Bundle Layer Research Articles

Optimal Cluster Head in DTN Routing Hierarchical Topology (DRHT)

In delay tolerant networking (DTN), nodes are autonomous and behave in an unpredictable way. Consequently, a control mechanism of topology is necessary. This mechanism should ensure the overall connectivity of the network taking into account nodes’ mobility. In this paper, we study the problem of data routing with an optimal delay in the bundle layer, by exploiting: the clustering, the messages ferries and the optimal election of cluster head (CH). We first introduce the DTN routing hierarchical topology (DRHT) which incorporates these three factors into the routing metric. We propose an optimal approach to elect a CH based on four criteria: the residual energy, the intra-cluster distance, the node degree and the head count of probable CHs. We proceed then to model a Markov decision process (MDP) to decide the optimal moment for sending data in order to ensure a higher delivery rate within a reasonable delay. At the end, we present the simulation results demonstrating the effectiveness of the DRHT. Our simulation shows that while using the DRHT which is based on the optimal election of CH, the traffic control during the TTL interval (Time To Live) is balanced, which greatly increases the delivery rate of bundles and decreases the loss rate.

Surface and interface effects on the current–voltage characteristic curves of multiwall carbon nanotube-Si hybrid junctions selectively probed through exposure to HF vapors and ppm-NO2

The possibility to increase the efficiency of photovoltaic (PV) cells based on hybrid carbon nanotube (CNT)–Si heterojunctions is related to the ability to control the chemical properties of the CNT–Si interface and of the CNT bundle layer. In spite of the encouraging performances of PV cells based on multiwall (MW) CNT, so far few efforts have been made in the study of this device compared to single wall (SW) CNT–Si interfaces. Here, surface and interface effects on the current–voltage characteristic curves of MW CNT–Si hybrid junctions are investigated through exposure to HF vapors and to 10 ppm-NO2 and compared to the effects detected in SW CNT–Si junctions. Quite similar results in terms of open circuit voltage, short circuit current density, and efficiency are found for both cells, suggesting that exposure to HF vapors mostly affects the interface chemical properties, i.e., the silicon oxidation state, that in both junctions reach an optimal state about 50 h after etching. In turn, NO2 exposure has larger effects on the SW-based cell, consistently with the larger surface-to-volume ratio of SW with respect to MW. In both cases, the efficiency value reaches a maximum after 28 min, before dropping when the NO2 molecules desorb from the surface. A combined analysis of current–voltage curves and photoemission data collected along the different phases of gas exposures allowed us to relate changes in the electrical properties to the chemistry of Si at the interface.

Modeling and topology design for free-space optical networks

To date, free-space optical (FSO) networks play an important role in current network construction to support large-capacity transmission, where randomly distributed FSO terminals desire to exchange a tremendous amount of information over atmospheric turbulence channels. However, in the presence of atmospheric turbulence and misalignment fading channels, FSO network topology can be dynamic and disconnected. To mitigate the impact of dynamic network environments, appropriate higher-layer protocols should be designed. We explore a practical terrestrial mobile ad-hoc FSO network based on the bundle protocol of disruption-tolerant network, and the theoretical cross-layer system model between physical layer and network layer is derived. To design the topology, at the bundle layer, the distributed routing scheme centrality and probability (CAP) is proposed, where contact probability, sociocentric measure, and message replication strategy are considered simultaneously, and the joint forwarding decision rule is given. Simulation results on the opportunistic networking environment simulator are presented, which show that CAP can be better compared with the conventional end-to-end protocol-based routing scheme.

Integrated Sized-Based Buffer Management Policy for Resource-Constrained Delay Tolerant Network

Delay tolerant network is a type of network where the end-to-end path is not available from source to destination due to the node mobility, dynamic topology and network partitioning or such a path is highly unstable and may split almost immediately after it has been explored. In this background, existing ad hoc routing protocols would be unsuccessful. Therefore, the concept of store-carry-forward mechanism is utilized by introducing a new layer on the top of transport layer called as bundle layer. The bundle layer store message(s) in a finite size buffer for the long duration of time. As a result, node buffer runs out of space and drop messages to overcome congestion. In this paper, we aim to schedule the node buffer by using local knowledge-based buffer management policies called as best message-size selections buffer management policy. We have utilized the local information available in message header such as message-size to control the drop of messages. The evaluation of proposed policy with the existing DOA, DLA, LIFO, MOFO, N-drop and SHLI have been analyzed in ONE simulator in terms of reducing message drop, overhead, latency and raising the delivery ratio.

A Reed-Solomon Based Method to Improve Message Delivery in Delay Tolerant Networks

Delay and Disruption Tolerant Networks are made up of mobile wireless nodes which may experience major message delivery restrictions. Such restrictions are the result of intermittent connectivity and scattered topology. Within these networks, messages can be detained for long periods of time or never be delivered. Existing solutions that purport improved message delivery rates modify routing protocols to perform integrity verification with each hop, resulting in routing overhead and, very often, unnecessary processing costs. This article proposes a scheme, named EMCOD, which decreases message delivery delay, while minimally increasing the processing overheads. To achieve this, EMCOD uses data encoding and interleaving to create messages. The original data is reassembled from some of the messages received, without the need to wait for all messages to be received. In scenarios subject to long delays and/or significant packet loss rates, it is possible to reduce original data recovery times by more than 50%. The processing overhead resulting from the encoding procedures is offset by the data recovery capabilities, which effectively decreases network overheads by more than 60%, in the same scenarios. EMCOD modifies the Bundle Layer, without interfering with the remaining layers, making it possible to route the messages through nodes that do not implement the proposed scheme.

Caryopsis transfer system in an Avena magna Murphy et Terrell × A. longiglumis Dur. amphiploid

Evaluation of the structure of the caryopsis transfer system is presented for an Avena magna × A. longiglumis amphiploid. Each component of the system such as vascular bundle, pigment strand, nucellar projection and ventral aleurone layer varies between the amphiploid and its parental species. The number of xylem vessels present in the caryopsis bundle expressed heterosis-like inheritance. The position of the caryopsis xylem bundle in A. longiglumis shows a lower efficiency in assimilate transport. Some anomalies in the development of the ventral aleurone layer and parenchyma, adjacent to the transfer system, are presented.

Laminated structure design of wood—Bamboo hybrid laminated composite using finite element simulations

In order to explore competitive bio-products to meet the requirements of the engineering structural member with high-strength, light-weight and low cost, bamboo bundle and wood laminated veneer lumbers (BWLVLs) with well-designed laminated structures have been regarded as potential candidate. Eight different assemble patterns of BWLVLs were designed and their mechanical performances with elastic range and ultimate bearing failure stage including the deflection, stress distribution, and stress transferring between adjacent layers were investigated using finite element simulations. The results showed that the finite element predicting model with a high accuracy could be used to optimize the design of laminated structures for bamboo bundle and wood veneer laminated composites. The relative error of the simulation results from the predicting model and the experimental results for different laminated composite panels was substantially less than 10%. The rank order for the VonMises stress of eight assemble BWLVLs were (7B) > (BBPPPBB) ≈ (BBPBPBB) > (BPBPBPB) > (BPPPPPB) ≈ (BPPBPPB) > (PBPBPBP) > (7P), (P) poplar, and (B) bamboo. The stress in laminated composites was transferred from poplar layers with low modulus to bamboo bundle layer with high elastic modulus.

Performance improvement in DTNs by packet size optimization

In space communication environments, most studies in delay tolerant networks (DTNs) adopt experimental approaches and they have shown that the utilization efficiency of link bandwidth can be affected by changing packet sizes at the bundle layer and the convergence layer. However, the lack of theoretical work makes it difficult to find the optimal packet sizes in general scenarios. In this paper, we focus on this important issue by performing a theoretical analysis to solve the packet size optimization problems in both one-hop and multihop DTNs. As our analysis is based on the widely used DTN architecture with Bundle Protocol (BP) and Licklider Transmission Protocol (LTP), the theoretical results can be applied to any DTN scenario using this architecture. We formulate packet size optimization problems in DTNs as nonconvex optimization problems. Furthermore, a goodput enhancement algorithm (GEA) is also proposed to find the optimal packet sizes in order to maximize goodput in DTNs. We conduct numerical analysis as well as simulations to validate our theoretical analysis and study the factors that determine the optimal packet sizes for BP and LTP. Numerical results show that GEA achieves significant performance improvement compared with schemes where packet size optimization on BP and LTP is not jointly considered.

Receiver-Triggered Handshake Protocol for DTN in Disaster Area

When a disaster hits a wide area, communication services for public use will be rendered unavailable. This will make it difficult to confirm the safety of people in the disaster area. A solution to this problem is to form delay/disruption tolerant networks (DTN) using mobile terminals of victims, those of rescuers, who serve as information carriers, and terminals (servers) in shelters. In this paper, we propose using a receiver-triggered handshake protocol for communication between these terminals. We have developed the bundle layer protocol for this handshake method. The proposed method has been implemented on a network simulator to build an evaluation environment. The disaster area has been modeled on an area around Shinjuku Station in Tokyo. Victims are randomly distributed in the area. We have compared the proposed method with Epidemic Routing and Spray and Wait in terms of the delivery rate at which messages reach their destinations, and the length of time taken for messages to reach their destinations. We have found that the delivery rate of the three methods are, more or less, the same, but that the proposed method is superior to the other two methods in terms of storage usage and battery consumption of terminals, and the number of bundles generated in the network.

마찰 드럼 상에서의 집속체 꼬임 구조 특성

Frictional bundling of fibers is accompanied by twists that compel the bundle cohesion force to generate bundle strength. Twists generated by friction occur in two forms; one by fiber arrangement on the bundle layer and the other by torque due to the thickness distribution of the bundle on the friction surface. This study investigates the twists of a friction bundle that occur on the friction surface, and theoretical models of twists are applied to develop total twist and the twist characteristics by simulation. Results showed that the fiber arrangement twists are directionally opposite to the torque twists; fiber arrangement twists occur as S-twists and torque twists as Z-twists. In the steady state the bundle exiting the friction zone had S-twists finally and the twists per length was uni- form along the bundle radius. The steady state twists of the bundle at the exit of the fric- tion zone were determined by two model constants and a process variable. The two model constants were composed of model parameters such as slippage ratio, minimum thickness of the fleece for bundling, the density ratio of the bundle to the input fleece, and also of process variables such as friction ratio, the speed ratio of the fleece feeding to bundle take- up, and the thickness of the input fleece. The process variable acting directly on the bundle twist was the fleece feeding width. Thus, the twist angle of the bundle in the friction zone varied with the radial position inside the bundle. The twist angle was the lowest in the vicinity of the bundle axis. As the fiber layer approaches the bundle surface, the twist angle increases.

Custody Transfer of Bundle layer in Security Mechanism for Under water Inter net of Things (UIoT)

The intent is to determine whether or not the custody transfer is helpful for data transmission in challenging underwater communications when running Bundle protocol or underwater protocols. From the point of view defending side, Underwater Acoustic Network (UAN) will be a serious threat for its strong functionality long rang and high precision of surveillance and detection. Therefore, countermeasures must be taken to weaken its effect. Our purpose is analyzed that how to benefit from the UIoT to learn from, exploit and preserve the natural underwater resources. Delay/Disruption Tolerant Network (DTN) is essential part of the network heterogeneity communication network. The vulnerability and potential security factors of UIoT are studied thereafter. Security mechanisms for an underwater environment are difficult to apply owing to the limited bandwidth. Therefore, for underwater security, appropriate security mechanisms and security requirements must be defined simultaneously. The paper consists of mathematical and security model. Most important point of view in the security challenges of effective Buffer and Storage management in DTN.

Design and Implementation of Bundle and Network Layer in Tactical Text Messaging Radio Using Delay Tolerant Network (DTN)

Design and Implementation of Bundle and Network Layer in Tactical Text Messaging Radio Using Delay Tolerant Network (DTN)

ECOP: Energy Conserving Postboxes in Postbox Delay Tolerant Networks

Abstract The Delay Tolerant Network (DTN) came as a saviour for heterogeneous networks marked by intermittent connectivity and low energy levels. By the introduction of the BUNDLE layer in addition to the TCP/IP layers, the DTN tries to achieve what the TCP/IP could not i.e. allow communication in challenged networks. The Postbox DTN is a type of DTN which has a persistent node known as Postbox which is always ON. All nodes have a direct connection to it and no other connection between nodes exist. Hence all communication is made via and by the Postbox just like the real world Postbox scenario. Apart from the novel concept of a 1 hop routing strategy, it is very easy to deploy. However its ease of use comes at a huge cost of energy usage by its always ON Postboxes. This work proposes a modified Postbox model which conserves energy without depreciating its performance. Simulation results confirm our hypothesis.

Establishment of the Novel Cystoscopic Classification for Bladder Trabeculation of Neurogenic Bladder

To establish a cystoscopic grading system for trabeculation of neurogenic bladders. A total of 140 neurogenic bladder patients who had undergone both fluoroscopic urodynamic study and cystoscopic examination were retrospectively reviewed. Cystoscopic images were categorized into 4 grades according to the formation of the muscle bundle layer and height-to-width ratio of the muscle bundle: 0 (none), 1 (mild), 2 (moderate), and 3 (severe). Test-retest reliability and interobserver reliability were assessed. Cystoscopic grade of the trabeculated bladder was correlated with urodynamic results and the fluoroscopic grades of trabeculation. The test-retest reliability showed almost perfect agreement with all levels of Cronbach alpha ranging from 0.925 to 0.970. The intraclass correlation coefficient was 0.986, indicative of an almost perfect level of interobserver reliability. The grading system showed clinical significance by correlation with urodynamic parameters (Qmax, P value = .016; postvoid residual, P value <.001; bladder outlet obstruction index, P value = .002). Cystoscopic grades correlated moderately well with fluoroscopic grades, showing comparable clinical significance with fluoroscopic grades. Our results showed that this novel cystoscopic classification of bladder trabeculation was highly reliable.

Performance evaluation of a cooperative reputation system for vehicular delay-tolerant networks

Abstract In the last decade, both scientific community and automotive industry enabled communications among vehicles in different kinds of scenarios proposing different vehicular architectures. Vehicular delay-tolerant networks (VDTNs) were proposed as a solution to overcome some of the issues found in other vehicular architectures, namely, in dispersed regions and emergency scenarios. Most of these issues arise from the unique characteristics of vehicular networks. Contrary to delay-tolerant networks (DTNs), VDTNs place the bundle layer under the network layer in order to simplify the layered architecture and enable communications in sparse regions characterized by long propagation delays, high error rates, and short contact durations. However, such characteristics turn contacts very important in order to exchange as much information as possible between nodes at every contact opportunity. One way to accomplish this goal is to enforce cooperation between network nodes. To promote cooperation among nodes, it is important that nodes share their own resources to deliver messages from others. This can be a very difficult task, if selfish nodes affect the performance of cooperative nodes. This paper studies the performance of a cooperative reputation system that detects, identify, and avoid communications with selfish nodes. Two scenarios were considered across all the experiments enforcing three different routing protocols (First Contact, Spray and Wait, and GeoSpray). For both scenarios, it was shown that reputation mechanisms that punish aggressively selfish nodes contribute to increase the overall network performance.

Designing of Dynamic Sensor Networks based on Meter-range Swarming Flight Type Air Nodes

Dynamic sensor network(DSN) technology which is based on swarming flight type air node offers analyzed and acquired information on target data gathered by air nodes in rotation flight or 3 dimension array flight. Efficient operation of dynamic sensor network based on air node is possible when problems of processing time, data transmission reliability, power consumption and intermittent connectivity are solved. Delay tolerant network (DTN) can be a desirable alternative to solve those problems. DTN using store-and-forward message switching technology is a solution to intermittent network connectivity, long and variable delay time, asymmetric data rates, and high error rates. However, all processes are performed at the bundle layer, so high power consumption, long processing time, and repeated reliability technique occur. DSN based on swarming flight type air node need to adopt store-and-forward message switching technique of DTN, the cancelation scheme of repeated reliability technique, fast processing time with simplified layer composition.

A Network Coding based DTN Convergence Layer Reliable Transport Mechanism over InterPlaNetary Networks

The realization of deep space scientific missions are enabled by the developments in the space technologies. TCP can not provide effective communication service in deep space links because of the long propagation delay and high BERs characteristics.Scientific community propose Delay Tolerant Network (DTN) for resolving the communication problem between earth and other planet. DTN introduces a new layer in the protocol stack called Bundle Layer that is placed between application layer and transport layer.DTN calls the transport protocols that it uses to move data across different networks convergence layers. This study present a novel Network Coding based convergence layer Reliable TransPort mechanism(NC-RTP) in order to provide effective communication service between DTN peers. This mechanism transmit a coded bundle every M original bundles(M is related to the packet error rate of the communication link). The coded bundle is a random linear combination of previous M original bundles. Using coded bundle and (M-1)original bundles, the receiver could decode and generate a single lost bundle of previous M original bundles . In this way, NC-RTP could compensate any single lost bundle in (M+1) transmitted bundles(including M original bundles and 1 coded bundle).Our theoretical and simulation performance evaluation results reveal that NC-RTP can enhance transmit reliability and make file transfered faster.

DTN Bundle Layer over TCP: Retransmission Algorithms in the Presence of Channel Disruptions

“Challenged n etworks” often violate the TCP design key assumption of continuous path availability from the source to the sink node. These networks are the preferred target of Delay/Disruption Tolerant Networking (DTN), which aims at providing a more robust network architecture. Against disruptions, however, even standard TCP offers a certain level of robustness, through its many retransmission algorithms. This intrinsic TCP resilience against disruptions is retained and enhanced if TCP is inserted in a DTN architecture. Focusing on this, the aim of the paper is to present an in-depth analysis of TCP and DTN bundle protocol retransmission algorithms that are triggered by channel disruptions, thus providing the reader with a comprehensive view of the many mechanisms involved and their complex interactions. The first sections, devoted to the description of TCP and DTN algorithms, are completed by the presentation of some numerical evaluations obtained by means of a Linux testbed. They refer to a GEO satellite environment and clarify the previous algorithm descriptions. Moreover, they also offer the reader some useful insights on both TCP and DTN resilience to disruptions, considering some performance metrics, like the “ maximum tolerable disrupti on length” and the “restart delay”, introduced and explained in the paper.

Damage in NCF composites under tension: Effect of layer stacking sequence

Non-crimp fabric (NCF) cross-ply composites response to tensile loading is investigated showing large effect of the fabric layer stacking sequence: much larger elastic modulus reduction was observed in [0/90/0/90] S than in [90/0/90/0] S case. Since transverse cracks in 90°-bundles may give modulus decrease about 5%, the observed 40% stiffness reduction is attributed to failure and delamination of bundles oriented in the direction of the applied load. Analysis of micrographs shows extensive delaminations and 0°-bundle breaks. FE calculations showed that failure of 0°-bundles at the surface is energetically more favorable. However, the fracture resistance of surface bundles is higher due to smaller bundle waviness and the density of bundle cracks on the surface was not larger than inside. Two possible reasons for the higher stiffness reduction in the [0/90/0/90] S NCF composite were suggested: (a) If two imperfect 0°-bundle layers are separated by a 90°-bundle layer their resistance to failure is lower than when they are situated next to each other; (b) the effect of each surface 0°-bundle break on the composite stiffness is larger (due to less constraint from the surrounding material the opening of surface bundle breaks is much larger).

Automatic Recognition and Analysis of Scanned Non-crimp Fabrics for Calculation of their Fluid Flow Permeability

Automatic recognition of scanned images of distorted bi-axial fiber bundle arrangements is considered in order to obtain the overall permeability of the formed fiber network. Scanned images are pre-processed with color normalization followed by usage of a threshold to find the pixels belonging to the bundles, the threads keeping the bundles together, and the distinct gaps formed between the bundles. Since the scanned images virtually have a perfect grayscale, the intensity can be treated as a corresponding signal of the image. Next the regular character of the fiber network is investigated using Fourier analysis on the fiber bundles as well as on the threads. The direction, position, and spatial separation of the fiber bundle and the threads are obtained in this way. In order to recognize the bottom fiber bundle layer a fine structure technique is used. Small clusters falsely identified as belonging to the bottom bundle layer are removed by application of a threshold to the perimeter of the cluster. The gaps in the top bundle layer are identified more clearly in this way. Next, a local Fourier analysis is applied to obtain the local distortion of the bundle and the thread structure yielding the characteristic distribution of the gaps between the bundles. Finally the distribution of the width of the threads is obtained by simply identifying the minimal distance between the sides of the threads.