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Summary The cluster networking protocols are the roots that embed intelligent decision‐making and enhance the lifespan of wireless sensor networks (WSNs). Wireless sensors with limited capabilities face several challenges due to the heterogeneous application environments. Especially, the mobility‐incorporated sensors in most situations trouble the cluster network's robustness. Many cluster networking protocols have been presented in the past to enhance the network lifespan and data delivery ratio. However, they lack a dedicated and efficient mechanism for mobility assistance, an adequate cluster management process and cluster head selection criteria. To overcome these issues and for the uniform energy load distribution, we propose a mobility‐compatible cache controlled cluster networking protocol (MC‐CCCNP) in this paper. It is an energy‐efficient cluster networking protocol that supports sensor movement. Network resource management and routing are controlled distributively by an optimal number of cache nodes. It defines a new strategy for cache node deployment based on neighbour density as well as a weight formula for cluster head selection and cluster formation based on the residual energy, the distance to the base station and the node velocity. It also includes techniques for detaching and reconnecting a mobile node to an appropriate cluster cache if it crosses the cluster boundary. We simulate and compare the performance of our protocol with the centralised energy‐efficient clustering routing, energy‐efficient mobility‐based cluster head selection protocol and dual tier cluster‐based routing protocols over different network configurations with varying mobility, scalability and heterogeneity. The MC‐CCCNP showed remarkable improvements in energy utilisation uniformity and energy consumption. With the improved network lifespan, it also maintains a higher data throughput rate of 95% or more in almost all network configurations. [ABSTRACT FROM AUTHOR]

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 FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Processing queries in wireless sensor networks causes quality of service challenges such as data latency and validity. In fact, this paper is going to shed light on identifying the right trade‐off between latency and the freshness of the data. For this purpose, a fuzzy logic‐based decision‐making system that assigns incoming queries either to the sensor network, where the queries are waiting to be processed into a queue, or a central database which provides stored and potentially stale data or to a cache server which in turn provides acceptable latency and recent data, is provided. Thus, a new rule‐based system decision is introduced, that minimizes the request latency and returns the most recent data. In addition, a comparison between the approach and other work that is restricted to the database server and sensor network with no focus on the caching server is provided. This paper is going to carry on with the theory of Markov Chain which is more complicated compared to the fuzzy logic system. This approach is confirmed in the basis of an experience is developed with python. [ABSTRACT FROM AUTHOR]

The Ad Hoc networks solves the problem of quickly establishing a temporary Ad Hoc network without the need for fixed facilities. However, problems such as network performance degradation, delay increase, and link interruption are endless. Aiming at the problem of shortening the survival time of Ad Hoc networks nodes, this paper proposes an improved AODV routing algorithm EC-MAODV (Energy Consumption-Modification AODV) based on energy consumption. EC-MAODV takes energy as the starting point, determines the time extension based on the residual energy of the current node, balance the power consumption of each node, and extends the networks lifetime. The effectiveness of EC-MAODV routing algorithm is proved by network simulator NS-3. The simulation results show that compared with the AODV routing protocol, the algorithm in this paper has more than 7% improvement and 19% increase in average delay and node lifetime. It can effectively prolong the life of the network, reduce the number of dead nodes, effectively solve the energy consumption problem of the wireless Ad Hoc network, and improve the overall performance of the network. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this paper, we address the problem of implementing distributed slice allocation algorithms for tactical networks deployed in regions lacking a communication infrastructure. We propose a multi-agent game implementation in which Application Slice Agents (ASAs) compete for shared computational and bandwidth resources in the network. We prove that the game can be implemented as a two stage potential game, with the first stage ensuring the selection of computational servers with load balancing, and the second stage improving connectivity and network throughput by promoting inter-slice cooperation. Our proposed analysis framework also incorporates a theoretical model to capture the impact of mitigation methods for timing channel leaks for the shared resources for different slices, and proposes a theoretical framework that allows for a security-delay tradeoff analysis. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This paper proposes a novel scalable reinforcement learning approach for simultaneous routing and spectrum access in wireless ad-hoc networks. In most previous works on reinforcement learning for network optimization, the network topology is assumed to be fixed, and a different agent is trained for each transmission node—this limits scalability and generalizability. Further, routing and spectrum access are typically treated as separate tasks. Moreover, the optimization objective is usually a cumulative metric along the route, e.g., number of hops or delay. In this paper, we account for the physical-layer signal-to-interference-plus-noise ratio (SINR) in a wireless network and further show that bottleneck objective such as the minimum SINR along the route can also be optimized effectively using reinforcement learning. Specifically, we propose a scalable approach in which a single agent is associated with each flow and makes routing and spectrum access decisions as it moves along the frontier nodes. The agent is trained according to the physical-layer characteristics of the environment using a novel rewarding scheme based on the Monte Carlo estimation of the future bottleneck SINR. It learns to avoid interference by intelligently making joint routing and spectrum allocation decisions based on the geographical location information of the neighbouring nodes. [ABSTRACT FROM AUTHOR]

Summary: The main aim of this paper is to address the problem of redundant broadcast packets using the extension of rough set concept. In general, a rough set is a mathematical tool for dealing with issues of uncertainty. In MANET, mobile nodes are moving from one place to another place in a simulation environment; hence, it creates uncertainty issues. Due to the fast mobility of mobile nodes, network metrics such as bandwidth and hop count vary. The findings were useful in identifying and improving the network's performance. The proposed NRS‐based route selection approach has been compared with conventional techniques such as rough set, covering rough set (CRS). The reduced control packets are obtained using pruning concept based on selection of one‐hop and two‐hop nodes. Eventually, the proposed approach proved that it attains a higher throughput (85%), reducing the route request packets (3406) and delay of data transmission (0.02274 s). Also, two well‐known ad hoc routing protocols were used such as Dynamic Source Routing (DSR) and Ad Hoc On‐Demand Distance Vector (AODV) protocols. [ABSTRACT FROM AUTHOR]

Aeronautical Ad-hoc Networks (AANETs) have been proposed as the promising complement to terrestrial networks for promoting the global interconnection to provide in-flight network service, emergency communication, vessel traffic service, etc. However, the large network scale of AANETs may induce severe synchronization overhead when the traditional topology-based networking algorithms are adopted. Moreover, the high-dynamic topology and changeable flight routes make the existing position-based routing algorithms suffer loop routing and forwarding failure. Motivated by these problems, this paper aims at developing efficient and low-cost networking and routing algorithms relying on the concept of dynamic virtual topology which organizes the disordered topology of AANETs into a structural and simplified one. The basic idea is that each connected aircraft is assigned with a unique and sequentially increased Virtual Identifier (VID) and thus all the connected aircrafts are organized into a virtual cluster consisting of one trunk and several branches. An event-driven synchronization mechanism is leveraged for maintaining the virtual topology as well as relieving the communication burden imposed by periodical broadcasting. By jointly considering the geographic locations and the virtual locations of aircrafts, we formulate the routing problem in AANETs as a weighted distance minimization problem, and further propose a novel routing algorithm, namely Trunk-Branch Cooperation aided Routing (TBCR) algorithm. Specifically, TBCR employs the geographic greedy forwarding strategy for enhancing its flexibility and boosts the routing efficiency by adopting the loop-free virtual topology based local forwarding. For extending the networking and routing algorithms to the global range, a multi-domain routing solution is also provided. Extensive experimental results show that the proposed Virtual Topology based Networking (VTN) cooperated with TBCR can reduce at least 30% average end-to-end transmission delay in large-scale AANETs and provide more than 90% lower synchronization overhead than the existing solutions. [ABSTRACT FROM AUTHOR]

In this paper, the outage performance of wireless networks with unstructured topologies is investigated. The network reliability perspective of graph theory is used to obtain the network outage polynomial of generalized wireless networks for both uncorrelated and correlated wireless channels. A relationship is established between the max-flow min-cut theorem and key communication performance indicators. The diversity order is equal to the size of the minimum cut-set between source and destination, and the coding gain is the number of cut-sets with size equal to the minimum cut. An ergodic capacity analysis of arbitrary network topologies based on the network outage polynomial is also presented. Numerical results are used to illustrate the technical definitions and verify the derivations. [ABSTRACT FROM AUTHOR]

Previous work has demonstrated the feasibility of Bluetooth Low Energy (BLE) as an alternative technology for data transfers in inter-vehicular communication (IVC) scenarios. Bluetooth 5.x core specifications enhance the trade-off between energy requirements, communication range and flexibility. In this paper, we aim to analyse the potential of Bluetooth 5 features for VANET applications, proposing a connectionless communication system. By means of field experiments, we evaluate long range and 2 × speed features, defining a set of communication scenarios. This allows us to test both Bluetooth 5.x range and application throughput. The evaluation includes experiments of V2I communications carried out under real highway traffic conditions. The experiments conducted demonstrate that communication ranges up to 300 m may be achieved depending on the communications scenario. The results also show how throughput degrades as the distance between devices increases. The results obtained are used to discuss future work, aimed at deeper analysing Bluetooth 5 features for VANET applications, completing the development of our prototype and evaluating VANET connectionless communications with the features included in the latest Bluetooth 5.2 specification. [ABSTRACT FROM AUTHOR]

Emergence of various types of wireless applications has brought about fast growing and diversified traffic in cellular networks. To gain a comprehensive understanding of the influences caused by the differentiated and dynamic traffic is vital for the design of the next-generation wireless networks. In this paper, we develop a mathematical framework for meta-distribution analysis by utilizing queueing theory and stochastic geometry to capture the spatial (geographical location) and temporal randomness (queue status) of traffic. We derive the ${k}$ -th moment of the conditional successful transmission probability (STP) and the closed-form expressions of the meta distribution for the cell-center users (CCUs) and the cell-edge users (CEUs), respectively. The results are further extended to obtain the analytical expression of the meta distribution by taking the temporal random arrival of traffic into consideration. Moreover, the mean local delays for the CCUs and CEUs are derived. Finally, the impact of key network parameters on the meta distribution and the corresponding mean local delay is investigated. [ABSTRACT FROM AUTHOR]

Shannon showed that to achieve perfect secrecy in point-to-point communication, the message rate cannot exceed the shared secret key rate giving rise to the simple one-time pad encryption scheme. In this paper, we extend this work from point-to-point to networks. We consider a connected network with pairwise communication between the nodes and assume that each node is provided with a certain amount of secret bits before communication commences. An eavesdropper with unlimited computing power has access to all communication and can hack a subset of the nodes not known to the rest of the nodes. We investigate the limits on information-theoretic secure communication with end-to-end encryption for this network. We establish a tradeoff between the secure channel rate (for a node pair) and the secure network rate (sum over all node pair rates) and show that information-theoretic secrecy can be achieved asymptotically if and only if the sum rate of any subset of unhacked channels does not exceed the shared unhacked-secret-bit rate of these channels. We also propose a practical scheme that achieves a good balance of network and channel rates with information-theoretic secrecy guarantee. This work has a wide range of potential applications for which strong secrecy is desired, such as cyber-physical systems, distributed-control systems, and ad-hoc networks. [ABSTRACT FROM AUTHOR]

The object of research is the military radio communication system. Effective operation of routing protocols is possible only if there is reliable information about the network topology for network nodes, given that the mobility of individual nodes is insignificant in special purpose wireless networks. Because nodes in the network demonstrate the mobility property of the node groups. This paper solves the problem of the analysis (decomposition) of methods of protocols efficiency increase of dynamic routing in telecommunication networks with a possibility to self-organization. In the course of the research, the authors used the main provisions of the queuing theory, the theory of automation, the theory of complex technical systems and general scientific methods of cognition, namely analysis and synthesis. This research analyzes various methods to increase the efficiency of dynamic routing protocols. Energy efficiency methods focus on three main components in energy management: battery management, transmission energy management and system energy management methods. Reliable multicast has become indispensable for the successful deployment of special purpose wireless networks, such as in tactical military operations and emergency operations. The results of the research will be useful in: – development of new routing algorithms; – substantiation of recommendations for improving the efficiency of the route selection process in networks with the possibility of self-organization; – analysis of the electronic situation during hostilities (operations); – while creating promising technologies to increase the efficiency of mobile radio networks. Areas of further research will focus on the development of a methodology for the operational management of interference protection of intelligent military radio communication systems. [ABSTRACT FROM AUTHOR]

The object of research is the military radio communication system. Effective operation of routing protocols is possible only if there is reliable information about the network topology for network nodes, given that the mobility of individual nodes is insignificant in special purpose wireless networks. Because nodes in the network demonstrate the mobility property of the node groups. This paper solves the problem of the analysis (decomposition) of methods of protocols efficiency increase of dynamic routing in telecommunication networks with a possibility to self-organization. In the course of the research, the authors used the main provisions of the queuing theory, the theory of automation, the theory of complex technical systems and general scientific methods of cognition, namely analysis and synthesis. This research analyzes various methods to increase the efficiency of dynamic routing protocols. Energy efficiency methods focus on three main components in energy management: battery management, transmission energy management and system energy management methods. Reliable multicast has become indispensable for the successful deployment of special purpose wireless networks, such as in tactical military operations and emergency operations. The results of the research will be useful in: – development of new routing algorithms; – substantiation of recommendations for improving the efficiency of the route selection process in networks with the possibility of self-organization; – analysis of the electronic situation during hostilities (operations); – while creating promising technologies to increase the efficiency of mobile radio networks. Areas of further research will focus on the development of a methodology for the operational management of interference protection of intelligent military radio communication systems. [ABSTRACT FROM AUTHOR]

Two-Way Ranging (TWR) is a widely used method for distance estimation in asynchronous wireless networks, but the deviation between the clocks can lead to errors in distance estimation. The ultra-wideband (UWB) technology provides the best accuracy in distance estimation, but total emission time is drastically limited by harmonized standards. Localization accuracy, latency and network scalability are key performance metrics in wireless location characterization. This article advances a new sequencing of the localization process, called Double-Beacon Two-Way Ranging (DB-TWR) algorithm, and presents the related time-of-flight (ToF) estimation formula, which is able to compensate for clock error and to reduce the localization period. The Fine Time Measurement (FTM) protocol, specified by the Wireless LAN (WLAN) standard, uses the TWR method and as a result the clock deviation leads to systematic errors in ToF estimation. The paper proposes two additional timestamp s captures and a new ToF computation formula which compensates for clock deviation. The article provides a theoretical analysis and extensive simulations of errors propagation in the ranging process, both as a mean and as an uncertainty, and proves that the designed algorithms cancel the clock offsets entirely. [ABSTRACT FROM AUTHOR]

Vehicular social networks (VSNs) are considered as an emerging class of vehicular ad hoc networks (VANETs) with social attributes. In contrast to the traditional randomly distributed human social networks, vehicles normally only move along fıxed paths. As such, information sharing and forwarding become challenging because of the high speed of vehicles, complicated propagation environment, and quickly changing network topologies. The social characteristics and human behavior features are used to improve the effıciency of information delivery among vehicles in VANETs. In this paper, we propose a dynamic periodic location encounter network (DPLEN) model that considering both time-varying and location-varying characteristics of vehicles. We calculate the line similarity for each encountered pair of vehicles based on the periodic time and location information of the encounter event, and analyze social attributes based on the network model, such as the Community structure, Betweenness Centrality and K-shell. We also use the similarity to design two routing protocols for unicast and multicast patterns. After testing the proposed model on empirically collected datasets of mobility traces, the results show that these two routing protocols are able to greatly improve the efficiency of information forwarding in the VSNs. [ABSTRACT FROM AUTHOR]

RGBT tracking has attracted increasing attention since RGB and thermal infrared data have strong complementary advantages, which could make trackers all-day and all-weather work. Existing works usually focus on extracting modality-shared or modality-specific information, but the potentials of these two cues are not well explored and exploited in RGBT tracking. In this paper, we propose a novel multi-adapter network to jointly perform modality-shared, modality-specific and instance-aware target representation learning for RGBT tracking. To this end, we design three kinds of adapters within an end-to-end deep learning framework. In specific, we use the modified VGG-M as the generality adapter to extract the modality-shared target representations. To extract the modality-specific features while reducing the computational complexity, we design a modality adapter, which adds a small block to the generality adapter in each layer and each modality in a parallel manner. Such a design could learn multilevel modality-specific representations with a modest number of parameters as the vast majority of parameters are shared with the generality adapter. We also design instance adapter to capture the appearance properties and temporal variations of a certain target. Moreover, to enhance the shared and specific features, we employ the loss of multiple kernel maximum mean discrepancy to measure the distribution divergence of different modal features and integrate it into each layer for more robust representation learning. Extensive experiments on two RGBT tracking benchmark datasets demonstrate the outstanding performance of the proposed tracker against the state-of-the-art methods. [ABSTRACT FROM AUTHOR]

In the last years, vehicular networking has grown up in terms of interest and transmission capability, due to the possibility of exploiting the distributed communication paradigm in a mobile scenario, where moving nodes are represented by vehicles. The different existing standards for vehicular ad-hoc networks, such as dedicate short range communication (DSRC), wireless access for vehicular environment (WAVE)/IEEE802.11p, have given to the research community the possibility of developing new medium access control (MAC) and routing schemes, in order to enhance the quality and the comfort of mobile users who are driving their vehicles. In this paper, we focus our attention on the optimization of traffic flowing in a vehicular environment with vehicle-2-roadside capability. As shown later, the proposed idea exploits the information that is gathered by road-side units to redirect traffic flows (in terms of vehicles) to less congested roads, with an overall system optimization, also in terms of carbon dioxide emissions reduction. An analytical model, as well as a set of pseudo-code instructions, have been introduced in the paper. A deep campaign of simulations has been carried out to give more effectiveness to our proposal. [ABSTRACT FROM AUTHOR]

In this paper, we consider a network reconstruction problem using unmanned aerial vehicles (UAVs) where stationary ad hoc networks are severely damaged in a post-disaster scenario. The main objective of this paper is to repair the network by supplementing aerial wireless links into the isolated ground network using UAVs. Our scheme performs network probing from the air and finds out crucial spots where both local and global routing performance can significantly be recovered if deployed. First, we propose a novel distributed coverage path planning algorithms with independent and computationally lightweight navigation based on adaptivezigzagpatterns. Second, we present route topology discovery schemes that capture both local andnon-local network connectivity by extracting inherent route skeletons via stitching partial local paths obtained from the simple packet probing by UAVs. Finally, we find the optimal UAV relay deployment positions that can improve network-wide data delivery most effectively based on three novel approaches of an optimization technique, an iterative heuristic algorithm, and a topology partitioning ofstrongly connected component. Simulation results demonstrate that our distributed traversing algorithms reduce the complete coverage time, the travel distance, and the duplicate coverage compared to other counterpart algorithms. Our deployment algorithms recover severely impaired routes, incurring reasonable computational overhead. [ABSTRACT FROM AUTHOR]

This paper examines a new application of the well-known ARP spoofing (or ARP cache poisoning) attack. Traditionally, ARP spoofing has been applied in local area networks to allow an attacker to achieve a man-in-the-middle position against target hosts, or to implement a denial-of-service by routing messages to non-existent hardware addresses. In this paper, we introduce a variant of ARP spoofing unique to multi-hop ad hoc networks in which routing loops are created among target wireless hosts. The routing loops not only results in a denial-of-service against the targeted hosts, but creates a resource consumption attack, where the targets waste power and occupy the channel, precluding its use by legitimate traffic. The paper identifies the network topology pre-conditions under which routing loops are possible, and discusses how ARP spoof messages can be used to create routing loops of arbitrary size. We show experimental results of an implementation and provide suggestions as to how to prevent, detect, or mitigate the attack. [ABSTRACT FROM AUTHOR]

For improving the throughput while simultaneously enhancing the security in aeronautical ad-hoc networking (AANET), a channel quality indicator (CQI)-mapped spatially modulated sparse code multiple access (SM-SCMA) scheme is proposed in this paper. On one hand, we exploit the joint benefits of spatial modulation and SCMA for boosting the data rate. On the other hand, a physical-layer secret key is generated by varying the SM-SCMA mapping patterns based on the instantaneous CQI in the desired link. This guarantees the security of AANETs, since this secret key is not exchanged between the source aeroplane and its destination. Due to the line-of-sight (LoS) propagation in the AANET, other aeroplanes or eavesdroppers may detect the signals delivered in the desired link. However, they are unable to translate the detected signals into the original confidential information, even if multiple copies of the signals are recoined over multiple hops of the AANET, because they have no knowledge of the CQI-based SM-SCMA mapping pattern. The performance of the CQI-mapped SM-SCMA is evaluated in terms of both its bit error rate and its ergodic secrecy rate, which substantiates that the proposed scheme secures the confidential information exchange in the multi-hop AANET. [ABSTRACT FROM AUTHOR]

Communications-based train control (CBTC) is a modern signaling system that uses radio communication to transfer train control information between the train and the wayside. A vast majority of CBTC systems worldwide use IEEE 802.11 Wi-Fi as the radio technology mostly due to its cost effectiveness. The trackside networks in these systems are mostly based on the conventional infrastructure Wi-Fi. It means a train has to continuously associate (i.e., perform handshake) with the trackside Wi-Fi access points (AP) as it moves. This is a time-consuming process associated with a certain delay. Additionally, these APs are connected to the wayside infrastructure via optical fiber cables that incurs huge costs. This paper presents a novel design in which trackside nodes function in ad-hoc Wi-Fi mode, which means no association has to be performed with them prior to transmitting. A train simply broadcasts packets to any nodes in its range. A node upon receiving these packets forwards them to the next node and so on, forming a chain of nodes. Following this chain, packets arrive at the destination. To make the design resilient against interference, transmissions are separated on multiple frequencies. Furthermore, redundancy is introduced in the design as a node forwards packets to not only one but two of its neighbors. This paper investigates the performance of the new design from the perspective of resiliency, redundancy, and scalability, and presents the results both from a field experiment carried out using prototype hardware and an extensive simulations study. [ABSTRACT FROM PUBLISHER]

With the technology of data storage and shared services in the cloud, users can easily share data or revoke from their groups. To ensure the accuracy of the shared data, the key is used for group users to calculate the authenticators of the shared data and audit the data's integrity remotely. However, high-speed mobile terminals have posed challenges to key management in Vehicle Ad-hoc networks (VANETs). Besides, to maintain the integrity of the shared data, the computation and communication overheads must be increased in the revocation process when a vehicle user is removed from a group. For such, a new shared data auditing scheme is proposed in this paper, which supports user revocation by combining the existing certificateless signcryption method with a fog architecture. This scheme improves the efficiency of auditing and user revocation since it reduces many time-consuming operations, as well as features such as public auditing, mutual authentication, efficient and secure revocation are presented. Security analysis and experimental results demonstrate that the proposed scheme is both correct and safe, has more comprehensive functions and better efficiency than other existing ones. [ABSTRACT FROM AUTHOR]

Smart, and green cities impose stringent requirements on spectral efficiency (SE), and energy efficiency (EE) of vehicular networks. For the current vehicular ad-hoc networks (VANETs), vehicle's mobility leads to rapid topology changes, and high channel uncertainty. However, clustering schemes for establishing stable clusters, and robust power control (RPC) combating with channel fluctuation are investigated independently. In this paper, joint clustering, and RPC schemes are proposed to optimize the SE, and EE of the involved VANETs. Via the same fixed-length slot, the synchronized interference constraints of cluster heads (CHs) are formed, and offer conditions for RPC. Due to the random channel fluctuations, all CHs’ synchronized interference constraints are formulated as probability constraints. Besides, a pricing-based utility which avoids the separate optimization between SE, and EE is introduced, and the price's impact on the tradeoff between them is involved. Since the probability constraints are intractable, and the unified utility is nonconvex, the Bernstein approximation, and successive convex approximation (SCA) are used to transform the problem into a tractable convex one. Through dual decomposition, two RPC algorithms are proposed to determine the optimal solutions for the fixed price C, and the optimal price C*, respectively. Numerical simulations are used to evaluate the algorithmic performances in high-dynamic system, and the results show that the proposed algorithms are effective. The validity of the clustering method, and the proposed RPC scheme is further verified by comparisons. [ABSTRACT FROM AUTHOR]

In recent years, the need for high security with reliability in the wireless network has tremendously been increased. To provide high security in reliable networks, mobile ad hoc networks (MANETs) play a top role, like open network boundary, distributed network, and fast and quick implementation. By expanding the technology, the MANET faces a number of security challenges due to self-configuration and maintenance capabilities. Besides, traditional security solutions for wired networks are ineffective and inefficient because of the nature of highly dynamic and resource-constrained MANETs. In this paper, the researchers focus on improving reliable data transmission with high security in the MANET using an optimization technique. In the proposed MANET system, the nodes are clustered by utilizing an energy-efficient routing protocol. Then, the modified discrete particle swarm optimization is used to select the optimal cluster head. A secured routing protocol and a signcryption model can be used to improve the transmission security of the reliable MANET. The signcryption algorithm encrypts the digital signature, which can enhance the overall efficiency and confidentiality. The security-based analysis is performed on the basis of packet delivery ratio, energy consumption, network lifetime, and throughput. Finally, the result demonstrates that the MANET with optimization techniques achieves a high transmission rate and improves the reliable data security. [ABSTRACT FROM AUTHOR]

Due to the requirement of real time controlling on the vehicular ad-hoc networks (VANETs), the security measure should be fast, lightweight, and strong. In this paper, we investigate the secure communication between the on-board unit and the roadside unit which has strong computing ability to remedy the insufficient computing power of on-board unit. The novel schemes are developed to guarantee both security and energy harvest. Specifically, a muti-antenna roadside unit (PT) conveys a secret message to a muti-antenna primary on-board unit (PR) intercepted by multiple muti-antenna adversaries (Eves). Simultaneously, a secondary roadside unit (ST) adopts simultaneous wireless information and power transfer (SWIPT) strategy to send secret-free data embeded with energy-carrying artificial noise (AN) to its service subscriber (SR), by which secrecy guarantee is provided for the primary on-board unit and the quality of service (QoS) is satisfied, i.e., data traffic and harvested energy. Technically, considering the secondary link's data transmission rate, harvested energy, and transmit power, we propose joint power allocation designs for the nonconvex secrecy rate maximization (SRM) problems under either perfect channel state information (CSI) or norm-bounded channel uncertainty model. Simulation results show that the proposed secondary link-aided secrecy designs can achieve better performance in terms of secrecy rate and energy efficiency. [ABSTRACT FROM AUTHOR]

The performance of existing coded caching schemes is sensitive to the worst channel quality, a problem which is exacerbated when communicating over fading channels. In this paper, we address this limitation in the following manner: in short-term, we allow transmissions to subsets of users with good channel quality, avoiding users with fades, while in long-term we ensure fairness among users. Our online scheme combines (i) the classical decentralized coded caching scheme with (ii) joint scheduling and power control for the fading broadcast channel, as well as (iii) congestion control for ensuring the optimal long-term average performance. We prove that our online delivery scheme maximizes the alpha-fair utility among all schemes restricted to decentralized placement. By tuning the value of alpha, the proposed scheme can achieve different operating points on the average delivery rate region and tune performance according to an operator’s choice. We demonstrate via simulations that our scheme outperforms two baseline schemes: (a) standard coded caching with multicast transmission, limited by the worst channel user yet exploiting the global caching gain; (b) opportunistic scheduling with unicast transmissions exploiting the fading diversity but limited to local caching gain. [ABSTRACT FROM AUTHOR]

The ad hoc network is an emerging wireless communication technology. Recently, the reliability of ad hoc networks has attracted increasing attention in the literature. In this paper, the reliability of such networks is analyzed by incorporating the impacts of node failures and interference, because node failures usually obstruct the achievement of the intended function of a network, and interference is a key factor that degenerates the communication quality. We consider a general case that an ad hoc network is functional if at least k arbitrary nodes are operational and connected. Accordingly, two novel reliability indices, the generalized k-terminal reliability and the average generalized k-terminal reliability, are proposed, and their calculation methods are provided based on the Laplace transformation technique and the graph theory. For optimizing the design of an ad hoc network, a multiobjective optimization problem is investigated to maximize the reliability level and minimize the cost. The optimization problem is handled by the weighted sum method, and the most suitable solution is selected by the fuzzy satisfying approach. Finally, a numerical example is given to demonstrate the application of the proposed methods. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The proliferation of radio-enabled equipment, including sensors, controllers, actuators, mobile handhelds, etc., into the today's heterogeneous wireless network (HWN) has led to the support of different vertical services on-top of the same physical infrastructure. Such an approach increases the potential for enhanced multiplexing gains due to the joint utilization of multiple network tiers and their resources. However, it also links the availability of new services to the robustness of the HWN infrastructure against malicious attacks. In this paper, we study the impact of two prominent denial of service (DoS) attacks, the jamming and the black hole attack, on network coverage of multi-tier HWNs. In particular, we consider a HWN model of multiple tiers, where the locations of nodes belonging to each tier are modeled by a homogeneous Poisson point process (PPP) with known intensity. Each tier consists of regular nodes, jammers (disrupting downlink communications by transmitting at constant power), and black holes (appearing as regular nodes but without forwarding received packets to their legitimate destination). The type of a node for a given network tier is determined by a prescribed probability, whereas jammer and black hole nodes are considered to act independently from each other. We further focus on the challenging scenario where end users can access a limited number of network tiers, while we also allow different tiers to potentially utilize different spectrum bands. Assuming that successful service reception from a node belonging to a given network tier requires a minimum received signal quality threshold to be attained, we derive exact expressions and performance bounds on the coverage probability of random multi-tier HWNs with joint jamming and black hole attacks, which depend on the capability of network nodes to detect and avoid association with malicious nodes (i.e., jammers or black holes). Detailed numerical results highlight the usefulness of the proposed analysis, providing valuable insights on system design and parameterization towards enhanced network robustness. [ABSTRACT FROM AUTHOR]

Generally, the ad hoc networks work correctly only if all nodes cooperate in the routing and forwarding of the packets. However, in some cases, selfish nodes are hesitated to share the resources with their neighbors and attempt to preserve their own assets, since splitting nodes into two distinct groups including absolute cooperator and absolute selfish and avoiding the selfish nodes group in network activities will be degraded network quality of service. In this paper, we propose a novel fuzzy-based selfish node detection approach for ad hoc networks that operates based on the social network principles. In the social-based proposed approach, the nodes' status will be determined by three variables, i.e., hop count (H.C.), residual energy (Re-En.), and cooperation history (Co-h.), through fuzzy interface process to prevent the isolating of the likely selfish nodes from the network and maintain more active node in the network as possible. The MobEmu tool is used to evaluate the effectiveness of the proposed approach in terms of the hit rate, delivery latency, delivery cost, and average hop count. The simulation results reveal that the proposed approach has a significant improvement in contrast to counterparts using UPB 2011 and UPB 2012 traces. [ABSTRACT FROM AUTHOR]

In this paper, we focus on one of the key technologies for the fifth-generation wireless communication networks, massive multiple-input-multiple-output (mMIMO), by investigating two of its most relevant architectures: 1) to provide in-band backhaul for the ultra-dense network (UDN) of self-backhauled small cells (SCs), and 2) to provide direct access (DA) to user equipments (UEs). Through comprehensive 3GPP-based system-level simulations and analytical formulations, we show the end-to-end UE rates achievable with these two architectures. Differently from the existing works, we provide results for two strategies of self-backhauled SC deployments, namely random and ad-hoc, where in the latter SCs are purposely positioned close to UEs to achieve line-of-sight (LoS) access links. We also evaluate the optimal backhaul and access time resource partition due to the in-band self-backhauling (s-BH) operations. Our results show that the ad-hoc deployment of self-backhauled SCs closer to the UEs with optimal resource partition and with directive antenna patterns, provides rate improvements for cell-edge UEs that amount to ${30\%}$ and tenfold gain, as compared to mMIMO DA architecture with pilot reuse 3 and reuse 1, respectively. On the other hand, mMIMO s-BH underperforms mMIMO DA above the median value of the UE rates when the effect of pilot contamination is less severe, and the LoS probability of the DA links improves. [ABSTRACT FROM AUTHOR]

Wireless sensor networks (WSNs) are made of spatially distributed autonomous sensors, which cooperate to monitor physical or environmental parameters and to deliver such data to one or more data sinks. A promising field of application of WSNs is planetary exploration, characterized by a continuous monitoring of the surface to have clear notion of planet conditions and prepare for future manned missions. The potentially large size of the region to be monitored and the line-of-sight limitations (as, for instance, on the Moon, which is the case study discussed in the paper) hamper the possibility of having 1-hop sensor-sink communications. Therefore, to allow sensed data to reach the sink(s), the sensors must be able to create and maintain a multi-hop ad hoc network. This paper proposes an ad hoc routing algorithm applicable to WSNs for planetary exploration, aiming at (i) assuring any-cast communications with multiple data sinks, (ii) minimizing the control overhead for routing maintenance, (iii) being light in terms of memory/computational requirements, to be installed into low-power and low-memory/processing devices, (iv) being rapid to reconfigure in the presence of node failures and (v) optimizing the choice of the paths, to achieve energy balancing and saving. Extensive simulations show the efficiency of the proposed approach. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In a mobile radio-frequency identification (RFID) system, tagged items enter and leave the reader’s field at a constant speed. The possibility of tags leaving the reader’s interrogation zone without being identified is known as tag loss. Minimizing the tag loss ratio in the presence of random denial-of-service (DoS) attacking signals by optimizing the number of frames is investigated in this paper. The results show that the number of frame control is not needed to reduce the tag loss ratio if the tag entering rate is below a critical limit. The number of frames has to abruptly reduce to keep the tag loss ratio lower if the tag entering rate exceeds that critical limit. This critical limit of the tag entering rate is derived analytically. An analytical solution of the optimum number of frames in the presence of attacking signals that also minimize the tag loss ratio is devised. The technique for setting the optimum number of frames is also presented. The presented results in this paper with random DoS attacking signals is so general that those can be converted without DoS attacking signals by setting the DoS attacking signals equal to zero. The results of this paper can be used for mobile RFID system design with and without DoS attacking signals. [ABSTRACT FROM AUTHOR]

The increasing use of shared, unlicensed spectrum bands by medical devices and nonmedical products highlights the need to address wireless coexistence to ensure medical device safety and effectiveness. This paper provides the first step to approximate the probability of a device coexisting in its intended environment by providing a generalized framework for modeling the environment. The application of this framework is shown through an 84-day spectrum survey of the 2.4–2.48 GHz industrial, scientific, and medical band in a hospital environment in the United States. A custom platform was used to monitor power flux spectral density and record received power. Channel utilization of three nonoverlapping channels of 20 MHz bandwidth—relative to IEEE 802.11 channels 1, 6, and 11—were calculated and fitted to a generalized extreme value distribution. Low channel utilization was observed ( $ <$10%) in the surveyed environment with sporadic occurrences of higher channel utilization ($ >$ 50%). Reported findings can be complementary to wireless coexistence testing. This paper can provide input to the development of a consensus standard for wireless device coexistence test methods and a consensus document focused on wireless medical device coexistence risk management. [ABSTRACT FROM PUBLISHER]

Vehicular ad hoc networks (VANETs) experience large-scale high-speed mobility and volatile topology. VANETs may therefore experience intermittent connections and may occasionally be unable to guarantee end-to-end connections. This gives the medium access control (MAC) layer the opportunity to adapt its transmission strategy to the current unstable wireless connections to improve transmission efficiency. In this paper, we propose an adaptive frame length aggregation scheme (AFLAS) for VANETs, which is designed to improve transmission efficiency and increase data throughput. In our scheme, the incoming data packets from higher layers are queued separately in the MAC layer to wait for transmission opportunities. Suitable aggregation frame lengths are calculated according to the current wireless status and applied in the MAC layer at the onset of data transmissions. In this paper, we analyze and apply our AFLAS strategy to two current frame aggregation schemes in IEEE 802.11. We also report on the performance evaluation of our scheme. Our results exhibit significant improvement results in data throughput, retransmissions, overheads, and transmission efficiency in comparison with nonadaptive aggregation schemes. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

This paper presents a systematic approach for solving wireless max–min utility fairness optimization problems in multiuser wireless networks with general monotonic constraints. These problems are often challenging to solve due to their nonconvexity. By establishing a connection between this class of optimization problems and the class of conditional eigenvalue problems that can be addressed by a generalized nonlinear Perron–Frobenius theory, we show how these problems can be solved optimally using an iterative algorithm that converges geometrically fast. The mathematical development in this paper unifies previous work and allows us to handle a broader class of competitive utility functions with general nonlinear monotonic constraints. Several representative applications illustrate the effectiveness of the proposed framework, including the max–min quality-of-service subject to robust interference temperature constraints in cognitive radio networks, the min–max weighted mean-square error subject to signal-to-interference-and-noise ratio constraints in multiuser downlink systems, the max–min throughput subject to nonlinear power constraints in energyefficient wireless networks, the max–min sigmoid utility in multimedia wireless networks, and the min–max outage probability subject to outage constraints in heterogeneous wireless networks. Numerical results are presented to demonstrate the fast-convergence behavior of the algorithms to the optimal fixed-point solution characterized by our generalized nonlinear Perron–Frobenius theoretic framework. [ABSTRACT FROM PUBLISHER]

Electromagnetic spectrum resources are a very important resource. With the rapid development of radio technology, electromagnetic spectrum resources have become scarce. Abuse of spectrum resources and interference with primary user often occur. Pre-sensing the electromagnetic environment and performing dynamic spectrum access is the direction of future wireless technology development. This paper focuses on the electromagnetic spectrum information service platform. We design a spectrum detection node in combination with an embedded system. The distributed spectrum detection network is constructed by using the TV White Space as the communication frequency band of the backbone network. From the perspective of signal source, research on detection and identification methods based on radio signal characteristics improves the efficiency of electromagnetic spectrum detection. A phase extreme range estimation method based on radio frequency I/Q data is proposed to improve signal estimation accuracy in a low signal-noise-ratio environment. The interquartile range is proposed to distinguish noise and signal. The experiment results show that distributed electromagnetic spectrum information service platform based on signal characteristics can improve detection accuracy and increase system flexibility. [ABSTRACT FROM AUTHOR]

The problem of routing security in vehicular ad hoc networks has become a major concern for researchers. Compared with cryptography-based solutions, trust-based solutions are considered to be more acceptable as a promising approach, which mainly define two operations: trust computing and security application. In this paper we first study trust properties and construct a novel trust inference model, where two trust attributes named subjective trust and recommendation trust, are selected to quantify the trust level of a specific vehicle. The SCGM(1,1)-weighted Markov prediction algorithm based on fluctuation recognition is utilized to calculate the subjective trust accurately, meanwhile a new evaluation method of recommendation credibility based on the feedback mechanism is introduced for the calculation of recommendation trust. We subsequently exploit the advantages of mesh structure and design a light-weight trust-aware multicast routing protocol (i.e., LTMRP), which can establish secure and reliable communication paths by selecting trusted relay vehicles. To further improve the routing efficiency, two mechanisms including forwarding nodes reuse mechanism and trust-aware route handoff mechanism are proposed. Simulation verification and comparison of the relevant trust models and trust-based protocols are accomplished by three simulation platforms (i.e., Netlogo, SUMO, and NS-2).The convincing results show that our trust model obtains strong resistibility to multiple malicious attacks. Moreover, examined in four routing metrics, the experimental results indicate that LTMRP performs better than the other relevant protocols. [ABSTRACT FROM AUTHOR]

A key factor limiting the democratisation of networked systems is the lack of trust, particularly in the wake of data-intensive applications that work on sensitive and private data, which requires providing strong network security guarantees via encryption and authentication algorithms, as well as rethinking algorithms to compute on the network peripheries without moving data. In many security and privacycritical domains such as Home Automation IoT networks, AUV networks etc., the existence of a centralized privileged node leads to a vulnerability for leakage of sensitive information. In this paper, we have proposed a decentralized networking architecture that adopts collaborative processing techniques and operates within the tradeoff between network security and performance. We have investigated the design and sustainability of autonomous decentralized systems and evaluated the efficiency of the proposed scheme with the help of extensive simulation tools. [ABSTRACT FROM AUTHOR]

As network resources are shared between many users, resource management must be a key part of any communication system as it is needed to provide seamless communication and to ensure that applications and servers receive their required Quality-of-Service. However, mobile environments also need to consider handover issues. Furthermore, in a highly mobile environment, traditional reactive approaches to handover are inadequate and thus proactive techniques have been investigated. Recent research in proactive handover techniques defined two key parameters: Time Before Handover (TBH) and Network Dwell Time (NDT) for a mobile node in any given networking topology. Using this approach, it is possible to enhance resource management in common networks using probabilistic mechanisms because it is possible to express contention for resources in terms of No Contention, Partial Contention, and Full Contention. This proactive approach is further enhanced by the use of a contention queue to detect contention between incoming requests and those waiting for service. This paper therefore presents a new methodology to support proactive resource allocation for future networks such as Vehicular Ad-Hoc Networks. The proposed approach has been applied to a vehicular testbed and results are presented that show that this approach can improve overall network performance in mobile heterogeneous environments. [ABSTRACT FROM AUTHOR]

This paper studies the asymptotic properties of average area spectral efficiency (ASE) of a downlink cellular network in the limit of very dense base station (BS) and user densities. This asymptotic analysis relies on three assumptions: 1) interference is treated as noise; 2) the BS locations are drawn from a Poisson point process; and 3) the path loss function is bounded above satisfying mild regularity conditions. We consider three possible definitions of the average ASE, all of which give units of bits per second per unit bandwidth per unit area. When there is no constraint on the minimum operational signal-to-interference-plus-noise ratio (SINR) and instantaneous full channel state information (CSI) is available at the transmitter, the average ASE is proven to saturate to a constant, which we derive in a closed form. For the other two ASE definitions, wherein either a minimum SINR is enforced or CSI is not available, the average ASE is instead shown to collapse to zero at high BS density. We provide several familiar case studies for the class of considered path loss models, and demonstrate that our results cover most previous models and results on ultradense networks as special cases. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the request routing delay of opportunistic routing for cache-enabled wireless networks considering uncorrelated and temporally correlated wireless channels. We model wireless channel variation at different time scales via two approaches: an abstract modeling approach where we model the variation considering Rayleigh fading and shadowing channel models and an empirical approach where the variation is modeled directly using signal strength measurements. We develop Markovian models to analyze the performance of opportunistic forwarding, leverage the wireless channel models to determine the packet transmission success probabilities and then utilize them to obtain the request routing delay. We first perform numerical experiments and simulations considering Rayleigh fading and shadowing channel models and then conduct a trace-based evaluation using signal strength measurements collected over a wireless sensor network testbed. Our experiments demonstrate the validity and effectiveness of our Markovian model in determining the request routing delay in real-world settings. Our work takes a step forward in providing network operators a tool for analyzing network performance before deploying their networks. [ABSTRACT FROM AUTHOR]

The design of an efficient medium access control (MAC) protocol for multichannel ad hoc cognitive radio networks is an important problem and has been the topic of extensive recent research. In this paper, we present the design and performance evaluation of a protocol, group MAC (GMAC), which is customized for a situation that commonly arises in ad hoc networks: The network consists of multiple groups of nodes such that a large fraction of the traffic of each node needs to be sent to other nodes of its own group. Some examples are 1) units (e.g., platoons) in a military ad hoc network; 2) divisions in an emergency or disaster relief network; and 3) departments in a corporate or university network. Our protocol requires each secondary node to have only one narrowband transceiver, does not rely on a control channel, and incorporates a novel technique for dynamically balancing the traffic load of secondary nodes across the set of free channels. We formulate the problem of partitioning the network nodes into groups based on the volumes of data traffic to be sent between different pairs of nodes, which we call the group formation problem (GFP). We show that the GFP is NP-complete and propose a greedy algorithm to solve it. We analyze the stability region of the GMAC protocol using a queuing theoretic framework. Our extensive simulations show that a large fraction of the bandwidth unoccupied by primary users is utilized by the GMAC protocol for data transmissions. [ABSTRACT FROM AUTHOR]

As a vital component of disaster response and relief, a wireless network needs to be rapidly deployed after a disaster strikes. Due to the advantages of large area coverage, low capital cost, and fast deployment, an unmanned aerial vehicle (UAV) is believed to be a potentially promising choice to recover wireless communication in post-disaster environments. In this paper, the performance gains of utilizing two cooperative UAVs for downlink transmission over a large number of emergency response rescue vehicles on the ground in post-disaster areas are explored. Toward this end, the concept of average channel access delay for a generic vehicle to establish a full transmission to an UAV is introduced, i.e., data packets are said to be successfully transmitted from a UAV to a vehicle only if the time duration for the vehicle covered by the UAV is greater than the specified average channel access delay. Based on the proposed concept, a stochastic geometry based mathematical framework to analyze the coverage probability and average achievable rate for a multi-UAV-assisted downlink network, where vehicles connect to the Internet via satellites in a two-hop manner, is presented. According to the derived closed-form solutions for the network performance metrics, extensive numerical results are provided to illustrate the network performance gains brought by UAVs. Additionally, optimal settings are also presented for network designers to efficiently determine the optimal network parameters so as to achieve the optimum network performances in post-disaster areas. [ABSTRACT FROM AUTHOR]

This paper studies finding the secure path according to the secrecy connectivity probability (SCP) in the multihop ad hoc networks in the presence of inhomogeneous eavesdropper clusters. We consider both random and fixed eavesdropper clusters, where the former case assumes that there is no knowledge of the locations of the clusters and the latter case assumes that the locations of the clusters can be estimated accurately. First, we derive the end-to-end SCP to characterize the secrecy performance of a given path in a general multihop wireless network with half-duplex randomize-and-forward relaying. Then, we consider a full-duplex scheme at the legitimate receiver, which receives the useful information while broadcasting a jamming signal to the potential eavesdroppers to further enhance the secrecy connectivity. Then, a novel secure routing algorithm that can provide the maximum SCP for any legitimate transmitter/receiver pair in a distributed manner is proposed. The theoretical analysis is verified by Monte Carlo simulation results. The results show that our secure routing algorithm provides similar results compared to an exhaustive search. For the random eavesdropper cluster case, the optimal route is independent of the knowledge of the cluster, which is the same as the homogeneous eavesdropper case. However, for the case where eavesdropper clusters are fixed and their locations are knowna priori, the optimal path selection depends on the radii and locations of the eavesdropper clusters and the average number of eavesdroppers in each cluster. [ABSTRACT FROM AUTHOR]