Empirical proofs

The routing efficiency in delay tolerant networks is degraded due to intermittent connection and high latency. Additionally, socially selfish nodes in social networks refuse to provide message forwarding service since there are limited resources. To solve these problems, an improved routing algorithm based on the social link awareness is proposed. In this algorithm, multiple social features of the nodes' behaviors are utilized to quantify the nodes pairs' social links. The social links of the nodes pairs are computed based on their encounter history. These social links can be used to construct the friendship communities of the nodes. The intra-community and inter-community forwarding mechanisms are implemented to raise the successful delivery ratio with low overhead and decrease the transmission delay. Simulation results show that the proposed algorithm shortens the routing delay and increases the successful delivery ratio, thereby improving the routing efficiency.

only intermittent connectivity between communication sources and destinations. In order to provide successful communication services for these challenged networks, a variety of relaying and routing algorithms have been proposed with the assumption that nodes are homogeneous in terms of contact rates and delivery costs. However, various applications of DTN have shown that mobile nodes should be divided into different classes in terms of their energy requirements and communication ability, and real application data have revealed the heterogeneous contact rates between node pairs. In this paper, we design an optimal relaying scheme for DTNs, which takes into account nodes ’ heterogeneous contact rates and delivery costs when selecting relays to minimise the delivery cost while satisfying the required message delivery probability. Extensive results based on real traces demonstrate that our relaying scheme requires the least delivery cost and achieves the largest maximum delivery probability, compared with the schemes that neglect nodes ’ heterogeneity. I.

DTN (Delay Tolerant Network) is a new type of mobile Ad Hoc network. Due to its characteristics such as long communication delay, high dynamic topology, it is difficult to maintain the stability of end to end paths. Therefore, design of effective and reliable routing algorithms has become the key issue in DTN. To avoid random and blindfold forwarding in Spray and Wait routing, a DTN routing algorithm named R-ASW (Relay-probability-based Adaptive Spay and Wait) has been proposed, R-ASW uses the performance of receiver nodes to determine whether forward message to the encounter node and calculate the number of message copies to be forwarded. This algorithm thought over synthetically the factors of node's energy, delivery predictability and speed. NS2 network simulation software is used to analyze the validity and reliability of the proposed DTN routing algorithm. The simulation results show that the proposed algorithm has better performances and it is suitable for DTN.

Continuous network connectivity has always been a significant issue in the area of networks. Delay Tolerant Networks(DTNs) provides an architecture that casts upon the problems of discontinuity in the network and tries to solve it. Such dropping of connectivity is found in tremendous terrestrial atmosphere and planetary systems. Instead of traditional communication system of delivering data from source to destination through continuous connectivity, DTNs uses the intermediate nodes to relay messages from source to destination. Sometimes these nodes act selfishly and can deny to relay packets for saving their resources like energy, buffer etc and that is why they may not agree to forward data packets which leads to lack of cooperation and hence hampers transferability in the network. To combat this selfish behavior various incentives or rewards have been proposed to these nodes such they assist with each other and make the network communication smoother. Packet replication control based prophet routing strategy for DTNs (PRCP) uses replication control based incentive mechanism in prophet routing algorithm which has shown better values of parameters compared to existing ones.

Networks that lack continuous connectivity among their nodes due to node mobility, limited data storage space and constrained power sources are called Delay Tolerant Networks (DTNs). DTN nodes store and carry the data packets until they come into the communication range of each other. In recent years several protocols have been developed specifically for routing in DTNs. These protocols vary in number of copies they use and the kind and amount of knowledge they use to guide the packets to their destinations. Remaining energy level, average latency, overhead ratio and delivery ratio are some of the performance metrics used to measure the performance of these protocols. The existing protocols are good in some of these metrics but not all of them. There is always a trade-off between different performance metrics. In this paper we have proposed a Hybrid protocol utilizing advantages of two protocols namely Epidemic and Probabilistic Routing. The performance is discussed and compared of these protocols with our Hybrid strategy in Opportunistic Network Environment tool.

Multi-copy replication is an efficient approach for routing a message between a pair of source and destination nodes in a Delay Tolerant Network (DTN). However, such an approach disseminates an undesirable number of replicas of messages, which increases the overhead of the network. To restrain this, disparate routing techniques have evolved that limit the number of copies of the messages. However, in these schemes a message stays undesirably long in the buffer of a node. To address this issue, we propose a contact-based routing algorithm for DTNs that minimizes the average message buffer time of a node, while maintaining a targeted message delivery ratio compared to the existing state-of-the-art routing protocols. Simulation results show that the average message buffer time reduces upto one fourth from the existing quota-based schemes, and the message delivery ratio improves upto 18% over the well-known flooding based schemes.

Automated key exchange protocol evaluation in delay tolerant networks

In delay tolerant networks (DTNs), all the networking functions rely on the contribution of the participants to fulfill the store-and-forward fashion. Since wireless nodes are buffer and energy constrained, it may not be in the best interest of a node to always accept relay request. In recent years, incentive mechanisms have been proposed to stimulate nodes to cooperate in packet forwarding. However, the lack of end-to-end paths, high variation and long feedback delay in DTNs imply that existing solutions for mobile ad-hoc networks do not apply to DTNs. In this paper, we address the problem assuming that nodes are rational to optimize self interest. We propose a model, named Pay-for-Gain (PFG), based on game theory and loan-credit theory, to investigate equilibrium point that maximizes their own interest. For comparison, the strategy tit-for-tat (TFT) and PFG are tested in existing routing protocols in DTNs.