Multi‐Manipulator Collaboration Based on Topology Transformation

In recent years, the problem of reinforcement learning has become increasingly complex, and the computational demands with respect to such processes have increased. Accordingly, various methods for effective learning have been proposed. With the help of humans, the learning object can learn more accurately and quickly to maximize the reward. However, the rewards calculated by the system and via human intervention (that make up the learning environment) differ and must be used accordingly. In this paper, we propose a framework for learning the problems of competitive network topologies, wherein the environment dynamically changes agent, by computing the rewards via the system and via human evaluation. The proposed method is adaptively updated with the rewards calculated via human evaluation, making it more stable and reducing the penalty incurred while learning. It also ensures learning accuracy, including rewards generated from complex network topology consisting of multiple agents. The proposed framework contributes to fast training process using multi-agent cooperation. By implementing these methods as software programs, this study performs numerical analysis to demonstrate the effectiveness of the adaptive evaluation framework applied to the competitive network problem depicting the dynamic environmental topology changes proposed herein. As per the numerical experiments, the greater is the human intervention, the better is the learning performance with the proposed framework.

ABSTRACTVehicular ad hoc networks (VANETs) are very changeable networks due to the highly dynamic movement of their nodes, resulting in frequent link disconnection and variable node density. One of the most challenging issues in VANETs is to propose a suitable routing scheme that is adapted to the characteristics of such a dynamic topology. Position‐based routing schemes that are effective in handling dynamic changes in the topology of VANETs are proposed. This article proposes an efficient routing protocol based on a greedy forwarding approach called ERGF. The proposed protocol is a position‐based routing protocol that uses fresh vehicular traffic information in the routing process. ERGF consists of two main algorithms: the vehicle traffic freshness dissemination algorithm and the greedy forwarding algorithm. The both algorithms work together to provide fresh, up‐to‐date information about vehicle traffic, enabling the proposed routing protocol to effectively withstand dynamic changes in VANET network topology. The proposed protocol has been developed over OMNET++ simulator, evaluated and compared with some other protocols. The simulation results showed that the proposed protocol provided better performance in terms of packet delivery rate and end‐to‐end delay than the EGyTAR and PBRP protocols. The packet delivery ratio of our proposal is approximately 75% and 6% higher than EGyTAR and PBRP, respectively, and the end‐to‐end delay of our protocol is reduced by 37% and 7%, respectively, compared with EGyTAR and PBRP for most scenarios.

While network path generation has been one of the representative Non-deterministic Polynomial-time (NP)-hard problems, changes of network topology invalidate the effectiveness of the existing metaheuristic algorithms. This research proposes a new and efficient path generation framework that considers dynamic topology changes in a complex network. In order to overcome this issue, Multi-directional and Parallel Ant Colony Optimization (MPACO) is proposed. Ant agents are divided into several groups and start at different positions in parallel. Then, Gaussian Process Regression (GPR)-based pheromone update method makes the algorithm more efficient. While the proposed MPACO algorithm is more efficient than the existing ACO algorithm, it is limited in a network with topological changes. In order to overcome the issue, the MPACO algorithm is modified to the Convolution MPACO (CMPACO) algorithm. The proposed algorithm uses the pheromone convolution method using a discrete Gaussian distribution. The proposed pheromone updating method enables the generation of a more efficient network path with comparatively less influence from topological network changes. In order to show the effectiveness of CMPACO, numerical networks considering static and dynamic conditions are tested and compared. The proposed CMPACO algorithm is considered a new and efficient parallel metaheuristic method to consider a complex network with topological changes.

A hybrid caching strategy for information-centric satellite networks based on node classification and popular content awareness

Exploring and controlling topological textures such as merons and skyrmions has attracted enormous interests from the perspective of fundamental research and spintronic applications. It has been predicted theoretically and proved experimentally that the lattice form of topological meron-skyrmion transformation can be realized with the requirement of external magnetic fields in chiral ferromagnets. However, such topological transition behavior has yet to be verified in other materials. Here, we report real-space observation of magnetic topology transformation between meron pairs and skyrmions in the localized domain wall of ferrimagnetic GdFeCo films without the need of magnetic fields. The topological transformation in the domain wall of ferrimagnet is introduced by temperature-induced spin reorientation transition (SRT) and the underlying mechanism is revealed by micromagnetic simulations. The convenient electric-controlling topology transformation and driving motion along the confined domain wall is further anticipated, which will enable advanced application in magnetic devices.

Due to station mobility, the network topology is continuously changing in mobile ad hoc networks. In this paper, we propose a neighbor-table-based multipath routing (NTBMR) protocol to track the dynamic topology changes. Distinguished from prior work on multipath protocols employing disjoint paths, NTBMR does not require the routes to be disjoint. In order to verify the different capabilities against dynamic topology changes for disjoint and non-disjoint multipath routings, we make an attempt to analyze their route reliabilities. Theoretical analysis reveals that non-disjoint multipath routing has higher route reliability when the wireless links are unreliable. In NTBMR scheme, we also present a technique to estimate the mean and variance of the lifetime of a wireless link, which can be used to aid route discovery and maintenance. Simulation results show that our multipath routing scheme is relatively robust in an environment with frequent topology changes and can improve the end-to-end delay and packet delivery ratio performance substantially compared to unipath routing.

Owing to the increasing capabilities of mobile devices and the development of mobile communication techniques in vehicular ad hoc networks (VANETs), mobile multimedia services have focused on supporting high Quality of Service (QoS) and Quality of Experience (QoE) for the subscribers in video streaming services. In VANETs, high-quality video streaming services aim to provide safety, as well as various infotainment applications to the subscribers. Owing to the dynamic topology and frequent connectivity changes in moving vehicles, video streaming services require elastic and continuous updates of vehicle information to present interactive real-time views of nontrivial scenarios on roads. To achieve high QoS and QoE of video streaming services in VANETs, this paper proposes a novel protocol named PSOstreaming that is based on a particle swarm optimization (PSO) which is one one of the mainstream and nature-inspired algorithms for swarm intelligence (SI). PSOstreaming calculates the PSQ score, which is the scoring method of the node in the topology in terms of the data communication capability measurement to analyze and optimize topology information in real-road circumstances. In addition, PSOstreaming utilizes a 3D vector mobility prediction algorithm for the mobility prediction method for the vehicles to address the characteristics of VANETs. In the topology, PSOstreaming defines Global PSO members and Local PSO members to disseminate video packets for video-streaming services to the service requester by computational equations. Experimental results indicate that PSOstreaming achieves high-quality video streaming services with a flexible response to dynamic topology changes and a high frame delivery ratio in terms of QoS and QoE.

Mobile ad hoc network (MANET) is a network that has fast characteristics, efficient deployment, and can apply in an emergency location such as natural disasters, military operations, forest fires, and health monitoring. However, the challenges and problems facing MANET are dynamic topology changes, with no fixed infrastructure, and limited energy sources. Dynamic topology changes will result in redundant data packets on each node, and the quality of the network will decrease. To overcome problems in MANET then selection of routing protocol is essential in improving network quality. This study aims to compare the performance of AODV, AOMDV, and DSDV routing protocols based quality of service (QoS). Parameters QoS to be analyzed are packet delivery ratio (PDR), packet loss, throughput, delay, and routing overhead (RO). The simulation result using NS-2 shows that AOMDV performs better than AODV and DSDV regarding PDR. AODV performs better than AOMD and DSDV regarding throughput, RO. While DSDV performs has better than AODV and AOMDV regarding the delay.

Dynamic network is the abstraction of networks with frequent topology changes arising from node mobility or other reasons. With the model of dynamic network, fundamental distributed computing problems can be formally studied with rigorous correctness. In this work, we study the counting problem, which plays a significant role in many applications, such as all-to-all information dissemination. Existing counting algorithms for dynamic networks are mostly estimation based and randomized, and cannot achieve accurate results deterministically. To address this problem, we adopt the diffusing computation approach in this paper. Although this approach has been widely used to solve different distributed computing problems, due to dynamic topology changes, existing diffusing computation algorithms cannot work under dynamic network models. To address such challenge, we firstly define a new dynamicity model, named (Q, S)-distance, which is used to describe dynamic changes of information propagation time. Based on (Q, S)-distance, we design two different counting algorithms. The first algorithm focuses on extending typical diffusing computation approach by handling topology changes. Different from existing algorithms, which have two phases, our algorithms contain three phases and the new phase is used to determine and notify the termination of tree growing, which the major challenge is caused by topology dynamicity. The second algorithm further extends the first one by incorporating a cluster-based hierarchy to reduce communication cost. The correctness of both the algorithms is formally proved and their performances in time cost and communication cost are analyzed.

Ad-hoc networks do not provide an infrastructure for communication such as routers and are characterized by 1) quick changes of communication topology and 2) unstable system behaviors. Self-stabilizing algorithms have been studied well to design stable distributed algorithms on unstable systems, but they are not requested to be adaptive to dynamic topology changes. We in this paper propose a new concept of dynamic reconfiguration tolerant (DRT for short) self-stabilizing algorithm, which is a self-stabilizing algorithm that is also robust against dynamic changes of topology. We next propose a DRT self-stabilizing token circulation algorithm. It deterministically circulates a token through a spanning tree edges in an asymptotically optimal time O(n), once the system is stabilized. The spanning tree will converge to the minimum spanning tree, if the network remains static.

Due to the broad prospect of Vehicular Ad hoc Networks (VANETS) on road safety, traffic management and entertainment applications, data transmission technology of VANETS has been became the focus of the study. However, dynamic topology changes and vehicle move speed of VANETS results in link break of workshop communication, which reduces the reliability of the link. This paper presents the cooperative communication mechanism to improve the reliability of the communication link and ease the wireless road deterioration caused by vehicle movement. Based on the ADHOC MAC scheme, cooperative ADHOC MAC scheme is proposed referred as COOMACP. In COOMACP, once the data packet unsuccessfully transmitted to the destination node, the neighbor nodes will use the unoccupied slot to offer cooperative pattern and retransmit data. Through the theoretical analysis, the probability of cooperative mode is proposed. Theoretical analysis and simulation results show that COOMACP improves the probability of successful transmission of data packets and improves the system throughput.

Robust and continuous connectivity maintenance for vehicular dynamic spectrum access networks

A variety of modeling frameworks have been proposed and utilized in complex systems studies, including dynamical systems models that describe state transitions on a system of fixed topology, and self-organizing network models that describe topological transformations of a network with little attention paid to dynamical state changes. Earlier network models typically assumed that topological transformations are caused by exogenous factors, such as preferential attachment of new nodes and stochastic or targeted removal of existing nodes. However, many real-world complex systems exhibit both state transition and topology transformation simultaneously, and they evolve largely autonomously based on the system’s own states and topologies. Here we show that, by using the concept of graph rewriting, both state transitions and autonomous topology transformations of complex systems can be seamlessly integrated and represented in a unified computational framework. We call this novel modeling framework “Generative Network Automata (GNA)”. In this chapter, we introduce basic concepts of GNA, its working definition, its generality to represent other dynamical systems models, and some of our latest results of extensive computational experiments that exhaustively swept over possible rewriting rules of simple binary-state GNA. The results revealed several distinct types of the GNA dynamics.KeywordsCellular AutomatonCentral NodePreferential AttachmentPolynomial GrowthDynamical System ModelThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Recently, the emerging computation-intensive in-vehicle applications and the exponentially growing data have posed a serious challenge to resource-limited in-vehicle devices. By integrating the mobile edge computing (MEC) into the vehicle networks, vehicular edge computing (VEC) is envisioned as a promising solution. In this paper, we divide the VEC system into small time slots, which effectively simulates dense small-scale computing scenarios in the rapidly varying channel environment over time. Furthermore, to alleviate the shortage of spectrum resources, vehicles can offload part of computing tasks to the edge server not only through licensed channels but also through unlicensed channels. However, dynamic topology changes and complex communication characteristics of the vehicle networks lead to the strategies of task offloading and resource allocation being difficult to obtain. By decoupling the non-convex optimizing problem and splitting it into multiple sub-problems, we design a joint power, spectrum and computing resource allocation strategy with low complexity, in order to minimize the total energy consumption of all vehicles for processing tasks. Theoretical analysis and simulation results validate the effectiveness of the proposed scheme that employing licensed and unlicensed access in VEC networks can reduce the energy consumption of vehicles for processing tasks in comparison with baseline schemes.

Mobile Adhoc Networks (MANETs) are the self-organized networks in which connections are not established for exchange the information. In MANET, there are major problems like scalability, dynamic topology, high mobility and routing. The network can be damaged due to the high mobility. Topology based routing can fail when there is a dynamic change in the network topology. To avoid these problems, Geographic routing is used. The geographic routing protocols are more efficient and scalable when there is a dynamic change in the network topology and when the mobility is high. In this paper, we have surveyed on the Hybrid Routing and Geographic routing protocol. The hybrid routing can be done into two ways i.e. greedy routing and face-2 algorithm or perimeter routing.