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Delay tolerant networks (DTNs) is a network evolved from mobile networks. Differing from the traditional network, which has a stable end‐to‐end transmission path, DTNs are sparse and intermittently connected mobile ad hoc network, which are widely used in harsh environments, such as battlefields, seabed, space communication networks, and so on. In DTNs, intermittent connectivity, partitioned network, long delays and node mobility characteristics make the network fail to communicate frequently, therefore, how to successfully forward the message is of extreme importance. Up to now, almost all the traditional models in DTNs use the store‐carry‐forward method. This paper proposes a novel clustered DTN routing model based on sensing node relationship strength. The routing mechanism takes advantage of the number of other nodes encountered by the nodes in the process of movement and the changes in the number of nodes to calculate the strength of the relationship between nodes, and clusters DTN routing according to the strength of the relationship between nodes. Moreover, the relationship between nodes in a cluster and other clusters is used to transmit messages between clusters, and messages are transmitted within clusters according to the strength of the relationship between nodes. Simulation results show that the routing mechanism not only increases the success rate of message transmission, but also reduces the transmission delay of messages and improves network performance. [ABSTRACT FROM AUTHOR]

Summary: This paper aims to investigate the potential advantages and also the limits of source routing when applied to delay‐/disruption‐tolerant networking (DTN) space networks. To this end, it uses a variant of contact graph routing (CGR) called moderate source routing (MSR), recently proposed by the authors and fully compatible with interplanetary overlay network (ION), the DTN suite developed by NASA‐JPL. MSR differs from standard CGR as the route to destination is not recalculated from scratch at each node, but possibly reused, if still valid, by next nodes. For this purpose, the route is saved in a dedicated extension block of the forwarded bundle (the data unit of the bundle protocol, used in DTN). Performance of MSR versus CGR is assessed by considering a simple but very challenging space layout. Numerical results, obtained on a GNU/Linux testbed, show that MSR is effective at reducing the chances of loops, in particular when the source has full knowledge of the state of the network; otherwise, network instabilities are still possible. In this case, they can be neutralized by means of the combined use of source routing and anti‐loop tools, as shown in the paper. A further advantage of MSR is that it is compatible with standard CGR, which would facilitate a gradual or partial deployment. [ABSTRACT FROM AUTHOR]

Summary: The Delay‐/Disruption‐Tolerant Networking (DTN) architecture was designed to cope with challenges such as long delays and intermittent connectivity. To exploit the a priori knowledge of contacts, typical of space networks, NASA‐JPL designed and included in ION (its DTN protocol suite) the Contact Graph Routing (CGR) algorithm. This paper studies the latest version, recently standardized as Schedule‐Aware Bundle Routing (SABR) within the Consultative Committee for Space Data Systems (CCSDS). The first part of the paper is devoted to the algorithm analysis, which distinguishes three logical phases to examine sequentially. Following this comprehensive study, three enhancements are proposed, which aim to improve SABR accuracy and resistance against possible loops. They are studied on a simple but challenging DTN topology, implemented on a virtual GNU/Linux testbed. Tests are performed by running the latest version of ION and an independent implementation of SABR developed by the authors, Unibo‐CGR. The numerical results are then examined in detail to highlight both SABR mechanisms and the advantages offered by the proposed enhancements. [ABSTRACT FROM AUTHOR]

Summary: In delay‐tolerant networks (DTN), node connection time and message transmission time are two important influencing factors that can improve the delivery rate. In this paper, we first define a new concept called communication capability (CC) and then apply this concept to the delivery predictability formulation in Prophet and improve it. Then, in Prophet, the selection of relay nodes relies only on the delivery predictability and ignores the caching and forwarding capability of the node. Therefore, we combine delivery predictability, buffering, and forwarding capability to develop a new adaptive relay node selection strategy. Subsequently, we define two metrics called message priority (MP) and message strength (MS). The node forwards messages sequentially based on message priority and discards messages based on message strength. Finally, we present a probabilistic routing algorithm based on node communication capability and message strength (CAMS). The simulation results show that compared with traditional routing algorithms, the CAMS can effectively improve the message delivery rate, reduce the overhead ratio, and keep average hop counts low. [ABSTRACT FROM AUTHOR]

Summary: Opportunistic ad hoc networks (OppNets) are characterized by intermittent and infrastructure‐less connectivity among mobile nodes with limited internode communication and buffer space. Without persistent end‐to‐end routing information, replication‐based routing techniques are often used to distribute duplicate messages in OppNets, which unfortunately leads to enormous costs of transmission, storage, and energy resources. Prior replication‐based routing schemes were mainly based on several premises, for example, the availability of global network knowledge, unlimited bandwidth capacity, and homogeneous contact patterns. In this paper, we propose a quota‐based routing scheme with finite buffer management, named QRBP, regardless of these weak premises. The QRBP scheme comprises two essential functions. First, only a portion of nodes with higher mobility are delegated to carry a certain quota of message replicas and disseminate those messages to nodes with lower mobility. The message traffic can be evenly diverted to relay nodes, which reduces the transmission overhead in the network. Second, nodes can manipulate message scheduling and dropping to improve the successful delivery rate according to heuristic strategies based on several measures of the quota value, remaining time‐to‐live, and contact rate with the destination. Furthermore, our study conducts extensive simulations under both synthetic and real mobility scenarios. In terms of transmission overhead ratio and successful delivery rate, the QRBP scheme performs better than Epidemic, Spray and Wait, and Temporal Closeness and Centrality‐Based (TCCB) routing schemes, as well as common buffer management policies like Drop Oldest, Drop Newest, Drop Random, and Space‐Time Drop. [ABSTRACT FROM AUTHOR]

Summary: In the traffic monitoring system, the transportation department generates the traffic map to report the real‐time traffic conditions, so as to provide more efficient service for drivers. However, if the vehicle obtains the local traffic conditions that the driver is more concerned about from the remote server, it will consume a heavy bandwidth and incurs an increased response delay. Generating and broadcasting local traffic conditions through fog computation is a feasible method to reduce communication costs, and most existing traffic monitoring systems based on fog computation are implemented using Bilinear Pairing operations. In this paper, we propose Lightweight and Privacy‐preserving Traffic Monitoring (LPTM) scheme with Elliptic Curve Cryptosystem, an optimized Timed Efficient Stream Loss‐tolerant Authentication protocol is adopted to achieve efficient and secure communication, and we also use an identity‐based signature scheme with partial message recovery to effectively shorten the length of the fog node broadcast message. Detailed security proofs show that the requirements of security and privacy are all achieved, and better simulation performance is presented in both computation and communication overhead. [ABSTRACT FROM AUTHOR]

Summary: The topology of the navigation satellite network with agility link evolves with chain‐building slots periodically. The navigation data are transmitted in a "store, carry and forward" manner without requiring end‐to‐end paths. Thus, the navigation satellite network with agility link can be considered as a deterministic delay tolerant network (DTN). The data transmission of navigation satellite network is limited by chain‐building slot and bandwidth. To utilize network transmission link and communication bandwidth fully, this paper proposed an algorithm called parallel data transmission for the navigation satellite network with agility link. Based on the network characteristics, the algorithm is designed with polling pattern of link establishment and formulated as parallel data transmission problem based on deterministic scheduling DTN. Then, we design the method based on Dynamic Game from the view of data, while the Dynamic Programming method is proposed referring to Linear Programming–based method for optimization. Finally, the results were compared with three methods using the standard network routing metrics and showed that the proposed algorithm is better than the existing methods. [ABSTRACT FROM AUTHOR]

Summary: Vehicular Ad‐hoc Network (VANET) is a vehicle‐to‐vehicle communication technology, which is highly promising due to its continuous demand, applicability, and suitability for public safety. The vehicular nodes establish communication with each other for exchanging traffic data and road maps, especially when warning messages need to be broadcasted on the network during emergency situations. Therefore, accurate vehicle information is necessary in such circumstances to improve the accuracy of Non‐Line‐of‐Sight (NLOS) node localization. In this paper, a Driving Training‐Based Optimization for NLOS Node Localization (DTO‐NL) Scheme is proposed for facilitating better warning message delivery during emergency situations in vehicular networks through a dynamic increase and decrease in the search based on the position of unknown NLOS nodes from the considered anchor nodes employed for localization. The performance of the suggested technique has been analyzed based on parameters like warning message delivery rate, latency, localization error, channel utilization rate, energy consumption, and packet delivery ratio. The proposed DTO‐NL scheme enhances the warning message delivery rate by 9.81%, 11.28%, 14.38%, and 17.64% compared to WIDVBA , ROA‐APS , ILL‐WOA‐NLOS , and WDHPBDS techniques. [ABSTRACT FROM AUTHOR]

Summary: Delay tolerant network (DTN) has attracted significant attention of the researchers due to its capability of delivering the message even in the situation where network connectivity is irregular. Irregular networks result in non‐delivery of data to user at right time, and the same is not possible with traditional algorithms due to requirement of end‐to‐end connectivity between nodes. DTN uses story–carry–forward technique to deliver a message in the environment of disconnection. Hence, for message transmission from source node to destination node, a relay node or forwarder node is required. The efficiency of the network is mainly dependent on the selection of forwarder node. Hence, forwarder node selection is very crucial in DTNs. The objective of this paper is to propose an efficient relay node selection technique integrated with fuzzy logic, based on four properties of node, namely, number of encounters, residual energy, buffer capacity, and speed so that performance metrics of the network can be improve. Proposed method uses fuzzy logic to decide which node should be selected as relay node in multi hop strategy. The study of simulation results indicate that proposed algorithm improves performance of the network with regards to delivery ratio, delay, hop count, and throughput. [ABSTRACT FROM AUTHOR]

Summary: In mobile social networks (MSN), portable devices of mobile users communicate with each other. The contact and intercontact times are the two most important parameters that specify the behavior of MSN. Many social features such as similarity, centrality, closeness, and distance are derived from contact and intercontact time patterns. Those parameters and features can be used in the community detection process in community‐based routing as a vector weight of network graph edges. But there is no solution for proper exploitation of them as a multicriteria optimization of community detection algorithms so that the communities become more adaptive with the MSN quiddity and the computational complexity of the algorithms to be stay constant. In this paper, we propose the MSN‐adaptive community detection framework, MSN‐CDF, which meets these demands. We improve the quality function of community detection methods, for example, the Intensity in clique percolation methods and the Modularity in modularity‐based methods, through our new model‐based joint optimization of their quality functions. To this end, to express the MSN contact and social features, we develop a criterion called MCSF. It holds the contact time and intercontact time distributions parameters and implies their social features for MSN purposes. This criterion has as little traffic as possible and enjoys from the probabilistic joint distribution model. The simulations show that MSN‐CDF reduces the network overhead significantly compared with the DiBUBB, Epidemic, and Dynamic Routing. Moreover, it outperforms DiBUBB and Dynamic Routing in terms of delivery rate and delivery latency. [ABSTRACT FROM AUTHOR]

Optical burst switching (OBS) is the most favourable switching paradigm for future all-optical networks. Burst assembly is the first process in OBS and it consists of aggregating clients packets into bursts. Assembled bursts wait for an offset time before being transmitted to their intended destinations. Offset time is used to allow burst control packet reserve required resources prior to burst arrival. Burst assembly process and offset-time create extra delay in OBS networks. To make OBS suitable for real time applications, this extra latency needs to be controlled. This paper proposes and evaluates a novel offset time and burst assembly scheme to address this issue. Constant bit rate (CBR) traffic that has stringent end-to-end delay QoS requirements is used in this study. The proposed scheme is called hybrid offset-time and burst assembly algorithm (H-OTBA). The objective of the paper is achieved by controlling maximum burst transfer delay parameters of CBR. The proposed scheme was evaluated via network simulation. Simulation results demonstrate that, H-OTBA has effectively reduced end-to-end delay for CBR traffic compared with current solutions. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In 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. [ABSTRACT FROM AUTHOR]

Summary: Opportunistic networks aim to deal with the unpredictable environment for data communication. Messages in opportunistic networks need to be stored with the node in the absence of any suitable forwarder. With such a store‐carry‐forward paradigm, it aims to eliminate challenges of no pre‐determined/fixed connectivity, absence of direct/in‐direct routes from source to destination, and high error rate and delay in the network. Node carrying message roams in the network to find a suitable forwarding node. In this study, the survey for various routing protocols and mobility models for opportunistic networks is discussed along with tools available for simulations of opportunistic networks. Further, various challenges in opportunistic networks such as storage management, congestion management, and energy constraints are discussed. Many applications for the opportunistic network, along with real‐time case study, are presented in the paper. The objective of the study is to provide future direction to the researchers, along with the systematic review. Hence, future objectives are discussed to mitigate the challenges faced in the current scenario. Also, based upon the study, it is observed that most researchers have taken epidemic, ProPHET, and spray and wait routing protocols as their base of study. Performance analysis for these protocols is done using opportunistic network environment (ONE) simulator. [ABSTRACT FROM AUTHOR]

Summary: Size and weight limitations of low‐Earth orbit (LEO) small satellites make their operation rest on a fine balance between solar power infeed and power demands of supporting communication technologies, buffered by on‐board battery storage. As a result, the problem of planning battery‐powered intersatellite communication is a very difficult one. Nevertheless, there is a growing trend toward constellations and mega‐constellations that are to be managed using sophisticated software support. In earlier work, we have discussed how the effective construction of contact plans in delay‐tolerant satellite networking can profit from a refined model of the on‐board battery behavior. This paper presents a profound study of the scalability of the approach and discusses how to tailor it to the needs arising in the management of mega‐constellations, together with a variety of improvements to the base approach. Results show that efficient mega‐constellation operations are compromised, encouraging further research on the area. [ABSTRACT FROM AUTHOR]

Summary: Designing a safe and reliable way for communicating the messages among the devices and humans forming the Opportunistic Internet of Things network (OppIoT) has been a challenge since the broadcast mode of message sharing is used. To contribute toward addressing such challenge, this paper proposes a Random Forest Classifier (RFC)‐based safe and reliable routing protocol for OppIoT (called RFCSec) which ensures space efficiency, hash‐based message integrity, and high packet delivery, simultaneously protecting the network against safety threats viz. packet collusion, hypernova, supernova, and wormhole attacks. The proposed RFCSec scheme is composed of two phases. In the first one, the RFC is trained on real data trace, and based on the output of this training, the second phase consists in classifying the encountered nodes of a given node as belonging to one of the output classes of nodes based on their past behavior in the network. This helps in proactively isolating the malicious nodes from participating in the routing process and encourages the participation of the ones with good message forwarding behavior, low packet dropping rate, high buffer availability, and a higher probability of delivering the messages in the past. Simulation results using the ONE simulator show that the proposed RFCSec secure routing scheme is superior to the MLProph, RLProph, and CAML routing protocols, chosen as benchmarks, in terms of legitimate packet delivery, probability of message delivery, count of dropped messages, and latency in packet delivery. The out‐of‐bag error obtained is also minimal [ABSTRACT FROM AUTHOR]

Mobile social networks are presenting new opportunities for content dissemination. User location, mobility, and social communities can be used to deliver delay-tolerant content. Most existing dissemination methods either fail to consider the user's interest in their protocol design or just allow exchange of contents between nodes that have a similar interest. If nodes with similar interest never encounter each other, then contents might not be exchanged with them. In this paper, we propose a method in which user location, mobility, and interest as well as certain limiting factors such as relay buffer size and communication overhead are used to select a set of relays for targeted advertisement distribution. Besides, our method does not depend on nodes with similar interest encountering one another. In the proposed method, a distribution agent exploits user location, mobility, and social networks as well as the interest of destinations to select a group of relays to carry content to the targeted destinations. Users move among social communities and carry advertisements to their peers in other communities. We have also developed an optimization problem for advertisement selection and scheduling. Since the problem is NP-hard, we propose a heuristic solution. Evaluation of the proposed approach shows that the algorithm is not sensitive to network resource variation and readily outperforms popular methods reported in the literature in terms of delay, delivery ratio, and interest compatibility. [ABSTRACT FROM AUTHOR]

When mobile devices involved in a communication process are unable to establish a direct connection, or when communication should be offloaded to cope with large throughputs, mobile collaboration can be used to enable communication through opportunistic networks. These types of networks are formed when mobile devices communicate only using short-range transmission protocols, usually when users are close. Routes are built dynamically, because each mobile device is acting according to the store-carry-and-forward paradigm. Thus, contacts are seen as opportunities to move data towards the destination. In such networks, the routing protocol is of vital importance, and today, we witness quite a number of routing algorithms that have been proposed to maximize the success rate of message delivery whilst minimizing the communication cost. Such protocols take advantage of the devices history of contacts, or information about users carrying the mobile devices, to make their forwarding decision. This paper extends our previous work with the following: First, we describe a new simplified, fast simulator, designed to minimize the work needed to conduct extensive tests for opportunistic routing algorithm on multiple traces; next, we analyze extensively several of the most popular routing algorithms through extensive simulations conducted using our simulation platform. We highlight their pros and cons in different scenarios, considering different real-world mobility data traces, such as Global Positioning System traces. The raw Global Positioning System traces are converted to a format based on encounters between participating entities. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Summary: The reliability of data dissemination in vehicular ad hoc network (VANET) necessitates maximized cooperation between the vehicular nodes and the least degree of congestion. However, non‐line of sight (NLOS) nodes prevent the establishment and sustenance of connectivity between the vehicular nodes. In this paper, a hybrid seagull and thermal exchange optimization (TEO) algorithm‐based NLOS node detection technique is proposed for enhancing cooperative data dissemination in VANETs. It inherits three different versions of the proposed hybridized algorithm; three different approaches for localization of NLOS nodes depending upon its distance from the reference nodes are incorporated. It is considered as a reliable attempt in effective NLOS node localization as it is predominant in maintaining the balancing the degree of exploration and exploitation in the search process. In the first variant, the method of the roulette wheel is utilized for selecting one among the two optimization algorithm. In the second adoption, this hybridization algorithm combines TEO algorithm only after the iteration of SEOA algorithm. In the final adoption, the predominance of the seagull attack mode is enhanced by including the heat exchange formula of TEO algorithms for improving exploitation capability. The simulation experiments of the proposed HS‐TEO‐NLOS‐ND scheme conducted using EstiNet 8.1 exhibited its reliability in improving the emergency message delivery rate by 14.86%, a neighborhood awareness rate by 13%, and the channel utilization rate by 11.24%, compared to the benchmarked techniques under the evaluation done with different number of vehicular nodes and NLOS nodes in the network. [ABSTRACT FROM AUTHOR]

Summary: Different devices with different characteristics form a network to communicate among themselves in Internet of Things (IoT). Thus, IoT is of heterogeneous in nature. Also, Internet plays a major role in IoT. So, issues related to security in Internet become issues of IoT also. Hence, the group and hierarchical management scheme for solving security issues in Internet of Things is proposed in this paper. The devices in the network are formed into groups. One of the devices is selected as a leader of each group. The communication of the devices from each group takes place with the help of the leader of the corresponding group using encrypted key to enhance the security in the network. Blom's key predistribution technique is used to establish secure communication among any nodes of group. The hierarchy is maintained such that the security can be increased further, but the delay is increased as it takes time to encrypt at every level of hierarchy. Hence, the numbers of levels of hierarchy need to be optimized such that delay is balanced. Hence, this algorithm is more suitable for delay‐tolerant applications. The performance of the proposed Algorithm is evaluated and is proved to perform better when compared with the legacy systems like Decentralized Batch‐based Group Key Management Protocol for Mobile Internet of Things (DBGK). [ABSTRACT FROM AUTHOR]

Summary: Wireless sensor networks (WSNs) have received a lot of attention from both academia and industry due to the increasing need for ubiquitous computing for monitoring applications, the continuous advances in miniaturization of electronic devices, and the ultra‐low‐power wireless technologies. These innovations in technology have driven the curiosity to use sensor networks in a new kind of applications such as road track or railway monitoring, border monitoring, oil and gas, or even water pipeline monitoring. Due to the underlying linear topology of these applications, a new type of network, called a linear sensor network (LSN), has emerged. Because of the specific characteristics of this application and the resource constraints of sensors, some of the major challenges faced in LSNs are to reduce end‐to‐end delays, to maximize the packet delivery ratio to a sink, and an even distribution of the load between nodes. To achieve these objectives, it is necessary to control node‐to‐node packet traffic conditions and to manage radio interference created by simultaneously active nodes. This paper addresses these challenges and proposes a new method of clustering LSNs that reduces or controls radio interference risks in order to satisfy these objectives, application needs, and the resource limitations of sensor nodes in the best possible way. This method is applied for LSNs using a token‐passing mechanism to access the medium. The performance evaluation is conducted by using a realistic propagation model in the analytical evaluation and also a NS‐2 simulation process. [ABSTRACT FROM AUTHOR]

Summary: Routing is a process of selecting a path in a network for delivering a packet from source node to destination node. Successful delivery of a message is a challenge, and therefore, this paper proposes an algorithm for a wireless network called Optimized Routing in wireless networks using Machine Learning (ORuML), which uses machine learning algorithm namely, K‐nearest neighbor (KNN), Support Vector Machine (SVM), and Multinomial Logistic Regression (MLR), to predict the network type of the source and destination nodes. The ML model is trained by using characteristic features of a node collected in real time such as battery power utilization, available internal storage, IP address, and range of a node. Intuitively, the MLR should outperform KNN and SVM in terms of accuracy and Area under ROC Curve (AUC). The proposed algorithm determines whether the source and destination nodes are co‐located and also, determines the best neighboring hop for efficient routing. [ABSTRACT FROM AUTHOR]

Summary: With the advancement in wireless technology and portable devices, smart phones have become one of the belongings of human being. People share their data online, but it has limitations due to transmission range and mobility. Yet opportunistic mobile social network enables users to share data online even if there is no connected path between source and destination. The widespread use of mobile phones equipped with WiFi, Bluetooth, and several other components and contact opportunities among humans bridge the gap between internet available and nonavailable area. In this paper, we have proposed a new routing approach which utilizes both spatial and temporal attributes of user such as probability to meet a particular location and remaining intercontact time between two nodes to select better relay nodes. Generally, users visit different locations such as sports stadium and mall, with varying probability. Users with similar interest form group, and each user has different intercontact time with other users according to their point of interest and visiting pattern. By utilizing multiattributes, different forwarding strategies have been devised for both inter and intragroup routing. The proposed work "point of interest (PoI)‐based routing" is implemented in Opportunistic Network Environment simulator, and the performance is analysed in terms of delivery rate, latency, overhead, goodput, and energy consumed. The simulation results show that PoI diminishes 23% of overhead and yields 24% improvement in goodput over the state‐of‐the‐art protocol. Thus, the simulation results reveal that our proposed work provides the balance between routing performance and resource consumption. [ABSTRACT FROM AUTHOR]

Summary: Opportunistic networks (OppNets) are composed of wireless nodes opportunistically communicating with each other. These networks are designed to operate in a challenging environment characterized by high delay, intermittent connectivity, and no guarantee of fixed path between the sender and the destination nodes. One of the most vital issues in designing and maintaining practical networks over a time period is the security of the messages flowing in OppNets. This paper proposes a new method called message trust‐based secure multipath routing protocol (MT‐SMRP) for opportunistic networks. Various routing protocols such as ProPHet, Epidemic, and HiBOp, to name a few, have been proposed for OppNets, but none of these have applied a secure multipath routing technique. The proposed MT‐SMRP scheme relays the message to the destination through the disjoint paths, each applying a soft‐encryption technique to prevent message fabrication attacks. Simulations are conducted using the Haggle Infocom'06 real mobility data traces, showing that when time‐to‐live is varied, (1) the proposed MT‐SMRP scheme outperforms D‐MUST by 18.10%, 7.55%, 3.275%, respectively, in terms of delivery probability, messages dropped, and average latency; (2) it also outperforms SHBPR by 21.30%, 7.44%, and 4.85%, respectively, in terms of delivery probability, messages dropped, and average latency. Under similar performance metrics, the performance of MT‐SMRP is also shown to be better than that of D‐MUST and SHBPR when the buffer size (respondents. the message generation interval) is varied. [ABSTRACT FROM AUTHOR]

Summary: With the advent of the Internet of Things (IoT), more and more devices can establish a connection with local area networks and use routing protocols to forward all information to the sink. But these devices may not have enough resources to execute a complex routing protocol or to memorize all information about the network. With proactive routing protocols, each node calculates the best path, and it needs enough resources to memorize the network topology. With reactive routing protocols, each node has to broadcast the message to learn the right path that the packets must follow. In all cases, in large networks such as IoT, this is not an appropriate mechanism. This paper presents a new software‐defined network (SDN)–based network architecture to optimize the resource consumption of each IoT object while securing the exchange of messages between the embedded devices. In this architecture, the controller is in charge of all decisions, and objects only exchange messages and forward packets among themselves. In the case of large networks, the network is organized into clusters. Our proposed network architectures are tested with 1000 things grouped in five clusters and managed by one SDN controller. The tests using OpenDayLight and IoT embedded applications have been implemented on several scenarios providing the ability and the scalability from dynamic reorganization of the end‐devices. This approach explores the network performance issues using a virtualized SDN‐clustered environment which contributes to a new model for future network architectures. [ABSTRACT FROM AUTHOR]

Summary: Approximate computing‐based arithmetic units are oriented towards reduction in power, delay, and area. Intrinsic error tolerance capability of emerging application domains, like multimedia, Internet of Things (IoT), and image processing provides better opportunities for optimization of approximate arithmetic units. In this paper, a novel 1‐bit imprecise full adder (IFA) is proposed with less gate count. Also, two versions of 16‐bit error tolerant adders (ETAs), namely a low power and area efficient error tolerant adder (LETA) and improved low power and area efficient error tolerant adder (ILETA), are proposed. In these proposed ETAs, the most significant bit (MSB) segments are realized in same approach, whereas the least significant bit (LSB) segment of LETA and ILETA are realized using an existing modified full adder (MFA) and proposed IFAs, respectively. The proposed and existing ETA adders are implemented using a Verilog hardware description language (HDL) and synthesized in a Synopsys electronic design automation (EDA) Tool using Taiwan Semiconductor Manufacturing Company (TSMC) 65nm technology. The proposed (ILETA, LETA) adders exhibit (55%, 50%) reduction in power consumption and achieve significant reduction in area (68%, 61%). Further, in this work, a new performance metric namely power and error product (PEP) is proposed in order to evaluate the approximate adders in terms of power and error metrics. It is found that the proposed ILETA achieves a low PEP of 1.05 ×10−5 compared with other ETAs. To study the efficacy of the proposed ETA adders in image processing application, an image blending algorithm is implemented and simulated using MATLAB. From simulation results, it is observed that the proposed ETA adders exhibit a high peak signal‐to‐noise ratio (PSNR). [ABSTRACT FROM AUTHOR]

In this paper, finite‐time stabilization of coupled systems on networks with time‐varying delays (CSNTDs) via periodically intermittent control is studied. Both delayed subsystems and delayed couplings are considered; the self‐delays of different subsystems in delayed couplings are not identical. A periodically intermittent controller is designed to stabilize CSNTDs within finite time, and the stabilization duration is closely related to the topological structures of networks. Furthermore, two sufficient criteria are developed to ensure CSNTDs under periodically intermittent control can be stabilized within finite time by using an approach that combines the Lyapunov method with Kirchhoff's Matrix Tree Theorem. Then finite‐time stabilization of coupled oscillators with time‐varying delays is given as a practical application and sufficient criteria is obtained. Finally, a numerical simulation is proposed to support our results and show the effectiveness of the controller. [ABSTRACT FROM AUTHOR]

In this paper, we propose delay-universal or 'anytime' code design for multiple access channels. The anytime characteristics of the proposed coding scheme are investigated asymptotically over two different multiple access channels. For the simplest multiple access channel, we derive the analytical delay-exponent of the proposed code by using mathematical induction technique. Through comparison, we show that the analytical delay-exponent matches with the delay-exponent obtained from numerical results. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In delay tolerant networks, most of the existing message forwarding algorithms prefer to deliver messages to the nodes with a higher popularity or centrality in the hope of maximizing the delivery ratio or minimizing the end-to-end delay. This forwarding scheme is prone to cause unfair load distribution and further lead to network congestion, overlooked in the previous work. In this paper, we discuss the network congestion from a community perspective and take it into account the design of message forwarding algorithms. We first put forward a novel distributed community detection approach, which could track the evolution of communities. Based on the identified communities, we develop a congestion avoidance mechanism to divert the load away from the congested areas to the alternative custodians and further present a congestion-aware message forwarding algorithm where messages can avoid being transmitted to the congested nodes. We finally evaluate the effectiveness of distributed community detection and congestion-aware message forwarding through the extensive real-trace driven simulations. [ABSTRACT FROM AUTHOR]

Because of the uncertainty of transmission opportunity in delay tolerant networks (DTN), routing algorithms in DTN often need nodes to serve as relays for others to carry and forward messages. One classic policy is the Epidemic routing (ER) algorithm. To reduce the overhead, the hop-limited ER protocol is proposed. This method can get better performance through controlling the message hop count. However, because of the energy constraint or other factors, each node may forward only limited times, that is, both the message hop count and the forwarding times may be limited. This paper proposes a unifying framework to evaluate the performance of ER with the aforementioned constraints. Simulations based on both synthetic and real motion traces show the accuracy of the framework. In addition, we explore the impact of many parameters (e.g., message hop count) through extensive numerical results. For example, numerical results show that both the message hop count and the forwarding times can have certain impact on the routing performance, but their impact is related with many other factors (e.g., the number of nodes). Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper, the exponential synchronization of dynamical network with distributed time delays is investigated. The intermittent controllers are designed to achieve the exponential synchronization. Based on the Lyapunov function method and the mathematical analysis technique, some synchronization criteria with respect to the system parameters, control gain and control rate are presented. From the criteria, for any given dynamical network, the needed values of control gains and rate can be easily estimated. Finally, two numerical simulations are performed to verify the derived theoretical results. [ABSTRACT FROM AUTHOR]

SUMMARY Delay-Tolerant/Disruption-Tolerant Networking (DTN) architecture will be used in future deep space missions, to enable autonomous networking operations and disruption-tolerant data communications. Therefore, it is worth analyzing the performance of the DTN Bundle Protocol (BP) in a realistic deep space environment, reproducing the characteristics of Mars missions. After a comprehensive introduction on data communications between Mars and Earth, the paper presents the essential features of both the BP DTN architecture and the Licklider Transmission Protocol (LTP), adopted here as BP convergence layer on deep space links, thanks to its ability to cope with the very long delays typical of this environment. The focus of our experiments is on analysis of the bundle flow from a Mars lander to an Earth control center through an intermediate relay node, for which two configurations are considered, inspired to Odyssey and Mars Reconnaissance Orbiter missions, respectively. Results are obtained by means of a test bed consisting of some GNU/Linux personal computers running either Interplanetary Overlay Network (ION) or DTN2 BP implementations. The analysis of results aims to highlight the role played by BP and LTP in tackling the challenges of Mars to Earth communications. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Summary: An Adhoc network is a combination of mobile nodes that works without centralized infrastructure. Every mobile node acts as host and routers. Furthermore, it also forward packets to other mobile nodes in network which are not within the direct transmission range. Mobile Ad hoc networks are easily exposed to various network layer attacks that include black hole, wormhole, and DOS attack. Wormhole attack is one among the severe attacks in MANET. Wormhole attacker receives the packets at any particular location in the network and disturbs the flow of packet by tunneling them to another location. In this paper, advanced mechanism is presented against these wormhole attacks in a MANET. Existing methods use Quality of Service (QoS) for entire network to detect attacks. Our method makes use of the packet delivery ratio and round trip time for each node, and it also detects active and passive attacks. Thus, the complete identification of wormhole attack is possible using the proposed method. [ABSTRACT FROM AUTHOR]

Opportunistic network applications are usually assumed to work only with unordered immutable messages, like photos, videos, or music files, while applications that depend on ordered or mutable messages, like chat or shared contents editing applications, are ignored. In this paper, we examine how total ordering can be achieved in an opportunistic network. By leveraging on existing dissemination and causal order algorithms, we propose a commutative replicated data type algorithm on the basis of Logoot for achieving total order without using tombstones in opportunistic networks where message delivery is not guaranteed by the routing layer. Our algorithm is designed to use the nature of the opportunistic network to reduce the metadata size compared to the original Logoot, and even to achieve in some cases higher hit rates compared to the dissemination algorithms when no order is enforced. Finally, we present the results of the experiments for the new algorithm by using an opportunistic network emulator, mobility traces, and Wikipedia pages. [ABSTRACT FROM AUTHOR]

The Delay Tolerant Network (DTN) is a novel Wireless Sensor Network architecture for an opportunistic network environment, in which environment end-to-end connection cannot be set up constantly between source and destination nodes pairs. In this paper, we have proposed a novel routing algorithm based on a hybrid of message delivery probability and message redundancy to reduce the communication overhead while keeping the high message delivery ratio. In this algorithm, the message delivery probability is calculated by the combined impact of meeting frequency and length of contact duration. Further, the maximum number of copies of the message is designated in the source node, and the forwarding task of message copies is assigned to relay nodes based on the pattern of a binary tree, so that multi-path parallel transmission can be implemented on message forwarding. Simulated results showed that the proposed routing algorithm can achieve a higher efficiency of message delivery than the related existing routing algorithms and it can also reduce the communication overhead significantly in general DTNs. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Summary: Delay tolerant networks are a class of ad hoc networks that enable data delivery even in the absence of end‐to‐end connectivity between nodes, which is the basic assumption for routing in ad hoc networks. Nodes in these networks work on store‐carry and forward paradigm. In addition, such networks make use of message replication as a strategy to increase the possibility of messages reaching their destination. As contact opportunities are usually of short duration, it is important to prioritize scheduling of messages. Message replication may also lead to buffer congestion. Hence, buffer management is an important issue that greatly affects the performance of routing protocols in delay tolerant networks. In this paper, Spray and Wait routing protocol, which is a popular controlled replication‐based protocol for delay tolerant networks, has been enhanced using a new fuzzy‐based buffer management strategy Enhanced Fuzzy Spray and Wait Routing, with the aim to achieve increased delivery ratio and reduced overhead ratio. It aggregates three important message properties namely number of replicas of a message, its size, and remaining time‐to‐live, using fuzzy logic to determine the message priority, which denotes its importance with respect to other messages stored in a node's buffer. It then intelligently selects messages to schedule when a contact opportunity occurs. Because determination of number of replicas of a message in the network is a difficult task, a new method for estimation of the same has been proposed. Simulation results show improved performance of enhanced fuzzy spray and wait routing in terms of delivery ratio and resource consumption. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Running computationally demanding real-time applications at the mobile user equipment (UE) is complicated because of limited battery life time of the UEs. One solution is to offload demanding computing tasks to a centralized cloud. Nevertheless, this option introduces significant delay consisting in delivery of the offloaded tasks to the cloud and back. Such delay is inconvenient for real-time applications. To cope with high delay, a concept of mobile edge computing has been introduced. The feasible way enabling mobile edge computing is to enhance the small cell base stations (SCeNBs) with computing capabilities. However, a high density of the SCeNBs together with even low mobility of users can result in often outage situation or handover when delay sensitive data cannot be delivered from the computing SCeNBs in time and become irrelevant. In this paper, we propose distributed cloud-aware power control algorithm, which targets to increase the ratio of delivery of computation results to the UE within required delay. Then, we enhance cloud-aware power control by adaptive algorithm. This algorithm exploits iterative process to find appropriate time when the power control is triggered in order to further improve the performance of the cloud-aware power control. The simulations demonstrate notable increase in the ratio of delivered offloaded tasks from the computing SCeNBs comparing with competitive schemes. At the same time, the amount of served data to the users exploiting common, non-cloud, services is increased. As the proposed solution is distributed, related signaling overhead is negligible. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In conventional delay-locked loop circuits, the charge and discharge of the charge pump result in mismatched current reflecting the size of the static phase error. The static phase error between feedback clock and reference clock is likely to be within tens or hundreds of picoseconds (ps). We thus propose an approach using digital calibration methods to reduce the charge pump current mismatch by means of the setup time of the D-type flip flop. The setup time of D-type flip flop is determined and duplicated to detect the phase error between the reference clock and feedback clock. It results in a very small static phase error between the reference clock and feedback clock. This paper used a 0.18 µm CMOS process design, with a reference frequency of 700 ~ 900 MHz. The active area is 0.031 mm2, and the phase error after correction is less than 5 ps. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Wireless sensor nodes are mainly deployed to focus the coverage and connectivity between the sensor nodes. Generally, nodes coverage range is fixed, sometimes which are placed in more distance cause out of coverage range from sender node to destination node. The network does not have any path analyzer node. This drawback is overcome by the proposed research work. After analyzing the number of packet drops during the transmission, the network identifies the out of coverage range among sensor node. It reduces packet delivery ratio and network connectivity ratio. Therefore, the proposed enhanced connectivity for nodes to measure coverage range (ECCR) is used to provide better coverage–based communication among sensor nodes. Affected routing path is detected initially since alert message packet is forwarded from the source node to the destination node. Anchor node–based path monitoring algorithm is constructed to monitor abnormal activities of each sensor nodes which are placed in the network environment. The abnormal activities indicate the more packet drop during communication since its coverage range goes out of limit. It increases the connectivity ratio and packet delivery ratio. [ABSTRACT FROM AUTHOR]

Message replication is often used to improve the delivery ratio in delay-tolerant networks because of the short-lived wireless connectivity environment. However, packet replication may easily incur large resource consumption and finally result in network congestion. This paper proposes a probabilistic packet acceptance and drop algorithm (PAD), which adaptively controls congestion for delay-tolerant networks. In PAD algorithm, the queue length and the input/output rate are combined to detect congestion. Based on the congestion state, each node determines the probability of accepting or dropping packets to obtain a good trade-off between high delivery ratio and low overhead. Furthermore, based on the birth-death model, we construct the continuous-time Markov chain to analyze the delivery ratio of a packet. Theory analysis and simulation results show that PAD increases the delivery ratio by more than 130% with least overhead. Meanwhile, it also achieves the shortest average end-to-end delay when the buffer of a node is severely limited. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this study, the authors present an energy-efficient technique for the fog-networks, where a node can communicate to other users using limited network infrastructure support. The authors' contribution is central to node mobility and lower energy consumption rates. They propose an energy-efficient cellular communication model for fog-networks. To establish the connection between the source and the destination node, the next generation involves node base station imports required information from nearby fog nodes and performs the network management with the help of data analytic units. A system-level optimisation for the energy consumption model is also proposed, which supports a high degree of node mobility. They compared their results with 4G/LTE and observed that the proposed work provides the least energy consumption as compared to the legacy of the networks. [ABSTRACT FROM AUTHOR]

ABSTRACT As stable end-to-end paths seldom exist in vehicular delay-tolerant networks, replication-based opportunistic routing protocols are often utilised to improve the data delivery ratio and decrease the transfer delay. However, the network load increases heavily because of numerous data replicas. In this paper, we propose a knowledge-based replica deletion Scheme using Directional Anti-packets (SuDAs), in order to reduce the transmission of anti-packets by considering vehicle contact statistics. We firstly use the contact judgment algorithm to avoid invalid anti-packet transmissions and select better forwarder for the anti-packets to reach each relay node, which has redundant data replica. Then, in the directional anti-packet transmission algorithm, we set different anti-packet transmission thresholds according to different requirements for the quality of replica deletion in the network. Formal validations and extensive simulations evaluate the performance of our scheme, which show that SuDA has a distinct advantage over others in striking a balance between the replica deletion delay and the anti-packet overhead. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY Delay tolerant networking (DTN) is an emerging technology introduced for deep-space communications to address both very large propagation delay or link disruptions. The DTN paradigm results promising in several satellite-based scenarios where either physical or service interruption might be experienced. This paper focuses on a set of selected satellite-based scenarios, where the DTN paradigm adoption greatly improves the unicast and multicast communications' performance with limited costs in terms of both software add-ons and architectural modifications. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT Because of the dynamic nature of delay tolerant networks (DTNs), many replication-based routing schemes were proposed to increase the probability of delivery by making multiple copies of each message. In such schemes, one concern is how many replicas of a message should be distributed in the network. In this paper, we propose a routing scheme for DTNs, called adaptive spraying based on the intercontact time (ASBIT). The scheme is based on the idea of that each node dynamically chooses the right number of message copies disseminated to respond to the current conditions of the network. When forwarding, ASBIT selects the node with a higher centrality as the next hop, and utilises the multi-attribute decision making theory for the division of the replication number between two nodes. Simulation results show that ASBIT achieves comparable delivery ratio and delivery delay while maintaining lower overhead compared with some well-known routing schemes in sparse scenarios. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Delay tolerant networks (DTNs) refer to a kind of novel wireless mobile network, where there is no constant end‐to‐end connection between network nodes due to frequent movement, sparse distribution and limited communication range of nodes. Instead of the traditional store‐forward routing strategy, in DTNs, the new store‐carry‐forward routing strategy is adopted for data transmission. Therefore, how to select the best next‐hop node among network nodes is the main challenge of the routing in DTNs. To this end, here, a k‐step double Q‐learning routing (K‐DQLR) algorithm is proposed, which integrates the multi‐step and double Q‐learning algorithms to make an unbiased, accurate and efficient routing decision in DTNs. Besides, a new dynamic reward mechanism is proposed, which combines the number of routing hops and the node centrality to adopt the dynamic network environment of DTNs. The simulation results show that K‐DQLR can significantly increase the delivery ratio while reducing the delivery delay and overhead compared with the related state‐of‐the‐art routing protocols of DTNs. [ABSTRACT FROM AUTHOR]

This paper studies the synchronization problem for multiagent systems with identical continuous- or discrete-time agents with unknown nonuniform constant input delays. The agents are connected via full- or partial-state coupling. The agents are assumed to be asymptotically null controllable, ie, all eigenvalues are in the closed left-half complex plane for continuous-time agents or in the closed unit disc for discrete-time agents. We derive an upper bound for the input delay tolerance, which explicitly depends on the agent dynamics. Moreover, for any unknown delay satisfying this upper bound, a low-gain-based protocol design methodology is proposed without relying on exact knowledge of the network topology such that synchronization is achieved among agents for any network graph in a given set. [ABSTRACT FROM AUTHOR]

Summary: Delay‐tolerant networking (DTN) bundle protocol is considered one of the best transmission protocols to be used in space communications by NASA. There are studies that evaluated the performance, measuring the total transfer time of a complete file from sender to receiver, of the DTN protocol via simulation or emulated experiments beyond the real space‐based experiences. In addition, there is a very few additional research works available for the modeling of the Licklider transmission protocol (LTP). However, these past studies on LTP modeling are implemented as a Logarithmic approach that is based on the calculation of loss segments in file delivery. In this work, the approach is investigated in a different manner. Specifically, the performance model was created based on the probability of the segment's successful delivery on the LTP. Moreover, the original model is enhanced via introducing a burst of transfer and equal interval distribution of signaling segments, specifically check point (CP), along with the retransmission time out (RTO). The results from the developed model for the original DTN protocol and enhanced versions align with the results obtained by PC‐based testbeds. [ABSTRACT FROM AUTHOR]

Summary: Delay/disruption tolerant networks (DTNs) are potentially applicable in the challenged scenarios like post‐disaster environments. In such networks, data forwarding generally relies on the mutual cooperation of the nodes. However, in reality, despite the availability of necessary resources for data forwarding, a node could misbehave by dropping messages received from other nodes with whom it has no strong social ties. Such a node is called a socially selfish node, which would cause a poor delivery ratio in the network. In this paper, we aim to address the problem of multicast data forwarding in the presence of such selfish nodes, by means of efficient relay selection in DTNs. First, we define a realistic reputation model, in contrast to existing models, to define the socially selfish/misbehaving nodes in the network. Further, a game‐theoretic analysis is carried out that implies data forwarding cost is also an influential parameter in handling selfishness/misbehavior. Subsequently, the problem is formulated as a constrained optimization problem, which is NP hard. Therefore, a heuristic is proposed by combining the reputation of a node and the cost of message forwarding to appropriately identify relay nodes, thus improve the performance of the multicast message delivery in the network. We utilize a social metric, centrality to minimize the message forwarding cost in terms of the number of relay nodes. Finally, the comparative performance evaluation in ONE simulator with practical scenarios shows the superiority of the proposed scheme over the other prominent schemes. [ABSTRACT FROM AUTHOR]

Summary: Wireless networks are now very essential part for modern ubiquitous communication systems. The design of efficient routing and scheduling techniques for such networks have gained importance to ensure reliable communication. Most of the currently proposed geographic routing protocols are designed for 2D spatial distribution of user nodes, although in many practical scenarios user nodes may be deployed in 3D space also. In this paper, we propose 3D routing protocols for multihop wireless networks that may be implemented in two different ways depending on how the routing paths are computed. When the routing paths to different user nodes from the base station in the wireless network are computed by the base station, we call it centralized protocol (3DMA‐CS). A distributed routing (3DMA‐DS) protocol is implemented when respective routing path of each user node to the base station is computed by the user node. In both of these protocols, the user (base station) selects the relay node to forward packets in the direction of destination, from the set of its neighbours, which makes minimum angle with the reference line drawn from user (base station) to the base station (user), within its transmission range. The proposed protocols are free from looping problem and can solve the void node problem (VNP) of multihop wireless networks. Performance analysis of the proposed protocol is shown by calculating end‐to‐end throughput, average path length, end‐to‐end delay, and energy consumption of each routing path through extensive simulation under different network densities and transmission ranges. [ABSTRACT FROM AUTHOR]

Summary: Disruption‐tolerant network (DTN) implementation is subject to many routing constraints like limited knowledge of the network and intermittent connections with no end‐to‐end path existence. In this paper, the researchers propose trusted‐cluster–based routing protocol (TCR) for routing in DTN. TCR uses the experiential learning model that integrates neural network‐based bipolar sigmoid activation function to form trusted‐cluster DTN. TCR works in two phases: firstly to form a trusted‐cluster and secondly to identify cluster heads to direct network traffic through them. After the formation of the trusted‐cluster, a cluster head is chosen for a set period, thus instigating stability in the network. These trust values are attached to the node's route cache to make competitive routing decisions by relaying a message to the other trusted intermediate nodes only. With negative trust value, any node is deprived of participation in the network. This way, TCR eliminates malicious or selfish nodes to participate in the DTN network and minimizes the number of messages forwarded in a densely populated DTN. Also, this implementation conserves sufficient buffer memory to reach the destined node. The TCR's performance with other DTN routing schemes, namely, epidemic and trust‐based routing, is compared using multiple simulations runs. The proposed work is verified using mobility traces from Community Resource for Archiving Wireless Data At Dartmouth, and the experimental result shows the elimination of selfish nodes participating in the DTN. The simulation result shows an increase of 19% in message delivery by forwarding only to a trusted intermediate node possible. [ABSTRACT FROM AUTHOR]