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The North Atlantic is one of the world’s airspaces accommodating a very high aircraft density while at the same time no radio coverage or radar surveillance is available. Beside satellite communication, one approach to enable data communication between aircraft and ground in the North Atlantic region is to establish ad-hoc networks build up by direct data links between the aircraft that are acting as communication nodes. In this paper we, therefore, present a modeling approach to model air traffic and ad-hoc networks in the North Atlantic region using up-to-date flight plans and trajectory modeling techniques and to assess the connectivity provided by such networks. Assuming an applicable set of ground stations that provide data transfer to and from this airborne network, we assess the connectivity by time-series analysis and in total for a set of different fractions of all aircraft assumed to be equipped with the necessary systems as well as for a variation of the air-to-air communication range. In addition, we present average link durations, average amounts of hops to reach ground and numbers of connected aircraft for the different scenarios and identify general relations between the different factors and metrics. We will show, that communication range and equipage fraction significantly influence the connectivity of such networks.

Vehicular ad-hoc network (VANET) is a technique that uses cars moved in cities or highways as nodes in wireless networks. Each car in these networks works as a router and allows cars in the range to communicate with each other. As a result of this movement, some cars will become out of range, but these networks can connect to the internet and the cars in these networks can connect to each other. This research proposes a unique clustering strategy to improve the performance of these networks by making their clusters more stable. One of the biggest problems these networks face is traffic data, which consumes network resources. Agent based modeling (ABM) evaluates better networks. The evaluation showed that the proposed strategy surpasses earlier techniques in reachability and throughput, but ad hoc on-demand distance vector (AODV) (on-demand/reactive) outperforms it in total traffic received since our hybrid approach needs more traffic than AODV.

Mobile ad-hoc networks (MANETs) have limited network resources such as node battery capacity and wireless frequency bands. Therefore, to ensure efficient broadcast communication in such networks, it is critical to reduce unnecessary packet transfers and maximize the use of network resources and power. Network coding (NC) is a technique for reducing the number of transmitted packets over a network and maximizing the use of devices and network resources. The packet-reduction benefits obtained using NC depend considerably on network topology. In this study, we propose an NC method particularly designed for MANETs. In our approach, the nodes switch the type of transmission between an uncoded transmission (simple broadcast) and a coded transmission (NC) based on the estimated neighboring node’s proximity. The effectiveness of the proposed method was evaluated using computer simulations. Our evaluations demonstrated that the proposed method can reduce the number of packets in the network without decreasing the packet delivery rate.

The rapid rate of dependence over internet usage using digital devices also results in enormous data traffic. The conventional way to handle these services is to increase the infrastructure. However, it results in high cost of implementation. Therefore, to overcome the data burden, researchers have come up with data offloading schemes using solutions for NP-hard Target Set Selection (TSS) problem. Our work focuses on TSS optimization and respective data offloading scheme. We propose a heuristics-based optimal TSS algorithm, a distinctive community identification algorithm, and an opportunistic data offloading algorithm. The proposed scheme has an overall polynomial time complexity of the order O(k3), where k is the number of nodes in the primary target set for convergence. However we have obtained its realization to linear order for practical reasons. To validate our results, we have used state-of-the-art datasets and compared it with literature-based approaches. Our analysis shows that the proposed Final Target Set Selection (FTSS) algorithm outperforms the greedy approach by 35% in terms of traffic over cellular towers. It reduces the traffic by 20% as compared to the heuristic approach. It has 23% less average latency in comparison to the community-based algorithm.

Routing is a crucial component in the design of Flying Ad-Hoc Networks (FANETs). State of the art routing solutions exploit the position of Unmanned Aerial Vehicles (UAVs) and their mobility information to determine the existence of links between them, but this information is often unreliable, as the topology of FANETs can change quickly and unpredictably. In order to improve the tracking performance, the uncertainty introduced by imperfect measurements and tracking algorithms needs to be accounted for in the routing. Another important element to consider is beamforming, which can reduce interference, but requires accurate channel and position information to work. In this work, we present the Beam Aware Stochastic Multihop Routing for FANETs (BA-SMURF), a Software-Defined Networking (SDN) routing scheme that takes into account the positioning uncertainty and beamforming design to find the most reliable routes in a FANET. Our simulation results show that joint consideration of the beamforming and routing can provide a 5% throughput improvement with respect to the state of the art., This project has received funding from the European Union's Horizon 2020 research and innovation program under the Marie SklodowskaCurie Grant agreement No. 813999. The work of A. Pastore and X. Mestre was supported by Grant RTI2018-099722-B-I00 funded by MCIN/AEI/10.13039/501100011033 and by "ERDF A way of making Europe". The author affiliations and emails are as follows: © 2022, IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other work.

Control and user (data) plane separation (CUPS) is a concept applied in various networking areas to scale network resources independently, increase the quality of service, and facilitate the autonomy of networks. In this study, we leverage this concept to design a plane-separated routing algorithm, CUPS-based hierarchical routing algorithm (CHRA), as an energy-efficient and low-latency end-to-end communication scheme for clustered ad-hoc networks. In CHRA, while cluster heads constitute the control plane to conduct network discovery and routing, ordinary nodes residing in the user plane forward packets according to the routing decisions taken by the control plane. Exploiting the CUPS, we avoid exhausting cluster heads by offloading packet-forwarding to ordinary nodes and improve the quality of service by utilizing alternative paths other than the backbone of cluster heads. Our simulation results show that CHRA offers a better quality of service in terms of end-to-end latency and data-to-all ratio, and promotes fairness in energy-consumption in both stationary and mobile scenarios.

Localization is one of the main problems in Mobile Wireless Sensor Networks, since it provides the location of an event occurrence. This paper presents a performance evaluation of the localization algorithms: Multilateration Algorithm, Weighted Multilateration Algorithm and Probabilistic Multilateration Algorithm (PMA). In addition, we propose an Improved Probabilistic Multilateration Algorithm that decreases the localization error of the interest node by using an approach that computes iteratively the position of a node of interest until it reaches the solution that minimizes the localization error. The proposed approach regards the noisy environment by its impact on a correlation matrix that involves the variance of the separation distance between the node of interest and the respective reference nodes (RNs). Furthermore, we also introduce a constant parameter called damping factor; which enhances the convergence of the localization algorithm providing the solution that minimizes the localization error. In this study, we evaluate localization algorithms in a single-hop and multi-hop scenarios considering a distribution with solid geometry of the RNs and randomly distributed RNs in both scenarios. The results we obtained show that our proposed algorithm Improved PMA presents a better performance according to the Normalized Root Mean Squared Error varying the number of reference nodes and noise proportion.

REACT is a distributed resource allocation protocol used to negotiate a max–min allocation of airtime for multi-hop ad hoc wireless networks. Two approaches are proposed for a node to realize its REACT allocation in a contention-based MAC protocol. This is achieved by tuning its contention window to a value that corresponds to its allocation. Only a change in the allocation, due to a change in local traffic requirements or local network views, results in re-tuning. The approaches for tuning are implemented in commercial Wi-Fi devices and their stability and convergence are studied experimentally in the w-iLab.t wireless network testbed. These properties are also studied analytically to support the experimental results. In addition, REACT is extended to support airtime reservations for multi-hop flows. With a reservation in place, multi-hop TCP flows exhibit improved performance metrics when running over REACT than when running over 802.11 DCF in the w-iLab.t testbed.

Autonomous vehicles are becoming a reality in places with advanced infrastructure to support their operations. In crowded places, harsh environments, missions that require these vehicles to be aware of the context in which they are operating, and situations requiring continuous coordination with humans such as in disaster relief, advanced-vehicle systems (AVSs) need to be better contextually aware. The vast literature referring to “context-aware systems” is still sparse, focusing on very limited forms of contextual awareness. It requires a structured approach to bring it together to truly realize contextual awareness in AVSs. This paper uses a human-AVSs (HAVSs) lens to polarize the literature in a coherent form suitable for designing distributed HAVSs. We group the relevant literature into two categories: contextual-awareness related to the vehicle infrastructure itself that enables AVSs to operate, and contextual-awareness related to HAVSs. The former category focuses on the communication backbone for AVSs including ad-hoc networks, services, wireless communication, radio systems, and the cyber security and privacy challenges that arise in these contexts. The latter category covers recommender systems, which are used to coordinate the actions that sit at the interface of the human and AVSs, human-machine interaction issues, and the activity recognition systems as the enabling technology for recommender systems to operate autonomously. The structured analysis of the literature has identified a number of open research questions and opportunities for further research in this area.

Multi-agent systems (MAS) rely on positioning technologies to determine their physical location, and on wireless communication technologies to exchange information. Both positioning and communication are affected by uncertainties, which should be accounted for. This paper considers an agent placement problem to optimize end-to-end communication quality in a MAS, in the presence of uncertainties. Using Gaussian processes (GPs), operating on the input space of location distributions, we are able to model, learn, and predict the wireless channel. Predictions, in the form of distributions, are fed into the communication optimization problems. This approach inherently avoids regions of the workspace with high position uncertainty and leads to better average communication performance. We illustrate the benefits of our approach via extensive simulations, based on real wireless channel measurements. Finally, we demonstrate the improved channel learning and prediction performance, as well as the increased robustness in agent placement.

During the last years, researchers have proposed solutions to help smartphones improve execution time and reduce energy consumption by offloading heavy tasks to remote entities. Lately, inspired by the promising results of message forwarding in opportunistic networks, many researchers have proposed strategies for task offloading towards nearby mobile devices, giving birth to the Device-to-Device offloading paradigm. None of these strategies, though, offers any mechanism that considers selfish users and, most importantly, that motivates and defrays the participating devices who spend their resources. In this paper, we address these problems and propose the design of a framework that integrates an incentive scheme and a reputation mechanism. Our proposal follows the principles of the Hidden Market Design approach, which allows users to specify the amount of resources they are willing to sacrifice when participating in the offloading system. The underlying algorithm, that users are not aware of, is based on a truthful auction strategy and a peer-to-peer reputation exchange scheme. Extensive simulations on real traces depict how our designed mechanism achieves higher offloading rate and produces less traffic compared to three benchmark algorithms. Finally, we show how collaborating devices get rewarded for their contribution, while selfish ones get sidelined by others.

From the radar and military research world’s, the Ultra-WideBand Impulse Radio (UWB-IR) was adopted in the telecommunications world in the 1990’. Currently, the UWB-IR technology is an interesting candidate for close range Wireless Sensors Networks (WSNs). It is particularly attractive for industrial sensor networks due to its resilience to multipath interference, simple transceiver circuitry, accurate ranging ability, and low transmission power. In order to secure data and communications in the Ad-Hoc UWB-IR networks, UWB-IR requires suitable encryption protocols. In this paper, we review and summarize the IEEE 802.15.4 security sub-layer protocol of UWB-IR based Symmetric Key Cryptography scheme. Then, we highlight the different vulnerabilities and weaknesses present in this type of scheme. Finally, we prove, after a deep examination of multiple Public Key Cryptography (PKC) schemes, that the certificateless one is the most suitable for Ad-Hoc UWB-IR networks characterized by nodes mobility. Indeed, we have also evaluated and analyzed the different public key cryptosystems (PKCS) and concluded that NTRU is the most optimum public key cryptosystem to be used with the certificateless scheme in order to secure data and communications in Ad-Hoc UWB-IR Networks. This is due to the fact that it is the fastest PKCS to provide different security levels at a high speed with very constrained resources.

Vehicular networks and their associated technologies enable an extremely varied plethora of applications and therefore attract increasing attention from a wide audience. However, vehicular networks also have many challenges that arise mainly due to their dynamic and complex environment. Fuzzy Logic, known for its ability to deal with complexity, imprecision, and model non-deterministic problems, is a very promising technology for use in such a dynamic and complex context. This article presents the first comprehensive survey of research on Fuzzy Logic approaches in the context of vehicular networks, and provides fundamental information which enables readers to design their own Fuzzy Logic systems in this context. As such, this article describes the Fuzzy Logic concepts with emphasis on their implementation in vehicular networks, includes classification and thorough analysis of the Fuzzy Logic-based solutions in vehicular networks, and discusses how Fuzzy Logic could be employed in the context of some of the key research directions in the 5G-enabled vehicular networks.

Многопутевая маршрутизация позволяет создавать и использовать несколько путей между парой «источник-получатель». За последние 15 лет разработано множество новых протоколов для Ad-hoc сетей, предназначенных для различных сценариев организации маршрутизации. Среди существующих сценариев одними из наиболее широко применяемых являются сценарии, обеспечивающие высокую производительность сети. Целью данного исследования является анализ и сравнение многопутевых протоколов маршрутизации, используемых в Ad-hoc сетях, для выбора протоколов, обеспечивающих наиболее высокую производительность сети., Багатомаршрутна маршрутизація дозволяє створювати і використовувати кілька шляхів між парою «джерело-одержувач». За останні 15 років розроблено безліч нових протоколів для Ad-hoc мереж, призначених для різних сценаріїв організації маршрутизації. Серед існуючих сценаріїв одними з найбільш широко застосовуваних є сценарії, які забезпечують високу продуктивність мережі. Метою даного дослідження є аналіз і порівняння багатомаршрутних протоколів маршрутизації, які використовуються в Ad-hoc мережах, для вибору протоколів, що забезпечують найбільш високу продуктивність мережі, In the past few years, we have seen a rapid expansion in the field of mobile computing due to the proliferation of inexpensive, widely available wireless devices. However, current devices, applications and protocols are solely focused on cellular or wireless local area networks (WLANs), not taking into account the great potential offered by Ad-hoc networking. Ad-hoc networks are wireless mobile networks that can operate without infrastructure and without centralized network management. In such networks, the wireless mobile nodes may dynamically enter the network as well as leave the network. Mobility and multipath are the main characteristics of Ad-hoc networks. Multipath routing allows to create and use multiple paths between a source-destination node pair. In the last 15 years designed hundreds of new routing protocols targeting the various scenarios of this design space. Among the existing scenarios, scenarios that provide high network performance are among the most used. The purpose of this study is to analyze and compare the multipath routing protocols used in Ad-hoc networks to select the protocols that provide the highest network performance.

The number of vehicles in the world's cities increases exponentially, this is the case of Latin American cities, and particularly in the city of Portoviejo, province of Manabí in Ecuador, has been growing considerably in recent years, the city has been expanding towards its surroundings. Due to this big number of vehicles, which also adds little planning to improve the use of public transport, little planning to improve urban vehicular flow, the centralization of administrative area and main shops in the city, are the main reasons why in certain times of the day the traffic can become a little slow. Universidad Técnica de Manabí, has the objective of modernizing the improvement of vehicular flow in its surroundings and in addition to automating the vehicular entrance to its facilities through the automation of the respective permit for visiting drivers and staff. In this paper we show the methodology and tools necessary to create a system to control vehicles entry and exit using a Raspberry Pi, an analysis of the different technologies that can be used to improve vehicular flow is also included, approaching the Internet of Things.

This paper focuses on how the probability can affect on the ad hoc routing protocols and especially on AODV regarding energy consumption. The evaluation of the performance of AODV with different message forwarding probability based on the mechanism that AODV protocol uses in order to forward the message in all nodes of the network. The evaluation of AODV protocol was carried out using network simulator-2 (NS-2), on 10 scales of probability. The outcome of this evaluation showed that using smaller probability than that of the original AODV protocol has, we can have better results on power consumption.

In this paper, we evaluate available bandwidth as a routing metric for IEEE 802.15.4-based ad-hoc networks. The available bandwidth on a data forwarding path is an approximation of the forwarding path’s residual data relaying capacity. High available bandwidth on a data forwarding path implies low data traffic load on the path, therefore data flows may experience low delay and high packet delivery ratio (PDR). Our aim is to evaluate available bandwidth as a routing metric. We present different available-bandwidth-based routing protocols for IEEE 802.15.40-based networks, namely: end-to-end available-bandwidth-based routing protocol (ABR), available bandwidth and contention-aware routing protocol (ABCR), and shortest hop-count and available-bandwidth-based opportunistic routing protocol (ABOR). Moreover, we also present variants of ABR and ABCR capable of distributing a flow’s data packets on multiple paths by maintaining the top K downstream nodes (the downstream nodes that advertised best data forwarding paths towards a sink node) corresponding to each sink node in a routing table. We focus on both single-sink and multi-sink networks. We performed extensive simulations, and the simulation results demonstrate that the available bandwidth routing metric shows better results when combined with a routing metric that helps to limit a data forwarding path’s length, i.e., shortest hop-count or intra-flow contention count. For multi-path data forwarding towards the same sink node, and at high traffic volumes, the available bandwidth metric demonstrates best performance when combined with the shortest hop-count routing metric.

Floating Content (FC) is a communication paradigm to locally share ephemeral content without direct support from infrastructure. It is based on constraining the opportunistic replication of content in a way that strikes a balance between minimizing resource usage and maximizing content availability among the intended recipients. However, existing approaches to management of FC schemes are unfit for realistic scenarios with non-uniform user distributions, resulting in heavy overdimensioning of resources allocated to FC. In this work, we propose a new version of FC, called Cellular Floating Content (CFC), which optimizes the use of bandwidth and memory by adapting the content replication and storage strategies to the spatial distribution of users, and to their mobility patterns. The main idea underlying our approach is to partition users into small “local communities”, and to optimally weight their contributions to the FC paradigm according to their specific mobility features, and to the resources required to achieve a target performance level. We characterize numerically the properties of the optimal strategies in a variety of mobility patterns and traffic conditions, showing the accuracy of our approach, and the significant savings it enables in the amount of resources necessary to run FC, which in a realistic setup can be as high as 27% with respect to traditional FC dimensioning strategies.

The rapid proliferation of the Internet of Things (IoT) has led to growth in the ad-hoc networking scenario. With the recent upcoming technologies of network programmability like SDN may be effectively integrated to create a communication platform. In this work, we present the details of our preliminary study of how to determine the effectiveness of an approach to build a cluster network using Software-Defined Networking (SDN). We will provide an overview of optimum path routing protocol with cluster interaction. Our proposed scheme is a starting point for some experiments providing perspective over SDN deployment in a cluster environment for IoT. With this aim in mind, we propose a routing protocol that manages routing tasks over Cluster-SDN. By using network virtualization and OpenFlow technologies to generate virtual nodes, we simulate a prototype system controlled by SDN. Our designed testbed, is a real openflow protocol evaluation environment comprising networks and applications, which provide flexible control of framework support for large scale experiments.

Centrality metrics are a key instrument for graph analysis and play a central role in many problems related to networking such as service placement, robustness analysis and network optimization. Betweenness centrality is one of the most popular and well-studied metric. While distributed algorithms to compute this metric exist, they are either approximated or limited to certain topologies (directed acyclic graphs or trees). Exact distributed algorithms for betweenness centrality are computationally complex, because its calculation requires the knowledge of all possible shortest paths within the graph. In this paper we consider load centrality, a metric that usually converges to betweenness, and we present the first distributed and exact algorithm to compute it. We prove its convergence, we estimate its complexity and we show it is directly applicable-with minimal modifications-to any distance-vector routing protocol based on Bellman-Ford. We finally implement it on top of the Babel routing protocol and we show that, exploiting centrality, we can significantly reduce Babel's convergence time upon node failure without increasing signalling overhead. Our contribution is relevant in the realm of wireless distributed networks, but the algorithm can be adopted in any distributed system where it is not possible, or computationally impractical, to reconstruct the whole network graph at each node and compute betweenness centrality with the classical approach based on Dijkstra's algorithm.

Energy constraints on wireless nodes represent a current field of research. Such restrictions are particularly significant because of the great amount of features and applications currently available on devices, which contribute to dramatically increase energy consumption. However, when transmitting delay-sensitive data, such as multimedia streaming, a balance between energy optimization and quality of service is required. In this sense, there are many works that address this issue from different layers of network architecture separately; however, a more efficient solution could be achieved by combining the management capabilities of the different layers and the joint use of such information, which is called a crosslayer mechanism. Moreover, despite the fact that the IEEE 802.11 standard defines an energy management mechanism at MAC level, it is envisaged only for structured networks, leaving just general guidelines for other kind of networks, such as Ad- Hoc networks. Therefore, as a first step towards the design of a cross-layer scheme, this paper analyzes the flaws of IEEE 802.11 standard as regards the infrastructureless mode and proposes an optimization mechanism for energy management in Ad-Hoc networks. The proposed approach is based on a buffering mechanism, which is able to increase power-saving periods of time in Ad-Hoc nodes. Simulations using NS3 indicate that it is possible to obtain higher levels of residual energy at the end of a transmission using the proposed scheme.

This paper analyzes the impact of error propagation on the achievable throughput and throughput-delay tradeoff in wireless networks. It addresses the particular class of multihop routing schemes for parallel unicast that achieve a throughput scaling of Theta(n(-1/2))per node in a network of n nodes. It is shown that in the finite-block-length case, necessitated by finite decoding memory at the nodes, the guaranteed per-node throughput in the network cannot scale better than o(n(-r)) per node for any r > 0. This bound on the guaranteed per-node throughput is tighter than the O(1/n) bound shown previously. Instead of focusing on the probability of error for each link, which is intractable, an approach of bounding mutual information is employed to show tight results on the achievable throughput and throughput-delay tradeoffs. It is shown that for multihop transmission protocols, error propagation leads to significant changes in the tradeoff between the throughput T (n) and the delay D(n), compared to previous results. The best known scaling behavior is only D(n) = Theta(n (log n) T (n)) under maximum throughput scaling, where the block length required scales as Omega(log n). When decoding memory at nodes is constrained to be O(log log n), the achievable tradeoff worsens to D(n) = Theta(n (log n)(2) T (n)) QC 20140602

This paper analyzes the problem of modeling the collisions in a distributed and heterogeneous fixed wireless network in which spatial reuse enables multi-packet communication (MPC), thus allowing the coexistence of multiple peer to peer communications. The objective is to present a completely theoretical model that provides closed form expressions for the capture probability, and for the statistics of the interference power and of the signal-to-interference ratio (SIR) experienced by a receiving node. The presented theory aims in particular to investigate the impact on the capture probability of the heterogeneity introduced by the network topology and by the use of different antenna systems. All theoretical results are validated by independent Monte Carlo simulations. Finally, this study discusses the possible analogies between the developed and the existing frameworks for homogeneous scenarios, and presents a preliminary application of the developed capture analysis by evaluating the throughput-delay behavior of a homogeneous 802.11 MPC network.

Interest in the cognitive radio sensor network (CRSN) paradigm has gradually grown among researchers. This concept seeks to fuse the benefits of dynamic spectrum access into the sensor network, making it a potential player in the next generation (NextGen) network, which is characterized by ubiquity. Notwithstanding its massive potential, little research activity has been dedicated to the network layer. By contrast, we find recent research trends focusing on the physical layer, the link layer and the transport layers. The fact that the cross-layer approach is imperative, due to the resource-constrained nature of CRSNs, can make the design of unique solutions non-trivial in this respect. This paper seeks to explore possible design opportunities with wireless sensor networks (WSNs), cognitive radio ad-hoc networks (CRAHNs) and cross-layer considerations for implementing viable CRSN routing solutions. Additionally, a detailed performance evaluation of WSN routing strategies in a cognitive radio environment is performed to expose research gaps. With this work, we intend to lay a foundation for developing CRSN routing solutions and to establish a basis for future work in this area.

In mobile ad hoc network, nodes co-operatively form a network independent of any fixed base station infrastructure. Every node in a mobile ad-hoc network can function as a router and forwards the data packets to the other nodes. Multicasting plays an important role whenever group communications are required. Most of the existing multicast routing protocols in mobile ad hoc networks consider only one source in a multicast group and become inefficient when the protocol is extended to multi-source multicasting. In this paper, we propose a unicast forwarded multi-source multicast routing protocol, for ad hoc networks which is having more than one source in a group. Here, the sources of the group also act as a receiver for other sources in that group. The proposed routing method is a cluster based one and avoids the flooding or broadcasting of control packets to form routing structure. On executing source joining and receiver joining procedures, a complete path for multicast data transfer was established. As the join request control packets are forwarded only through cluster-heads and junction nodes, lower amount of control overhead is incurred. Simulation result shows that the proposed protocol maintains the delivery ratio with reduced control overhead and utilizes the bandwidth efficiently.

We consider centralized and distributed algorithms for the numerical solution of a hemivariational inequality (HVI) where the feasible set is given by the intersection of a closed convex set with the solution set of a lower-level monotone variational inequality (VI). The algorithms consist of a main loop wherein a sequence of one-level, strongly monotone HVIs are solved that involve the penalization of the non-VI constraint and a combination of proximal and Tikhonov regularization to handle the lower-level VI constraints. Minimization problems, possibly with nonconvex objective functions, over implicitly defined VI constraints are discussed in detail. The methods developed in the paper are then used to successfully solve a new power control problem in ad-hoc networks. © 2013 Springer-Verlag Berlin Heidelberg and Mathematical Optimization Society.

The strengthening of security solutions for computer networks increases the interests in new methods for the transfer of hidden information. In this paper, we considered the use of routing protocols for transmission of steganographic messages. We evaluated such approach using proactive and reactive routing protocols by analyzing the amount of sent data, the number of generated routing packets, the average size of routing packets, and the packet delivery ratio using the NS-3 simulator. Simulations included random network topologies with a various number of nodes and mobility settings. The obtained results showed that reactive routing protocols exchange a large amount of routing packets which can be suitable for steganographic purposes due to network flooding mechanism.

Fast and efficient recovery from node failure, with minimal disruption of routes and the consequent traffic loss is of the utmost importance for any routing protocol. Link-state protocols, albeit preferred to distance vector ones because of faster convergence, still suffer from a trade-off between control message overhead and performance. This work formalizes the routes' disruption following a node failure as an optimization problem depending on the nodes' centrality in the topology, constrained to a constant signaling overhead. Next, it shows that the solution can be found using Lagrange Multipliers. The solution complexity is low enough to be computed on-line on the network routers, thus obtaining the optimal setting of control message timers that minimize the traffic loss following a node failure. The gain obtained is quantified in power-law synthetic topologies, and it is also tested on real network topologies extending the OLSR protocol to use the modified timers, showing that the inevitable approximations introduced in the analysis do not hamper the very good results achievable through this novel approach. The technique can be applied to any link state protocol, including OSPF, and improves route convergence not only upon failures but on every topology modification.

MANET (Mobile Ad-hoc Network) is a mobile multi-hop wireless self-organized distributed ad-hoc network thatdoes not require the basic internal construction. Routing in MANET is a challenging problem which draws researcher's vision, due to nodes mobility, dynamic topology and lack of central point like base station or servers. Clustering of devices in MANET could reduce overhead, flooding and collision in communication and make the network topology more stable. The ABC (Artificial Bee Colony) algorithm is a new meta-heuristic population based optimization technique inspired by the intelligent foraging behavior of honeybee swarms. In this paper, a new general framework has been proposed for achieving QoS which provides a cluster based routing and applies Artificial Bee Colony optimization Technique for effective optimal route discovery in MANET. It works on the principle of collective intelligence and emergence of artificial honey bees. It's application in ad-hoc networks involves swarming agents (honey bees) hopping node to node, analyzing a set of variables exposed by the nodes and provide the optimal path and minimize the routing overhead and also provides QoS guarantees with an ability for minimal end-to-end delay and enhanced scalability.

This paper provides a review of antennas applied for indoor positioning or localization systems. The desired requirements of those antennas when integrated in anchor nodes (reference nodes) are discussed, according to different localization techniques and their performance. The described antennas will be subdivided into the following sections according to the nature of measurements: received signal strength (RSS), time of flight (ToF), and direction of arrival (DoA). This paper intends to provide a useful guide for antenna designers who are interested in developing suitable antennas for indoor localization systems.

This paper proposes a new Ad-Hoc network system which comprises the multiple relay access points (APs) with multi channels. Ad-Hoc network systems are recently proposed and incorporated for the communication infrastructure, which relays wireless transmission among access points (APs) in wireless LAN (WLAN) system. System throughput is decreased due to hidden terminal problem when only a single channel is used for the Ad-Hoc network. In order to solve this problem, a new system with multi channels is proposed. However, even if the multi channels are employed, the co- and/or adjacent-channel interference occurs due to hidden terminal problem and multiple APs in a limited space, when considering a simultaneous transmit and reception at the relay AP. In this paper, we develop an Ad-Hoc network testbed which can reduce and avoid co- and/or adjacent-channel interference by using vertically arranged antenna configuration and distributed channel allocation scheme. Moreover, the effectiveness of our testbed is clarified by applying actual WLAN signals.

CoopMAC has been recently proposed as a possible implementation of cooperation protocols in the medium access control (MAC) layer of a wireless network. However, some nodes may refrain from cooperation for selfish purposes, e.g. in order to save energy, in what is called selfish behavior or misbehavior. This protocol violation worsens other nodes' performance and can be avoided if other nodes detect and punish (e.g. banning from the network) misbehaving nodes. However, fading and interference may prevent nodes from cooperating even if they are willing, therefore it is not trivial to identify misbehaving nodes. In a fading scenario where an automatic repeat request (ARQ) protocol is used, we propose a mechanism that allows to detect misbehaving nodes. Two approaches, either based on the uniformly most powerful (UMP) test or on the sequential probability ratio test (SPRT) are considered. The two techniques are characterized and compared in terms of their average detection delay and resulting network performance.

This paper presents a unified mathematical performance analysis of the physical layer in orthogonal frequency division multiple access (OFDMA) wireless ad hoc networks, where several independent transmitter-receiver pairs share a common wideband channel in a local area environment. Multiuser interference (MUI) occurs when the signals from different users arrive at a given receiver with arbitrary timing misalignments, leading to the destruction of the orthogonality between subcarriers. Precise interference analysis in white Gaussian noise and Rayleigh multipath fading is developed in a partially loaded OFDMA network. New exact expressions of symbol and bit error rates are given in the case of interleaved subcarrier assignment schemes. On the other hand, tight upper bounds and accurate improved Gaussian approximations are developed for arbitrary subcarrier assignment schemes. Furthermore, expressions of the cutoff rates are derived and employed to estimate the spectral efficiency in bits/sec./Hz. These are used to quantify the improvement in the spectral efficiency that can be achieved by a common MUI mitigating technique based on the extension of guard intervals and dynamic positioning of FFT windows. © 2006 IEEE.

We propose a probabilistic system model for anonymous ad hoc routing protocols that takes into account the a priori knowledge of the adversary, and illustrate how the information theoretical entropy can be used for quantification of the anonymity offered by a routing protocol as the adversary captures an increasing number of nodes in the network. The proposed measurement schema is applied to ANODR and ARM routing protocols.

A random geometric graph ${\mathcal{G}}(n,r)$ is obtained by spreading n points uniformly at random in a unit square, and by associating a vertex to each point and an edge to each pair of points at Euclidian distance at most r. Such graphs are extensively used to model wireless ad-hoc networks, and in particular sensor networks. It is well known that, over a critical value of r, the graph is connected with high probability. In this paper we study the robustness of the connectivity of random geometric graphs in the supercritical phase, under deletion of edges. In particular, we show that, for a sufficiently large r, any cut which separates two components of Θ(n) vertices each contains Ω(n2r3) edges with high probability. We also present a simple algorithm that, again with high probability, computes one such cut of size O(n2r3). From these two results we derive a constant expected approximation algorithm for the β-balanced cut problem on random geometric graphs: find an edge cut of minimum size whose two sides contain at least βn vertices each.

We investigate the connectivity of fading wireless ad-hoc networks with a pair of novel connectivity metrics. Our first metric looks at the problem of connectivity relying on the outage capacity of MIMO channels. Our second metric relies on a probabilistic treatment of the symbol error rates for such channels. We relate both capacity and symbol error rates to the characteristics of the underlying communication system such as antenna configuration,modulation, coding, and signal strength measured in terms of Signal-to-Interference-Noise-Ratio (SINR). For each metric of connectivity, we also provide a simplified treatment in the case of ergodic fading channels. In each case, we assume a pair of nodes are connected if their bi-directional measure of connectivity is better than a given threshold. Our analysis relies on the central limit theorem to approximate the distribution of the combined undesired signal affecting each link of an ad-hoc network as Gaussian. Supported by our simulation results, our analysis shows that (1) a measure of connectivity purely based on signal strength is not capable of accurately capturing the connectivity phenomenon, and (2) employing multiple antenna mobile nodes improves the connectivity of fading ad-hoc networks.

In this work we focus on investigating the learning phase of an autonomous authentication mechanism. Through a series of simulation, an experimental best cutoff point and the aggression threshold values for different network size were calculated. In the test phase, those found values are proved by the average good accuracy.

Opportunistic traffic offloading has been proposed to tackle overload problems in cellular networks. However, existing proposals only address device-to-device-based offloading techniques with deadline-based data propagation, and neglect content injection procedures. In contrast, we tackle the offloading issue from another perspective: the base station interference coordination problem during content injection. In particular, we focus on dissemination of contents, and aim at the minimization of the total transmission time spent by base stations to inject the contents into the network. We leverage the almost blank subframe technique to keep under control the intercell interference in such a process. We formulate an optimization problem, prove that it is NP-hard and NP-complete, and propose a near-optimal heuristic to solve it. Our algorithm substantially outperforms classical intercell interference approaches, as we evaluate through the simulation of LTE-A networks. This work has been initially supported by the FP7 CROWD Project under Grant 318115 and later on followed up by the H2020 5G NORMA Project under Grant 671584. The work of V. Mancuso was supported by the Ramon y Cajal Grant from the Spanish Ministry of Economy and Competitiveness under Grant RYC-2014-01335.

One of the most present issues of computer wireless networks is the security. Comparing with their wired counterpart, the wireless networks not only accentuate some of the well-known security vulnerabilities but they are subject of new and specific ones. Among the existing wireless networks the ad hoc ones are the most exposed to attacks and collusions due to the absence of any centralized control. The most efficient way to ensure the communication secrecy, inclusively for ad hoc wireless networks, is the cryptography. From many reasons, following from specific operating conditions, the employment of asymmetric key techniques and Public Key Infrastructure is not a realistic choice. In the networks with a large number of nodes, as wireless sensor networks, a large number of secret keys are involved in order to ensure the communication secrecy. While dynamicity is one of the essential features of mobile wireless networks, when nodes may leave or join the network and in the absence of a centralized control entity, the management of secret keys is crucial. The paper presents the main aspects of mobile wireless networks security and focuses on the key management issue in ad-hoc wireless networks.

Thanks to the widespread use of wireless systems with the Android operating system, the presence of intelligent devices that can access the network is increasingly high. Wireless Mesh Networks are proposed today as the enabling technology to increase even more the pervasiveness of the Internet access and as a alternative to overcome typical limitations of existing infrastructure, but there have not been so far substantial contributions about the integration of different technologies. Furthermore, nowadays heterogeneous networks are a promising reality; a seamless integration of different technologies would leverage them to a key element to increase pervasiveness of access and connectivity in the emerging view of the Internet of Things. In this perspective the present paper proposes an open source implementation of an ad-hoc network based on mobile devices running Android, along with its integration with the infrastructured network, in an IPv4/IPv6 dual stack environment. The use of commercial devices for the end-user terminals and the leverage of the infrastructured network on widely used routing protocols enable this solution to be easily deployable in the real world. The developed test bed provides a novel and flexible framework for validation of networking solutions in emerging scenarios with heterogeneous network components.

Topology control, wherein nodes adjust their transmission ranges to conserve energy and reduce interference, is an important feature in wireless ad hoc networks. Contrary to most of the literature on topology control which focuses on reducing energy consumption, in this paper we tackle the topology control problem with the goal of limiting interference as much as possible, while keeping the communication graph connected with high probability. Our approach is based on the principle of maintaining the number of physical neighbors of every node equal to or slightly below a specific value k. As we will discuss in this paper, having a nontrivially bounded physical node degree allows a network topology with bounded interference to be generated. The proposed approach enforces symmetry on the resulting communication graph, thereby easing the operation of higher layer protocols. To evaluate the performance of our approach, we estimate the value of k that guarantees connectivity of the communication graph with high probability both theoretically and through simulation. We then define k-NEIGH, a fully distributed, asynchronous, and localized protocol that uses distance estimation. k-NEIGH guarantees logarithmically bounded physical degree at every node, is the most efficient known protocol (requiring 2n messages in total, where n is the number of nodes in the network), and relies on simpler assumptions than existing protocols. Furthermore, we verify through simulation that the network topologies produced by k-NEIGH show good performance in terms of node energy consumption and expected interference

The throughput of wireless networks is known to scale poorly when the number of users grows. The rate at which an arbitrary pair of nodes can communicate must decrease to zero as the number of users tends to infinity, under various assumptions. One of them is the requirement that the network is fully connected: the computed rate must hold for any pair of nodes of the network. We show that this requirement can be responsible for the lack of throughput scalability. We consider a two-dimensional network of extending area with only one active source-destination pair at any given time, and all remaining nodes acting only as possible relays. Allowing an arbitrary small fraction of the nodes to be disconnected, we show that the per-node throughput remains constant as the network size increases. This result relies on percolation theory arguments and does not hold for one-dimensional networks, where a non-vanishing rate is impossible even if we allow an arbitrary large fraction of nodes to be disconnected. A converse bound is obtained using an ergodic property of shot noises. We show that communications occurring at a fixed non-zero rate imply some of the nodes to be disconnected. Our results are of information theoretic flavor, as they hold without assumptions on the communication strategies employed by the network nodes.

Network coding is a new research area that may have interesting applications in practical networking systems. With network coding, intermediate nodes may send out packets that are linear combinations of previously received information. There are two main benefits of this approach: potential throughput improvements and a high degree of robustness. Robustness translates into loss resilience and facilitates the design of simple distributed algorithms that perform well, even if decisions are based only on partial information. This paper is an instant primer on network coding: we explain what network coding does and how it does it. We also discuss the implications of theoretical results on network coding for realistic settings and show how network coding can be used in practice

In ad-hoc networks, autonomous wireless nodes can communicate by forwarding messages for each other. For routing protocols in this setting, it is known that a malicious node can perform a variety of attacks just by not behaving according to the specification. Whilst secure versions of routing protocols are under development, little effort has been made to formalise the scenario similarly to developments in the realm of traditional security protocols for secrecy and authentication. We present a broadcast process calculus suitable to describe the behaviour of protocols which require a local memory component for every node. By adding annotations for the origin of messages, we are able to formalise a vital security property in this context, called store authorisation. Furthermore, we describe a static analysis for the detection of violations of this property. For a model of the AODV protocol in our calculus, we are then able to deduce that an attacker may introduce a routing loop in certain networks.

Locating and obtaining context sensitive information in a mobile environment has always been a challenge. This is especially true for pervasive computing environments where in addition to limited computing and battery resources, mobile devices cannot always rely on the help of a proxy-based wired infrastructure. Rather, a collaboration among peer mobile entities is required. It allows entities to obtain data that may be otherwise inaccessible due to nature of the environment and to reduce their computation cost by reusing answers generated by other peers. We introduce the problem of data interaction among peers in ad-hoc networks and propose a collaboration query processing protocol based on the principles of Contract Nets. Once an entity identi es information it needs via the help of user's pro les, our protocol enables the device to locate data sources and obtain data matching its speci c query requiring one or more data sources. We show the effectiveness of our technique through performance evaluation of entities querying for data while moving in a city-like environment.

Network Coding (NC) is a new area which brings radical change in the way we treat information flow in networks. NC considered being a layer 3 operation has been shown to improve the throughput of wired networks especially for broadcast and multicast traffic. Linear network coding (LNC) in which packets are combined using simple linear operations over finite fields can indeed achieve the multicast capacity. Random LNC (RLNC) is attractively used for distributed scenario where the codes are generated by various nodes in random fashion. The data dissemination latency scales as O(N2) (N is the number of nodes) in naive broadcast scenario. However with RLNC the data dissemination latency scales between O(N) and O(N2) depending on the network connectivity. NC is at the heart of two problems that we have considered in this thesis. Firstly we consider collaborative distributed indoor target tracking using wireless sensor networks (WSNs) where we show how RLNC can be used for effective information dissemination and analyzed its impact on tracking performance for the case of indoor target tracking. Our simulation results demonstrate that for a target root mean square (RMS) value of tracking error the RLNC scheme would require less number of time slots in comparison with the two competing schemes. Secondly we consider the performance of NC in relay assisted contention based ad hoc networks considered like the IEEE 802.11 compliant ones. We specifically show as how MAC layer NC can be used at both relay, source & destination nodes to improve throughput in contention based wireless networks. Our simulation results demonstrate an increment in system throughput by 15-20% for the case with NC.

The growing need for multimedia applications within wireless Local Area Networks (LAN) demands reliable and efficient broadcasting and multicasting transmission of throughput sensitive data, like audio and video. IEEE 802.11 standard which is the primary technology in wireless LANs was not initially designed to handle heavy broadcasting traffic. However, this raises a series of reliability problems mainly related to the lack of an effective feedback mechanism for multicasting and broadcasting transmission. This inherited drawback does not allow the standard to take full advantage of the bandwidth offered by its latest amendments. The main aim of this work is to offer an alternative congestion control mechanism especially for broadcasting. For this, the expanding use of the CTS-to-Self protection mechanism is proposed. The Medium Access Control (MAC) algorithm is appropriately modified and tested under various data traffic conditions. The simulation shows that the use of this amended MAC method in conjunction with the suitable data packet size can significantly improve throughput, in multimedia type data broadcasting over wireless ad-hoc networks.

In recent years, continuous progress in wireless communication has opened a new research field in computer networks. Now a day’s wireless ad-hoc networking is an emerging research technology that needs attention of the industry people and the academicians. A vehicular ad-hoc network uses vehicles as mobile nodes to create mobility in a network. It’s a challenge to generate realistic mobility for Indian networks as no TIGER or Shapefile map is available for Indian Automotive Networks. This paper simulates the realistic mobility of the Vehicular Ad-hoc Networks (VANETs). The key feature of this work is the realistic mobility generation for the Indian Automotive Intelligent Transport System (ITS) and also to analyze the throughput, packet delivery fraction (PDF) and packet loss for realistic scenario. The experimental analysis helps in providing effective communication for safety to the driver and passengers

In wireless ad-hoc networks, communication is done mainly through intermediate nodes or relay nodes. The mobile nodes in ad-hoc network have limited energy, so the intermediate nodes or relay nodes do not always co-operate to transfer other nodes’ information. If all nodes start performing in the same manner, network performance will drop drastically and the whole network will get disconnected. Co-operation strategy is applied on communities instead of each node to get better network performance. A Community is created based on how strong a node is socially connected to other nodes, because a node will co-operate to those nodes who are having strong social ties with it (especially in energy constrained and selfish environments). Due to this, nodes in the same community will always co-operate to one another. After the community formation, Generous Tit - for - Tat (GTFT) co-operation strategy and other co-operation strategies are applied between communities for further communication. The community formation will make these strategies more scalable and results show that the performance of these strategies are good under heavy non co-operative or selfish networks.

Despite its obvious potential in many contexts, ad-hoc networks are still mostly unknown, not popular and not a clear choice in the absence of any other network infrastructure. Two main reasons may be pointed out: the difficulty to configure a secure ad-hoc environment and the lack of ease to use services targeted to such environments. In this work we describe the design and implementation of a complete framework for service support based on three major components (1) a set of auto-configuration mechanisms suitable for ad-hoc environments (2) a transport layer protocol that allows the transfer of authenticated messages (3) an easy to use and web-based service framework. We believe that only those three components together make the framework powerful and effectively easy to use for the auto deployment of useful services in ad-hoc environments., This work is partially funded by FEDER Funds through the Programa Operacional Fatores de Competitividade – COMPETE and by National Funds through the FCT - Fundação para a Ciência e a Tecnologia (Portuguese Foundation for Science and Technology) within project FCOMP-01-0124-FEDER-022674