Randomization Adaptive Self-Stabilization

We present a scheme to convert self-stabilizing algorithms that use randomization during and following convergence to self-stabilizing algorithms that use randomization only during convergence. We thus reduce the number of random bits from an infinite number to a bounded number. The scheme is applicable to the cases in which there exits a local predicate for each node, such that global consistency is implied by the union of the local predicates. We demonstrate our scheme over the token circulation algorithm of Herman and the recent constant time Byzantine self-stabilizing clock synchronization algorithm by Ben-Or, Dolev and Hoch. The application of our scheme results in the first constant time Byzantine self-stabilizing clock synchronization algorithm that uses a bounded number of random bits

Design and analysis of adaptive hierarchical low-power long-range networks

A new phase of evolution of Machine-to-Machine (M2M) communication has started where vertical Internet of Things (IoT) deployments dedicated to a single application domain gradually change to multi-purpose IoT infrastructures that service different applications across multiple industries. New networking technologies are being deployed operating over sub-GHz frequency bands that enable multi-tenant connectivity over long distances and increase network capacity by enforcing low transmission rates to increase network capacity. Such networking technologies allow cloud-based platforms to be connected with large numbers of IoT devices deployed several kilometres from the edges of the network. Despite the rapid uptake of Long-power Wide-area Networks (LPWANs), it remains unclear how to organize the wireless sensor network in a scaleable and adaptive way. This paper introduces a hierarchical communication scheme that utilizes the new capabilities of Long-Range Wireless Sensor Networking technologies by combining them with broadly used 802.11.4-based low-range low-power technologies. The design of the hierarchical scheme is presented in detail along with the technical details on the implementation in real-world hardware platforms. A platform-agnostic software firmware is produced that is evaluated in real-world large-scale testbeds. The performance of the networking scheme is evaluated through a series of experimental scenarios that generate environments with varying channel quality, failing nodes, and mobile nodes. The performance is evaluated in terms of the overall time required to organize the network and setup a hierarchy, the energy consumption and the overall lifetime of the network, as well as the ability to adapt to channel failures. The experimental analysis indicate that the combination of long-range and short-range networking technologies can lead to scalable solutions that can service concurrently multiple applications

Perception is Reality: Change Leadership and Work Engagement

Purpose The purpose of this paper is to investigate how employee perceptions of change and leadership might impact work engagement following major organizational change. Design/methodology/approach Social media invited US workers recently experiencing major organizational change to anonymously complete a web-based survey requesting qualitative and quantitative responses. Values-based coding and thematic analysis were used to explore qualitative data. Hierarchical and linear regression, and bootstrapped mediation were used to analyze quantitative data. Findings Analysis of qualitative data identified employees’ perceptions of ideal change and ideal leadership were well supported in the change leadership literature. Analysis of quantitative data indicated that employee perceptions of leadership fully mediated the relationship between employee perceptions of change and work engagement. Practical implications Study findings imply that how employees perceive change is explained by how they perceive leadership during change, and that these perceptions impact work engagement. Although these findings appear commonsensical, the less than stellar statistics on major organizational change may encourage leaders to become more follower-focused throughout the change process. Originality/value The study makes a contribution to an understudied area of organizational research, specifically applied information processing theory. This is the first study that identifies employee perceptions of leadership as a mediator for perceptions of change and work engagement. From a value perspective, leaders as successful change agents recognize significant cost savings in dollars and human welfare by maintaining healthy workplaces with highly engaged workers

How to Stop Disagreeing and Start Cooperatingin the Presence of Asymmetric Packet Loss

We consider the design of a disagreement correction protocol in multi-vehicle systems. Vehicles broadcast in real-time vital information such as position, direction, speed, acceleration, intention, etc. This information is then used to identify the risks and adapt their trajectory to maintain the highest performance without compromising the safety. To minimize the risk due to the use of inconsistent information, all cooperating vehicles must agree whether to use the exchanged information to operate in a cooperative mode or use the only local information to operate in an autonomous mode. However, since wireless communications are prone to failures, it is impossible to deterministically reach an agreement. Therefore, any protocol will exhibit necessary disagreement periods. In this paper, we investigate whether vehicles can still cooperate despite communication failures even in the scenario where communication is suddenly not available. We present a deterministic protocol that allows all participants to either operate a cooperative mode when vehicles can exchange all the information in a timely manner or operate in autonomous mode when messages are lost. We show formally that the disagreement time is bounded by the time that the communication channel requires to deliver messages and validate our protocol using NS-3 simulations. We explain how the proposed solution can be used in vehicular platooning to attain high performance and still guarantee high safety standards despite communication failures

Farming for Health: Aspects from Germany

Until now, the term ‘Farming for Health’ is unknown in Germany but it would cover a wide spectrum of different kinds of social agriculture already existing in Germany, such as farms that integrate disabled people or drug therapy into their farming system, or farms that integrate children, pupils or older people. Relevant work in Germany is done in ‘Sheltered Workshops’, where supporting and healing powers of farming and gardening are used for disabled people with a diversity of work possibilities. Relevant activities also take place in work-therapy departments using horticultural therapy and in animalassisted therapy. There are an estimated number of 1000 different projects for mentally ill, disabled and elderly people in hospitals, Sheltered Workshops, on farms and other projects in Germany with a multitude of individual work places. The upcoming idea of Farming for Health may be met by the term ‘multifunctionality’ as one of the future goals of agriculture: to combine the production of cash crops with social functions, like providing space for recreation, care for landscapes and care for disabled people. Research showed that farms that work together with clients in their farming system have more time and financial support to integrate aims like caring for biotopes and landscape measures into their work schedule

A virtual actuator approach for the secure control of networked LPV systems under pulse-width modulated DoS attacks

In this paper, we formulate and analyze the problem of secure control in the context of networked linear parameter varying (LPV) systems. We consider an energy-constrained, pulse-width modulated (PWM) jammer, which corrupts the control communication channel by performing a denial-of-service (DoS) attack. In particular, the malicious attacker is able to erase the data sent to one or more actuators. In order to achieve secure control, we propose a virtual actuator technique under the assumption that the behavior of the attacker has been identified. The main advantage brought by this technique is that the existing components in the control system can be maintained without need of retuning them, since the virtual actuator will perform a reconfiguration of the plant, hiding the attack from the controller point of view. Using Lyapunov-based results that take into account the possible behavior of the attacker, design conditions for calculating the virtual actuators gains are obtained. A numerical example is used to illustrate the proposed secure control strategy.Peer ReviewedPostprint (author's final draft

VCube-PS: A Causal Broadcast Topic-based Publish/Subscribe System

In this work we present VCube-PS, a topic-based Publish/Subscribe system built on the top of a virtual hypercube-like topology. Membership information and published messages are broadcast to subscribers (members) of a topic group over dynamically built spanning trees rooted at the publisher. For a given topic, the delivery of published messages respects the causal order. VCube-PS was implemented on the PeerSim simulator, and experiments are reported including a comparison with the traditional Publish/Subscribe approach that employs a single rooted static spanning-tree for message distribution. Results confirm the efficiency of VCube-PS in terms of scalability, latency, number and size of messages.Comment: Improved text and performance evaluation. Added proof for the algorithms (Section 3.4