Delay Tolerant Mobile Networks Research Articles

L-VTP: Long-Term Vessel Trajectory Prediction Based on Multi-Source Data Analysis.

With the rapid development of marine IoT (Internet of Things), ocean MDTN (Mobile Delay Tolerant Network) has become a research hot spot. Long-term trajectory prediction is a key issue in MDTN. There are no long-term fine-grained trajectory prediction methods proposed for ocean vessels because a vessel’s mobility pattern lacks map topology support and can be easily influenced by the fish moratorium, sunshine duration, etc. A traditional on-land trajectory prediction algorithm cannot be directly utilized in this field because trajectory characteristics of ocean vessels are far different from that on land. To address the problem above, we propose a novel long-term trajectory prediction algorithm for ocean vessels, called L-VTP, by utilizing multiple sailing related parameters and K-order multivariate Markov Chain. L-VTP utilizes multiple sailing related parameters to build multiple state-transition matrices for trajectory prediction based on quantitative uncertainty analysis of trajectories. Trajectories’ sparsity of ocean vessels results in a critical state missing problem of a high-order state-transition matrix. L-VTP automatically traverses other matrices in a specific sequence in terms of quantitative uncertainty results to overcome this problem. Furthermore, the different mobility models of the same vessel during the day and the night are also exploited to improve the prediction accuracy. Privacy issues have been taken into consideration in this paper. A quantitative model considering Markov order, training metadata and privacy leak degree is proposed to help the participant make the trade-off based on their customized requirements. We have performed extensive experiments on two years of real-world trajectory data that include more than two thousand vessels. The experiment results demonstrate that L-VTP can realize fine-grained long-term trajectory prediction with the consideration of privacy issues. The average error of 4.5-hour fine-grained prediction is less than 500 m. In addition, the proposed method can be extended to 10-hour prediction with an average error of 2.16 km, which is also far less than the communication range of ocean vessel communication devices.

Mobile delay‐tolerant networks with energy‐harvesting and wireless energy transfer cooperation

SummaryWe consider a mobile delay‐tolerant networks (MDTNs) with energy‐harvesting capabilities. In order to determine energy management policies that will improve network capacity and packet delivery ratio and maximize the system throughput, we consider a source node that seeks to send packets to a destination node. The optimal policy for the source varies according to its system state, which allows it to guarantee a maximum delivery probability rate. Our problem is modeled by decision theory; as a start, we are interested in the MDP to model and solve such sequential decision problems. Our goal is to optimize for each node, a utility depending on a random environment and decisions made by the node. As the MDP formalism reaches its limits when it is necessary to take into account the interactions between different several nodes, we will start using the graph‐based MDP where the state and action spaces are factorizable by variables. The transition functions and rewards are then decomposed into local functions and the dependency relations between the nodes are represented by a graph. To calculate the optimal policy, we propose Mean Field Approximation (MFA) and Approximate linear‐programming (ALP) algorithms for solving GMDP problem.

OceanRoute: Vessel Mobility Data Processing and Analyzing Model Based on MapReduce

The network coverage is a big problem in ocean communication, and there is no low-cost solution in the short term. Based on the knowledge of Mobile Delay Tolerant Network (MDTN), the mobility of vessels can create the chances of end-to-end communication. The mobility pattern of vessel is one of the key metrics on ocean MDTN network. Because of the high cost, few experiments have focused on research of vessel mobility pattern for the moment. In this paper, we study the traces of more than 4000 fishing and freight vessels. Firstly, to solve the data noise and sparsity problem, we design two algorithms to filter the noise and complement the missing data based on the vessel’s turning feature. Secondly, after studying the traces of vessels, we observe that the vessel’s traces are confined by invisible boundary. Thirdly, through defining the distance between traces, we design MR-Similarity algorithm to find the mobility pattern of vessels. Finally, we realize our algorithm on cluster and evaluate the performance and accuracy. Our results can provide the guidelines on design of data routing protocols on ocean MDTN.

Android smartphones network implementation in the absence of internet

AbstractIn this paper, Mobile Delay Tolerant Network service is implemented in Android application that allows the use of smartphones for broadcasting messages to nearby smartphones without Internet. A simple experiment is carried out with simple facilities and one type of routing protocols. This is implemented with only one router and eleven smartphones.

Multicast Techniques for Hybrid RF/FSO DTNs

Increasing the contact bandwidth in delay tolerant networks (DTNs) via multicopy routing leads to a decrease in data delivery delay and an improvement in throughput. In DTNs, in which nodes have both radio frequency (RF) and free space optical (FSO) PHY layers, contact bandwidth can be increased by using the FSO PHY as the data channel and performing multicasting. As we show in this paper, due to the highly directional nature of FSO, a naive broadcast strategy where the beam divergence includes all nodes in the broadcast set, it does not always result in the minimization of data delivery delay and the maximization of delivery probability. To this end, we develop multicast strategies for hybrid RF/FSO DTNs via an emulation of static conditions in mobile DTNs in which RF is primarily used for control. We show that the optimal multicast problem in static environments is an abstraction of the minimum weighted set cover problem, which is known to be NP-hard. To save on computation time, we propose a greedy local optimum heuristic. Performance of the various multicast techniques is comprehensively evaluated in a DTN simulator, using the Epidemic routing protocol. These evaluations show that our computationally cheap solution yields results identical to optimal while not compromising the performance of the DTN.

VSTP: vessel spatio-temporal contact pattern detection based on MapReduce

Due to lack of the coverage of 3G/4G network, satellite communication which costs excessively is the main approach used in ocean to provide network service. Ocean mobile delay tolerant network (OMDTN) can provide low-cost data transmission service in the network by utilizing the contact chances of moving vessels. Spatio-temporal contact pattern is one of the key metrics to improve the efficiency of the routing algorithm in OMDTN. Some researches have been carried out on human handheld device and vehicular ad hoc networks (VANETs). However, the vessel’s trajectory data is distributed and stored disorderly, which makes traditional contact pattern detection algorithm cannot be directly applied. In this paper, we design a parallel algorithm named VSTP based on MapReduce to detect spatio-temporal contact pattern from trajectories of over 2000 vessels. Studying the vessels’ trajectories and the contact records, we observe that the vessels’ contact pattern including inter-contact time distribution and contact times distribution is in sharp contrast to the study on human handheld device and VANETs. Our results can provide the guidelines for the design of data routing protocols on OMDTN and give a new solution to overcome the difficulty of ocean network coverage.

Cedos: A Network Architecture and Programming Abstraction for Delay-Tolerant Mobile Apps

Delay-tolerant Wi-Fi offloading is known to improve overall mobile network bandwidth at low delay and low cost. Yet, in reality, we rarely find mobile apps that fully support opportunistic Wi-Fi access. This is mainly because it is still challenging to develop delay-tolerant mobile apps due to the complexity of handling network disruptions and delays. In this paper, we present Cedos, a practical delay-tolerant mobile network access architecture in which one can easily build a mobile app. Cedos consists of three components. First, it provides a familiar socket API whose semantics conforms to TCP, while the underlying protocol, $\text{D}^{2}$ TP, transparently handles network disruptions and delays in mobility. Second, Cedos allows the developers to explicitly exploit delays in mobile apps. App developers can express maximum user-specified delays in content download or use the API for real-time buffer management at opportunistic Wi-Fi usage. Third, for backward compatibility to existing TCP-based servers, Cedos provides $\text{D}^{2}$ Prox, a protocol-translation Web proxy. $\text{D}^{2}$ Prox allows intermittent connections on the mobile device side, but correctly translates Web transactions with traditional TCP servers. We demonstrate the practicality of Cedos by porting mobile Firefox and VLC video streaming client to using the API. We also implement delay/disruption-tolerant podcast client and run a field study with 50 people for eight weeks. We find that up to 92.4% of the podcast traffic is offloaded to Wi-Fi, and one can watch a streaming video in a moving train while offloading 48% of the content to Wi-Fi without a single pause.

Data or index: a trade-off in mobile delay tolerant networks

Acquiring content through mobile networks is a basic and general topic. Mobile nodes have two different ways of obtaining data. The first method is to download data quickly through 3G/4G networks, which is expensive. The second way is to get data from other nodes by means of delay tolerant networks (DTN), which are much cheaper, but are time-consuming. Throwboxes deployed in DTN act as fixed ferry nodes. The index records the historical encounter information, in order to give the mobile nodes predictive abilities regarding future encounter events. We try to compare the effectiveness when we replace some space for the data to index. We bring forward an index-based buffer space management mechanism for throwboxes, by which mobile nodes can have the chance to fetch data at a lower total cost. Preliminary simulations demonstrate that the buffer space allocation strategy is affected by some system parameters, and that replacing some space for data with an index can lower the system total cost significantly in most cases. Simulation results also show that the index-based buffer space management mechanism outperforms other mechanisms which only store data items or hold an index of static size.

Data or index: a trade-off in mobile delay tolerant networks

Data or index: a trade-off in mobile delay tolerant networks

MAP: Ef?cient Cooperation Induced Routing Scheme for a Delay Tolerant Multi-hop Mobile Network

In multi-hop network the efficiency of the transmission depends solely on the cooperation of all nodes in the network in relaying neighbouring nodes' data packets. Some nodes may be selfish, mischievous by dropping received packets or refuse to accept packet from other nodes whereas using other nodes resources to transmit their packets. This drastically affects the performance of the network. In this paper, a fair and effective incentive mechanism, which induces cooperation among nodes in the network is proposed. The mechanism applies auction scheme by initiating auction between the node and its immediate neighbouring nodes. The neighbouring node(s) competitively purchase packets transmission liability from the source and re-auctions it to the neighbouring node. The performance characterisation and evaluation against fairness and some possible attacks demonstrated that the scheme strongly stimulates fairness and competitiveness in message relaying among the intermediary nodes unlike other incentive based schemes.

Analyzing and designing energy efficient routing protocol in delay tolerant networks

Delay tolerant networks (Barun Saha, http://delay-tolerant-networks.blogspot.in) are the networks that address the technical issues in heterogeneous network that may lack continuous network connectivity. A message is forwarded to a node if it has higher delivery predictability than the current node for that particular destination. But there obviously exists a tradeoff between delivery delay and energy consumption (Yoon et al. in Tradeoff between energy consumption and lifetime in delay-tolerant mobile network, 2008), as a message (or a file) has to be delivered to each of several destinations by epidemic relaying. With every relay due to the various nodes, energy is consumed by the node. This adds to the total energy spent in relaying and thus increases the network overhead. As the energy available to a particular node is limited, there is a need to conserve this energy. This paper investigates the Energy Aware Prophet protocol and the methods to optimize the delivery probability. Threshold Algorithm and Remaining Required Energy Algorithm (Kaviani et al. in Delay tolerant routing protocols for energy-neutral animal tracking, 2015) leads to an increase of about 42% in delivery probability and energy is saved by 47%. Also, we have found that the Threshold Algorithm leads to the optimal energy value (i.e. threshold value) as 49 J as a constraint to the current energy. Further, a buffer size higher than 8 M is not recommended, as the delivery probability remains constant after 8 M buffer size.

4PR: Privacy preserving routing in mobile delay tolerant networks

Message routing is one of the major challenges in Mobile Delay Tolerant Networks (MDTNs) due to frequent and long-term network partitions. A number of routing protocols for MDTNs belong to the category of prediction-based routing protocols, which utilize the social encounter probability of nodes to guide message forwarding. However, these prediction-based routing protocols compromise the privacy of the nodes by revealing their mobility patterns. In this paper, we propose the Privacy Preserving Probabilistic Prediction-based Routing (4PR) protocol that forwards messages by comparing aggregated information about communities instead of individual nodes. Specifically, it compares the probability that at least one node in a community will encounter the destination node. We present theoretical security analyses as well as practical performance evaluations. Our simulations on a well established community-based mobility model demonstrate that our routing protocol has comparable performance to existing prediction-based protocols. Additionally, the community information is computed efficiently and independently of the routing protocol.

SPF-ECP: Self-Organized, Predictive, and Fast Adaptive: Enhanced Clustering Protocol for DTMN Routing

One type of computer networks which are deficient due to its discontinuous character of network partitioning is a Delay Tolerant Mobile Network. DTMN issues are how to stabilize, maintain, and update currently presents mobile nodes to accomplish improved routing of packets making sure there is no loss in the packet. Issues of DTMN addressed by defining the basic idea of SPF-ECP based clustering scheme for DTMN with a high degree of mobility nodes, where a node may modify the allied cluster head numerous times during its connection period. The proposed clustering scheme consists of clustering at its initial stages. The cluster groups the mobile nodes together. The mobile nodes are grouped with comparable clustering in the mobility pattern into a clustering group beforehand a packet is being routed. In addition, an adaptive scheme also used to control prediction by examining the performance tradeoff between limiting prediction cost and reducing communication cost, with an algorithm to enable or disable prediction operations. A node with higher contact probability becomes a member than the preset threshold node. `Hello packets' inclusion used to crisscross the node presence position. Performance analysis shows the best possible route and adaptive route in order to reach the destination with the greatest delivery rate.

Inter-Session Network Coding-Based Policies for Delay Tolerant Mobile Social Networks

We consider delay tolerant mobile social networks (DTMSNs), which are opportunistic networks made of human-carried wireless devices clustered into social communities. In such environments, routing is a challenge as the limited resources (such as memory and contact opportunities) must be efficiently used and shared between the sessions (or users, contents). To handle several unicast sessions, inter-session network coding (ISNC) has been proved necessary for optimal throughput in general networks, but is a delicate problem as it can quickly get detrimental. This paper investigates that ISNC can be beneficial to DTMSNs when used on top of a social-aware routing algorithm, whereas we exemplify and make explicit why any gain can hardly be expected with greedy replication, in regard to the current literature on ISNC. We then design decentralized criteria to control when and where in the network ISNC should be triggered, based on the node features (buffer size and social relationships) and network current load. These criteria are tested extensively on real-world contact traces, in terms of various metrics, such as number of deliveries, mean delay, or fairness. Our online ISNC protocol builds on the SimBet utility-routing policy. Our ISNC protocol can, however, run on top of any social-aware routing.

Distance-Based Energy-Efficient Opportunistic Broadcast Forwarding in Mobile Delay-Tolerant Networks

Mobile-relay-assisted forwarding in delay-tolerant networks (DTNs) can improve network capacity and packet delivery ratio but, at the same time, may significantly increase energy consumption at the system level. In this paper, we propose a distance-based energy-efficient opportunistic forwarding (DEEOF) framework for the broadcast transmission in mobile DTNs. DEEOF strikes a balance between energy consumption and network performance by maximizing the energy efficiency while maintaining a high packet delivery ratio. In the proposed algorithms, we define the metric of the forwarding equivalent energy efficiency distance (FEED) for broadcast transmission to quantify the transmission distances achieving the same energy efficiency at different time instances, or with different numbers of the relays in the source's transmission radius. Based on the concept of FEED, we propose two DEEOF algorithms for opportunistic broadcast forwarding, which makes the forwarding decision by comparing the current energy efficiency with the estimated future expectation and distribution, respectively. The performance improvement of the proposed DEEOF algorithms is also demonstrated by simulation, particularly for the cases in which the source has very limited battery reserves.

Optimization Problems in Throwbox-Assisted Delay Tolerant Networks: Which Throwboxes to Activate? How Many Active Ones I Need?

One of the solutions to improve mobile Delay Tolerant Network (DTN) performance is to place additional stationary nodes, called throwboxes, to create a greater number of contact opportunities. In this paper, we study a key optimization problem in a time-evolving throwbox-assisted DTN: throwbox selection, to answer the questions such as “how many active throwboxes do I need?” and “which throwboxes should be activated?” We formally define two throwbox optimization problems: min-throwbox problem and k-throwbox problem for time-evolving DTNs modeled by weighted space-time graphs. We show that min-throwbox problem is NP-hard and propose a set of greedy algorithms which can efficiently provide quality solutions for both challenging problems.

Wireless mobile DTN routing with the extended minimum estimated expected delay protocol

We present the Extended Minimum Estimated Expected Delay (EMEED) protocol for routing in wireless mobile Delay-Tolerant Networks (DTNs) comprising very large numbers of nodes with nonuniform, correlated mobility patterns.Under EMEED, packets are routed on graphs that are created taking into account (i) estimates of the expected delays until node pairs are within RC hops of each other and (ii) information on which node pairs are currently within RC hops of each other — RC is a tunable parameter. EMEED is inspired by the Minimum Estimated Expected Delay (MEED) protocol; it may be viewed as an extension of the basic routing method of MEED coupled with a suite of mechanisms that maintain the resulting control overhead at manageable levels. Packet replication is not employed.We evaluate the performance of EMEED through simulations in a pocket switched network and a vehicular DTN, comparing it with MEED, BUBBLE, Spray & Wait and flooding. We find that EMEED is superior to these other protocols in terms of jointly optimizing the packet delivery rate and the wireless channel usage efficiency.

An approach for routing in delay tolerant mobile ad-hoc networks using quadrant-based look-ahead method

It is difficult for delay tolerant Mobile Ad-Hoc Networks MANETs to render the end-to-end paths from source to the destination where there is no proper connectivity. Opportunistic routing overcomes the deficiencies of conventional MANET routing, and the proposed algorithm works based on quadrant-based look-ahead approach, which is highly efficient in managing the traffic uniformly, conserving energy, and increasing the lifetime of nodes as well as improving the route network stability. The proposed method aimed at reducing the amount of time that packet spends in the buffers. Simulation studies reveal that the proposed novel routing approach outperforms the existing methods.

Data gathering and offloading in delay tolerant mobile networks

Mobile sensing emerges as an important application for mobile networks. Smartphones equipped with sensors are used to monitor a diverse range of human activities. One key and challenging procedure ...

Efficient Packet Routing in Highly Mobile Wireless Networks

Traditional mobile ad-hoc network (MANET) and delay tolerant network (DTN) routing schemes work properly only under the limited assumptions. MANET routing schemes are designed for densely populated networks while DTN routing schemes were developed for dealing with intermittently connected topologies. However, in a real environment, the assumption cannot be hold: the density of nodes constantly changes and a network can be separated due to node mobility even when it is composed of large number of nodes. We propose a routing scheme for maximizing the delivery rate in a network with varying density. In the proposed scheme, data packets are used to search an available path while they are delivered by DTN-based routing. If a path exists, subsequent packets are relayed along the path. Otherwise, packets are delivered continuously using DTN-based routing. Using simulation we show that the proposed scheme achieves high throughput and a low overhead in a dense part of the network, while it outperforms existing DTN routing schemes in an intermittently connected situation.