Connectivity Resilience Research Articles

Network Connectivity Resilience in Next Generation Backhaul Networks: Challenges and Future Opportunities

Network Connectivity Resilience in Next Generation Backhaul Networks: Challenges and Future Opportunities

The Ecological Risks in Arid Zones from a Production–Living–Ecological Space Perspective: A Case Study of the Tuha Region in Xinjiang, China

The ecological and environmental problems of arid zones have become an urgent global concern. Current research on ecological risk is based mainly on the dominant functions of land use, with a primary focus on land use landscape projections and less consideration of potential risks to ecosystems, system resilience and interactions between nature and future sustainable development. In this study, a potential–connectivity–resilience ecological risk assessment model based on the SDGs was constructed using multisource data to spatially quantify indicators at the grid scale in the Turpan and Hami regions of Xinjiang, China. This model was used as a basis for studying ecological risk in arid zones from a production–living–ecological space (PLES) perspective. The results revealed that, during the period 2000–2020, PLESs in the Turpan and Hami regions presented significant spatial similarity, with an increasing trend in overall risk. The production space in the Turpan and Hami regions showed a parabolic trend of increasing and then decreasing, whereas the living space and ecological space in the Hami region showed continuous linear upward trends. The state of ecological security in the Turpan and Hami regions is gradually deteriorating, and comprehensive ecological protection and restoration measures are urgently needed to rationally allocate the structure and layout of the production-–living-–ecological space. The study of ecological risk from a PLES perspective not only helps in fully understanding the development trend of the arid zone; it also provides new ideas and methods for evaluating regional ecological environmental safety and scientific references for formulating regional sustainable development, ecological risk prevention and control and the rational allocation of resources.

Expanding China’s protected areas network to enhance resilience of climate connectivity

Expanding the network of connected and resilient protected areas (PAs) for climate change adaptation can help species track suitable climate conditions and safeguard biodiversity. This is often overlooked when expanding PAs and quantifying their benefits, resulting in an underestimate of the benefits of expanding PAs. We expanded PAs through terrestrial mammalian species distribution hotspots, Key Biodiversity Areas (KBAs), and wilderness areas. Then, we constructed climate connectivity networks using a resistance-based approach and further quantified the network resilience to propose resilient climate response strategies in China. The results showed that existing PAs suffered from location biases with important biodiversity areas. The existing PAs represented about half of the KBAs and wilderness areas, yet only 12.08% of terrestrial mammalian species distribution hotspots were located within existing PAs. Compared with the existing PA network, the network efficiency and resilience of the expanded PAs’ climate connectivity increased to 1.80 times and 1.78 times, respectively. With 56% of the nodes remaining, the network efficiency of the expanded PAs was equivalent to that of the existing PAs with all nodes. The network resilience of preferentially protecting and restoring low human footprint patches was approximately 1.5–2 times that of the random scenario. These findings highlighted that confronted with the unoptimistic situation of global warming, nature conservation based on existing PAs was no longer optimal. It was critical to construct a connected and resilient conservation network relying on both important biodiversity areas and low human footprint patches.

Optimizing Network Reliability in Dynamic or Rapidly-Changing Topologies

With communication, power and transportation networks facing ever-greater dynamics, optimizing reliability poses significant modeling and computational challenges. Most existing reliability optimization research assumes static topologies with predefined failure probabilities and connectivity demands. This work puts forth a time-varying mathematical program to maximize expected network reliability under shifting topological uncertainties. Sets, parameters, decision variables and constraints are defined as functions of time to capture variability in links, capacities, risks and demands. The formulation adapts to detected changes through re-optimization triggered by model error thresholds. Approximation techniques based on constraint sampling and decomposition address solve efficiency for large fluid networks. Evaluations on simulated dynamic test cases demonstrate superior reliability versus periodic and static optimization approaches while fulfilling budget limits. Accuracy metrics assess model fidelity over increasing volatility levels. Implementation case studies exhibit optimized resilience in software-defined communication architectures, smart grid reconfiguration, and adaptive transportation maintenance scenarios. The mathematical programming foundation provides a pathway to achieve connectivity resilience for critical infrastructure networks facing intensifying dynamics. The integration of optimization, prediction and adaptive response provides a paradigm for decision making under modern uncertain conditions.

Provision of maximum connectivity resiliency with minimum cost to telecommunication networks through third‐party networks

AbstractIn telecommunication networks, full connectivity resilience to multiple link failures is too costly as it requires a network topology with too many redundant links. Alternatively, the connectivity resilience of a telecommunications network can be improved by resorting to available third‐party networks for temporary additional connectivity until the failing links are restored. In this approach, some nodes of the network must be selected in advance to act as gateway nodes to the third‐party networks when a multiple link failure event occurs. For a given network topology and a cost associated with each node to turn it into a gateway node to each of the third‐party networks, the aim is to select the gateway nodes providing maximum connectivity resilience at minimum cost. The Gateway Node Selection is defined as a bi‐objective optimization problem such that its Pareto‐optimal solutions represent different trade‐offs between cost and connectivity resilience. In this work, the connectivity resilience is modeled by the Critical Link Detection optimization problem. An exact optimization algorithm is proposed, based on a row generation algorithm and on set cover cuts. The computational results demonstrate the effectiveness of the proposed algorithm on four well‐known telecommunication network topologies.

Whether weather causes contention: assessing the ongoing resilience opportunity of telecommuting

The Covid-19 pandemic resulted in an unprecedented overnight explosion in telecommuting. It has highlighted a new dependence on digital infrastructures and raised new questions regarding the resilience of internet connectivity as an alternative to travel. Pre-pandemic, we considered how telecommuting could offer an opportunity for resilience when travel was disrupted by weather extremes. We analysed five years’ of recorded broadband speed variation across England and Wales in order to quantify the changing demand for internet access during the working day under adverse weather conditions. Slower broadband speeds, also known as contention, are an indication of increased demand. Thus, during the working day, contention is an indication that external factors like weather can influence the choice to telecommute instead of travel. A multilevel regression model is estimated to investigate the relationship between contention during the working day and weather, whilst controlling for background spatial and demographic differences in internet services. Emergent patterns suggest that even before the pandemic, online connectivity was in greater demand when travel was disrupted or at risk of disruption. Our research provides insights into the roles that both the supply of and the demand for transport and digital technologies might play in increasing resilience and maintaining productivity during severe weather and other disruptions as experience of both types of working has become so widespread.

Resilient steel beam-column connection with bolted compact hollow structural steel damper

This study proposes a resilience-based design approach that considers the correlation between the resilience response of self-centering post-tensioned (SCPT) steel beam to column connections and the inelastic performance of the required energy dissipation (ED) system. A compact circular hollow steel tube (CHST) is proposed as a replaceable ED system. On the basis of existing experimental results, a detailed three-dimensional finite element modeling (3D-FEM) was carried out to identify the response of the compact CHST under half cyclic loading. A large number of numerical works ended with the extraction of design charts to determine the axial strain (ΔL/L) of the ED system before encountering post-yield buckling and/or excessive strength degradation. Accordingly, in a numerical validated reference SCPT connection, several predesigned ED systems were implemented for simulation. As a result, according to the design charts, the optimum selection of proper inherent depth to thickness (D/t) ratio and length to depth (L/D) ratio of the CHST-ED system can increase the resilience of modern self-centering steel structures. In addition, the improvement of the entire connection resilience is associated with the development of satisfactory energy dissipation capacity. Furthermore, the superior performance of the connection under sequential cyclic loading promotes the application of the proposed SCPT-ED connection in a resilient structural system.

Regulative distance, international connectivity and innovation systems: Turkey’s links to the EU

PurposeThe purpose of this study is to assess the effect of institutional distance on national innovation systems.Design/methodology/approachThis study uses social network analysis to analyze the connectivity between national systems of innovation. A regulative distance index is constructed by coding the European Commission progress reports and using weights to account for relevance to research and innovation.FindingsReductions in institutional distance (proxied by regulative distance) increase international innovation connectivity between national systems of innovation. More importantly, it leads to increase in both the complexity and resilience of innovation connectivity between countries.Originality/valueThis study provides fresh evidence on the pathways through which institutions affect international business systems. Policy harmonization has strong effects on firm-level corporate strategy.

Combining ensemble models and connectivity analyses to predict wolf expected dispersal routes through a lowland corridor

The Italian wolf (Canis lupus italicus) population has remained isolated South of the Alps for the last few thousand years. After a strong decline, the species has recolonized the Apennines and the Western Alps, while it is currently struggling to colonize the Eastern Alps. Recently, the species was detected in a lowland park connecting the Northern Apennines to the Central Alps. If the park was able to sustain a net wolf dispersal flow, this could significantly boost the connection with the Eastern Alps and the Dinaric-Balkan population. We investigated the suitability of the park as a functional ecological corridor for the wolf through the unhospitable lowland of Northern Italy. We collected wolf occurrence data in two study areas. We modeled species distribution running a separate ensemble model for each study area and then merging the output of the models to obtain an integrated suitability map. We used this map to identify corridors for the wolf adopting a factorial least-cost path and a cumulative resistant kernel approach. The connectivity models showed that only two corridors exist in the lowland areas between the Northern Apennines and the Central Alps. The Western corridor is a blind route, while the eastern corridor passes through the park and has a continuous course. However, the models also revealed a scarce resilience of corridor connectivity in the passageways between the park and the Apennines and the Prealps, which suggests that urgent management actions are necessary to ensure the future functionality of this important corridor.

On Resilience of Connectivity in the Evolution of Random Graphs

In this note we establish a resilience version of the classical hitting time result of Bollobás and Thomason regarding connectivity. A graph $G$ is said to be $\alpha$-resilient with respect to a monotone increasing graph property $\mathcal{P}$ if for every spanning subgraph $H \subseteq G$ satisfying $\deg_H(v) \leqslant \alpha \deg_G(v)$ for all $v \in V(G)$, the graph $G - H$ still possesses $\mathcal{P}$. Let $\{G_i\}$ be the random graph process, that is a process where, starting with an empty graph on $n$ vertices $G_0$, in each step $i \geqslant 1$ an edge $e$ is chosen uniformly at random among the missing ones and added to the graph $G_{i - 1}$. We show that the random graph process is almost surely such that starting from $m \geqslant (\tfrac{1}{6} + o(1)) n \log n$, the largest connected component of $G_m$ is $(\tfrac{1}{2} - o(1))$-resilient with respect to connectivity. The result is optimal in the sense that the constants $1/6$ in the number of edges and $1/2$ in the resilience cannot be improved upon. We obtain similar results for $k$-connectivity.

Feedback-Based Path Failure Detection and Buffer Blocking Protection for MPTCP

A multipath TCP (MPTCP) is a promising protocol that has been standardized by the Internet Engineering Task Force to support multipath operations in the transport layer. However, although the MPTCP can provide multiple transmission paths and aggregate the bandwidth of multiple paths, it does not consistently achieve more throughput (goodput) nor a greater connection resilience. Currently, the MPTCP is vulnerable to path failure or underperforming subflows, which cause transmission interruption or throughput (goodput) degradation. Unfortunately, there is no exact rule for declaring a path failure or preventing the usage of underperforming subflows in the MPTCP. In this paper, we propose a novel path failure detection method referred to as feedback-based path failure (FPF) detection. In addition, we propose a new decision method called buffer blocking protection (BBP) to address the underperforming subflows for the MPTCP. Measurement results indicate that the FPF detection reduces transmission interruption time by the fast path failure decision, which can prevent duplicate transmission interruption events and unnecessary retransmissions. Furthermore, the FPF detection is sufficiently robust in terms of packet loss and the delay difference between paths. The results additionally show that the BBP method prevents goodput degradation due to underperforming subflows. Consequently, the MPTCP with the BBP method can at least achieve the throughput performance of a single Transmission Control Protocol (TCP), which uses the best path regardless of the delay difference between paths.

Long-term acclimatization to high-altitude hypoxia modifies interhemispheric functional and structural connectivity in the adult brain.

BackgroundStructural and functional networks can be reorganized to adjust to environmental pressures and physiologic changes in the adult brain, but such processes remain unclear in prolonged adaptation to high‐altitude (HA) hypoxia. This study aimed to characterize the interhemispheric functionally and structurally coupled modifications in the brains of adult HA immigrants.MethodsWe performed resting‐state functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) in 16 adults who had immigrated to the Qinghai‐Tibet Plateau (2300–4400 m) for 2 years and in 16 age‐matched sea‐level (SL) controls. A recently validated approach of voxel‐mirrored homotopic connectivity (VMHC) was employed to examine the interhemispheric resting‐state functional connectivity. Areas showing changed VMHC in HA immigrants were selected as regions of interest for follow‐up DTI tractography analysis. The fiber parameters of fractional anisotropy and fiber length were obtained. Cognitive and physiological assessments were made and correlated with the resulting image metrics.ResultsCompared with SL controls, VMHC in the bilateral visual cortex was significantly increased in HA immigrants. The mean VMHC value extracted within the visual cortex was positively correlated with hemoglobin concentration. Moreover, the path length of the commissural fibers connecting homotopic visual areas was increased in HA immigrants, covarying positively with VMHC.ConclusionsThese observations are the first to demonstrate interhemispheric functional and structural connectivity resilience in the adult brain after prolonged HA acclimatization independent of inherited and developmental effects, and the coupled modifications in the bilateral visual cortex indicate important neural compensatory mechanisms underlying visual dysfunction in physiologically well‐acclimatized HA immigrants. The study of human central adaptation to extreme environments promotes the understanding of our brain's capacity for survival.

The seed bank as a mechanism for resilience and connectivity in a seasonal unregulated river

The seed bank of a seasonally flowing river was sampled to assess ecosystem resilience and evidence of connectivity. Seed banks were sampled from ‘Floodplain’, ‘Top of Bank’ and ‘In Channel’ hydrogeomorphic areas in seven reaches of the Wannon River, and the distribution of species and water plant functional groups (WPFGs) among these sites was assessed. The seed bank material was exposed to two treatments (damp and flooded) to stimulate germination of terrestrial (Tdr Tda), flooding-tolerant (ATe, ATl, ARp, ATw) and flooding-dependent (ARf, Se, Sr, Sk) species. There was a high degree of similarity among seed banks from all parts of the river, and all hydrogeomorphic areas. Few species were restricted to any one area (i.e., ‘In Channel’, ‘Top of Bank’, ‘Floodplain’) or any one reach of the river. This indicates that the wetland areas of the Wannon River have a high degree of longitudinal and lateral connectivity, and the riparian zone retains the capacity to provide resources to wetland fauna, even with large variation in the natural flow regime and long-term agricultural land-use. Provided the seed bank remains intact, the perennial vegetation is allowed to regenerate, and a natural flow regime is maintained, seasonal rivers like the Wannon are likely to be resilient to the consequences of climate change, despite the surrounding agricultural land-use and the influx of saline ground-water.

Assessing and safeguarding network resilience to nodal attacks

This article introduces new methods for evaluating and improving resilience of network connectivity to attacks on nodes of the network. Network connectivity is evaluated using a centrality measure that quantifies sensitivity of the size of the largest connected component to node removals. Based on this centrality measure, a new method for improving resilience is introduced, called edge rewiring. The topology of the power grid of western U.S. states is used to illustrate the proposed method. Using the proposed centrality measure, we show that the power grid topology is especially vulnerable to nodal attacks. In particular, using the proposed centrality measure, an attacker could reduce the largest component size by nearly a factor of two by only targeting 0.2 percent of the nodes. More importantly, we show that network resilience can be greatly improved via a few edge rewires without introducing additional edges in the network.

Online Authentication and Key Establishment Scheme for Heterogeneous Sensor Networks

In recent years, the adaptation of wireless sensor networks (WSNs) to application areas requiring mobility increased the security threats against confidentiality, integrity, and privacy of the information as well as against their connectivity. Since key management plays an important role in securing both information and connectivity, a proper authentication and key management scheme is required in mobility enabled applications where the authentication of a node with the network is a critical issue. In this paper, we present an authentication and key management scheme supporting node mobility in a heterogeneous WSN that consists of several mobile sensor nodes and a few fixed sensor nodes. We analyze our proposed solution by using the OMNET++ simulator to show that it requires less memory space and provides better connectivity and network resilience against node capture attacks compared to some existing schemes. We also propose two levels of secure authentication methods for the mobile sensor nodes for secure authentication and key establishment.

Distributed KDC-Based Random Pairwise Key Establishment in Wireless Sensor Networks

Key management is a core mechanism to provide secure and reliable communications in wireless sensor networks (WSNs). In large-scale WSNs, due to the resource constraint on sensor nodes, it is still an extremely challenging task to achieve good performance in terms of high network connectivity and strong resilience against sensor nodes capture with low overheads. To address this issue, in this paper we propose a novel random pairwise key establishment scheme, called RPKE. In RPKE, sensor nodes differentiate their roles as either auxiliary nodes or ordinary nodes prior to network deployment. The auxiliary nodes act as distributed key distribution center (KDC), and neighboring ordinary nodes can establish pairwise key with the help of the distributed KDC. Theoretical analysis and simulation evaluation demonstrate that RPKE performs well in terms of network connectivity and resilience at the cost of low computation/communication/storage overheads, compared to the existing counterparts.

An Adaptive Key Management Framework for the Wireless Mesh and Sensor Networks

Wireless sensor networks (WSNs) and wireless mesh networks (WMNs) are popular research subjects. The interconnection of both network types enables next-generation applications and creates new optimization opportunities. Currently, plenty of protocols are available on the security of either wireless sensor networks or wireless mesh networks, an investigation in peer work underpins the fact that neither of these protocols is adapt to the interconnection of these network types. The internal cause relies on the fact that they differ in terms of complexity, scalability and network abstraction level. Therefore, in this article, we propose a unified security framework with three key management protocols, MPKM, MGKM, and TKM which are able to provide basic functionalities on the simplest devices and advanced functionalities on high performance nodes. We perform a detailed performance evaluation on our protocols against some important metrics such as scalability, key connectivity and compromise resilience, and we also compare our solution to the current keying protocols for WSNs and WMNs.