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In this paper, we consider a cooperative simultaneous wireless information and power transfer (SWIPT) network with one source–destination pair and multiple energy harvesting relays. How to efficiently use these relays has been addressed in conventional cooperative networks, and this paper investigates the impact of SWIPT on the performance of such multirelay cooperative networks. In particular, the main contribution of this paper is that a closed-form expression of the outage probability achieved by the multirelay cooperative protocol is obtained, as well as its approximation at high SNR. In addition, the performance of the cooperative network with the SWIPT relays is compared with that in conventional systems with self-powered relays. [ABSTRACT FROM PUBLISHER]

The intelligent radio is a novel emerging paradigm catching on in many practical applications, in order to provide context awareness techniques, able to learn by the environment conditions applying machine learning frameworks. The channel state information (CSI) prediction is one of the main challenges that an intelligent radio has to face with. This paper deals with the CSI prediction in the case of a buffer aided relaying communication scheme with adaptive link selection previously proposed in the literature where a direct source-destination link is not available and with both links affected by an independent fading. In particular, the CSI prediction has been reduced here to a time series prediction problem, performed by involving the usage of the recurrent neural networks. Finally, the validation of the effectiveness of the proposed intelligent radio buffer-aided relaying scheme with adaptive link selection approach has been pursued by presenting performance comparisons with the previously proposed scheme under the assumption of an ideal and actual CSI estimations, respectively. [ABSTRACT FROM AUTHOR]

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]

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]

This paper studies and analyzes the performance of the licensed-assisted access (LAA) scheme introduced by 3GPP in LTE Release 13, and adopted by 3GPP in LTE Release 14, which is called 3GPP LAA scheme for short. Considering the characteristics that the 3GPP LAA scheme is different from other LAA schemes and IEEE 802.11 distributed coordination function (DCF) protocol in WiFi systems, the 3GPP LAA scheme is modeled as a new two-dimensional discrete Markov model, and the collision probability and the channel occupancy utilization are further derived based on the proposed model. To more deeply analyze the performance of the 3GPP LAA scheme by comparisons, we also derive the expressions of the same performance indices for the linear backoff based LAA scheme proposed in this paper and the fixed contention window based LAA scheme mentioned in existing literatures. The simulation and numerical results prove the validity of the proposed Markov chain model, and also show that the 3GPP LAA scheme is the friendliest one to WiFi networks among the three LAA schemes, whereas its total channel occupancy utilization is the lowest when the number of LAA small base stations (SBSs) is little and that is the highest when large. However, the other two LAA schemes are still the graceful coexistence, which is defined as the scheme where the interference to WiFi users caused by LAA SBSs coexisting with them is not more than that caused by other WiFi APs replacing the LAA SBSs. [ABSTRACT FROM AUTHOR]

This paper presents a non-orthogonal multiple access (NOMA)-assisted full-duplex (FD) cooperative spectrum sharing protocol to achieve full-rate at a cell-edge primary user, where the secondary receiver helps the primary network relay the information to the cell-edge primary user. Unlike other FD cooperative schemes, the FD relay in the proposed system is not transmitting while receiving symbols from the primary transmitter. Hence, the proposed scheme can achieve full-rate at a primary user without degrading its outage performance. Further, it guarantees every alternate time-slots to the secondary network for accessing the licensed spectrum by employing a secondary receiver as a cooperative relay. In this paper, we derive the analytical expression for the outage probability and ergodic capacity. Moreover, we validate the derived expression through simulation and asymptotic results. The numerical and simulation results substantiate that the proposed scheme significantly outperforms other existing protocols. [ABSTRACT FROM AUTHOR]

In this paper, we investigate a two-hop simultaneous wireless information and power transfer (SWIPT) amplify-and-forward (AF) multiple-input multiple-output (MIMO) relay communication system with an energy-limited relay node. The relay node harvests energy based on the radio-frequency (RF) signal transmitted from the source node through the time-switching (TS) protocol and fully uses the harvested energy to precode and forward the information to the destination node. The non-linear energy harvesting models are considered at the relay node. With the consideration of the channel estimation error, the joint optimization of the TS factor, source and relay precoding matrices is proposed with robustness against the channel state information (CSI) mismatch to maximize the mutual information (MI) between the source and destination nodes. The optimal structure for the source and relay precoding matrices is derived to simplify the transceiver optimization problem. Numerical simulations show that the system performance provided by the proposed algorithms with robustness is better than the non-robust algorithm. [ABSTRACT FROM AUTHOR]

The work presented in this paper describes a multi-issue negotiation protocol between active consumers and a management platform in order to establish load coordination in a highly congested network. The multi-issue negotiation protocol considers simultaneously the consumption interval, the price, and the size of the energy packages, which is the main contribution of this work. Regarding the implementation methodology, the proposed algorithms have been implemented using MATLAB classes that allow emulating the behaviour of a multi-agent system in which each vehicle is an agent that interacts with the platform, which is another agent. In the present work, and without loss of generality, the algorithm is applied to coordinate the charging of electric vehicles (EVs) in a distribution network in which building loads represent critical loads. The algorithm is tested in a realistic environment, and its stability and performance are evaluated. Furthermore, the description of the algorithm is provided in a generic form, and it could be applied to any other scenario. [ABSTRACT FROM AUTHOR]

This paper presents the overall framework for high-performance vehicle streams that integrates the transportation and the communication layered architectures together. It shows the process in establishing an infrastructure for high-performance vehicles and the theoretical development and deployment of cooperative adaptive cruise control (CACC) for heterogeneous vehicles that is integrated with lateral control. The system is designed to be fault tolerant and uses the concept of subplatoons. Our framework is based on integrating a transportation layered architecture with the Wireless Access in Vehicular Environment (WAVE) communication protocol. [ABSTRACT FROM PUBLISHER]

In this paper, the scaling law of the network throughput of a special type of heterogeneous networks is studied, where a secondary network composed of cognitive users shares the same resources opportunistically with a primary network of licensed users. Some pioneering works in this area showed that this type of heterogeneous networks performs as well as two stand-alone networks under the dense network model. A key assumption behind this conclusion is that the density of the secondary network is higher than that of the primary network in the order sense, which essentially decouples the two overlaid networks as the secondary network dominates asymptotically. In this paper, we endeavor to investigate this problem with a weaker condition that the dimensions of the two overlaid networks are on the same order, under the extended network model. Our analysis shows that, with the ratio of the two network sizes larger than a threshold, this weaker (and arguably more practical) condition does not degrade either network throughput scaling. Our result further reveals the potential of cognitive radio (CR) technology in real applications. [ABSTRACT FROM PUBLISHER]

Assuming noisy feedback channels, this paper investigates the data transmission efficiency and robustness of different automatic repeat request (ARQ) schemes using adaptive power allocation. Considering different block-fading channel assumptions, the long-term throughput, the delay-limited throughput, the outage probability, and the feedback load of different ARQ protocols are studied. A closed-form expression for the power-limited throughput optimization problem is obtained, which is valid for different ARQ protocols and feedback channel conditions. Furthermore, the paper presents numerical investigations on the robustness of different ARQ protocols to feedback errors. It is shown that many analytical assertions about the ARQ protocols are valid both when the channel remains fixed during all retransmission rounds and when it (in)dependently changes in each round. As demonstrated, optimal power allocation is crucial for the performance of noisy ARQ schemes when the goal is to minimize the outage probability. [ABSTRACT FROM PUBLISHER]

Vehicular ad hoc networks (VANETs) are wireless self-organizing networks, whose communication is conducted through open wireless channels, thus making it vulnerable to various attacks. It is therefore necessary to employ encryption technology to ensure secure communication. In view of the foregoing, key agreement techniques are introduced to VANET communications. The group key agreement (GKA) protocol allows a group of participants to establish a public session key for a secure communication channel over an insecure network. The traditional GKA protocol is inefficient, however, and consumes considerable amounts of resources. With the aim of resolving problems related to information security and privacy preservation in VANETs, this paper proposes a full session key agreement scheme based on chaos mapping. In this paper, the first phase describes the key agreement between the fog server and group administrator; the second phase describes the group key agreement for vehicle nodes in the group where the vehicle can only communicate with vehicles having the same group key without the aid of a trusted key center or centralized key distributor. The proposed scheme is based on Chebyshev chaotic mapping algorithm, in which a chaotic map is utilized to provide a one-way hash; Chebyshev polynomial is also employed to establish a public multi-party key; it avoids the modular multiplication index or scalar multiplication on the elliptic curve. The proposed scheme does not only satisfy the security requirements in VANETs but also performs detailed analysis. [ABSTRACT FROM AUTHOR]

The time synchronization in vehicular ad hoc networks (VANETs) has gained significant attention in recent times. In this paper, we focus on the time synchronization in large-scale VANETs and propose an adaptive beacon time synchronization (ABTS) algorithm to enhance timing message synchronization. ABTS algorithm selects the best time synchronization pairs to decrease the number of timing messages transmitted. To guarantee the reliability of synchronization, the clock offset of the connected vehicles periodically readjust to provide a better degree of synchronization accuracy with minimum energy consumption. Based on two-way timing message synchronization, we derive maximum likelihood (ML) estimation and its equivalent Cramer-Rao lower bound (CRLB) for clock offset design in the generalized sender-to-receiver system by assuming a Gaussian noise model. We propose node pair selection algorithms to improve pairwise beacon message timing synchronization. The simulation results validate that our proposed ABTS algorithm performs better than other protocols in terms of synchronization accuracy, the rate of convergence and energy efficiency. [ABSTRACT FROM AUTHOR]

In a cognitive radio network (CRN), two nodes have a rendezvous when they tune to the same channel simultaneously. Providing rendezvous guarantee between any pair of nodes is essential because a rendezvous is necessary for communication. Some existing works claim that rendezvous guarantee can be provided by using a dedicated common control channel to negotiate the channel being used. A serious problem of these mechanisms is that a globally available channel may not exist. Some channel hopping protocols try to provide a rendezvous guarantee without using a common control channel. However, these solutions may suffer from a poor number of rendezvous or uneven channel utilization. In this paper, we propose a novel distributed channel hopping protocol: Quorum and Latin square channel hopping (QLCH). The QLCH scheme efficiently provides rendezvous guarantee by utilizing the concept of quorum systems and Latin squares. The former is utilized to guarantee balanced rendezvous among nodes, whereas the latter is adopted to share the rendezvous among channels. QLCH efficiently provides fast rendezvous guarantee and can cooperate with other channel hopping protocols to enhance network throughput. Analytical and simulation results verify the improvement of QLCH. For example, when there are 30 flows using 11 channels in a CRN, the achieved time to rendezvous of QLCH is 9.84 times lower than that of the existing protocol SYNC-ETCH, whereas the achieved network throughput of QLCH is 362% higher than that of the existing protocol, i.e., Quorum-based channel hopping (L-QCH). [ABSTRACT FROM PUBLISHER]

Free-space optics (FSO)-based, low-earth orbit (LEO) satellite-assisted Internet of vehicles (IoVs) has recently attracted research efforts worldwide. For the majority of Internet applications, transmission control protocol (TCP) is one of the most widely deployed protocols. Nevertheless, a complete understanding of the TCP performance over FSO-based satellite-assisted IoVs networks is still lacking in the literature. This is a highly challenging issue, as a consequence of the non-trivial interdependencies between transmission losses caused by the dynamics/uncertainty of atmospheric last-mile channels and the buffer overflows on the Internet, as well as their joint impact on the TCP congestion control mechanisms. This paper offers a comprehensive analytical framework that allows assessing the TCP throughput performance under the joint impact of congestion losses occurred in the Internet and transmission errors at the last-mile link from the satellite-to-vehicle. Internet access for emerging unmanned aerial vehicles (UAVs) is considered while the analysis can be also applied to other kinds of vehicles, which, in fact, require simpler channel models. The link-layer incremental redundancy hybrid automatic repeat request (IR-HARQ) protocol is employed at satellite-to-UAV channels to further improve the TCP throughput performance. Numerical results provide non-trivial findings and insights for the TCP performance in satellite/FSO-based IoVs, in which optimal UAV’s parameters are chosen to maximize the TCP throughput. [ABSTRACT FROM AUTHOR]

Economical and environmentally friendly geocast (EEFG) uses traffic signals to communicate with approaching vehicles. The communication can be signal-to-vehicle (TLS2V) and vehicle-to-vehicle (V2V). Based on the information sent, the vehicle receiving the message adapts its speed to a recommended speed (SR ) , which helps the vehicle reduce fuel consumption and emissions. Our previous paper entitled “Optimization of Fuel Cost and Emissions Using V2V Communications” develops a model to determine the optimum SR . It also proposes heuristic expressions to compute the optimum or near-optimum SR. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel analytical approach to the analysis of the queuing delay and medium access distribution of carrier sense multiple access with collision avoidance (CSMA-CA) protocols over multihop personal area networks (MPANs). The proposed approach considers a general case without restrictions on the topology, traffic generation patterns, or multipath routing policy, and it accounts for heterogeneous traffic patterns, all possible packet loss scenarios, and the effect of the length of the backoff on the channel assessment. This paper uses statistical theorems to derive the moment generating function (mgf) of the time required to service a packet and then uses this function as a service distribution in a GI/G/1 queuing model to derive the interdeparture and total queuing delays. From these functions, the end-to-end delay, jitter, throughput, and failure transmission probability over a path are derived. In addition to determining these metrics, this paper exploits the statistical features of the mgf to determine the rare-event probability of the service function. The proposed approach is exemplified using the state-of-the-art IEEE 802.15.4 CSMA-CA protocol, and its accuracy is demonstrated through comparison with simulations. [ABSTRACT FROM PUBLISHER]

In this paper, we design a novel estimate-and-forward (EF) protocol in multiple-access relay channels (MARCs) where two correlated sources transmit their information to the common destination with the help of a relay. With the application of network coding (NC) at the relay, the network-coded soft symbols contain redundant information due to the correlated sources, which can be compressed before being forwarded. Specifically, we first derive the value of the network-coded soft symbol by considering the correlation of the two sources. Due to this correlation, the majority of soft symbol values are close to one. Then, we convert network-coded soft symbol vector into a sparse vector, which is suitable for compression by using the compressive sensing (CS). Next, we analyze the performance of the proposed EF protocol by comparing the soft symbol value and received signal-to-noise ratio (SNR) with the conventional EF protocol. Simulations show that our protocol can achieve the same bit error rate (BER) as the conventional EF protocol with proper compression rates, and it consumes much less transmission time due to the compression. [ABSTRACT FROM PUBLISHER]

This paper studies the interference graph construction for device-to-device (D2D) communications in cellular networks and proposes an interference graph construction protocol. The proposed interference graph construction protocol consists of two stages, i.e., announcement and collision resolution, which are performed in an iterative manner. The announcement announces the existence of each D2D link to its neighbor area by broadcasting announce messages. The collision-resolution stage resolves the collisions that could occur during the announce stage by broadcasting response messages. The theoretical analysis of the proposed construction protocol is presented, and the convergence of the protocol to an actual interference graph is studied. The theoretical analysis is validated by simulation results, and the performance of the proposed protocol is analyzed. It is shown that, for a number of D2D links up to as large as 1000 links, only two to seven iterations are needed to complete the interference graph construction procedure. [ABSTRACT FROM AUTHOR]

Cooperative hybrid automatic retransmission request (C-HARQ) is a simple and effective method for wireless communication. Since its performance largely depends on the selection of a relevant relay, the design of an appropriate relay selection scheme is very important. Although various works have been performed on this topic, most of them did not take into account both the “not memoryless” and multiple retransmission characteristics of C-HARQ, resulting in the loss of achievable performance. In this paper, we propose a novel cooperative relay selection scheme in a distributed manner called transmission number relaying (TNR) to simultaneously reduce the outage probability and increase the energy efficiency by utilizing the features of C-HARQ. The TNR scheme determines a single relay based on the estimated number of transmissions, which is calculated from the channel condition. Using these numbers instead of just the channel condition improves the outage probability and reduces the total consumed energy. The exact probability of the number of transmissions at each relay and the outage probability are analyzed, and the numerical results show that the proposed scheme significantly improves the outage probability and reduces the total consumed energy. In addition, when the number of available relays is small, the proposed scheme achieves high energy efficiency. [ABSTRACT FROM AUTHOR]

With the increasing connectivity between the Electronic Control Units (ECUs) and the outside world, safety and security have become stringent problems. The Controller Area Network (CAN) bus is the most commonly used in-vehicle network protocol, which lacks security mechanisms by design, so it is vulnerable to various attacks. In this paper, we propose a novel intrusion detection model called CNN-LSTM with Attention model (CLAM) for the in-vehicle network, especially CAN. The CLAM model uses one-dimensional convolution (Conv1D) to extract the abstract features of the signal values at each time step and feeds it into the Bidirectional Long Short Term Memory (Bi-LSTM) to extract the time dependence. By combining the attention mechanisms, we calculate the weight of each hidden state output by Bi-LSTM and perform a weighted summation, so that the model focuses only on locally important time steps, which can improve the convergence speed of the model and prediction accuracy. The proposed model uses the bit flip rate to extract continuous signal boundaries in the 64-bit CAN data, so it does not need to parse the CAN communication matrix and is suitable for different vehicles. The extensive evaluation results demonstrate that our proposed CLAM model can effectively detect CAN attacks, with an average F1-score of 0.951 and an error rate of 2.16%. Compared with the work in related research fields, the accuracy of attack detection is improved by 2.5%. [ABSTRACT FROM AUTHOR]

Autonomous Vehicles ($AV$ s) take advantage of Machine Learning (ML) for yielding improved experiences of self-driving. However, large-scale collection of $AV$ s’ data for training will inevitably result in a privacy leakage problem. Federated Learning (FL) is proposed to solve privacy leakage problems, but it is exposed to security threats such as model inversion, membership inference. Therefore, the vulnerability of the FL should be brought to the forefront when applying to $AV$ s. We propose a novel Byzantine-Fault-Tolerant (BFT) decentralized FL method with privacy-preservation for $AV$ s called BDFL. In this paper, a Peer-to-Peer (P2P) FL with BFT is built by extending the HydRand protocol. In order to protect their model, each $AV$ uses the Publicly Verifiable Secret Sharing(PVSS) scheme, which allows anyone to verify the correctness of encrypted shares. The evaluation results on the MNIST dataset have shown that introducing decentralized FL into $ AV$ area is feasible, and the proposed BDFL is superior to other BFT-based FL method. Furthermore, the experimental results on KITTI dataset indicate the practicality of BDFL on improving performances of multi-object recognition in $ AV$ areas. Finally, the proposed PVSS-based data privacy preservation scheme is also justified its characteristic of no side-effect on models’ parameters by the experiments on the MNIST and KITTI datasets. [ABSTRACT FROM AUTHOR]

With the dramatic growth of Bluetooth low energy (BLE), the indoor radio environment suffers from complex spectrum interference in the 2.4-GHz Industrial Scientific and Medical equipment (ISM) band, because BLE unconditionally transmits data without any carrier sensing or energy detection. With some recent trends reintroducing traditional wireless personal area networks standard for supporting the deployment of Internet of Things (e.g., Thread), IEEE 802.15.4 is spotlighted again, requiring mitigation of the mutual interference problem in the ISM band. For suitable coexistence under densely deployed BLE, this paper considers key impact phenomena of BLE characteristics, including studying a channelization and frequency-hopping mechanism. It finds a solution that can efficiently prevent problems by designing a multiple spectrum access scheme employing the same channelization that comes with BLE. To investigate the performance, this paper constructs a 4D Markov chain model describing the behavior of one communication node, and adopts an analytic matrix method to solve the model. The numerical results and experimental output are presented for further evaluation. [ABSTRACT FROM AUTHOR]

Terahertz (THz)-band (0.1–10 THz) communication is envisioned as a key wireless technology of the next decade, able to support wireless Terabit-per-second links in 6G systems. THz communication exhibits an extremely large bandwidth (tens to hundreds of GHz) at the cost of a very high path loss ($>$ 100 dB for distances beyond a few meters). Therefore, highly directional antennas (DAs) are needed simultaneously in transmission and reception at all times to establish reliable communication links. The application of highly DAs introduces new challenges in the neighbor discovery process. In this paper, a time-efficient neighbor discovery protocol for THz-band communication networks is proposed. The protocol expedites the neighbor discovery process by leveraging the full antenna radiation pattern to detect a series of effective signals and map them to the universal signal patterns, which indicate the potential direction of the signal source. A mathematical framework is developed to compare the neighbor discovery protocols with and without the antenna side-lobes information in free space. The X60 testbed is utilized to validate the proposed neighbor discovery protocol. Furthermore, a feasibility analysis of the proposed protocol inside a bounded space (e.g., a square room) is conducted. Numerical results are presented to illustrate the performance improvements achieved by the proposed protocol when compared to the traditional neighbor discovery protocols with only main-lobe information. [ABSTRACT FROM AUTHOR]

This paper considers random access in a communication channel, which is shared by $N$ active users with saturated traffic. Following a slotted ALOHA-type protocol, each active user attempts to transmit in every slot with a common probability. It is assumed that the channel has the multiple-packet reception capability to enable the correct reception of up to $M$ ($1 \leq M < N$) time-overlapping transmissions. To support mission- and time-critical applications that require reliable delivery within a strict delivery deadline $D$ (in units of slot), the aim of this paper is to achieve the maximum deadline-constrained reliability. First, we prove the uniqueness of the optimal transmission probability for any $1\leq M< N$ and any $D\geq 1$. Second, we show it can be computed by a fixed-point iteration for all the cases. Third, for real-life scenarios where $N$ may be unknown and changing, we develop a distributed algorithm for $M>1$ , which allows each active user to dynamically tune its transmission probability based on a method for estimating $N$. Simulation results verify our analysis and show that the proposed tuning algorithm is effective with near-optimal performance. In addition, as a special case (i.e., $D=1$) of our study, the issue of saturation throughput maximization is completely addressed for the first time. [ABSTRACT FROM AUTHOR]

In many bandwidth-critical environments, including vehicle-to-vehicle and vehicle-to-infrastructure communications, implicit certificates such as elliptic curve Qu-Vanstone (ECQV) are frequently employed as a means to reduce the bandwidth requirement of digital signatures. In these environments, however, certain recipients such as roadside units need to verify signatures for multiple messages within considerably short time periods. In this paper, we propose two efficient methods of reducing the computational costs of signature verification when multiple digital signatures are provided together with the ECQV implicit certificates. The first method achieves this by sharing the intermediate results that are computed when public keys are extracted from ECQV certificates. The second guarantees a further speed improvement by merging the public key extraction processes into a batch signature verification process. We also present an algorithm that adaptively chooses the best verification method for the given signatures in real time. Our experimental results show that the proposed methods allow for a signature verification that is five times faster than existing methods. [ABSTRACT FROM AUTHOR]

This correspondence paper presents automatic key generation for long-range wireless communication in low power wide area networks (LPWANs), employing LoRa as a case study. Differential quantization is adopted to extract a high level of randomness. Experiments conducted both in an outdoor urban environment and in an indoor environment demonstrate that this key generation technique is applicable for LPWANs and shows that it is able to reliably generate secure keys. [ABSTRACT FROM AUTHOR]

In this paper, efficient deployment algorithms are proposed for a mobile sensor network to improve the coverage area. The proposed algorithms find the target position of each sensor iteratively, based on the existing coverage holes in the network. The multiplicatively weighted Voronoi (MW-Voronoi) diagram is used to discover the coverage holes corresponding to different sensors with different sensing ranges. Three sensor deployment algorithms are provided, which tend to either move sensors out of densely packed areas or place them in proper positions with respect to the boundaries of the MW-Voronoi regions. Under the proposed procedures, the sensors move in such a way that the coverage holes in the target field are reduced. Simulations confirm the effectiveness of the deployment algorithms proposed in this paper. [ABSTRACT FROM PUBLISHER]

This paper deals with the modeling and analysis of the resequencing delay in time-division duplexing communication systems that adopt the Selective Repeat Automatic Repeat-reQuest error control strategy. Under the assumption that packet misordering at the receiving end is induced by channel errors, this paper proposes an analytical approach based on the absorbing Markov chain theory to accurately predict the impact of the resequencing delay on the quality of the provided services. Numerical results, which are derived by means of computer simulations, are also given to validate the proposed analytical model. [ABSTRACT FROM PUBLISHER]

Virtual multiple-input–multiple-output (MIMO) systems using multiple antennas at the transmitter and a single antenna at each of the receivers have recently emerged as an alternative to point-to-point MIMO systems. This paper investigates the relationship between energy efficiency (EE) and spectral efficiency (SE) for a virtual-MIMO system that has one destination and one relay using compress-and-forward (CF) cooperation. To capture the cost of cooperation, the power allocation (between the transmitter and the relay) and the bandwidth allocation (between the data and cooperation channels) are studied. This paper derives a tight upper bound for the overall system EE as a function of SE, which exhibits good accuracy for a wide range of SE values. The EE upper bound is used to formulate an EE optimization problem. Given a target SE, the optimal power and bandwidth allocation can be derived such that the overall EE is maximized. Results indicate that the EE performance of virtual-MIMO is sensitive to many factors, including resource-allocation schemes and channel characteristics. When an out-of-band cooperation channel is considered, the performance of virtual-MIMO is close to that of the MIMO case in terms of EE. Considering a shared-band cooperation channel, virtual-MIMO with optimal power and bandwidth allocation is more energy efficient than the noncooperation case under most SE values. [ABSTRACT FROM PUBLISHER]

In this paper, we examine the problem of designing and allocating transmission sequences to users in a mobile ad hoc network that has no spatial boundary. A basic tenet of the transmission sequence approach for addressing media access control (MAC) is that under normal operating conditions, there is no feedback-triggered retransmission. This obviously is a major departure from the Slotted-ALOHA or carrier-sense multiple-access (CSMA)-type approaches. While these traditional solutions enjoy excellent throughput performance, a fundamental drawback is that they are based on feedback information. For systems without a naturally defined central controller that can play the role of a base station, the task of providing feedback information could easily become unmanageable. This highlights the advantage of the feedback-free approach. A second advantage is the ability to handle unlimited spatial coverage. We propose in this paper a concept for MAC that is akin to frequency reuse. However, instead of reusing frequency, the new approach allows transmission sequences to be reused. A study of the transmission sequence approach against other approaches is conducted by comparing the minimal frame lengths that can guarantee the existence of conflict-free transmissions. [ABSTRACT FROM PUBLISHER]

This paper analyzes the performance of generalized multirelay cooperation (GMRC) protocols, which generalize the conventional single- and multiple-relay cooperative protocols, by allowing the number of relays employed in a cooperative cycle to vary with the instantaneous channel condition. Two variants of GMRC protocols are studied, including the output-detection GMRC (OD-GMRC) based on a decoding result and the output-threshold-test GMRC (OT-GMRC) relying on a threshold test. For both protocols, we derive the average outage probability and the average delay for completing a cooperative cycle, assuming uncoded decode-and-forward (DF) relays with multiple receiving antennas. Through numerical results, we validate the analysis accuracy and identify the ideal operational mode of GMRC under different network configurations. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a new clustered structure for a multiway relay network (MWRN) with $G$ clusters, $N$ users per cluster, one intracluster relay per cluster, and a single intercluster relay. The proposed structure allows private information exchange among users within a certain cluster through the corresponding intracluster relay and only public information exchange among users in different clusters through the intercluster relay. In this paper, we quantify the dominating error events in the proposed clustered MWRN and derive the expressions for the probability of these error events. Then, we use these expressions to derive the average bit error rate (BER) of a clustered MWRN. It is shown that clustering in an MWRN improves the error performance by reducing the number of dominating error events and, in effect, reducing error propagation, compared with the nonclustered counterpart. The analysis proves that the average BER of a clustered MWRN is minimized when the number of clusters and the number of users per cluster are chosen to be the closest possible factors of the total number of users, i.e., $L=GN$. Finally, numerical simulation results are provided to verify the validity of the analysis. [ABSTRACT FROM AUTHOR]

An important problem in a 3-D wireless sensor network with dense and random deployment of sensors is the minimization of the number of sensors required to cover a field of interest (FoI). Some monitoring applications may require the FoI to be k-covered, i.e., k\ge \mbox{1}, while redundant sensors must be scheduled to sleep to minimize energy consumption. In this paper, we address the problem of determining the probability of a sensor being redundant for the k$-coverage of the FoI. We assume that the network is heterogeneous, in which all the sensors may not have the same sensing and/or communication radii. We use a probabilistic approach to estimate the volume of the sensing sphere of an arbitrary sensor that is redundantly covered by its neighbors. We prove a result to determine if a sensor is redundant for $k$-coverage, which is only based on information about the number of neighbors and their type. We propose a distributed protocol to schedule the redundant sensors to sleep, which requires no geographical information. Results demonstrate that the scheduling protocol reduces the number of active sensors and, thereby, prolongs the network lifetime. [ABSTRACT FROM PUBLISHER]

In this paper, we address the problem of securing information transmission in very adverse environments, i.e., no eavesdropper channel state information (CSI) and imperfect legitimate channel CSI, by introducing a massive multiple-input–multiple-output (M-MIMO) relay. The relay is powered through wireless power transfer from the source, such that it can flexibly adjust its position according to the secrecy requirement. The benefits of a M-MIMO relay are fully exploited to enhance both power transfer efficiency and information transmission security. In particular, the challenging issues incurred by short interception distance and long transfer distance are well addressed simultaneously. The focus of this paper is on investigating the secrecy performance of two classical relaying protocols, namely amplify-and-forward (AF) and decode-and-forward (DF), and obtaining explicit expressions of secrecy outage capacity in terms of transmit power, channel condition, and antenna number. Furthermore, we propose two effective performance optimization schemes, i.e., power control at the source, and relaying protocol switch at the relay. Finally, our theoretical claims are validated by simulation results. [ABSTRACT FROM PUBLISHER]

This paper proposes a selection relaying (SR) protocol for a cooperative multiple-input–multiple-output (MIMO) relay system that consists of a direct link between a source and a destination. The system has only receive-side channel state information (CSI) and spatially correlated MIMO channels, and the receiver nodes observe spatially correlated noise. The transmit nodes employ orthogonal space–time block codes (OSTBCs), whereas the receiver nodes employ optimum minimum mean square error (MMSE) detection. The SR protocol, which transmits via the relay only when the direct link between the source and destination is in outage, is compared with the fixed relaying (FR) protocol, which always uses the relay. By deriving novel asymptotic expressions of the outage probabilities, it is analytically shown that both protocols provide the same diversity gain. However, the coding gain (CG) of the SR protocol can be much better than that of the FR protocol. In particular, when all MIMO links have the same effective rank, irrespective of its value, the SR protocol provides better CG than the FR scheme if the target information rate is greater than \ln_2(\mbox3) bits per channel use. Simulation results support theoretical analysis and show that the SR scheme can significantly outperform the FR method, which may justify the increased complexity due to the one-bit feedback requirement in the SR protocol. [ABSTRACT FROM AUTHOR]

In this paper, distributed spatial modulation (DSM) is introduced. DSM is a cooperative diversity protocol for multirelay wireless networks, which is based on the concept of spatial modulation (SM). The distinguishable feature of DSM lies in improving the reliability of the source via distributed diversity and by increasing the aggregate throughput of the network since new data is transmitted during each transmission phase. This is achieved by encoding the data transmitted from the source into the spatial positions of the available relays and by exploiting the signal domain to transmit the data of the relays. At the destination, a diversity combiner that is robust to demodulation errors at the relays is proposed, and its end-to-end error probability and achievable diversity are studied. It is mathematically proved that DSM allows the source to achieve second-order diversity. With the aid of Monte Carlo simulations, DSM is compared against state-of-the-art cooperative protocols, and it is shown to provide a better error probability. [ABSTRACT FROM AUTHOR]

This paper presents a coherent scheme to optimize an in-band full-duplex multiple-input–multiple-output (MIMO) relay via beamforming and transmit power allocation in a two-hop single-input–single-output (SISO) link under full channel knowledge and perfect hardware assumptions. First, we derive in closed form the optimal pair of transmit power and receive filter for a fixed transmit filter by unifying the minimum-mean-square-error (MMSE) filtering with the SISO-equivalent power allocation, as an iterative approach is not guaranteed to converge to global optimum. Second, we propose a heuristic algorithm to approximate the optimal transmit filter for a fixed receive filter. Furthermore, we study the well-known null-space projection constraint and derive a singular value decomposition (SVD)-based solution for the arbitrary-rank self-interference channel by generalizing the optimal solution under the assumption of rank-1 self-interference channel. Finally, we combine these solutions into a partially iterative algorithm in order to address the global optimization as our observations justify that some of the aforementioned schemes converge to the optimal solution under certain criteria. The numerical analysis of the proposed iterative algorithm demonstrates close-to-optimal performance relative to the theoretical upper bound of the end-to-end link in terms of maximum achievable throughput. [ABSTRACT FROM PUBLISHER]

Security is the main concern and bottleneck for widely deployed wireless applications due to the fact that wireless channels are vulnerable to attacks and that wireless bandwidth is a constrained resource. In this sense, it is desirable to adaptively achieve security according to the available resource. In particular, mobile ad hoc networks (MANETs) based on cooperative communication (CC) present significant challenges to security issues, as well as issues of network performance and management. In this paper, we focus on authentication and topology control issues. Although authentication and topology control are separately studied in most existing works, they are, in fact, closely correlated in MANETs. For example, both authentication and topology control schemes have significant impacts on throughput. In this paper, we jointly consider authentication and topology control. Specifically, we analyze the effective throughput with upper layer authentication schemes and physical-layer schemes related to channel conditions and relay selections for CCs. A joint authentication and topology control (JATC) scheme is proposed to improve the throughput. JATC is formulated as a discrete stochastic optimization problem, which does not require prior perfect channel status but only channel estimate. We also mathematically prove the tracking convergence property and the convergence rate of the discrete stochastic optimization approach in this paper. Simulation results show that our scheme can substantially improve throughput in MANETs with CC. [ABSTRACT FROM PUBLISHER]

To satisfy the increasing demands of cellular traffic, cooperative content caching at the network edge (e.g., User Equipment) has become a promising paradigm in the next-generation cellular networks. Device-to-Device (D2D) communications can improve the content caching and fetching performance without deploying additional infrastructure. In this paper, we investigate the joint optimization of cooperative caching and fetching in dynamic D2D environment for minimizing the overall content fetching delay. We formulate it as a decentralized partially observable Markov game for finding the optimal policies at agents. To address this problem, we propose a Fully Decentralized Soft Multi-Agent Reinforcement Learning (FDS-MARL) algorithm, which extends the soft actor-critic framework to non-stationary multi-agent environment for fully decentralized learning and it contains the following major design components: Graph Attention Network based self-attention for cooperative inter-agent coordination, a consensus communication mechanism for effectively reducing the information loss and non-stationarity of the environment while keeping gradual global consensus, and an influence based transmission scheduling mechanism for effective credit assignment and also alleviation of potential transmission contentions among agents. Simulation results show that FDS-MARL can improve the content caching and fetching performance significantly compared with the representative work in the literature. [ABSTRACT FROM AUTHOR]

With the rise of new technological paradigms such as the Internet of Things (IoT) and the Internet of Vehicles (IoV), we are going to see an unprecedented growth of connected vehicles on the roads. Also, with the ever-increasing complexity of vehicular electronics and with the increasing number of Electronic Control Units (ECUs) inside these next-generation vehicles, the need for verification of the firmware and software running on these ECUs using attestation techniques is heightened all the more. In this paper, we propose a lightweight and secure authentication and attestation scheme for attesting vehicles while they are on the roads. Since this attestation is proposed to be carried out on moving vehicles, there is also a need for authenticating the vehicles with the Road Side Units (RSUs) first before carrying out attestation. Therefore, a combined attestation and authentication scheme for verification of the vehicle ECU firmware is presented here. The ECU firmware running on the vehicles can be attested from the edge servers connected to the RSUs while the vehicles are in-transit and passing through these RSUs. We perform a security analysis of the proposed attestation and authentication protocol and compare it with other similar existing protocols. We also do a performance analysis of the proposed protocol and show the feasibility of its deployment. [ABSTRACT FROM AUTHOR]

Unmanned Aerial Vehicles (UAVs) are becoming very popular nowadays due to the emergence of application areas such as the Internet of Drones (IoD). They are finding wide applicability in areas ranging from package delivery systems to automated military applications. Nevertheless, communication security between a UAV and its ground station (GS) is critical for completing its task without leaking sensitive information either to the adversaries or to unauthenticated users. UAVs are especially vulnerable to physical capture and node tampering attacks. Further, since UAV devices are generally equipped with small batteries and limited memory storage, lightweight security techniques are best suited for them. Addressing these issues, a lightweight mutual authentication scheme based on Physical Unclonable Functions (PUFs) for UAV-GS authentication is presented in this paper. The UAV-GS authentication scheme is extended further to support UAV-UAV authentication. We present a formal security analysis as well as old-fashioned cryptanalysis and show that our protocol provides various security features such as mutual authentication, user anonymity, etc, and is resilient against many security attacks such as masquerade, replay, node tampering, and cloning attacks, etc. We also compare the performance of our protocol with state-of-the-art authentication protocols for UAVs, based on computation, communication, and memory storage cost. [ABSTRACT FROM AUTHOR]

This paper represents the design, feasibility evaluation, and performance validation of ICMR, a novel cross layer protocol that can maximize concurrent transmissions and avoid data frame interference in wireless networks, achieving a higher throughput comparing with the 802.11 standard and other state-of-the-art protocols. Observations on the 802.11 standard reveal that nodes around both the transmitter and receiver of the ongoing link waste concurrent transmission opportunities, degrading the network throughput dramatically. A state-of-the-art protocol IRMA is proposed to improve the network throughput through exploiting concurrent transmissions at the transmitter side. In this paper, a new ICMR protocol focuses on the receiver side to further improve the network throughput, through exploiting discernible interference cancellation, a physical layer mechanism that can successfully detect data frames when collided by control frames. We analyze the concurrent transmission opportunities of one link from the transmitter's transmission opportunities and the receiver's reception opportunities, then formulate the opportunities and give theoretical analysis to indicate that ICMR will have a higher opportunity over other protocols. Feasibility of the discernible interference cancellation mechanism is demonstrated through experiment results based on USRP2, and the throughput improvement of ICMR comparing with the other protocols is confirmed through simulations based on ns-2. [ABSTRACT FROM AUTHOR]

Covert communications is critical in many application scenarios for ensuring transmission security and privacy. Two-way protocols are widely adopted in intelligent reflecting surface (IRS) assisted relaying networks to enable covert communications and prevent wireless signals from being overheard. To quantify the performance of covert communications in this special scenario, we derive the closed-form expression of outage probability and its asymptote in this paper. Considering the worst-case of covert communications, the optimal normalized power threshold of warden's detector is analyzed under a complex Gaussian distribution approximation. To meet the requirement of the detection error probability, the ratio of the transmission power between the covert nodes is investigated. Simulation results are provided to validate the theoretical expressions as well as the asymptotic analysis with a small number of reflecting elements. [ABSTRACT FROM AUTHOR]

As millimeter wave (mmWave) technology becomes more integrated into today's communication infrastructure, its application to mobile scenarios has attracted considerable interests. In particular, mmWave technology is one of the leading candidates in Vehicle-to-Everything (V2X) community to address the ever-rising data exchange demand from vehicles. However, the inherent directionality of the technology poses challenges to peer discovery and transmission scheduling in typical V2X scenarios, causing significant loss of network capacity. To mitigate this issue, we propose a novel sub-6 GHz V2X-assisted synchronous mmWave communication scheduler in this paper. The sub-6 GHz channel serves as control channel for mmWave scheduling. The scheduler carefully considers data importance and freshness in determining communication schedule, such that network utility across mmWave links is maximized. We formulate the scheduling problem into an integer linear programming (ILP) problem. However, ILP problem is NP-hard and has exponential computational complexity for the worst cases. We then develop a scheduling algorithm, maximum weight matching based iterative algorithm (MWMIA), that operates in polynomial time with performance guarantees for the NP-hard ILP, by leveraging structural properties of link conflicts. Comparative simulation studies verify the effectiveness of our scheduler against other solutions. [ABSTRACT FROM AUTHOR]

Recent research showcased several cyber-attacks against unmodified licensed vehicles, demonstrating the vulnerability of their internal networks. Many solutions have already been proposed by industry and academia, aiming to detect and prevent cyber-attacks targeting in-vehicle networks. The majority of these proposals borrow security algorithms and techniques from the classical ICT domain, and in many cases they do not consider the inherent limitations of legacy automotive protocols and resource-constrained microcontrollers. This paper proposes DAGA, an anomaly detection algorithm for in-vehicle networks exploiting $n-$ gram analysis. DAGA only uses sequences of CAN message IDs for the definition of the $n-$ grams used in the detection process, without requiring the content of the payload or other CAN message fields. The DAGA framework allows the creation of detection models characterized by different memory footprints, allowing their deployment on microcontrollers with different hardware constraints. Experimental results based on three prototype implementations of DAGA showcase the trade off between hardware requirements and detection performance. DAGA outperforms the state-of-the-art detectors on the most performing microcontrollers, and can execute with lower performance on simple microcontrollers that cannot support the vast majority of IDS approaches proposed in literature. As additional contributions, we publicly release the full dataset and our reference DAGA implementations. [ABSTRACT FROM AUTHOR]

Mobile terminals have been widely used in the communication applications (e.g., vehicular network, e-Health, smart grid and e-Commerce) as they can obtain all kinds of services and upload data for users anytime and anywhere. With the number of users increasing dramatically and user demands diversifying, multi-server architecture was proposed to solve issues on lack of service resources that single-server architecture remains. However, multi-server architecture faces a series of challenges in applications, such as security and authentication efficiency requirements. Thus, many authenticated key agreement (AKA) protocols are presented, yet most of them require unacceptable computation and communication overhead, which is inefficient indeed. In this paper, we propose an adaptive secure handover authenticated key agreement protocol for multi-server architecture. Specifically, broadcast mechanism is utilized to assist users to select appropriate service providers with the lowest cost. Users can realize efficient handover authentication with multiple servers in the proposed scheme, that is, after completing initial authentication, users can switch to other servers and complete authentication through simple operations. Security analysis shows the proposed protocol can meet all security requirements and compared with other relevant protocols, it greatly reduces the computation and communication overhead. In addition, the above advantages grow significantly as the number of servers to be authenticated increases. [ABSTRACT FROM AUTHOR]

Autonomous vehicles (AVs) are increasingly common, although there remain a number of limitations that need to be addressed in order for their deployment to be more widespread. For example, to mitigate the failure of self-driving functions in AVs, introducing the remote control capability (which allows a human driver to operate the vehicle remotely in certain circumferences) is one of several countermeasures proposed. However, the remote control capability breaks the isolation of onboard driving systems and can be potentially exploited by malicious actors to take over control of the AVs; thus, risking the safety of the passengers and pedestrians (e.g., AVs are remotely taken over by terrorist groups to carry out coordinated attacks in places of mass gatherings). Therefore, security is a key, mandatory feature in the design of AVs. In this paper, we propose a cloud-centric three-factor authentication and key agreement protocol (CT-AKA) integrating passwords, biometrics and smart cards to ensure secure access to both cloud and AVs. Three typical biometric encryption approaches, including fuzzy vault, fuzzy commitment, and fuzzy extractor, are unified to achieve three-factor authentication without leaking the biometric privacy of users. Moreover, two session keys are negotiated in our protocol, namely: one between the user and AV to support secure remote control of the AV, and the other is negotiated between the mobile device and the cloud to introduce resilience to the compromise of ephemeral security parameters to ensure cloud data access security with a high security guarantee. Finally, we formally verify the security properties and evaluate the efficiency of CT-AKA, whose findings demonstrate that the protocol achieves high security strength with reasonable computation and communication costs. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the system outage performance of full-duplex (FD) two-way relay networks where all nodes are equipped with FD multiple-input multiple-output (MIMO) capability and two sources exchange information via decode-and-forward (DF) relay protocol in two consecutive time slots. In order to completely separate the desired signal and interference, we consider a finite size of buffer at the relay. We propose zero-forcing based beamforming schemes for two different cases of the buffer-aided relay and non-buffer-aided relay. We derive exact closed-form expression and lower bound of the outage probability for those two-way relay system, respectively. Numerical results show that the proposed buffer-aided relay scheme significantly improves the system performance over the conventional scheme in terms of outage probability. [ABSTRACT FROM AUTHOR]

Recently, millimeter-wave (mmWave) 5G localization has been shown to be to provide centimeter-level accuracy, lending itself to many location-aware applications, e.g., connected autonomous vehicles (CAVs). One assumption usually made in the investigation of localization methods is that the user equipment (UE), i.e., a CAV, and the base station (BS) are time synchronized. In this paper, we remove this assumption and investigate two two-way localization protocols: (i) a round-trip localization protocol (RLP), whereby the BS and UE exchange signals in two rounds of transmission and then localization is achieved using the signal received in the second round; (ii) a collaborative localization protocol (CLP), whereby localization is achieved using the signals received in the two rounds. We derive the position and orientation error bounds applying beamforming at both ends and compare them to the traditional one-way localization. Our results show that mmWave localization is mainly limited by the angular rather than the temporal estimation and that CLP significantly outperforms RLP. Our simulations also show that it is more beneficial to have more antennas at the BS than at the UE. [ABSTRACT FROM AUTHOR]