Search

There is no universally accepted definition of a green building. Generally, it refers to an ideal living environment created with respect for ecological principles and environmental considerations, combined with the principle of ecological design. Green buildings not only improve living conditions and energy efficiency but also contribute to urban air quality, enhance landscapes, and positively impact the physiological and psychological well-being of individuals. To achieve the goals of green building, it is imperative to have convenient and accurate selection of plant materials, create a sustainable green system, and establish a comprehensive green building plant resource information system. Over the past few decades, numerous quantitative studies on the ecological functions of green plants have been conducted worldwide. Various test methods have been employed under different green conditions to quantify these functions and obtain numerous quantitative values. Concepts such as green area, green coverage, leaf area index, leaf area, green rate, vertical green coverage area, and overall green quantity have been introduced. Delay Tolerant Network (DTN) engineering faces challenges in ensuring end-to-end availability in cloud computing. Consequently, transporting data over such networks is challenging since most Internet applications rely on persistent end-to-end connections. Since the standardization of the DTN architecture, significant research has been dedicated to developing routing protocols for various mobility scenarios, aiming to improve segment delay, delivery, and data delivery ratios.

Opportunistic networks (OppNet) a new paradigm emerges after the great advancement of wireless technology and MANETs (Mobile Ad-hoc Networks). Store-Carry-forward phenomena is used to route the messages in OppNets; therefore, it is called delay tolerant network (DTNs). OppNet is such a heterogeneous flexible network that works in hurricane affected regions and volcanoes environment. The objective of this article is to determine, evaluate, elect and synthesize all terrific quality research work on the basis of Research Questions (RQ) which is significant to use for opportunistic routing. Systematic literature review on state-of-the-art researches on routing protocols are presented with comparative analysis. To eliciting relevant work for review, advanced exploration is conducted on contrasting digital libraries. This work gives the opportunity to the readers to understand what has been done in field of Opportunistic Routing (OR), what parameters effect the performance of protocol, name of the organization; who works in this field. At last, issues, challenges, and upcoming future terms of this network are discussed.

Vehicular Ad Hoc Networks (VANETs) are increasingly playing a fundamental role in improving driving safety. However, VANETs in a sparse environment may add risk to driving safety. The probability of a low density of vehicles in a rural area at midnight is very high. Consequently, the packet will be lost due to the lack of other vehicles, and the arrival of the following vehicles in the accident area is unavoidable. To overcome this problem, VANET is integrated with Wireless Sensor Network (WSN). The most challenging features of VANETs are their high mobility. This high mobility causes sensor nodes to consume most of their energy during communication with other nodes, leading to frequent network disconnectivity. With the evolution of VANET and WSN, the Store/Carry-Forward (SCF) paradigm has emerged as an exciting research area in the Delay Tolerant Networks (DTNs) to solve network disconnectivity. This paper proposes the Energy-Mobility-Connectivity aware routing protocol (EMCR) for a hybrid network of VANET-WSN. A comprehensive performance analysis that considers realistic propagation models and real city scenario traffic is performed in NS3. The simulation results show that the SCF mechanism is essential in the EMCR protocol to maximize the delivery ratio and minimize energy consumption and overhead.

The paper explores data delivery delays in next-generation railway communication networks with various configurations of terrestrial and satellite coverage (including mesh and delay tolerant forwarding). It proposes a rough analytic estimation (with just two parameters: the total number of trains and the average number of their meetings) and computer simulation (based on realistic train schedules). This approach can serve as a preliminary groundwork for the technical and commercial choice of a preferred 5G railway link type on the stage of implementing: satellite (SatCom) or terrestrial (TerraNet), and assessing the feasibility of the necessary QoS.

Vehicular delay tolerant networks (VDTNs) enable information sharing among mobile nodes in scenarios where cellular base stations are unavailable and the connections between the mobile nodes are intermittent. While unmanned aerial vehicles (UAVs) have shown to improve the performance of VDTNs, existing routing protocols, such as PRoPHET, consider the encounter probability between mobile nodes only, which does not fully address the characteristics of UAVs in route selection. In this paper, we propose a routing protocol, which considers both the encounter probability and the persistent connection time between mobile nodes for each encounter, in UAV-assisted VDTNs. By introducing the persistent connection time in route selection, the proposed protocol is able to evaluate the stability of a communication link more accurately in the UAV-assisted VDTN environment. The proposed protocol is evaluated using realistic simulations by comparing it with existing baselines. The simulation results verify that the proposed protocol can improve the reliability of message forwarding while reducing network overhead and end-to-end delay.

In order to deploy a blockchain on the non-continuous connectivity delay tolerant network,a blockchain trading mechanism was designed,which could run on this type of network.First,the identifier was introduced into the existing block structure and a block structure on the attached chain was presented,which could append the blocks generated during network disconnection.Then,the approaches including the block package,block mining and block consensus on the attached chain were proposed.Finally,a confirming consensus approach was presented to avoid block fraud in the process of appending the attached chain.Through theoretical proof and experimental analysis,the proposed mechanism can support blockchain trading in the delay tolerant network.

Abstract Due to the unguaranteed connectivity, wireless sensor networks based on delay tolerant network (DTN) are typically characterized by the opportunistic forwarding mechanism in transmission. Such a mechanism requires nodes to participate in forwarding messages actively. However, when the mechanism is used in the real world, selfish nodes will exhibit some non-cooperation behaviors. Therefore, some incentive mechanism may be designed to encourage selfish nodes. In order to solve the selfishness problem, we propose a fair credit-based incentive mechanism for routing in DTN-based sensor networks. In this mechanism, when a source node sends messages to its destination, each relay node will be rewarded with some credits. The accumulated credits are then used to evaluate the level of cooperation in the network. The selfish nodes with few credits are not able to get enough service from other nodes. With the fair incentive, all participating relays will get equal rewards by the trusted third party. In order to evaluate the proposed mechanism, we also perform some simulation, and the results demonstrate that the method can be used to support efficient routing for DTN-based sensor networks.

The article is devoted to the analysis of the effectiveness of the DTN (Delay Tolerant Network) system in a communication network on a railway line. Trains act as moving objects, that are sending and receiving messages to/from an external network. As well trains may transmit telemetry, collected during movement. The article presents data on the effectiveness of the DTN network in terms of reducing the delay in message delivery, reducing the delay in transmitting telemetry, and increasing the total number of messages in the railway scenario. The data on the theoretical efficiency of the DTN system are presented, including the results of the generation of many maps of railway networks and the corresponding train schedules. An analysis of railway line sections of various load and having different coverage of mobile network was made. These models are based on real railway maps with real train schedules. Effectiveness of DTN during migration to networks of a higher data rate (5G) and networks with satellite connection of trains is analyzed.

Drones have become prevalent for the delivery of goods by many retail companies such as Amazon and Dominos. Amazon has an issued patent that describes how drones scan and collect data on their fly-overs while dropping off packages. In this context, we propose a path optimization algorithm for a drone multi-hop communications network that can carry and forward data in addition to its primary function of parcel deliveries. We argue that traditional Delay Tolerant Networking (DTN) based protocols may not be efficient for this purpose. Therefore, this paper proposes a new DTN-based algorithm that optimizes drone flight paths in conjunction with optimized routing to deliver both parcels and data in a power efficient way and within the shortest possible time. We propose a heuristic algorithm called Weighted Flight Path Planning (WFPP) that priorities the data packets in an exchange pool in order to create an optimized path for the drones. Our approach is to determine a weight for each packet based on the packet's remaining time to live, priority, size, and location of the packet's destination. When two drones meet each other, they exchange the high weighted packets. Simulation studies show that WFPP delivers up to 25% more packets compared with EBR, EPIDEMIC, and a similar path planning method. Also, WFPP reduces the data delivery delays by up to 66% while the overhead ratio is low.

The Internet of Things is one of the new emerging application domains that require delay tolerant network (DTN) support, where an end-to-end path between the source and the destination may not always exist. Due to the intermittent connectivity of DTN, the design of an efficient routing algorithm is the main challenge. In this paper, we first define a metric called message handling capacity to determine the ability of a node to forward messages. Then, we introduce a concept called connection strength to reflect the connection time between nodes and then integrate the concept into delivery predictability used by Prophet to determine the chance of a node completely delivering a message to the destination. Subsequently, we present a metric called quality of node (QoN), which is calculated by combining the relative weights of the message handling capacity and the improved delivery predictability. Finally, we present an adaptive spray and wait routing algorithm based on QoN (QoN-ASW). The QoN-ASW adaptively allocates the number of message copies between the encountered nodes according to the proportion of quality of node in the spray phase, which avoids the blindness of replica distribution. In addition, a forwarding scheme is implemented in the wait phase, which takes full advantage of encounter opportunities. In the simulation, we demonstrate the efficiency of integrating the connection strength into delivery predictability and compare the QoN-ASW with four existing DTN routing algorithms from four aspects. The simulation results show that the QoN-ASW can significantly improve the delivery rate and reduce the average delay while achieving a relatively low overhead.

Abstract 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.

The existing DTN routing algorithms tend to make data transition inflexible and have a long delay in contact.To solve those problems,an algorithm was proposed which called meeting delay expect value in spray and forward routing algorithm for DTN（MDESF）.This algorithm will use mobile node's contact history to conduct the expected average contact/disconnect time and message expected wait value（EWV）.With those attributes the MDESF will proportionally distribute replicas of a message between two nodes in multiple replicas phase.A buffer management strategy was proposed in order to improve the success rate of imformation fornarded.The simulation results illustrate that the proposed MDESF protocol outperform other existing ones.

The architecture of space delay tolerant networking can effectively support a deep space communication network with long delay,high error rate and on-off frequently link characteristics through“store-carry-forwards”and other features.Due to the experiment of application of deep space communication is not easy to carry,so building an accurate and reliable semi-physical simulation platform for simulating and making an argumentation of the design of deep space communication tasks was very necessary.A space DTN semi-physical simulation platform was proposed which supported a variety of specific deep space communication tasks simulation.The simulation platform provided new theory and technology for ground simulation and verification,and provided analysis tools and test instruments for carrying out deep space communication application study.

Large amounts of data are typically generated in applications such as surveillance of power lines and railways, inspection of gas pipes, and security surveillance. In the latter application it is a necessity that the data is transmitted to the control centre ``on-the-fly'' for analysis. Also missions related to other applications would greatly benefit from near real-time analysis and operator interaction based on captured data. This is the motivation behind this paper on coarse offline motion- and communication-planning for cooperating Unmanned Aerial Vehicles (UAVs). A Mixed-Integer Linear Programming (MILP) problem is defined in order to solve the surveillance mission. To efficiently transmit the data back to the base station the vehicles are allowed to store data for later transmission and transmit via other vehicles, in addition to direct transmission. The paths obtained by solving the optimization problem are analyzed using a realistic radio propagation path loss simulator. If the radio propagation path loss exceeds the maximum design criterion the optimization problem is solved again with a stricter communication constraint, and the procedure is continued in an iterative manner until the criterion is met. The proposed algorithm is supported by simulations showing the resulting paths and communication topologies for different choices of delay tolerance.

A mobility model detection method based on birth and death model (MMD-BDM) in DTN environment was proposed.It first computed the connected channel capacity of sampling times according to the data traffic during the data transfer process,and then constructed the time varying intercommunication metrics at local,which composed of channel capacity between local node and others.Based on these,the connection birth and death mode of nodes based on connected edges was deduced,and then the birth and death features of the connected nodes was analyzed to detect the mobility model,which used to improve the routing strategy during the packages deliver process.Ultimately,the mobility model detection method was put into use in spray and wait routing (SWR) method and random network coding routing (RNCR) method to experiment,the simulation results show that,it can improve the opportunity routing performance of the data deliver rate and transfer latency in DTN environment.

To stimulate the DTN selfish nodes to cooperatively forward messages when the buffer was limited, a congestion-aware incentive scheme based on double auction for DTN was proposed. In the scheme, nodes determined the self congestion degree according to the current free buffer and message receiving rate. Combining the message delivery probability and congestion degree, nodes traded the message based on double auction model, thereby achieved the cooperation between nodes. Extensive simulations were carried out on real-world traces to evaluate the proposed scheme. The experimental results show that, due to the congestion aware, the incentive scheme can further stimulate selfish nodes to cooperatively forward messages, improve the message delivery ratio and reduce the message delivery delay.

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

Different from conventional networks, DTN has several unique characteristics, such as node mobility, loose connectivity, and delay tolerability, etc. As mobile devices have become indispensable in daily life, there emerges a new interesting problem, which is how to take advantage of the portable and powerful facilities to share resources and information. The prevailing approach to process those queries is to use flooding methods because of their quick response and easy maintenance. However, this kind of approaches wastes a huge amount of communication bandwidth and battery power of mobile devices. To tackle this problem, an intelligence accuracy（IA） scheme was introduced to improve network query success rate. The IA scheme mimics natural behavior of human social networking features to promote efficiency of information collection. Experimental results show that the efficiency and effectiveness of the IA approach are as well as its scalability in a volatile environment.

With the dynamical features of mobility, intermittent connectivity and dynamic topology in delay tolerant net-work (DTN), the static random network coding methods become difficult to adapt to the applications in DTN environ-ment. For working out this problem, a dynamic random network coding transfer method (DRNC) was proposed. Based on the Markov channel model, it first computed the transmit speeds of every network channel according to the receive data states of nodes, and then constructed the network flow graphic with channel capacities at the source node, calculated and forecasted the current network multicast capacity, after that, the random network coding scenario was extended and tailored according to the multicast capacity to transmit data packages under DTN environment. The simulation results show that, compared with the traditional random network coding method with fixed multicast rate, the dynamic random network coding method has reduced the average latency of data packages and increased the delivery probability.

The hybrid MANET - DTN is a mobile network that enables transport of the data between groups of the disconnected mobile nodes. The network provides benefits of the Mobile Ad-Hoc Networks (MANET) and Delay Tolerant Network (DTN). The main problem of the MANET occurs if the communication path is broken or disconnected for some short time period. On the other side, DTN allows sending data in the disconnected environment with respect to higher tolerance to delay. Hybrid MANET - DTN provides optimal solution for emergency situation in order to transport information. Moreover, the security is the critical factor because the data are transported by mobile devices. In this paper, we investigate the issue of secure candidate node selection for transportation of the data in a disconnected environment for hybrid MANET- DTN. To achieve the secure selection of the reliable mobile nodes, the trust algorithm is introduced. The algorithm enables select reliable nodes based on collecting routing information. This algorithm is implemented to the simulator OPNET modeler.

Internet of Things (IoT) is witnessing an increasing range of application domains (industry 4.0, eHealth, smart city, etc.). Meanwhile, IoT is still facing communication challenges because of limited capabilities in computing, storage and energy constraints of smart objects. The use of Delay Tolerant Network (DTN) as basis for communication in IoT is promising but needs more development. In this paper, we present a literature review and a classification of DTN routing protocols. Furthermore, we survey a number of DTN solutions for IoT and propose a new taxonomy to motivate the importance of enabling DTN for IoT applications. The novelty of this classification is the focus on X-DTN category, which combines Delay Tolerant schemes with new technologies (e.g., Fog Computing). We also point out some open issues for potential Delay Tolerant IoT schemes.

One of the main challenges of operating a smart city (SC) is collecting the massive data generated from multiple data sources (DSs) and transmitting them to the control units (CUs) for further data processing and analysis. These ever-increasing data demands require not only more and more capacity of the transmission channels but also results in resource over-provision to meet the resilience requirements, thus the unavoidable waste as a result of the data fluctuations throughout the day. In addition, the high energy consumption (EC) and carbon discharge from these data transmissions posing serious issues to the environment we live in. Therefore, to overcome the issues of intensive EC and carbon emission (CE) of massive data dissemination in SCs, we propose an energy-efficient and carbon reduction approach by using the daily mobility of the existing vehicles as an alternative communications channel to accommodate the data dissemination in SCs. To illustrate the effectiveness and efficiency of our approach, we take the Auckland City in New Zealand as an example, assuming massive data generated by various sources geographically scattered throughout the Auckland region, to the control centres located in the city. Results obtained show that our proposed approach can provide up to four times faster transferring the large volume of data by using the existing daily vehicles’ mobility, than the conventional transmission network. Moreover, our proposed approach offers about 32% less EC and CE than that of conventional network transmission approach.

Many applications of Internet of Things (IoT) have been implemented based on unreliable wireless or mobile networks like the delay tolerant network (DTN). Therefore, it is an important issue for IoT applications to achieve efficient data transmission in DTN. In order to improve delivery rate and optimize delivery delay with low overhead in DTN for IoT applications, we propose a new routing protocol, called Scheduling-Probabilistic Routing Protocol using History of Encounters and Transitivity (PROPHET). In this protocol, we calculate the delivery predictability according to the encountering frequency among nodes. Two scheduling mechanisms are proposed to extend the traditional PROPHET protocol and improve performance in both storage and transmission in DTN. In order to evaluate the proposed routing protocol, we perform simulations and compare it with other routing protocols in an Opportunistic Network Environment (ONE) simulator. The results demonstrate that the proposed Scheduling-PROPHET can achieve better performances in several key aspects compared with the existing protocols.

The Intermittently Connected Mobile Networks (ICMN) is a disconnected mobile network where a complete connectivity never exists. The intermittent connectivity is due to the dense nature of the network. The dense nature is mainly due to the high mobility of the nodes in the network. Routing in such a sparse network is arduous. Due to the disconnected attribute of the network, the encounter of the suspicious nodes in the network also remains a tedious task. In this paper, we put forward a secure routing that aids in detecting and preventing intrusion of malicious nodes. The routing process is made adorable through Spray and Wait (SNW). Since ICMN is prompt to higher delays certain authentication series are used to enable secure communication within the network. The amalgamation of SNW with authentication series leads a novel routing protocol named S-Spray (Secured-Spray) which is highly secure.

To cope with un-ideal conditions in mobile network where connectivity is only intermittent,a novel DTN (delay tolerant network) routing protocol,IEDR,was proposed,which incorporates experiences gained before and strives to fully utilize node contacts for data exchange,in order to maximize delivery ratio and minimize delivery delay,while still with controlled overhead.Additionally,IEDR attempted to use wireless access points for data propagation,as access points were supposed to be widely deployed and interconnected with high speed,providing an opportunity to efficiently distribute data in large areas.The evaluation proves that IEDR is better than many classic DTN routing protocols.

Worms spreading directly between cell-phones over short-range radio (Bluetooth, WiFi, etc.) are increasing rapidly. Communication by these technologies is opportunistic and has very close relation with the social characteristics of the phone carriers. In this paper, we try to evaluate the impact of different characteristics on the spreading performance of worms. On the other hand, the behaviors of worms may have certain impact, too. For example, worms may make phones be completely dysfunctional and these phones can be seen as killed. We study the impact of the killing speed. Using the Markov model, we propose some theoretical models to evaluate the spreading performance in different cases. Simulation results show the accuracy of our models. Numerical results show that if users do not believe the data coming from others easily, the worms may bring less damage. Surprisingly, if the users are more willing to install the anti-virus software, the worms may bring bigger damage when the software becomes to be outdated with high probability. Though the worms can bring big damage on the network temporarily by killing phones rapidly, numerical results show that this behavior may decrease the total damage in the long time. Therefore, killing nodes more rapidly may be not optimal for worms.

The Smart City concept is starting to extend into maritime environments alongside with the increase of Unmanned Surface Vehicles (USV) models on the market. Consequently, by joining both Smart City and USV technologies, a set of platforms and applications for aquatic environments are emerging. This work proposes a low-cost aquatic mobile sensing platform for data gathering with a swarm of USVs communicating through a Delay-Tolerant Network (DTN). A set of DTN link quality-based routing strategies select the best quality path in a dynamic approach so the sensed information is able to reach the mobile gateway in a reliable way. A Link Quality Estimation (LQE) approach is proposed and its accuracy is evaluated through real experimentation. An aquatic simulation environment, considering both navigation and communication layers, was also proposed and used to evaluate the performance of the proposed routing strategies, and complement real environment performance studies.

In order to get the real-time mobility model information which could be exploited to assist routing decision,a framework for mobility model detection based on local information（FMDL） was proposed.In FMDL,each node collected the local information on connectivity through neighbor discovery mechanism and generated the connectivity matrix.The changing rule of relative position could be extracted from the connectivity matrix,and then the real-time mobility model was detected.The simulation results show that FMDL achieves high detection rate without any auxiliary equipment.

Delay Tolerant Networking (DTN) is well suited to challenging environments, defined by the lack of reliable end-to-end communication paths to the destination. However, the available energy is not considered in the majority of existing DTN routing protocols when they make forwarding decisions. This limits both delivery probabilities and the network lifetimes in energy-constrained applications. This paper investigates energy-aware routing protocols for wildlife tracking application to transmit data from attached sensors on the animal’s back to data collection base stations. We propose three new network protocol strategies to extend common DTN routing protocols, and consider the available energy to achieve efficient utilization of the node’s energy in transmission and sensing. These strategies enhance packet delivery rates up to 13% by carefully using the limited energy resources. We simulate two different animal tracking scenarios and show that the new strategies provide significant performance improvement under different scenarios.