Link Duration Research Articles

Novel self-adaptive routing service algorithm for application in VANET

As a special MANET (mobile ad hoc network), VANET (vehicular ad-hoc network) has two important properties: the network topology changes frequently, and communication links are unreliable. Both properties are caused by vehicle mobility. To predict the reliability of links between vehicles effectively and design a reliable routing service protocol to meet various QoS application requirements, in this paper, details of the motion characteristics of vehicles and the reasons that cause links to go down are analyzed. Then a link duration model based on time duration is proposed. Link reliability is evaluated and used as a key parameter to design a new routing protocol. Quick changes in topology make it a huge challenge to find and maintain the end-to-end optimal path, but the heuristic Q-Learning algorithm can dynamically adjust the routing path through interaction with the surrounding environment. This paper proposes a reliable self-adaptive routing algorithm (RSAR) based on this heuristic service algorithm. By combining the reliability parameter and adjusting the heuristic function, RSAR achieves good performance with VANET. With the NS-2 simulator, RSAR performance is proved. The results show that RSAR is very useful for many VANET applications.

The Impact of Link Duration on the Integrity of Distributed Mobile Networks

A major challenge in distributed mobile networks is network integrity, resulting from short link duration and severe transmission collisions. This paper analyzes the impact of link duration and transmission collisions on a range of on-the-fly authentication protocols, which operate based on predistributed keys and can instantly verify and forward messages. All unexpired messages within a link duration can be verified retrospectively, once the keys are matched on-the-air. We develop a new general 4D Markov model which, apart from the first three dimensions modeling a cycle of the protocols, is able to unprecedentedly capture unexpired messages between cycles in the fourth dimension. Validated by simulation, our analysis reveals that the on-the-fly authentication is efficient under short link duration, but is susceptible to transmission collisions. The authentication requires holistic cross-layer designs of retransmission and rekeying. The proposed model is able to facilitate the design of the protocol parameters, which allows the protocols to significantly outperform the state of the art.

VANSec: Attack-Resistant VANET Security Algorithm in Terms of Trust Computation Error and Normalized Routing Overhead

VANET is an application and subclass of MANETs, a quickly maturing, promising, and emerging technology these days. VANETs establish communication among vehicles (V2V) and roadside infrastructure (V2I). As vehicles move with high speed, hence environment and topology change with time. There is no optimum routing protocol which ensures full-pledge on-time delivery of data to destination nodes, and an absolutely optimum scheme design for flawless packet exchange is still a challenging task. In VANETs, accurate and on-time delivery of fundamental safety alert messages (FSAMs) is highly important to withstand against maliciously inserted security threats affectively. In this paper, we have presented a new security-aware routing technique called VANSec. The presented scheme is more immune and resistive against different kinds of attacks and thwarts malicious node penetration attempts to the entire network. It is basically based on trust management approach. The aim of the scheme is to identify malicious data and false nodes. The simulation results of VANSec are compared with already existing techniques called trust and LT in terms of trust computation error (TCE), end-to-end delay (EED), average link duration (ALD), and normalized routing overhead (NRO). In terms of TCE, VANSec is 11.6% and 7.3% efficient than LT and trust, respectively, while from EED comparison we found VANSec to be 57.6% more efficient than trust and 5.2% more efficient than LT. Similarly, in terms of ALD, VANSec provides 29.7% and 7.8% more stable link duration than trust and LT do, respectively, and in terms of NRO, VANSec protocol has 27.5% and 14% lesser load than that of trust and LT, respectively.

T134. Quantifying dynamical interactions between neural assemblies

Introduction There is accumulating evidence that brain function is strongly dependent on dynamic interactions between neural assemblies. Several methods, based on synchronization measures, are used to quantify functional connectivity between neural networks. However, despite the dynamic nature of neuronal interactions, functional connectivity is typically expressed as a mean value during the period of observation. In the present work, we characterize and quantify the spatiotemporal dynamics of these interactions using common instantaneous frequencies between different recording positions. We explore this approach in two conditions: wakefulness and generalized anesthesia. Methods We used 19-channel EEGs from patients who underwent a carotid endarterectomy during general anesthesia with propofol. Pre-operative 20 min EEGs were also available. All recordings were obtained as part of our routine care. All EEGs were recorded with Ag/AgCl electrodes with a sampling frequency of 250 Hz. EEGs were decomposed in the time-frequency plane by a short time Fourier transform. Subsequently, we used the ridge transform to subtract instantaneous frequencies from the local maxima in the time-frequency plane. The resulting ridge plots allow analysis of common instantaneous frequencies between different oscillators. We now define a link rate (LR) and a link duration (LD) for quantifying the frequency and duration of interactions, respectively. We illustrate this approach for different frequency bands (delta, theta, alpha and beta), using the EEG recordings during the eyes closed wake state and general anesthesia. Results EEGs from 21 patients were used. Link rates in the theta, alpha and beta band were significantly higher during anesthesia than during wakefulness (3.65–5.34 Hz during anesthesia, 3.51–4.55 Hz during wakefulness, p ≪ 0.05), while the link rates in the delta band were significantly lower during anesthesia (2.49 Hz during anesthesia, 2.96 Hz during wakefulness, p ≪ 0.05). The link durations in the delta and beta band were significantly shorter during anesthesia (158–124 ms during anesthesia, 168–129 ms during wakefulness, p ≪ 0.05), while those in the theta and alpha band were significantly higher (151–169 ms during anesthesia, 149–160 ms during wakefulness, p ≪ 0.05). Conclusion We present a method to characterize dynamic interactions between neural networks in the brain. A next step is to include phase information to limit volume conduction effects. Despite this limitation, we further show that link durations in most frequency bands decrease during anesthesia, supporting the notion that in this condition ‘neural integration’ is reduced.

A Link-Stability-Based Interest-Forwarding Strategy For Vehicular Named Data Networks

In recent years, the Vehicular Named Data Network (VNDN) architecture has been proposed to face performance and reliability challenges from IP/host centric Vehicular Ad hoc Networks. The constant mobility of nodes in such networks can result in rapid flooding of unsatisfied interest packets thus leading to network overloads. In this article, we proposed LSIF, a Link Stability-based Interest Forwarding strategy that relies on predictions of link durations to reduce the number of interest and data packets. The simulation results revealed LSIFs benefits. It outperformed existing approaches in both urban and highway VNDN scenarios by significantly reducing interest and data packets but preserving good levels of interest satisfaction rates and low round-trip times.

The Dynamical Prediction of V2V Link Duration in Urban VANETs

The Dynamical Prediction of V2V Link Duration in Urban VANETs

Link Duration Analysis of Entity Mobility Models in the Network of Moving Objects

In this research article, the Probability Density Function of Link Duration has been analysed by using three mobility models in the networks of moving objects. Link duration is a derived metric of graph theory. For the analysis, two well-known along with a proposed mobility model has been selected. Several performance criteria have been considered for the study including speed of node, Transmission range, node density, simulation area and computational complexity regarding time. The robustness, reliability of the proposed schemes have been examined by using Monte Carlo simulations and their statistical analysis. The real advantage of the proposed plan is to study the entity based mobility of objects which do not show much variance of angle and direction in their movement style (like vehicles on the highway). This model provides ease of implementation due to the simplicity of the code and concept in entity mobility models. Keywords: Ad-hoc Networks, Connectivity, Link Duration, Mobility Models, Monte Carlo Simulations

Novel routing protocol scheme for real-time applications in mobile Ad Hoc networks

In mobile Ad Hoc networks (MANETs), flooding-based route discovery is usually preferred in order to set up the route with reliability between transmission pair. However, this approach may cause a serious contention in transmission between adjacent nodes and a considerable amount of control packets. In addition, most of Ad Hoc routing protocols establish the route with minimum hop count. Consequently, the performance of Ad Hoc routing protocol is considerably affected by link (or route) duration since the network comprises the nodes with unrestricted mobility and constrained range in transmission. This paper proposes novel routing protocol that aims to (1) minimize routing overhead in route discovery procedure, and (2) guarantee a reliable and fast packet delivery between source and destination, especially in providing real-time applications over MANETs. To achieve this objective, we introduce relay region (RR) within the transmission range of nodes in order to select optimal next relaying nodes for supporting specific application requirements in route discovery procedure. The RR is defined by the limited distance progress in transmission to next relaying node in order to maintain the established route for an arbitrary length of time (i.e., route duration) while meeting packet delivery reliability and delay constraints. In performance evaluation, the simulation results showed that the proposed scheme can significantly improve the performance in comparison with the previous routing algorithms in terms of packet delivery ratio and packet delivery latency, reducing transmission redundancy in route discovery procedure.

An efficient routing protocol for the QoS support of large‐scale MANETs

SummaryThe hierarchical routing algorithm is categorized as a kind of routing method using node clustering to create a hierarchical structure in large‐scale mobile ad hoc network (LMANET). In this paper, we proposed a new hierarchical clustering algorithm (HCAL) and a corresponded protocol for hierarchical routing in LMANET. The HCAL is designed based on a cost metric in the form of the link expiration time and node's relative degree. Correspondingly, the routing protocol for HCAL adopts a reactive protocol to control the existing cluster head (CH) nodes and handle proactive nodes to be considered as a cluster in LMANET. Hierarchical clustering algorithm jointly utilizes table‐driven and on‐demand routing by using a combined weight metric to search dominant set of nodes. This set is composed by link expiration time and node's relative degree to establish the intra/intercommunication paths in LMANET. The performance of the proposed algorithm and protocol is numerically evaluated in average end‐to‐end delay, number of CH per round, iteration count between the CHs, average CH keeping time, normalized routing overhead, and packet delivery ratio over a number of randomly generated benchmark scenarios. Furthermore, to corroborate the actual effectiveness of the HCAL algorithm, extensive performance comparisons are carried out with some state‐of‐the‐art routing algorithms, namely, Dynamic Doppler Velocity Clustering, Signal Characteristic‐Based Clustering, Dynamic Link Duration Clustering, and mobility‐based clustering algorithms.

Multiple QoS Parameters-Based Routing for Civil Aeronautical Ad Hoc Networks

Aeronautical ad hoc network (AANET) can be applied as in-flight communication systems to allow aircraft to communicate with the ground, in complement to other existing communication systems to support Internet of Things. However, the unique features of civil AANETs present a great challenge to provide efficient and reliable data delivery in such environments. In this paper, we propose a multiple quality of service parameters-based routing protocol (MQSPR), to improve the overall network performance for communication between aircraft and the ground. The proposed MQSPR integrates path availability period, residual path load capacity and path latency in route selection and presents a broadcast optimization scheme to minimize flooding. The primary aim of MQSPR is to maintain long link durations, achieve path load balancing and reduce end-to-end delay to satisfy the requirements of civil aviation communication services. The simulation scenario and real-world scenario are set up, respectively, and the experimental results show that the proposed MQSPR can achieve high ground connectivity while effectively increase the path durations, improve the packet delivery ratio and perform the path load balancing. In addition, the flexibility of MQSPR is demonstrated by considering weighting factors of path selection parameters.

Performance Modeling of Link Duration in Vehicular Ad Hoc Networks Under Weibull Fading Channel Conditions

This paper presents an analytical model for the probability density function of link duration in vehicular ad hoc networks by considering the vehicle-to-vehicle channel to undergo Weibull fading. Assuming free flow traffic state and the vehicle speed to be uniformly distributed, we analyse the dependence of various parameters on link duration and its PDF. We perform Kolmogorov–Smirnov test and establish that the probability distribution of link duration can be approximated as exponential.

Integrity-Oriented Content Offloading in Vehicular Sensor Network

In this paper, an integrity-oriented content offloading ( ICO ) problem with variable modulation and coding schemes is proposed for relay-assisted vehicular sensor network. To accurately describe the link duration properties, a finite-state Markov chain-based model is built by jointly considering the mobility and radio propagation characteristics. Considering the ICO problem is NP-hard, our solution divides it into two offloading sub-problems with direct link and relay-assisted path, respectively. These two sub-problems are solved heuristically, and the corresponding results are combined to achieve a near-optimal result as the ICO scheme. While the analytical model is validated by Monte Carlo simulations and chi-square goodness fit test, the performance of our proposed ICO scheme is verified through simulations and comparisons, showing that our ICO solution can reduce the integral content offloading time compared with two other selected schemes and an upper performance bound.

Efficient and Stable Routing Algorithm Based on User Mobility and Node Density in Urban Vehicular Network.

Vehicular ad hoc networks (VANETs) are considered an emerging technology in the industrial and educational fields. This technology is essential in the deployment of the intelligent transportation system, which is targeted to improve safety and efficiency of traffic. The implementation of VANETs can be effectively executed by transmitting data among vehicles with the use of multiple hops. However, the intrinsic characteristics of VANETs, such as its dynamic network topology and intermittent connectivity, limit data delivery. One particular challenge of this network is the possibility that the contributing node may only remain in the network for a limited time. Hence, to prevent data loss from that node, the information must reach the destination node via multi-hop routing techniques. An appropriate, efficient, and stable routing algorithm must be developed for various VANET applications to address the issues of dynamic topology and intermittent connectivity. Therefore, this paper proposes a novel routing algorithm called efficient and stable routing algorithm based on user mobility and node density (ESRA-MD). The proposed algorithm can adapt to significant changes that may occur in the urban vehicular environment. This algorithm works by selecting an optimal route on the basis of hop count and link duration for delivering data from source to destination, thereby satisfying various quality of service considerations. The validity of the proposed algorithm is investigated by its comparison with ARP-QD protocol, which works on the mechanism of optimal route finding in VANETs in urban environments. Simulation results reveal that the proposed ESRA-MD algorithm shows remarkable improvement in terms of delivery ratio, delivery delay, and communication overhead.

Research on link duration for mobile multihop communication networks

Mobile multihop communication network is an important branch of modern mobile communication system, and is an important technical support for ubiquitous communication. The random movement of the nodes makes the networking be more flexible, but the frequently changing topology will decrease the link duration between nodes significantly, which will increase the packets loss probability and affect the network communication performance. Aiming at the problem of declining link duration caused by nomadic characteristics in mobile multihop communication network, four link duration models for possible moving states are established based on different features in real networking process in this paper, which will provide reliable criterion for the optimal routing selection. Model analysis and simulation results show that the reliable route established by the proposed model will effectively extend the link duration, and can enhance the global stability of the mobile multihop information transmission, so as to provide new option to transmission reliability improvement for the mobile communication network.

T-VNets: A novel trust architecture for vehicular networks using the standardized messaging services of ETSI ITS

In this paper we propose a novel trust establishment architecture fully compliant with the ETSI ITS standard which takes advantage of the periodically exchanged beacons (i.e. CAM) and event triggered messages (i.e. DENM). Our solution, called T-VNets, allows estimating the traffic density, the trust among entities, as well as the dishonest nodes distribution within the network. In addition, by combining different trust metrics such as direct, indirect, event-based and RSU-based trust, T-VNets is able to eliminate dishonest nodes from all network operations while selecting the best paths to deliver legal data messages by taking advantage of the link duration concept. Since our solution is able to adapt to environments with or without roadside units (RSUs), it can perform adequately both in urban and highway scenarios. Simulation results evidence that our proposal is more efficient than other existing solutions, being able to sustain performance levels even in worst-case scenarios.

ELDP: Extended Link Duration Prediction Model for Vehicular Networks

Link duration between two vehicles is considered an important quality of service metric in designing a network protocol for vehicular networks. There exist many works that study the probability density functions of link duration in a vehicular network given various vehicle mobility models, for example, the random waypoint model. None of them, however, provides a practical solution to estimating the link duration between two vehicles on the road. This is in part because link duration between vehicles is affected by many factors including the distance between vehicles, their turning directions at intersections, and the impact of traffic lights. Considering these factors, we propose the extended link duration prediction (ELDP) model which allows a vehicle to accurately estimate how long it will be connected to another vehicle. The ELDP model does not assume that vehicles follow certain mobility models; instead, it assumes that a vehicle's velocity follows the Normal distribution. We validate the ELDP model in both highway and city scenarios in simulations. Our detailed simulations illustrate that relative speed between vehicles plays a vital role in accurately predicting link duration in a vehicular network. On the other hand, we find that the turning directions of a vehicle at intersections have subtle impact on the prediction results.

Belief Propagation-Based Cognitive Routing in Maritime Ad Hoc Networks

Cognitive routing for maritime wireless ad hoc networks is proposed in this paper to find a stable path between source and destination. This is ship-to-ship communication where two ships can communicate when they not only have consensus on a common idle channel but also are in the transmission range of each other. We apply belief propagation algorithm for collaborative spectrum sensing. Every user (ship) exchanges its local decisions with its neighbors to compute the final belief about the state of the channel. These beliefs are applied for estimating the link duration for total number of hops between source and destination. Then, a path is selected which maximizes the path duration among all the paths in the network to reach the destination. We apply both flood-based and geographical routing protocols to find a route between source and destination for different scenarios. We simulate our scheme for different ocean settings and evaluate path durations for different number of ships. The results report a significant increase in path duration as the number of nodes increases in the network. In addition, we verify that path duration increases with an increase in probability of primary user being idle via extensive simulations. Hence, our scheme provides stable path selection for communication among users onboard.

Congestion Avoidance and Delay Minimization in Energy Aware Routing of Dynamic ieee 802.11s WMN

Minimization of delay in collecting the data at any base stations is one of the major concerns in cluster based Wireless Mesh Networks. several researches have proposed algorithms to control congestion considering static nature of a node. Mobility of a node results in high congestion due to frequent link breakages and high energy consumption due to re-establishment of route during routing process. Hence, the authors consider dynamic nodes with single hop inside the static cluster. The proposed model includes four modules namely, Cluster head selection, slot allocation, slot scheduling and data collection process. the cluster head selection is based on the maximum energy, number of links and link duration. Slot allocation is based on the available energy () and the required energy (). Slot scheduling is carried out based on the link duration. Data at the base station will be collected as they are scheduled. Model is tested using Network Simulator-3 (NS3) and results indicate that the proposed model achieves least delay besides reducing the congestion compared to the existing methods.

Link connectivity under more realistic channel model for vehicle-to-vehicle communications

Since the antennas are very low in vehicle-to-vehicle V2V scenarios, the communication link is easily blocked by other vehicles. The shadowing effect caused by other vehicles has been ignored in most of the existing V2V channel models, and it is thus neglected in the system performance evaluation. By incorporating channel state transition with a measurement-based dual-slope path loss model, an obstacle-based model is presented in this paper for the V2V highway scenarios to capture the dynamic characteristics of radio channels, in the presence of other vehicles as moving obstacles. The joint effects of the radio environment and traffic flow on link connectivity are mainly investigated. The obstruction probability is represented, and the connectivity-related metrics are evaluated: inter-vehicle connectivity probability and link duration. All the analytical results are validated by extensive simulations under the measurement-based path loss model, and are also compared to the existing models.

Routing and Wavelength Assignment in a Satellite Optical Network Based on Ant Colony Optimization With the Small Window Strategy

Ant colony optimization (ACO) with the small window strategy is put forward to solve the routing and wavelength assignment problem in satellite optical networks. The intersatellite distance, link duration, and wavelength idle ratio are introduced as the heuristic functions, and the small window strategy is used to promote the convergence speed. By calculating the intersection of idle wavelengths on adjacent links, the algorithm can accomplish routing selection and wavelength assignment on a single ant. The results show that, compared with the Dijkstra+FF algorithm, the blocking probability of ACO can decrease by 50% at most, and improvement of the resource utilization ratio can reach 45%.