Delay Tolerant Networks Research Articles

Effective communication for message prioritization in DTN for disaster scenarios

When disaster strikes, effective communication is crucial for emergency responses and accessing a victim’s location. Using smartphone-based Delay Tolerant Networks (DTNs) is the prevalent proposed approach to work around network disruptions. One of the challenges in these networks is high-traffic congestion since buffer limitation produces messages that get dropped before they are delivered. This article presents a congestion control strategy using message prioritization for DTNs to increase network resilience facing high message congestion. We measure congestion by considering the free space in the buffer of the nodes involved in the routing or by counting the messages deleted from the buffer in a fixed period to improve the availability and immediacy of information for disaster scenarios. We evaluated the proposed strategies using The ONE simulator to test different mobility models and communication protocols. Results show that the strategy improved delivery rate, buffer usage, eliminated messages, overhead, and latency for the highest priority messages. The best results were obtained in terms of latency, which fits our disaster scenario since timely information is vital. The trade-offs are a slightly lower average delivery rate and a decrease in the lowest priority message delivery rate.

A DTN oriented adaptive routing algorithm based on node load

In recent years, Delay Tolerant Networks (DTN) have received more and more attention. At the same time, several existing DTN routing algorithms generally have disadvantages such as poor scalability and inability to perceive changes in the network environment. This paper proposes an AdaptiveSpray routing algorithm. The algorithm can dynamically control the initial maximum message copy number according to the cache occupancy rate of the node itself, and the cache occupancy rate is added as an impact factor to the calculation of the probability of each node meeting the destination node. In the forwarding phase, the node will first compare the meeting probability of itself and the meeting node to the destination node, and then choose different forwarding strategies. The simulation shows that the AdaptiveSpray algorithm proposed in this paper has obvious advantages compared with the existing routing algorithms in terms of message delivery rate and average delay.

A Delay-Tolerant Network for Antarctica

Antarctica is the land of science. Every year, many studies are carried out in diverse disciplines. Some of these studies collect relevant data for their research with sensors. However, Antarctica's lack of telecommunication technologies hardens the possibility of automatizing this data collection. In most cases, the collection is done manually, limiting research projects' time and space scopes. Over the last years, some alternatives have been studied to deploy remote wireless sensor networks in Antarctica. Near-Vertical Incidence Skywave (NVIS) communications are an example of these alternatives. However, NVIS presents problems that cannot guarantee persistent end-to-end connectivity. For this reason, this article assesses adapting a delay-tolerant network protocol, the Bundle Protocol, to deliver sensor data reliably through an NVIS network. The scenario is developed and tested in the Riverbed Modeler simulator, and performance is evaluated through a trustworthiness model. A practical testbed is also presented.

Effects of preoperative Staphylococcus aureus screening and targeted decolonization bundle protocols in cardiac surgery: a nine-year review of a regional cardiovascular center in China.

Nosocomial infection (NI) prolongs hospital stay and heightens mortality among patients who underwent cardiac surgery. We constructed a retrospective study to explore the prevalence of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (SA/MRSA) nasal colonization, as well as the effects of SA/MRSA decolonization bundle measures on SA/MRSA-related infection among Chinese cardiac patients. After reviewing the medical records, we divided cardiovascular surgery patients treated at our central campus into two groups: the baseline group (treated between January 2012 and December 2013) and the intervention group (treated between May 2014 and December 2020). Intervention measures consisted of preoperative nasal screening and targeted decolonization bundle therapy. The medical records of patients at our southern campus (treated between January 2017 and December 2020) were collected as an additional control group, since we did not implement SA intervention measures at this location. The incidences of SA/MRSA-related NI were then compared between the groups. There were 794 patients in the baseline group and 2,826 in the intervention group. A total of 131 (4.6%) patients had SA nasal colonization, and among them, 33 patients (1.2%) were MRSA colonized. SA/MRSA was cleared in approximately 95% of the carriers. The total level of SA-related infection was significantly lower in the intervention group compared to the baseline group [0.354% vs. 1.133%, respectively; P=0.021; risk ratio (RR): 0.312; 95% confidence interval (CI): 0.127-0.766]. The incidence of MRSA-related infection followed the same trend (0.212% vs. 0.756%, respectively; P=0.030; RR: 0.281; 95% CI: 0.091-0.860). When compared to the southern campus, SA intervention measures at the central campus resulted in a significant reduction in total SA-related infection (1.132% vs. 0.284%, respectively; P=0.035; RR: 0.251; 95% CI: 0.077-0.820). The prevalence of SA/MRSA colonization is relatively low among Chinese patients who received cardiovascular surgery. Targeted decolonization bundle therapy was associated with cleared colonization and reduced incidence of SA/MRSA-related infection.

Effect of Skincare Bundle Protocol on Nursing Performance Regarding Prevention of Skin Breakdown

Effect of Skincare Bundle Protocol on Nursing Performance Regarding Prevention of Skin Breakdown

Adaptive Data Dissemination Algorithm Based on Storing-Discarding Equilibrium for OUSNs

Opportunistic underwater sensor networks (OUSNs) are deployed for various underwater applications, such as underwater creatures tracking and tactical surveillance. The data dissemination in OUSNs differs significantly from those in terrestrial wireless sensor networks or delay-tolerant networks, due to the signal irregularity in underwater communications and the limited storage capacity of the nodes in OUSNs. To alleviate the storage overflows on nodes and make room for the newly arriving data packets, some stored data packets ought to be actively discarded by nodes. This research begins with the construction of a differential equation set to describe the propagation process of data packets in OUSNs, and the storing-discarding equilibrium is investigated such that each data packet is expected to propagate and disappear during the allowable dissemination time slots. After that, the optimal storing probabilities and discarding probabilities are obtained for the nodes with different in-degrees to maximize the delivery ratio of data packets. Then, we propose an Adaptive Data Dissemination Algorithm (ADDA) for the storage-limited OUSNs with signal irregularity, where at each time slot the newly arriving data packets are stored and the stored data packets are discarded by nodes according to the obtained storing probabilities and discarding probabilities, respectively. Simulation results demonstrate the excellent performance of ADDA, showing that it can enhance the delivery ratio of data packets and reduce the number of storage overflows.

Voronoi-Based UAV Flight Method for Non-Uniform User Distribution in Delay-Tolerant Aerial Networks

This paper considers an emergency communication system controlling multiple unmanned aerial vehicles (UAVs) in the sky over a large-scale disaster-affected area. This system is based on delay-tolerant networking, and information from ground users is relayed by the UAVs through wireless transmission and the movement of UAVs in a store-and-forward manner. Each UAV moves autonomously according to a predetermined flight method, which uses the positions of other UAVs through communication. In this paper, we propose a new method for UAV flight considering the non-uniformity of user distributions. The method is based on the Voronoi cell using the predicted locations of other UAVs. We evaluate the performance of the proposed method through computer simulations with a non-uniform user distribution generated by a general cluster point process. The simulation results demonstrate the effectiveness of the proposed method.

Development of an evidence-based care bundle protocol for preventing falls in hospitalized children: Delphi study and trial test.

The aim of the study was to develop an evidence-based care bundle protocol for preventing falls in hospitalized children. Delphi method. Based on the four basic concepts of nursing, the theoretical dimension and item pool of the care bundle first draft were constructed by searching evidence and referring to the care bundle for preventing inpatient fall issues by the China Nursing Quality Promotion Alliance. The Delphi method and trial tests were used to select and adjust items of the care bundle to form the care bundle protocol for preventing falls in hospitalized children. The first draft care bundle for preventing falls in hospitalized children included 4 dimensions and 21 items. In the 2-round Delphi study, one item was removed, and three items were adjusted. One item was adjusted by trial test. Finally, the care bundle protocol for preventing falls in hospitalized children consisted of 4 dimensions and 20 items.

Non-Terrestrial Networks with UAVs: A Projection on Flying Ad-Hoc Networks

Non-terrestrial networks (NTNs) have recently attracted elevated levels of interest in large-scale and ever-growing wireless communication networks through the utilization of flying objects, e.g., satellites and unmanned aerial vehicles/drones (UAVs). Interestingly, the applications of UAV-assisted networks are rapidly becoming an integral part of future communication services. This paper first overviews the key components of NTN while highlighting the significance of emerging UAV networks where for example, a group of UAVs can be used as nodes to exchange data packets and form a flying ad hoc network (FANET). In addition, both existing and emerging applications of the FANET are explored. Next, it provides key recent findings and the state-of-the-art of FANETs while examining various routing protocols based on cross-layer modeling. Moreover, a modeling perspective of FANETs is provided considering delay-tolerant networks (DTN) because of the intermittent nature of connectivity in low-density FANETs, where each node (or UAV) can perform store-carry-and-forward (SCF) operations. Indeed, we provide a case study of a UAV network as a DTN, referred to as DTN-assisted FANET. Furthermore, applications of machine learning (ML) in FANET are discussed. This paper ultimately foresees future research paths and problems for allowing FANET in forthcoming wireless communication networks.

Improving the delivery ratio in vehicular delay‐tolerant network using customized binary particle swarm optimization‐based optimized throwbox deployment

SummaryVehicular delay tolerant networks (VDTNs) suffer due to insufficient connection opportunities in sparse infrastructure. The sparsity of the network results in poor delivery ratio (DR). Deployment of additional small nodes named throwbox increases the contact opportunities, resulting in improved performance in terms of DR. However, randomly deployed throwboxes do not provide optimum results. Therefore, this article proposes the throwbox deployment as an optimization problem. Customized binary particle swarm optimization‐based optimization method is employed to solve the problem. With the objective of maximizing the DR, the method optimize the placement of ‐throwboxes in the network. The performance of the proposed methods is tested and compared by simulating a VDTN model in opportunistic network environment simulator. The optimization framework was implemented in Matlab. Exhaustive experiments were carried out by varying the number of throwboxes (). A statistical comparison of the results with the existing throwbox deployment methods validates the effectiveness of the proposed optimization‐based approach. The article also presents an analysis for choice of value of for a desired network performance.

PROTOTYPE OF A DESKTOP-BASED COMMUNICATION APPLICATION USING A DELAY TOLERANT NETWORK ARCHITECTURE

Currently, the process of exchanging information or data is carried out quickly, precisely, effectively and efficiently using the internet network. However, in reality, there are still some problems in areas that are difficult to get a signal, such as connection loss or unstable connection. One of the proposed solutions to anticipate this problem is the implementation of a network using the Delay Tolerant Network architecture. This architecture was chosen because of its basic capability, namely being able to send files even in a high delay state or used in areas with intermittent properties. The implementation carried out is making a chat application prototype that is able to function in intermittent areas and can be used for communication between sender and receiver in difficult signal conditions. The hardware used is a raspberry pi and supporting software using ION-DTN and traffic management designed using the python programming language. The application is tested by applying the concept of functionality testing, namely with full signal condition scenarios and limited signal conditions as a representation of the intermittent area. The test results show that the application is able to function based on the initial design with a delay with test variations of 1-10 minutes of signal dropout time. Further development can be done by adding a chat feature so that it is able to send more varied data.

Analysis of health informatics and bioinformatics connectivity modeling

Health informatics and bioinformatics are closely linked, but the overlapping literature search rate of the analysis methods is low due to the connectivity analysis model. Therefore, a health informatics and bioinformatics connectivity modeling analysis based on a delay-tolerant network routing algorithm is proposed. The analysis is conducted for the topics of both health informatics and bioinformatics disciplines, and a reasonable design of citation measures is designed. The first step in describing the connection between the two disciplines using citation analysis is to extract multidimensional descriptive vectors for the disciplines as a basis for connectivity analysis. The connectivity analysis model is designed with the core of the tolerance network routing algorithm to determine the connectivity of disciplines by detecting the citation overlap between two disciplines. Finally, the connectivity is described by outputting the co-occurrence knowledge structure between disciplines through co-occurrence analysis. The experimental results show that the proposed method improves the completeness rate by 36.6% and 39.2% compared with the conventional connectivity modeling analysis method, which indicates that the proposed method reveals more comprehensive connectivity analysis results.

EE-MSWSN: Energy-Efficient Mobile Sink Scheduling in Wireless Sensor Networks

Data gathering using mobile sink (MS) based on rendezvous points (RPs) is a need in several Internet of Things (IoT) applications. However, devising energy-efficient and reliable tour planning strategies for MS is a challenging issue, considering that sensors have finite buffer space and disparate sensing rates. This is even more challenging in delay-tolerant networks, where it is more desirable to select the shortest traveling path. There exist several algorithms on MS scheduling, which are based on hierarchical protocols for data forwarding and data collection. These algorithms are lacking efficient tradeoff between the Quality-of-Service (QoS) requirements in terms of energy efficiency, reliability, and computational cost. Besides, these algorithms have shown high packet losses while jointly performing MS tour planning and buffer overflow management. To address these limitations, we propose EE-MSWSN, an energy-efficient MS wireless sensor network that reliably collects data by implementing efficient buffer management. It forms novel clustered tree-based structures to cover all the network, and select each RP based on 1) hop count; 2) number of accumulated data in each clustered tree; and 3) distance to the stationary sink. The extensive simulation results verify that the EE-MSWSN minimizes tour length for various network configurations and incurs less energy consumption while reliably gathering data without packet losses as compared with existing protocols.

A Study of Transmission Overhead of a Hybrid Bundle Retransmission Approach for Deep-Space Communications

Bundle protocol (BP) was proposed as the core protocol of delay/disruption-tolerant networking for space. A hybrid reliable transmission mechanism based on integrating “proactive” retransmission and “reactive” retransmission of BP bundles has been presented as a means of achieving highly reliable file/data delivery in deep-space communications. Transmission overhead imposed by reliable delivery of data packets/bundles is consistently one of the key factors for efficient data delivery in space communications. It is especially important in deep-space networks, where the available electrical power on spacecraft for data delivery is a scarce resource but substantial energy is needed to propagate data over an extremely long deep-space channel. In this article, a detailed study of the transmission overhead for the hybrid retransmission approach of BP for reliable deep-space communications is presented. An analytical framework is presented for modeling the transmission overhead of BP as influenced by variations in channel quality, file size, bundle size, and retransmission timeout interval length. Its energy resource consumption is also briefly discussed. The analytical framework is validated by realistic file transfer experiments using a PC-based testbed infrastructure; the framework is found to be able to predict the performance with respect to the transmission overhead of BP.

Multicolor Licklider Transmission Protocol: An LTP Version for Future Interplanetary Links

The Licklider Transport Protocol (LTP) is the “convergence layer” of choice in Interplanetary networks based on Delay-/Disruption-Tolerant architecture. It was designed for long-delay scheduled-intermittent links, offering either a reliable or an unreliable service, with “red” and “green” parts, respectively. The aim of this article is to present multicolor LTP, an LTP version consisting in a series of enhancements of which the most significant are the use of monochrome sessions, the introduction of an additional orange color offering a “notified” service, and the definition of default link colors. After a thorough examination of basic LTP mechanisms for all color variants, this article discusses two scenarios where orange seems particularly appealing: video streaming and optical interplanetary links. Numerical results offer further insight into the complex LTP mechanisms and also highlight the difference between LTP retransmissions and bundle protocol retransmissions, the latter benefitting from routing reprocessing. Multicolor LTP has already been implemented as an interplanetary overlay network (ION) plug-in and its enhancements have been proposed to Consultative Committee for Space Data Systems Space Internetworking Services Delay-/Disruption-Tolerant Networking working group for a possible inclusion in the next version of LTP specifications (LTPv2).

Stability and average delay in delay tolerant networks with Poisson packet arrivals and buffered relay nodes

We consider a single-source single-destination delay tolerant network (DTN) with Poisson packet arrivals. The source uses a store and forward protocol which makes multiple copies of a packet to relays which buffer them until delivery to the destination. We characterize the stability threshold, defined as the maximum value of arrival rate for which the source has finite average queue length, as a function of number of relays, relay contact rate, relay packet buffer capacity, and number of packet copies. We analyse DTNs without packet delivery feedback and with instantaneous feedback. For DTNs without packet delivery feedback, we obtain a non-asymptotic analytical stability threshold and show that it only doubles as the relay-buffer capacity increases from one to infinity. For DTNs with instantaneous packet delivery feedback, we characterize the stability threshold using simulations. We also present an analytical approximation for the stability threshold in the case of unit relay-buffer capacity, and show that it is approximately double of that without feedback for large number of packet copies and relays. For DTNs with and without feedback, we also study the average delay performance through simulations. We obtain analytical approximations for the average delays of the packets for DTNs without feedback. We observe that the last-in-first-out relay to destination packet transmission policy has the minimum delay.

An improved multipath video data communication in a vehicular delay-tolerant network.

A vehicular network offers diverse beneficial services related to video streaming in different types of setups, including rural and urban. Some of the recent issues in vehicular communication include prospect of leveraging machine learning and blockchain for privacy and security enhancement, and resource allocation for video streaming coupled with integration of 6G networks for high data rate. Considering the extreme mobility and dynamic structure of vehicular networks and the high data rates of video streams, a unitary route may not support the required quality of a video stream. To achieve load balancing, connectivity among vehicles, path diversity, and low delay, the multipath transmission with a delay-tolerant network (DTN) concept based on a node disjoint algorithm is considered. In this proposed study, video frames are categorized in accordance with priority and forwarded via two graded paths. The first path carries the video reference frame, which is the most important frame for video decoding. The second path carries neighboring frames during video transmission. For the efficient selection of an optimal relay vehicle, a communication cost function is introduced into the existing DTN. This communication cost function is based on three key enhancement parameters: link stability rate, accessible bandwidth estimation, and transmission delay. The improvement in this study, is the integration of store-carry-forward strategy to the existing multipath data forwarding strategy. On the basis of the simulation outcomes, the proposed multipath video data communication in a vehicular DTN (MVDTN) scheme can enhance video data delivery in terms of packet loss ratio, end-to-end delay, structural similarity index measure, and peak signal-to-noise ratio. Considering the aforementioned metrics, our proposed schemes outperform the baseline schemes, namely, road-based multi-metrics forwarder selection evaluation for multipath video streaming and quality of service-aware multipath video streaming for an urban vehicular ad hoc network by using ant colony optimization.

Enhancing the Communication of IoT Using African Buffalo Delay Tolerant and Risk Packet Jump Approach

The Internet of Things is used in many sectors for different applications in an efficient way. However, sharing huge data to distant destinations is a difficult task such as sending large data from remote area for healthcare application. So that the Delay Tolerant Network is used but, in some cases, the presence of selfish nodes in Delay Tolerant Network may drop all the packets. To overcome this problem the current research affords a novel African Buffalo Delay Tolerant Network with Risk Packet Jump (ABDTN –RPJ) mechanism to improve the communication channel by predicting the selfish and misbehavior node in an earlier stage. Besides, RPJ is introduced to split the huge data to the other neighboring nodes to reduce packet load on the node if the load is greater than the capacity of the node. Finally, the ABDTN –RPJ is implemented and evaluated using the NS2 simulator. The comparison results proved the efficiency of the proposed model by reducing the delay and drop rate.

ReliefChain: A blockchain leveraged post disaster relief allocation system over smartphone-based DTN.

One of the major concerns in any emergency relief operation is appropriate allocation of scarce emergency relief materials to the affected community. Due to several reasons ranging from lack of mechanism to accurately assess demand and utility of relief materials to malicious participation of some of the stakeholders, such allocation may become ad-hoc. Thus, it becomes imperative to have an unchallengeable and globally accessible record of relief requirement vis-à-vis allocation for efficient relief management. Emergency response organizations (e.g. UNICEF) have recommended the adoption of blockchain technology to create such immutable records. However, the usage of blockchain is restricted by the availability of end-to-end internet connection which may not be available in a post-disaster scenario. This paper proposes ReliefChain, a blockchain leveraged post disaster relief allocation system over delay tolerant network that works in such environments. We validate relief requirements to mitigate resource diversion, forecasting the exact demand and enumerating precise utilities of relief items. We design smart contracts for creating new transactions to upload relief requirements and allocations in the blockchain network. The proposed system executes these smart contracts to create an immutable and globally accessible record of relief requirement and allocation. Effectiveness of the proposed system is evaluated through extensive simulation in Ethereum platform. Results substantiate the efficiency of the system over a system using baseline methodologies, in terms of design parameters like shelter specific deficit and average resource deficit while not compromising the blockchain performance in terms of processing time and gas consumption even in presence of malicious forwarders.

Effect of Designed Bundle Protocol about Ventilator Associated Pneumonia on Nurses' Performance, Compliance, and Patient Outcomes

Context: Ventilator-associated pneumonia (VAP) is considered one of the leading causes of morbidity and mortality due to nosocomial infections among ventilated patients.
 Aim: To evaluate the effect of a designed bundle protocol about ventilator-associated pneumonia on nurses' performance, compliance, and patient outcomes.
 Methods: The study employed the quasi-experimental research (pre/post-test) (study/control) design. This study was conducted at the intensive care unit of Benha University Hospital. A convenience sample of 50 critical care nurses and a purposive sample of 66 patients were enrolled in the current study. Three tools were used to collect data. Nurses' knowledge assessment questionnaire; nurses' practice assessment checklist; The VAP bundle compliance checklist; and patient outcomes assessment record.
 Results: Statistically significant improvement in total knowledge and practice mean scores post implementing a designed bundle protocol compared to pre-implementing a designed bundle protocol at p <0.001. Also, there was a statistically significant improvement in nurses’ compliance with a highly statistically significant difference between nurses’ compliance with practices of VAP bundle pre-and post designed bundle protocol implementation. Immediately after a designed bundle protocol implementation, the study group patients exhibited a statistically significant difference between all clinical pulmonary infection score items except for oxygenation status and radiographic findings.
 Conclusion: The study group nurses who received designed bundle protocol training would get improved knowledge, practices, and compliance scores than pre-designed bundle protocol training. Also, the study group of patients who were cared for by trained nurses on the designed bundle protocol would get better outcomes such as a better score of CPIS, shorter length of stay in the intensive care unit, less duration on mechanical ventilation compared to the control group who received routine hospital nursing care. The study recommended replication of the study using a large probability sample from a different geographical area to allow for greater generalization of the results.