• Wireless Networks (IF 2.405) Pub Date : 2020-02-18

Abstract Vehicular ad hoc networks (VANETs) are able to facilitate data exchange among vehicles and provide diverse data services. The benefits of cooperative communications are such as to make it a proper idea to improve the achievable rate and diversity in VANETs. We investigate a dual-hop relay vehicular network with different transmit powers in vehicles on non-uniform shadowed double Nakagami-m fading channels in the presence of non-uniform co-channel interferers. In this paper, we investigate the diversity-multiplexing tradeoff (DMT) in such a network for three different schemes, namely, dynamic decode and forward (DDF), dynamic quantize map and forward and static quantize map and forward and prove that the DDF strategy has the optimal DMT. Also, the optimal listening and transmitting time of vehicles in various strategies as a function of the channel conditions in vehicles are determined. Finally, we extend our results to a general multi-hop relay vehicular network model with multiple half-duplex relay terminals and different average SNRs over links.

更新日期：2020-02-18
• Wireless Networks (IF 2.405) Pub Date : 2020-02-18
Huibin Jia, Yonghe Gai, Dongfang Xu, Yincheng Qi, Hongda Zheng

Abstract Large-scale natural disaster or malicious attacks could cause serious damages to the communication network in smart grids. If the damaged network cannot be recovered timely, greater threat will be brought to the secure and stable operation of smart grids. In this paper, a link importance-based network recovery method for large-scale failures in smart grids has been proposed. Firstly, the link importance for the network can be obtained according to the link importance for the service type and the importance of the service type for the network; secondly, a network recovery model, which is 0–1 integer programming, has been established to recover more important communication services with limited recovery resources; finally, we propose a heuristic algorithm to solve the problem and reduce the computational expenditure. The simulation experiments are carried out to evaluate the performance of the proposed algorithm. The simulation results illustrate that our network recovery method is applicable to the large-scale failures and the link which carries the high-priority service can be first recovered in this paper, thus which further ensures the safe and stable operation of smart grids.

更新日期：2020-02-18
• Wireless Networks (IF 2.405) Pub Date : 2020-02-17
Madiyar Nurgaliyev, Ahmet Saymbetov, Yevhen Yashchyshyn, Nurzhigit Kuttybay, Didar Tukymbekov

Abstract This paper shows a method for predicting the lifetime of a wireless sensor network based on the LoRa Ra-01 wireless modules. To develop a prediction model of the energy consumption, wireless sensor modules were assembled and it was obtained experimental data using LabView development environment. There were performed experiments to get battery discharge curve. Experimental data of power consumption depending on the packet length were obtained in transmission mode. Using experimental data, we obtained dependencies of system lifetime on sleep mode duration and packet length. The paper also considered a probabilistic approach to predict the system lifetime depending on the probability of data transmission during the day. The lifetime prediction model is based on Markov’s chains. The results obtained in this work can be used to predict lifetime of sensor networks more accurately.

更新日期：2020-02-18
• Wireless Networks (IF 2.405) Pub Date : 2020-02-15
Miroslava Trembošová, Alena Dubcová, Ľudmila Nagyová, Dagmar Cagáňová

Abstract The main aim of this paper is to show the specifics of the retail network of three regional towns in the Slovak Republic—Nitra, Trnava and Žilina, and answer the following question: What value of the Population to the Admissible Floor Space (PAFS) indicator will cause saturation of the retail network? The situation of the retail network of the examined towns from 2015 was compared by using the standard methods based on the indicators from detailed passportisation of the retail facilities in the terrain. The indicators are: amount and assortment structure of the stores, sales area size, PAFS and concentration index at the level of the town districts. Based on the result of the comparison, regularities of space structure formation of the retail amenities of the mentioned towns in Slovakia were identified and their features were pointed out. According to the survey results, the size of sales area is the clear indicator of the retail network evaluation. The sales area size defines the following changes in the best detail, and it appears as the most suitable tool for the analysis. However, in this case, more thorough and detailed passportation is needed. Saturation stage was identified only in Nitra, where it was identified after the year 2010. This process has not occurred yet in other two region towns. Quantitatively new stage called: “The stage gradually flowing “purification” of the retail network from the excessive sales area” is expected to start in the Nitra town.

更新日期：2020-02-18
• Wireless Networks (IF 2.405) Pub Date : 2020-02-14
Anurag Shukla, Sarsij Tripathi

Abstract The effectiveness of wireless sensor network (WSN) in Internet of Thing (IoT) based large scale application depends on the deployment method along with the routing protocol. The sensor nodes are an important component of WSN-assisted IoT network running on limited and non-rechargeable energy resource. The performance of WSN-assisted IoT is decreased, when network is deployed at large area. So, developing robust and energy-efficient routing protocol is a challenging task to prolong the network lifetime. In contrast to the state-of-the-art techniques this paper introduces Scalable and energy efficient routing protocol (SEEP). SEEP leverages the multi-hop hierarchical routing scheme to minimize the energy consumption. To achieve scalable and energy efficient network, SEEP employs a multi-tier based clustering framework. The network area in SEEP is divided into various zones with the help of proposed subarea division algorithm. The number of zones in the network are increased as the network size increases to avoid long-distance communication. Every zone is divided into certain number of clusters (sub-zones) and the number of clusters are increased towards the base station, whereas the zone width is decreased. In every cluster, some of the optimal nodes are promoted as a Relay Node (RN) and Cluster Head (CH). Normal nodes send their sensed data to the base station via local RN and CH in a multi-hop way. Furthermore, propose protocol provides a trade-off between distance and energy to prolong the network lifetime. In the proposed framework, static and mobile scenarios have been considered by applying Random walk and Random waypoint model for node mobility in simulation to make it more realistic as the various application of WSN-assisted IoT. The effectiveness of SEEP is examined against LEACH, M-LEACH, EA-CRP, TDEEC, DEEC, SEP, and MIEEPB, and result indicates that SEEP performs better for different network metrics: network lifetime, scalability, and energy efficiency.

更新日期：2020-02-18
• Wireless Networks (IF 2.405) Pub Date : 2020-02-14
Rui Zhou, Xiang Lu, Yang Fu, Mingjie Tang

Abstract Crowd counting is of great importance to many applications. Conventional vision-based approaches require line of sight and pose privacy concerns, while most radio-based approaches involve high deployment cost. In this paper, we propose to utilize WiFi channel state information (CSI) to infer crowd count in a device-free way, with only one pair of WiFi transmitter and receiver. The proposed method establishes the statistical relationship between the variation of CSI and the number of people with deep neural networks (DNN) and thereafter estimates the people count according to the real-time CSI through the trained DNN model. Evaluations demonstrate the effectiveness of the method. For the crowd size of 6, the counting error was within 1 person for 100% of the cases. For the crowd size of 34, the counting error was within 1 person for 97.7% of the cases and within 2 persons for 99.3% of the cases.

更新日期：2020-02-14
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-17
Tommaso Rossi; Mauro De Sanctis; Fabio Maggio; Marina Ruggieri; Craig Hibberd; Cristina Togni

The short-term scenarios of high-throughput satellite systems foresee the exploitation of (currently commercially unused) extremely high frequency bands in the feeder link to support broadband user access services. In this context, spatial diversity plays a key role, considering that this is the only technique that can allow high link availability at frequency bands higher than the Ka-band without requiring very high link margins, which results in a waste of system resources. In this framework, the most promising spatial diversity technique is the so-called smart gateway (SG) diversity. This paper focuses on the optimization of the SG technique following operator perspectives and needs. In particular, a design approach for the optimization of the SG architecture is proposed, which allows to select the best SG configuration (spare capacity, number of gateway groups, number of gateways in each group, geographical position of gateways in each group) given a set of constraints (geographical position of all available gateways, longitude of the GEO satellite, characteristics of satellite/ground terminals, system availability). Moreover, a practical case of SG diversity optimization is presented as a reference to guide the reader in the SG optimization process.

更新日期：2020-02-14
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-20
Sayed Jalal Zahabi; Mohammad Mahdi Naghsh; Mahmoud Modarres-Hashemi; Jian Li

We propose a compressive pulse-Doppler radar that works through one-bit quantization of the received noisy signal by comparing it with a time-varying reference level. Considering the sparsity of the targets in the range-Doppler domain, we solve the problem by sparse recovery methods in both the absence and presence of clutter. The proposed method leads to an optimization problem that can be tackled by a convex approximation. Numerical examples confirm the effectiveness of the proposed method.

更新日期：2020-02-14
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-17
Arti M. K.

We investigate the problem associated with the statistics of the product of two squared Shadowed Rician (SR) random variables (RVs). Both SR RVs are independent and nonidentically distributed. The distribution of the product of two squared SR RVs is very important from the satellite communication perspective. We derive approximate expressions of the probability density function (p.d.f.), the moment generating function (m.g.f.), and the cumulative distribution function (c.d.f.) in terms of Meijer-G functions. Furthermore, exact closed-form expressions for higher order moments, channel quality estimation index, and amount of fading are derived. The outage probability is also discussed by utilizing the expression of the c.d.f. An approximate closed-form expression of channel capacity is also derived with the help of the p.d.f. expression. Furthermore, the performance of satellite communication system is discussed in terms of the approximate symbol error rate by using the derived results. Specifically, the derived expression of the p.d.f. is used to develop an approximate closed-form expression of the m.g.f. for an amplify-and-forward-based satellite communication system.

更新日期：2020-02-14
• Wireless Networks (IF 2.405) Pub Date : 2020-02-13
Martin Straka, Martin Hricko

Abstract The article deals with the problem of research of software solutions of efficiently layout of material within a defined space for the needs of production storages and transport. The problem relates to using knowledge with branches of logistics, layout, math and geometry for needs of research and for needs the creation of an expert system of materials layout as the software application. Similar systems do not occur in the market for the needs of practice. The aim of the article is to point out the principles, which is necessary to take into account in the research of an expert system of materials layout. Final implementation of the goal consists of the idea to achieve a logistic computer system design, focused on the effective use of loading areas, combined with an aesthetic, comfortable and logically moulded outlet as a possible realistic graphic illustration of the desired result. This part refers to the object-oriented programming language, mainly because of its object-oriented features, such as polymorphism, or templating. The results of the program solution show an improvement in the utilization of the loading area of the means of transport by up to 30%.

更新日期：2020-02-13
• Wireless Networks (IF 2.405) Pub Date : 2020-02-12
Basabdatta Palit, Suvra Sekhar Das, Yughandhar Kamavaram

Abstract In this paper, we present an analytical framework for the performance evaluation of a pre-emptive priority scheduler in multi-resource networks, like those using Orthogonal Frequency Division Multiple Access (OFDMA). We focus on Quality of Service (QoS)-guaranteed traffic for which QoS is guaranteed to individual users by restricting the number of admitted users. For this, the QoS-constrained capacity, in terms of the number of supported users, needs to be ascertained a priori. The QoS-constrained capacity is a function of users’ QoS requirements, channel conditions, and radio resource allocation algorithms, which in this work is the pre-emptive priority scheduler. It is, thus, a variable quantity and mostly obtained using time-consuming offline computer simulations. Mathematical models, on the other hand, are timely and accurate, allowing the capacity to be derived in real-time as a function of the current network configuration. Existing works on mathematical modelling of pre-emptive priority schedulers have mostly focussed on single servers or multiple servers where a single server is assigned to each user. In contrast, OFDMA networks have multiple radio resources, i.e., multiple servers and each user may need more than one radio resource for a single packet transmission, i.e. it is a multi-resource system, which has been accounted for in this paper. We classify the users based on their resource requirements and model the pre-emptive priority scheduler as a multi-class, multi-server, multi-resource, non-work conserving queueing system. We derive its QoS metrics like average delay, packet drop probability, throughput, etc., from its continuous-time Markov Chain. We then use the derived QoS metrics to obtain the QoS-constrained capacity and design a threshold based predictive call admission control unit. We have validated the results using extensive discrete event simulations.

更新日期：2020-02-13
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-02-27
Shenghong Li; Mark Hedley; Iain B. Collings; David Humphrey

The performance of a range-based indoor positioning system is severely degraded by non-line-of-sight (NLOS) propagation due to the offsets in range measurements (i.e., NLOS errors). It is difficult to predict or mitigate the NLOS errors since they are dependent on both the location and the environment. In this paper, we propose an accurate tracking scheme for NLOS environments by jointly estimating the target's trajectory and the NLOS errors based on the fusion of sensors that measure the motion of the target. We first formulate a maximum a posteriori (MAP) estimation problem with generic equality constraints that capture the spatial correlation of NLOS errors. A specific constraint function based on Gaussian process (GP) regression is then provided, and an iterative algorithm is proposed to solve the optimization problem. The proposed scheme is validated experimentally in an indoor positioning system with 125 MHz bandwidth using a mobile node equipped with an inertial measurement unit. It is shown that the median positioning error in an office environment is reduced by 90% to 11 cm compared to using conventional tracking algorithms.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-07-22
Zhengqiang Zhong; Lei Xu; Jiuping Xu

In this paper, an integrated system health management oriented condition monitoring and maintenance decision-making model is proposed, which uses intelligent mobile agents to achieve real-time monitoring and to realize life cycle maintenance decision-making for multistate systems (MSSs). The model is applied to an aircraft engine system numerical example, the results of which illustrate that the proposed system and model have the ability to provide efficient and accurate engine system maintenance decision-making information and provide detailed health condition information. The feasibility of the proposed system and model is demonstrated and MSS frequent maintenance decisions are recorded and revealed.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-07-22

Random jitter or offset between the transmitter/receiver clocks is an important parameter that has to be accurately estimated for optimal detection of pulse position modulation (PPM) symbols for high-data-rate optical communications. This parameter, in general, is modeled as an unknown random quantity that depends on the clock drift between the transmitter/receiver clocks and the random motion between the transmitter and receiver stations. In this paper, we have modeled the time jitter for two scenarios—phase modulation jitter and frequency modulation jitter. The phase modulation jitter is modeled as a Gaussian random variable which is estimated with the help of a maximum a posteriori probability (MAP) estimator. The frequency modulation jitter is characterized as a random walk, and this leads to the modeling of the jitter as a state space variable in the context of a dynamical system. Since the observations are the photon counts in each slot of a PPM symbol (for both MAP estimation and tracking), the resulting dynamical model is highly nonlinear, and particle filters are employed for tracking the frequency modulation jitter. We evaluate the performance of both the maximum a posteriori estimators and the particle filters in terms of the relative mean-square error and probability of error. We conclude that with MAP estimation and particle filters that estimate/track the time offset, we achieve a significant performance gain in terms of probability of error as compared to systems that do not have a time synchronization system in place.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-04-11

We present an optimal control method for distance-based formation control of multiagent systems with energy constraints. We combine the rigid graph theory and state-dependent Riccati equation method to develop a multiagent formation control scheme. We defined a normalized rigidity matrix and use it for the rigorous stability analysis. The proposed method asymptotically minimizes weighted cost functional that includes formation and energy consumption costs. Furthermore, we propose a solution for the global asymptotic stability and collision avoidance. Simulation results illustrate the effectiveness of the proposed method in two- and three-dimensional spaces.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-04-15

A new algorithm, the finite-difference algorithm, is proposed for single-component polynomial phase signal parameter estimation. The proposed algorithm takes advantage of the framework of the quasi-maximum-likelihood (QML) estimator but estimates the finite difference of the polynomial instead of the derivative. The algorithm is computationally simpler and has comparable performance to the QML algorithm. A phase centering step is proposed to increase the detectable range of polynomial phase parameters as an alternative to phase unwrapping.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-21
Wei Cui; Jing Tian; Xiang-Gen Xia; Si-Liang Wu

To compensate the range cell migration and Doppler frequency spread of a maneuvering target during the integration time, this paper proposes a new parameter estimation method based on sub-band dual-frequency conjugate (SDFC)–Radon chirp rate–quadratic chirp rate algorithm. In this method, SDFC process is first applied to reduce the equivalent frequency and Radon chirp rate–quadratic chirp rate algorithm is then performed to obtain the estimates. Both simulated and real-data results demonstrate the effectiveness of the proposed algorithm.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-04-17
Seok-Kyoon Kim; Choon Ki Ahn

This paper presents a nonlinear tracking controller including the cutoff frequency adaptation algorithm for quadcopters without the use of true plant parameters. This study makes two contributions. First, an adaptation algorithm automatically updates the closed-loop cutoff frequency by updating the feedback gains. Second, a nonlinear control law renders the closed-loop system to guarantee the exponential performance recovery and offset-free properties, while only using the proportional component of tracking errors. The numerical verifications are performed to verify the closed-loop performance improvement from the proposed controller with MATLAB/Simulink.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-08
Antonio Augusto da Fontoura; Francisco Assis Moreira do Nascimento; Simin Nadjm-Tehrani; Edison Pignaton de Freitas

Reconfigurable avionics systems can tolerate faults by moving functionalities from failed components to another available system component. This paper proposes a distributed reconfigurable architecture for application migration from failed modules to working ones. The feasible system reconfiguration states are determined off-line to provide the expected configuration in foreseen situations. Model checking is used to determine feasible configurations evaluating specific temporal properties. A case study is used to show the application of the presented approach as a proof of concept.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-04-17
Jungmin Park; Yong-gonjong Park; Chan Gook Park

In this paper, we present an expectation-maximization (EM) initialization method for estimation of unknown parameters in a radar noise model. We deal with radar based terrain referenced navigation (TRN) over vegetated areas, where the radar noise was modeled as a double-mode Gaussian mixture with two unknowns. The known parameters are used for EM initialization along with innovation samples. Through TRN simulation, it is shown that the proposed EM initialization method outperforms random or k-means initialization methods in terms of both the parameter estimation error and the vehicle position error.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-03

This paper proposes an impulse radio ultrawideband (IR-UWB) wireless network channel model for next-generation wireless avionic system (NGWAS). Complexities such as poor network localization, redundant wiring, network security flaws, suitable physical proximity to the aircraft system's controller and need to guarantee scalable wireless network access have necessitated the adoption of wing system units of a passenger aircraft for this scheme's deployment. The proposed IR-UWB approach aims at alleviating the attendant drawbacks by selecting optimal channel path from available paths on the basis of bit error rate (BER), based on the numerical results obtained from the Saleh–Valenzuela (S-V) principle. Cooperative relay transmission schemes factored upon transmission power, overall outage probability and spectral-energy efficiency tradeoffs for the relay network communication were also investigated and compared with the noncooperative schemes. Simulation results validate maximum data packet delivery while a strong network signal strength is attained. Comparative approach of the performances of the IR-UWB standardized channel models are also evaluated.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-04-17
Julian J. Lopez-Salamanca; Laio Oriel Seman; Marcelo D. Berejuck; Eduardo A. Bezerra

This paper proposes a channel model to be applied to the communications systems of CubeSats. The model considers the low earth orbit geometry when a satellite is passing over a ground station, and the propagation surrounding multiple paths of the ground station location in urban areas. The geometry was used to define the deterministic factors, which contribute to the fading of the communication signal, such as Doppler effect and loss in free space. These are parameters that change as a function of time and elevation angle. Thus, a complete digital communication system, at the link layer level, is presented, using Markov Chains to model the previously cited effects in the form of a finite-state Markov channel. The proposed model was used as an uplink channel between a ground station and a CubeSat, both implementing a protocol stack, following the consultative committee for space data systems (CCSDS) recommendations. The ground station and the proposed communication channel were implemented through a functional simulation model and a telecommand and telemetry unit, implemented in hardware, was used as a case study for the CubeSat. Through the analysis of the simulated system, with telecommands sent by the station and responses sent by the hardware unit (in a hardware-in-the-loop setup), it was possible to demonstrate the operation of the proposed channel together with the retransmission mechanism suggested in the CCSDS recommendations, in order to mitigate communication issues.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-08
Marco Aurélio Carvalho; Nelson Paiva Oliveira Leite; Roberto d'Amore

A reliable telemetry link is a key element to reduce reflies and to enhance test flight efficiency (i.e., real-time test point validation) and safety in flight test campaigns. However, the telemetry link undergoes losses owing to radio frequency noise and flight test maneuvers. In addition, the telemetry community has been facing a reduction of the available bandwidth owing to electromagnetic spectrum auctions. Many methods have been presented to solve these problems; however, no conclusive solution has been obtained. In view of these issues and by focusing on flight test requirements, IPEV, an Air Force Flight Test Center, proposed an integrated pulse code modulation (iPCM) Telemetry protocol as a potential solution to vital matters regarding the reliability and bandwidth of telemetry links. This paper presents the iPCM architecture and the ground and flight test results. Test results demonstrated the iPCM's capability to recover corrupted data and ensure data integrity and reliability. In a flight test, 100% of the data was successfully retrieved by iPCM without any noise and loss compared with the 98.24% received by PCM IRIG-106. Similarly, for the ground test results, 100% of the data was retrieved successfully by iPCM, and only 88.45% by PCM. In addition, the iPCM protocol provides an option to dynamically select an Flight Test Instrumentation parameter list to be transmitted. In a typical test scenario, this feature of frame changing in the parameter list can achieve a 65% reduction in the bandwidth usage in comparison with PCM IRIG-106.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-04-17
Ignacio Torralbo; Isabel Pérez-Grande; José Luis Gasent-Blesa; Javier Piqueras; Esteban Sanchis-Kilders; Pedro Rodríguez; Antonio López

This paper presents the thermal design of the electronics unit of the instrument Polarimetric Helioseismic Imager, onboard the European Space Agency mission Solar Orbiter. The thermal design procedure, along with the problems encountered during this design phase, and the solutions found to fix them are described, proving in this way the thermal feasibility and robustness of the unit. Its final thermal behaviour, obtained from thermal analyses correlated with data from thermal tests performed in a vacuum environment, is presented.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-04-29
Jae-Won Rim; Il-Suek Koh

By employing an expendable repeater-type decoy that is known as efficient electronic countermeasure device, the survivability of an airborne platform can be improved. To optimize the survivability of the aircraft by managing the active decoy, analyzing which factors critically affect to the survivability is very important. For its dynamic situation, where the motions and interaction of the decoy, platform, and missile varied with respect to time, a modeling and simulation (M&S) approach is preferred, which can consider other factors: radio frequency specification of decoy, guidance model of the missile, and so on. Based on the proposed M&S approach, several crucial factors affecting to the survivability of the platform such as platform reaction range, platform maneuvering, decoy dynamics, missile's maximum load factor, etc., are addressed and numerically analyzed. Additionally, the survival probability of the platform is also simulated on several engagement scenarios through the Monte Carlo simulation.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-06-04
Karl Granström; Maryam Fatemi; Lennart Svensson

This paper presents a Poisson multi-Bernoulli mixture (PMBM) conjugate prior for multiple extended object filtering. A Poisson point process is used to describe the existence of yet undetected targets, while a multi-Bernoulli mixture describes the distribution of the targets that have been detected. The prediction and update equations are presented for the standard transition density and measurement likelihood. Both the prediction and the update preserve the PMBM form of the density, and in this sense, the PMBM density is a conjugate prior. However, the unknown data associations lead to an intractably large number of terms in the PMBM density, and approximations are necessary for tractability. A gamma Gaussian inverse Wishart implementation is presented, along with methods to handle the data association problem. A simulation study shows that the extended target PMBM filter performs well in comparison to the extended target $\delta$ -generalized labelled multi-Bernoulli and LMB filters. An experiment with Lidar data illustrates the benefit of tracking both detected and undetected targets.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-04-29
Nertjana Ustalli; Debora Pastina; Pierfrancesco Lombardo

This paper is devoted to the estimation of target motion parameters with a forward scatter radar (FSR). To provide an upper bound for the estimation performance, a closed-form expression of the Cramér–Rao lower bound (CRLB) is provided for the main target signal parameters, namely Doppler rate, baseline crossing instant, and main lobe width parameter of the target amplitude modulation pattern. This is performed by operating on the signal at the output of the standard FSR processing scheme, namely on the crystal video detector signal: the received signal, which is passed through a square-law envelope detector followed by a DC removal filter. The estimate of the kinematic parameters of moving targets that follow a linear trajectory can be obtained by inverting the relationship between these parameters and the previously estimated target signal parameters. Especially, two FSR configurations are investigated: single-node FSR configuration and dual-baseline FSR configuration with a small angular separation between the two baselines. The closed-form expression of the corresponding CRLB is derived by using a linearized version of the same inverse transformation. Finally, a practical estimator is presented, based on a two-dimensional filter bank, and its performance is compared with the derived CRLB. The results show that unbiased and highly accurate estimates of the kinematic parameters are obtained. The feasibility and the effectiveness of this estimation scheme is demonstrated by applying this technique to recorded live data acquired with a dual-baseline FSR configuration exploiting FM signals as a waveform of opportunity.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-08
Arthur Hsi-Ping Chu; Shubhendra Vikram Singh Chauhan; Grace Xingxin Gao

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-08
Shulei Gong; Hong Shen; Kanglian Zhao; Wenfeng Li; Haibo Zhou; Ruhai Wang; Zhili Sun; Xinggan Zhang

In this paper, we investigate the transmission schemes of space data systems for optimized network capacity in an integrated terrestrial-satellite network (ITSN) with a two-layered space segment. First, a theoretical model of the network capacity is developed to evaluate the strategy of utilizing both direct and relayed transmissions. Second, we consider the ideal and the resource-constrained scenarios in which the corresponding network capacity is modeled with respect to the scheduling scheme. In particular, closed form and semi-closed form solutions to difficult integer programs are achieved via rigorous mathematical analysis. The proposed model is general for exploring the capacity of various satellite network deployments whose solutions have not been obtained in prior studies. Furthermore, we verify the potential capacity of the different transmission schemes based on the proposed solutions and prove that the system's network capacity can be significantly improved by the hybrid transmission scheme. The theoretical framework proposed in this paper is expected to provide constructive insights in the design for the future space segments of ITSNs.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-03
Sébastien J. J. Généreux; Alvin K. H. Lai; Craig O. Fowles; Vincent R. Roberge; Guillaume P. M. Vigeant; Jeremy R. Paquet

Aircraft are becoming increasingly connected to other systems or networks, introducing attack vectors and posing a threat to their operational effectiveness. Many military aircraft function using the MIL-STD-1553 protocol in order to communicate information across its systems. Previous intrusion detection research on this type of data bus is unable to detect spoofing attacks where only data words are manipulated. This paper presents the design of a MIL-STD-1553 anomaly-based intrusion detection system able to identify those attacks through the use of a novel histogram comparison approach and time-based features. The approach includes optimizations for improved time resolution in threat identification. Results demonstrate the effectiveness of the approach in identifying threats quickly and accurately.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-02
Thomas Delamotte; Andreas Knopp

With sum throughputs exceeding 1 Tb/s, next-generation high throughput satellite will play a key role in 5G networks for applications including backhauling or broadband in-flight connectivity. Such satellites require the deployment of tens of $Q/V$ -band feeder links to support the data traffic in their uplink. Meanwhile, geographical restrictions and cost considerations significantly constrain the search for gateway deployment sites. Diversity strategies are, furthermore, necessary to cope with strong rain fades. In this paper, multiple-input-multiple-output (MIMO) feeder links are proposed to address these challenges. Using two active gateway antennas per feeder link, a MIMO-based solution enables to support twice the user link bandwidth per link compared to the state-of-the-art. On-ground and onboard processing strategies for such MIMO links are introduced, and the link outage probabilities are determined. An extension of smart diversity schemes to MIMO-based architectures is also presented to guarantee a sufficient robustness against rain fades. An analysis of the achieved uplink CINR demonstrates the superiority of the proposed concept and provides guidelines for an efficient design.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-04-17
Alexei E. Kolessa; Alexander G. Tartakovsky; Atner P. Ivanov; Vasily A. Radchenko

Typically, near-Earth space objects are observable for a small fraction of the orbit revolution. In this paper, we consider the problem of identification and fusion of two short optical tracks of near-Earth space objects, as well as the problem of estimation of the parameters of the corresponding orbits directly from these tracks in the absence of a priori information. The popular approach to solving these problems is based on admissible regions of orbital parameters, which is typically computationally demanding. It is shown that the solution of these problems does not require admissible regions and computationally and algorithmically difficult operations with admissible regions. A new, purely statistical method for solving these problems is proposed.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-20
Pawel Ladosz; Hyondong Oh; Gan Zheng; Wen-Hua Chen

This paper presents a learning approach to predict air-to-ground communication channel strength to support the communication-relay mission using the unmanned aerial vehicle (UAV) in complex urban environments. The knowledge of the air-to-ground communication channel quality between the UAV and ground nodes is essential for optimal relay trajectory planning. However, because of the obstruction by buildings and interferences in the urban environment, modeling and predicting the communication channel strength is a challenging task. We address this issue by leveraging the Gaussian process (GP) method to learn the communication shadow fading in a given environment and then employing the optimization-based relay trajectory planning by using learned communication properties. The key advantage of this learning method over fixed communication model based approaches is that it can keep refining channel prediction and trajectory planning as more channel measurement data are obtained. Two schemes incorporating GP-based channel prediction into trajectory planning are proposed. Monte Carlo simulations demonstrate the performance gain and robustness of the proposed approaches over the existing methods.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-09
Ke Ren; Lan Du; Baoshuai Wang; Quan Li; Jian Chen

Aiming at the signal reconstruction problem for the conventional narrowband radar system, we propose a new statistical compressive sensing (SCS) method to achieve the reconstruction of superresolution time-frequency spectrum from the corrupted time-domain measurement. The proposed method assumes that the signal obeys complex Gaussian distribution and develops a hierarchical Bayesian model. Variational Bayesian expectation maximization (VBEM) is used to perform inference for the posterior distributions of the model parameters. In order to fully exploit the superresolution characteristics of reconstructed spectrum, a novel superresolution time-frequency feature vector is extracted for subsequent classification of ground moving targets, i.e., walking person and a moving wheeled vehicle. Experimental results on measured data show that the proposed reconstruction method can obtain good reconstruction results and the superresolution feature has good classification performance for human and vehicle targets.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-20
Michael Kowalski; Peter Willett; Tim Fair; Yaakov Bar-Shalom

In target tracking systems involving data fusion it is common to encounter sensor measurement biases that contribute to the tracking errors. There is extensive research into estimating sensor biases, but very little research into bias estimation in the dynamic case, meaning that biases that change over time are addressed. This paper investigates the means for and necessity of estimating bias rates of change in addition to constant sensor biases to reduce the errors in the state estimates. This is explored by comparing the Cramér–Rao lower bound and root-mean-square error of simultaneous target state and bias estimates for rotational biases with three-dimensional passive sensors with roll, pitch, and yaw biases. The present work models the dynamic biases as linearly varying over time. The iterated least squares method is used for the search of the maximum likelihood estimate, and is shown to be statistically efficient via hypothesis testing.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-08
Andrew Robert Finelli; Yaakov Bar-Shalom

This paper deals with measurement extraction, from an optical sensor's Focal Plane Array (FPA), of a streaking target. We use a model that assumes pixels are separated by dead zones and model the streaking target's point spread function (PSF) as a Gaussian PSF that moves during the optical sensor's integration time. We make an assumption that the target has a constant velocity over the sampling interval and parametrize its motion with a starting and ending position. The noise model for a single pixel has variance proportional to its area, consistent with a Poisson model of the number of nontarget originated photons. We develop a maximum likelihood (ML) method of estimating the target motion parameter vector based on the set of pixel measurements from the optical sensor. This paper then derives the Cramer–Rao lower bound (CRLB) on the estimation error of the target motion parameter. We then present a matched filter (MF) based definition of the signal-to-noise ratio (SNR) to use as a basis for comparison of Monte Carlo simulation based location estimates to the calculated CRLB. It is shown that the ML estimator for the starting and ending positions of a streak in the FPA is efficient for MFSNR $\geq 12$ dB. We then provide a test statistic for target detection and propose approximate distributions to set the detection threshold for specific detection ( $P_D$ ) and false alarm probabilities ( $P_{\text{FA}}$ ), which are then verified via simulations. This paper's major contributions are the proposal of an ML/MF method for measurement extraction of streaking targets, confirmation that this method achieves the best accuracy possible for realistic FPA sensors, i.e., it attains the CRLB, the introduction of a statistically supported definition of SNR for these measurements, and an evaluation of the target measurement detection performance. Furthermore, this paper shows that, given our MFSNR definition, the streak length and direction of motion in the FPA have a negligible effect on performance compared to the SNR where we show that with a 4-dB change, the detection performance increases dramatically.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-04-29
Youeyun Jung; Seongheon Lee; Hyochoong Bang

Safe landing site selection of a planetary lander is one of the most important technologies for the lander's mission success. In this paper, a new concept for safe landing site selection is proposed based on the digital terrain map and contour lines generated by light detection and ranging (LIDAR) measurements. The design parameters of the proposed approach are defined and systematically classified. Then, the effect of key parameters related to the performance of the algorithm, i.e., terrain roughness is analyzed by comparing the results of three different types of terrain. The simulation results show that the proposed method is well-performed under various circumstances.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-08
Yafeng Li; Jorge Cervantes; Nagaraj C. Shivaramaiah; Dennis M. Akos; Meiling Wang

With GPS/Global Navigation Satellite System (GNSS) receivers exposed to greater levels of Radio Frequency Interference (RFI), a potential problem is the saturation of the receiver front end (FE). This problem is further complicated in typical multifrequency receivers by the interfrequency saturation effect. Specifically, any inband RFI targeted to induce FE saturation at only one specific GPS/GNSS frequency, if not properly handled, would potentially impact the reception of the other frequencies. This paper presents the design of an antenna module to detect, identify, and isolate potential RFI to prevent FE saturation including that due to the interfrequency effect. Analysis showed that any specific antenna module configuration with fixed internal components must sacrifice noise figure (NF) performance to increase robustness to RFI saturation, and vice versa. To provide a compact solution to this dilemma and the interfrequency saturation issue, two dynamically configurable antenna modules based on the concept of network topology were proposed for typical dual-frequency GPS/GNSS receivers. Such a solution can adapt to different RFI conditions by operating in corresponding modes resulting in a better NF versus robustness tradeoff. The proposed antenna-module design was validated by experiments with live GPS signals under controlled RFI conditions.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-02
Christos D. Nikolopoulos; Anargyros T. Baklezos; Stylianos Tsatalas; Christos N. Capsalis

In their previous work, the authors proposed a methodology for predicting and modeling electromagnetic emissions in case of shielded coaxial cable with respect to the ground dielectric properties. In that work, a shielded coaxial cable was treated as a travelling wave antenna and the decomposed contribution of each phenomenon was validated through extensive electric field measurements of the cable over various ground planes and heights. In the present paper, the authors attempt to verify the applicability of this methodology in more complex structures; exploring the case of SpaceWire (SpW) cable over a carbon-fiber-reinforced polymer ground. This setup is of major interest for space applications, as it becomes the standard harness and grounding design for the majority of space missions. SpW is a space-application focused cable with four shielded twisted pairs employing low-voltage differential sign signaling, a geometry requiring rather cumbersome calculations in order to analytically extract the radiated emissions. The authors showcase that this issue can be bypassed with the proposed methodology, while measurements verify the validity of this claim also for the case of complex structures

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-13
Nicola Alessi; Carlo Caini; Tomaso de Cola; Marco Raminella

Interplanetary networks are affected by long propagation delays, intermittent connectivity, possible packet losses due to residual errors, and other impairments. To cope with these challenges, the delay-/disruption-tolerant networking (DTN) architecture utilizes the Licklider transmission protocol (LTP) as convergence layer on space links. The LTP reliable service (red) relies on Automatic Repeat reQuest, but very long propagation delays make packet layer forward error correcting (PL-FEC) codes very appealing to protect LTP segments from losses. The key advantage of FEC is that LTP retransmissions would be limited to the unlikely case of decoding failures. To this end, a new FEC-based protocol, to be inserted immediately below LTP, the erasure coding link service adapter (ECLSA), is presented here. ECLSA is completely transparent to LTP, relies on two alternative external libraries for coding/decoding, LibecDLR and OpenFEC, both using low density parity check codes and it is fully integrated with the ION DTN software package of NASA-JPL. This paper aims to provide a solid description of ECLSA, including features functional in a real deployment (such as the dynamic selection of codes). Performance is evaluated at the end of the paper, with nearly ideal results. ECLSA is released as free software and is already included in the “contrib” section of ION.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-06
Yulong Huang; Yonggang Zhang; Yuxin Zhao; Lyudmila Mihaylova; Jonathon A. Chambers

A novel robust Rauch–Tung–Striebel smoothing framework is proposed based on a generalized Gaussian scale mixture (GGScM) distribution for a linear state-space model with heavy-tailed and/or skew noises. The state trajectory, mixing parameters, and unknown distribution parameters are jointly inferred using the variational Bayesian approach. As such, a major contribution of this paper is unifying results within the GGScM distribution framework. Simulation and experimental results demonstrate that the proposed smoother has better accuracy than existing smoothers.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-16
Lei Shen; Zhiwen Liu; Yougen Xu; Yang Bai; Tao Zhao

A polarimetric scheme is presented for the detection of a range-spread target when the presumed target steering matrix is deviated from the actual one. Following the adaptive beamformer orthogonal rejection test model, the decision statistic of the proposed detector involves the polarimetric clutter-plus-noise covariance matrix, the target component after noise whitening and rotation, as well as the sidelobe interference vectors of multiple range cells. In the practical realization of the detector, the polarimetric clutter-plus-noise covariance matrix is estimated by using the minimum mean-square-error regularized secondary data sample averaging. Taking into account the mismatch involved in the presumed target steering matrix, the target component is obtained by least square fitting subject to multiple separate conic uncertainty set constraints. The estimation of the sidelobe interference vectors is also based on the Bayesian statistics, and the involved polarimetric clutter-plus-noise covariance matrix is ultimately replaced by its Bayesian estimate previously obtained. The performance of the proposed detector has been evaluated and compared with the existing popular polarimetric detectors using both synthetic and real data. The results show that in the presence of target steering matrix mismatch caused by pointing errors, sensor position errors, channel calibration errors, multipath propagation, and random errors, the proposed detector has a superior performance to the current detectors in terms of the probability of detection.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-06-05
Rojina Adhikary; John N. Daigle; Lei Cao

To maximize file transfer from deep-space vehicles, a space-to-earth content-transfer protocol that combines turbo codes, RaptorQ codes, real-time channel prediction, and dynamic code-rate selection is proposed. The protocol features a signal-to-noise ratio prediction model that facilitates the periodic adjustment of turbo encoder to achieve adaptive-rate transmission, and fountain codes to eliminate retransmission of specific packets. Simulation results indicate that an increase of about 132% in file transfer rate is achievable compared to fixed-rate transmission scheme.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-20
Julie Ann Jackson; Forest Lee-Elkin

We propose a new compressive sensing scheme that enables fully polarimetric radar imaging from a subset of channel measurements. Previous sparse recovery methods for polarimetric radar have not modeled channel coupling. We recognize that mixing of information through coupling is key to dropping a channel. Our method complements fast and slow time sampling and may reduce hardware and communications costs. This paper provides the signal model and examples of successful four-channel recovery when only three are measured.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-08
Xuejing Zhang; Zishu He; Xuepan Zhang; Yue Yang

This paper presents a novel strategy to simultaneously estimate the direction of arrival (DOA) of a source signal and the phase error of a partly calibrated array with arbitrary geometry. We add up the snapshot data of two different sensors, and then extract a knowledge associated with the DOA and phase errors of these two elements by using singular value decomposition. In such a manner, we can establish a series of linear equations with respect to the unknown DOA and phase error, by simply conducting the procedure on any two sensor elements. On this basis, it can be shown that the problem of jointly estimating DOA and phase error is equivalent to a least square (LS) problem with a quadratic equality constraint. To solve this LS problem (so that the DOA and phase error can be obtained), an effective convex–concave procedure is employed. Different from the conventional algorithms that are limited to specific array geometries, the proposed one is suitable for arrays with arbitrary geometries. More importantly, the devised method only requires one extra calibrated sensor, which is not necessarily adjacently located with the reference one. Several simulations are carried out in this paper and the effectiveness of the devised method can be clearly observed.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-02
Jianqing Peng; Wenfu Xu; Lei Yan; Erzhen Pan; Bin Liang; Ai-Guo Wu

The relative pose (position and attitude) measurement of space noncooperative targets is very important for on-orbit servicing activities, such as target tracking, approaching, and capturing. The traditional methods rarely consider the instability of feature extraction and image blurring caused by target tumbling. In this paper, a method based on the maximum outer contour (MOC) recognition is proposed to measure the pose of the target. Different feature extraction algorithms can simultaneously achieve close- and long-range measurement tasks. First, the trailing image is restored by the image enhancement method. Second, the “rough + fine” combination recognition method is used for contour extraction and connected component labeling of the restored image, and the target feature extraction time is reduced to one-third of traditional methods. Furthermore, the elliptical surface on the MOC is fitted by the least squares method (LSM), and the ellipse parameters (i.e., the center position, the long- and short-axes, and the deflection angle) are extracted. The accuracy of the target recognition is improved. Third, for the close-range measurement, based on the detected ellipse parameter, the pose of the noncooperative target is solved by the binocular imaging algorithm of the space circle; for the long-range measurement, the contour centroid of the target is calculated by the detected MOC, and the position of the target is solved by the LSM. Moreover, the effectiveness of the method is verified by the OpenSceneGraph numerical simulation system. Finally, an experimental system consisting of a binocular camera, a UR5 manipulator, and a satellite mockup was built. The experimental results verified the proposed method.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-10-10
Seok-Ho Chang; Sang-Hyo Kim; Jihwan P. Choi

In the fractional frequency reuse (FFR) system, the bandwidth is partitioned into orthogonal subbands such that users in the cell-center region use the subbands of a frequency reuse factor (FR factor) equal to 1, whereas users in the cell-edge region exploit the subbands of an FR factor larger than 1. The distance threshold, which is used to distinguish the cell-edge region from the cell-center region, is an important factor in FFR system performance. In this paper, we study the optimal distance threshold to maximize system throughput in the downlink cellular networks, including aerial base stations. Subject to the constraint that a given target outage probability is satisfied, the optimal distance threshold is analyzed as a function of the cell size. It is proven that when the sizes of all cells in the network are scaled at the same rate, the optimal distance threshold normalized by the cell size is nondecreasing in the cell size. The analytical results in this paper provide a system design guideline for initial planning of FFR cellular networks of different sizes, including macro, pico, and femto systems. In particular, for size-scalable aerial networks comprising base stations in the sky, such as balloons or unmanned aerial vehicles, our analysis offers insight into the design of the distance threshold with regard to the cell size.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-27

In this paper, a new algorithm called blind star identification is presented to identify the stars in night sky images without using the intrinsic parameters of the star sensor camera (focal length, principal point, and pixel size), and in lost in space mode. The accuracy and reliability of the proposed algorithm were successfully validated by using the real night sky images and Monte Carlo simulations. Accordingly, the proposed algorithm was successfully able to identify in more than 90% of the images containing more than five stars and no wrong identification was observed in the Monte Carlo simulations. On the other hand, the rotation around the optical axis, which cannot be estimated using vector observations, should be minimized in the process of designing and manufacturing the star sensor and carefully measured in the ground calibration, like as the aberration and lens distortion. Ultimately, another advantage of this algorithm is the simultaneous use of planar and interstellar angles. This advantage leads to data redundancy and greater reliability of the algorithm so that the performance of the algorithm is guaranteed under severe error conditions.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-17
Yuan Jiang; Hongbin Li; Muralidhar Rangaswamy

We consider signal detection in subspace interference with partial prior knowledge of the subspace. The problem was recently considered by Li et al. , where a subspace knowledge with learning (SKL) Bayesian model was proposed to leverage partial and uncertain knowledge of the subspace bases. The SKL, however, is based on the assumption that the subspace bases are a subset of a known overdetermined dictionary defined on a densely sampled frequency grid. Due to the so-called grid mismatch problem, i.e., the subspace bases may not be exactly on the frequency grid, there is a need to develop solutions that can exploit approximate prior knowledge, i.e., knowledge of frequency grid points close to the true frequencies but the latter themselves. In this paper, we extend the work by Li et al. and develop a modified SKL (mSKL) algorithm to exploit partial, approximate, and uncertain prior knowledge for subspace estimation and target detection. The mSKL is a Bayesian inference algorithm that can reject incorrect subspace bases, recover missing bases, and benefit approximately correct bases in the prior knowledge set. For computational efficiency, the recently introduced generalized approximate message passing (GAMP) is employed in the mSKL for efficient update of some posteriors. The resulting scheme, referred to as the mSKL-GAMP, is shown to offer competitive subspace recovery and target detection performance over a range of alternative methods in various scenarios with different grid mismatch levels.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-30
Gor Hakobyan; Michael Ulrich; Bin Yang

Radar with digitally generated orthogonal frequency division multiplexing (OFDM) signals is an emerging research field that has been studied for the past few years. Another trend for radar is the multiple-input multiple-output (MIMO) architecture used for an efficient direction-of-arrival estimation. These two technologies can be efficiently combined into an OFDM-MIMO radar with novel interleaving concepts enabled by the multicarrier structure of OFDM. By multiplexing of transmit antennas via subcarrier interleaving, the whole bandwidth can be utilized by all transmit antennas simultaneously. In case of equidistant subcarrier interleaving, however, the unambiguously measurable distance range is reduced. To avoid this reduction, we propose an OFDM-MIMO radar concept with nonequidistant subcarrier interleaving (NeqSI) that maintains the full unambiguously measurable distance range. Since the NeqSI leads to sidelobes in distance estimation, we present an approach for generation of near-to-optimum nonequidistant interleaving patterns. To further complement the proposed concept, compressed sensing based distance–velocity estimation algorithm that achieves a high dynamic range in both distance and velocity dimensions is used. We study the performance of the presented concept in simulations and validate it by measurements with an OFDM-MIMO radar prototype.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-17
Zhiqiang Ma; Panfeng Huang

This paper proposes a nonlinear discrete-time sliding mode based tension control for deployment of tethered space robot with only length and angle measurements. The discrete-time dynamics of deployment is uncovered based on discretization of Hamilton's principle. Taking into account the underactuated dynamics, the proposed discrete-time sliding surface can generate a specified reduced-order system, which can be regarded as an uncertain discrete-time system with multiple time delays, which is caused by a considerable sample interval, and the stability of a reduced-order system is well analyzed by combining a linear matrix inequation technique based on robust control theory and nonlinear discrete-time Lyapunov method. A novel input structure with the auxiliary variable sequence is presented to deal with the tension saturation, and the states can converge to the specified reduced-order system although the input saturation occurs. The proposed discrete-time method makes no appeal to velocity terms. It is cost-effective to use the proposed method for the information of length and angle are easily measured rather than that of velocity, and it conduces to low requirements for the measurement ability of sensors. Simulation results verify the stability analyses, and are coincident with the stability analyses.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-22
Augusto Aubry; Vincenzo Carotenuto; Antonio De Maio; Luca Pallotta

This paper is focused on noncooperative target position estimation via the joint use of two-dimensional (2-D) hyperbolic and elliptic passive location techniques based on time difference of arrival (TDOA) and passive coherent locator (PCL) measurements, respectively. A fusion strategy is laid down at the signal processing level to obtain a reliable estimate of the current target position. With reference to the scenario with a single transmitter of opportunity, the mathematical model for joint exploitation of TDOA and PCL strategies is formulated. Then, the Cramer–Rao lower bound (CRLB) for the Cartesian coordinates of the target is established and the theoretical performance gains achievable over the localization technique using only TDOA or PCL observations are assessed. Finally, TDOA-PCL hybrid 2-D localization algorithms are provided and their performance in terms of root-mean-square error is compared with the square root of the CRLB.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-10-10
Afshin Rahimi; Krishna Dev Kumar; Hekmat Alighanbari

A new hierarchical method for fault detection, isolation, and identification of nonlinear systems with applications for in-orbit closed-loop controlled satellites is proposed where fault detection employs unscented Kalman filter and adaptive thresholds. Fault isolation employs multiple model approach in conjunction with Bayes’ probability theorem and adaptive window, and fault identification employs dual state/parameter estimation using unscented Kalman filter. Results show up to 97% success rate under comprehensive Monte Carlo simulations for transient abrupt faults in satellite actuators.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-28
Zegang Ding; Pengjie You; Lichang Qian; Xu Zhou; Siyuan Liu; Teng Long

Long-time integration is an effective method to improve target detection performance in a noisy background. However, when detecting high-speed and maneuvering targets by long-time integration, it is easy to encounter the across range unit and across Doppler unit effects, which deteriorate the detection performance of algorithms with low computational complexity, such as moving target detection and hybrid integration (HI). The generalized Radon–Fourier transform (GRFT) detector has proven to have the best detection performance. However, the GRFT has a high computational burden for an ergodic search in a multidimensional motion parameter space and thus is hardly employed in real engineering applications. In this paper, we propose subspace HI (SHI) to achieve a good balance between detection performance and computational complexity. SHI first divides the parameter space into several equidimensional subspaces and moves them to the center of the coordinate system. Then, HI is implemented on all the subspaces, and all the HI results are finally fused. Through parameter space division and subspace movement, the values of the parameters in the subspaces are reduced, which increases the subaperture length, i.e., the time that the target echoes stay in one range-Doppler unit. By increasing the subaperture length, SHI gradually improves the detection performance with an increase in the computational complexity. Conversely, by shortening the subaperture length, the computational complexity of SHI can be reduced at the expense of the detection performance. Compared with HI and the GRFT, SHI achieves a better compromise between detection performance and computational complexity.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-30
Hao Jin; Rui Xu; Wenming Xu; Shengying Zhu

This paper deals with a new modeling method and a powerful planning approach for deep space probes. The key technique is based on the concept of extended state model. Furthermore, extended state model planning (ESMP) algorithm is designed to be fully compliant with the model, and flaw selection strategies are proposed to avoid redundant work. Finally, we discuss the time complexity of ESMP, and computational results comparing ESMP with the algorithm in Europa are presented.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-20
Zhibo Yan; Juan Andres Fraire; Kanglian Zhao; Hongcheng Yan; Pablo G. Madoery; Wenfeng Li; Hong Yang

Next generation global navigation satellite systems (GNSSs) will embrace intersatellite links capability as an enabler of navigation and data transfer. However, platform restrictions will require of suitable contact plan design (CPD) schemes, which have been traditionally assumed centralized . After discussing the requirements of distributed CPD, we propose a first scheme in this class. Simulation results on the BeiDou GNSS prove that satisfactory metrics can be obtained enabling valuable and real autonomy for future GNSSs.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-20
Michael Kowalski; Yaakov Bar-Shalom; Peter Willett; Djedjiga Belfadel; Fred Daum

As bias estimation methods are developed, it becomes necessary to obtain the bound on bias estimation for more complex bias and sensor models. Three-dimensional (3-D) sensors, such as radars commonly used in applications, contain both scale and additive biases in sine space which result in a nonlinear estimation problem that may have poor observability and accuracy depending on the geometry of the sensors. By converting the sine space and range measurements to Cartesian using an unbiased conversion, it is possible, via creation of pseudomeasurements, to eliminate the need to estimate the target's state thereby reducing the sensor bias estimator complexity. The present paper evaluates the Cramér–Rao lower bound (CRLB) for estimating scale and additive biases in sine space for 3-D sensors and compares it with a maximum likelihood formulation implemented via iterated least squares, which is thereby shown to be statistically efficient. Additionally, the importance of measurement diversity is investigated with respect to the CRLB.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-06-03
Haoge Jia; Zuyao Ni; Linling Kuang; Jianhua Lu

In helicopter satellite communication systems, the received signal is blocked by the helicopter rotor blades during propagation, incurring the unstableness of traditional methods of channel estimation due to unknown channel state. To this end, a joint occlusion detection and phase estimation algorithm is proposed by factor graph in this paper. For occlusion detection to acquire channel state, the occlusion channel model is established relying on a Markov chain with a priori blocking ratio, in which the probability distribution of the channel state is calculated by the proposed message-passing algorithm. To obtain the occlusion position and update the blocking ratio, a cross-correlation method is designed. Furthermore, a joint block detection and phase estimation algorithm is developed based on the proposed occlusion detection algorithm to realize phase estimation by iterative receiver, where occlusion detection, phase estimation, and decoding are performed in turn for one turbo iteration and the result of decoding is then sent back to the occlusion detection step for the next iteration. Simulation results show that the proposed algorithm is adaptive to the dynamical change in the blocking ratio and can achieve bit error rate performance that is close to the performance bounds based on perfect channel state.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-05-31
Namhoon Cho; Suwon Lee; Jinrae Kim; Youdan Kim; Sanghyuk Park; Chanho Song

This study presents a method to adjust the waypoints of an unpowered air vehicle to compensate for the influence of wind on the trajectory. A framework combining preflight waypoint planning and inflight waypoint adjustment is proposed. In the offline planning phase, optimal trajectories under various wind profile combinations are generated by using a direct optimization method. Waypoints are extracted from the obtained trajectories for each wind condition. Then, deviations of each waypoint due to wind from the corresponding waypoint on the trajectory for a zero-wind case are obtained; these deviations are used to construct the models of waypoint deviation as functions of wind speed and direction via least-squares regression. In the online adjustment phase, the wind-compensated waypoint is computed using the waypoint deviation model and the estimated wind velocity. A nonlinear six degrees-of-freedom simulation, incorporating a guidance and control system and a realistic wind profile, is performed to demonstrate the effectiveness of the proposed waypoint management framework.

更新日期：2020-02-11
• IEEE Trans. Aerosp. Electron. Sys. (IF 2.797) Pub Date : 2019-08-30
Ke-Bo Li; Hyo-Sang Shin; Antonios Tsourdos; Min-Jea Tahk

The capturability of the two-dimensional (2-D) pure proportional navigation (PPN) guidance law against lower speed arbitrarily maneuvering target for homing phase had been thoroughly analyzed by using the nonlinear output regulation (NOR) method before. However, due to the complexity of the 3-D relative kinematics, the NOR method has not been applied to the capturability analysis of the 3-D PPN, which leads to the capturability discrepancy of the 2-D PPN and its 3-D extension. Thanks to the 3-D relative kinematic equation between the missile and target established in the rotating line-of-sight coordinate system, the capturability of the 3-D PPN against the lower speed arbitrarily maneuvering target for the homing phase is restudied by extending the NOR method of the 2-D PPN to the 3-D space. The necessary and sufficient condition for the missile guided by the 3-D PPN to intercept this type of target is obtained. It is proven that the capturability of the 3-D PPN is identical with that of the 2-D PPN.

更新日期：2020-02-11
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