A Checkpoint Based Message Forwarding Approach For Opportunistic Communication

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.

Majority of the existing Delay Tolerant Network (DTN) routing protocols, attempt to minimize one of the popular DTN routing indices, i.e. message delay, forwarding count and storage. However, for many DTN applications such as distributing commercial content, targeting the best performance for one index and compromising the others is insufficient. A more practical solution would be to strike a balance between multiple of these indices. Gain Dissemination Protocol (GDP) is one of the protocols which targets this aim by introducing a gain concept which tries reach a maximum gain of delivery by keeping the balance between the value achieved via delivering the packet to the destination and the forwarding cost involved with that. In this paper, we focus on characterizing the GDP protocol in the scope of mobility. We also propose an upper bound for gain in multicast routing problem, i.e. the Union of Unicast Benchmark (UUB) and compare the performance of a few DTN routing protocols with the former. This eventually reveals the performance scope of a potential gain-aware DTN dissemination protocol.

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.

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.

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.

A social-aware routing protocol for opportunistic networks

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.

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

Delay-Tolerant Networks (DTN) are intermittent wireless mobile networks designed to handle communications in environments where network connectivity is often disrupted due to node mobility or the absence of fixed infrastructures.These frequent disconnections lead to repeated communication attempts between nodes, thereby increasing energy consumption.DTN is often deployed in isolated and hard-to-reach environments with limited energy sources, imposing significant constraints on the performance and operational lifetime of individual DTN nodes, as well as the DTN network as a whole.Despite the significant efforts invested by researchers to develop energy-efficient algorithms and models, the problem of energy consumption persists, especially with nonrenewable sources.The motivation for this research is based on the major challenges related to powering mobile nodes in DTN networks, notably due to the absence of reliable and constant energy sources.The energy constraints of the nodes, combined with their mobility, raise problems of energy consumption and durability, leading to communication interruptions, delays, data losses, and a decrease in the overall efficiency of the network.To overcome these challenges, the article proposes a long-term energy management strategy by integrating renewable energy sources, notably solar energy, into the architecture of DTN nodes.The contributions include the modeling of an energyautonomous and sustainable solar-powered DTN node, the evaluation of the energy generated and stored by these nodes, and the validation of the effectiveness of this approach through simulations in the ONE simulator, considering realistic mobility scenarios and communication conditions.The results show that solar DTN nodes have significantly higher residual energy than those with limited power sources.Additionally, social mobility models (MBM, SPMBM) consume more energy than individual models (RW, RWP, RD), while the Spray-and-Wait and PROPHET protocols are more energy-efficient compared to Epidemic and MaxProp.These analyses reveal optimal combinations of DTN protocols and mobility models to reduce energy consumption: the Spray-and-Wait protocol aligns well with social mobility models, while PROPHET is more suited to individual mobility models.

Delay-Tolerant Networks are characterized by not having permanent end-to-end connections, often leading to intermittent connectivity, long and variable delays and high error rates. Mobile Social Networks are particular scenarios on which nodes are seen as individuals with inherent social habits, having wireless communication devices. In this paper a routing protocol based on the social property of Friendship is proposed. The protocol allows nodes to consider other nodes to be friends if they maintain contact frequently, regularly and in long-lasting sessions. The forwarding scheme consists in only delivering the message to nodes which are friends of the destination. To evaluate the performance of this protocol, the ONE Simulator was used. The Friendship Protocol performance was analyzed and compared to three other routing protocols while varying the network load. The simulation results showed that the Friendship Protocol could reach a high delivery rate and a very low overhead. A dynamic threshold version of the protocol was also proposed, on which the friendship threshold changes over time as it corresponds to a portion of the best friends. The results of this dynamic version were similar to the fixed threshold version, but with roughly half the overhead.

The underwater acoustic channel features long and variable propagation delay, high bit error rate and limited bandwidth. Moreover, underwater mobile networks consisting of Autonomous Underwater Vehicles (AUVs) for surveillance and monitoring applications often suffer from intermittent connectivity as nodes move around the area of operations. Therefore, this scenario is appropriately modeled as a Delay-Tolerant Network (DTN). In this paper, we investigate two classes of DTN routing protocols: Spray-and-Wait (SNW) and the Resource Allocation Protocol for Intentional DTN (RAPID), together with a standard flooding protocol for underwater mobile networks, and their performance is analyzed in terms of packet delivery ratio, average end-to-end delivery delay and throughput, in different load conditions across various node mobility scenarios. Our results show that RAPID performs better than other DTN routing protocols in terms of packet delivery ratio at higher load conditions irrespective of node mobility, whereas the Binary version of SNW has the best performance in terms of average delivery delay.

Hybrid delay tolerant network routing protocol for heterogeneous 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.

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.

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