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Ultraviolet technology has a wide range of applications in military and civilian fields, such as space detection, ultraviolet light guidance, ultraviolet interference, corona discharge detection and military communications. Starting from the single and multiple scattering of ultraviolet light, this paper first introduces the progress of ultraviolet optical communication at home and abroad. Then it analyzes the different links in ultraviolet optical communication. Next, it discusses the pulse broadening effect and atmospheric turbulence of ultraviolet communication in non-direct link ultraviolet communication. Finally, the paper summarizes the ultraviolet Ad Hoc network, and shows the trend of the development of ultraviolet optical communication.

Abstract Delay tolerant networks (DTNs) is a network evolved from mobile networks. Differing from the traditional network, which has a stable end‐to‐end transmission path, DTNs are sparse and intermittently connected mobile ad hoc network, which are widely used in harsh environments, such as battlefields, seabed, space communication networks, and so on. In DTNs, intermittent connectivity, partitioned network, long delays and node mobility characteristics make the network fail to communicate frequently, therefore, how to successfully forward the message is of extreme importance. Up to now, almost all the traditional models in DTNs use the store‐carry‐forward method. This paper proposes a novel clustered DTN routing model based on sensing node relationship strength. The routing mechanism takes advantage of the number of other nodes encountered by the nodes in the process of movement and the changes in the number of nodes to calculate the strength of the relationship between nodes, and clusters DTN routing according to the strength of the relationship between nodes. Moreover, the relationship between nodes in a cluster and other clusters is used to transmit messages between clusters, and messages are transmitted within clusters according to the strength of the relationship between nodes. Simulation results show that the routing mechanism not only increases the success rate of message transmission, but also reduces the transmission delay of messages and improves network performance.

Abstract In unmanned aerial vehicle ad‐hoc network (UANET), the node speed of unmanned aerial vehicles (UAVs) may reach up to 400 km/h. The fast or slow movement of UAV nodes leads to different speeds of topology change of the nodes. Traditional optimized link state routing (OLSR) protocol cannot adaptively adjust the routing update period when the network topology changes, which may lead to the nodes calculating incorrect routing tables. This increases the average end‐to‐end delay and packet loss rate for packet transmission. To enhance the adaptability of OLSR routing protocol to network topology changes, this paper proposes a multi‐agent independent deep deterministic policy gradient‐OLSR (MA‐IDDPG‐OLSR) routing protocol based on distributed multi‐agent reinforcement learning. The protocol deploys DDPG algorithm on each UAV node, and each UAV node adaptively adjusts the Hello and TC message sending intervals, according to the one‐hop neighbouring nodes as well as its own state. Simulation results show that the proposed protocol is able to improve the throughput and reduce the packet loss rate as compared to traditional AODV, GRP, OLSR, and distributed multiple‐agent independent proximal policy optimization‐OLSR (MA‐IPPO‐OLSR), distributed multiple‐agent independent twin delayed deep deterministic policy gradient‐OLSR (MA‐ITD3‐OLSR) routing protocols. Since MA‐IDDPG‐OLSR relies only on local information, there is a minor performance degradation in MA‐IDDPG‐OLSR compared to centralized single‐agent DQN‐OLSR routing protocol. But it is more suitable to a completely distributed UAV network without a centralized node.

This paper proposes an evolved wireless ad hoc network (WANET) in which user equipment (UE) can manage radio resources by itself without the control by infrastructure. There are two independent channels in the proposed WANET, one is a data channel, the other is a tone channel for resource management. UEs allocate, occupy, and return resources by using tones in the tone channel. Although UEs do not exchange channel information with each other, they are able to occupy a clear one-hop area without a hidden node problem by setting the data communication area and the tone communication area differently. A UE occupying a resource performs a real time collision check on the occupied resource, and if a collision is detected, it is able to re-occupy a resource without collision. In this paper, we present the operating principle of the proposed WANET, and design its communication area, and analyze the average resource occupation time. Since the proposed WANET operates in a general communication environment that is not limited to special assumptions, it supports periodic and aperiodic communication and broadcast links and unicast links without hidden node problem, and could be utilized to various communication fields such as drones, vehicles, ships, and smartphones.

This paper presents a comprehensive study of capacity characterization in mobile wireless networks employing directive communications and full-duplex communication technology. We address the impact of nodes’ mobility, directive beams, and full-duplex capabilities on the network capacity. Firstly, we derive the signal-to-interference-plus-noise ratio (SINR) for a reference receiver, considering the combined effects of mobility, directive beams, and full-duplex communications. The derived SINR is then utilized to calculate the network’s capacity. To validate the proposed model, extensive simulations are performed, incorporating various scenarios of mobility levels, self-interference suppression levels in the full-duplex wireless system, and different receiving thresholds. The simulation results confirm the accuracy and effectiveness of the derived SINR-based capacity characterization model under real-world conditions. Furthermore, we study the probability of a receiver simultaneously decoding multiple packets as a function of the receiver’s threshold and full-duplex self-interference suppression. The probability is crucial for assessing the network performance and facilitating future optimization schemes aimed at regulating the number of competing nodes in a given spatial region. The validated model and probability characterization offer valuable insights into network performance evaluation and can be instrumental in devising future efficient optimization strategies for managing network contention at the medium access control and enhancing the network performance.

Reconfigurable wireless networks, such as ad hoc or wireless sensor networks, do not rely on fixed infrastructure. Nodes must cooperate in the multi-hop routing process. This dynamic and open nature make reconfigurable networks vulnerable to routing attacks that could degrade significantly network performance. Intrusion detection systems consist of a set of techniques designed to identify hostile behavior. In this paper, there are several approaches for intrusion detection in reconfigurable network routing such as collaborative, statistical, or machine learning-based techniques. In this paper, we introduce a new approach to intrusion detection for reconfigurable network routing based on linear systems theory. Using this approach, we can discriminate routing attacks by considering the system's z-plane poles. The z-plane can be thought of as a two dimensional feature space that arises naturally. It is independent of the number of network attack detection metrics and does not require extra dimensionality reduction. Two different host-based intrusion detection techniques, inspired by this new linear systems perspective, are presented and analyzed through a case study. The case study considers the effects of attack severity and node mobility to the attack detection performance. High attack detection accuracy was obtained without increasing packet overhead for both techniques by analyzing locally available information.

Purpose - This paper aims to introduce vehicular network platform, routing and broadcasting methods and vehicular positioning enhancement technology, which are three aspects of the applications of intelligent computing in vehicular networks. From this paper, the role of intelligent algorithm in the field of transportation and the vehicular networks can be understood. Design/methodology/approach - In this paper, the authors introduce three different methods in three layers of vehicle networking, which are data cleaning based on machine learning, routing algorithm based on epidemic model and cooperative localization algorithm based on the connect vehicles. Findings - In Section 2, a novel classification-based framework is proposed to efficiently assess the data quality and screen out the abnormal vehicles in database. In Section 3, the authors can find when traffic conditions varied from free flow to congestion, the number of message copies increased dramatically and the reachability also improved. The error of vehicle positioning is reduced by 35.39% based on the CV-IMM-EKF in Section 4. Finally, it can be concluded that the intelligent computing in the vehicle network system is effective, and it will improve the development of the car networking system. Originality/value - This paper reviews the research of intelligent algorithms in three related areas of vehicle networking. In the field of vehicle networking, these research results are conducive to promoting data processing and algorithm optimization, and it may lay the foundation for the new methods.

This paper deals with the tradeoffs between security, real-time and lifetime performance. Due to the multihop nature of communication wireless ad hoc networks are very vulnerable to attacks. Malicious nodes included in a routing path may misbehave and organize attacks such as black holes. Scaling the number of hops for a packet delivery we trade off energy efficiency against security and real-time communication. To study the multihop communication we propose a hierarchical communication model. The REWARD (receive, watch, redirect) algorithm for secure routing is employed as a main example for corrective actions. Symmetrical routing is a distinguish feature of protocols such as REWARD and we outline the threshold of conflict between power-efficient partitioning of communication links and symmetrical routing.

Vehicular ad hoc networks consist of self-organizing nodes using multi-hop wireless links for communication without any infrastructure support. Traditionally, ad hoc routing protocols use the minimum hop count for their routing metric since a smaller number of transmissions is typically equivalent to a higher throughput, lower delay, and minimal power consumption. However, with the muti-rate capability of emerging radio interfaces, e.g., 802.11ax/be standards, the min-hop metric no longer results in high throughput. For instance, if the higher data rate links are selected for the route, it could result in a higher throughput even if the route takes more hop counts. In this paper, we propose a high throughput routing scheme, called MARV, which makes two key contributions. MARV searches for high throughput paths using an on-demand route searching algorithm so that the routing overhead is smaller compared to other multi-rate-aware routing schemes. MARV also searches for multiple paths to maintain both min-hop and high-throughput paths to select the adequate path depending on the data packet size. We conduct simulations to demonstrate that MARV outperforms not only min-hop path metrics but also previously proposed high-throughput metrics.

The increasing demand for Internet of Things (IoT) applications has resulted in vast amounts of data, requiring the utilization of big data analytics. The integration of big data analytics in IoT-based smart cities can greatly benefit from the development of wireless communication protocols, among which the Thread protocol has emerged as a promising option. Thread is IEEE 802.15.4 based and has advanced capabilities like mesh networking, IPv6 support, and multiple gateways providing no single point of failure. This paper presents the design and evaluation of a low-cost mesh network using Raspberry Pi, nRF52840 dongle, and OpenThread 1.2 (i.e., an open-source software implementation of the Thread protocol stack). The research elaborates on the hardware and software solutions used, as well as the network topologies adopted. To evaluate the performance of the developed system, extensive real-time tests are performed, considering parameters, such as jitter, packet loss, and round trip time. These tests effectively demonstrate the effectiveness of the Thread network. Furthermore, the impact of varying payload size and bitrate on the network is analyzed to understand its influence. The behavior of the multi-hop network is also examined under link failure scenarios, providing insights into the network’s robustness. Our findings provide valuable insights for researchers interested in designing low-cost and efficient mesh networks for various IoT applications, including home automation, building/campus monitoring systems, distributed industrial IoT applications, and smart city infrastructure.

In recent years, low-power wide-area network (LPWAN) has received widespread popularity with long-range and wide-area communication at low power for the Internet of Things (IoT) systems. Among many vendors of LPWAN, long-range low-power wireless communications, also called LoRa, is one of the competing standards and is well known in both academia and industrial communities as an emerging research area. Among the LoRa applications, unmanned aerial vehicles (UAV) systems are emerging with the benefits of extended battery life and a long communication range. In this paper, we investigate the network capacity with the mixture of concurrent and sequential transmission (MCST) scheme over LoRa networks. From the simulation results, it can be seen that MCST is suitable for implementation in the LoRa network. Specifically, MCST can achieve higher throughput with low transmission latency and energy consumption compared to the existing CSMA approach LoRa MAC. Besides, we also propose a modified MCST over the LoRa (mMCST/LoRa) scheme to mitigate the transmission latency further. The simulation results reveal a better performance in terms of throughput, latency and energy consumption, regardless of the frame payload size and the number of nodes in the network.

A novel on-demand cluster-based hybrid routing protocol for cognitive radio ad hoc network with non-uniform node distribution is proposed in this paper. At first, a novel spectrum-aware clustering mechanism is introduced. The proposed clustering mechanism divides node into clusters based on three values: spectrum availability, power level of node, and node stability. Therefore, clusters are formed with the highest stability to avoid frequent reclustering. Later, a routing algorithm is introduced to minimize the delay while achieving acceptable delivery ratio. In this paper, routing is defined as a multi-objective optimization problem to combine different individual routing metrics to form a global metric. Simulation results show that our proposed routing algorithm can guarantee a lower delay and a higher packet delivery ratio than conventional routing protocols for cognitive radio ad hoc networks. Due to our routing design specification, such as power consideration and low delay, it can be suitable to be adopted for Internet of Things applications.

With the emergence of new technologies and standards for wireless communications and an increase in application and user requirements, the number and density of deployed wireless ad hoc networks is increasing. For deterministic ad hoc networks, Time-Division Multiple Access (TDMA) is a popular medium access scheme, with many distributed TDMA scheduling algorithms being proposed. However, with increasing traffic demands and the number of wireless devices, proposed protocols are facing scalability issues. Besides, these protocols are achieving suboptimal spatial spectrum reuse as a result of the unsolved exposed node problem. Due to a shortage of available spectrum, a shift from fixed spectrum allocation to more dynamic spectrum sharing is anticipated. For dynamic spectrum sharing, improved distributed scheduling protocols are needed to increase spectral efficiency and support the coexistence of multiple co-located networks. Hence, in this paper, we propose a dynamic distributed multi-channel TDMA (DDMC-TDMA) slot management protocol based on control messages exchanged between one-hop network neighbors and execution of slot allocation and removal procedures between sender and receiver nodes. DDMC-TDMA is a topology-agnostic slot management protocol suitable for large-scale and high-density ad hoc networks. The performance of DDMC-TDMA has been evaluated for various topologies and scenarios in the ns-3 simulator. Simulation results indicate that DDMC-TDMA offers near-optimal spectrum utilization by solving both hidden and exposed node problems. Moreover, it proves to be a highly scalable protocol, showing no performance degradation for large-scale and high-density networks and achieving coexistence with unknown wireless networks operating in the same wireless domain.

Delay-tolerant networks (DTNs) are networks where there is no immediate connection between the source and the destination. Instead, nodes in these networks use a store–carry–forward method to route traffic. However, approaches that rely on flooding the network with unlimited copies of messages may not be effective if network resources are limited. On the other hand, quota-based approaches are more resource-efficient but can have low delivery rates and high delivery delays. This paper introduces the Enhanced Message Replication Technique (EMRT), which dynamically adjusts the number of message replicas based on a node’s ability to quickly disseminate the message. This decision is based on factors such as current connections, encounter history, buffer size history, time-to-live values, and energy. The EMRT is applied to three different quota-based protocols: Spray and Wait, Encounter-Based Routing (EBR), and the Destination-Based Routing Protocol (DBRP). The simulation results show that applying the EMRT to these protocols improves the delivery ratio, overhead ratio, and latency average. For example, when combined with Spray and Wait, EBR, and DBRP, the delivery probability is improved by 13%, 8%, and 10%, respectively, while the latency average is reduced by 51%, 14%, and 13%, respectively.

Fog computing is a disruptive technology in the big data analytics area. Smartphone users and organizations use cellular services, which can support decision-making in disaster scenarios with the data that have been collected. Nevertheless, the regular communication infrastructure can be damaged by disasters. NTT provided an easily deployable solution to construct an emergency communication network (ECN), but ECNs are slow at propagating big data due to their limited transmission capabilities. One major issue is efficiently integrating data processing in the ECN to realize effective data processing and transmission in disaster scenarios. In this paper, we present—a detailed mathematical model to represent data processing and transmission in an ECN fog network; an NP-hard proof for the problem of optimizing the overall delay; and a novel algorithm to minimize the overall delay for wirelessly-networked disaster areas that can be run in real-time. We evaluated the systems across various transmission speeds, processing speeds, and network sizes. We also tested the calculation time, accuracy, and percent age error of the systems. Through evaluation, we found that the proposed disaster area adaptive delay minimization (DAADM) algorithm showed to have a reduced overall delay over various network sizes when compared with some conventional solutions. The proposed DAADM algorithm matched the curve of the genetic algorithm (GA), even if its results did not yield delays as small as the GA. The DAADM had one major advantage over the GA which was the processing time, which allows the DAADM to be implemented in a real-time system, where a GA solution would take far too much time.

Ad-hoc networks have long been studied as an ideal technology to provide communications in emergency operations when network infrastructures are not available. Nevertheless, this area has not yet delivered enough mature technologies or working prototypes. We suspect that, among other issues, this is due to a lack of understanding of this application domain that forces researchers to make too many assumptions. One of those concerns is the mobility of network nodes. This paper describes, analyzes, and simulates the mobility traces of a fire department during 30 wildfires. The analysis shows interesting insights into the communication range and the type of network in these scenarios. For instance, multi-hop routes are unlikely, so the network behaves like a delay-tolerant network. In addition, the simulation results present a clear image of the network performance under different circumstances that can be used to design applications. We found that the network capacity is low due to the sparse network connectivity. Moreover, the buffer size has a much bigger impact on data delivery than the delay-tolerant routing protocol selected. We think that these are valuable insights and that the traces constitute an important asset for the research community.

In tactical mobile ad hoc networks, unmanned vehicles such as ground maneuvering nodes or aircraft, are increasingly expected to be exploited for information collection in battlefields or dangerous areas on behalf of soldiers in consideration of their safety. The primary function of this networking system is to conduct military surveillance and reconnaissance through unmanned vehicles, which are teleoperated via a central node by sending command messages in real time. This requires simultaneous network traffic flow in both directions, i.e., uplink and downlink, both of which need to occur in real time with high reliability. In this paper, we propose a novel centralized time-division multiple access (TDMA) protocol to guarantee network reliability and quality of service regarding the bidirectional traffic. We develop a bidirectional-pipelined TDMA (BiPi-TMAC) protocol that consists of three parts: a slot-requesting procedure with bandwidth requirement, a depth-based pipelined slot allocation algorithm, and multiple MAC queue management for prioritized packet scheduling. We implement and evaluate the proposed scheme through the ns-3 simulator and show that it improves performance in terms of both uplink and downlink traffic.

In cognitive radio ad hoc networks (CRAHNs), the secondary users' links are interrupted by the arrival of primary users, which leads to a significant increase of the number of transmissions per packet. Since network coding and opportunistic routing can reduce the number of transmissions over unreliable wireless links, they are more suitable for CRAHNs. Network coding-based opportunistic routing has been well studied in previous works for traditional ad hoc networks. However, existing approaches have limitations to handle CRAHNs. First, the routing decisions of these methods aim to find one optimal forwarding set for the whole path from the source to the destination. If the channel conditions change dynamically, the pre-selected forwarding set may become unavailable or non-optimal. Second, their coding schemes are not efficient enough to cope with the dynamic spectrum variation in CRAHNs. In this paper, we attempt to overcome these limitations and propose a network-coding-based geographic segmented opportunistic routing scheme for CRAHNs, by fully embracing its characteristics. In our scheme, the whole path from the source to the destination is cut down into several smaller opportunistic route segments, where the packets are transmitted through multiple segments based on a step-by-step forwarding procedure until all the packets are delivered to the destination. Since our scheme utilizes only local spectrum opportunities, topology information, and geometric conditions to compute the forwarding set for each short-term opportunistic route segment, it can better adapt to dynamic spectrum environments and changing network topologies in CRAHNs. Furthermore, we construct a coding graph to show that our coding problem is a reduction from the maximum clique problem, and we propose an efficient network coding strategy to solve it. Simulation results show that our scheme can achieve a considerable performance, compared with the latest opportunistic routing protocols designed for CRAHNs.

In the first part of the paper, we modeled and characterized the underwater radio channel in shallowwaters. In the second part,we analyze the application requirements for an underwaterwireless sensor network (U-WSN) operating in the same environment and perform detailed simulations. We consider two localization applications, namely self-localization and navigation aid, and propose algorithms that work well under the specific constraints associated with U-WSN, namely low connectivity, low data rates and high packet loss probability. We propose an algorithm where the sensor nodes collaboratively estimate their unknown positions in the network using a low number of anchor nodes and distance measurements from the underwater channel. Once the network has been self-located, we consider a node estimating its position for underwater navigation communicating with neighboring nodes. We also propose a communication system and simulate the whole electromagnetic U-WSN in the Castalia simulator to evaluate the network performance, including propagation impairments (e.g., noise, interference), radio parameters (e.g., modulation scheme, bandwidth, transmit power), hardware limitations (e.g., clock drift, transmission buffer) and complete MAC and routing protocols. We also explain the changes that have to be done to Castalia in order to perform the simulations. In addition, we propose a parametric model of the communication channel that matches well with the results from the first part of this paper. Finally, we provide simulation results for some illustrative scenarios.

LoRa is a long-range and low-power radio technology largely employed in Internet of Things (IoT) scenarios. It defines the lower physical layer while other protocols, such as LoRaWAN, define the upper layers of the network. A LoRaWAN network assumes a star topology where each of the nodes communicates with multiple gateways which, in turn, forward the collected data to a network server. The main LoRaWAN characteristic is the central role of the gateways; however, in some application scenarios, a much lighter protocol stack, relying only on node capabilities and without the presence of gateways, can be more suitable. In this paper, we present a preliminary study for realizing a LoRa-based mesh network, not relying on LoRaWAN, that implements a peer-to-peer communication between nodes, without the use of gateways, and extends node reachability through multi-hop communication. To validate our investigations, we present a hardware/software prototype based on low-power-consumption devices, and we preliminarily assess the proposed solution.

Abstract The scheduling algorithm is a fundamental design problem to allocate resources amongst different entities in distributive wireless sensor networks (WSNs). These sensor nodes have limited power and non-replenishable energy resources. In WSNs, the duty cycling mechanism is commonly used to save energy due to idle listening. On the other hand, a fixed duty cycling mechanism increases transmission latency in WSNs. Therefore, in order to ensure the prolonged network-life of WSNs, the medium access control (MAC) protocol should be tackled in an efficient manner to improve energy efficiency by minimizing idle listening, maximizing sleep duration, and eliminating data collision. This paper proposes a practical Adaptive Sleep Efficient Hybrid Medium Access Control (AEH-MAC) algorithm in which the key idea is to dynamically adjust nodes’ sleep time to improve the scheduling in WSNs. The AEH-MAC allows nodes to adjust sleep time dynamically according to the traffic load and coordinate wakeup time with neighbour nodes. A series of short taken packets are transmitted to wake the receiver, and a prediction field is introduced in the ACK packets (GRANT/RELEASE) to reduce the waiting time of the source node. In the proposed algorithm, each node maps a conflict-free time slot for itself up to two-hop neighbouring nodes. The simulation results show that the AEH-MAC algorithm achieves high performance in terms of runtime, number of rounds, energy consumption, and slot reservation.

Abstract Multiple-input multiple-output (MIMO) technologies have been shown to potentially improve the performance of network. Many traditional medium access control (MAC) protocols, such as spatial time division multiple access (STDMA), may not support MIMO technologies directly and not make full use of the feature of MIMO, which may be a limitation in the practical application in ad hoc networks. Therefore, in this paper, we propose a dynamic time slot allocation and stream control for MIMO STDMA (DTSMS) protocol to improve STDMA in performance. Utilizing stream control technology of MIMO and reservation scheme, DTSMS makes improvement on network throughput and avoids the mutual interference of neighbor links. Thus, DTSMS can support both unicast and multicast simultaneously. Moreover, we implement the dynamic time slot allocation scheme in DTSMS to guarantee the transmission efficiency of packets with high cross-layer transmission parameters, such as the packet priority, neighbor node density, or link quality. Utilizing the collected cross-layer information, the proposed scheme allocates time slots for all nodes dynamically according to the changes of network topology and nodes’ transmission parameters. Finally, the effectiveness of the protocol is demonstrated by numerical analysis and simulations. The results show that DTSMS outperforms STDMA in terms of network throughput and delay. Furthermore, compared to our previous TTS-MIMO, DTSMS can decrease the delay of packets with high transmission parameters and improve the quality of service (QoS).

Content-centric networking (CCN) introduces a paradigm shift from a host centric to an information centric communication model for future Internet architectures. It supports the retrieval of a particular content regardless of the physical location of the content. Content caching and content delivery networks are the most popular approaches to deal with the inherent issues of content delivery on the Internet that are caused by its design. Moreover, intermittently connected mobile environments or disruptive networks present a significant challenge to CCN deployment. In this paper, we consider the possibility of using mobile users in improving the efficiency of content delivery. Mobile users are producing a significant fraction of the total Internet traffic, and modern mobile devices have enough storage to cache the downloaded content that may interest other mobile users for a short period too. We present an analytical model of the CCN framework that integrates a delay tolerant networking architecture into the native CCN, and we present large-scale simulation results. Caching on mobile devices can improve the content retrieval time by more than 50%, while the fraction of the requests that are delivered from other mobile devices can be more than 75% in many cases.

The traditional MAC protocol in ad hoc networks includes carrier sensing to judge the busy/idle state of a channel. However, in airborne tactical networks, the results of carrier sensing are usually inaccurate due to the wide distribution of nodes, large communication distance, and high-dynamic network topology, and the carrier sensing causes a large transmission delay and low channel utilization ratio. In this paper, we propose a novel channel busy recognition mechanism combined with auto regressive (AR) forecasting, namely, L-steps-revise AR (LS-AR). LS-AR predicts the number of bursts in the current time frame based on the number of bursts received in previous time frames, and the predicted number of bursts determines the channel busy/idle state. The difference between the predicted value and the true value serves as the means for correcting the next prediction. This mechanism avoids the delay caused by carrier sensing, improves the channel utilization ratio and provides a more accurate judgment to enable different priority packets to access a channel. The simulation results show that the algorithm can accurately predict the channel load and meet the requirements of the MAC protocol in airborne tactical networks.

The messages in vehicular ad hoc networks (VANET) are vulnerable to attack in the open wireless environment. Group communication in VANET is receiving more attention, which confronts many security issues. First, only users who have passed legal authentication can communicate in the group. The ring signature is an effective solution. In addition, the group membership in the vehicular self-organising network changes rapidly, which leads to dynamic adjustment of group members. It is necessary to consider the computing power and communication capability of each node in the group members. To speed up the authentication process, a roadside unit with more computing power and communication capability than vehicles is selected as the signature agent, which effectively reduces the computational load of vehicles and accelerates the communication throughput. Meanwhile, the computational task and communication overhead have not been well-solved. To address these issues, this paper proposed an efficient proxy ring signature scheme for VANET to achieve higher signature efficiency and lower transmission overhead. The scheme allows both privacy protection and original signer tracing. Security analysis shows that the proposed scheme meets the security requirements of VANET.

Unmanned aerial vehicles (UAVs) are widely used in our modern society and their development is rapidly accelerating. Flying Ad Hoc Networks (FANETs) have opened a new window of opportunity to create new value-added services. However, the characteristics that make FANETs unique, such as node mobility, node distance, energy constraints, etc., imply that several guidelines need to be considered for their successful deployment. Although numerous routing protocols have been proposed for FANETs, due to the wide range of applications in which FANETs can be applied, not all routing protocols can be used. Due to this challenge, after breaking down and classifying the different types of existing routing protocols for FANET, this paper analyzes and compares the performance of several routing protocols (Babel, BATMAN-ADV, and OLSR) in terms of throughput and packet loss in a real deployment composed of several UAV nodes using 2.4 and 5 GHz WiFi networks. The results show that Babel achieves better performance in the studied metrics than OLSR and BATMAN-ADV, while BATMAN-ADV delivers significantly lower performance. This experimental study confirms the importance of choosing the proper routing protocol for FANETs and their performance evaluation, something that will be extremely important in a few years when this type of network will be common in our day-to-day life.

In mobile ad hoc networks (MANETs), it is effective to retrieve data items using top-k query. However, accurate results may not be acquired in environments when malicious nodes are present. In this paper, we assume that malicious nodes attempt to replace necessary data items with unnecessary ones (we call these data replacement attacks), and propose methods for top-k query processing and malicious node identification based on node grouping in MANETs. In order to maintain the accuracy of the query result, nodes reply with k data items with the highest score along multiple routes, and the query-issuing node tries to detect attacks from the information attached to the reply messages. After detecting attacks, the query-issuing node tries to identify the malicious nodes through message exchanges with other nodes. When multiple malicious nodes are present, the query-issuing node may not be able to identify all malicious nodes at a single query. It is effective for a node to share information about the identified malicious nodes with other nodes. In our method, each node divides all nodes into groups by using the similarity of the information about the identified malicious nodes. Then, it identifies malicious nodes based on the information on the groups. We conduct simulation experiments by using a network simulator, QualNet5.2, to verify that our method achieves high accuracy of the query result and identifies malicious nodes.

With the deployment of Vehicular Ad hoc Networks (VANETs), new transport safety and efficiency applications are emerging. One of the fields where the adoption of information and communication technologies (ICT) is expected to bring great benefits, is emergency systems. A properly designed emergency vehicle warning system should provide car drivers with adequate reaction times and additional information, complementing the currently used lights and sirens. The objective is to increase road safety and to create conditions for a fast and reliable movement of emergency vehicles (EVs). The available literature addressing privacy issues in VANET-based emergency vehicle warning systems is strongly limited. In this paper, the privacy ensuring emergency vehicle approaching warning system (PEEV-WS) is proposed based on a requirements analysis. Privacy is ensured by avoiding transmissions of sensitive information (e.g., expected EV route) over the wireless channel. This is achieved by assigning the decision-making responsibility to an EV and determining which vehicles can potentially interfere with the EV in the near future, and to notify those vehicles only by unicasting vehicle-customized information. The performance of the system is evaluated by federated telco-traffic simulations in terms of end-to-end delay and message delivery probability for three commonly used ad hoc routing protocols—Ad hoc On-Demand Distance Vector (AODV), Greedy Perimeter Stateless Routing (GPSR), and Dynamic MANET On-demand (DYMO), as well as in terms of reaction time, which the system provides to the drivers. Despite low applicability of the ad hoc routing protocols for vehicular communication, especially for low-latency and high-frequency applications, the simulations of the communication network demonstrate that the AODV protocol, with the modified configuration, can support the emergency vehicle warning system. The traffic simulations confirm that the system has the potential to provide drivers with sufficient reaction time.

The vehicular internet will drive the future of vehicular technology and intelligent transportation systems (ITS). Whether it is road safety, infotainment, or driver-less cars, the vehicular internet will lay the foundation for the future of road travel. Governments and companies are pursuing driver-less vehicles as they are considered to be more reliable than humans and, therefore, safer. The vehicles today are not just a means of transportation but are also equipped with a wide range of sensors that provide valuable data. If vehicles are enabled to share data that they collect with other vehicles or authorities for decision-making and safer driving, they thereby form a vehicular network. However, there is a lot at stake in vehicular networks if they are compromised. With the stakes so high, it is imperative that the vehicular networks are secured and made resilient to any attack or attempt that may have serious consequences. The vehicular internet can also be the target of a cyber attack, which can be devastating. In this paper, the opportunities that the vehicular internet offers are presented and then various security and privacy aspects are discussed and some solutions are presented.

Realistic mobility models can demonstrate more precise evaluation results because their parameters are closer to the reality. In this paper a realistic Fuzzy Mobility Model has been proposed. This model has rules which are changeable depending on nodes and environmental conditions. It seems that this model is more complete than other mobility models.After simulation, it was found out that not only considering nodes movement as being imprecise (fuzzy) has a positive effects on most of ad hoc network parameters, but also, more importantly as they are closer to the real world condition, they can have a more positive effect on the implementation of ad hoc network protocols.

Cognitive radio network and vehicular ad hoc network (VANET) are recent emerging concepts in wireless networking. Cognitive radio network obtains knowledge of its operational geographical environment to manage sharing of spectrum between primary and secondary users, while VANET shares emergency safety messages among vehicles to ensure safety of users on the road. Cognitive radio network is employed in VANET to ensure the efficient use of spectrum, as well as to support VANET’s deployment. Random increase and decrease of spectrum users, unpredictable nature of VANET, high mobility, varying interference, security, packet scheduling, and priority assignment are the challenges encountered in a typical cognitive VANET environment. This paper provides survey and critical analysis on different challenges of cognitive radio VANET, with discussion on the open issues, challenges, and performance metrics for different cognitive radio VANET applications.

The spectrum handoff is highly critical as well as challenging in a cognitive radio ad hoc network (CRAHN) due to lack of coordination among secondary users (SUs), which leads to collisions among the SUs and consequently affects the performance of the network in terms of spectrum utilization and throughput. The target channel selection mechanism as part of handoff process can play an enormously significant role in minimizing the collisions among the SUs and improving the performance of a cognitive radio network (CRN). In this paper, an enhanced target channel selection scheme based on imperfect channel state prediction is proposed for the spectrum handoff among the SUs in a CRAHN. The proposed scheme includes an improved frame structure that increases coordination among the SUs in the ad hoc environment and helps in organizing the SUs according to the shortest job first principle during channel access. Unlike the existing prediction-based spectrum handoff techniques, the proposed scheme takes into account the accuracy of channel state prediction; the SUs affected due to false prediction are compensated by allowing them to contend for channel access within the same transmission cycle and thus enabling them to achieve higher throughput. The proposed scheme has been compared with the contemporary spectrum handoff schemes and the results have demonstrated substantial improvement in throughput and extended data delivery time by virtue of the reduced number of collisions.

The Internet of Things (IoT) is an emerging technology that aims to enable the interconnection of a large number of smart devices and heterogeneous networks. Ad hoc networks play an important role in the designing of IoT-enabled platforms due to their efficient, flexible, low-cost and dynamic infrastructures. These networks utilize the available resources efficiently to maintain the Quality of Service (QoS) in a multi-hop communication. However, in a multi-hop communication, the relay nodes can be malicious, thus requiring a secured and reliable data transmission. In this paper, we propose a QoS-aware secured communication scheme for IoT-based networks (QoS-IoT). In QoS-IoT, a Sybil attack detection mechanism is used for the identification of Sybil nodes and their forged identities in multi-hop communication. After Sybil nodes detection, an optimal contention window (CW) is selected for QoS provisioning, that is, to achieve per-flow fairness and efficient utilization of the available bandwidth. In a multi-hop communication, the medium access control (MAC) layer protocols do not perform well in terms of fairness and throughput, especially when the nodes generate a large amount of data. It is because the MAC layer has no capability of providing QoS to prioritized or forwarding flows. We evaluate the performance of QoS-IoT in terms of Sybil attack detection, fairness, throughput and buffer utilization. The simulation results show that the proposed scheme outperforms the existing schemes and significantly enhances the performance of the network with a large volume of data. Moreover, the proposed scheme is resilient against Sybil attack.

This paper presents the evolution of protocol MMAC-CR (Multichannel MAC protocol for Cognitive Radio). To this end, we analyze the advantages of the protocol and we study the operational activities that pertain to cognitive radio where the medium access control protocol plays a very influential role, namely spectrum mobility, channel sensing, resource allocation, and spectrum sharing. Moreover, we describe the variations of the MMAC-CR protocol according to the negotiation and reservation mechanisms implemented.

A mobile ad hoc network (MANET) is considered as an autonomous network, which consists of mobile nodes, which communicate with each other over wireless links. When there is no fixed infrastructure, nodes have to cooperate in order to incorporate the necessary network functionality. Ad hoc on Demand Distance Vector (AODV) protocol is one of the primary principal routing protocols implemented in Ad hoc networks. The security of the AODV protocol is threaded by a specific kind of attack called ‘Black Hole’ attack. This paper presents a technique to prevent the Black hole attack by implementing negotiation with neighbors who claim to maintain a route to destination. Negotiation process is strengthen by apriori method to judge about suspicious node. Apriori algorithm is an effective association rule mining method with relatively low complexity, which is proper for MANETs. To achieve more improvement, fuzzy version of ADOV is used. The simulation results indicate that the proposed protocol provides more securable routing and also more efficiency in terms of packet delivery, overhead and detection rate than the conventional AODV and fuzzy AODV in the presence of Black hole attacks.

It is expected that many networks will be providing services at a time in near future and those will also produce different interfering signals for the current Slotted ALOHA based systems. A random packet destruction Denial of Service (DoS) attacking signal can shut down the Slotted ALOHA based networks easily. Therefore, to keep up the services of Slotted ALOHA based systems by enhancing the secured operating regions in the presence of the interfering signals from other wireless systems and DoS attacking signals is an important issue and is investigated in this paper. We have presented four different techniques for secured operating regions enhancements of Slotted ALOHA protocol. Results show that the interfering signals from other wireless systems and the DoS attacking signals can produce similar detrimental effect on Slotted ALOHA. However, the most detrimental effect can be produced, if an artificial DoS attack can be launched using extra false packets arrival from the original network. All four proposed secured operating regions enhancement techniques are easy to implement and have the ability to prevent the shutdown of the Slotted ALOHA based networks.

Ad hoc wireless network consists of a set of wireless nodes communicating with each other without a pre-defined infrastructure. They communicate by forwarding packets which can reach wireless nodes that do not exist in the range of the direct radio transmission. Designing ad hoc network routing protocols is a challenging task because of its decentralized infrastructure which makes securing ad hoc networks more and more challenging. Dynamic Source Routing (DSR) protocol is a popular routing protocol designed for use in wireless ad hoc networks. Mobile agent is a promising technology used in diverse fields of network applications. In this paper, we try to implement DSR using mobile agents for securing this type of wireless network. Hybrid encryption technique (symmetric key encryption/public key encryption) is used to improve performance; where symmetric keys are used to encrypt routing data to authenticate and authorize node sending data, while, public keys are used for the exchange of symmetric keys between nodes. We found that DSR may be secured using mobile agents with competitive performance.

One of the most overlooked factors in evaluating performance of ad hoc routing protocols is the variation in received signal strength known as fading. Many types of routing protocols have been proposed based on simplified assumptions and unrealistic propagation models that neglect the effect of fading. The choice of propagation models have a great impact on performance, so realistic models are necessary to consider the effect of fading as far as an accurate analysis of performance of the routing protocols is concerned. In this paper, comparative analysis of two on demand ad hoc routing protocols is performed in order to study the impact of mobility and fading on performance. The non-fading models such as free space and two ray ground are simulated for comparison with fading models such as Shadowing, Ricean, and Rayleigh fading. The simulation results reveal that the fading models have a significantly degraded network performance with respect to two mobility scenarios.

The explosive growth in the use of real-time applications on mobile devices has resulted in new challenges to the design of medium access control (MAC) protocols for ad hoc networks. In this paper, we propose an energy efficient cognitive radio (CR) MAC protocol for QoS provisioning called ECRQ-MAC, which integrate the spectrum sensing at physical (PHY) layer and the channel-timeslots allocation at MAC layer. We consider the problem of providing QoS guarantee to CR users as well as to maintain the most efficient use of scarce bandwidth resources. The ECRQ-MAC protocol exploits the advantage of both multiple channels and TDMA, and achieves aggressive power savings by allowing CR users that are not involved in communication to go into sleep mode. The proposed ECRQ-MAC protocol allows CR users to identify and use the unused frequency spectrum of licensed band in a way that constrains the level of interference to the primary users (PUs). Our scheme improves network throughput significantly, especially when the network is highly congested. The simulation results show that our proposed protocol successfully exploits multiple channels and significantly improves network performance by using the licensed spectrum opportunistically and protects QoS provisioning over cognitive radio ad hoc networks.

This survey on Quality of Service (QoS) in multicast ad hoc networks uses a framework based on the mechanisms in three important elements: resource estimations, multicast tree/mesh administration, and multicast routing. Our contribution is an exploration of the design space and an identification of areas that have not been fully explored. We discuss the design space of central mechanisms and classify proposed QoS multicast schemes according to the mechanisms they used. In addition, we summarize the scenarios used for evaluating their performance. Furthermore, we identify issues, mechanisms, and scenarios that have not been fully investigated in existing works. The paper provides a coherent understanding of design principles, conceptual operation, and evaluated scenarios of schemes designed for QoS multicast application in mobile ad hoc networks (MANETs). It also outlines new areas for future research in this field.

Wireless ad hoc sensor networks differ from wireless ad hoc networks from the following perspectives: low energy, lightweight routing protocols, and adaptive communication patterns. This paper proposes an energy-aware routing protocol (EARP) suitable for ad hoc wireless sensor networks and presents an analysis for its energy consumption in various phases of route discovery and maintenance. Based on the energy consumption associated with route request processing, EARP advocates the minimization of route requests by allocating dynamic route expiry times. This paper introduces a unique mechanism for estimation of route expiry time based on the probability of route validity, which is a function of time, number of hops, and mobility parameters. In contrast to AODV, EARP reduces the repeated flooding of route requests by maintaining valid routes for longer durations.

Development of the efficient power aware protocol is the need of today s adhoc networks. Although developing battery efficient systems that have low cost and complexity, remains a crucial issue. In order to facilitate communication within a mobile adhoc network, an efficient routing protocol is required to discover routes between mobile nodes. Power is one of the most important design criteria for adhoc networks as batteries provide limited working capacity to the mobile nodes. Power failure of a mobile node not only affects the node itself but also its ability to forward packets on behalf of others and hence affects the overall network lifetime. Much research efforts have been devoted to develop energy aware routing protocols. In this paper we propose an efficient algorithm, which maximizes the network lifetime by minimizing the power consumption during the source to destination route establishment. As a case study proposed algorithm has been incorporated along with the route discovery procedure of AODV and by simulation it is observed that proposed algorithm s perperformance is better as compare to AODV and DSR in terms of various energy related parameters like Total Energy Consumption, Average Energy Left Per Alive Node, Node Termination Rate, and Network Lifetime for different network scenarios.

Recently, research topics are focusing on clustering approaches for Ad hoc networks due to their effectiveness in building a virtual backbone formed by a set of suitableclusterheads (CH) to guarantee the communications acrossclusters. In this paper, we propose a clustering approach to elect suitable nodes’ representatives and to store minimum topology information by reducing the propagation of routing information which facilitates the spatial reuse of resource and increase the system capacity. The clusters must adapt dynamically to the environment changes, we also propose a distributed maintenance procedure that allows managing nodes’ adhesion, nodes’ handoff and CHs’ re-election. Based on our analytical model used to estimate the quality of service (QoS) parameters, we implement an admission control algorithm to determine the number of members inside a cluster that can be accommodated while satisfying the constraints imposed by the current applications. This might effectively drive congestion avoidance on the CH andinterclusters load-balancing to achieve better network resource utilization. The obtained results will help us to readjust the clustering algorithm metrics in order to provide better maintenance and QoS guarantees depending on the used applications. Through numerical analysis and simulations, we have studied the performance of our model and compared it with that of other existing algorithms. The results demonstrate better performance in terms of number of clusters, number of handoffs, number of transitions (state change) on CHs, QoS parameters, load balancing and scalability. We also observed how the connectivity and the stability are maximized when the number of nodes increases in presence of the mobility.

Wireless technology is becoming a leading option for future Internet access. Transmission Control Protocol (TCP) is one of the protocols designed on the basis of the transmission characteristics in wired networks. It is known that the TCP performance deteriorates drastically under a wireless communication environment. On the other hand, many wireless networking standards such as IEEE 802.11a, 802.11b, and 802.11g have multirate capability. Therefore, adaptive rate control methods have been proposed for ad hoc networks. However, almost methods require the modification of the request to send (RTS) and clear to send (CTS) packets. Therefore, the conventional methods are not compatible with the standardized system. In this paper, we propose adaptive rate control mechanisms for ad hoc networks. Our mechanisms are based on the RTS/CTS mechanisms. However, no modifications to the RTS and CTS packets are required in the proposed method. Therefore, our proposed method can attempt to satisfy the conventional IEEE 802.11 standards. Moreover, an adequate transmission rate is selected based on an estimated TCP throughput performance. From simulation results, it is observed that the proposed method can improve the throughput performance without any modification of packet structures.

A CDMA-based mobile Ad Hoc networks face two main design challenges. One is to periodically update connectivity information, namely, neighboring nodes and the codes used by neighboring nodes. The other is to guarantee that there is no code collision in two hops' distance. This paper proposes an enhanced time-spread broadcasting schedule for connectivity information update. Based on the connectivity information, a code assignment and potential code collision resolution scheme to solve hidden/exposed nodes problem is proposed. Simulation results demonstrate the efficiency and effectiveness of the proposed schemes.

Mobile ad hoc networks (MANET) are very difficult to design in terms of scenarios specification and propagation modeling. All these aspects must be taken into account when designing MANET. For cost-effective designing, powerful and accurate simulation tools are needed. Our first contribution in this paper is to provide a global approach process (GAP) in channel modeling combining scenarios and propagation in order to have a better analysis of the physical layer, and finally to improve performances of the whole network. The GAP is implemented in an integrated simulation tool, Ad-SMPro. Moreover, channel statistics, throughput and delay are some key points to be considered when studying a mobile wireless networks. A carefully analysis of mobility effects over second order channel statistics and system performances is made based on our optimized simulation tool, Ad-SMProl. The channel is modeled by large scale fading and small scale fading including Doppler spectrum due to the double mobility of the nodes. Level Cross Rate and Average Duration of Fade are simulated as function of double mobility degree, a defined to be the ratio of the nodes' speeds. These results are compared to the theoretical predictions. We demonstrate that, in mobile ad hoc networks, flat fading channels and frequency-selective fading channels are differently affected. In addition, Bit Error rate is analysed as function of the ratio of the average bit energy to thermal noise density. Other performances (such as throughput, delay and routing traffic) are analysed and conclusions related to the proposed simulation model and the mobility effects are drawn.

In this paper we present ViStA-XL, a Cross-Layer (XL) design aiming to optimize the overall performance of videostreaming services over Mobile Ad Hoc Networks (MANETs). The idea relies on applying optimization strategies to different network layers in a holistic way. In ViStA-XL, a real-time Optimizer (XLO) periodically gathers information of the state of node and network from different layers of the stack of protocols, takes optimization decisions, and then modifies some parameters of the protocols accordingly. In addition, our proposal exploits path diversity through MM-DSR (Multipath MultimediaDynamic Source Routing) protocol as a means to reinforce the Quality of Service (QoS) provision to multi-layer encoded videostreaming applications, by protecting the most important video information packets, balancing the load and decreasing the endto-end delay. To show the advantages of our approach, we have developed and tested an algorithm based on ViStA-XL. Simulation results show that our proposed network design can improve the performance of video-streaming transmissions over MANETs in spite of frequent changes in network and node operating conditions.

Mobile ad hoc networks (MANETs) are dynamic mobile networks that can be formed in the absence of any pre-existing communication infrastructure. In addition to node mobility, a MANET is characterized by limited resources such as bandwidth, battery power, and storage space. The underlying assumption in MANETs is that the intermediate nodes cooperate in forwarding packets. However, this assumption does not hold in commercial and emerging civilian applications. MANETs are vulnerable to Denial of Service (DoS) due to their salient characteristics. There is a need to provide an incentive mechanism that can provide cooperation among nodes in the network and improve overall network performance by reducing DoS attacks. In this paper, we propose a reputation-based incentive mechanism for detecting and preventing DoS attacks. DoS attacks committed by selfish and malicious nodes were investigated. Our scheme motivates nodes to cooperate and excludes them from the network only if they fail to do so. We evaluated the performance of our scheme using the packet delivery ratio, the routing and communication overhead, and misbehaving node detection in a discrete event-simulation environment. The results indicate that a reputation-based incentive mechanism can significantly reduce the effect of DoS attacks and improve performance in MANETs.

U radu je razmatrana mogućnost primene ad hoc mobilnih komunikacionih mreža za povezivanje senzorskih sistema, kao čvornih izvora informacija i kao čvornih elemenata komunikacione mrežne infrastrukture u okviru komandno-informacionog sistema. Korak u evoluciji bežičnih komunikacija predstavljaju ad hoc mreže koje se javljaju u obliku grupa prenosnih računara, mobilnih telefonskih uređaja, personalnih digitalnih asistenta i sličnih korisničkih uređaja, kao i u obliku mreže autonomnih elektronskih senzorskih uređaja. Osnovnu karakteristiku svake ad hoc mreže predstavlja uspostavljanje komunikacije između mrežnih čvorova bez unapred postavljene fiksne mrežne infrastrukture. Umesto mreže fiksnih čvorova i baznih stanica karakterističnih za postojeću bežičnu mrežnu infrastrukturu, nosilac komunikacije postaje mreža čvornih sofisticiranih senzorskih uređaja - stanica. Mogućnost eliminisanja potrebe fiksne komunikacione infrastrukture u sistemima obezbeđenja i kontrole teritorije od izuzetnog je značaja u vojnim primenama, posebno sa aspekta pripreme i vođenja savremenih operacija. Praćenje situacije u vazdušnom prostoru na osnovu vizuelnih osmatračkih i zvukometrijskih stanica, senzorska zaštita objekata i prostora i prikupljanje relevantnih informacionih podataka predstavljaju samo neke od primera praktične primene ad hoc mreža. / The application possibility of ad hoc mobile communication network for connecting sensor systems, as node sources of information and as node elements of communication network's infrastructure, in command information system is presented in this paper. The next step in wireless communication evolution is ad hoc networks, which appear in the form of groups of mobile computers, mobile phone devices, personal digital assistants and in the form of a network of autonomy electronically sensors devices. The basic characteristic of every ad hoc network is establishing communication between network nodes without fixed network infrastructure, established in advance. Instead of fix network nodes and basic stations, that are typical of available wireless networks infrastructure, network of nodes of sophisticated sensors devices (stations) became most important for communication. Possibility of eliminating the need for fixed communication infrastructure in security systems and systems for territory control, is very important in military, especially for the preparation and leading of modern operations. Some of the examples for practical application of ad hoc networks are: air surveillance system based on visual surveillance and acoustic-metric stations, sensor systems for protection of objects and space and collection of relevant information data.

Ad hoc networks are wireless networks with new architectures, which are formed in any environment that is needed, without a fixed infrastructure. Due to a lack of central management and fixed infrastructure, and the poor physical security of nodes, these networks are extremely vulnerable. As the usage and development of ad hoc networks increases, problems related to these networks are a popular research topic. Hence, efficient and effective algorithms, such as bee algorithms, were created, which were inspired by the foraging principles of honey bees. In this paper, we study algorithms based on bee swarms in ad hoc networks. doi:10.14456/WJST.2015.2