Sequential measurement processing is of benefit to both estimation accuracy and computational efficiency. When the noises are correlated across the measurement components, decorrelation based on covariance matrix factorization is required in the previous methods in order to perform sequential updates properly. A new sequential processing method, which carries out the sequential updates directly using the correlated measurement components, is proposed. And a typical sequential processing example is investigated, where the converted position measurements are used to estimate target states by standard Kalman filtering equations and the converted Doppler measurements are then incorporated into a minimum mean squared error (MMSE) estimator with the updated cross-covariance involved to account for the correlated errors. Numerical simulations demonstrate the superiority of the proposed new sequential processing in terms of better accuracy and consistency than the conventional sequential filter based on measurement decorrelation.

A typical electronic communication system, such as GPS receiver, unmanned aerial vehicle’s (UAV’s) data link, and radar, faces multi-dimensional and complicated electromagnetic interference in operating environment. To measure the antiinterference performance of the electronic communication system in the complicated electromagnetic interference environment, a method of multi-dimensional and complicated electromagnetic interference hardware-in-the-loop simulation in an anechoic room is proposed. It takes into account the characteristics of interference signals and the positional relationship among interference, the receiver and the transmitter of the electronic communication system. It uses the grey relational method and the angular domain mapping error correction method to control the relevant parameters, the microwave switch and so on, thus achieving the approximately actual mapping of the outdoor multi-dimensional and complicated electromagnetic interference in the anechoic room. To verify the effectiveness of this method, the multi-dimensional and complicated electromagnetic interference of the UAV’s data link is simulated as an example. The results show that the degree of correlation between the calculated signal to interference ratio of the data link receiver in the actual scene and the measured signal to interference ratio of the data link receiver simulated with this method in the anechoic room is 0.968 1, proving that the method is effective for simulating the complicated electromagnetic interference.

Wireless communication is easily disturbed by unfortunate factors which drive the wireless environment unstable and complicated. Therefore, it is essential to consider these factors in stability analysis of the wireless network. However, wireless channel characteristics and packets collisions are neglected in the classical fluid model. A wireless TCP fluid model (WTFM) for stability analysis of wireless network is proposed based on cross layers, which not only makes the congestion control based on random early detection (RED) available for wireless network, but also provides a more accurate model to analyze the stability of wireless system theoretically. In the proposed model, active queue management, abnormality of wireless channels and packets collisions are taken into consideration. The comparisons between evaluating results from the WTFM and the practical performance from NS2 simulations validate the accuracy of the proposed WTFM in the perspectives of delay, dropping probability, throughput, sliding window size and queue length. A set of comparisons among the proposed WTFM, the classical fluid model and the convex optimization model are conducted. The results demonstrate that the proposed WTFM model performs better than other schemes in comprehensive aspects on capturing the characteristic of the wireless network and computing complexity.

A new time-frequency transform, known as short-time Lv transform (STLVT), is proposed by applying the inverse Lv distribution to process consecutive segments of long data sequence. Compared with other time-frequency representations, the STLVT is able to achieve better energy concentration in the time-frequency domain for signals containing multiple linear and/or non-linear frequency modulated components. The merits of the STLVT are demonstrated in terms of the effects of window length and overlap length between adjacent segments on signal energy concentration in the time-frequency domain, and the required computational complexity. An application on the spectrum sensing for cognitive ratio (CR) by using a joint use of the STLVT and Hough transform (HT) is proposed and simulated.

In order to improve the acquisition probability of satellite navigation signals, this paper proposes a novel code acquisition method based on wavelet transform filtering. Firstly, the signal vector based on the signal passing through a set of partial matched filters (PMFs) is built. Then, wavelet domain filtering is performed on the signal vector value. Since the correlation signal is low in frequency and narrow in bandwidth, the noise out-of-band can be filtered out and the most of the useful signal energy is retained. Thus this process greatly improves the signal to noise ratio (SNR). Finally, the detection variable when the filtered signal goes through the combination process is constructed and the detection based on signal energy is made. Moreover, for the better retaining useful signal energy, the rule of selection of wavelet function has been made. Simulation results show the proposed method has a better detection performance than the normal code acquisition methods under the same false alarm probability.

This paper addresses the extremal problem of the null subcarriers based Doppler scale estimation in underwater acoustic (UWA) orthogonal frequency division multiplexing (OFDM) communication. The cost function constructed of the total energy of null subcarriers through discrete Fourier transform (DFT) is proposed. The frequencies of null subcarriers are identified from non-uniform Doppler shift at each tentative scaling factor. Then it is proved that the cost function can be fitted as a quadratic polynomial near the global minimum. An accurate Doppler scale estimation is achieved by the location of the global scarifying precision and increasing the computation minimum through polynomial interpolation, without complexity. A shallow water experiment is conducted to demonstrate the performance of the proposed method. Excellent performance results are obtained in ultrawideband UWA channels with a relative bandwidth of 67%, when the transmitter and the receiver are moving at a relative speed of 5 kn, which validates the proposed method.

Time reversal mirror (TRM) can use the physical characteristicsof the underwater acoustic (UWA) channel to focus onthe desired user in multi-user UWA communication. The activeaverage sound intensity (AASI) detector can estimate all azimuthsof users with the same frequency band at the same time in orderto achieve directional communication by vector combination.Space-division multiple access (SDMA) based on TRM combinedwith the AASI detector is proposed in this paper, which can makethe capacity of the code division multiple access (CDMA) UWAsystem significantly increase. The simulation and lake test resultsshow that the 7-user UWA multi-user system can achieve low biterror communication.

With the rapid development of wireless local area network(WLAN) technology, an important target of indoor positioningsystems is to improve the positioning accuracy while reducing theonline calibration effort to overcome signal time-varying. A novelfingerprint positioning algorithm, known as the adaptive radio mapwith updated method based on hidden Markov model (HMM), isproposed. It is shown that by using a collection of user tracesthat can be cheaply obtained, the proposed algorithm can takeadvantage of these data to update the labeled calibration data tofurther improve the position estimation accuracy. This algorithm isa combination of machine learning, information gain theory andfingerprinting. By collecting data and testing the algorithm in a realisticindoor WLAN environment, the experiment results indicatethat, compared with the widely used K nearest neighbor algorithm,the proposed algorithm can improve the positioning accuracy whilegreatly reduce the calibration effort.

 We investigate the performance of multiple relays cooperativego back n automatic repeat request (MRC-GBn-ARQ) protocolwith limited retransmission. An N+2-state Markov transitionmodel is constructed for analyzing arbitrary packet transmissionprocess with limited retransmission. Then the system’s steadystatedistribution is derived by using the Kolmogorov equations.Further, the mean packet transmission delay and startup delayare obtained respectively; the channel utilization is derived basedon discrete-time Geom/G/1 queue model with startup. Also, weget the energy efficiency of the MRC-GBn-ARQ based on energyanalytical model. Especially, the presented models are contrary tothe classical ARQ protocols of always allowing infinite retransmission,and our analysis of the MRC-GBn-ARQ protocol with limitedretransmission provides theoretical results for reducing the system’sdelay and energy consumption. Finally, analysis is validatedthrough some numerical simulations.

A novel method is proposed for the supervised classificationof multifrequency polarimetric synthetic aperture radar(PolSAR) images. The coherency matrices in P-, L-, and C-bandsare mapped onto a 9×9 matrix Ω based on the eigenvalue decompositionof the coherency matrix of each band. A boxcar filteris then performed on the matrix Ω. The filtered data are put intoa complex Wishart classifier. Finally, the effectiveness of the proposedmethod is demonstrated with JPL/AIRSAR multifrequencyPolSAR data acquired over the Flevoland area.

A distributed blackboard decision-making framework forcollaborative planning based on nested genetic algorithm (NGA)is proposed. By using blackboard-based communication paradigmand shared data structure, multiple decision-makers (DMs) cancollaboratively solve the tasks-platforms allocation schedulingproblems dynamically through the coordinator. This methodologycombined with NGA maximizes tasks execution accuracy,also minimizes the weighted total workload of the DM which ismeasured in terms of intra-DM and inter-DM coordination. Theintra-DM employs an optimization-based scheduling algorithm tomatch the tasks-platforms assignment request with its own platforms.The inter-DM coordinates the exchange of collaborative requestinformation and platforms among DMs using the blackboardarchitecture. The numerical result shows that the proposed blackboardDM framework based on NGA can obtain a near-optimalsolution for the tasks-platforms collaborative planning problem.The assignment of platforms-tasks and the patterns of coordinationcan achieve a nice trade-off between intra-DM and inter-DMcoordination workload.

Grey mathematics is the mathematical foundation of thegrey system theory. Recently, some important results have beenachieved. In order to accelerate the development of grey mathematics,the results are summarized and redefined. This paperincludes the fundamental definitions and calculation rules of thegrey hazy set, grey number, grey matrix and grey function. Greymathematics includes four types of operation, i.e. the grey operation,the whitened operation, the covered operation and the onlypotential true operation. According to its intrinsic quality, the coveredoperation, which differs from the interval one, is called as thewhole-proximate calculation that means the proximate calculationspreads through the whole range of the covered set of every greynumber, and we confirm that it may be a new branch of computationalor applied mathematics. The overview should develop thegrey system theory and grey mathematics.

The issue of attitude maneuver of a flexible spacecraftis investigated with single gimbaled control moment gyroscopes(SGCMGs) as an actuator. To solve the inertia uncertainty of thesystem, an adaptive attitude control algorithm is designed by applyinga radial basis function (RBF) neural network. An improvedsteering law for SGCMGs is proposed to achieve the optimal outputtorque. It enables the SGCMGs not only to avoid singularity,but also to output more precise torque. In addition, global, uniform,ultimate bounded stability of the attitude control system is provedvia the Lyapunov technique. Simulation results demonstrate theeffectiveness of the new steering law and the algorithm of attitudemaneuver of the flexible spacecraft.

To rapidly generate a reentry trajectory for hypersonicvehicle satisfying waypoint and no-fly zone constraints, anovel optimization method, which combines the improved particleswarm optimization (PSO) algorithm with the improved Gausspseudospectral method (GPM), is proposed. The improved PSOalgorithm is used to generate a good initial value in a short time,and the mission of the improved GPM is to find the final solutionwith a high precision. In the improved PSO algorithm, by controllingthe entropy of the swarm in each dimension, the typical PSOalgorithm’s weakness of being easy to fall into a local optimumcan be overcome. In the improved GPM, two kinds of breaks areintroduced to divide the trajectory into multiple segments, and thedistribution of the Legendre-Gauss (LG) nodes can be altered, sothat all the constraints can be satisfied strictly. Thereby the advantagesof both the intelligent optimization algorithm and the directmethod are combined. Simulation results demonstrate that theproposed method is insensitive to initial values, and it has morerapid convergence and higher precision than traditional ones.

Craters are salient terrain features on planetary surfaces,and provide useful information about the relative dating ofgeological unit of planets. In addition, they are ideal landmarksfor spacecraft navigation. Due to low contrast and uneven illumination,automatic extraction of craters remains a challengingtask. This paper presents a saliency detection method for crateredges and a feature matching algorithm based on edges information.The craters are extracted through saliency edges detection,edge extraction and selection, feature matching of the same crateredges and robust ellipse fitting. In the edges matching algorithm,a crater feature model is proposed by analyzing the relationshipbetween highlight region edges and shadow region ones. Then,crater edges are paired through the effective matching algorithm.Experiments of real planetary images show that the proposedapproach is robust to different lights and topographies, and thedetection rate is larger than 90%.

In solving small- to medium-scale travelling salesmanproblems (TSPs) of both symmetric and asymmetric types, thetraditional ant colony optimization (ACO) algorithm could workwell, providing high accuracy and satisfactory efficiency. However,when the scale of the TSP increases, ACO, a heuristic algorithm,is greatly challenged with respect to accuracy and efficiency. Anovel pheromone-trail updating strategy that moderately reducesthe iteration time required in real optimization problem-solvingis proposed. In comparison with the traditional strategy of theACO in several experiments, the proposed strategy shows advantagesin performance. Therefore, this strategy of pheromone-trailupdating is proposed as a valuable approach that reduces thetime-complexity and increases its efficiency with less iteration timein real optimization applications. Moreover, this strategy is especiallyapplicable in solving the moderate large-scale TSPs basedon ACO.

 Contraposing the need of the robust digital watermarkfor the copyright protection field, a new digital watermarking algorithmin the non-subsampled contourlet transform (NSCT) domainis proposed. The largest energy sub-band after NSCT is selectedto embed watermark. The watermark is embedded into scaleinvariantfeature transform (SIFT) regions. During embedding, theinitial region is divided into some cirque sub-regions with the samearea, and each watermark bit is embedded into one sub-region.Extensive simulation results and comparisons show that the algorithmgets a good trade-off of invisibility, robustness and capacity,thus obtaining good quality of the image while being able to effectivelyresist common image processing, and geometric and comboattacks, and normalized similarity is almost all reached.

This paper presents several useful mixture representations for the reliability function of the residual live of a coherent system with independent but non-identically distributed components. These presentations are based on order statistics, signatures and mean reliability functions. We then discuss some stochastic comparisons of residual lives between two systems based on the stochastic ordering of coefficient vectors (or components) of the two systems. These results form nice extensions of some known results for the case of independent and identically distributed components.