Ad-hoc Mode Research Articles

Can We Observe Nonperturbative Vacuum Shifts in Cavity QED?

We address the fundamental question of whether or not it is possible to achieve conditions under which the coupling of a single dipole to a strongly confined electromagnetic vacuum can result in nonperturbative corrections to the dipole's ground state. To do so we consider two simplified, but otherwise rather generic cavity QED setups, which allow us to derive analytic expressions for the total ground-state energy and to distinguish explicitly between purely electrostatic and genuine vacuum-induced contributions. Importantly, this derivation takes the full electromagnetic spectrum into account while avoiding any ambiguities arising from an adhoc mode truncation. Our findings show that while the effect of confinement perse is not enough to result in substantial vacuum-induced corrections, the presence of high-impedance modes, such as plasmons or engineered LC resonances, can drastically increase these effects. Therefore, we conclude that with appropriately designed experiments it is at least in principle possible to access a regime where light-matter interactions become nonperturbative.

Systematically Improving the Efficiency of Grid-Based Coverage Path Planning Methodologies in Real-World UAVs’ Operations

This work focuses on the efficiency improvement of grid-based Coverage Path Planning (CPP) methodologies in real-world applications with UAVs. While several sophisticated approaches are met in literature, grid-based methods are not commonly used in real-life operations. This happens mostly due to the error that is introduced during the region’s representation on the grid, a step mandatory for such methods, that can have a great negative impact on their overall coverage efficiency. A previous work on UAVs’ coverage operations for remote sensing, has introduced a novel optimization procedure for finding the optimal relative placement between the region of interest and the grid, improving the coverage and resource utilization efficiency of the generated trajectories, but still, incorporating flaws that can affect certain aspects of the method’s effectiveness. This work goes one step forward and introduces a CPP method, that provides three different ad-hoc coverage modes: the Geo-fenced Coverage Mode, the Better Coverage Mode and the Complete Coverage Mode, each incorporating features suitable for specific types of vehicles and real-world applications. For the design of the coverage trajectories, user-defined percentages of overlap (sidelap and frontlap) are taken into consideration, so that the collected data will be appropriate for applications like orthomosaicing and 3D mapping. The newly introduced modes are evaluated through simulations, using 20 publicly available benchmark regions as testbed, demonstrating their stenghts and weaknesses in terms of coverage and efficiency. The proposed method with its ad-hoc modes can handle even the most complex-shaped, concave regions with obstacles, ensuring complete coverage, no-sharp-turns, non-overlapping trajectories and strict geo-fencing. The achieved results demonstrate that the common issues encountered in grid-based methods can be overcome by considering the appropriate parameters, so that such methods can provide robust solutions in the CPP domain.

Empirical Study on Wireless Multimedia & Mesh Ad-Hoc Network

In this paper, we present about the construction of a wireless multimedia & mesh ad-hoc network needs to go across the mixed environment with the indoor, the wall-penetration, and the outdoor condition. This paper presents contribution to address the system design aspects of a multimedia enabled network based on IEEE 802.11g ad-hoc mode. There are distinct differences between indoor and outdoor environment and penetrating he walls stressed the system limit of the 802.11g ad-hoc mode. Therefore, routing decisions should be made intelligently with the environmental respect to maximize the bandwidth support on the end-to-end paths. One of the biggest issues in routing is providing adequate connectivity whiles calling the network. IEEE 802.16 employs TDMA (Time Division Multiple Access) as the access method and the policy for selecting scheduled links in a given time slot will definitely impact the system performance. We propose a collision-free centralized scheduling algorithm for IEEE 802.16 based Wireless Mesh Networks (WMN) to provide high-quality wireless multimedia services. We design a relay strategy for the mesh nodes in a transmission tree, taking special considerations on fairness, channel utilization and transmission delay

Methodology of Effective Application of Economic-Mathematical Modeling as the Key Component of the Multi-Crisis Adaptive Management

Abstract. Introduction. The modern economy is characterized not only by processes of increasing globalization and competition in markets, mobility and internationalization of resources, rapid development of innovative information technologies, but also by rapid spread of crisis phenomena in the middle and between national economies - all these factors put forward new requirements for effective corporate management [1, 2]. Purpose. Thus, for the sake of stability, not only in the current global market competition, but especially in the context of multi-level crisis phenomena [3], all efficient companies (including logistic) should be able to adapt quickly and efficiently to changes, i.e., they must be systemically adaptive with using economic and mathematical modeling of crisis program, forecasting the results of crisis management. Results. The two main groups of results will provide an adequate, systemic multi-modal response to a variety of crisis events and situations. The process of assembling and configuring the elements of the crisis program (plan) is inherently an open, heuristic, intellectual process of making managerial decisions and scenarios. The intellectual and professional abilities of the manager (specialist, auditor, controller) performing this task play a significant role in the development and implementation of effective crisis management plans and programs. This determines the importance of the personal factor and experience in preparing for decision-making in open problems, determines the requirements for the selection and organization of work in the ad-hoc mode of internal and external experts ( auditors, controllers). However, a study of the management practice of logistics companies in emerging markets (especially in the context of the current global pandemic) showed a significant and negative potential impact of subjective factors on decisions of the management of logistics companies, their auditors and controllers (cheating, corruption, raiding, inattention, industrial espionage, etc.). To limit the influence of the above subjective factors, the authors conducted research in the field of economic and mathematical modeling on two main tasks: development of a methodology and model for the formation of a crisis plan for a logistics company in the context of a possible multi-level crisis and development of methodology and improvement of models for predicting the results of a possible implementation of an crisis three-level adaptive program for a logistics company, taking into account the influence of the current multi-level crisis features and conditions. The results obtained can be used by logistics companies on emerging markets of developing countries and under the influence of similar political, macroeconomic and pandemic crisis phenomena (for example, including many countries in Africa, most countries in Eastern Europe, some countries of Latin America, some countries in the Middle East, and some countries in Southeast Asia). Conclusions. The obtained results are relevant and applicable not only for local logistic companies, but also for international applications in the context of projected glo bal macroeconomic and current national crisis phenomena.

DESIGN OF WIRELESS INTRUSION DETECTION SYSTEM FOR DOS ATTACK AND MALICIOUS ACCESS POINT IN WI-FI NETWORKS

The IEEE 802.11 wireless networks are organized either in infrastructure mode or ad-hoc mode. These wireless networks are very common, because of their portability and ease of access. In infrastructure mode of wireless networks, wireless clients have to be aware of the environments due to vulnerability and various types of attacks that can made by wireless intruders. Wired Equivalent Privacy (WEP) and Wi-Fi Protected Access (WPA) security protocols are used to protect any wireless infrastructure against wireless intruders. The main problem of wireless network is to maintain the network security. Firewalls are not much capable to secure network from attacks because firewall can only detect the attacks which come from outside of the network. Therefore, Intrusion Detection System (IDS) plays an important role in network security. In general Intrusion Detection System (IDS) is used to detect unauthorized access, malicious access point and various types of wireless attacks in IEEE 802.11 infrastructure mode of wireless networks. Network based Wireless Intrusion Detection system (WIDS) is designed to detect Denial of Service (DOS) attack and Malicious Access Point (Evil Twin Attack) in Wi-Fi networks. Because DOS attack and Evil Twin Attack are the most significant attacks in IEEE 802.11 networks. In this work, a diverse detection algorithm is proposed to detect DOS attack and Evil Twin Attack which is based on number of deauthentication frames and beacon frames and some other fields. In this project, an experimental setup for wireless network infrastructure with one access point (AP) and three or four number of wireless clients are used to design Wireless Intrusion Detection System (WIDS). In that design, one client act as an attacker and another one client act as detector. In this work, Kali Linux based attack software tool is used to register wireless clients to launch attacks on the network. The set of commends are used to configure on the designed infrastructure wireless networks for testing the attacks and solutions

UAV Communication Networks Issues: A Review

The unmanned aerial vehicle communication networks (UAVCN) comprises of a collection of unmanned aerial vehicles (UAVs) to build a network that can be used for many applications. These nodes autonomously fly in free space in ad-hoc mode to carry out the mission. However, the UAVs face some challenging issues during collaboration and communication. These nodes have high speed, hence the communication links fail to route the traffic that affects the routing mechanism. Therefore, UAVCN communication affecting the quality of service and facing the performance issue. Power is another major problem to limit and optimize the use of power, the energy-efficient mechanism is needed. In this paper, an attempt is made to explore the issues of unmanned aerial vehicle communication networks: UAVCN characteristics, UAVCN design issues, UAVCN applications, routing protocols, quality of service, power issue and identify the future open research areas which could be considered for further research to explore the UAVCN technology.

Analysis of a S-TDMA distributed scheduler for ad-hoc cellular-V2X communication

The cellular industry recently proposed a Long Term Evolution (LTE) extension supporting direct Vehicle to Everything (V2X) communication in full ad-hoc mode. Without infrastructure support, a distributed scheduler will play a critical role to the performance of such Cellular-V2X (C-V2X) technology. Self-Organizing TDMA (S-TDMA) is a reliable semi-deterministic and context aware distributed channel access algorithm, which has been considered by European Telecommunications Standard Institute (ETSI) as an attractive alternative to its WiFi-V2X standard, ITS-G5.In this paper, we describe S-TDMA, and present an analytical model to determine its packet reception performance. We then describe and analyze the performance of a distributed Cellular-V2X scheduler based on S-TDMA. We notably illustrate half-duplex issues impacting its performance in a C-V2X context, and propose two extensions to mitigate them. We finally compare their performance against each other, confirming S-TDMA’s potential as distributed scheduler for the future cellular-based V2X technology.

Design and Deployment of UAV-Aided Post-Disaster Emergency Network

Designing a reliable, resilient, and quickly deployable emergency communication network is a key challenge for post-disaster management. In this paper, a UAV-assisted emergency Wi-Fi network is proposed to expedite the rescue operations by guiding the survivors to the nearest rescue camp location. Here, the Raspberry PI (RPI) development board, mounted on UAV is considered to form a Wi-Fi chain network over the disaster region. During network set-up, the proposed solutions for the design challenges like UAV synchronization, avoid communication disruption and surveillance data management are the key contributions of this paper. The designed UAV network is capable of doing on-site surveillance and transmitting the data to the relief center for better rescue planning. One major challenge is to alert a survivor about the emergency network, which is addressed by designing a captive portal. Furthermore, to extend the Wi-Fi network, an Android-based application is developed by which each smartphone acts as a relay for its neighbor. Three types of field experiment are carried out to evaluate the performance of the designed prototype. It is found from the field results; the Wi-Fi access point mode and user datagram protocol are more suitable for network design as compared to Ad-Hoc mode and transmission control protocol, respectively. It is also observed from the experiment that the maximum hop distance for the prototype is 280 meters and 290 meters for a Wi-Fi configuration following IEEE 802.11n and IEEE 802.11ac protocol, respectively.

A Wi-Fi based Electronic Road Sign for Enhancing the Awareness of Vehicle Driver

Reducing the road accident rate is one of the city goal in the area of transportation. One of the effort to reach that goal is done by deploying various signs across the road. However, the role of those road signs can be diminished once the vehicle drivers intentionally or unintentionally disobey the rule indicated on those signs. In order to increase the awareness of the driver, we can employ the vehicular network concept in which a vehicle can communicate with another vehicles or with the infrastructure installed along the road. For realizing that idea, we propose the implementation of communication equipped road sign system which consists of two components: Road Side Unit (RSU) module deployed at road sign and On Board Unit (OBU) module deployed at each vehicle. In our proposed scheme, both of the devices communicate each other through the widely-used Wi-Fi protocol (IEEE 802.11n) operating in ad-hoc mode. While a OBU equipped vehicle is moving towards the communication range of RSU, it will make an association to a predefined wireless ad-hoc network. Once it is associated, the OBU can receive message broadcast by the RSU. Upon reception, OBU display alert message indicating that the vehicle is approaching a road sign. From performance testing we observe that the proposed system can give relatively good service the vehicle moving as fast as speed 90km/h with the distance as far as 90m.

Distributed throughput optimization for heterogeneous IEEE 802.11 DCF networks

For IEEE 802.11 DCF networks in ad-hoc mode, how to achieve the maximum throughput in a distributed manner draws much attention in previous studies. The problem becomes challenging for partially-saturated heterogeneous networks with multiple groups, as the optimal access parameters not only depend on the group size of saturated groups but also the aggregate input rate of all the unsaturated groups, both of which are hard to obtain without a central controller. In this paper, a novel distributive scheme is proposed for partially-saturated heterogeneous IEEE 802.11 DCF networks to achieve the maximum network throughput. With the proposed scheme, each saturated transmitter can obtain the optimal initial backoff window size distributively by two estimation rounds. In each estimation round, each saturated transmitter only needs to count the number of busy intervals and ACK frames on the channel. For fully-saturated networks, only one estimation round is needed. It is shown by extensive simulations that the proposed scheme can achieve the maximum network throughput in a distributive manner.

A Distributed Three-Hop Routing Protocol to Increase the Capacity of Hybrid Wireless Networks

Hybrid wireless networks combining the advantages of both mobile ad-hoc networks and infrastructure wireless networks have been receiving increased attention due to their ultra-high performance. An efficient data routing protocol is important in such networks for high network capacity and scalability. However, most routing protocols for these networks simply combine the ad-hoc transmission mode with the cellular transmission mode, which inherits the drawbacks of ad-hoc transmission. This paper presents a Distributed Three-hop Routing protocol (DTR) for hybrid wireless networks. To take full advantage of the widespread base stations, DTR divides a message data stream into segments and transmits the segments in a distributed manner. It makes full spatial reuse of a system via its high speed ad-hoc interface and alleviates mobile gateway congestion via its cellular interface. Furthermore, sending segments to a number of base stations simultaneously increases throughput and makes full use of widespread base stations. In addition, DTR significantly reduces overhead due to short path lengths and the elimination of route discovery and maintenance. DTR also has a congestion control algorithm to avoid overloading base stations. Theoretical analysis and simulation results show the superiority of DTR in comparison with other routing protocols in terms of throughput capacity, scalability, and mobility resilience. The results also show the effectiveness of the congestion control algorithm in balancing the load between base stations.

Cluster Connectivity Assurance Metrics in Vehicular ad hoc Networks

Many applications introduced by Vehicular Ad-Hoc Networks (VANETs), such as intelligent transportation and roadside advertisement, make VANETs become an important component of metropolitan area networks. In VANETs, mobile nodes are vehicles which are equipped with wireless antennas; and they can communicate with each other by wireless communication on ad-hoc mode or infrastructure mode. Clustering vehicles into different groups can introduce many advantages for VANETs as it can facilitate resource reuse and increase system capacity. The main contribution of our work is a new strategy for clustering a VANET and improvements in many classical clustering metrics. One of the main ideas is the definition of a new optimized selection metric for the clustering of vehicular nodes, in the framework of Next Generation Vehicular ad-hoc Network. These metrics should select clusterheads which provide safe clusters and avoid collisions with adjacent vehicle nodes and intend to create stable clusters by reducing reclustering overhead and prolonging cluster lifetime

Delay minimization by exploring full-duplex capacity and relay-based cooperative scheduling in WLANs

The research breakthrough on the hardware implementation of wireless full-duplex transmission has attracted significant interests on building full-duplex wireless networks in recent years. However, due to the asymmetry of real traffic flows, it is challenging to improve the network performance by effectively utilizing the full-duplex capacity. In this paper, we investigate the transmission delay minimization problem of full-duplex WLANs under ad-hoc mode. We first derive a lower bound of the total transmission delay and then propose a relay-based cooperative schedule scheme named CR-Mechanism, via exploiting eligible full-duplex communication opportunities. Our theoretical analysis shows that it achieves such lower bound with a polynomial-time complexity. Furthermore, the closed-form expressions of the expectation of totaly delay, time saving and transmission cost of CR-Mechanism are also derived. The extensive experimental results confirm that CR-Mechanism is an optimal scheduling algorithm with better performance than conventional mechanisms under different traffic models.

Design and Analysis of a Novel Hybrid Wireless Mesh Network Routing Protocol

Wireless mesh network (WMN) operates both in infrastructure and ad-hoc mode. It provides extended network coverage based on heterogeneous wireless technologies through multi-hop communications. In WMNs, the routing mechanisms and network organization need to be improved so that optimal path discovery or different protocols adaptability can be achieved. Hybrid routing is a demanding issue to be discussed these days as need of higher mobility management in the diverse situations and environments. It's required to improve the older schemes for higher data rate and minimum energy consumptions. The proposed work presents a design of a novel routing algorithm for optimal route discovery, congestion reduction, dynamic route selection and scalability in hybrid mesh networks. The authors have focused on Hybrid Routing Protocols to originate a novel routing scheme based on AODV (Ad hoc On-Demand Distance Vector routing protocol) in Ad-Hoc level with clustering scheme and DSDV (Destination Sequence Distance Vector) as proactive routing protocol in Backbone Mesh Router Level to form a new hybrid routing protocol. In this work a Novel Hybrid Distance Vector (NHDV) routing protocol algorithm has been introduced, which is the combination of DSDV (Destination Sequence Distance Vector) and AODV routing protocols. A clustering scheme with the combination of two efficient clustering schemes for Ad-hoc mesh client levels is discussed in detail and a performance metric for DSDV is also discussed which ETX (Expected Transmission Count) is for measuring packet loss ratio at each link for higher throughput. A new performance metric introduced in AODV as Mesh Router Count is used to improve the performance of communication to the Mesh Routers. The proposed work is the design of new algorithm that presents an optimal solution in bringing out a revolutionary change to Hybrid Routing.

Security Threats in Manets: A Review

Ad hoc networks are the special networks formed for specific applications. Operating in ad-hoc mode allows all wireless devices within range of each other to discover and communicate in a peer-to-peer fashion without involving central access points. Many routing protocols like AODV, DSR etc have been proposed for these networks to find an end to end path between the nodes. These routing protocols are prone to attacks by the malicious nodes. There is a need to detect and prevent these attacks in a timely manner before destruction of network services.

SECURITY IN AD-HOC NETWORKS

On wireless computer networks, ad-hoc mode is a method for wireless devices to directly communicate with each other. Operating in ad-hoc mode allows all wireless devices within range of each other to discover and communicated in peer-to-peer fashion. One main challenge in design of these networks is their vulnerability to security attacks. The growing popularity and widespread applications of wireless networks are directly proportionate to their propensity for security exploitation. In this paper we have discussed about the potential attacks and security issues of routing protocols face by ad-hoc network.

Optimal Client-Server Configuration of Mobile Ad-Hoc Networks

Abstract Interactive online gaming is a widely successful application that is becoming more and more popular even on mobile devices. In this context, an emerging scenario is represented by having playersʼ mobile devices directly connected to each other, without resorting to the Internet. To enable this scenario, we leverage on a hybrid architecture that allows client-server games to be played in ad-hoc mode: a number of players take turn in acting also as the server of the game. However, the problem on how to choose the servers so as to maximize the duration of the network still remains an issue. To this aim, we propose an Integer Programming model and a heuristic based on it: preliminary experimental results show the effectiveness and the potential of the approach.

Application and mobility aware integration of opportunistic networks with wireless infrastructures

The wireless world is migrating towards an era that will comprise wireless network infrastructure, as well as more temporary structures which, for instance, can be called Opportunistic Networks (ONs). ONs can comprise various terminals, potentially organized in an ad-hoc mode, and be terminated at a set of access points of the infrastructure-based network. In this context, an operator, owning a wireless network infrastructure, can exploit ONs for complementing the infrastructure, e.g., in order to resolve coverage expansions or for achieving green targets. Given the existence of opportunities in terms of available nodes and spectrum, the suitability of creating an ON can be determined by the type of involved applications and mobility levels. The decision to create or not an ON will be dynamic, should respect traffic and mobility aspects and should also envisage anticipated QoS and energy related benefits for the whole network. Framed within this statement, this paper aims at the investigation of those conditions under which the creation of an ON will be beneficiary for the overall network. This investigation is based on extensive network simulations and under certain circumstances the scheme may designate solutions that can offer adequate QoS.

Performance of CSMA in multi-channel wireless networks

We analyze the performance of CSMA in multi-channel wireless networks, accounting for the random nature of traffic. Specifically, we assess the ability of CSMA to fully utilize the radio resources and in turn to stabilize the network in a dynamic setting with flow arrivals and departures. We prove that CSMA is optimal in the ad-hoc mode, when each flow goes through a unique dedicated wireless link from a transmitter to a receiver. It is generally suboptimal in infrastructure mode, when all data flows originate from or are destined to the same set of access points, due to the inherent bias of CSMA against downlink traffic. We propose a slight modification of CSMA that we refer to as flow-aware CSMA, which corrects this bias and makes the algorithm optimal in all cases. The analysis is based on some time-scale separation assumption which is proved valid in the limit of large flow sizes.

Resource Allocation Schemes for the Heterogeneous OFDMA System with Multiple Ad Hoc Relays

In this paper, we present a heterogeneous network framework involved an orthogonal frequency division multiple access (OFDMA) network with an out-of-band Ad Hoc network, which maybe a promising architectural upgrade and has not been studied so far. In the heterogeneous system, the mobile stations (MSs) are dual-mode with both cellular OFDMA and Ad Hoc radios. And MSs communicate with the base station by cellular OFDMA mode, while they communicate with each other by Ad Hoc mode. An active MS can choose multiple inactive MSs as its relay stations (RSs). And each RS operates in a full duplex mode, that is, it can receive data through Ad Hoc network in the first hop and transmit data through the OFDMA network in the second hop, simultaneously. Based on this heterogeneous system, the problem of joint relay selection, subcarrier and power allocation with the objective of maximizing the system capacity under individual rate and transmit power constraints is addressed. We propose a dual-based resource allocation scheme to solve the problem fairly and efficiently, and then we propose a fully distributed resource allocation scheme to decrease the computational complexity. Simulation results show that the performance of the proposed dual-based resource allocation scheme, in terms of the system capacity and the outage probability, is better than that of the fully distributed resource allocation scheme. However, the performance improvement is at the expense of a high computational complexity.