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The dynamic interaction of vehicles/bridges is an important part of the research field of the Electromagnet Suspension (EMS) maglev train. However, multiple factors affect the dynamics of the coupling system, which increases the complexity of the vehicle-bridge coupling system, and makes it difficult to analyze. Herein, combining the advantages of theoretical derivation and numerical calculation, a fast and accurate analysis method of maglev vehicle and bridge system is proposed to analyze the influence of bridge and controller on the dynamics of the maglev system. This work is directed to the Changsha maglev express line, in which the mathematical equations for the vehicle- bridge system is presented. Then the influence of the parameter on the system is analyzed. Finally, the vibration experimental test system is set up, and the vibration test of the maglev vehicle bridge is tested by the test scheme, and the experimental results data are given. The test results of vibration acceleration are in good agreement with the calculation results of the proposed method, which verifies the accuracy of the model and the analysis method. Therefore, the research in this paper can provide theoretical guidance for Maglev engineering, and the analysis method in this paper can also be used in the study of other vehicles, such as the high-speed maglev train. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the realization of synchronized spread spectrum code division multiple access (synchronized SS-CDMA) for the quasi-zenith satellite system (QZSS) safety confirmation system during major disasters. The QZSS is expected to provide a highly accurate positioning service and allow two-way communication, which includes the terminal location and short messages. The proposed synchronized SS-CDMA scheme realizes direct access from mobile terminals to the satellite and the simultaneous transmission of many users using SS codes with a large spreading factor. All terminals synchronize their own clock and frequency with those of the global navigation satellite system (GNSS). In this scheme, maintaining orthogonality among users in both the time and frequency domains is the most important problem. In this paper, for the consideration of mobile use, the effect of residual timing jitter and frequency offset in a fading environment is evaluated by computer simulation. As a result, acceptable timing and frequency errors for terminals are clarified in order for the system to be viable using the GNSS. [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]

With the increasing demand of spectrum and emergence of mobile devices, a cloud radio access network (C-RAN) is a promising technology to improve network capacity and coverage. The key concept of the C-RAN is to separate the radio function unit in remote radio heads (RRHs) from the digital function unit in baseband units (BBUs). This separation facilitates efficient spectrum and infrastructure sharing in the C-RAN. This paper considers the cooperative interference management among RRHs in the C-RAN. The RRHs can form coalitions to mitigate intra-interference and jointly serve their subscribers. To characterize RRH performance under the coalition, this paper develops two signal-to-interference-plus-noise-ratio (SINR)-based downlink throughput models of RRH, where one adopts tools from stochastic geometry to capture the interference from vehicular users (VUs) belonging to noncooperative RRHs, and another ignores the VU interference. In this paper, a coalition formation game is formulated to model the situation in which RRHs of C-RAN can make an individual decision to cooperatively serve their VUs if the throughput of the RRH can be improved. To obtain the solution of the proposed game, we develop a distributed coalition formation algorithm and analyze the stability of the coalition structure using a Markov chain model. Simulation results show that, as compared with the noncoalition and grand coalition, our distributed coalition formation can improve the C-RAN throughput by at least 20% and 80%, respectively. Furthermore, according to extensive simulation, we can define the conditions needed for RRHs to form a coalition and obtain higher throughput. [ABSTRACT FROM PUBLISHER]

In this paper, we consider the intercell interference coordination (ICIC) problem in heterogeneous cellular networks with randomly deployed small-cell base stations (BSs). Current research on ICIC mainly focuses on optimizing the spectrum and power allocations at BSs, whereas the user–BS association is treated as a separate issue. Nevertheless, the user–BS association problem is an important issue in ICIC and should be jointly optimized with resource allocations to achieve global optimality. In this paper, with the objective of maximizing the system sum rate in a distributed manner, we propose a novel belief propagation (BP) algorithm to jointly optimize user association, subchannel assignment, and power allocation. We first develop a factor graph model to decompose the network-wide objective and constraints into multiple local utilities. Then, we transform the maximization of local utilities into the estimations of marginal distributions and propose a distributed BP algorithm to solve the estimations. Simulations show that our distributed BP algorithm dramatically improves the performance compared with the benchmark scheme. [ABSTRACT FROM AUTHOR]

Thanks to excellent mobility and high probability of a Line-of-Sight (LoS) to ground objects, unmanned aerial vehicles (UAVs) have been widely used in surveillance. This paper considers the use of UAVs to covertly and collaboratively eavesdrop on suspicious wireless transmitters on the ground. We focus on the trajectory planning of the UAVs. To avoid the UAVs being visually noticed by the ground transmitters, we propose a new measure to quantify the disguising performance of the UAVs. The trajectories of the UAVs are planned to maximize the disguising performance, subject to an uninterrupted eavesdropping requirement, UAV collision avoidance and UAV aeronautic maneuverability. A new randomized method based on the Rapidly-exploring Random Tree (RRT) is developed to efficiently construct the trajectories of the UAVs. Computer simulations confirm that the proposed method outperforms the random movement method in eavesdropping performance, while achieving with comparable disguising performance. [ABSTRACT FROM AUTHOR]

This paper investigates distributed beamforming networks composed of multiple groups of transmitters where each group consists of two transmitters. The goal is to jointly optimize the phase components at the transmitters and the orientation angles of the groups that maximize the radiated energy over an angular sector containing an adversary while placing a null towards the client in order not to obfuscate the client. Since the optimization problem is non-convex, it is intractable to obtain the optimal solution in closed-form. To this end, we propose a non-iterative closed-form solution by adopting a group-wise nullforming approach where each group independently creates a null to the client. The effectiveness of the proposed scheme is validated through numerical simulations. [ABSTRACT FROM AUTHOR]

Interference alignment (IA) is a precoding technique that aligns interfering signals at receivers. It is known that IA achieves the maximum degrees of freedom over an interference channel under ideal assumptions. The real-world performance of IA depends on a range of practical issues, such as imperfect synchronization, channel estimation, and feedback. Practical issues have been studied in simulations and prototypes, but fully distributed operation of IA network nodes has not been considered. In this paper, we present the first investigation of real-time IA performance on a fully distributed 2 $\times$ 2 multiple-input–multiple-output (MIMO) prototype system with three physically independent user pairs. Over-the-air algorithms for time and frequency synchronization, as well as analog feedback, are studied and implemented. Sum rates are illustrated as a function of complexity and accuracy of different alignment, synchronization, and feedback algorithms. Corresponding tradeoffs are evaluated using an iterative IA method, the injection of residual frequency offset into synchronization, and analog versus quantization-based limited feedback approaches. We demonstrate that, while considering all possible error sources in estimation, synchronization, and feedback, the theoretical multiplexing gain of IA can be reached in practical systems with a constant sum rate loss that remains within 5 bits/Hz/s compared with an ideal simulation. [ABSTRACT FROM PUBLISHER]

This paper investigates the distributed adaptive control problems for nonlinear vehicle-following systems subject to nonlinear acceleration uncertainties involving vehicle acceleration disturbances, wind gusts, and parameter uncertainties. It is worth mentioning that the acceleration of the leader in most existing studies is always assumed to be zero or constant; the evolution of the leader in this paper may be subject to some unknown bounded input. Distributed adaptive control strategies based on an integral sliding mode control (ISMC) technique are proposed to maintain a rigid formation for a string of vehicle platoon in one dimension. First, distributed adaptive control based on traditional constant time headway (TCTH) policy under the assumption that the initial spacing and velocity errors are zero is developed to guarantee that all spacing errors are uniformly ultimately bounded and that the string stability of the whole vehicle platoon is also satisfied. Then, a modified constant time headway (MCTH) policy is proposed to remove the assumption of zero initial spacing and velocity errors and simultaneously effectively decrease the intervehicle spacing (i.e., increase the traffic density), making them nearly equal to those by using the constant spacing (CS) policy. Adaptive compensation terms without requiring a prior knowledge of upper bounds of the uncertainties are constructed to compensate for the time-variant effects caused by nonlinear acceleration uncertainties. Finally, numerical simulation results show the validity and advantages of the proposed policy up to a significant higher traffic density. [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]

This paper studies the application of network non-orthogonal multiple access (N-NOMA) to vehicular communication networks, modeled by a Poisson line Cox point process (PLC). Particularly, the road infrastructure is modeled by a Poisson line point process (PLP), whereas base stations (BSs) and users are located according to 1D homogeneous Poisson point processes (HPPPs) on each road. In the considered N-NOMA scheme, there are two types of users, i.e., coordinated multi-point (CoMP) users which are far from their BSs and NOMA users which are close to their BSs, where the CoMP users and the NOMA users are served simultaneously by applying the principle of NOMA. Specifically, the BSs collaborate with each other to provide reliable transmission for the CoMP user by applying Almouti coding, while each BS employs superposition coding to opportunistically serve an additional NOMA user. Compared to a conventional OMA based scheme, where only a CoMP user is served, the proposed N-NOMA scheme significantly improves the performance in terms of outage sum rates and user connectivity, since more users are served in the same resource block. A comprehensive analytical framework is developed to characterize the system level performance of the proposed N-NOMA scheme by applying PLC. Closed form expressions for the outage probabilities achieved by the CoMP and NOMA users are obtained. Computer simulation results are provided to show the superior performance of the proposed scheme and also validate the accuracy of the developed analytical results. [ABSTRACT FROM AUTHOR]

In this paper, a general two-way relay (TWR) transmission method is proposed under per-antenna power constraints by combining space-time line codes (STLCs) with transmit power allocation for two source nodes. We introduce a general STLC-based encoding scheme for a decode-and-forward TWR and derive the detection signal-to-interference-plus-noise ratio (SINR) values at two source nodes. An optimal encoder structure with power allocation is proposed in terms of maximizing the minimum SINRs, and it is verified that the optimal encoder is identical to the superposition of two conventional STLCs. An iterative method is proposed to find the optimal power allocation for detection at two source nodes. Moreover, a low-complexity suboptimal encoder is proposed for practical implementation. Numerical simulations present that the proposed STLC-based transmission method outperforms a conventional eigen-beamforming scheme with nulling and an STLC-based scheme with equal power allocation, in terms of the average bit error rate of source nodes, regardless of the distribution of source nodes, the number of TWR antennas, and the transmit power. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study on millimeter-wave-based mobile hotspot network (MHN) system for high-speed train (HST) communications, including system design, field trial, channel modeling based on measurement campaign, simulation, and validation. First, an overview of the MHN system and the design of an MHN enhanced (MHN-E) system including physical layer specification and single frequency network are provided. Second, the overall design of prototypes for MHN conventional (MHN-C) and MHN-E systems is presented, and then the recent experimental results of a field trial conducted at Seoul subway line 8 with the MHN-C prototype and demonstrations with the MHN-E prototype are analyzed. Third, this paper presents a measurement campaign investigating channel characteristics of a rural HST environment and a QuaDRiGa-based channel model developed based on the parameters extracted from the measurement. Finally, a computer simulation is conducted to validate the performance of the MHN-E system at high mobility of up to 500 km/h under the QuaDRiGa channel model, which suggests a good methodology for the validation of HST communication systems at the highmobility since it is impractical to be tested by real testbeds as of now. The simulation results revealed that the MHN-E system is capable of providing a broadband mobile wireless backhaul with a peak data rate exceeding 5 Gb/s at a speed of 500 km/h. [ABSTRACT FROM AUTHOR]

This paper presents the usage of additional tire information in the form of cornering stiffness to enhance vehicle handling and stability with an adaptive rear-wheel steering control (RWS). The influence of varying cornering stiffness on driving behavior is discussed in advance with a single-track model. On the basis of an enhanced single-track model, a RWS feedforward control is presented with a provided tuning parameter adapting the desired rear axle cornering stiffness for the vehicle. In the following, this paper proposes an adaption law that is derived in order to enhance handling performance and safety of a vehicle, taking into account conflicting goals. Finally, simulation results and driving experiments with the adaptive RWS feedforward control are evaluated in both steady-state and transient conditions. In order to examine the full potential of the approach, the controller is adapted to a wide spreading of the cornering stiffness. Therefore, identified cornering stiffnesses of winter-, summer- and ultra-high performance tires are used as a basis for the adaption. [ABSTRACT FROM AUTHOR]

Beamforming has a great potential for joint communication and radar sensing (JCAS), which is becoming a demanding feature on many emerging platforms, such as unmanned aerial vehicles and smart cars. Although beamforming has been extensively studied for communication and radar sensing respectively, its application in the joint system is not straightforward due to different beamforming requirements by communication and sensing. In this paper, we propose a novel multibeam framework using steerable analog antenna arrays, which allows seamless integration of communication and sensing. Different to conventional JCAS schemes that support JCAS using a single beam, our framework is based on the key innovation of multibeam technology: providing fixed subbeam for communication and packet-varying scanning subbeam for sensing, simultaneously from a single transmitting array. We provide a system architecture and protocols for the proposed framework, complying well with modern packet communication systems with multicarrier modulation. We also propose low-complexity and effective multibeam design and generation methods, which offer great flexibility in meeting different communication and sensing requirements. We further develop sensing parameter estimation algorithms using conventional digital Fourier transform and one-dimensional compressive sensing techniques, matching well with the multibeam framework. Simulation results are provided and validate the effectiveness of our proposed framework, beamforming design methods, and the sensing algorithms. [ABSTRACT FROM AUTHOR]

Blind signal identification has important applications in both civilian and military communications. Previous investigations on blind identification of space-frequency block codes (SFBCs) only considered identifying Alamouti and spatial multiplexing transmission schemes. In this paper, we propose a novel algorithm to identify SFBCs by analyzing discriminating features for different SFBCs, calculated by separating the signal subspace and noise subspace of the received signals at different adjacent OFDM subcarriers. Relying on random matrix theory, this algorithm utilizes a serial hypothesis test to determine the decision boundary according to the maximum eigenvalue in the noise subspace. Then, a decision tree of a special distance metric is employed for decision making. The proposed algorithm does not require prior knowledge of the signal parameters such as the number of transmit antennas, channel coefficients, modulation mode, and noise power. Simulation results verify the viability of the proposed algorithm for a reduced observation period with an acceptable computational complexity. [ABSTRACT FROM AUTHOR]

In this paper, we propose a sparse signal estimation algorithm that is suitable for many wireless communication systems, especially for the future millimeter wave and underwater communication systems. This algorithm is not only asymptotically optimal, but also robust to the distribution of nonzero entries of the sparse signal. Then, we derive its upper bound and lower bound, and show that the mean square error of the proposed algorithm can approach the minimum mean square error bound when the signal noise ratio goes to infinite or zero. Numerical simulations verify our theoretical analysis and also show that the proposed algorithm converges faster than existing algorithms, e.g., turbo-type signal recovery-discrete fourier transform, approximate message passing, etc. [ABSTRACT FROM AUTHOR]

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]

Responsive and highly controlled autonomous vehicles (AVs) on the road easily form platoons with small inter-vehicle gaps to increase traffic throughput and reduce energy consumption. Unlike human drivers, AVs typically employ discrete quantization signals and only generate finite discrete acceleration. Finite discrete acceleration easily causes unstable inter-vehicle gaps and inter-vehicle collisions, especially when there are inaccurate quantization parameters due to quantizer aging. Based on the backstepping technique, this paper proposes the cooperative constrained control algorithm under unknown quantization parameters for AVs with nonuniform input quantization and motion uncertainties. The control laws of each AV in the platoon only depend on the state information of its consecutive AVs. The position trajectories of consecutive AVs are constructed as inter-vehicle collision-free constraints to avoid emergency braking and inter-vehicle collisions. In addition, the consistent characteristic of two types of nonuniform quantizers (i.e., logarithmic quantizers and hysteresis quantizers) is proposed, and unknown disturbances in vehicle motion are compensated. The Lyapunov based local stability and string stability are proved. Numerical simulation shows that the control algorithm is applicable to AVs with either logarithmic quantizers or hysteresis quantizers. Compared with the previous control algorithms without considering input quantization and inter-vehicle collision avoidance, the control algorithm proposed reduces inter-vehicle spacing errors, avoids high acceleration, and avoids inter-vehicle collisions. [ABSTRACT FROM AUTHOR]

In this paper, the downlink of a clustered coordinated multicell multiuser multiple-input multiple-output (MIMO) system is considered, and various low-complexity user scheduling algorithms to maximize the sum rate are proposed. The users' data signals are transmitted cooperatively via the base stations (BSs) of a cluster within the sectorized multicell heterogeneous cellular network. Exhaustive search as the optimal scheduling method is extremely complex, particularly for large numbers of users requesting service. We therefore propose suboptimal scheduling algorithms based on the lower complexity metaheuristic stochastic optimization techniques of simulated annealing (SA) and particle swarm (PS). Moreover, a hybrid algorithm combining the traits of PS and a greedy scheduler is also proposed. The performance and complexity of these algorithms are evaluated for a heterogeneous system model employing different precoding methods. Assessing the algorithms' performance via computer simulations, the effectiveness of the proposed schemes in terms of sum rate is demonstrated, yielding performance very close to that of the exhaustive search at much lower complexity. For each precoding method used in the employed system model, the best corresponding approach to scheduling from our proposed algorithms is determined. [ABSTRACT FROM AUTHOR]

This paper proposes an algorithm to control the suspension dynamics with an energy regeneration capability and high conversion efficiency. Central to the concept is the development of a switched-mode rectifier (SMR) that is capable of providing either an equivalent positive or negative damping and alternating between regenerative and motoring modes. Simulation results are presented to demonstrate power flow in regeneration and motoring modes and verify the equivalent damping characteristic and vibration energy harvesting. The studies are conducted on a small-scale proof-of-concept electromagnetic suspension system excited by emulated International Standard Organization (ISO) 8608 road profiles. An autonomous start/stop algorithm is proposed such that autonomously turns on or off the converter. This mechanism mitigates quiescent power consumption of auxiliary integrated circuits (ICs) such as gate drivers and current transducers, therefore increasing the conversion efficiency of the power electronics throughout an ISO standardized variable-speed driving cycle. The autonomous start/stop algorithm is implemented experimentally to demonstrate its feasibility under typical standardized driving cycles. [ABSTRACT FROM PUBLISHER]

This paper proposes a new efficient path-planning algorithm for articulated steering vehicles operating in semi-structured environments, in which obstacles are detected online by the vehicle's sensors. The first step of the algorithm is offline and computes a finite set of feasible motions that connect discrete robot states to construct a search space. The motion primitives are parameterized using Bézier curves and optimized as a nonlinear programming problem (NLP) equivalent to the constrained path planning problem. Applying the A^\ast search algorithm to the search space produces the shortest paths as a sequence of these primitives. The sequence is drivable and suboptimal, but it can cause unnatural swerves. Therefore, online path smoothing, which uses a gradient-based method, is applied to solve another NLP. Numerical simulations demonstrate that performance of the proposed algorithm is significantly better than that of existing methods when determining constrained path optimization. Moreover, field experimental results demonstrate the successful generation of fast and safe trajectories for real-time autonomous driving. [ABSTRACT FROM AUTHOR]

This paper presents an optimal control algorithm for connected cruise control (CCC) system in the presence of the stochastic communication delays. In the CCC system, wireless vehicle-to-vehicle (V2V) communication is the key factor to achieve comprehensive environment perception while it gives rise to delays in the meantime. In order to compensate for the influence of the stochastic delays and develop an optimal controller for the CCC system, we first analyze the vehicle dynamics with the car-following model. Then, the mathematical platoon model is formulated with heterogenous platoon structure. With the objective of minimizing the deviations of vehicle's headway and velocity, a linear quadratic optimization problem is formulated. The optimal control strategy is solved in an iterative manner by using a backward recursion which can be divided into two steps. In particular, the optimal control gain is iteratively derived off-line and the control strategy is calculated on-line. In addition, the control gain convergence, the stability analysis, and the effect of the packet losses and state noises are analyzed. Finally, the stability and performance of the proposed control algorithm are verified by numerical simulations to highlight its superiority compared with the existing algorithms. [ABSTRACT FROM AUTHOR]

In this paper, we investigate a hybrid multicast/unicast scheme for a multiple-input single-output cache-aided non-orthogonal multiple access (NOMA) vehicular scenario in the face of rapidly fluctuating vehicular wireless channels. Considering a more practical situation, imperfect channel state information is taking into account. In this paper, we formulate an optimization problem to maximize the unicast sum rate under the constraints of the peak power, the peak backhaul, the minimum unicast rate, and the maximum multicast outage probability. To solve the formulated non-convex problem, a lower bound relaxation method is proposed, which enables a division of the original problem into two convex sub-problems. Computer simulations show that the proposed caching-aided NOMA is superior to the orthogonal multiple access counterpart. [ABSTRACT FROM AUTHOR]

This paper presents a geometry-based stochastic channel model (GSCM) for a 3GPP millimeter-wave (mmWave) high-speed train (HST) scenario. An important demand of the mmWave HST channel model is the spatial consistency during movement. In order to meet this requirement, the environment pattern containing the most effective geometry information is proposed, which is useful for generating an integral and accurate channel geometry. Since the measurement of a mmWave channel is deficient for high mobility, the proposed channel model is developed using a ray-tracing (RT) simulator that is validated with the channel measurements performed in the HST scenario at 93.2 GHz. The paper gives a full parameterization for the proposed model and its implementation for channel simulation. The verification is made through a comparison of the proposed model and the measurement-validated RT simulations in terms of the power delay profile, the Ricean $K$-factor, and the second-order statistics for the delay and angle domains. Finally, for the design of mmWave HST communication systems, the time-varying channel characteristics are evaluated in the delay and Doppler domains. [ABSTRACT FROM PUBLISHER]

This paper proposes a current-fed single-phase inverter without constant intermediate DC link. It eliminates electrolytic capacitor from the DC-link and introduces an intermediate pulsating DC bus. The proposed topology is modular with three full-bridges making it scalable for high-power applications. New pulsating-DC-modulation for back-end pulsating DC-link inverter and secondary modulation (SM) for front-end DC-to-pulsating DC converter is proposed. Soft-switching and device voltage clamping of both primary side and secondary side devices of front-end current-fed full-bridge converter is realized. A rotating partial hybrid pulsewidth modulation has been introduced. One leg of inverter is commutated at a low switching frequency, while the other leg is operated at a high switching frequency for partial period of a line frequency cycle. Thus, switching losses of the back-end inverter are considerably reduced. Rotating mechanism is used to equalize the switching losses of four switches of the inverter. This paper presents detailed operation and analysis of the topology with a proposed modulation scheme. Simulation and experimental results validate the effectiveness and accuracy of the proposed modulation scheme as well as soft-switching and performance of the converter. [ABSTRACT FROM PUBLISHER]

This paper studies the network connectivity problem in a vehicular network and focuses on the two-way connectivity of vehicles moving on a one-way highway road with one entry and exit. The entry and exit separates the road into two segments, where vehicle arrivals follow a Poisson process. At the entry and exit, a vehicle may enter or exit from the road, or drive through the entry and exit. A connectivity analytical model is derived for analyzing the connectivity probability of vehicles moving on the road. The analytical model takes into account several parameters that may affect the connectivity probability, including a vehicle's arrival rate and moving speed as well as the probability that a vehicle drives through the entry and exit. Moreover, it considers two entry and exit scenarios: one with no roadside unit (RSU) deployed, and the other with one RSU deployed. The analytical model is justified through simulation results and the impacts of different parameters on the connectivity probability are investigated based on the derived analytical model. [ABSTRACT FROM PUBLISHER]

Generalized spatial modulation (GenSM) aided millimeter wave (mmWave) multiple-input multiple-output (MIMO) has recently received substantial academic attention. However, due to the insufficient exploitation of the transmitter's knowledge of the channel state information, the achievable rates of state-of-the-art GenSM-aided mmWave MIMO systems are far from being optimal. Against this background, a novel analog precoding scheme is proposed in this paper to improve the spectral efficiency (SE) of conventional GenSM-aided mmWave MIMOs. More specifically, we firstly manage to lower-bound the achievable SE of GenSM-aided mmWave MIMO with a closed-form expression. Second, by exploiting this lower bound as a cost function, a low-complexity iterative algorithm is proposed to design the analog precoder for SE maximization. Finally, numerical simulations are conducted to substantiate the superior performance of the proposed design with respect to state-of-the-art GenSM-aided mmWave MIMO schemes. [ABSTRACT FROM PUBLISHER]

Device-to-device (D2D) communications underlaying cellular networks have been recently considered as a promising means to enhance resource utilization of the cellular network and local user throughput among devices in proximity to each other. In this paper, we investigate the joint resource block assignment and transmit power allocation problem to optimize the network performance in such a scenario. Specifically, we model the interference relationships among different D2D and cellular communication links as a novel interference graph with unique attributes and propose a corresponding joint resource-allocation scheme that can effectively lead to a near-optimal solution at the base station, with low computational complexity. Simulation results confirm that, with markedly reduced complexity, our proposed scheme achieves a network throughput that approaches the one corresponding to the optimal resource-sharing scheme obtained via exhaustive search. [ABSTRACT FROM PUBLISHER]

This paper presents a method for simultaneous segmentation and modeling of objects, detected in range data gathered by a laser scanner mounted onboard ground-robotic platforms. Superquadrics are used as model for both segmentation and object shape fitting. The proposed method, which we name Simultaneous Segmentation and Superquadrics Fitting, relies on a novel global objective function that accounts for the size of the object and the distance of range points, and for partial occlusions. Results on experimental 2-D range data, which are collected from indoor and outdoor environments, are qualitatively and quantitatively analyzed. Results are compared with those from popular and state-of-the-art segmentation methods. Moreover, we present results on 3-D data obtained from an in-house setup and also from a Velodyne LIDAR. This paper finds applications in areas of mobile robotics and autonomous vehicles, namely object detection, segmentation, and modeling. [ABSTRACT FROM PUBLISHER]

In this paper, we study the underlay relay-aided Device-to-Device (D2D) communications to improve the physical layer (PHY) security of the cellular network. We propose a cooperative scheme, whereby the D2D pair, in return of being allowed to share the spectrum band of the cellular network, serves as a friendly jammer, through its multiple-input multiple-output relay, to degrade the wiretapped signal at an eavesdropper. This paper aims to show that spectrum sharing is advantageous for both D2D communications and cellular networks with respect to reliability and robustness for the former, and the physical layer security enhancement for the latter. To assess the proposed cooperative system model, closed-form expressions for the D2D outage probability, the secrecy outage probability, and the probability of non-zero secrecy capacity are derived. More importantly, the benefits due to the cooperation scheme are verified through numerical and simulation results. [ABSTRACT FROM AUTHOR]

In this work, we use the acoustic ray model to study passive source localization problems using a single hydrophone for shallow water waveguides. It has been found that conventional matched field processing, which requires a multi-hydrophone array, is no longer effective. In this paper, we introduce matched feature localization to achieve passive source localization using a single hydrophone. The eigenray that contains the arrival structure is the core of the acoustic ray model; however, it is difficult to estimate the relative arrival delay of the eigenray for passive localization, especially in shallow water. Therefore, we propose a novel peak extraction passive source localization method based on the autocorrelation function, which does not require estimation of the relative arrival delay of the eigenray. According to a computer simulation, the proposed method can achieve good performance using only one hydrophone. Further, its performance is validated using wideband data collected on a vertical line array during the Shallow Water 2006 experiment. [ABSTRACT FROM AUTHOR]

In this paper, we propose an uplink multiuser-multiple input multiple output (MU-MIMO) cooperative retransmission control scheme for the reliable and efficient communication of autonomous unmanned aerial vehicles (i.e., flight communication and drone-to-drone communication). This scheme is a key element in the design of a drone-based ad-hoc network. Because drone relay transmission operates in the air, flexible wireless relay networks over large areas can be achieved without interference from multipath signals caused by buildings and obstacles in ground-based communication. However, two main challenges exist. First, the relay transmission system occupies bandwidth every time the drone relays information. Therefore, because the radio channel is shared by multiple relay stations, the throughput is greatly reduced. To improve throughput, it is better to transmit using the minimum number of relay stations. Ultimately, long-distance direct transmission is the best. The other issue is a direct result of the first issues solution: the propagation loss increase when relaying information directly over a long distance. Moreover, because the frequency of interference waves from the ground increases, transmission signal errors are an important issue. To solve this issue, a transmission scheme to reduce errors is required. The scheme proposed in this study achieves high transmission reliability and efficiency even under high transmission error conditions. The results of a computer simulation reveal that the proposed method achieves a direct transmission throughput that is 1.5 times better than that of a conventional scheme. It is also shown that the proposed scheme requires only about three stations to achieve acceptable results. [ABSTRACT FROM AUTHOR]

Non-orthogonal multiple access (NOMA)-based cooperative relaying systems (CRS) are very promising to overcome spectral inefficiency of conventional cooperative communications. Although NOMA-CRS have great recent attention, almost all studies investigate NOMA-CRS only in terms of capacity and outage probability. Error performances of NOMA-CRS have not been well-studied. In this paper, we analyze error performance of NOMA-based diamond relaying network (NOMA-DRN) with imperfect successive interference canceler (SIC) as a NOMA-CRS scheme. We derive exact bit error probability (BEP) for NOMA-DRN and provide a tight approximated BEP in the closed-form. In addition, high-SNR analysis is conducted to present that NOMA-DRN has an error floor. Moreover, it is proved that NOMA-DRN turns out to be a non-equiprobable communication system and we derive priori probabilities of symbols. All derived expressions are validated via computer simulations. [ABSTRACT FROM AUTHOR]

This paper investigates the problem of asymptotic stabilization of underactuated surface vehicles (USVs) with actuator dead-zones and yaw constraints. By transforming the system model into two subsystems, a backstepping control method based on a Barrier Lyapunov Function (BLF) is introduced to stabilize the transformed system and prevent the USV from reaching the boundaries of yaw angle and velocity constraints. A fixed-time disturbance observer is involved in the USV controller to deal with actuator dead-zones and disturbances. The method is extended to cover the case in which the yaw constraints are time-varying and the initial states exceed the constraint regions. Numerical simulations have shown the effectiveness of the presented method. [ABSTRACT FROM AUTHOR]

Thanks to their ubiquitous coverage, Long-Term Evolution (LTE) networks are considered the most potential enabler for massive Machine-Type Communications (mMTC) service in fifth-generation (5G) context. LTE standard, however, was not designed for mMTC and scenarios where the massive Machine-Type Devices (MTDs) population try to access a network over a short period may overload the Random Access CHannel (RACH). Furthermore, there is no mechanism to prioritize urgent MTDs in such overload situation. The baseline Access Class Barring (B-ACB) scheme is thus adopted by the 3GPP to address both issues at a substantial cost of access delay. This paper follows a different approach and proposes a complete solution to the two main issues of cellular mMTC. We promote the use of a mechanism called Distributed Queueing (DQ), aided by a MAC-layer load estimation technique, to effectively resolve contentions between the MTDs to improve delay performance with minimal impacts to LTE access procedure and air interface. Then, by exploiting information related to congestion level from the DQ process, a dynamic access prioritization scheme can be realized without additional signaling overhead. Computer simulation under an mMTC-oriented traffic model shows that our framework outperforms the B-ACB in terms of both access delay and energy consumption when all devices are of equal importance. On the other hand, when devices of different priorities coexist, our framework with proper tuning also offers lower delay for all classes and lower overall energy consumption compared to both the baseline and a dynamic ACB solutions in massive bursty access scenarios. [ABSTRACT FROM AUTHOR]

The increasing demand for rich multimedia services and the emergence of the Internet of Things (IoT) pose challenging requirements for the next-generation vehicular networks. Such challenges are largely related to high spectral efficiency and low latency requirements in the context of massive content delivery and increased connectivity. In this respect, caching and non-orthogonal multiple access (NOMA) paradigms have been recently proposed as potential solutions to effectively address some of these key challenges. In this paper, we introduce cache-aided NOMA as an enabling technology for vehicular networks. In this context, we first consider the full file caching case, where each vehicle caches and requests entire files using the NOMA principle. Without loss of generality, we consider a two-user vehicular network communication scenario under double Nakagami $\text{-}m$ fading conditions and propose an optimum power allocation policy. To this end, an optimization problem that maximizes the overall probability of successful decoding of files at each vehicle is formulated and solved. Furthermore, we consider the case of split file caching, where each file is divided into two parts. A joint power allocation optimization problem is formulated, where power allocation across vehicles and cached split files is investigated. The offered analytic results are corroborated by extensive results from computer simulations and interesting insights are developed. Indicatively, it is shown that the proposed caching-aided NOMA outperforms the conventional NOMA technique. [ABSTRACT FROM AUTHOR]

Interference alignment (IA) is a promising technique for interference management in wireless networks. On the other hand, jamming is a potential threat to wireless communications, which can degrade the performance of IA-based networks severely. Although some excellent work has been done on IA and antijamming, these two important aspects have traditionally been addressed separately in most previous work. In this paper, we study the antijamming issues and propose two antijamming schemes for IA-based networks. In the first scheme, the jamming signal and interferences are aligned into the same subspace at each receiver, and thus, can be perfectly eliminated together. When the requirement of perfect alignment can be relaxed, the second scheme is proposed to further improve the antijamming performance by maximizing the received signal-to-interference-plus-noise ratio (SINR). We derive the proper and feasibility conditions of the proposed two schemes. Simulation results are presented to show the effectiveness of the proposed schemes in mitigating jamming signals in IA-based wireless networks. [ABSTRACT FROM PUBLISHER]

This paper investigates the performance of a cognitive hybrid satellite–terrestrial network, where the primary satellite communication network and the secondary terrestrial mobile network coexist, provided that the interference temperature constraint is satisfied. By using the Meijer-G functions, the exact closed-form expression of the outage probability (OP) for the secondary network is first derived. Then, the asymptotic result in a high-signal-to-noise-ratio (SNR) regime is presented to reveal the diversity order and coding gain of the considered system. Finally, computer simulations are carried out to confirm the theoretical results and reveal that a more loose interference constraint or heavier shadowing severity of a satellite interference link leads to a reduced OP, whereas stronger satellite interference power poses a detrimental effect on the outage performance. [ABSTRACT FROM AUTHOR]

This paper proposes a cyber-physical framework consisting of the secure and privacy-preserving distributed impulsive-based estimator (DIE) algorithm and the local nonlinear control (LNC) algorithm to solve the cooperative formation tracking problem of networked marine surface vehicles (NMSVs) with sampled-data interactions and external disturbances. In the cyber layer, a secure and privacy-preserving information exchange scheme is proposed based on the Paillier cryptosystem such that the states of the virtual leader can be estimated in a secure and privacy-preserving way. In the physical layer, the LNC algorithm is designed with the utilization of the estimators in the cyber layer to achieve the formation tracking for the NMSVs with disturbance rejection ability. Sufficient conditions for guaranteeing the convergence and the stability of the closed-loop system are derived based on systematic analysis. Finally, numerical simulations are performed on Cyber-Ships II to verify the effectiveness of the main results. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the problem of joint design of the transmit and receive beamforming weight vectors for multiple-input multiple-output (MIMO) radar systems in the presence of signal-dependent interference, which is distinct from its existing counterparts focusing on joint design of the temporal codes of transmit waveforms and spatial-temporal receive filter. The design problem is formulated as output signal-to-interference-plus-noise ratio (SINR) maximization subject to a similarity constraint on the transmit beamforming weight, such that a good transmit beampattern can be guaranteed. Due to the existence of signal dependence, the resultant problem is NP-hard, and therefore, an iterative scheme is devised. Specifically, in each iteration, the receive beamforming is optimized with the minimum variance distortionless response method, then the transmit beamforming is obtained via the semidefinite relaxation (SDR) technique. It is proved that the proposed SDR-based algorithm is able to produce a rank-one solution. Numerical simulations are provided to demonstrate the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Of the wide palette of 5G features, ultra-wide bandwidth and large-scale antenna configuration are regarded as the essential enabling technology components for millimeter wave (mmWave) communication. Accurate knowledge of delay and angle information of multipath components is essential for many applications in mmWave systems. There is a strong need for a low computation-cost channel estimation algorithm for such systems, where typically adopted far-field and narrowband assumptions might be violated. In this paper, a generic yet novel beamspace uniform circular array (UCA) beamforming algorithm with successive cancellation scheme is proposed to jointly detect the impinging azimuth angle and delay of each multipath component. The proposed algorithm is computationally cheap and it works for ultra-wideband UCA systems in the near-field conditions as well as the traditional narrowband systems in the far-field conditions. Both numerical simulations and experimental validation results are provided to demonstrate the effectiveness and robustness of the proposed algorithm, compared to the state-of-art works. [ABSTRACT FROM AUTHOR]

Caching at base station is a promising technology to reduce the backhaul loads in future wireless networks. To exploit the content diversity gain and multiple antenna transmission, in this paper, we consider the analysis and optimization of random caching in multi-antenna small-cell networks with limited backhaul. We analyze the performance of the success probability, which is defined as the probability that the requested file is not only obtained from the cache or the backhaul at the small base station (SBS), but also successfully delivered via the wireless link from the SBS to the user. Using tools from stochastic geometry, we first derive an exact expression and an upper bound of the success probability. Based on the analytical results, we then consider network throughput maximization by optimizing the design parameters in the cache-enabled multi-antenna small-cell networks. The optimization problem is a complicated mixed-integer optimization problem. After analyzing the optimal properties, we obtain a local optimal solution with low complexity. To further simplify the optimization, we solve an asymptotic optimization problem in the high user density region, using the upper bound as the objective function. Numerical simulations show that our proposed scheme improves the performance by up to $14\%$ when the Zipf parameter is 0.4 and the antenna number is 8. [ABSTRACT FROM AUTHOR]

We consider a cognitive radio system, in which a secondary transmitter harvests energy from a primary transmitter's RF signal. The secondary transmitter, which provides decode-and-forward relaying service for the primary system, transmits its own data by using downlink non-orthogonal multiple access (NOMA). A time-switching protocol is used by the secondary transmitter to harvest energy and decode the primary transmitter's information. Our objective is to achieve maximal secondary throughput, by optimally selecting the time portion used for energy harvesting and the secondary transmitter's power allocation in NOMA transmission. In this paper, two optimization problems are formulated, in which the secondary receiver performs or does not perform successive interference cancellation (SIC), respectively. Although the two problems are nonconvex, we devise a method to transform the problems into equivalent problems under different cases. Then, we theoretically prove that the objective functions of the equivalent problems are quasiconcave, based on which we develop two-level bisection search algorithms to solve the equivalent problems. Interestingly, we show that performing SIC at the secondary receiver does not always guarantee a higher secondary throughput than the case without performing SIC. Computer simulation demonstrates that our algorithm performs better than an equal power allocation algorithm and an orthogonal multiple access algorithm. [ABSTRACT FROM AUTHOR]

Considering that wireless unidirectional full-duplex (FD) transmission is one of the FD transmissions over 5G mobile wireless networks, this paper proposes a joint receive and transmit relay beamformer design for systems consisting of a source, a FD relay, an intended destination, and an eavesdropper. The source and destination are single-antenna nodes, whereas the FD relay is a multi-antenna node. Assuming that full channel state information (CSI) is available and the eavesdropper processes two blocks of received data at a time, the joint optimization problem is reformulated as a semidefinite relaxation (SDR) problem (in terms of relay transmit beamformer), which is tight in the sense that the rank-one beamformer can always be recovered from the SDR solution. In order to significantly minimize the computational cost of the SDR implementation, a novel semi-analytical approach based on dual optimization is proposed to obtain the optimum transmit beamformer. When the number of data blocks is arbitrary, we propose a successive convex approximation approach for solving the original non-convex optimization problem and show that a stationary solution can be efficiently obtained. We then propose a distributionally robust beamformer design for the case of an arbitrary number of blocks, assuming that the means and covariance matrices of the eavesdropper's channels are known. Computer simulations show that the proposed semi-analytical solution matches with that obtained from numerical optimization of the SDR problem, the FD scheme significantly outperforms its half-duplex counterpart, and the proposed robust design provides robustness against CSI uncertainty. [ABSTRACT FROM AUTHOR]

In this paper, a novel scheme is proposed to optimize the effectiveness of the device-to-device (D2D) enabled vehicular communications (D2D-V), which are underlaid in cellular networks, where the uplink channel allocated to one cellular user (CU) is reused by the multiple D2D-V links. To develop a well-functioning D2D-V system, the sum rate of all D2D-V links is necessary to be maximized, and also the reliability of the co-channel CU to infrastructure has to be guaranteed with the CU interference constraint. Unlike the traditional statical D2D systems, the D2D-V system suffers with high mobility and channel uncertainty. Therefore, the CU interference constraint is formulated as a probabilistic function by the Bernstein approximation, the constraint attempts to address the mobile channel fluctuations. Besides, the tractable approximate constraint is reformulated as two separable structure, this reformulated constraint attempts to determine the near-optimal solutions more efficiently. Since the objective function with a logarithmic form is nonconvex, successive convex approximation is applied to transform the nonconvex problem into the convex problem. The dual decomposition is used to determine the near-optimal solutions. After the problem is reformulated, a distributed robust power control algorithm is proposed to perform the chance-constrained optimization. Numerical simulations are used to evaluate the performance of the proposed scheme. The simulation results show the impacts of system performance when applying the proposed scheme in vehicular environments with high mobility. The proposed optimization schemes are further verified by comparing with the existing methods. [ABSTRACT FROM AUTHOR]

Misuse of vehicle horns by irresponsible drivers can be a source of noise pollution. The first step in eliminating such misuse is to monitor horn use in order to identify the culprit. This paper reports the development of an effective overhead honking monitoring system for this purpose. Integrating techniques of sensor array, time sequence analysis, sound source localization, and data fusion, this proposed system recognizes the sound of vehicle horn, determines the position of the sound-emitting vehicle, and visualizes it in an image captured by the road monitoring camera. The performance of this proposed system has been evaluated via experiments conducted under different typical urbane scenarios. [ABSTRACT FROM AUTHOR]

This paper proposes a new algorithm to evaluate the performance of the mobile edge computing system. Specifically, a new metric called computation efficiency is defined as the number of calculated data bits divided by the corresponding energy consumption. In order to compute the required data timely, we combine two schemes, local computing and data offloading, into a joint computation algorithm. An optimization problem is formulated with the objective to maximize the sum of computation efficiency among users with weighting factors. With iterative and gradient descent methods, the problem can be solved efficiently. Simulation results show that the proposed scheme outperforms traditional approaches. In addition, the tradeoff study between local computing and data offloading reveals that when data size is small, local computing plays a more important role, but when the size grows, data offloading becomes preferable. [ABSTRACT FROM AUTHOR]

In this paper, we investigate cooperative spectrum sensing (CSS) in a cognitive radio network (CRN) where multiple secondary users (SUs) cooperate in order to detect a primary user, which possibly occupies multiple bands simultaneously. Deep cooperative sensing (DCS), which constitutes the first CSS framework based on a convolutional neural network (CNN), is proposed. In DCS, instead of the explicit mathematical modeling of CSS, the strategy for combining the individual sensing results of the SUs is learned autonomously with a CNN using training sensing samples regardless of whether the individual sensing results are quantized or not. Moreover, both spectral and spatial correlation of individual sensing outcomes are taken into account such that an environment-specific CSS is enabled in DCS. Through simulations, we show that the performance of CSS can be greatly improved by the proposed DCS. [ABSTRACT FROM AUTHOR]

The performance of wireless systems and transmission technologies is ultimately limited by radio channels. This paper characterizes multi-link multiple-input multiple-output (MIMO) channels for future high-speed train (HST) communication systems. The channel characterization is based on field measurements in a dedicated long-term evolution (LTE) network along a high-speed railway line of China. The raw channel data are collected by an LTE sounder with two antenna ports in the multi-link region between neighboring remote radio units of the network, which are further processed by a time-delay-window-based partitioning approach to acquire multi-link MIMO channel impulse responses. Before investigating the multi-link channel properties, MIMO channel characteristics for each single link in a plain viaduct scenario are analyzed and compared in terms of root mean square angular spread and spatial correlation. Then, the dual-link MIMO channel characteristics, such as correlation matrix collinearity and sum rate capacity, are newly presented and discussed. These results can provide the reference for realistic performance assessment of cooperative MIMO HST communication systems. [ABSTRACT FROM AUTHOR]