Hop Path Research Articles

DIA-TORUS:A Novel Topology for Network on Chip Design

The shortcomings of conventional bus architectures are in terms of scalability and the ever increasing demand of more bandwidth. And also the feature size of sub-micron domain is decreasing making it difficult for bus architectures to fulfill the requirements of modern System on Chip (SoC) systems. Network on chip (NoC) architectures presents a solution to the earlier mentioned shortcomings by employing a packet based network for inter IP communications. A pivotal feature of NoC systems is the topology in which the system is arranged. Several parameters which are topology dependent like hop count, path diversity, degree and other various parameters affect the system performance. We propose a novel topology forNoC architecture which has been thoroughly compared with the existing topologies on the basis of different network parameters.

다중 홉 무선 네트�p에서 지연을 고려한 멀티케스트 루팅

Static wireless multi-hop networks, such as wireless mesh networks and wireless sensor networks have proliferated in recent years because of they are easy to deploy and have low installation cost. Two key measures are used to evaluate the performance of a multicast tree algorithm or protocol : end-to-end delay and the number of transmissions. End-to-end delay is the most important measure in terms of QoS because it affects the total throughput in wireless networks. Delay is similar to the hop count or path length from the source to each destination and is directly related to packet success ratio. In wireless networks, each node uses the air medium to transmit data, and thus, bandwidth consumption is related to the number of transmission nodes. A network has many transmitting nodes, which will cause many collisions and queues because of congestion. In this paper, we optimize two metrics through a guaranteed delay scheme. We provide an integer linear programming formulation to minimize the number of transmissions with a guaranteed hop count and preprocessing to solve the aforementioned problem. We extend this scheme not only with the guaranteed minimum hop count, but also with one or more guaranteed delay bounds to compromise two key metrics. We also provide an explanation of the proposed heuristic algorithm and show its performance and results.

Performance Evaluation of Best-Path Selection in a Multihop Decode-and-Forward Cooperative System

Multihop communication is considered to be a useful approach for improving the coverage area with reduced transmit power. In this paper, we consider a path-selection-based multihop decode-and-forward (DF) cooperative system. A simple parallel multihop path-based cooperative communication system is considered. It is assumed that all hops in all cooperative paths are subject to independent Rayleigh fading. The best path, that is, the best multihop link between the source and the destination, is selected based on the max–min selection criterion. The relays in the selected cooperative path use the symbol-wise DF protocol, in which they demodulate the received data from the preceding node in a symbol-wise manner and forward it to the succeeding node. An analytical framework is developed for finding an accurate (almost close to exact) error performance of the considered system. To be more specific, we derive an accurate expression of the average bit error rate of the max–min-criterion-based best-path selection scheme, in terms of convergent power series. The coding gain and the diversity order of the scheme are also analytically obtained.

Thermally activated charge transport in microbial protein nanowires.

The bacterium Geobacter sulfurreducens requires the expression of conductive protein filaments or pili to respire extracellular electron acceptors such as iron oxides and uranium and to wire electroactive biofilms, but the contribution of the protein fiber to charge transport has remained elusive. Here we demonstrate efficient long-range charge transport along individual pili purified free of metal and redox organic cofactors at rates high enough to satisfy the respiratory rates of the cell. Carrier characteristics were within the orders reported for organic semiconductors (mobility) and inorganic nanowires (concentration), and resistivity was within the lower ranges reported for moderately doped silicon nanowires. However, the pilus conductance and the carrier mobility decreased when one of the tyrosines of the predicted axial multistep hopping path was replaced with an alanine. Furthermore, low temperature scanning tunneling microscopy demonstrated the thermal dependence of the differential conductance at the low voltages that operate in biological systems. The results thus provide evidence for thermally activated multistep hopping as the mechanism that allows Geobacter pili to function as protein nanowires between the cell and extracellular electron acceptors.

MAODV: A Defense against Sybil Attacks in Wireless Networks

Wireless networks are gaining popularity to its peak today, as the users want wireless connectivity irrespective of their geographic position. An ad-hoc wireless network is a collection of nodes that come together to dynamically create a network, with no fixed infrastructure or centralized administration. In mobile ad-hoc networks, data transmission is performed within an untrusted wireless environment. The lack of centralized infrastructure in ad-hoc network makes it vulnerable to various attacks. Sybil attack is one of the serious attacks, which form a serious threat in the networks, especially against many ad hoc wireless routing protocols, and location based wireless security system. In the Sybil attack incorporates a malicious device with the ability to illegitimately take on several identities in the same network. The forged identity from a malicious device is called a Sybil node. A malicious device can obtain an identity for a Sybil node in two different ways; (a) generating a new identity; or (b) taking the identity from an existing node (with the cooperation of the node or by developing a spoofing attack). We identify two types of Sybil attacks. In the first type, malicious nodes do not take part in finding routes, meaning that, legitimate nodes do not know their existence. In the second type, malicious nodes do create route advertisements and legitimate nodes are aware of the existence of malicious nodes, just do not know they are malicious. Some of the researchers have proposed many solutions for Sybil attack. In this paper, an efficient method to detect a Sybil attack called modified Sybil detection AODV protocol has been proposed. Detection of Sybil attack is performed using number of hops in different paths from source to destination and delay of each node in different paths from source to destination. The destination is able to detect both kinds of Sybil attacks. The performance of modified Sybil detection AODV protocol is justified by simulations.

A Novel Dynamic Physical Layer Impairment-Aware Routing and Wavelength Assignment (PLI-RWA) Algorithm for Mixed Line Rate (MLR) Wavelength Division Multiplexed (WDM) Optical Networks

AbstractThe ever-increasing global Internet traffic will inevitably lead to a serious upgrade of the current optical networks’ capacity. The legacy infrastructure can be enhanced not only by increasing the capacity but also by adopting advance modulation formats, having increased spectral efficiency at higher data rate. In a transparent mixed-line-rate (MLR) optical network, different line rates, on different wavelengths, can coexist on the same fiber. Migration to data rates higher than 10 Gbps requires the implementation of phase modulation schemes. However, the co-existing on-off keying (OOK) channels cause critical physical layer impairments (PLIs) to the phase modulated channels, mainly due to cross-phase modulation (XPM), which in turn limits the network’s performance. In order to mitigate this effect, a more sophisticated PLI-Routing and Wavelength Assignment (PLI-RWA) scheme needs to be adopted. In this paper, we investigate the critical impairment for each data rate and the way it affects the quality of transmission (QoT). In view of the aforementioned, we present a novel dynamic PLI-RWA algorithm for MLR optical networks. The proposed algorithm is compared through simulations with the shortest path and minimum hop routing schemes. The simulation results show that performance of the proposed algorithm is better than the existing schemes.

Improved TEEN Routing Protocol with Multi Hop and Multi Path in Wireless Sensor Networks

Wireless Sensor Networks are used in monitoring environment condition, safety and medical applications. The sensor nodes are usually randomly deployed in a specific region. All these sensor nodes collect their data and send it to the base station (BS) through some routing protocol. These nodes are not rechargeable nodes to keep them alive. These nodes may serve as long as possible without any external assistance, they must follow some protocol that ensure efficient use of their power. In energy consumption of each node a routing technique plays a key role. Many of the routing protocols use clustering as their routing technique. So clustering plays a key role in prolonging the stability period and network life time. The Cluster Heads (CHs) collects data from all the nodes in their cluster, perform aggregation on that and then finally send it to the BS. Sensor nodes must use a certain routing protocol to send their data efficiently to the BS. The objective of all routing protocols is to minimize the energy consumption so that the network lifetime and particularly the stability period of the network may be enhanced. By network lifetime we mean the time duration from the start of the network till the death of the last node whereas, stability period shows the time period from the start of the network till the death of the first node. This paper has an objective to develop an energy efficient increased lifetime threshold sensitive clustering algorithm by dynamic selection of cluster heads using multi-hops and multi-path, that leads to load balancing on different-different clusters. This results in the enhancement of cluster heads or normal nodes network lifetime and comparison of performance of the various proposed clustering protocol with TEEN. In this work we propose an energy efficient multipath routing algorithm in WSN. This protocol is designed to enhance the network life time and energy efficiency through discovering multiple paths from the source to the destination.

Studies on role of grain-size on transport properties of Sm0.5Sr0.5CoO3−δ cathodic films

The transport properties of mixed conducting Sm0.5Sr0.5CoO3−δ (SSC) films featuring mean grain sizes from 44 nm to 4.42 μm are studied with regard to grain-size effects. A remarkable enhancement in total conductivity of about one order is found in nano-scaled films than that of micro-crystalline films. In micro-crystalline films, a change in the transport mechanism as a function of temperature is observed, which is attributed to a transition from bulk controlled (at high temperatures) to grain-boundary controlled (at low temperatures) charge transportation. The films having nano-grains facilitates the charge transportation via parallel grain-boundaries and attribute to enhance the total conductivity through grain-boundaries. Alongside, the AC conductivity study showed that the charge carriers in nano-scaled films follow a long-range hopping path in the entire temperature region. Hence, the nano-scaled Sm0.5Sr0.5CoO3−δ cathodic films will give higher and steady state performance in solid oxide fuel cell (SOFC) in the low temperature region.

Fast Edge-Aware Denoising by Approximated Patch Geodesic Paths

Patch-based denoising, while effective, requires expensive pairwise patch comparisons. We present a novel fast patch-based denoising technique based on patch geodesic paths (PatchGPs). PatchGPs treat image patches as nodes and patch differences as edge weights for computing the shortest (geodesic) paths. The distance defined by the PatchGP can then be used as a similarity metric for image denoising. We first show that, for natural images, PatchGPs can be approximated by minimum hop paths (MHPs) that correspond to Euclidean line paths connecting two patch nodes. The denoising kernel is constructed using patches along discretized MHP search directions. We apply a weight propagation scheme to robustly and efficiently compute the path distance for each MHP. Our technique handles noise at multiple scales by analyzing the noise distribution (through wavelet decomposition) at each scale. Experiments show that our approach maintains the high quality of patch-based denoising but is a few orders of magnitude faster. We also demonstrate how PatchGP can be used for fast Bayer pattern (raw) denoising and image detail enhancement.

Fault Tolerant Multi-Criteria Multi-Path Routing in Wireless Sensor Networks

The Ad Hoc On-Demand Multi-Path Distance Vector (AOMDV) routing protocol allows the transport of data along one or more paths in wireless sensor networks (WSNs). The path chosen is based on a single shortest path hop count metric. The data on some WSNs is mission critical, for example, military and health care applications. Hence, fault tolerance in WSNs is becoming increasingly important. To improve the fault tolerance of WSNs in lossy environments, this work adds to the AOMDV routing protocol as it incorporates an additional packet loss metric. This Multi-criteria AOMDV or M-AOMDV is evaluated using the ns2 simulator. Simulations show that M- AOMDV maintains relatively low packet loss rates when the WSN is experiencing loss.

Deposition of YBaCo4O7+δ thin films on (001)-SrTiO3 substrates by dc sputtering

The structure, magnetic and magnetotransport properties of YBaCo4O7+δ thin films deposited by high oxygen-pressure dc magnetron sputtering on (001)-oriented SrTiO3 substrates have been studied. The film growth was carried out at three different substrate temperatures (750 °C, 850 °C and 870 °C) in order to determine the influence of this parameter on the crystalline quality of the films deposited on SrTiO3 substrates. Within these limits, the growth quality, with respect to the preferential growth orientation, changed significantly improving notably with increasing substrate temperature. The enhanced intensity of (203), (220) and (110) reflections stemming from films grown at 850 °C suggests that the as-grown films are polycrystalline. In turn, the dependence of the resistivity on temperature shows a semiconducting-like behavior, without any distinguishable structure, in the temperature range measured (400–120 K). The analysis of the experimental data shows that the transport mechanism in the films is well described by using the Mott variable range hopping (VRH) conduction model. From the fitting procedure, a temperature scale T∗∼107 K is obtained which ended up being similar to that found in other transition metal oxides. The fact that the conductivity of oxygen-rich YBaCo4O7+δ samples features a VRH nature implies itinerant electron states with the apparent insulating behavior due to magnetic frustration. Interestingly, the YBaCo4O7+δ thin films show a positive magnetoresistance over the studied temperature range without evidence for transition to negative values as observed in ferromagnetic cobaltites. The origin of the positive magnetoresistance effect in the studied samples is difficult to explain by the known magnetoresistance models as the samples don't show evident magnetic transition in the entire temperature region from low temperature to room temperature. Nevertheless, the main features of the positive magnetoresistance seem to be explained by Zeeman splitting of the localized states that suppresses the spin dependent hopping paths in the presence of on-site Coulomb repulsion.

Analytical Evaluation of Directional-Location Aided Routing Protocol for VANETs

Vehicular Ad-hoc Networks (VANETs) are now considered as a way to realize active safety, by providing the position information of each other or the possible danger warning by wireless vehicular communications. Multi-hop data delivery in VANETs is a challenging task, since it encounters rapid changes in network topology and frequent fragmentation in the network. Because of these characteristics, routing algorithms based on greedy forwarding are known to be very suitable for VANETs. The design and implementation of efficient and scalable routing protocols for VANETs is a challenging task due to high dynamics and mobility constraints. In this paper, we have worked on a routing protocol over VANETs to efficiently broadcast the information for the sake of active safety applications, such as the positions and the directions of the vehicles. Therefore, we have explained a position-based routing protocol called directional-location aided routing (D-LAR) with (1) location-aided routing utilizes location information using GPS to limit the area for discovering a new route to a smaller request zone and (2) directional routing having direction closest to the line drawn between source and destination. D-LAR protocol is a greedy based approach to forward packet to the node present in request zone part of sender's transmission range as a most suitable next-hop node. Further, we have justified the feasibility of D-LAR routing protocol for VANETs. Through analytical analysis we have also given the relationship among the average number of hop counts, link lifetime, and path throughput metrics for the protocol. Finally, simulation results show that the proposed formulation can be used to evaluate path throughput accurately in the network.

Ferromagnetism and Crossover of Positive Magnetoresistance to Negative Magnetoresistance in Na-Doped ZnO

Na doped ZnO films were fabricated via a hydrothermal process. The films have shown room temperature ferromagnetism and p-type conductivity. Crossover of positive to negative magnetoresistance has been observed with the variation of Na doping concentrations. The positive MR is due to p-p exchange interaction induced Zeeman splitting to suppress the hopping path of holes. The ferromagnetism is attributed to the formation of a Zn vacancy complex. The negative magnetoresistance is due to the minimization of spin-dependent scattering by the applied magnetic field.

Hole detection and shape-free representation and double landmarks based geographic routing in wireless sensor networks

In wireless sensor networks, an important issue of geographic routing is “local minimum” problem, which is caused by a “hole” that blocks the greedy forwarding process. Existing geographic routing algorithms use perimeter routing strategies to find a long detour path when such a situation occurs. To avoid the long detour path, recent research focuses on detecting the hole in advance, then the nodes located on the boundary of the hole advertise the hole information to the nodes near the hole. Hence the long detour path can be avoided in future routing. We propose a heuristic hole detecting algorithm which identifies the hole easily and quickly and then propose a representation of hole no matter what the shape of the hole is. In addition, we quantitatively figure out the areas in the vicinity of the hole that need to be announced the hole information. With such information, a new routing scheme with two landmarks was developed. Simulation results illustrate that our approach can achieve better performance in terms of the average length and number of hops in routing paths. Simulation also shows that our approach introduces very small computational complexity.

The Case for Network Coding for Collective Communication on HPC Interconnection Networks

SUMMARY Recently network bandwidth becomes a performance concern particularly for collective communication since bisection bandwidths of supercomputers become far less than their full bisection bandwidths. In this context we propose the use of a network coding technique to reduce the number of unicasts and the size of data transferred in latency-sensitive collective communications in supercomputers. Our proposed network coding scheme has a hierarchical multicasting structure with intra-group and inter-group unicasts. Quantitative analysis show that the aggregate path hop counts by our hierarchical network coding decrease as much as 94% when compared to conventional unicast-based multicasts. We validate these results by cycle-accurate network simulations. In 1,024-switch networks, the network reduces the execution time of collective communications as much as 70%. We also show that our hierarchical network coding is beneficial for any packet size.

A Novel Energy Efficient Routing Algorithm for Wireless Sensor Networks Using Sink Mobility

There are numerous applications for wireless sensor networks which are inevitable now a day in our daily life. Majority of such applications which use wireless sensor networks will be in areas where the direct human intervention is impossible. So the limited energy available in such sensors is a threat for prolonging the life of the entire network. The need of energy efficiency in wireless sensor networks is a hot research topic in which lot of new strategies for improvement in energy efficiency has been sought after. As communication process consumes more energy, an energy efficient routing strategy can probably reduce the energy consumption to a great extend. This paper gives an overview of the different routing techniques in which mobile sinks are used to facilitate the routing process which can effectively reduce the energy use. A new routing strategy with mobile sinks and a static sink is proposed and is compared based on the matrices life time and average energy of the nodes with the existing Shortest Hop path (SH) algorithm. The simulation results shows the proposed algorithm is more energy efficient than the existing one.

Role of Unidirectionality and Reverse Path Length on Wireless Sensor Network Lifetime

Transceiver characteristics, asymmetric interference, and various properties of electromagnetic propagation environment create unidirectional links in wireless sensor networks (WSNs), especially in extreme environments. Utilization of unidirectional links is shown to improve network connectivity and lifetime. In practical WSNs, link level data exchange is performed through handshaking. However, a special handshake mechanism, where acknowledgment (ACK) packets are conveyed through a multihop reverse path, is necessary to be able to utilize unidirectional links. In this mechanism, hop length of the reverse path is a key design parameter because by allowing longer reverse paths, more unidirectional links can be utilized. However, increasing the reverse path hop length increases the energy overhead due to the extra ACK packets. Furthermore, complexity of maintaining the data flow also increases as the allowed maximum reverse path hop length increases. In this paper, we seek the answer for the following question: what is the optimum number of hops allowed for the reverse path hop length in WSNs? We created a novel mixed integer programming (MIP) framework to characterize the impact of reverse path hop length on WSN lifetime and performed extensive numerical analysis. Our results show that reverse path hop length has a significant impact on WSN lifetime.

A Simulation Based Performance Evaluation of AODV, R-AODV and PHR-AODV Routing Protocols for Mobile Ad Hoc Networks

Mobile Ad hoc Networks (MANETs) are characterized by open structure, lack of standard infrastructure and un-accessibility to the trusted servers. The performance of various MANET routing protocols is significantly affected due to frequently changing network topology, confined network resources and security of data packets. In this paper, a simulation based performance comparison of one of the most commonly used on-demand application oriented routing protocols, AODV (Ad hoc on-demand Distance Vector) and its optimized versions R-AODV (Reverse AODV) and PHR-AODV (Path hopping based Reverse AODV) has been presented. Basically the paper evaluates these protocols based on a wide set of performance metrics by varying both the number of nodes and the nodes maximum speed. A NS-2 based simulation study shows that, as compared to AODV and PHR-AODV, R-AODV enhances the packet delivery fraction by 15-20% and reduces the latency approximately by 50%. R-AODV requires lesser node energy for data transmission .

Analysis of Multipath Routing in Random Ad Hoc Networks Scenario

In this study, we have proposed a multipath routing protocol for Mobile Ad Hoc Networks. Multipath routing overcomes various problems that occur in data delivery through a single path. The proposed protocol selects multiple neighbor nodes of source node to establish multiple paths towards destination. These nodes are selected based on their minimum remaining distance from destination. We have computed the length of various paths and average hops count for different node density in the network. We have considered only three paths for our evaluation. The results show that path-2 gives better results in term of hop count and path length among three paths.

Syntheses and electrochemical properties of the Na-doped LiNi0.5Mn1.5O4 cathode materials for lithium-ion batteries

The novel Na-substituted Li1-xNaxNi0.5Mn1.5O4 has been synthesized to use as a cathode material for lithium ion battery via a solid-state method. Both crystal domain size and lattice parameter are influenced by the doping content of Na, without changing the basic spinel structure. The doping of Na ions not only increase the disordered distribution of nickel and manganese cations in spinel, but also increase two additional electron hopping paths, which contribute to a better charge transfer ability, relieve the ohmic polarization and electrochemical polarization of materials and improve lithium ion diffusion coefficient. After Na-doped, the discharge specific capacity rises up comparing to the sample without Na-doped. As a result, the excellent rate capability is achieved for the doping content of 5% Na in spinel, that the discharge capacity is increased by 3.4%, 9.4%, 9.1%, 8.7%, 6.5% and 3.4% in comparison with LNMO, presenting a discharge specific capacity of 121, 119.4, 118.5, 115.1, 108.4 and 101.3mAh·g−1 at the rates of 0.2, 0.5, 1, 2, 5 and 10C respectively, with tiny Mn3+ platform appearing. In addition, the sample presents a discharge capacity of 125mAh·g−1 at 1C, with a retention of 116.2mAh g−1 after 100 cycles. Even cycling at 5C rate and 55°C, the cell with 5% Na-doped LNMO cathode can has 82% of capacity retention after 400 cycles, indicating that it is a promising cathode material for lithium ion batteries.