Abstract:Spatial information can be described as the range information, direction of arrival (DOA) information and scattering information of the targets in radar detection systems. Spatial information theory is a basic theory for information extraction system such as radar systems using Shannon information theory. The recent research progress and main research work are summarized based on the concept of spatial information, the theoretical and closed-form expressions of spatial information, entropy error, radar resolution, and other basic theoretical issues. The concept of spatial information and its system model are introduced to analyze the spatial information. The theoretical derivation of the quantity of spatial information, the concept of entropy error and its relation to mean square error, the new definition of resolution and its relation to traditional resolution are emphatically analyzed. The theoretical problems that need to be solved are pointed out in the paper. Finally, the development trend of spatial information theory is analyzed and prospected.

Abstract:The Capon beamformer, known as the optimal beamformer in suitable case, has the remarkable interferences suppression capability. However, the Capon beamformer is highly sensitive to the model mismatches. Especially when the covariance matrix and desired signal steering vector errors are existed, the performance of beamformer would degrade dramatically, which greatly reduces the robustness of the beamformer. Nowadays, a number of robust adaptive beamforming (RAB) algorithms based on the covariance matrix reconstruction have been proposed. The main idea of these algorithms utilizes the Capon power spectrum integrated in the special region to reconstruct the covariance matrix. In this paper, the signal model of beamforming is introduced firstly, and four typical covariance matrix reconstruction RAB algorithms are expounded based on the Capon beamformer. Finally, the future research directions are prospected.

Abstract:As a key part of communication industry chain,the 5th generation mobilecommunication system(5G) testing technology makes it possible to simulate and test 5G network devices and evolving new standard technology. Flexible and diverse test technology can truly reflect the network status, providing a strong guarantee for enhancing the coverage of 5G network and improving the overall performance of the network.This paper first gives a brief overview of global 5G development status and an introduction to China’s test progress in 5G key technology verification, core network verification and access network verification. Then it particularly presents the over-the-air (OTA) testing technology of 5G NR (New radio) and its advantages for massive MIMO. Finally, the challenges and development trends of future 5G testing are forecasted.

Abstract:As one of the key technologies of cognitive radio, spectrum sensing is extensively and deeply studied. In the case of low SNR environment, the threshold of traditional double threshold method is fixed, which leads to poor perception effect. To solve the problem, an adaptive double-threshold cooperative spectrum sensing algorithm is proposed. The weight is obtained by calculating the SNR of each node. The weights are obtained. The decision threshold is adjusted, and the current judgment result is fully correlated with the time before and after, and the final decision result is obtained by fusing the decision information of each node. The results of theoretical analysis and Monte-Carlo simulation show that the algorithm can effectively improve the spectrum sensing performance compared with the traditional double threshold detection algorithm and the weighted double threshold detection algorithm.

Abstract:The paper implements the research of spatial spectrum estimation for coprime linear array. By utilizing the conjugate augmented characteristic of the second-order statistic of the signals, a conjugate augmented unitary estimation of signal parameters via rotational (ESPRIT) (CA-UESPRIT) direction of arrival (DOA) estimation algorithm is proposed. By using the second-order statistics of the received signals with different time lags, the algorithm firstly constructs a conjugate augmented virtual array to expand the array aperture and improve degrees of freedom (DOFs), subsequently, achieves the DOA estimation by exploiting the coprime property based joint UESPRIT algorithm. Compared to the traditional joint UESPRIT algorithm for coprime linear array, better DOA estimation performance can be achieved by CA-UESPRIT algorithm. In addition, the covariance matrix of the ESPRIT algorithm can be transformed from the complex domain to the real domain by the unitary transform, which reduces the complexity but ensures the estimation accuracy. The simulation results verify the effectiveness of the proposed algorithm.

Abstract:Aiming at the problem of high complexity of particle-filtering in single channel blind separation for digital mixed signals, a novel low complexity algorithm is proposed. By analyzing, the high algorithm complexity lies in the exponentially increase between the number of researching spaces and the smoothing length in particle sampling process. Two sampling schemes are proposed, which are named partial sampling and hybrid sampling. The basic ideal of partial sampling is that instead of exploring the whole space of smoothing interval, several symbol sequences are generated. The incremental weights of each symbol sequences are used for particle sampling and weight update. The hybrid sampling scheme divides the smoothing interval into two parts, in which the first part uses the traditional full space searching scheme and the second one uses the partial sampling scheme. The incremental weights of the two parts are used for particle sampling and weight update. Theoretical analysis and simulation results show that the proposed algorithm can efficiently reduce the particles’ searching spaces.

Abstract:Aiming at poor anti-error performance in the existing algorithms for RS codes, a blind recognition algorithm based on non-zero-mean-ratio is proposed. The algorithm constructs the analysis matrix by transforming the intercepted RS code sequence into GF(2 ^m ) symbols. The finite-field Gauss-Jordan elimination algorithm is used to obtain the non-zero-mean-ratio of the analysis matrix and identify the code length, symbol number and the primitive polynomial. Finally, the Galois field Fourier transform is used to complete the information bit length and generator polynomial recognition. Simulation results show that the proposed algorithm can effectively identify all the coding parameters of the primitive RS code and shorten RS code. The anti-error performance is better, and the relationship among the recognition performance and the information bit length and the code length is given. As the code length and information bit length increase, the recognition performance gradually decreases.

Abstract:Direction of arrival (DOA) estimation using sensor arrays with strong interferences is an important problem in array signal processing. Although the DOA estimation accuracy of existing methods for on-grid targets is high, the DOA estimation performance of these methods for off-grid targets degrades seriously. In this paper, a new DOA estimation method is proposed. Firstly, a new matrix filter called robust orthogonal matrix filter with nulling (ROMFN) which combines the orthogonal matrix filter with nulling (OMFN) and robust adaptive beamforming using worst-case is used for filtering of off-grid targets. ROMFN is effective for off-grid targets just with a few grid points designed. Besides, the new matrix filter preserves the white Gaussian noise property, avoiding the pretreatment of noise whitening. Secondly, a new DOA estimation method is used to estimate DOAs of off-grid sources with strong interferences based on off-grid sparse Bayesian inference (OGSBI) and ROMFN. Compared to previous methods, simulation results validate the proposed method can achieve better resolution in different grid intervals, different SNRs and different INRs.

Abstract:The rapid change of the topology for the intelligent connected vehicles results in the instability of communication links, which reduces the efficiency of data forwarding. To address these challenges, the paper proposes a road section scoring-based data forwarding model for intelligent connected vehicles (RSSM) for urban scenario. Firstly, the road segment is divided into two parts by the vehicle density, and the connectivity for the two parts of the road is modeled, separately. Then, the connectivity between the nodes in the whole road segment is obtained as the scoring of the road segment. Then, the connectivity for all road segments in the whole road network is calculated and regarded as the scoring of the corresponding road segments. Next, the dynamic path calculation from the source node to the destination node is realized by the scoring of the whole road network, which ensures that the planned routing is optimal. Finally, RSSM is implemented on the NS3 and SUMO experimental platform. Experimental results show that the proposed RSSM is superior to the similar data forwarding methods in terms of the successful rate of data delivery and average end-to-end delay.

Abstract:Surface electromyography(sEMG) signal directly and objectively reflects the functional status of nerve and muscle, which has been widely used. In this paper, a sEMG acquisition circuit is designed and used as single channel circuit to collect sEMG signals of five kinds of upper limb movements, then six kinds of features (one of which is quoted from the feature extraction method based on wavelet transform) are extracted by wavelet packet transform(WPT) combining with KPCA, and finally recognition is performed with BP neural network and SVM. Feature extraction based on wavelet transform is also performed for comparison and the difference between PCA and KPCA on feature transform is also studied. The results show that among the six kinds of features extracted by wavelet packet transform, five kinds of recognition rates exceed 95.7%, and the average recognition rate of the high-low frequency coefficients combination feature quoted is more than 99% with a BP neural network. Overall, the recognition rates are high. And the five kinds of features extracted by wavelet transform combining KPCA also achieve a decent recognition rate. The results prove that the sEMG signals collected and the feature extraction method used in this paper are both effective.

Abstract:In this paper, a distributed relay selection optimization method is proposed for the optimization of service transmission energy in microcellular networks. Taking the transmission energy consumption as the optimization goal under the condition that the user meets his own transmission requirements. The user’?s service transmission requirements, the wireless environment, the location of the relay service node, and other users’choice relays are comprehensively analyzed. The service transmission relay selection distributed optimization model is established. The optimization relay selection game model for energy efficiency of microcellular network is constructed. The game is proved to be an accurate potential energy game. An energy efficiency optimization relay selection distributed optimization decision-making algorithm is designed, and the convergence of the algorithm is proved. Experiment analysis verifies the theoretical analysis of the proposed game model and learning algorithm which show that the proposed algorithm can effectively optimize the relay selection results in a distributed decision-making manner and satisfy the user’s transmission needs.

Abstract:Device-to-device (D2D) communication has attracted a lot of attention since it is considered as a key technology for 5G. The high rate can be obtained by the short distance between D2D users. However, this superiority will be lost when the distance between D2D users increases, since the transmit power of user is limited. Motivated by these, in order to improve the performance of D2D link, this paper investigates the D2D communication assisted with another D2D user working as a relay node. We consider three modes including traditional D2D communication, amplify-and-forward (AF) relay node assisted D2D communication and D2D communication aided by decode-and-forward (DF) relay node. In this paper, we analyze the achievable rate of each mode, and propose a mode selection scheme which is presented with closed-form expressions， which include only elementary functions. The mode selection scheme guarantees the D2D link always achieves the maximum rate of three modes. Numerical results show the significantly enhanced performance with the mode selection scheme.

Abstract:The short-circuit grounding wire is an important device to ensure the personal safety of power production. The traditional portable short-circuit grounding wire lacks intelligent monitoring means, and often suffers from leakage, misconnection, and detachment, which brings safety hazards to personal, equipment, and power grid safety, and even personal injury or death. Based on the internet of things(IoT) technology, this paper designs the overall framework including the sensing layer, network layer, platform layer and application layer, and develops the grounding line intelligent monitoring device and system to realize the automatic collection and movement of grounding line distribution, hooking status and equipment information, real-time monitoring and integrated management. Through the actual scenario pilot of Wuxi Power Supply Company of State Grid, result shows that the intelligent monitoring device and system can visually display the multi-dimensional information of the grounding equipment, and have the characteristics of real-time, mobility and scalability, effectively assisting security management decision-making, and improving on-site security integrated control level.

Abstract:Unmanned aerial vehicles (UAVs) as relaying can establish a reliable and efficient data transmission link and is used in the field of emergency communications. By considering the interferences at the amplify-and-forward UAV relays, two beamforming (BF) strategies are proposed to improve the communication quality and performance. The expressions of signal-to-interference-and-noise ratio and achievable rate at the ground receiver are first presented. Then, two optimization problems are formulated, namely total relay transmit power minimization and achievable rate maximization, and the corresponding BF schemes is designed to obtain the optimal BF analytical expressions. Finally, the effectiveness and validity of the proposed BF schemes are verified by simulations.

Abstract:Aiming at the low energy efficiency caused by the energy consumption of cognitive radio network, an optimal power allocation algorithm is proposed to maximize the energy efficiency of secondary user system based on clustering cooperative spectrum sensing. By establishing the energy efficiency maximization transmission model and considering transmission power, perceived time constraints and interference constraints, the optimal transmitted power allocation algorithm can be obtained to achieve the purpose of the system energy efficiency maximization through using Lagrange function and KKT condition. Then the influence of different parameters on energy efficiency is analyzed. Simulation results show that the proposed algorithm can reduce energy consumption and improve energy efficiency.

Abstract:In high-speed mobile communication systems, there exist two prominent issues-large Doppler spread and limited pilot resource between the transmitter and receiver, which has great influence on the performance of a traditional joint frequency-phase offset estimation. In this case, this paper proposes a parallel processing-based joint frequency-phase offset estimation. First, we utilize a variable delay-length auto-correlation operator to design a frequency-phase decoupling algorithm and apply it to the traditional joint frequency-phase offset estimation. Theoretical analysis and simulation results show that the proposed frequency-phase decoupling algorithm can decouple the phase offset estimation and frequency offset estimation, and can also reduce complexity of the phase offset estimation.

Abstract:Non-orthogonal multiple access (NOMA) in communication system has recently received significant attention since it provides a superior spectral efficiency and supports massive connectivity. We study a resource allocation problem in multi-user downlink NOMA systems to achieve the maximum energy efficiency. The original optimization problem is a non-convex problem that is difficult to solve. Therefore, the original optimization problem is decomposed into two sub-problems, i.e., the user assignment and the power allocation. A user grouping method based on greedy algorithm is firstly used to reduce the computational complexity of the exhaustive method. Secondly, for the given user grouping method, the power allocation coefficient expression of the multiplexed user on each sub-channel is obtained. In order to further improve the energy efficiency, a non-equal power allocation scheme is investigated. The problem of power allocation on all sub-channels is formulated as a nonlinear and non-convex problem of the sum of the ratios, and a Dinkelbach-like algorithm is proposed to obtain a suboptimal solution. Simulation results show that the NOMA system equipped with the proposed algorithms perform well in terms of sum rate and energy efficiency.

Abstract:Aiming at the security problems of Modbus TCP protocol, such as lack of authentication, data transmission in clear text and abuse of function codes, a secure industrial control communication protocol (Modbus-S protocol) based on the original Modbus TCP protocol is proposed. The digital signature technology is used to ensure the integrity and authentication of data. The symmetric encryption is used to ensure the confidentiality of data. The unidirectional principle of hash function is used to guarantee the uniqueness of data. Finally, the "white list" filtering mechanism is used to manage function codes based on roles to ensure the controllability of instructions. Experimental verification and analysis show that Modbus-S protocol can fully compensate for the design defects of Modbus TCP protocol. Compared with the existing methods, the method has higher security and can comprehensively improve the communication security of Modbus TCP protocol.

Abstract:Benefiting from the development of compressed sensing (CS) theory, sparse representation based off-grid direction-of-arrival (DOA) estimation technique has been extensively exploited, resulting in several high accuracy methods. However, most of these methods are based on the grid assumption, i.e., the DOAs of the incident signals are accurately located on the grid points, which violates the fact that the true DOAs belong to the continuous angle space. This grid bias effect may bring in model mismatch, leading to performance deterioration. In this paper, we propose an off-grid signal model based on Taylor expansion, which allows the DOAs to deviate from the grid points, so the grid bias effect can be eliminated, and the estimation accuracy can be improved. We employ an alternating iterative method to solve the problem and use the singular value decomposition to reduce the computational cost. The proposed method is able to reduce the grid bias, resulting in high estimation accuracy. Simulation results are provided to verify the effectiveness of the proposed method.

Abstract:Traditional statistical methods do not provide accurate prediction for UAV channels under specific scenarios. For the urban scenarios, a geometry-based stochastic channel model for the communication link between UAV-based base stations and ground is developed by a deterministic method based on the ray tracing principle. The proposed model considers the influence of scattering times on received power, and divides arrival rays to the ground into three types, e.g., the line-of-sight component, the single-bounced component, and the double-bounced component. By calculating the electric field along the propagation path and using the ray tracing principle, the computation methods for the path loss and received power of three kinds of components are given. After the digital map is pre-processed, the propagation paths, path loss, power delay profile, and power coverage are simulated and verified. Numerical and analytical results show that the proposed model can accurately reconstruct the propagation situation and the coverage predictions can be used on the UAV layout optimization.