- EI核心期刊
A new p-cycle algorithm was proposed to improve the protection success ratio for asymmetric traffics in mesh optical networks. The proposed algorithm was simulated in Pan-European COST239 network environment under asymmetric dynamic traffic model. The experiment shows that the proposed algorithm has lower capacity redundancy and higher utilization rate of configured resources than that of traditional p-cycle methods. The network performance can be significantly improved when this algorithm is implemented under single-link failure circumstances. The system behavior is analyzed under different traffic volumes, and the configuration strategy is also investigated for the heavy-load and light-loads network respectively.
To be able to represent the whole hierarchical phrase structure, 10 types of Chinese chunks are defined. A method of Chinese shallow paring based on support vector machines is presented. Conventional recognition techniques based on machine learning have difficulty in selecting useful features as well as finding appropriate combination of selected features. SVMs can automatically focus on useful features and robustly handle a large feature set to develop models that maximize their generalizability. On the other hand, it is well known that SVMs achieve high generalization of very high dimensional feature space. Furthermore, by introducing the kernel principle, SVMs can carry out the training in high-dimensional space with smaller computational cost independent of their dimensionality. The experiments produced promising results.
Based on Greenberger-Horne-Zeilinger（GHZ） state, a controllable quantum secret sharing scheme was proposed. In this scheme, the quantum correlations among the three particles in a GHZ state and the characteristics of the Hadamard gate were exploited sufficiently. Bob and Charlie could obtain the joint key by sharing GHZ states. The Hadamard gate ensured the protocol controllable and secure. One GHZ state could be used to share three bits of message on average. Because all the quantum states are transmitted unidirectionally, and all particles except for the checking ones are used to transmit the joint key, this protocol has the advantage of high intrinsic efficiency, which approaches to 100% in theory.
Most statistical-based Chinese chunking researches was inspired by English chunking of CoNLL2000. After representing chunks within the scheme of tags for words in a chunk (BIO), chunk identification task was cast as word sequence tagging and tackled as multi-classification problems. For sake of decreasing classification complexity, a decomposed chunking approach was proposed: first, chunk boundary identification, and then chunk type identification. The vital problem of Chinese chunking is actually boundary identification. Cascade chunk identifiers were built based on conditional random fields (CRF). The experimental dataset was extracted from Chinese tree bank 5.1 (CTB5.1). As to the features selection, some methods often used in Chinese word segmentation were borrowed to chunking task. On 5 cross validation of dataset, F1-measure of chunk boundary identification is 95.05%, and the precision of chunk type recognition is 99.43% as well. And the total chunking F1-meausre reaches 93.58%. Comparing with other relative researches, the performance is improved and the training time of learners is sharply shortened.
To meet integrated security requirements in the security model of information systems, by extending the role-based access control model(RBAC) with security level, an open synthetical security model(OSSM) is proposed, and then, by extending some basic elements of OSSM according to its openness, a model of confidentiality and integrity as well as the model of Clark-Wilson are implemented. It is proved that OSSM will extend the application area of security model.
To improve the distance measurement accuracy between sensory nodes, the sources of errors in time difference of arrival (TDOA) distance measurement based on tiny micro threading operating system (TinyOS) were studied. A series of correction methods were put forward on average temperature of path compensation, timing factor compensation and bit synchronization compensation. Based on the least square method, a mathematic model was built to modify the results. Experiments show that the correction algorithm and the mathematical model can control the errors effectively and improve the precision in distance measurement.
The new words identification becomes an issue we have to face to with the generating flood of new words on Internet. Through analysis of the appearance characteristics of the new words, candidate strings were extracted according to co-current frequency and timeliness rules of the scattered single characters. Thereafter an improved algorithm of association rules was proposed for identifying the new words from the candidate strings based on the new word characteristics—adjacency, sequence, and frequency. Experiments show that the new words can be distinguished from the general single-character strings, the rigidity of the traditional n-gram model matching is lessened, and the short-word-included-in-long-word problem is solved, meanwhile, the precision of the new words identification is increased.
A new multipath routing algorithm called double backup multi-path routing, based on on-demand multipath routing for mobile Ad hoc networks (ODMR), is proposed, which preserves not only the routings from intermediate nodes to the destination, but the routings from the source to the intermediate nodes. It performs much better than ODMR, prolongs the lifetime of a routing, and reduces the frequency of request floods and time delay as shown by the simulation results.
A pilot aiming at mitigating the inter-cell interference of channel estimation in multi-input multi-output (MIMO) orthogonal frequency division multiplex (OFDM) systems is designed. The proposed pilot can make the power of interference distribute evenly over all the multi-path delays, so the inter-cell interference is similar to white noise. Based on characteristics of the proposed pilot, an improved frequency domain least squares (LS) channel estimation method is proposed. The algorithm is of low complexity, and is able to mitigate the inter-cell interference effectively even at existing of unknown multi-path delays, therefore, the performance of system will be improved significantly. Simulations validate the pilot design method and the channel estimation algorithm.
For improving the communication performance of simple object access protocol (SOAP) and adapting the needs of parallel computation in multi-cluster grid (MCG), a SOAP parallel communication model was proposed. By using of the concurrent data stream, the technique of dynamic buffer pool, the compression code and the pipeline parallel, the parallel run mechanism between communication device and the computation device were designed using memory function. The main components of this model, the model architecture, and the communication process were described. Analysis and experiment results show that this model has good communication efficiency and good characteristics for effective supporting parallel computation. It can be also fit for the parallel computation applications in MCG.
Based on the oscillation phenomenon in the decoding of Q-LDPC (q-ary low-density parity-check) codes, a modified decoding algorithm was proposed. In each iteration, for oscillating variable nodes, the previous posteriori probabilities are added to the current posteriori probabilities to reduce effects of oscillating in decoding. From the computer simulation, the modified decoding algorithm can achieve better bit error rate and block error rate for short and middle length Q-LDPC codes.
An admission control algorithm based on peer-to-peer for streaming media was proposed. For different peers had different in-bound bandwidth and out-bound bandwidth, the algorithm chooses the requesting the biggest contributed rate peer. When all peers’ in-bound bandwidths are the same, the system capacities that were gained by the algorithm and distributed DACp2p (differentiated admission contorl) protocol algorithm, respectively, would be the same. When all peers’ in-bound bandwidths were not the same, the system capacity that was gained by the algorithm would be bigger than that gained by the DACp2p algorithm.
An identification method for physical parameters of joint of robot is presented based on fuzzy automatic reasoning method. The method is a kind of on line adaptive fuzzy reasoning which is deduced based on fuzzy clustering method. The method can be used in parameters identification of time-varying system. Also a 3-DOF single arm robot is used as research object, and a dynamic model of the moving robot is built. The adaptive fuzzy reasoning method is used to identify the time-varying physical parameters of the robot joint. The computing error can be reduced because the local estimating method is applied. Experiment result shows that the method has better computing precision and identification speed, and has application value in practice engineering.
Aiming at a three-limb robot with integration of its arm and leg mechanism, regarding robot’s limb operating pattern as the special work process of its motion pattern, and translating kinematics analysis of the whole robot into the task of a kinematic combination of each limb acting as a standing or a swinging foot, the unification of kinematics model of the robot under circumstances of locomotion and operation is successfully realized. Working patterns of the three-limb robot in the state of both locomotion and operation are planned. A gait simulation of the three-limb robot is performed, it therefore justifies the previous theoretical analysis and lends a solid theoretical basis to the design of the robot controller in the future.
A single antenna interference cancellation (SAIC) receiver was proposed for suppressing the co-channel interference (CCI) of cellular mobile communications system in frequency selective fading channels. The receiver with parallel structure detects each co-channel signal with a soft-input soft-output (SISO) detector separately. The soft information provided by the detectors and the decoders is used as the a priori information for the iterative cancellation of CCI. Its complexity only grows linearly with the number of co-channel signals. Simulation shows that the performance of the proposed scheme converges to that of the optimal receiver.
With analysis and comparison of several chaotic systems generally applied on image encryption, the Henon map is proposed for image encrypting. Owing to the non-uniform distribution of sequence generated by Henon map, Wang Ying’s method is adopted, which lateralizes the decimal point to right direction and clips the integer part. The lateral parameter of Wang Ying’s method is limited in the treatment of chaotic sequence as to get a more suitable pseudo-random sequence in the progress of image encryption. Then a transfer matrix and a confusion matrix is used, which are generated by the pseudo-random sequence to exclusive or the bits of the pixels and scramble the location of image. Simulation results indicate that the algorithm can reach a better effect in image encryption and have strong anti-attacking performance.
In order to coordinate the inter-cell interference, a multicell adaptive power allocation scheme was proposed for downlink orthogonal frequency division multiple access (OFDMA) cellular systems. In order to coordinate transmit power in co-subchannels, the difference of signal to interference plus noise ratio(SINR) between co-subchannels of adjacent cells was used to balance SINR. Then the scheme would be able to improve the edge users’ performance, reduce the interference in co-subchannels of adjacent cells and improve the radio resource utility. Simulation results show that the scheme could balance the performance of the system and ensure the throughput of the system.
With the goal of minimizing the transmit power, an adaptive resource allocation algorithm is proposed for multiuser multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) downlink with correlated channels. Based on the users’ grouping according to their spatial correlations, the algorithm joints a shared manner and an exclusive manner. In different groups, the shared manner with a null steering method based on the group marginal users is applied. And in the same group, the exclusive manner is applied. The simulations show that the power and the spectral efficiency are improved; the base station antenna number and the computational complexity are decreased.
In order to improve the robustness of H.264 coded video over wireless channels, a new scheme using hybrid automatic repeat request (HARQ) technique for video transmission was proposed. To achieve the unequal error protection, the scheme adopted different HARQ schemes to different priority-data, that is based on data partition mode of H.264. The simulation results show that remarkable improvement in quality of the reconstructed video is obtained by using HARQ technique, especially in the low SNR regions. Moreover, the proposed scheme is with much more error robust compared with the equal error protection scheme under the same bandwidth.
A new signcryption scheme based on the BLS short signature and Gap Diffie-Hellman groups is proposed. It is proved that the new scheme is secure against adaptively chosen ciphertext attack in the random oracle model, and its security is reduced to computational Diffie-Hellman problem. The new scheme enjoys desirable properties as follows: signature unforgeability, public verifiability and forward secrecy. The computational costs and communication overheads of the new scheme are lower than those of signcryption schemes available, and the whole operation only requires two pairing evaluations, and the data rate of signcryption can amount to 28 percents. So the new scheme can be used in environments with stringent bandwidth constraints.
An initial quantity parameter (QP) prejudgment (IQPP) algorithm that can predict the initial QP precisely is proposed based on statistics of encoded frames and frame complexity eigenvalue of I frame. Experimental results show that IQPP algorithm will greatly enhance the performance of rate control and rate-distortion optimization (RDO). The average peak signal-to-noise ratio (PSNR) will be improved compared to traditional method and a constant picture quality has been achieved at low bit rates.
An optimized re-keying algorithm for secure multicast based on pseudo-random function (PRF) and exclusive OR (XOR) operation was presented. According to algorithm design concept, all updated keys with relativity were generated by PRF operation, and re-keying messages in multicast were generated by PRF and XOR operation together instead of conventional encryption and decryption. The communication cost, computation cost and storage cost are obviously decreased without destroy of the insurance of security. The simulation results of prototype under Linux verify that the optimized algorithm improves key management performance to some extent in secure multicast.
A novel image blind digital watermark algorithm is proposed. When using error correcting coding and Arnold transform, the binary image watermark is processed before embedded into the bitplane of the original gray image. It is effective to improve the security of traditional least significant bits (LSB ) watermarking algorithm. The embed position is chosen by the secret key which is obtained during the course of the best scrambling degree calculation in Arnold transform. This algorithm can also realize blind extraction of digital image watermark. The experimental results show that the watermarks are invisible and robust against noise and commonly used image-processing methods such as Gaussian’s noise, Salt Pepper noise, joint photographic experts group (JPEG) compressing, and crop procession etc
Based on bilinear pairings and dynamic accumulators, a new ID-based linkable ring signature scheme (SLRS-BP) was presented. According to SLRS-BP, a fair e-cash protocol (EC-LR) with revocable anonymity was given. By virtue of constant-size signature of SLRS-BP and the spontaneity of ring signatures, the EC-LR will show good for the bank systems which have large numbers of dynamically changed users. In addition, EC-LR can avoid the member revocation problem of e-cash protocols based on group signatures.
ZHANG Da-long, YU Hong-yi, LI Qing, HU Han-ying
The three-handshake broadcast protocol (THBP) was introduced as a single channel synchronous MAC protocol for multi-hop wireless networks. In THBP, a receiver-based conflict detection mechanism as well as a three-handshake process of the control packets was designed to ensure the reliable transmission of broadcast services. By three handshakes of the control packets, it allows nodes to schedule a conflict-free broadcast channel. Within scheduling process, the collisions were detected and reported by the destination nodes. The study shows that the protocol can ensure higher transmission reliability of the broadcast packets with the lower overhead.
A fast and reliable technique with high performance for timing and frequency synchronization of multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system is proposed in multipath fading channel. The synchronization is achieved using shift-orthogonal chu sequence which is simultaneously transmitted from all transmit antennas in the same OFDM time instant. The analysis method gives out better detection properties in terms of higher correct timing detection probability and accurate fractional frequency synchronization. Furthermore, with the help of the proposed algorithm, the integral frequency offset in time domain can be obtained without FFT transform, that will reduce the computation complexity for the synchronization in MIMO-OFDM systems. The valid of the new algorithm is verified in AWGN channel and multipath fading channel in which the first path is not the strongest one.
The real-time transcoding from MPEG-2 to MPEG-4, the discrete cosine transform (DCT) domain data of intra frame(I-frame) decoded in part by MPEG-2 decoder could not be directly used in re-quantization of MPEG-4. A quick compensation method based on DCT domain is proposed, in which the calculation time of six DCTs and six inverse DCTs are saved in each macroblock for implementing DCT and inverse DCT are not needed. Experimental results show that the transcoding time for I frame is saved by 65.05% and the peak signal-to-noise ratio (PSNR) error is in 0.001dB compared with the pixel domain compensation method.
A service framework in Military Information Grid (MIG) is proposed to integrate various battlefield information and the coordinated combat network is built. The framework can locate the required data in hundreds of geographically distributed sites. Vertically, it is composed of resources layer, grid-based service layer, metadata service layer, application service layer, and also user management layer. Meanwhile, the application service layer is horizontally partitioned into data service layer, information service layer, and knowledge service layer depending on to types of different service contents. The crucial functionality of metadata in the framework is demonstrated, and several related key techniques in the implementation are discussed. The framework is verified by the simulation in similar telecom scenarios based on service-oriented architecture. And it could be a feasible reference to meet the information sharing requirements of MIG.
A transmit diversity strategy in enhanced multimedia broadcast/multicast service (E-MBMS) networks was proposed, in which the space-time-frequency coding technique was adopted, i.e., the frequency diversity and the cyclic delay diversity were jointly designed to enhance the traditional space-time coding scheme. The broadcast/multicast cells in the proposal were divided into multiple cell groups. And the orthogonal frequency division multiplexing (OFDM) symbols in the same cell between different frames were executed with space-time coding schemes, Meanwhile, the proper cyclic delay was obtained to the frequency diversity gain in the different cell groups. Simulation results show that the proposal can improve the bit error rate performances efficiently and get increasing of coverage and throughput, especially for those users who are at the cell edges.
A dynamic generalized threshold multi-secret sharing scheme among weighted participants of special access right based on Chinese Remainder Theorem is introduced, it permits that multiple secrets be shared in one secret sharing session. The sub-secret of every participant can be used many times，and the secrets can be renewed without renewing the sub-secrets of the participants, furthermore, a participant can be freely put into or removed.
An amplify-and-forward (AF) based two-hop orthogonal frequency division multiplexing (OFDM) relaying system was analyzed. Since channel fading of the first hop and second hop is independent, system performance is limited if the signal is transmitted on the same sub-carrier in both hops. In order to solve the problem, a sub-carrier coupling method was proposed. A Hungarian algorithm was adopted to provide the optimal coupling scheme, and furthermore, sub-carrier coupling scheme based on sub-bands was presented. Simulations indicate that sub-carrier coupling can bring about 5 dB gain to the system. Though the gain of sub-carrier coupling scheme based on sub-bands only has a little loss, it can reduce signaling overhead greatly.