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The fast evolutions of Internet of Things (IoT) technologies have been accelerating their applicability in different sectors of life and becoming a pillar for sustainable development. However, this revolutionary expansion led to a substantial increase in attack surface, raising many concerns about security threats and their possible consequences. Machine learning has significantly contributed to designing intrusion detection systems (IDS) but suffers from critical limitations such as data privacy and sovereignty, data imbalance, concept drift, and catastrophic forgetting. This collectively makes existing IDSs an improper choice for securing IoT environments. This paper presents a federated learning approach called FIDWATCH to continuously monitor and detect a broad range of IoT security threats. The local side of FIDWATCH introduces contrastive focal loss to enhance the ability of the local model (teacher) to discriminate between diverse types of IoT security threats while putting an increased emphasis on hard-to-classify samples. A fine-grained Knowledge Distillation (KD) is introduced to allow the client to distill the required teacher's knowledge into a lighter, more compact model termed the pupil model. This greatly assists the competence and flexibility of the model in resource-constrained scenarios. Furthermore, an adaptive incremental updating method is introduced in FIDWATCH to allow the global model to exploit the distilled knowledge and refine the shared dataset. This helps generate global anchors for improving the robustness of the mode against the distributional shift, thereby improving model alignment and compliance with the dynamics of IoT security threats. Proof-of-concept simulations are performed on data from two public datasets (BoT-IoT and ToN-IoT), demonstrating the superiority of FIDWATCH over cutting-edge performance with an average f1-score of 97.07% and 95.63%, respectively. [ABSTRACT FROM AUTHOR]

The fast advancement of quantum computing poses a substantial challenge to the privacy and security of critical scientific research data. This is because the standard cryptography methods, which have been proven effective in classical computers, are rendered less secure in the face of quantum computing approaches. Previously, numerous endeavors have been made to safeguard confidential information through the utilization of different standards and quantum cryptographic methods. However, there remains a research void with several challenges and limitations, including excessive computational burden, vulnerability to various attacks, and limited hardware compatibility for implementation. We propose a modern hybrid cryptographical approach to secure sensitive data from various attacks and vulnerabilities to address the existing limitations. The suggested standard integrates traditional cryptographic standards with quantum-resistant standards to boost sensitive scientific data privacy and security and address various classical cyber-attacks and critical quantum attacks. For the context of scientific data privacy and security, our work depicts a hybrid standard structure by performing a systematic exploration of current encipherment model challenges and issues such as the investigation of various susceptibilities of mathematical cryptographic models. In this work, we apply lattice-based coding as the outer layer and Advanced Encryption Standard (AES) as the inner layer to improve security and efficacy. The proposed security theorem launches the operational veracity of lattice-based coding in the face of quantum attacks, while a complete investigation of the proposed algorithm efficacy vitrines the enhanced security and scalability of the anticipated hybrid standard transversely diverse input sensitive data volumes. Furthermore, this proposed work offers the security confidence score of the hybrid model by the amalgamation of AES and lattice-based cryptography (LBC), hence guaranteeing strength next to both quantum and traditional computing weaknesses. The investigational results prove the improved efficiency of the proposed hybrid model in contrast to traditional and past quantum-resistant models. [ABSTRACT FROM AUTHOR]

Routing Protocol for Low Power and Lossy Networks (RPL) is the de-facto routing standard in IoT networks. It enables nodes to collaborate and autonomously build ad-hoc networks modeled by tree-like destination-oriented direct acyclic graphs (DODAG). Despite its widespread usage in industry and healthcare domains, RPL is susceptible to insider attacks. Although the state-of-the-art RPL ensures that only authenticated nodes participate in DODAG, such hard security measures are still inadequate to prevent insider threats. This entails a need to integrate soft security mechanisms to support decision-making. This paper proposes iTRPL , an intelligent and behavior-based framework that incorporates trust to segregate honest and malicious nodes within a DODAG. It also leverages multi-agent reinforcement learning (MARL) to make autonomous decisions concerning the DODAG. The framework enables a parent node to compute the trust for its child and decide if the latter can join the DODAG. It tracks the behavior of the child node, updates the trust, computes the rewards (or penalties), and shares them with the root. The root aggregates the rewards/penalties of all nodes, computes the overall return, and decides via its ϵ -Greedy MARL module if the DODAG will be retained or modified for the future. A simulation-based performance evaluation demonstrates that iTRPL learns to make optimal decisions with time. [ABSTRACT FROM AUTHOR]

Communication problems in ad hoc wireless networks have been already widely studied under the SINR model, but a vast majority of results concern networks with constraints on connectivity, so called strongly-connected networks. In such networks, connectivity is defined based on highly reliable links, that is, where both ends are located far closer from their transmission boundaries. What happens if the network is not strongly-connected, e.g., it contains some long but still viable "shortcut links" connecting transmission boundaries? It is known that even a single broadcast in such ad hoc weakly-connected networks with uniform transmission powers requires Ω (n) communication rounds, where n is the number of nodes in the network. The best up-to-date (randomized) distributed algorithm, designed by Daum et al. [1] , accomplishes broadcast task in O (n log 2 ⁡ n) communication rounds with high probability. In this work, inspired by the work on broadcasting, we show a novel deterministic distributed implementation of token traversal — a fundamental tool in distributed systems — in the SINR model with uniform transmission powers and no restriction on connectivity. We show that it is efficient even in a very harsh model of weakly-connected networks without GPS, carrier sensing and other helping features. We apply this method to span a traversal tree and accomplish broadcast in O (n log ⁡ N) communication rounds, deterministically, provided nodes are equipped with unique IDs in the range [ 1 , N ] for some integer N ≥ n. This result implies an O (n log ⁡ n) -round randomized solution that does not require IDs, which improves the result from [1]. The lower bound Ω (n log ⁡ N) for deterministic algorithms proved in our work shows that our result is tight without randomization. Our implementation of token traversal routine, efficient in terms of time and memory, is based on a novel implicit algorithmic carrier sensing method and a new type of selectors, which might be of independent interest and applicable to other communication tasks in distributed ad hoc setting. [ABSTRACT FROM AUTHOR]

Abstract Visible light communication (VLC) is a wireless technology complementary to well-understood radio frequency (RF) communication that is promising to help alleviate the spectrum crunch problem in overcrowded RF spectrum bands. While there has been significant advancement in recent years in understanding physical layer techniques for visible light point-to-point links, the core problem of developing efficient networking technology specialized for visible-light networks is substantially unaddressed. This article discusses the current existing techniques as well as the main challenges for the design of visible-light ad hoc networks - referred to as LANETs. The paper discusses typical architectures and application scenarios for LANETs and highlights the major differences between LANETs and traditional mobile ad hoc networks (MANETs). Enabling technologies and design principles of LANETs are analyzed and existing work is surveyed following a layered approach. Open research issues in LANET design are also discussed, including long-range visible light communication, full-duplex LANET MAC, blockage-resistant routing, VLC-friendly TCP and software-defined prototyping, among others. [ABSTRACT FROM AUTHOR]

Abstract This paper investigates the performance of MIMO ad hoc networks that employ transmit diversity, as delivered by the Alamouti scheme, and/or spatial multiplexing, according to the Vertical Bell Labs Layered Space-Time system (V-BLAST). Both techniques are implemented in the ns-3 network simulator by focusing on their overall effect on the resulting signal-to-interference-plus-noise ratio (SINR) at the intended receiver. Unlike previous works that have studied fully-connected scenarios or have assumed simple abstractions to represent MIMO behavior, this paper evaluates MIMO ad hoc networks that are not fully connected by taking into account the impact of multiple antennas on the carrier sense activity in CSMA-like medium access control (MAC) protocols. In addition to presenting a performance evaluation of ad hoc networks operating according to each individual MIMO scheme, this paper proposes simple modifications to the IEEE 802.11 DCF MAC to allow the joint operation of both MIMO techniques. Hence, each pair of nodes is allowed to select the best MIMO configuration for the impending data transfer. The joint operation is based on three operation modes that are selected based on the estimated SINR at the intended receiver and its comparison with a set of threshold values. The performance of ad hoc networks operating with the joint MIMO scheme is compared with the performance when using each individual MIMO scheme and the standard single-input single output (SISO) IEEE 802.11. Performance results are presented based on MAC-level throughput per node, delay, and throughput fairness under saturated traffic conditions. [ABSTRACT FROM AUTHOR]

DelPHI [1] is a highly cited protocol that secures Ad hoc On Demand Distance Vector (AODV) routing protocol against wormhole attacks. DelPHI assumes that the underlying wireless transmission rate is constant. Under such an assumption it has a wormhole detection rate above 80%. In this work we show that DelPHI is unable to secure AODV in a multirate transmission environment because it does not take into account the variable bit rate nature of the wireless channel and assumes a constant bit rate leading to either false detection or no detection of wormhole attacks. We go on to propose an extension to DelPHI (M-DelPHI) that adapts it to the multirate 802.11 wireless channel. We propose three fundamental extensions: 1. Multirate channel, 2. Processing delay and 3. Neighbour monitoring. We provide 2 test cases that demonstrate our extension and simulate the new protocol in different environments. We show that M-DelPHI performs exceptionally well resulting in above 90% wormhole detection rate against inbound and out-of-band wormholes under the specified test conditions. [ABSTRACT FROM AUTHOR]

Due to their self-organized, multi-hop and distributed characteristics, ad hoc networks are useful in search and rescue. Topology control models need to be designed for energy-efficient, robust and fast communication in ad hoc networks. This paper proposes a topology control model which specializes for search and rescue—Compensation Small World-Repeated Game (CSWRG)—which integrates mobility models, constructing small world networks and a game-theoretic approach to the allocation of resources. Simulation results show that our mobility models can enhance the communication performance of the constructed small-world networks. Our strategy, based on repeated game, can suppress selfish behavior and compensate agents that encounter selfish or faulty neighbors. This model could be useful for the design of ad hoc communication networks. [ABSTRACT FROM AUTHOR]

In Cognitive Radio Ad Hoc Networks (CRAHNS), several spectrum bands with different channel characteristics may be available over a large frequency range. It is essential to identify the most appropriate spectrum band correctly which allow the Secondary Users (SUs) to exploit the band without disturbing the Primary Users (PUs). Many channel selection solutions, based on cooperative spectrum sensing, have been employed for this purpose depending on their prediction models for primary users’ activities. In practice, cooperative spectrum sensing cannot completely solve the sensing problems which are false alarm and miss detection, especially in heavily shadowed or fading environment. This paper presents, ICSSSS, as an Intelligent Channel Selection Scheme for cognitive radio ad hoc network using Self organized map followed by simple Segregation. The contribution of the proposed scheme is twofold: using an unsupervised learnable Self Organizing Map (SOM) method to efficiently minimize the probability of the sensing errors (false alarm and miss detection), in addition to segregated channel selection strategy to speed up the search for the available best channel. Simulation results based on NS2 simulations show that the proposed scheme can be used with the advantage of better performance than other existing channel selection strategies. [ABSTRACT FROM AUTHOR]

In this paper we address the goal of achieving higher throughput capacity in multi-hop wireless ad hoc networks than estimated by capacity scaling laws of Gupta and Kumar (2000) [1]. By exploiting the implications pointed in earlier research, a cross-layer design based channel quality aware rate adaptive MAC algorithm CQRA-MAC is proposed to achieve this goal. CQRA-MAC dynamically switches the MAC transmission rate on the basis of channel quality experienced at the physical layer. The proposed algorithm is implemented by modifying the IEEE 802.11 model of Qualnet 4.5 simulator and its performance is evaluated in static and mobile network scenarios following the random access transport capacity approach. Experimental results show that CQRA-MAC achieves higher throughput than DCF and ARF. The achieved throughput capacity is quantified in terms of measurable network parameters and thus validates equations of random access transport capacity framework (Andrews et al., 2010) [9]. [ABSTRACT FROM AUTHOR]

For the beam search algorithms proposed by some existing literatures cannot always find the global optimal beam in multipath channel and the single communication link may easily be broken, the node at the edge of a wireless ad hoc network will encounter a temporary outage problem, which means it will be isolated from the network. To solve this problem, we propose a new hierarchical beam search algorithm which can be performed on some marginal nodes. The algorithm will take advantage of the multipath channel and find some available communication beams together with the global optimal beam. The main idea of our algorithm is to increase the opportunity to find multiple local optimal beams. The selected number of beams at each level is greater than or equal to the number of paths. In last level, we selectively delete beams and then obtain a plurality of local optimal beams which can be alternative communication beams for the marginal node. Furthermore, we can also get the global optimal beam simultaneously, which are included in these local optimal beams. The simulation results show that, comparing with the exhaustive search algorithm, it has almost the same success rate, but lower search complexity to get a number of alternative beams. Comparing with binary search algorithm, the proposed algorithm has higher success rate to find the global optimal communication beam in multipath environment. [ABSTRACT FROM AUTHOR]

Data caching can remarkably improve the data availability in Mobile Ad Hoc Networks (MANETs) by reducing the access latency and bandwidth usage. Unfortunately, due to mobility and resource constraints, caching techniques designed for wired network are not applicable to MANETs. Moreover, frequent data updates, limited Mobile Terminal's (MT's) resources, insufficient wireless bandwidth and MT's mobility make cache management a tedious task. However, as MTs in MANETs may have similar tasks and share common interests, cooperative caching, which allows the sharing and coordination of cached data among multiple MTs, can be used to reduce the bandwidth and power consumption. Hence, a nearby MT can serve requests instead of the distant data source. The originality of this paper is concentrated on introducing an Adaptive Cooperative Caching Strategy (ACCS) with a novel cache replacement and prefetching policies. ACCS divides the network into non-overlapping clusters. Unlike other caching techniques that employ reactive routing protocols, ACCS employs a novel built-in table driven routing strategy with no additional penalties. Such behavior significantly minimizing the query delay. The secret lies in collecting the routing information during the clusters formulation, then fill the routing tables accordingly. ACCS has been compared against recent cooperative caching strategies. Experimental results have shown that ACCS outperforms other strategies as it introduced the maximum cache hit as well as the minimum query latency. [ABSTRACT FROM AUTHOR]

The increase of mobile devices and most recently wearables has raised the interest to utilize their sensors for various applications such as indoor localization. We present the first acoustic self-localization scheme that is passive, and is capable of operating when sensors are moving, and possibly unsynchronized. As a result, the relative microphone positions are obtained and therefore an ad hoc microphone array has been established. The proposed system takes advantage of the knowledge that a device is worn by its user e.g. attached to his/her clothing. A user here acts as a sound source and the sensor is the user-worn microphone. Such an entity is referred to as a node. Node-related spatial information is obtained from Time Difference of Arrival (TDOA) estimated from audio captured by the nodes. Kalman filtering is used for node tracking and prediction of spatial information during periods of node silence. Finally, the node positions are recovered using multidimensional scaling (MDS). The only information required by the proposed system is observations of sounds produced by the nodes such as speech to localize the moving nodes. The general framework for acoustic self-localization is presented followed by an implementation to demonstrate the concept. Real data collected by off-the-shelf equipment is used to evaluate the positioning accuracy of nodes in contrast to image based method. The presented system achieves an accuracy of approximately 10 cm in an acoustic laboratory. [ABSTRACT FROM AUTHOR]

Without pre-defined infrastructures, vehicles connect to each other to form Vehicular Ad-Hoc Networks (VANETs) to deliver data among vehicles. Dissemination of messages, for example accident alert messages or congestion messages is critical in VANETs. People’s lives may be at stake in accidents. Modeling and predicting VANETs’ message dissemination opens an opportunity to adopt appropriate strategies to alert severe accidents, manage traffic, evacuate vehicles from disasters, or recover from accidents. However, modeling data dissemination is challenging due to vehicles’ high mobility, which results in network topologies rapidly changing and data transmission being unstable. This paper presents analytical data dissemination models on VANETs. We model data dissemination as a new production adoption process and as a time-dependent stochastic process. The fact that information value or importance is decreasing with time and distance is also considered. The analytical models allow prediction and evaluation of information diffusion and enable intelligent traffic management. [ABSTRACT FROM AUTHOR]

In multihop wireless ad hoc networks, it is important to maintain the outcome fairness of throughput and to maximize the throughput. In this paper, we propose a novel opportunistic scheduling framework by considering outcome fairness and throughput simultaneously. Since the data rate fluctuates intensively due to channel errors, we first devise a data rate estimation method with an adaptive sliding window to accurately and adaptively estimate the data rate. Then, we present a framework together with two mechanisms. The first proposed mechanism is ROSA-WOM, with the weighted objective function method to configure the data rate. The other one is ROSA-MGCF, and it is a maximum total goodput method under a constrained fairness index. The proposed mechanisms are able to schedule the flows fairly even when the data rate of all flows is more than the channel capacity. We establish a testbed to evaluate these two mechanisms. The experiment results show that our proposed mechanisms can not only trade off with different fairness and throughput requirements, but also effectively provide robust service isolation, outcome fairness, and high throughput in the presence of channel errors. [ABSTRACT FROM AUTHOR]

Information broadcasting in MANETs is an essential building block for cooperative operations, group discussions, and common announcements (e.g., filling routing tables). The flooding is the simplest broadcasting scheme used in MANETs. In this scheme, source nodes broadcast at once packets to all neighbors. Broadcasting through flooding causes increased messages redundancy, collision, and wastage of bandwidth and energy. Several approaches have been proposed to solve these issues and could be classified into two main categories: static schemes and adaptive schemes. In this paper, we introduce an adaptive scheme for information broadcasting in MANETs. This scheme allows nodes to select an appropriate action, either to rebroadcast or to discard receiving messages. The decision is based on the amount and timestamps of received messages. Simulations have been conducted and results show that the proposed scheme reduces the number of packet transmissions, has better latency and SRB, good reachability, and low energy consumption. [ABSTRACT FROM AUTHOR]

Mission-critical military operations with dismounted soldiers are frequently characterized by high battlefield dynamics. In such scenarios a mobility model can manage soldiers’ movements dynamically especially under enemy attacks. This paper presents a group mobility model simulating realistic soldier and leader battlefield behaviors. Our model analyzes communication between a group of dismounted soldiers deployed in a mobile ad hoc network (MANET) and their leader under several perturbation factors (e.g., noise and enemies attacks) which affect movements and topology connectivity. Results show that the dismounted soldiers’ collective movement improves the capacity of communication channels, whereas noise uncertainty may dramatically destroy the network. Moreover, the enemy’s presence, another disorder parameter, changes qualitatively and quantitatively the army’s wireless communication topology. Enemy numbers decrease almost linearly the throughput at the sink node (commander). A discussion of results follows, using distributions of path lifetimes, path lengths, packet delivery and group sizes in the communication soldiers’ network. [ABSTRACT FROM AUTHOR]

Clustering became relevant in the past as a solution for the scalability problems of ad hoc networking, but, the unsuccessful application of ad hoc solutions to real scenarios, such as the projects SURAN and PRNet, decreased the interest of research community on ad hoc communications, and subsequently, on clustering algorithms. Recently, however, clustering techniques have gained renewed interest due to the emergence of cooperative communications for cellular networking. Clustering is envisaged, in this scenario, as a technique to team up nodes to support efficient data aggregation for energy saving, scalability and privacy among other benefits. Moreover, research on 5G networks also envisages a connected society, where everything and everyone will be connected under the umbrella of Internet of Everything (IoE). This novel communication paradigm has fostered new research on clustering, which has yielded novel and more advanced algorithms and applications. This article surveys the State-of-the-Art in clustering techniques and provides detailed descriptions of the basics of clustering and the latest novel ideas. Open issues, technical challenges and directions for future research are also outlined. [ABSTRACT FROM AUTHOR]

VANETs have emerged as an exciting research and application area. Increasingly vehicles are being equipped with embedded sensors, processing and wireless communication capabilities. This has opened a myriad of possibilities for powerful and potential life-changing applications on safety, efficiency, comfort, public collaboration and participation, while they are on the road. Although, considered as a special case of a Mobile Ad Hoc Network, the high but constrained mobility of vehicles bring new challenges to data communication and application design in VANETs. This is due to their highly dynamic and intermittent connected topology and different application’s QoS requirements. In this work, we survey VANETs focusing on their communication and application challenges. In particular, we discuss the protocol stack of this type of network, and provide a qualitative comparison between most common protocols in the literature. We then present a detailed discussion of different categories of VANET applications. Finally, we discuss open research problems to encourage the design of new VANET solutions. [ABSTRACT FROM AUTHOR]

IEEE 802.11 MAC is designed for single channel and based on Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). The throughput of network is limited by the bandwidth of the single channel and the CSMA-based MAC protocol with omnidirectional antennas can cause the serious unfairness or flow starvation. By exploiting the multiple channels and using the directional antennas, nodes located in each other’s vicinity may communicate simultaneously. This helps to increase the spatial reuse of the wireless channel and thus increase the network performance. In this paper, we propose a Multi-channel MAC protocol with Directional Antennas (MMAC-DA) that adopts IEEE 802.11 Power Saving Mechanism (PSM) and exploits multiple channel resources and directional antennas. Nodes have to exchange control packets during the Announcement Traffic Indication Message (ATIM) window to select data channels and determine the beam directions which are used to exchange data packets during the data window. The simulation results show that MMAC-DA can improve the network performance in terms of aggregate throughput, packet delivery ratio, energy efficiency and fairness index. [ABSTRACT FROM AUTHOR]

This study investigates the impact of the diversity combining techniques on the performance of wireless code division multiple access (CDMA) ad hoc networks operating over κ -μ fading channels, where the performance criterion in this study is in terms of the expected progress per hop. The probability density function (PDF) and the cumulative density function (CDF) of the interference power are obtained in κ -μ fading conditions. Furthermore, expression for the unconditional CDF of the signal-to-noise-and-interference ratio (SNIR) is derived, which is utilized to derive expressions for the expected progress per hop with selecting combining (SC) and maximal ratio combining (MRC) diversity. Corresponding expressions for Nakagami- m and Rician fading are presented in this paper as special cases of κ -μ fading. Numerical results are presented for illustration purposes. [ABSTRACT FROM AUTHOR]

In this paper, we consider decoding of loss tolerant data encoded by network coding and transmitted over error-prone networks. Intermediate network nodes typically perform the random linear network coding in a Galois field and a Gaussian elimination is used for decoding process in the terminal nodes. In such settings, conventional decoding approaches can unfortunately not reconstruct any encoded data unless they receive at least as many coded packets as the original number of packets. In this paper, we rather propose to exploit the incomplete data at a receiver without major modifications to the conventional decoding architecture. We study the problem of approximate decoding for inter-dependent sources where the difference between source vectors is characterized by a unimodal distribution. We propose a mode-based algorithm for approximate decoding, where the mode of the source data distribution is used to reconstruct source data. We further improve the mode-based approximate decoding algorithm by using additional short information that is referred to as position similarity information (PSI). We analytically study the impact of PSI size on the approximate decoding performance and show that the optimal size of PSI can be determined based on performance requirements of applications. The proposed approach has been tested in an illustrative example of data collection in sensor networks. The simulation results confirm the benefits of approximate decoding for inter-dependent sources and further show that 93.3% of decoding errors are eliminated when the approximate decoding uses appropriate PSI. [ABSTRACT FROM AUTHOR]

We study decidability and undecidability results for parameterized verification of a formal model of timed Ad Hoc network protocols. The communication topology is defined by an undirected graph and the behaviour of each node is defined by a timed automaton communicating with its neighbours via broadcast messages. We consider parameterized verification problems formulated in terms of reachability. In particular we are interested in searching for an initial configuration from which an individual node can reach an error state. We study the problem for dense and discrete time and compare the results with those obtained for (fully connected) networks of timed automata. [ABSTRACT FROM AUTHOR]

The study of polling disciplines for receiver-initiated MAC protocols has not received much attention in the literature, and simple schemes such as round-robin or uniform prioritization are usually assumed. However, not only the order, but also the rate at which nodes are polled is significant: a polling rate that is too slow may render low throughput and high delays, whereas the opposite may lead to excessive control traffic and frame collisions. Ideally, a receiver-initiated MAC protocol would perform best if nodes could know “whom” and “when” to poll based on data availability. This paper investigates the performance of three polling disciplines when applied to a specific receiver-initiated unicast MAC protocol that is based on a reversal of the binary exponential backoff (BEB) algorithm of the IEEE 802.11. With the BEB algorithm, the polling rate is self-regulated according to channel conditions and traffic availability at polled nodes. Additionally, this paper extends the BEB-based MAC protocol by introducing a new control frame and a frame reordering technique at MAC queues to speed up polling rounds. The performance of the polling disciplines are also compared to the traditional IEEE 802.11 with respect to control overhead, delay, fairness, and throughput, according to different topologies and traffic scenarios. [ABSTRACT FROM AUTHOR]

Range extension is a promising feature offered by cooperative transmission (CT), also known as virtual multiple-input–single-output (VMISO). Many authors have considered how the diversity and array gains from CT may benefit a wireless multi-hop network, when the gains are used for increasing link reliability and reducing transmit power. However, relatively less attention has been given to the benefits of CT range extension and few testbed implementations of CT have been demonstrated. In this paper, we focus on how CT range extension can impact the lower three layers, especially medium access control (MAC) and routing for ad hoc and sensor multi-hop networks (AHSMNs). We assume cooperators decode and forward the packets. Various analytical models, performance analyses, and experimental results using software-defined radios in an indoor office environment are discussed. For wireless sensor networks (WSNs), we review CT range extension at the network layer, to eliminate the energy hole that forms around sink nodes in non-CT networks, and we review cooperator selection and duty cycle scheduling algorithms at Layer 2, to maximize the lifetime of a multi-hop WSN. For ad hoc networks, we emphasize a family of lightweight broadcasting and unicasting protocols based on a simple form of CT called the opportunistic large array (OLA). Experimental results, including OLA-based unicast routing and diversity order effects in two-hop CT networks, are discussed. [ABSTRACT FROM AUTHOR]

The knowledge of vehicle headway distribution is essential for estimating the probability of connectivity in vehicle ad hoc networks. We consider the distribution of vehicles in a single lane, taking into account that consecutive vehicles have to maintain a minimum safe distance between them. It is shown that the account of safe distance improves the agreement between vehicles theoretical spacing distribution and empirical data in single lane traffic. We study how this minimum distance affects the connectivity probability in light traffic conditions. We show that the headway distribution of single lane traffic in the free flow conditions is better modeled using a shifted exponential model which takes into account the safe distance between vehicles. We also show that neglecting this effect will result in overestimating the connectivity in vehicular ad hoc networks, therefore, underestimating the communication range needed to establish the network with a given connectivity probability. The effect is stronger for shorter transmission range. [ABSTRACT FROM AUTHOR]

A Monte Carlo Simulation based evaluation of mobile ad hoc network reliability is proposed which considers different mobility models along with the effect of different scenario metrics and different values of tuning parameter. Through our approach we show that the mobility considerations have no significant impact on reliability as the same results are obtained by just implicitly simulating the node locations. Considering no mobility models reduces computational burden, number of random variables involved making the algorithm more efficient is the added advantage. A comparative study of the results of the network reliability estimate considering with and without mobility is provided. [ABSTRACT FROM AUTHOR]

An accurate reproduction of real human movement is essential in simulations of MANETs in order to obtain meaningful performance results. Existing models capturing real world mobility features often require knowledge of the underlying dynamics of the target scenario, therefore limiting the application scope. In this paper we tackle this problem from a different perspective. Rather than considering the details of the target scenario, we extract features from a sample trace, and synthesize traces that have similar features. In particular, as human activities are often socially organized, resulting in a tendency of forming groups, we propose an N-body mobility model that captures the group forming tendency from traces of a small number of nodes, and reproduces them in mobility traces of a larger population. Through simulation we show that the N-body model is capable of synthesizing the group forming behavior similar to that observed from sample traces. [ABSTRACT FROM AUTHOR]

In order to establish communication links among different communication devices or machines, the Medium Access Control (MAC) has to schedule the simultaneous transmissions by the contending nodes to constrain the probability of outage at each receiver. An efficient channel access scheme should be able to schedule the highest number of concurrent transmissions while being easy to implement with minimal coordination between the contending nodes. The existing MAC schemes provide network-wide solutions without adaptiveness, such as in existing guard zone-based solutions. On the other hand, an adaptive channel access scheme is proposed in this paper, which instead of declaring a network-wide fixed guard zone employs each interferer's Transmitter–Receiver (Tx–Rx) separation to conclude its incorporation in the scheduled transmissions. The suggested scheme warrants the spatial separation among the scheduled links by suppressing the dominant interferers. The proposed MAC design functions approximately as good as the centralized, otherwise infeasible, joint scheduling and power control algorithm. In addition, the recommended scheme has proved its strength by outperforming both Carrier Sense Multiple Access (CSMA) and fix-sized guard zone schemes by significant margins under strict outage constraints and high contention density. The proposed scheme provided up to 100% and 60% better transmission capacity when compared with CSMA and fix-sized guard zone-based scheme, respectively. This paper also presents the closed-form results for the optimal guard zone size multiplier and the corresponding throughput capacity in terms of various network variables, such as contention density, outage constraint, Tx–Rx separation, network's path loss exponent and spreading factor. [ABSTRACT FROM AUTHOR]

The Future Internet of Things (IoT) will connect billions of battery-powered radio-enabled devices. Some of them may need to communicate with each other and with Internet gateways (border routers) over multi-hop links. While most IoT scenarios assume that for this purpose devices use energy-efficient IEEE 802.15.4 radios, there are use cases where IEEE 802.11 is preferred despite its potentially higher energy consumption. We extend the IEEE 802.11 power saving mode (PSM), which allows WLAN devices to enter a low-power doze state to save energy, with a traffic announcement scheme that facilitates multi-hop communication. The scheme propagates traffic announcements along multi-hop paths to ensure that all intermediate nodes remain awake to receive and forward the pending data frames with minimum latency. Our simulation results show that the proposed Multi-Hop PSM (MH-PSM) improves both end-to-end delay and doze time compared to the standard PSM; therefore, it may optimize WLAN to meet the networking requirements of IoT devices. MH-PSM is practical and software-implementable since it does not require changes to the parts of the IEEE 802.11 medium access control that are typically implemented on-chip. We implemented MH-PSM as a part of a WLAN driver for Contiki OS, which is an operating system for resource-constrained IoT devices, and we demonstrated its efficiency experimentally. [ABSTRACT FROM AUTHOR]

Ad-hoc networks represent distributed systems that comprise wireless nodes which can dynamically self-organize into arbitrary and temporary network topologies, without relying on pre-existing infrastructure, and thus network hierarchy formation via clustering is vital for them. The present article conducts a comprehensive simulation-based evaluation of the performance achieved by a recently proposed, biology-inspired, clustering algorithm used in wireless ad hoc networks, namely the Randomized Beep Based Maximum Independent Set ( RanMIS ) (Afek et al., 2011). This is the first evaluation done for this high-performance algorithm. The evaluation is done for a set of metrics (measures for protocol cost, backbone description and robustness) some of which has not been used in earlier simulation studies and are developed here. Our study confirms the virtues (message complexity) and reveals the shortcomings of RanMIS (latency issues), and quantifies the impact of some of its administratively-tuned parameters. RanMIS is compared with two representative graph-theoretic node clustering methods and a new one developed here; the results confirm the message optimality of RanMIS , but reveal some shortcomings of it, basically related to the excessive number of rounds that needs to run in order to complete the network clustering. [ABSTRACT FROM AUTHOR]

Highlights: [•] The feasibility of medical alarms propagation via wireless linking of mobile phones is proposed. [•] Analyses were based on realistic people mobility in an urban environment. [•] Results revealed the practicability of the solution in assuring timely alarm dissemination. [•] The dissemination scheme has the potential to be routinely utilized in all people aggregations. [ABSTRACT FROM AUTHOR]

Abstract: We consider the problem of appropriate clusterhead selection in wireless ad-hoc networks where it is necessary to provide robustness in the face of topological changes caused by node motion, node failure and node insertion or removal. The main contribution of our work is a new strategy for clustering a wireless AD HOC network and improvements in WCA and other similar algorithms. We first derived some analytical models and thereafter some clustering schemes. Our contribution also extends previous works in providing some properties and analyses of Quality of Clustering (QoC) in AD HOC. We showed that our algorithm outperforms the Weighted Clustering Algorithm (WCA) in terms of cluster formation and stability. One of the main ideas of our approach is to prioritize favourable nodes in clusterhead election and re-election processes. We strived to provide a trade-off between the uniformity of the load handled by the clusterheads and the connectivity of the network. [Copyright &y& Elsevier]

Abstract: A new strategy for clustering a wireless AD HOC network is proposed. The main contribution of our work is to improve Weighted Clustering Algorithm (WCA) [5] and other similar algorithms. In literature, the node degree is considered as an important weight metric in clusterhead selection process. Unfortunately, this metric is not consistent especially when it is considered separately at the node environment such as the neighbours’ location within the transmission range zone of this node. To overcome this inefficiency, we propose two new models. Thereafter, we combined these two models to take profit of their efficiencies. The new combined model, motivates us to generate and reformulate many node degree based formula given in literature and dealing with Quality of Clustering (QoS) as stability and load balancing clustering parameters. We showed that our algorithm outperforms WCA in the in terms of cluster formation and stability. [Copyright &y& Elsevier]

Highlights: [•] We study three types of Ad Hoc routing protocols, AODV, DSDV and CBRP. [•] A real urban area and a mobility model are established for the simulation. [•] The NS2 simulation tool is used. [•] We determine a methodology for the comparative analysis in the scenarios proposed. [•] For emergency and rescue scenarios, the protocol with better performance is the CBRP. [ABSTRACT FROM AUTHOR]

Abstract: The need for an effective clustering algorithm for Vehicular Ad Hoc Networks (VANETs) is motivated by the recent research in cluster-based MAC and routing schemes. VANETs are highly dynamic and have harsh channel conditions, thus a suitable clustering algorithm must be robust to channel error and must consider node mobility during cluster formation. This work presents a novel, mobility-based clustering scheme for Vehicular Ad hoc Networks, which forms clusters using the Affinity Propagation algorithm in a distributed manner. This proposed algorithm considers node mobility during cluster formation and produces clusters with high stability. Cluster performance was measured in terms of average clusterhead duration, average cluster member duration, average rate of clusterhead change, and average number of clusters. The proposed algorithm is also robust to channel error and exhibits reasonable overhead. Simulation results confirm the superior performance, when compared to other mobility-based clustering techniques. [Copyright &y& Elsevier]

Abstract: Clustering is a widely used solution to provide routing scalability in wireless ad hoc networks. In the literature, clustering schemes feature different characteristics and purposes, however few schemes are context-aware. This work proposes a new solution called Distributed and Location-aware Clustering (DiLoC), a clustering scheme designed to operate in indoor environments, providing mechanisms to gather context location information in order to ease the maintenance of clusters, thus resulting in a stabler network topology in order to provide a scalable network topology for an efficient routing. DiLoC considers three distinct approaches, regarding the characteristics of the deployment environment, aiming to cover infrastructure-less, infrastructure and hybrid network scenarios. DiLoC was evaluated and compared with a similar clustering scheme, featuring the stability, amount of clustered nodes and network load. Included results demonstrate a scalable algorithm with a significant high stability. [Copyright &y& Elsevier]

Abstract: In this paper we address the problem of finding the optimal performance region of a wireless ad hoc network when multiple performance metrics are considered. Our contribution is to propose a novel cross-layer framework for deriving the Pareto optimal performance bounds for the network. These Pareto bounds provide key information for understanding the network behavior and the performance trade-offs when multiple criteria are relevant. Our approach is to take a holistic view of the network that captures the cross-interactions among interference management techniques implemented at various layers of the protocol stack (e.g. routing and resource allocation) and determines the objective functions for the multiple criteria to be optimized. The resulting complex multiobjective optimization problem is then solved by multiobjective search techniques. The Pareto optimal sets for an example sensor network are presented and analyzed when delay, reliability and energy objectives are considered. [Copyright &y& Elsevier]

Abstract: MMRS was developed as a system that eliminates parents’ anxiety by watching over their children and sharing information about their safety. Through MMRS, parents and school staff can confirm the location of children through GPS and at the same time view a visualization of their mental state, which cannot be seen by the naked eye. Also, in areas cell phone signals cannot reach, one special feature of the system is that it is equipped to use ad hoc and multihop networks. [Copyright &y& Elsevier]

Abstract: Selecting the most appropriate path between each pair of nodes in an ad hoc network is an issue with major impact on network performance. Many schemes were proposed and compared in the literature, using various criteria. However, the connectivity over time behavior of these schemes, which is important to some practical applications, was not well studied, especially with regards to the terrain type. In this work we use simulation to study this aspect of network performance. We demonstrate that a different connectivity requirement and a different time horizon may dictate a different scheme to use. We also demonstrate that path selection schemes are not equally sensitive to the terrain. [Copyright &y& Elsevier]

Abstract: Mobile ad hoc networks are able to extend the coverage area of Internet access points by establishing multihop communication paths. Due to diverse factors such as the mobility of the nodes, the propagation conditions or the traffic status, the communication paths present a lifetime. In fact, the quality of the Internet connection mainly depends on the durability of the employed communication routes. In order to improve the network performance, the nodes should select the best route in terms of its remaining lifetime. Since the factors impacting the route lifetime are unpredictable, the route remaining lifetime cannot be analytically derived. Under these circumstances, a fuzzy-logic system outstands as a potential solution to estimate the stability of the routes. This paper analyses the potentiality of this kind of solution. In particular, the paper presents a fuzzy logic system which should be installed in the mobile nodes to distributedly identify the stable routes. In particular, the system is supported by an interval-based type-2 fuzzy logic. Being a type-2 fuzzy logic system, it is able to cope with inexact estimations. This ability is necessary to avoid the use of additional messages which will occupy the scarce wireless medium. On the other hand, an interval-based fuzzy system provides the simplicity demanded by the energy-constrained mobile devices. As a novelty, the two outputs of the interval-based fuzzy system are employed. The use of each output depends on the traffic state of the mobile node. By means of extensive simulations, we demonstrate the goodness of the proposed system. [Copyright &y& Elsevier]

Abstract: Medium access control (MAC) protocol is essential since it is to address how to resolve potential contentions and collisions among wireless nodes and give them equal share of channel bandwidth. However, due to the existence of hidden/exposed terminal problem and partially connected network topology, IEEE 802.11 standard, the de facto and widely accepted wireless MAC protocol, does not function well in mobile ad hoc networks (MANETs) because it brings intensive collisions, unfair channel access, and quickly degraded system throughput in multi-hop environments, especially when the whole system is also dense and congested. One approach to alleviate this problem is to use multi-channel MAC protocol because these nodes can access the wireless channel simultaneously as long as they choose the different channels to transmit their packets. Nowadays, the modern wireless MAC protocols usually support multiple channels, where mobile nodes adapt their channels based on their channel selection strategies to transmit their own packets. In this paper, we put forth an adaptive channel allocation strategy for IEEE 802.11 based multi-channel MAC protocol in MANETs. An analytic model is also carried out to study the normalized saturation throughput of proposed scheme. In addition to theoretical analysis, simulations are conducted to evaluate the performance of the proposed scheme in congested multi-hop environments, and the results indicate that our adaptive channel allocation strategy did achieve far better performance than the legacy single channel IEEE 802.11 protocol without loss of simplicity. [Copyright &y& Elsevier]

Abstract: We study the problem of constructing a novel framework for dynamically organizing mobile nodes in wireless ad-hoc networks into clusters where it is necessary to provide robustness in the face of topological changes caused by node motion, node failure and node insertion/removal. The main contribution of our work is a new strategy for clustering a wireless AD HOC network and improvements in WCA (Weighted Clustering Algorithm) [3], a well-known algorithm. We first derive mathematically a new cluster size bound to replace δ in WCA and a simple node stability model. Thereafter, we prove their efficiencies. Our contribution also extends previous work to replace the degree- difference used initially in WCA to provide load-balance in wireless AD HOC with a new more efficient and consistent model which helps to decrease the number of clusters. We show that our algorithm outperforms WCA in terms of cluster formation and stability. The non-periodic procedure for clusterhead election is invoked on-demand, and is aimed to reduce the computation and communication costs. We strive to provide a trade-off between the uniformity of the load handled by the clusterheads and the connectivity of the network. [Copyright &y& Elsevier]

Abstract: Mobile wireless ad hoc networks need to maximize their network lifetime (defined as the time until the first node runs out of energy). In the broadcast network lifetime problem, all nodes are sending broadcast traffic, and one asks for an assignment of transmit powers to nodes, and for sets of relay nodes so that the network lifetime is maximized. The selection of a dynamic relay set consisting of a single node (the ‘master’), can be regarded as a special case, providing lower bounds to the optimal lifetime in the general setting. This paper provides a preliminary analysis of such a ‘dynamic master selection’ algorithm, comparing relaying to direct routing. [Copyright &y& Elsevier]

Abstract: The spatial resolution of publicly available numerical weather forecasts is largely limited by the computing resources of the originating weather services. Only selected parameters are available to the public from many weather services. We present a scalable system for distributed computation of high resolution symbiotic numerical weather forecasts. Each forecast is computed on the user's desktop computer, independent of other forecasts. Forecasts from the neighborhood may be exchanged between forecast producing peers, and amalgamated into a Symbiotic Forecast. The combination of several fore- casts yields additional insight into the uncertainty introduced by the interaction of the chosen grid placement of the numerical model with geographical features with steep gradients, such as steep terrain. We let forecast producers share forecasts with each other. We assume that a user frequently is interested in the forecast for the area where the user lives and that the produced forecasts are stored at a computer located where the user is. Based on this, we limit the sharing of forecasts to computers within the same geographical area. To find computers with relevant forecasts, we will find most of them at computers located within a limited geographical region. These computers can be located quickly by scanning for them every time forecasts are needed. This approach scales with respect to the number of forecasters by limiting interaction to geographical regions. It also removes the need to maintain a list of computers with relevant forecasts. [Copyright &y& Elsevier]

Abstract: In this paper we study the fundamental scheduling, multiplexing and diversity trade-off in MIMO ad hoc networks. In particular, we propose a unified framework for the scheduling-multiplexing and scheduling-diversity sub-problems that constitutes a major step towards solving the overall problem. The two sub-problems are motivated by a fundamental trade-off between scheduling full multiplexing (diversity) gain non-interfering links and scheduling interfering links using lower multiplexing (diversity) gain in conjunction with interference nulling. First, we cast each sub-problem as a cross-layer optimization problem that jointly decides the scheduling and MIMO stream allocation, subject to signal-to-interference-and-noise-ratio (SINR) constraints. Second, we characterize the problem as non-convex integer programming which is quite challenging to solve. Hence, we shift our focus to characterize the optimal for the simple case of two links. The main result of this paper is that the two fundamentally different sub-problems give rise to structurally similar SINR-based decision rules which constitute the basis for a resource allocation algorithm with linear complexity in the number of links, namely Iterative MIMO Link Scheduling (IMLS), that solves the two sub-problems and achieves significant gains for any number of links. Numerical results exhibit more than twofold/quadratic improvement over scheduling non-interfering links with full multiplexing/diversity gain, for plausible scenarios. IMLS and its variants reveal an important throughput-fairness trade-off which is an interesting topic for future research. [Copyright &y& Elsevier]

Abstract: Mobile ad hoc networks (MANET) have a set of unique challenges, particularly due to mobility of nodes, that need to be addressed to realize their full potentials. Because the mobile nodes of a MANET are free to move rapidly and arbitrarily, the network topology may change unexpectedly. This paper presents a decentralized approach to maintain the connectivity of a MANET using autonomous, intelligent agents. Autonomous agents are special mobile nodes in a MANET, but unlike other nodes, their function is to proactively prevent network bottlenecks and service problems by intelligently augmenting the network topology. To achieve this function without depending on a central network management system, autonomous agents are expected to dynamically relocate themselves as the topology of the network changes during the mission time. A flocking-based heuristic algorithm is proposed to determine agent locations. A computational study is performed to investigate the effect of basic flocking behaviors on the connectivity of a MANET. [Copyright &y& Elsevier]

Abstract: This paper considers a framework where data from correlated sources are transmitted with the help of network coding in ad hoc network topologies. The correlated data are encoded independently at sensors and network coding is employed in the intermediate nodes in order to improve the data delivery performance. In such settings, we focus on the problem of reconstructing the sources at decoder when perfect decoding is not possible due to losses or bandwidth variations. We show that the source data similarity can be used at decoder to permit decoding based on a novel and simple approximate decoding scheme. We analyze the influence of the network coding parameters and in particular the size of finite coding fields on the decoding performance. We further determine the optimal field size that maximizes the expected decoding performance as a trade-off between information loss incurred by limiting the resolution of the source data and the error probability in the reconstructed data. Moreover, we show that the performance of the approximate decoding improves when the accuracy of the source model increases even with simple approximate decoding techniques. We provide illustrative examples showing how the proposed algorithm can be deployed in sensor networks and distributed imaging applications. [Copyright &y& Elsevier]

Abstract: This paper studies a density driven virtual topography based publish/subscribe service for mobile ad hoc networks. Two variants of the service are presented and evaluated by extensive simulations; the first is very communication frugal while the latter trades a higher message overhead for faster latency. Both variants are also being compared to two other representative approaches for publish/subscribe in ad hoc networks, a dissemination tree based scheme and an efficient flooding based scheme. It is shown that the density-driven approach outperforms the others in most tested scenarios. [Copyright &y& Elsevier]