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    2020,32(3):329-335, DOI: 10.3979/j.issn.1673-825X.2020.03.001
    Abstract:
    Aiming at the selection of target MEC servers for task offloading in networks with ultra-dense deployment of mobile edge computing (MEC) servers, a multiple indicators-based MEC server selection scheme (MIMS) is designed in this paper.Considering the influence of multiple indicators, such as delay, energy consumption, task offloading cost and energy efficiency, the candidate MEC servers are sorted by the sum of indicators' linear weighted values, and then the optimal MEC server is obtained.The simulation results show that MIMS can improve users' performance in task processing delay while meeting constraints of multiple indicators.
    2020,32(3):336-344, DOI: 10.3979/j.issn.1673-825X.2020.03.002
    Abstract:
    In the VANET cloud, some computationally intensive tasks need to be offloaded to the surrounding vehicles for coordinated processing due to the limited resources of the vehicle itself. The randomness of vehicle movement is one of the important factors affecting the offloading performance. For this reason, we propose an offloading task allocation strategy between vehicles. Considering the randomness of connection time between vehicles, we adopt a connection time prediction method based on artificial neural network. This method can accurately predict the future vehicle trajectory by learning historical data. In addition, sharing idle resources to other vehicles means increasing energy consumption. Due to the selfishness of the vehicles, they will not provide services for surrounding vehicles without compensation. In order to encourage the cooperation of available vehicles, we have developed a distributed Buyer/Seller game method to achieve a balance between resource demand and payment. Finally, we design a centralized task allocation strategy to get the maximum utility of task offloading. The simulation results show that the proposed method is feasible in maximizing the offloading utility and improving the success rate of task offloading.
    2020,32(3):345-355, DOI: 10.3979/j.issn.1673-825X.2020.03.003
    Abstract:
    Aiming at the problem of location accuracy in the multi-path effect of indoor environment, this paper proposes a multi-path degree division with self-calibration fingerprint localization algorithm based on 3 dimensional convolutional neural network (3DCNN). The algorithm uses the MeanShift method to analyze the data distribution characteristics of the channel state information of each sampling point in the location area, and obtains the number of clusters that can represent the degree of multipath effect.The fingerprint library is divided into two sub-libraries with different multipath degrees by combining the threshold principle, thereby reducing the influence of fingerprint points with large differences in multipath degree on subsequent positioning, and using 3DCNN to deeply learn two types of fingerprint sub-libraries;in the positioning stage,judging the sub-library to which the data to be tested belongs according to the calibration algorithm, and adopting corresponding 3DCNN model estimates the location. The simulation experiment proves that this method can achieve a significant improvement in positioning accuracy while ensuring the rationality and high efficiency of the fingerprint database construction. This method is better than the related algorithms.
    2020,32(3):356-367, DOI: 10.3979/j.issn.1673-825X.2020.03.004
    Abstract:
    In the virtual machine placement problem, the traditional heuristic methods are not entirely applicable to the complex cloud computing environment, and the researches using intelligent algorithms lack the consideration of time overhead. To solve the above problems, a Memetic algorithm-based virtual machine placement (MAVMP) method is proposed. Firstly, The MAVMP method establishes a multi-objective optimization model for minimizing energy consumption, minimizing the service-level agreement violation times per active host (SLATAH) and maximizing resource utilization according to the operation situation of cloud data centers. Secondly, on the basis of resource requests, virtual machines are classified, improving the Memetic algorithm. Finally, the improved Memetic algorithm is used to solve the multi-objective optimization model, and then obtain the virtual machine placement plan. The results of simulation test show that the simulation data center using the MAVMP method to place virtual machines has good performances in energy consumption,resource utilization and service quality. Moreover, in contrast to the existing intelligent algorithm-based virtual machine placement method, the calculation time of the MAVMP method decreases sharply.
    2020,32(3):368-376, DOI: 10.3979/j.issn.1673-825X.2020.03.005
    Abstract:
    In order to improve the convergence and diversity of multi-objective particle swarm optimization algorithm, a new multi-objective particle swarm optimization algorithm based on expansion and dual distance is proposed. The main innovations of this paper are as follows: firstly,the upper and lower limits of the objective function value in the target space are expanded by the expansion, and after the grid is established by the new upper and lower limits, the coordinates of the boundary point can be calculated. Then, when selecting the leader or the inferior particles in a small grid,the decision is made by the two distances from the small grid to the ideal point and the current small grid. In this way, the information in the target space is fully utilized to judge the priority of the particles; Finally, the differential mutation of the new particles increases overall diversity and the frequency of their mutation is controlled by a threshold. The algorithm is compared with the current representative multi-objective particle swarm optimization algorithm, and the results show that the algorithm proposed in this paper is better than the comparison algorithm. Experiments show that the convergence and diversity of the proposed algorithm are not only improved, but also stable.
    2020,32(3):377-384, DOI: 10.3979/j.issn.1673-825X.2020.03.006
    Abstract:
    Aiming at the problems of data corruption and loss caused by improper operation of administrators and hacker attacks etc. in power payment terminals, a data integrity protection verification method based on multi-branch hash tree structure is designed. This method uses the signature mechanism based on bilinear mapping and the characteristics of multi-branch tree structure. Firstly, the random mask technique is used to randomize the blocked data to ensure data privacy. Then, the multi-branch tree structure is used to implement the fast authentication and fast signature of the blocked data, and the hash value of the hash tree node is used to verify the integrity of the blocked data. Finally, the verification server is introduced to perform batch verification and evidence calculation on blocked data, and the backup server is to complete backup processing of stored data. The experimental results show that the scheme can effectively improve the batch detection efficiency of storage data integrity, reduce the computational overhead of the terminal and the main server, and has lower computational overhead and higher security.
    2020,32(3):385-393, DOI: 10.3979/j.issn.1673-825X.2020.03.007
    Abstract:
    In cognitive heterogeneous wireless networks, a spectrum handoff mechanism based on reputation system is proposed. This mechanism is to solve the problem of network performance degradation caused by selfishness or malicious behavior of secondary users in spectrum handoff. Firstly,by extracting the user characteristic information,the behavior of the secondary users after accessing the channel is evaluated. According to the behavior of the secondary users,the reputation is calculated, thereby establishing a reputation system in the cognitive base station. Then, the secondary users are ranked according to the reputation status, and the licensed channels or channels of the ISM band are allocated to the secondary users according to their ranking. In the process of accessing the licensed spectrum,when the trusted user meets waiting delay requirement,the secondary user with a high reputation value has a higher access priority.Suspicious secondary users can transmit in the ISM band.Simulation results show that the proposed method can effectively improve the system throughput,reduce the handoff and interrupt probability, reduce the chance of low-reputation secondary users to access the licensed spectrum, and improve the security of the system.
    2020,32(3):394-399, DOI: 10.3979/j.issn.1673-825X.2020.03.008
    Abstract:
    In order to improve the energy efficiency of cognitive radio networks and reduce the total interference to the primary users, this paper proposed a new interference efficiency-based maximization power allocation algorithm for downlink cognitive orthogonal frequency division multiplexing access (OFDMA) networks. Interference efficiency is defined as the total rate of secondary users over the total interference to the primary users. Since the original problem is a non-convex fractional programming problem,it is difficult to obtain the analytical solution for power allocation. Based on the Dinkelbach method, the original problem is firstly converted into a convex optimization problem. Then it is solved by using Lagrange dual methods and the subgradient updating methods. Lastly, simulation results show that the proposed algorithm has good convergence,and it outperforms the traditional energy efficiency maximization-based power allocation algorithm in terms of interference efficiency and the protection for primary users.
    2020,32(3):400-410, DOI: 10.3979/j.issn.1673-825X.2020.03.009
    Abstract:
    To reduce the network congestion caused by the extra traffic due to repeated downloads of some popular multimedia files, a hybrid self-backhaul and cache (HSBC) assisted content delivery scheme is proposed. In a co-channel and full millimeter wave deployed heterogeneous network,with a ratio factor η, some small base stations (SBSs) are equipped with cache storing multimedia content according to a popularity level, whereas the rest of SBSs without cache provide the requested content for user terminals with the self-backhaul assistance from the macro base station equipped with multiple antenna array. The introduction of millimeter wave technology effectively alleviated the shortage of network spectrum. Based on the realistic direction pattern of multiple antenna systems, the average coverage probability, average area throughput, and average delay of the system are studied comprehensively. The results show that the performance gain of the HSBC assisted system over the traditional self-backhaul (TSB) assisted system depends largely on the system parameters. Thereby, an adaptive TSB-HSBC-SBS assisted model is proposed for content delivery. When the current ratio factor of SBS caches is less than the threshold, the TSB-SBS assisted model is selected. otherwise, the HSBC-SBS assisted model is used.
    2020,32(3):411-418, DOI: 10.3979/j.issn.1673-825X.2020.03.010
    Abstract:
    In order to study the impact of electrical appliance on the characteristics of low-voltage power line channel,this paper presents the two-dimensional time and frequency electrical appliance impedance measurement method based on a vector network analyzer. Through this method, the impedance characteristics of all kinds of electrical appliance are measured under different working conditions. Then, the channel characteristics of a typical power line channel scenario connecting to different types of electrical appliance loads are theoretically analyzed in combination with bottom-up power line channel modeling. According to the measurement, the same load of electrical appliance in different spatial locations affect the power line channels differently. The influence of different electrical appliance on the characteristics of power line channels is different when the load of electrical appliance is connected to the same load node. In addition, the time-varying load causes the power line channels accessing the load to present time-varying characteristics. Theoretical analysis and test results show that load impedance of electrical appliance with time-frequency changes is one of the key factors that affect the channel characteristics of low-voltage power line carrier communication.
    2020,32(3):419-425, DOI: 10.3979/j.issn.1673-825X.2020.03.011
    Abstract:
    The row weight of quasi cyclic low-density parity check (QC-LDPC) codes based on quadratic residue (QR) codes is usually large, which causes that the decoder will consume more resources on hardware implementation.Therefore,this paper designed a layered decoder based on partial-parallel structure compromised between resource occupancy and throughput. The decoder is implemented by the Layered Normalized Min-Sun Algorithm (LNMSA),which simultaneously processes consecutive n rows of a layer using a partial-parallel structure. On the storage structure of variable node posterior probability information, the continuous n information is combined into one group and the consecutive two groups are alternately stored by two random access memories(RAM). When obtaining the minimum value and the second small value, the input message is divided into 4 groups. Then, 4 minimum value are respectively computed from 4 groups and the global minimum value and second small value are obtained from them, which can effectively reduce the complexity of the comparison operation. In the test environment with code length of 2040, code rate of 0.83 and Xilinx Virtex-6 development board,the throughput of the decoder can reach 447.5 Mbit/s when working on 166.7 MHz.
    2020,32(3):426-433, DOI: 10.3979/j.issn.1673-825X.2020.03.012
    Abstract:
    Aiming at the problem that BeiDou receiver is vulnerable to interference caused by high power microwave, the circularly polarized patch antenna is used as the irradiation target, and the induced electromotive force generated by the antenna irradiation is injected into the RF front-end of the receiver based on the co-simulation of CST and ADS, the monitoring nodes are set to record circuit parameters. The front-door coupling process of narrow-band and ultra-wideband high-power microwave irradiation to the navigation receiver is analyzed through the simulation.The results show that the ultra-wideband electromagnetic pulse can cause the secondary low-noise amplifier transistor of the Beidou receiver to burn out, and the narrow-band electromagnetic pulse will cause the front-end limiting diode to break down,resulting the navigation system being unable to work. The vulnerable parts of the receiver circuit were determined and the basis for the electromagnetic protection design of the Beidou navigation receiver was provided by the study, the research method can also be used as the reference for other electromagnetic pulse front door coupling effect simulation experiments.
    2020,32(3):434-440, DOI: 10.3979/j.issn.1673-825X.2020.03.013
    Abstract:
    In singular value decomposition (SVD) of a matrix, the matrix dimension increases along with the exponential increase in the computational complexity of SVD; that reduces the real-time performance of the algorithm. To alleviate this issue, this paper proposes an improved logic design for the coordinate rotation digital computer (CORDIC) based on the Hestenes-Jacobi numerical calculation method. The logic design adopts the parallel full pipeline design idea that improves the running speed of the Jacobi plane rotation transformation. Therefore, to accelerate the computational speed of singular value decomposition of an arbitrary dimensional matrix; this paper first analyzes the numerical calculation process of SVD based on Hestenes-Jacobi method, then introduces the basic principle of CORDIC algorithm, and specifies the design of Jacobi plane rotation module based on CORDIC algorithm. Furthermore, it also uses Verilog language to realize the design and verification of the logic. To validate the concept the logic design unit is implemented on the field programmable gate array (FPGA) and Matlab toolkit. The experimental test results show that the structure can reduce the calculation time and meet the requirements of high-speed data processing.
    2020,32(3):441-451, DOI: 10.3979/j.issn.1673-825X.2020.03.014
    Abstract:
    Due to the short time to come out and insufficient parameters of GaoFen-3 satellite(GF-3) data, the existing software does not add sensor support for GF-3 data which makes it difficult to generate its orthophoto images by using existing software. To this end, a method of generating GF-3 orthophoto images based on indirect rectification is presented in this paper. Firstly, the process of satellite imaging in the region to be ortho-corrected is simulated, and the simulated GF-3 image is constructed by using DEM data which corresponds to this region through the RD model. Secondly, feature points are extracted in simulated and real GF-3 images, respectively, the feature point pairs are matched; and then the mapping relationship between the two images is established. Finally, using the mapping relationship between simulated GF-3 image and DEM data as well as real GF-3 image, orthophoto correction is completed indirectly and orthophoto image is generated. In this paper, according to the characteristics of multiple imaging modes of GF-3, the experiment for generating GF-3 orthophoto image generation is carried out with three representative imaging model and good experimental results are obtained. The comparison of corresponding pixel coordinates between real GF-3 image and simulated GF-3 image shows error in x and y direction is less than one pixel. A high precision result has been obtained. The imaging features of SAR system are fully taken into account in the proposed method. Results of different terrain details are good. The experimental results of qualitative and quantitative analysis verify the feasibility and effectiveness of the proposed method.
    2020,32(3):452-458, DOI: 10.3979/j.issn.1673-825X.2020.03.015
    Abstract:
    Aiming at the problem that most existing fine-grained image classification algorithms ignore the correlation between local localization and local feature learning, this paper proposes a fine-grained image classification algorithm based on ensemble methods of transfer learning. The classification network of the algorithm consists of region detection classification and multi-scale feature combination. The regional detection classification network obtains local regions by class activation mapping (CAM), and learns fine-grained features from the localized regions in a mutually reinforcing way. Finally, the local features are combined as the final feature representation to classify. The classification network combines the proposed ensemble methods of transfer learning in the training process,and ensemble the local training model by stochastic weight averaging method based on transfer learning to obtain a better classification model. Experiments on datasets CUB-200-2011 and Stanford Cars show that the algorithm has better fine-grained classification results than most of the previous algorithms.
    2020,32(3):459-468, DOI: 10.3979/j.issn.1673-825X.2020.03.016
    Abstract:
    Due to the face recognition problem of illumination, pollution and occlusion in the test images and training images, a study of group sparse representation face recognition method based on robust principal component analysis with(GSR-RPCA)is proposed. Firstly,transferring the face image from the spatial domain to the logarithmic domain to enhance the contrast of the face image, and decomposes the clean low-rank partial face image from the training sample image matrix D by the structural incoherence robust principal component analysis algorithm. The matrix A and the error image matrix E are used to enhance the discriminating ability of the recovered data. Then, the low rank mapping relationship matrix P between A and D is learned, and P is used to map the occlusion test samples to their potential subspaces to get a clean test sample y. Finally, the group sparse representation coefficient of y is calculated, and the test face is identified by using the class association reconstruction residual to obtain the category of the test face. Experimental results on CMU PIE, Extended Yale B and AR database verify the effectiveness and robustness of our method.
    2020,32(3):469-476, DOI: 10.3979/j.issn.1673-825X.2020.03.017
    Abstract:
    In order to obtain the optimal attitude of uniaxial magnetic sensor in the location of pig labeled with magnets, numerical simulation is adopted to carry out modeling analysis of the horizontal pipe and the bent pipe, take a series of measuring points at the measuring surface directly above the pig and study the magnetic fluctuation values of each measuring point in multiple directions. The best detecting direction can be obtained by comparing the fluctuation value. According to the difference laying mode of the actual pipeline, the horizontal pipeline is analyzed firstly, and it is found that when the pig passed the measuring point, the fluctuation Perpendicular to the pipeline axis is the largest to be effectively detected by the uniaxial magnetic sensor. Then two variables,pipeline inclination and pipeline deflection are used to describe the bent pipeline, the results indicates that the largest fluctuation is in the direction perpendicular to the pipe.And the existence of both inclination and declination proves that the uniaxial sensor should also be installed perpendicular to the pipeline. Finally, relevant equivalent experiments are carried out to verify the numerical simulation results. So the conclusion is that: the measurement direction of the uniaxial magnetic sensor should be perpendicular to the direction of the pipeline during the detection.
    2020,32(3):477-486, DOI: 10.3979/j.issn.1673-825X.2020.03.018
    Abstract:
    Aiming at the rescue or escape of trapped people after a confined environmental accident such as an underground mine or tunnel, this paper proposes a trusted anchor node selection algorithm through constructing a wireless sensor network based on hybrid channel model to realize the accurate location estimation of wireless sensor network nodes in sparse anchor node environment after an accident, generate the optimal escape rescue path, and realize real-time navigation. The simulation results show that the algorithm has higher node positioning accuracy than the existing research in the sparse anchor node scenario, and can accurately search the rescue or escape path based on the dynamic obstacle recognition.
    2020,32(3):487-494, DOI: 10.3979/j.issn.1673-825X.2020.03.019
    Abstract:
    Balanced iterative reducing and clustering using hierarchies(BIRCH) is a comprehensive and hierarchical clustering algorithm. However, algorithm BIRCH sets a unified space threshold for clusters in leaf nodes, and where it inserts the data is determined by the distance between data and clusters,thus ignoring the relationship between clusters. In addition, when splitting nodes, the algorithm selects two clustering feature with the maximum distance as its sub-clusters,which is used by other clustering to splitting, thus resulting in the wrong classification of sample data between clusters and ignoring the relationship between clustering features. To deal with the two problems of BIRCH algorithm, an adaptive algorithm based on threshold is proposed in order to solve unified space threshold of the original algorithm, and the original algorithm is improved by combining Naive Bayesian algorithm to solve the problem of clustering features. A simulated experiment on the improved BIRCH algorithm and the traditional one shows that the clustering effect of the BIRCH algorithm is obviously improved under the loss of efficiency, and compared with other methods,the proposed method has good performance and is robust across data sets.
    2020,32(3):495-502, DOI: 10.3979/j.issn.1673-825X.2020.03.020
    Abstract:
    Aiming at the limitations of existing unbalanced data processing methods, a hybrid sampling method considering boundary sparse samples is proposed. By calculating the boundary factor of each sample to identify the boundary points, the sample space is divided into boundary and non-boundary domains, and negative samples in the non-boundary domain are undersampled, and due to the sparsity of the samples on the boundary domain.MD-SMOTE algorithm,SMOTE based max distance,is performed for positive samples on it,which maximumly reserve the information of positive samples and ultimately achieves a basic balance between the two types of samples. The Recall, F1-value, G-mean and AUC values were used as evaluation indicators. The CBSS-HS+SVM algorithm was used to verify the validity of the datasets on five different balances, and compared with the classification model of the other four combined models. The results show that the CBSS-HS algorithm presented in this paper has a good performance on different evaluation indexes,with an average increase of 4.6%. Therefore, this method can be used as an effective means of processing unbalanced data.
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    2008,20(6):682-685, DOI: 10.3979/j.issn.1673-825X.2008.06.013
    [Abstract] (1349) [HTML] (0) [PDF 1.61 M] (24658)
    Abstract:
    In order to reduce the interference of wireless communication and to realize the multi-system sharing and transmitting receiving sharing for multi-wireless communication systems, the antenna must work under broadband and different frequency. In this paper, a novel dual-band microstrip antenna with good performance is analyzed and designed, and this antenna has been simulated by using the software HFSS 10.0. The simulation result shows that the frequency channels of the antenna are 1.67~1.84 GHz and 2.33~2.53 GHz, and the relative bandwidths of the antenna are 9.71% and 8.23%, respectively. This antenna can be used in RF communication as a multi frequency antenna.
    2008,20(5):624-626, DOI: 10.3979/j.issn.1673-825X.2008.05.029
    [Abstract] (1096) [HTML] (0) [PDF 1.11 M] (6990)
    Abstract:
    Traveling salesman problem (TSP) is of important theoretical and practical significance and applied widely in engineering practice. The genetic algorithm, ant colony algorithm and simulated annealing were adopted to solve the traveling salesman problem, and the Chinese traveling salesman problem was chosen to simulate. Through the comparison of these three algorithms' advantages and disadvantages, their different applications were gained: the ant colony algorithm is suitable for slow and accurate solving, the simulated annealing applies to quick and accurate solving, and the genetic algorithm is for quick but low accurate solving.
    2012,24(3):319-325, DOI: 10.3979/j.issn.1673-825X.2012.03.010
    [Abstract] (1623) [HTML] (0) [PDF 1.68 M] (5581)
    Abstract:
    Scanning mechanisms and recognizing process of remote electrical tilt antenna are analyzed, and property and type of remote electrical tilt antenna device searching algorithm is concluded, and 4 feedback states of devices in a scan cycle are summarized and the coping methods are presented, so to provide theoretical basis for an algorithm to improve and optimize the device searching efficiency. Layered analysis method to the various searching depth is taken in the algorithm realization and the impacts on the total scanning time with different number of the devices and mask shift bits are researched, and design method of more optimized algorithm is achieved, and device searching algorithm based on repeated scanning and the hybrid mask shift bits on AISG2.0 protocol is put forward. Simulation and practice show that the proposed algorithm can effectively reduce RET device recognition time and increase device search efficiency.
    2010,22(4):395-399, DOI: 10.3979/j.issn.1673-825X.2010.04.001
    [Abstract] (3081) [HTML] (0) [PDF 1.08 M] (4335)
    Abstract:
    In 3GPP LTE (long term evolution) physical layer protocol, Both CQI (channel quality indicator) and HARQ-ACK (hybrid automatic repeat request acknowledgement) adopted a method called super code based on Reed-Muller. It is similar to the encoding of TFCI (transport format combination indicator) in TD-SCDMA physical layer protocol. But the coding matrix used more complex interleaver technology and increased more masks in 3GPP LTE. It made receiver s decoding difficult. According to the characteristics of coding matrix, this paper used FHT (fast Hadamard transformation) and gave an effective decoding algorithm of Reed-Muller. Simulation results show the effectiveness of the algorithm, which has been applied to LTE-TDD wireless integrated test instrument.
    2013,25(1):30-38, DOI: 10.3979/j.issn.1673-825X.2013.01.005
    [Abstract] (2426) [HTML] (0) [PDF 2.62 M] (4321)
    Abstract:
    Distributed storage system introduces redundancy to increase reliability, and erasure code is used widely in distributed storage system. When a node fails in the distributed storage system, a new node is introduced to repair the failed one. When using erasure code, repairing the failed node often requires a large amount of data transfer. Regenerating Code was proposed to reduce the cost of repair bandwidth. Regenerating Code reduces the amount of data uploaded by each helping node by transferring a linear combination of the data it stores to the failed node in the repair process. In this paper we first review the basic idea of regenerating code. Then we summarize the code constructions of both the one by one and cooperative regenerating code. At last we talk about the future research direction.
    2010,22(1):112-117, DOI: 10.3979/j.issn.1673-825X.2010.01.025
    [Abstract] (5796) [HTML] (0) [PDF 1.93 M] (4211)
    Abstract:
    Since Mean-Shift (MS) tracking algorithm always loses tracking objects and the particle filter tracking algorithm costs huge computation, a novel two-step multiple targets tracking algorithm was proposed. Firstly, a candidate object was gotten by Mean-Shift (MS) tracking algorithm. Then, the tracking result would be verified by particle filter technique when the object couldn't be traced exactly. Experimental results show that this approach can maintain the efficiency of MS algorithm and the powerful ability of particle filter technique, so it is of high practicability.
    2010,22(2):174-178, DOI: 10.3979/j.issn.1673-825X.2010.02.011
    [Abstract] (2481) [HTML] (0) [PDF 1.54 M] (4103)
    Abstract:
    High data speed and capacity in LTE makes the contradiction between spectrum resources and business capacity more outstanding. This paper first introduces the robust header compression (ROHC) and its application in PDCP sublayer in 3G system. Then, the paper analyses the process and the principles of implementation. Combined with the process of PDCP header compression, the framework realization of ROHC procedure was discussed separately from compress part and decompress part. Finally, an improved decompression algorithm was put forward to enhance the robustness, especially for great quantity of packet loss.
    2010,22(1):63-70, DOI: 10.3979/j.issn.1673-825X.2010.01.015
    [Abstract] (6549) [HTML] (0) [PDF 893.46 K] (4096)
    Abstract:
    In this paper, vertical handoff algorithm for heterogeneous network was studied through the integration between cellular network and wireless local area network (WLAN). The network-end and user-end parameters affecting algorithm performance were analyzed in detail, including the parameter definition, the range of parameters in different access networks, the relations between different parameters and the normalization problem. According to the parameter effects on handoff algorithm and system performance, these parameters were categorized as handoff conditional parameters, handoff decision parameters and handoff assistance parameters. Based on the parameter classification, a new weight variable handoff algorithm was proposed. This algorithm adopts the weights that are adaptive to the characteristics of user traffic, user mobility model and user preference to access networks. Compared with existing vertical handoff algorithms with fixed weights, this novel algorithm takes into account user characteristics and QoS requirements, and it is able to improve user satisfaction level and system performance.
    2012,24(4):411-415, DOI: 10.3979/j.issn.1673-825X.2012.04.004
    [Abstract] (2093) [HTML] (0) [PDF 993.83 K] (3747)
    Abstract:
    In this paper, we introduce a relay to the SISO symmetric wireless interference network, and apply interference alignment technology to this network. By comprehensively considering all the users' performances, we propose an optimized distributed interference alignment algorithm based on the biggest chordal distance criterion. Applying the optimization algorithm, we can realize interference alignment only requiring two time slots extension for the three users SISO interference network, and achieve 1/2 Degree of freedom for each user. Simulation results justify that using relay and optimization algorithm can significantly improve the capacity and energy efficiency of the system.
    2010,22(6):703-707, DOI: 10.3979/j.issn.1673-825X.2010.06.003
    [Abstract] (2063) [HTML] (0) [PDF 1.66 M] (3714)
    Abstract:
    Terahertz(THz) lies between far-infrared and microwave in electromagnetic spectrum with frequency form 0.1 to 10 THz. Terahertz is believed to be the master technology of international electronics and information science, and to be the bridge between micro-electronics and macro wavelength. THz contains great prospect in the electronic, information, life, national defense, aerospace, etc, and has formed a worldwide research climax. This article introduces the main character,primary researchs and applications of Terahertz.
    2009,21(3):432-434, DOI: 10.3979/j.issn.1673-825X.2009.03.022
    [Abstract] (5815) [HTML] (0) [PDF 1.19 M] (3577)
    Abstract:
    The attitude arithmetic is one of the important parts in strapdown inertial navigation system (SINS). Based on traditional three order recursive Taylor expansion and four-order Range-Kuttle method, another effective method four-order Taylor expansion was proposed. Under the typical circular cone rotation condition, the three algorithms were simulated on angle error. Considered precision and speed, the simulation result proves that the four-order recursive Taylor expansion is better than the three-order recursive Taylor expansion and the four-order Range Kuttle method. And this method offers reference for developing attitude arithmetic of SINS.
    2010,22(2):131-134, DOI: 10.3979/j.issn.1673-825X.2010.02.002
    [Abstract] (5289) [HTML] (0) [PDF 1.45 M] (3488)
    Abstract:
    Timing error sensitivity is the characteristic of orthogonal frequency division multiplexing (OFDM) system. Using superimposed training sequence, a novel weak power training sequence was proposed. The training sequence, superimposed on the cyclic prefix, has lower power than the reduplicate structure training sequence. The method can reduce the bit error rate of the system affected by the superimposed training sequence. It can make the sidelobe of the correlation lower and improve the timing synchronization accuracy by using the structural characteristic. The timing synchronization accuracy using the structure proposed at the low SNR is higher than that of the reduplicate structure. The performance of the method is checked by simulation.
    2009,21(6):704-709, DOI: 10.3979/j.issn.1673-825X.2009.06.002
    [Abstract] (6380) [HTML] (0) [PDF 1.63 M] (3480)
    Abstract:
    Based on the 3GPP long term evolution (LTE) Release 8 standard released recently, the mechanism of designing and realizing radio link control (RLC) acknowledged mode(AM) transmission mode in LTE radio protocol stack was studied. The structure of air interface protocol stack in LTE radio access network was introduced, then the design principle of RLC AM transmission mode was analyzed, and a method was proposed to realize the AM transmission mode in LTE air interface protocol stack software based on 3GPP standard.
    2008,20(2):194-196, DOI: 10.3979/j.issn.1673-825X.2008.02.014
    Abstract:
    The design method of a dual-section transmission line transformer with broadband is studied. This transformer can achieve the ideal impedance matching between two arbitrary frequencies. In ideal conditions, all parameters can be obtained by solving the equations which are satisfied with the transformer. If using the optimization designed by Ansoft Designer, the broadband impedance transformer can be gained. Simulation results verify the validity of the design.
    2013,25(1):101-110, DOI: 10.3979/j.issn.1673-825X.2013.01.017
    [Abstract] (1995) [HTML] (0) [PDF 1.31 M] (3154)
    Abstract:
    Traditional classification methods are based on the assumption that the training sets are well-balanced, however, in real case the data is usually unbalanced, and the classification performance of the traditional classification is always restricted. A detailed overview of domestic and foreign classification algorithms from the data level and algorithm level is provided in this paper. And through simulation experiments to compare the classification performance of a variety of unbalanced classification algorithm on six different data sets, it is found that the improved classification algorithm has varying degrees of improvement for overall performance. The paper concludes with a list of problems which need solving for the development of unbalanced data classification.
    2008,20(2):132-138, DOI: 10.3979/j.issn.1673-825X.2008.02.002
    Abstract:
    Gaussian minimum shift keying (GMSK) is a constant envelope modulation with continuous phase, and achieves good power-bandwidth efficiency. According to the basic principle of GMSK signal, the GMSK demodulation based on Viterbi algorithm and its performance analysis are presented by describing the signal state and the computation of the branch metric in trellis diagram. Simulation result indicates that the proposed algorithm possesses good performance of anti-noise and anti-multipath. And it can obtain 7 dB gains under the same condition of bit error rate of 10-3 than that of the 2-bits differential demodulation.
    2009,21(4):518-522, DOI: 10.3979/j.issn.1673-825X.2009.04.013
    [Abstract] (4174) [HTML] (0) [PDF 470.98 K] (3014)
    Abstract:
    Computer forensics is an important method for solving civil dispute and fighting against computer crime. Hence, it is valuable to realize computer forensics by utilizing intelligent information processing technology. The development and problems for intelligent forensic technologies were discussed from the angle of formal forensic analysis method, user behavior analysis, intelligent image forensic and intelligent video forensic. Future trends of intelligent forensic technology were analyzed.
    2013,25(1):24-29, DOI: 10.3979/j.issn.1673-825X.2013.01.004
    [Abstract] (2410) [HTML] (0) [PDF 2.23 M] (2962)
    Abstract:
    The OpenFlow network, which separates the control plane from the data plane, provides a real platform for innovation in the Internet. The working processes of the OpenFlow switch are analyzed, and the performance of the PC-based OpenFlow switch is measured and analyzed too. The experimental results depict that no matter for the TCP or the UDP packet transmitting, the PC-based OpenFlow switch can have a good performance in the moderate scale OpenFlow network. However, the throughput will decline rapidly when lots of short packets arrive at the switch. And the flow entries constructing for the high-speed UDP packets will depress the performance of the OpenFlow network too.
    Abstract:
    For improving the convergence performance of antennas beamforming algorithms, this paper proposes a new MIMO-SDMA of smart antennas beamforming algorithm based on research of optimization vector value of phase-amplitude perturbations by improved Memetic algorithm. Simulation results show that this algorithm has good convergence performance and convergence efficiency; the system based on the algorithm can adjustably suppress interferers by placing nulls at the directions of the interfering sources and provide a maximum main lobe in the direction of the desired signal at the same time; thus, the signal to interference ratio of the system is increased, and the uplink MIMO-SDMA can be achieved.
    2012,24(4):420-425, DOI: 10.3979/j.issn.1673-825X.2012.04.006
    [Abstract] (1990) [HTML] (0) [PDF 1.81 M] (2824)
    Abstract:
    In this paper, the impacts of mutual coupling on the performance of MIMO wireless channel are analyzed. From the analysis of the antenna model by network equivalent analysis, the impedance matrix and the mutual coupling matrices of transmitter and receiver are obtained. A general expression of the spatial correlation between a pair of mutually coupled antennas is explicitly derived, and the conditions under which mutual coupling has no effect on the spatial correlation are also identified. The effects of mutual coupling on the parallel antenna array and the collinear antenna array are investigated. Simulation results show that the impacts of mutual coupling on parallel antenna array and collinear antenna array are quite different in the performance of MIMO channel, and the performance of MIMO system affected by mutual coupling can be improved effectively by properly selecting antenna array.

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