Topology Control Scheme Research Articles

Topology Control in Hybrid VLC/RF Vehicular Ad-Hoc Network

Vehicular ad-hoc network (VANET) is a promising technology to realize communications among vehicles in intelligent transportation systems. Conventional VANET utilizes radio frequency (RF) for vehicle to vehicle communications. However, as the vehicle density increases, RF-based VANET suffers from limited bandwidth and unavoidable interference. Visible light communication (VLC) is emerging as a complement candidate, which possesses the advantages of wide spectrum, high power efficiency and low interference, but also has the drawback of limited communication range. Therefore, the hybrid VLC/RF structure is beneficial to an efficient and reliable VANET. Since there are usually no center infrastructures in VANET and different vehicles could have different preferences, the distributed and non-cooperative topology control (TC) should be investigated for the establishment of VLC and RF links among various vehicles to satisfy some properties, e.g., interference level, power consumption, connectivity and delay requirements. Conventional TC schemes designed particularly for RF-based ad-hoc network can not be applied directly due to the distinctive features of VLC and RF links. In this paper, the TC problem for the hybrid VLC/RF VANET is modeled as a potential game. When considering the different features of the two kinds of links, a distributed TC algorithm is proposed to handle the TC game, in which the RF and VLC transmitting power of each vehicle is locally adapted based on the vehicle’s local knowledge about the VANET topology and can converge to a Nash Equilibrium state.

Data Driven Coordinated Control of Converters in a Smart Solid State Transformer for Reliable and Automated Distribution Grids

A data-driven smart solid-state transformer (SST) is an attractive building block for reliable and automated distribution power grids. An SST can work as an energy buffer unit in a completely embedded framework, similar to the information internet router, which facilitates a seamless information flow between the local grids and the data centers. An SST connects two or more electric subsystems and then distributes the energy to other subsystems based on a data-driven energy dispatch and intelligent management algorithm. The modern SST-based distribution grid has been envisioned to integrate several renewable energy sources, energy storage devices, and dc or ac loads in a standardized protocol-based plug-n-play technique, which may form a dc or an ac zonal microgrid system. Energy-efficient monitoring, coordination, control management, and economic dispatch are crucial issues for the optimal operation of an SST. This article proposes a data-driven coordinated control strategy for a three-stage multiple active bridge converter-based SST topology, which can ensure improved power quality of the distribution grid. A step-by-step controller design methodology is developed, which can coordinate several control data according to the various SST functionalities. The article presents the simulation and experimental results that validate the effectiveness of the proposed coordinated control approach.

Optimization Research on a Switching Power Amplifier and a Current Control Strategy of Active Magnetic Bearing

Active magnetic suspension bearing technology has been widely used in the field of high-speed motors because of its many technical advantages. A switching power amplifier is an important part of active magnetic bearing. This paper first analyzes the topology of a switching power amplifier and proposes an optimized switching power amplifier topology, which can significantly reduce the number of switches used in a power amplifier. Then, by studying the transfer function of the system, the boundary conditions of the power amplifier bandwidth, stiffness and damping, which maintain system stability, are obtained. Furthermore, an improved current control strategy is proposed, and this strategy can significantly improve the bandwidth of the switching power amplifier and improve the stability and dynamic performance of the system. Simulations and experiments verify the practicability and effectiveness of the topology and current control strategy proposed in this paper.

Energy-Efficient Topology Control for UAV Networks

Following striking developments in Unmanned Aerial Vehicle (UAV) technology, the use of UAVs has been researched in various industrial fields. Furthermore, a number of studies on operating multiple autonomous networking UAVs suggest a potential to use UAVs in large-scale environments. To achieve efficiency of performance in multi-UAV operations, it is essential to consider a variety of factors in UAV network conditions, such as energy efficiency, network overhead, and so on. In this paper, we propose a novel scheme that improves the energy efficiency and network throughputs by controlling the topology of the network. Our proposed network topology control scheme functions between the data link layer (L3) and the network layer (L2). Accordingly, it can be considered to be layer 2.5 in the network hierarchy model. In addition, our methodology includes swarm intelligence, meaning that whole topology control can be generated with less cost and effort, and without a centralized controller. Our experimental results confirm the notable performance of our proposed method compared to previous approaches.

Improving Energy Efficiency in Wireless Sensor Networks through Virtual-Backbone–Based Topology Control Mechanism

Abstract This article presents a design of a virtual-backbone–based topology control scheme that builds the virtual backbone with the help of localized information. Initially, the dominating set is constructed using spanning tree application. The resultant dominating set spanning tree is further optimized to remove dominant act nodes because, originally, they are the regular nodes, and it forms a small-sized backbone with selected sufficient energy capacity nodes. Then the 3-hop message forward algorithm is used to identify the relay nodes. The roles of the relay nodes are to make the dominating set as a connected dominating set (CDS). Finally, a minimal CDS is formed by a heuristic approach to remove redundant sensors from the CDS.

Binary grey wolf optimisation‐based topology control for WSNs

Wireless sensor networks (WSNs) are composed of a large number of sensor nodes that are deployed at target locations. Topology control (TC) is one of the significant fundamental challenges in WSNs because of node energy and computing power constraints. TC algorithms try to produce reduced topology by preserving network connectivity. This study presents a novel TC algorithm based on binary Grey wolf optimisation. It uses the active and inactive schedules of sensor nodes in binary format as well as introduces fitness function to minimise the number of active nodes (ANs) for achieving the target of lifetime expansion of the nodes and network. The proposed algorithm is compared with other TC algorithms. The result reduces a minimum of 10% of ANs and energy consumption by 6.84%. The proposed approach also gives maximum coverage and connectivity. The designed fitness function also benefits in the process of selecting a node with low residual energy to join the active topology. The standard deviation in the remaining energy for the proposed algorithms is lower than the other TC schemes.

Adaptive Topology Control for Hierarchical Routing Over Resource Constrained Wireless Sensor Networks

Topology defines the standards used by sensors to communicate with each other. Frequent updates in topology may cause excessive control overhead. Overall resource requirements for network operations can be reduced by optimizing the topology control schemes. In this paper, traditional methods for topology management are investigated and a new approach is introduced to manage the frequent topological updates.

Security-aware Localized Topology Control Algorithm for Mobile Ad-hoc Networks

In this paper, we extend the topology control schemes by making security the primary concern. For this purpose, we propose a security-aware localized topology control algorithm that can maximally avoid making malicious nodes into intermediate nodes. In order to marginalize malicious nodes, we introduce a new metric for characterizing the security status of each link in the network. Each node independently builds a local spanning tree for finding a reduced neighbor set. In the meantime, we maximally avoid using insecurity links in their neighborhood for the local spanning tree construction. Simulation results show that our algorithm significantly improves the security of a network.

Power Flow in a Multi-Frequency HVac and HVdc System: Formulation, Solution, and Validation

This paper proposes a novel power flow formulation and solution algorithm for a generalized large-scale interconnected transmission system encompassing multi-frequency HVac and HVdc grids having arbitrary numbers of buses, topologies, and operating frequencies. Back-to-back and ac/dc voltage-source converters are employed to interconnect and control the voltage and power interchange between two power grids operating at different frequencies. The power Flow formulation is based on a steady-state model of back-to-back and ac/dc converters operated in centralized and distributed droop control strategies. Each power grid is represented by a set of nonlinear power balance equations. These equations are solved simultaneously using a unified power flow algorithm, taking into account generator and converter limits. It is shown that the solution convergence is achieved rapidly despite the system size, topology, and converter control strategies. The efficacy and accuracy of the proposed steady-state solution algorithm are demonstrated by comparing the numerical solution to the one obtained by time-domain electromagnetic models of multi-frequency HVac and HVdc transmission systems with fully controllable back-to-back and ac/dc converters. The results obtained by using the proposed algorithm and the time-domain simulation are practically identical.

Dynamic Network Topology Control of Branch-Trimming Robot for Transmission Lines

With the development of engineering technology, the distributed design-based Branch-Trimming Robot (BTR) has been used to ensure the power supply security of transmission lines. However, it remains difficult to combine distributed BTRs with a wireless sensor network to build an efficient multi-robot system. To achieve this combination, a dynamic network topology control method was proposed, combining the motion characteristics of robots with the structure of a distributed wireless sensor network. In addition, a topology-updating mechanism based on node signal strength was adopted as well. To achieve efficient data transmission for distributed multi-robot systems, the present study focused on the design of a distributed network model and a dynamic network topology control strategy. Several simulation and test scenarios were implemented, and the changes of network performance under different parameters were studied. Furthermore, the real scene-based dynamic topology control method considers the relationship between network performance and antenna layout.

Architecture and Network Model of Time-Space Uninterrupted Space Information Network

Space information network (SIN) plays an extremely important role in civil and military applications. However, a specific definition of SIN still remains a challenging issue. Unlike space communication network (SCN), which merely focuses on information delivery, SIN has the ability to process the delivered information and providing corresponding services based on the information, which makes SIN seem to be able to understand information. This paper offers architecture and corresponding network model for time-space uninterrupted SIN. Initially, both physical and logical constitution of SIN architecture are presented with several corresponding constellation designs, which is the fundamental work for setting nodes in SIN. Based on this SIN architecture, a hierarchical autonomous system (AS)-based network model for SIN is proposed in order to manage SIN more efficiently by separating the whole network into several relatively stable ASs. Furthermore, we analyze topology control schemes and network capacity trend of AS-model based SIN. This paper gives the future research directions in the conclusion.

Novel hybrid excited machine with flux barriers in rotor structure

PurposePermanent magnet (PM) electrical machines are becoming one of the most popular type of the machines used in electrical vehicle drive applications. The main drawback of permanent magnet machines, despite obvious advantages, is associated with the flux control capability, which is limited at high rotor speeds of the machine. This paper aims to present a new arrangement of permanent magnets and flux barriers in the rotor structure to improve the field weakening control of hybrid excited machines. The field weakening characteristics, back-emf waveforms and efficiency maps of this novel machine have been reported.Design/methodology/approachIn the study, finite element analysis was used to perform simulation research. Then, based on the simulation studies, an experimental model was built. The paper also presents selected experimental results.FindingsObtained results show that the proposed machine topology and novel control strategy can offer an effective flux control method allowing to extend the maximal rotational speed of the machine at constant power range.Practical implicationsThe proposed solution can be used in electric vehicles drive to extend its torque and speed range.Originality/valueThe paper presents original design and results of research on a new solution of a hybrid excited machine with magnetic barriers in a rotor.

Topology Control Strategy for Movable Sensor Networks in Ultradeep Shafts

Ultradeep shafts are the only means available to extract solid mineral resources from deep within the earth, and the conditions of these shafts directly affect the working safety of the lifting system. Chain-type wireless sensor networks (CWSNs), which are mobile and self-supporting, provide a new option for mobile collaborative monitoring of ultradeep shafts by sampling panoramic images. In this paper, a topological control method for CWSNs in an ultradeep shaft based on mobile sensor nodes is proposed. First, a video sensor node that can vertically climb a rope and automatically generate power is designed. Then, a uniform chain-type deployment strategy is proposed to accommodate the actual conditions of an ultradeep shaft. Ultimately, the network repair strategies based on mobile nodes are designed to address node movement and communication failures. The research results indicate that a uniform hierarchical deployment algorithm with a scheduling strategy can achieve overall monitoring of the ultradeep shaft in a monitoring cycle and that the collaborative repair strategy can effectively maintain the linear-domain coverage of the network.

Adaptive Transmission Range Based Topology Control Scheme for Fast and Reliable Data Collection

An Adaptive Transmission Range Based Topology Control (ATRTC) scheme is proposed to reduce delay and improve reliability for data collection in delay and loss sensitive wireless sensor network. The core idea of the ATRTC scheme is to extend the transmission range to speed up data collection and improve the reliability of data collection. The main innovations of our work are as follows: (1) an adaptive transmission range adjustment method is proposed to improve data collection reliability and reduce data collection delay. The expansion of the transmission range will allow the data packet to be received by more receivers, thus improving the reliability of data transmission. On the other hand, by extending the transmission range, data packets can be transmitted to the sink with fewer hops. Thereby the delay of data collection is reduced and the reliability of data transmission is improved. Extending the transmission range will consume more energy. Fortunately, we found the imbalanced energy consumption of the network. There is a large amount of energy remains when the network died. ATRTC scheme proposed in this paper can make full use of the residual energy to extend the transmission range of nodes. Because of the expansion of transmission range, nodes in the network form multiple paths for data collection to the sink node. Therefore, the volume of data received and sent by the near‐sink nodes is reduced, the energy consumption of the near‐sink nodes is reduced, and the network lifetime is increased as well. (2) According to the analysis in this paper, compared with the CTPR scheme, the ATRTC scheme reduces the maximum energy consumption by 9%, increases the network lifetime by 10%, increases the data collection reliability by 7.3%, and reduces the network data collection time by 23%.

A Review on Machine Topologies and Control Techniques for Low-Noise Switched Reluctance Motors in Electric Vehicle Applications

This paper presents a technical overview for low-noise switched reluctance motor (SRM) drives in electric vehicle (EV) applications. With ever-increasing concerns over environmental and cost issues associated with permanent magnet machines, there is a technical trend to utilize SRMs in some mass production markets. The SRM is gaining much interest for EVs due to its rare-earth-free characteristic and excellent performance. In spite of many advantages compared with conventional adjustable-speed drives, SRMs suffer from torque ripple and radial distortion (and thus noise and vibration) by their nature. Therefore, for high-performance vehicle applications, it is important and urgent to optimize the SRM system to overcome the drawbacks of the noise and vibration. In order to present clear solutions to the acoustic noise in SRMs, this paper starts by analyzing the mechanism of the radial vibration and torque ripples inherent in the motors, and then focuses on the state-of-the-art technologies to mitigate the radial force and torque ripples. It highlights two categories for low-noise SRMs, including the machine topology improvement and control strategy design for radial vibration mitigation and torque ripple reduction. Advanced technologies are reviewed, classified, and compared accordingly. In addition to these methodologies, the schemes that have been developed by authors are also presented and discussed. Finally, the research status on this topic is summarized and forecast research hotspots are presented. It is our intention that this paper provides the guidance on performance improvements for low-noise SRM drives in EV applications.

Cooper: Expedite Batch Data Dissemination in Computer Clusters with Coded Gossips

Data transfers happen frequently in server clusters for software and application deployment, and in parallel computing clusters to transmit intermediate results in batches among servers between computation stages. This paper presents Cooper , an optimized prototype system to speedup multi-batch data transfers among a cluster of servers, leveraging a theoretically proven optimal algorithm called “coded permutation gossip,” which employs a simple random topology control scheme to best utilize bandwidth and decentralized random linear network coding to maximize the useful information transmitted. On a process-level coding-transfer pipeline, we investigate the best block division, batch division and inter-batch scheduling strategies to minimize the broadcast finish time in a realistic setting. For batch-based transfers, we propose a scheduling algorithm with low overhead that overlaps the transfers of consecutive batches and temporarily prioritizes later batches, to further reduce the broadcast finish time. We describe an asynchronous and distributed implementation of Cooper and have deployed it on Amazon EC2 for evaluation. Based on results from real experiments, we show that Cooper can almost double the speed of data transfers in computing clusters, as compared to state-of-the-art content distribution tools like BitTorrent, at a low CPU overhead.

A Power Controlled Energy-efficient Clustering Scheme for Heterogeneous Wireless Sensor Networks

Topology control is one of the most important technologies in wireless sensor networks. Many applications, combined with the methods of power control and hierarchical topology control strategy, can ultimately achieve the purpose of energy saving and topology optimization. Taken into consideration both power control and average energy of adjacent region, the paper proposes an energy efficient clustering algorithm for heterogeneous WSNs, called Power Controlled Clustering algorithm with Average Energy of Adjacent Region (PCCAEAR). In PCCAEAR, the cluster heads election process is divided into two stages. Firstly, the candidate cluster heads are elected by a probability based on the ratio between residual energy of each node and average energy of adjacent region. Secondly, a regional cluster head can be identified as the node with the highest residual energy within a certain range, while a candidate cluster head is communicating with other reachable candidate cluster heads in a certain transmission power. The cluster heads are elected in a stable number per round and evenly distributed in network, which make the network energy consumption more balanced. Simulation results show that PCCAEAR algorithm has a longer network lifetime, with the first node dead round number increasing by 6%, 14% and 22% respectively compared to DEEC, TCAC and REAC algorithms.

A Topology Control Strategy with Reliability Assurance for Satellite Cluster Networks in Earth Observation.

This article investigates the dynamic topology control problem of satellite cluster networks (SCNs) in Earth observation (EO) missions by applying a novel metric of stability for inter-satellite links (ISLs). The properties of the periodicity and predictability of satellites’ relative position are involved in the link cost metric which is to give a selection criterion for choosing the most reliable data routing paths. Also, a cooperative work model with reliability is proposed for the situation of emergency EO missions. Based on the link cost metric and the proposed reliability model, a reliability assurance topology control algorithm and its corresponding dynamic topology control (RAT) strategy are established to maximize the stability of data transmission in the SCNs. The SCNs scenario is tested through some numeric simulations of the topology stability of average topology lifetime and average packet loss rate. Simulation results show that the proposed reliable strategy applied in SCNs significantly improves the data transmission performance and prolongs the average topology lifetime.

Topology control in the presence of jammers for wireless sensor networks

SummaryIn this paper, the problem of ensuring packet delivery ratio and high network lifetime in wireless sensor networks in the presence of single or multiple jammers is studied using single‐leader‐multiple‐followers Stackelberg game theory. A topology control scheme is proposed, in which the sink node, which acts as the leader, identifies the set of jamming affected nodes. On the other hand, the sensor nodes, which act as followers, need to decide an optimum transmission power level, while ensuring an optimal set of neighbor nodes covered. A scheme, named TC‐JAM, for ensuring packet delivery ratio, while avoiding jammers and increasing network lifetime in wireless sensor networks, is proposed. In existing literatures, the sensor nodes are envisioned to be equipped with multiple interfaces, while having access for multiple channels. However, in TC‐JAM, the sensor nodes have simple hardware with single interface for communication, ie, the sensor nodes have single channel for communication. Additionally, in the proposed scheme, TC‐JAM, each sensor node has a provision to vary its transmission power according to the chosen strategies. Using TC‐JAM, the energy consumption of the overall network reduces by up to 62%, and the network lifetime increases by 56% to 73%.

A Game-Based Localized Multi-Objective Topology Control Scheme in Heterogeneous Wireless Networks

In wireless networks, network topology may change at any time. Therefore, topology control is one of the effective methods to get and keep the desired topology performance. The most existing topology control methods assume that nodes are altruistic. Although there are some game-based topology control schemes to stimulate cooperation between nodes, they only consider a single objective (e.g., energy consumption or network lifetime), which cannot be adaptive to the variation of demand on topology performance. To address these weaknesses, we present the notion of link lifetime and model the multi-objective weight sum of any link as the function with respect to transmission power, link delay and link lifetime. Then the proposed game-based localized multi-objective topology control ensures that the desired topology property exists in resulting topology, in which the presented Improved LOCAL $\delta $ -Improvement Algorithm (LDIA) algorithm not only stimulates nodes’ cooperation on topology control operation and ensures network’s convergence to a steady state, but also has the better performance with respect to executing time and communication overhead than a classic algorithm, i.e., LDIA. Finally, the simulation results show that, by employing appropriate weight values, when compared with some typical schemes considering only energy efficiency, the proposed scheme is the most efficient in regard to average link delay and link lifetime. When compared with a typical scheme considering only network lifetime, the proposed scheme has advantage over average link lifetime, but it is slightly worse in terms of average link delay. Although the proposed scheme is less efficient in terms of average transmission power, where the shortage may be alleviated by adjusting weight values, it satisfies diversified demands for applications due to its flexibility.