Avoidance Scheme Research Articles

Close proximity formation flying via linear quadratic tracking controller and artificial potential function

A Riccati-based tracking controller with collision avoidance capabilities is presented for proximity operations of spacecraft formation flying near elliptic reference orbits. The proposed dynamical model incorporates nonlinear accelerations from an artificial potential field, in order to perform evasive maneuvers during proximity operations. In order to validate the design of the controller, test cases based on the physical and orbital features of the Prototype Research Instruments and Space Mission Technology Advancement (PRISMA) will be implemented, extending it to scenarios with multiple spacecraft performing reconfigurations and on-orbit position switching. The results show that the tracking controller is effective, even when nonlinear repelling accelerations are present in the dynamics to avoid collisions, and that the potential-based collision avoidance scheme is convenient for reducing collision threat.

P-024: Are admissions to hospital from an integrated health and social care hospital avoidance scheme preventable . . .

P-024: Are admissions to hospital from an integrated health and social care hospital avoidance scheme preventable . . .

An Adaptive WLAN Interference Mitigation Scheme for ZigBee Sensor Networks

We propose an adaptive interference avoidance scheme that enhances the performance of ZigBee networks by adapting ZigBees' transmissions to measured wireless local area network (WLAN) interference. Our proposed algorithm is based on a stochastic analysis of ZigBee operation that is interfered with by WLAN transmission, given ZigBee and WLAN channels are overlaid in the industrial, scientific, and medical (ISM) band. We assume that WLAN devices have higher transmission power than ZigBee devices. Then, the high transmission power of WLAN devices causes the capture effect when WLAN and ZigBee transmit simultaneously. On the other hand, ZigBee performs backoff during clear channel assessment (CCA) operation if the WLAN is transmitting its frames on the channel. We adopt a widely used WLAN queueing/transmission model that is based on a Markov chain concept. We model a ZigBee device's operation using the Markov chain that includes WLAN interference statistically derived from the WLAN queueing/transmission model. Our proposed algorithm is evaluated in a simulated ZigBee network in the presence of varying WLAN interference. Numerical results show that our WLAN interference mitigation scheme finds the ZigBee control parameters, among a candidate set, which enhances ZigBee network performance compared to the conventional ZigBee operation.

Distance-Based Stable Routing Decision Scheme in Urban Vehicular Ad Hoc Networks

A number of ad hoc routing protocols of vehicular ad hoc network (VANET) have been proposed and evaluated based on mobile ad hoc network (MANET) routing protocols. Although a large number of routing protocols have been developed in MANET, the VANET has different environments such as highly dynamic topology, frequently disconnected network, hard delay constraints for safety-related application, and various communications environments (e.g., highway or urban traffic scenarios). Therefore, development of a suitable routing protocol that considers these characteristics of VANET should be needed. In this paper we suggest the improved distance-based VANET routing protocol compared with the previous researches on urban traffic environments. We apply approaches to packet-collisions avoidance scheme in the intersection and to stable route decision scheme based on the adaptive waiting time. The performance is then evaluated under simulation which is implemented with the Manhattan urban traffic model. The results show the improved performance as compared with the previous researches.

무선 USB 시스템에서 간섭 회피를 위한 채널 스케쥴링 기법

Wireless universal serial bus (WUSB) is the USB technology merged with WiMedia PHY/MAC. WUSB can be applied to wireless persanal area network (WPAN) applications as well as PAN applications like wired USB. Because numerous WUSB networks operate independently for each application, data conflict can occur between adjacent networks. To avoid data conflict, the resource in a different time zone can be utilized. However, if devices in a network increase, available resources in the network decrease, and then the lack of resources necessary to provide service can occur. To solve this problem, we propose interference avoidance scheme for WUSB systems.

Virtual Impedance Control for Safe Human-Robot Interaction

Collision avoidance is essential for safe robot manipulation. Especially with humans around, robots should work only when safety can be robustly guaranteed. In this paper, we propose using virtual impedance control for reactive, smooth, and consistent collision avoidance that interferes minimally with the original task. The virtual impedance control operates in the risk space, a vector space describing the possibilities of all forthcoming collisions, and is designed to elude all risks in a consistent response in order to create assuring human-robot interaction experiences. The proposed scheme intrinsically handles kinematic singularity and the activation of avoidance using a boundary layer defined on the spectrum of Jacobian. In cooperation with the original controller, the proposed avoidance scheme provides a proof of convergence if the original controller is stable with and without projection. In simulations and experiments, we verified the characteristics of the proposed control scheme and integrated the system with Microsoft Kinect to monitor the workspace for real-time collision detection and avoidance. The results show that the proposed approach is suitable for robot operation with humans nearby.

Distributed Random Access Scheme for Collision Avoidance in Cellular Device-to-Device Communication

In this paper, we propose a fully-distributed random access protocol for the device-to-device (D2D) communication in a cellular network. The D2D communication can provide a significant capacity gain by enabling a cellular network to offload data traffic to direct communication links between devices (i.e., D2D link). However, a D2D link can generate serious interference to other D2D links as well as cellular devices without any proper interference control mechanism. Compared to centralized resource allocation and power control schemes for the D2D communication, a distributed scheme is advantageous in that it has smaller control overhead and is more responsive to traffic demands. To protect a D2D receiver, the proposed scheme employs a collision avoidance mechanism that creates an exclusion region around the D2D receiver, where interferers are prohibited from transmitting a signal. We analyze the proposed scheme by assuming that the locations of devices follow a Poisson point process. By simulation, we show that the analysis results accurately match the simulation results and that the proposed scheme outperforms a distributed D2D scheme without collision avoidance by a very wide margin.

Detouring dynamic routing holes in stationary wireless sensor networks in the presence of temporarily misbehaving nodes

Summary In this work, we propose a scheme, named BRIDGE, to bypass dynamic routing holes arising in stationary wireless sensor networks in the presence of temporarily misbehaving nodes such as dumb [1, 2] or transfaulty nodes. The affected nodes behave normally after the resumption of favorable environmental conditions. Therefore, both dumb and transfaulty behaviors of sensor nodes are dynamic in nature. The nodes in these networks get temporarily isolated from the network, when they behave as dumb or transfaulty. Because of the presence of nodes with such behavior, dynamic communication holes may occur in the network, which are formed or removed and thus increase or decrease in size with time. Connectivity re-establishment procedures can mitigate holes by re-connecting isolated nodes with the network after activating the intermediate sleep nodes, adjusting the communication range of intermediate nodes, or by using an alternative communication mode. However, such procedures cannot always re-establish connectivity because of the lack of neighbor nodes in reduced or adjusted communication range. Therefore, routing schemes using greedy forwarding approaches need to bypass holes to avoid the data packets from getting stuck at the boundary nodes and efficiently delivering them to the sink. However, the existing hole avoidance schemes consider holes as static. The proposed scheme, BRIDGE, detects hole boundary and bypasses routing traffics in the dynamic hole scenario. In the proposed scheme, a boundary node selects the next hop based on the minimum distance from all the neighbor nodes to the destination node, although this minimum distance is more than the distance to the destination from the node itself. Simulation results show that the performance of the proposed scheme degrades with the increase in hole area. Copyright © 2015 John Wiley & Sons, Ltd.

Obstacle detection and avoidance with noisy measurements using danger zone concepts

Potential collision danger increases if a vehicle gradually moves closer to other vehicles or obstacles. If the collision time can be predicted before the vehicle is dangerously close to other vehicles or obstacles, the vehicle can devise an effective evasive maneuver or reroute its path, thus avoiding collision. This paper proposes an obstacle avoidance algorithm for unmanned vehicles in an unknown environment. The proposed avoidance algorithm uses the danger zone concept to determine whether the obstacle or surrounding vehicle will cause a possible collision. The danger zone is constructed around the vehicle by using semi-algebraic functions. The possible collision can be predicted by checking the sign of these semi-algebraic functions. The semi-algebraic functions for constructing the danger zone apply the relative velocities between the vehicle, and other vehicles or obstacles and can be used for both two- and three-dimensional cases. Several avoidance schemes are provided, with examples to demonstrate the concept of the proposed approach.

Adaptive GTS Allocation Scheme with Applications for Real-time Wireless Body Area Sensor Networks

The IEEE 802.15.4 standard not only provides a maximum of seven guaranteed time slots (GTSs) for allocation within a superframe to support time-critical traffic, but also achieves ultralow complexity, cost, and power in low-rate and short-distance wireless personal area networks (WPANs). Real-time wireless body area sensor networks (WBASNs), as a special purpose WPAN, can perfectly use the IEEE 802. 15. 4 standard for its wireless connection. In this paper, we propose an adaptive GTS allocation scheme for real-time WBASN data transmissions with different priorities in consideration of low latency, fairness, and bandwidth utilization. The proposed GTS allocation scheme combines a weight-based priority assignment algorithm with an innovative starvation avoidance scheme. Simulation results show that the proposed method significantly outperforms the existing GTS implementation for the traditional IEEE 802.15.4 in terms of average delay, contention free period bandwidth utilization, and fairness.

No Accounting for Tax Avoidance

AbstractIn the 2010–15 Parliaments, the UK House of Commons Committee of Public Accounts held hearings and investigated some of the operations of the tax avoidance industry. Its reports have been highly critical of the role of big accountancy firms in designing, marketing and implementing tax avoidance schemes which have enabled their clients to avoid taxes. The Committee's recommendations set a reform agenda but drew a lukewarm response from the government. An examination of the Committee's reports provides an indication of the trajectories of future debates and policies.

A New Obstacle Avoidance Algorithm for Quad rotors Group in the presence of Dynamic and Static Obstacles

Abstract. In this paper a new geometric-based collision avoidance scheme is presented for a group of quad rotor in environment with static and dynamic obstacles. The objective is to consider the full dynamics of the system to design obstacle avoidance controllers for the group of quad rotors. We introduce a method for both moving and non-moving obstacles. The proposed algorithm guide group toward the target in the path which is tangent to obstacle defined safe circle and optimize trajectory for minimized path to target. Due to simulation results, it is independent of the number of agents and applicable for static and dynamic obstacles. Simulation results are presented to validate the designed algorithm.

Structured Lattice Codes for Some Two-User Gaussian Networks With Cognition, Coordination, and Two Hops

We study a number of two-user interference networks with multiple-antenna transmitters/receivers (MIMO), transmitter side information in the form of linear combinations (over an appropriate finite-field) of the information messages, and two-hop relaying. We start with a cognitive interference channel (CIC) where one of the transmitters (noncognitive) has knowledge of a rank-1 linear combination of the two information messages, while the other transmitter (cognitive) has access to a rank-2 linear combination of the same messages. This is referred to as the network-coded CIC, since such linear combination may be the consequence of some random linear network coding scheme implemented in the backbone wired network. For such channel we develop an achievable region based on a few novel concepts: precoded compute-and-forward (PCoF) with channel integer alignment (CIA), combined with standard dirty-paper coding. We also develop a capacity region outer bound and find the symmetric generalized degrees of freedom (GDoF) region of the network-coded CIC. Through the GDoF characterization, we show that knowing mixed data (linear combinations of the information messages) provides a unbounded spectral efficiency gain over the classical CIC counterpart, if the ratio (in decibel) of signal-to-noise (SNR) to interference-to-noise is larger than certain threshold. Then, we consider a Gaussian relay network having the two-user MIMO IC as the main building block. We use PCoF with CIA to convert the MIMO IC into a deterministic finite-field IC. Then, we use a linear precoding scheme over the finite-field to eliminate interference in the finite-field domain. Using this unified approach, we derive the symmetric sum rate of the two-user MIMO IC with coordination, cognition, and two-hops. We also provide finite-SNR results (not just DoF) which show that the proposed coding schemes are competitive against state-of-the-art interference avoidance scheme based on orthogonal access, for standard randomly generated Rayleigh fading channels.

Balancing virtual channel utilization for deadlock-free routing in torus networks

Torus networks have been widely used by modern commercial supercomputers due to low node degree and linear scalability cost. Meanwhile, the ring in each dimension of a torus creates cyclic channel dependencies, which pose challenges to the design of deadlock-free routing and virtual channel allocation schemes. Existing virtual channel allocation schemes such as dateline employ two virtual channels to avoid deadlock in a ring. While the unbalanced utilization of virtual channels caused by these deadlock avoidance schemes brings lots of performance pathologies. This paper focuses on improving deadlock-free routing algorithms in torus by balancing virtual channel utilization. First, we propose BVCU, a novel virtual channel allocation scheme that can balance the utilization of the two virtual channels used to prevent deadlock. The technique is deadlock free and can achieve almost perfect balanced utilization. Second, we propose a balanced dimension-order routing (BDOR) to provide deadlock-free deterministic routing for $$n$$n-D torus by combining BVCU with dimension-order routing. Also, a balanced fully adaptive routing (BFAR) is proposed. These routing algorithms yield higher performance than existing solutions as they achieve a proper balanced utilization of virtual channels. Finally, simulation results show that the proposed methods achieve up to 16 % throughput improvement.

Tax Transparency – How To Make It Work?

The author reports on the 7th CFE Professional Affairs Conference held on 5 December 2014 in Paris, wherein three aspects of tax transparency were discussed: corporate country-by-country reporting (CBCR), mandatory disclosure of tax avoidance schemes and “cooperative compliance” in respect of the relationship between taxpayers and their advisers and the tax administration.

Coexistence of Wi-Fi and heterogeneous small cell networks sharing unlicensed spectrum

As two major players in terrestrial wireless communications, Wi-Fi systems and cellular networks have different origins and have largely evolved separately. Motivated by the exponentially increasing wireless data demand, cellular networks are evolving towards a heterogeneous and small cell network architecture, wherein small cells are expected to provide very high capacity. However, due to the limited licensed spectrum for cellular networks, any effort to achieve capacity growth through network densification will face the challenge of severe inter-cell interference. In view of this, recent standardization developments have started to consider the opportunities for cellular networks to use the unlicensed spectrum bands, including the 2.4 GHz and 5 GHz bands that are currently used by Wi-Fi, Zigbee and some other communication systems. In this article, we look into the coexistence of Wi-Fi and 4G cellular networks sharing the unlicensed spectrum. We introduce a network architecture where small cells use the same unlicensed spectrum that Wi-Fi systems operate in without affecting the performance of Wi-Fi systems. We present an almost blank subframe (ABS) scheme without priority to mitigate the co-channel interference from small cells to Wi-Fi systems, and propose an interference avoidance scheme based on small cells estimating the density of nearby Wi-Fi access points to facilitate their coexistence while sharing the same unlicensed spectrum. Simulation results show that the proposed network architecture and interference avoidance schemes can significantly increase the capacity of 4G heterogeneous cellular networks while maintaining the service quality of Wi-Fi systems.

LockSim: An Event-Driven Simulator for Modeling Spin Lock Contention

Spin lock contention in operating systems can limit scalability on multicore systems so significantly that an increase in the number of cores actually leads to reduced speedup (i.e., scalability collapse). Modeling spin lock contention is an effective way to understand the scalability collapse phenomenon and explore collapse avoidance schemes. However, previous spin lock models have disadvantages in accuracy and efficiency. To overcome these drawbacks, this paper proposes LockSim, an event-driven simulator which models both the sequential execution in lock-protected codes (i.e., critical sections) and shared hardware resource contention caused by the cache coherence protocol. Our simulator is verified against real-world workloads with different degrees of spin lock contention. Experimental results suggest that LockSim can reproduce the scalability collapse phenomenon with better accuracy than previous work. Besides, several metrics are also used to characterize this phenomenon and collapse avoidance methods are investigated.

A VLC Based Vehicle Collision Avoidance Scheme for Intelligent Transport Systems

Visible Light Communication (VLC) technology is one of the main candidate solutions for Intelligent Transportation Systems (ITS). This paper presents a comprehensive study on VLC based anti-rear-end collision scheme on the highway. A detailed VLC based rear-end collision avoidance model is proposed with theoretical analysis and numerical simulations.

The BEPS Project: Disclosure of Aggressive Tax Planning Schemes

Action 12 of the Base Erosion and Profit Shifting (BEPS) Action Plan promises the development of new rules on disclosure of aggressive tax planning arrangements. This article examines the meaning of the phrase, the experience of the UK with Disclosure of Tax Avoidance Schemes, and raises some issues about the Organization for Economic Cooperation and Development (OECD) plans in this area.

RSAODV : A Route Stability Based Ad Hoc on Demand Distance Vector Routing Protocol for Mobile Ad Hoc Network

High mobility of mobile nodes is one of the major reasons for link failures in mobile ad hoc network (MANET). The present paper aims at proposing modification of well known Ad hoc On demand Distance Vector (AODV) routing protocol for MANET seeking stable route for data transmission and incorporating link break avoidance scheme for such networks. The performance of the proposed routing protocol, named as Route Stability based Ad hoc On demand Distance Vector (RSAODV), is evaluated considering some major performance metrics which include average route life time, throughput, packet delivery fraction, normalized routing load and end–to-end delay. The study is based on simulation runs adopting CBR traffic pattern taking care of node failure scenarios. The performance of RAODV is compared with AODV routing protocol. The simulation runs exhibit significant increase in average route life time, packet delivery fraction and throughput for RSAODV, on the other hand, the normalized routing load and end–to-end delay are reduced for this routing protocol as compared to AODV routing protocol.