- EI核心期刊
The problem of synthesizing a planar 4-bar linkage with given two fixed pivots such that the coupler curve passes through five given points is considered with the Groebner-Sylevester hybrid approach. Firstly, the closed-form equations of the single point are constructed. Next, the reduced Groebner basis under degree lexicographic ordering for the closed-form equations is obtained using computer algebra. Selecting 23 Groebner bases from 89 ones, a 23×23 Sylvester’s matrix can be constructed. A 36th degree univariate equation is obtained directly from the determinate of the matrix. The same result can be obtained with continuation method. A numerical example is given and it verifies that the problem has at most 36 solutions in the complex field.
Aiming at nonlinearity measurement error of detection system caused by the change of the environment temperature, a new Chebyshev fitting algorithm is proposed for detection system temperature compensation. The temperature compensative technique can be validated by the post-correction output voltage curve and the correction output voltage curve showed in the same figure. The curves are gained when Square-law detector system works on the dynamic range. Utilizing soft data processing to implement the Chebyshev algorithm, not only the measurement error is decreased, but the system noise caused by the additional electron device is also eliminated. Using compensative technique in the microwave radiometer, the accuracy and linearity of such system is optimized, and the instrument is more reliable for the real-time observation on airborne or ground platform.
Modeling radio frequency micro-electro-mechanical system (RF MEMS) device for electromagnetic analysis is difficulty, especially with small feature size and movable structures. A new electromagnetic modeling method, deformed alternating-direction implicit method finite difference time domain (DADI-FDTD), is proposed. The dynamic equation of motion is dispersed in time domain using finite difference methods (FDM). Numerical dispersion is discussed in the three-dimensional ADI-FDTD method. A new algorithm, dielectric interpolations, is presented, it is capable of solving the conflict of the time and special steps between the mechanical portion and electromagnetic (EM) portion. And it’s able to implement the EM modeling in time domain of complex three-dimensional structures. Simulation results demonstrate the feasibility of the method.
Based on analysis of application protocols, a group of multi-flow characteristics with low complexity, high quality is proposed to mitigate the problem of low recognition rate and high implementation complexity associated with the traditional flow classification algorithms using single flow statistics. These characteristics can effectively identify peer-to-peer (P2P) traffic in network flow classification, and improve the recognition rate of the traditional algorithms. They also enable the use of multinomial logistic regression algorithm to classify the network flow, and reduce the complexity of the traditional algorithms. Experiment results show that the proposed characteristics can achieve good generalization, and only need a small number of training samples to get a model that can maintain good performance for a long time.
Aimed at 9-degree of freedom（DOF） hyper-redundant module robot in intra-vehicular robot system, attention is given to the avoiding joint limits as an optimal mark. Two different iterative algorithms considering fault-tolerance for trajectory planning of redundant robot in Cartesian space are then proposed by using the method of differential locomotion. The first algorithm is for linear-path in which the pose of manipulator can be changed, the second is for circular-path in the plane decided by three noncollinear arbitrary points in the space. Experiments on the specimen robot platform are performed to validate the above algorithms. And the hyper-redundant robot’s actions, such as pulling drawers, grapping club-shaped stuff along linear-path and opening doors along circular-path are realized.
Drawing idea from the quantum entanglement swapping, a quantum (n-1，n)threshold scheme is proposed. By local unitary operation and entanglement swapping, the sender can transmit the piece of secret to the participant. To ensure the qubits be transmitted between two parties in a secure manner，the sender switches randomly the message mode to control mode asymmetrically. A security analyses on this scheme is then made. It shows that this scheme is secure. Compared with the quantum secret sharing scheme with Greenberger-Horne-Zeilinger (GHZ) state, the scheme achieves a high efficiency. Furthermore, since the Einstein-Podolsky-Rosen （EPR） pair was used, the experimental realization of the protocol becomes feasible
The integration of the middleware based on Pub/Sub scheme and the multicast routing protocol of mobile Ad-hoc network was researched, and a multi-hop routing subscription protocol named publish/subscribe multi-hop routing （PSMR） was proposed. PSMR helps to distribute the publisher’s data to subscribers and cooperate with the layer of Pub/Sub scheme as well as the layer of routing work to distribute the data to make the transmission more reliable. Simulation conclusion shows that PSMR can greatly reduce the number of packet transmission.
The effect of channel-spacing on differential phase shift keying （DPSK） systematical performance was analyzed and optimized through VPItransmission maker simulation, aiming at the severe distortion of DPSK signal to narrow channel-spacing for its broad spectrum. It is found that the delay time of the DPSK Mach-Zehnder delay interferometer （MZDI）-demodulator will be less than 1-bit duration for the 40 Gbit/s dense wavelength-division multiplexing（DWDM) system with 50 GHz channel-spacing, and become shorter according to the narrower optical filter bandwidth. Furthermore, the system achieves the optimal transmission performance by matching the variation of the optical add-drop multiplexer (OADM) series, with a method of feedback controlling of the delay time according to the monitored transmission performance indications.
The relationship between link scheduling scheme and the performance of user fairness and delay guarantee is detailed analyzed. In order to guarantee user fairness and reduce end-to-end delay, the concept of “link scheduling periods” and “link hop degree” are introduced. One suboptimal user fairness and delay guarantee link scheduling algorithm is proposed based on the user fairness optimization problem model. To guarantee the performance of system throughput, both the spatial reuse and link quality are considered. Theoretical analysis and simulation show that the proposed algorithm can enhance the performance of user fairness and delay effectively with a certain system throughput guarantee.
In peer-to-peer network, there exist lots of free riders, whose passive behaviors decrease the efficiency and reliability of search. A new search algorithm named credit model based restricted random walk (CMRRW), which is based on the credit model, is proposed to solve this problem. The credit model is applied to evaluate the reliability of the peers. The query reliability rate is gained to reflect the peer’s history query success rate and the routing efficiency of its neighbors. In our solutions, when the peer selects neighbors to forward the query message, the neighbors with higher credit and history hit rate will be selected in prior order. Simulation results indicate that CMRRW shows good performance.
XU Fang-min1,2, TAO Xiao-feng1,2,WANG Ying1,2, ZHANG Ping1,2
To improve cell-edge user (CEU) performance, a new soft fractional frequency reuse（SFFR） scheme is introduced. Unlike other frequency reuse schemes, it supports space diversity and space multiplexing because multi-cell and multi-CEU form a generalized multi-input multi-output (MIMO) system. On the other hand, CEU performance is improved by interference coordination through frequency programming based on soft fractional frequency reuse. It provides a good chance to use space multiplexing than space diversity. For getting a further performance, space multiplexing is adopted. In the meantime, cell-center users are still served by one cell. Simulation results show that the novel fractional frequency reuse scheme can support generalized MIMO technique and improve CEU performance significantly.
According to the characteristic of uncertainty information in the information system risk analysis process, and information system risk measure using entropy theory, a risk analysis algorithm using entropy-weight coefficient is presented. When combining qualitative analysis and quantitative calculation, a model of information system risk analysis is constructed. Finally, an instance of the risk analysis approach based on the model is analyzed and validated, which demonstrates the rationality and feasibility of the model. So it provides a new method for information system risk analysis.
A nonuniform transmission line is modeled for multilayer plates and an effective shielding is obtained by matrix theory. Owing to discontinuity of nonuniform transmission line, it is suited for modeling multilayer plates regardless of re-reflection between plates. Matrix presentation can benefit calculation using programming. A general formula applicable to analyze arbitrary multiplayer plates shielding is proposed. Special cases of double and fourfold shield are investigated. The accuracy of this method has been validated by comparison to other analytical methods.
Subcarrier power allocation in broadband orthogonal frequency division multiplexing（OFDM） relaying system is addressed for the nonregenerative and regenerative relaying mode. Firstly, based on the two-hop nonregenerative relaying system, an equivalent channel gain model for the two-hop regenerative relaying system is induced. Afterwards, the overall transmit power is allocated to the subcarrier pairs using water-filling approach. Finally, the above conclusions are generalized to the multi-hop relaying system. Simulation shows that the proposed power allocation algorithm can achieve a higher system capacity than both the direct transmission system and uniform power allocation scheme, and the multi-hop relaying system can efficiently enlarge the coverage.
That a presented proposal of efficient certificateless signature scheme is insecure against public key replacement attack is demonstrated. It is shown that an adversary who replaces the public key of a signer can forge valid signatures for the signer without knowledge of the signer’s private key. Then the scheme is improved by replacing the original public key with a public key pair. It enables a verifier to check the validity of a signer’s public key pair by simplifying the signature construction. The improved scheme is proven secure against existential forgery under the random oracle model.
A joint optimization strategy for relay selection and power allocation is proposed to optimize the performance of cooperative communication system. Convex optimization method is used to implement the algorithm, which optimally distributes power among the source and relay nodes. Both theoretical analysis and simulation results indicate that the proposed strategy notably improve system performance and energy efficiency with low implementing complexity, thus can be effectively used in cooperative communications based on relaying transmission.
A privacy-preserving point-line relation determination protocol based on additive homomorphism encryption is developed in semi-honest model. The privacy-preserving point-line relation determination protocol can be used to solve many privacy-preserving computational geometry problems, such as segments intersection problem and point inclusion problem. The privacy-preserving point-line relation determination protocol can be also used to determine either the point is at the positive side, negative side, or on the line privately. Further more, the privacy-preserving segments intersection protocol can be used to determine two lines supplied by different users intersect securely; and the privacy-preserving point inclusion protocol can be used to determine the relation of a point and a polygon supplied by different users. Finally, the correctness, security and efficiency of these protocols are analyzed.
After analyzing current technology background, a kind of unified modeling language（UML）activity model checking mechanism based on rule database in Telecom services is proposed. By separating the model checking rules and the model checking engine, the scalability and agility of the checking mechanism are improved. When using in the model driven architecture （MDA） service platform, the correctness and high-performance of the model checking software based on the mechanism are also testified.
With characteristic of enhanced multimedia broadcast/multicast service (E-MBMS) networks, a time-frequency two dimensions (2-D) resource allocation strategy based on power-saving is proposed. In time domain, the proposed algorithm minimizing power consumption merges different E-MBMS sessions and minimizes the total number of receiving time-slots. Allocation in frequency domain is aimed at maximizing system throughput under the condition in which the target rates can be attained. The proposed scheduling algorithm is done in each orthogonal frequency division multiplexing (OFDM）frame, it allocates time-frequency units to different sessions. Simulation shows that the efficiency of proposed allocation algorithm can obviously reduce power consumption of MBMS handsets and will be with significant higher fairness with throughput being close to the upper bound of optimum method.
A multi-antenna spectrum sensing technique based on cyclostationary characters was proposed to improve the sensing performance in cognitive radio. After estimating the channel frequency response from the spectral correlation function (SCF) of each antenna, the new method combines the multiple antenna signals in frequency domain to detect the spectrum of combined signal. The closed-form expression for the signal noise ratio (SNR) of combined signal’s SCF and simulation results show that the technique is capable of achieving full spatial diversity in spectrum sensing.
A new kind of discrete signal with good periodic correlation function is proposed. It is binary array pairs with two-level autocorrelation. The definition of binary array pairs with two-level autocorrelation is presented. Its transformation properties and Fourier spectrum characters are discussed. To reduce the searching range and improve the searching efficiency of binary array pairs with two-level autocorrelation, its existence conditions are studied. And folding construction between binary array pairs with two-level autocorrelation and binary sequence pairs with two-level autocorrelation is given out.
The insufficient of current traffic identification technique was analyzed, and then a heuristic traffic identification method based on trusted list was proposed. This method uses a “memory” technique, adds the discerned connection into a trusted list. Moreover, a real-time optimized method was developed to make sure that the more active connections can be measured to primarily in the trusted list all the time, thus will accelerate the traffic identification speed and improve the accuracy. The experiment results show that this method can identify the encrypted traffic perfectly, and more effectively than existed methods.
A novel Traffic-aware and energy efficient routing (TEER) protocol based on dynamic source routing（DSR） is proposed in wireless mesh network (WMN). TEER exploits information originated from media access control （MAC） and physical layer as well as that from application layer. To balancing energy efficiency and bandwidth quality of service （QoS） requirement, an integrated metric MTEER is proposed to denote the energy and transmission state of the node. TEER combines the available link bandwidth, duty cycle of load queue and the residual energy of node acquired by statistic methods. Simulation results demonstrate that TEER outperforms the performance than that of energy-aware multi-path routing protocol (EMRP）and dynamic source routing (DSR) in terms of network lifetime and throughput.
An iterative formula of the amplitude estimate is presented based on Cholesky decomposition for the signal power order. The decision arrangement in the order of decreasing amplitude is implemented by permutation matrix in decorrelating decision-feedback multiuser detector, it will make the strongest user get a very first decision. Performance analysis shows that the decision arrangement can improve the bit error rate (BER) performance of the detector. The simulation results accord with theoretical prediction which summarizes that the decision arrangement will enhance the BER performance of the weaker user and equalize that of the whole system.
Under summarizing the characteristics of pulse noise, the pulse coupled neural network (PCNN) is combined with gray-scale morphology, and a new pulse noise removing algorithm based on PCNN and gray-scale morphology is proposed. Firstly, the noisy points are located using the synchronous pulse burst property of PCNN, then, are processed using the gray-scale open-close filtering. Finally the algorithm is compared with median filtering, gray-scale open-close filtering and with the algorithm combined PCNN with median filtering. Experimental results show that the proposed algorithm performs well。However，it is at a cost of more calculating time than median filtering and gray-scale open-close filtering. But, with similar results, it spends less time than that of the algorithm combined PCNN with median filtering.
In the IEEE 802.11 distributed coordination function based wireless local area network (WLAN), a new downlink access scheme optimal power saving mode (OPSM) is proposed to solve the problem of over contention after beacon transmissions. To maximize the number of stations which contend the channel successfully, OPSM configures the traffic indication map (TIM) fields in beacon frames to constrain collisions. The downlink priority differentiation degree α is defined to describe the quality of service (QoS) gap between different services. Furthermore, the power consumption models of downlink constant bit rate service with standard 802.11 PSM and OPSM are built. Analysis and simulation results validate the performance improvement and the priority differentiation by configuring α.
A novel fast intra prediction algorithm for H.264 is proposed. The nine Intra_4×4 modes are divided into three classes, the suitable mode class for current 4×4-block is predicted using the mode classes of neighboring left and up blocks. A novel Intra_4×4 mode selection method is designed based on the derived sum of absolute values of index-weighted integer transform coefficients. The quasi-stationary of locations of Intra_16×16 macroblocks (MB) in successive I-frames is exploited to reduce the computational complexity of Intra prediction. Mode selection for two chroma 8×8 blocks is accelerated based on the mode correlations between luma blocks and chroma blocks in one MB. Experiments show that the proposed algorithm can save 25% encoding time on average compared with Joint Video Team（JVT）-G013, while with better rate-distortion efficiency.
Two Hybrid Automatic Repeat Request（HARQ） protocols for relay cooperative Rayleigh fading systems are proposed, they are relay-controlled and destination-controlled protocols, the control on each side is based on the outage probability. Numerical analysis and simulation under the slow fading channel show that the lower average received signal noise ratio（SNR） of the relay, and good performance gain will be got in relay-controlled HARQ protocol. In the destination-controlled HARQ protocol, when the uplink qualities of the source and relay are worse, the average received SNR of the destination will become lower, the systems performance can be improved efficiently.
A new spectrum sensing mechanism based on flexible sensing period（ FSP） is proposed to control the cost of the sensing in the medium access control（MAC） layer of cognitive radio networks. The cognitive radio (CR) users can make a balance between the unexpected time and the sensing count by utilizing the statistic information of licence users and a “period control factor”, that will reduce the cost of sensing. Simulation results show that FSP can give a better performance than the typical fixed sensing period mechanism.
The problem of tolerance of radar signal sorting is analyzed in modern electronic warfare that faces more complex and dense pulses environments. It is becoming a vital factor to improve the efficiency of sorting of the conventional multi-parameters signal sorting system. According to the idea of statistics learning theory, a segment clustering radar signal sorting method is presented based on cascade coupling and support vector clustering (SVC). It prevents tolerance from affecting radar signal sorting. Experiments show that the sorting method presented is good for raising the efficiency to overcome the tolerance of radar signal sorting.
An optimal log-likelihood ratio (LLR) ordering algorithm used in the tree search algorithm is presented. A simplified LLR ordering scheme employed in uncoded systems and an exact LLR ordering scheme employed in coded systems are proposed. The proposed ordering algorithm not only utilizes the channel state information, but also receives signal as well as a priori information from the decoder, thus the transmitted signals are detected in the order of their reliability information. Simulation shows that LLR ordering algorithms achieve significant performance gain in uncoded systems and a faster convergence in coded systems.