- EI核心期刊
Based on the unrestricted aggregate signature scheme and the public-key cryptosystem based broadcast protocol, a new multi-party contract signing protocol (MCSP) was proposed. The MCSP employed the public-key cryptosystem based broadcast protocol (PCBP) to distribute the messages of the signers, and employed the unrestricted aggregate signature scheme to sign the contract between the signers. The implementation of MCSP is divided into two phases：The signers exchange the aggregate signature on the message and voucher in the first phase; then, they exchange their signatures on the contract. If a dispute occurs in the process of implementing, any signer can ask the adjudicator to settle the dispute to ensure fairness. The performance analysis results show that the proposed multi-party contract signing protocol satisfies the requirements of unforgeability, opacity, extractability and fairness. The proposed CSP has more efficient，and the interactions of message grow linearly with the increase of the parties.
Providing special correlated template, an improved ultra wide band (UWB) receiver based on parallel combinatory spread spectrum is presented. With help of these special templates, the UWB signals demodulation and despread of parallel combinatory spread spectrum signals can accomplished, and the infection coming from the error codes in demodulation of the UWB portion is reduced as well. Simulation shows that, under the background of the additive white Gaussian noise, the improved structure has a better biterror rate performance. And when the bit error rate is about 10-4, the signal to noise ratio of the improved structure needed is about 2dB lower than the former one.
The existing solutions of cooperative spectrum sensing (CSS) based on decision fusion are mostly built on the assumption of ideal decision transmission without considering any fading or noise corruption in common control channels. For this, the sensing channels and control channels are extend as Suzuki characteristics. A cooperation scheme is proposed under imperfect decision transmission model, in which a detector based on minimum error probability rule is used for decision estimation. The final decision combination is accomplished with K out of N rule. As demonstrated both by simulation, there is some performance deterioration in the proposed scheme, when compared with the ideal case that assumes errorfree decision transmission. It is even inferior to the local sensing when the average signal to noise ratio of the control channels is very low. Further, the spatial correlation of shadowing effects is investigated. It is shown that the negative impacts of correlated shadowing on the CSS gets weaker with the increasing distance between each other of the secondary users.
Considering the stochastic resonance phenomenon is constrained and influenced by signal amplitude and frequency, noise intensity and system parameters, a fast and effective adaptive adjusting method for stochastic resonance (SR) parameters is proposed. The adaptive adjustment of the sampling frequency and system parameters for the timevarying input signal and noise not only can effectively prevent data overflow in SR process, but also can maintain the best signal processing performance and keep the output signal to noise ratio at the maximum value. Simulation demonstrates the validity of proposed method.
To quantitatively study the mechanism of the guidance of Internet public opinion, a new design on the effect of the common guiding methods through graph centrality in social network analysis (SNA) is presented. Compared with the result of the common methods using the data of ‘Huananhu’ event occurred in Tianya forum in the Internet, an advice of guiding the Internet public opinion in all stages of its evolvement is proposed.
It is difficult for fuzzy Sarsa learning(FSL) to tune learning rate and balance exploration vs. exploitation, so an improved FSL(IFSL) method based on FSL is presented. In the method, an adaptive learning rate generator for tuning learning rate online and a fuzzy balancer for controlling the degree of exploration vs. exploitation are introduced. The diagram of IFSL is given, and the weight vector of IFSL with stationary action selection policy converges to a unique value is proved. Simulation results show that IFSL well manager balance, and outperforms FSL in terms of learning speed and action quality.
Its presented an indepth algorithmic study of the carry of ones complement addition. The results are based on a fairly simple classification of Fn2, we derive O((n－1)/2)time algorithm to calculate the probability distribution of XOR difference between ones complement addition and XOR. The results solves the probability distribution of noise function produced by macrocosm approximations of ones complement addition with XOR, and reflects the closeto degree of the two operations.
In order to realize the digital convergence business integration of operational management needs, we propose an architecture which uses the enhanced telecom operations map model structure of telemanagement forum and serviceoriented architecture for design core. The architecture fulfills the future digital convergence business oriented requirements to construct the completed operation support system(OSS), and analyze instructions architecture constitute modules and related subsystems. In addition, using web services interface the service network component interface and information transmission standardization are built. Therefore, this architecture can provide a framework of recommendation and reference for customer service order process flow description based on digital convergence networks service operation support system.
Fault correction by detecting anomalies designating performance degradation is an important approach to improving the reliability of communication network. Statistical hypotheses testing approach is employed to detect network anomaly. A new approach to acquiring the fluctuation threshold is proposed comprehensively when taking advantage of time series prediction confidence interval computation based on multiplicative autoregressive integrated moving average. Furthermore, under the assumption that the training residual which is a white noise process follows normal distribution, the associated confidence interval of prediction can be figured out under any given confidence degree by constructing random variable satisfying t distribution. Experiments verify the effectiveness of anomaly detection mechanism and the accuracy of the algorithm.
Aiming at the unresolved problem of estimating the minimum link scheduling time lower limit in wireless Mesh networks when taking multigateway accessary, a new calculation approach of its time lower limit is put forward .The method essentially involves a Pareto optimizing problem based on resource allocation. The Lagrangian algorithm,via Lyapunov function, is taken to solve the problem. The minimum link scheduling time lower limit based on optimized rate of multigateway accessing can be figured out. The foregoing method can not only calculate the lower limit of the minimum link scheduling time more accurately, which is used to evaluate the network performance, but also can reach the goal to optimize the upstream link scheduling rate in wireless mesh networks and to improve the link throughput.
A construction scheme of the changeable intruder model is proposed. By defining the concept of abstract terms and their operation rules. The changeable intruder model (CIM) can greatly reduce the complexity of algebraic operations for intruders. And the CIM defines the intruder action library and the attack rule selection algorithm, which enables the analysts construct a changeable intruder model according to different protocols. As the actions of the intruder are composable, the CIM is able to dynamically adjust the intruder models. Changeable intruder model ensures both efficiency and correctness of the protocol analysis for model checkers.
Aiming at solving the problem that access selection method based on fuzzy logic and neural network technology for heterogeneous wireless network did not consider network load conditions reasonably, a particle swarm optimization (PSO)fuzzy neuron based access selection algorithm with dynamic adaptability for network load is proposed. This method set equal access blocking rate as a goal for fuzzy neuron parameter learning, and combined with PSO algorithm with global optimization capability to set initial parameters value, so as to improve the precision of parameter learning. Simulations show that the proposed algorithm can balance the load among networks effectively, and reduce the access blocking rate compared with maximum load balance algorithm.
In order to reduce the waste of network resources caused by multiple copies routing in delay tolerant networks (DTN), a routing algorithm based on probability gradient and fresh gradient (PFG) is proposed. In the algorithm, the historical track of the destination node and the coverage potential field of the destination node are established with probability gradient and fresh gradient. When the two nodes meet, the message will be sent to the node which is much fresher and with higher probability to the destination node, it means that more waste of network resources can be avoided. Simulations show that the PFG can efficiently reduce data copies in network under the same message delivery rate and message average delivery delay, and hence improve the system performance.
A millimeterwaveband multichannel source generating method for wavelengthdivisionmultiplexed (WDM) radioonfiber (ROF) systems is proposed. Firstly, the combined use of a femtosecond semiconductor modelocked laser and two 5mlong high nonlinear photonic crystal fibers with opposite dispersion values is demonstrated experimentally to implement a supercontinuum with width of more than 170nm around 1550nm. Secondly, a sampled fiber Bragg grating is used to filter spectrum. It is shown that the spectrum is sliced into 20 channels with ±03dB peak fluctuation. Each two adjacent channels can be filtered out as one channel radiofrequency carrier. 10channel carriers are successfully obtained for WDMROF system. These tenchannel carriers have some advantages such as small gain fluctuation, large modulation depth and narrow width, etc.. Besides, the whole system can be easily integrated for its simple structure and small insertion loss.
Based on the established threat model in cognitive radio networks, the performance loss of conventional cooperative spectrum sensing scheme under malicious attacks is figured out. And a weighted cooperative spectrum sensing algorithm is proposed based on the cognitive radio’s (CRs’) reputation. The reputation values are updated according to the behavior history of CRs, the weighted factors are derived from reputation values, and the final result is made by weighted fusion as well. Simulations show that the new method outperforms the conventional cooperative spectrum sensing algorithms under threat environment.
In digital wireless communication systems, to reduce the complexity of channel decoding, the soft information always needs to be intercepted as fixpoint information before channel decoding. Upoverflow and downoverflow will be happened during the interception process, and then two kinds of system performance degradation will be occured. Based on joint consideration about these two kinds of overflow, a new adaptive fixpoint information interception method is suggested, so that the system performance will show better than those existed methods and even near to the exhaust algorithm, with high time efficiency. This method is verified by simulations, and then successfully applied to on a broadcast communication platform based on superposition coding.
A throughput efficiency oriented opportunistic routing algorithm for wireless Mesh networks is proposed. The relationship between the qualities and quantities of forwarding nodes is researched. The forwarding characteristics of multiforwarders are analysed. Consequently,a new routing metric and a corresponding forwarder selection algorithm is presented successively. With this method, we will achieve a better balance between the number of forwarders and link stability for introducing the factor of transmission time. Simulations show that the proposed algorithm can achieve higher endtoend throughput with fewer number of forwarding nodes and transmissions.
Currently limiting to the minimal support， the algorithms used in alarm association rules mining are almost applied in the frequently occurring alarm events. A new algorithm based on graph theory to mine telecommunication alarm pattern is proposed. It first mines networks 2items association pattern by scanning the database only once, and then gets the maximal association mode, so that it can avoid generating lots of middle items. Experiments based on the actual network alarm data demonstrate the efficiency and the effectiveness of the algorithm.
A new spacetime equalizer with wavelet transformation based on structure risk minimum criterion (WSRMSTE) is present to improve convergence speed by a wavelet transformation. In some dimensions wavelet signal space, it not only takes advantage of learning information in communication signals, but also appropriately exploits structure information of filters. It adaptively adjusts wavelet coefficients and capacity control coefficients. Simulation is carried out. It shows that, compared with a spacetime equalizer based on structure risk minimum criterion, and a typic spacetime equalizer with wavelet transformation based on support vector machine, the WSRMSTE is with better track performance and rapid convergence speed. So, it can be applied to wireless mobile communications.
To improve the resource location efficiency and guarantee resource download quality of peer to peer (P2P) system, a new concept of interest domain trust similarity as well as its computation method is given based on Interest domain partition mechanism using node Interest bias in P2P Networks. Thereupon, a P2P network topology construction model named interest domain trust similarity sensitive P2P topology (ITAPT) is implemented. In ITAPT, by computing interest domain trust similarity of each other, the nodes with similar interest and trust value are connected as neighbors. Thus the ITAPT will improve node resource query efficiency, and provide an incentive mechanism to encourage node to offer more contribution so as to get better service. Simulations show that the ITAPT improves the efficiency and security of P2P topology effectively.
To merge various mappings resulted from multiple ontology matchers, an argumentation framework is presented for ontology mapping negotiation. In this framework, arguments are built for mapping results while four argument relations such as support, disprove, unite and attack are used to reflect the impacts among mappings. By judging successful attack and computing preferred extension, the acceptable arguments, namely final mapping results, are obtained. Experiments show that the effect of mapping negotiation is improved, and a powerful tool for the cooperation of multiple ontology matchers is provided as well.
Autocorrelation properties of coordinate sequence generated by single cycle Tfunction (the kth coordinate sequence) are investigated to check whether Tfunctions can be the substitution of linear feedback shift register in the design of stream ciphers. Based on single cycle Tfunctions properties and autocorrelation functions periodicity, the bounds of autocorrelation functions are calculated, where the shift is equal to the period of the kth coordinate sequence multiplied by 2 to the minus power. According to the bounds, it is concluded that the smaller the shift is, the larger the value of autocorrelation functions is. As a result, Tfunctions are not suitable for generating pseudorandom sequences.
In order to detect the defects of widespread used business process execution language（BPEL） statically, the defects existed in BPEL programs are deeply studied. A defectoriented static testing method for BPEL is presented. The extended finite state machine is used to model the defect under detections. The states of defects can be identified by transition conditions of the properties state. And the redundancy of calculation by merging the conditions of identical property state at join points in the control flow graph is avoided. Experiments show the validity and feasibility of this method, it can be used to enhance the reliability and accuracy of process.
Delay tolerant network (DTN) routing protocol based on historical information forwarding, according to the history of statistics forecast estimates on the next hop node, forwarding and storage of information to judge the best time, and avoids blindly forwarding information. In this paper, the typical spray and focus protocol choice blindness among nodes, the "separation time" applied to routing, buffer management and multicast mode, the good conservation of resources and improves communication efficiency. Simulation results show that the improved protocols effectively improve delivery ratio and shorten the message delivery delay.
The continuous Markov model is used to model the access process of cognitive users with finite population. In connection with the variability of the number of primary users and cognitive users, the blocking probability, the forced termination probability and the average numbers in channels of cognitive users are analyzed while cognitive users try to occupy the licensed channels. Simulation results show that the blocking probability and the forced termination probability of cognitive users will climb up with the increase of the number of primary users or cognitive users while the average numbers of cognitive users in licensed channels will reduce with the increase of numbers of primary users and grow up with the increase of numbers of cognitive users separately.
A modified covariance differencing method is proposed to the direction of arrival (DOA) estimation of narrowband signals under a colored noise environment. The covariance matrix of received data is transformed in a linear way. The noise component is eliminated finally by assuming a symmetric Toeplitz matrix for the unknown array noise. The covariance differencing algorithm works well when impinging signals are uncorrelated or just two signals are coherent. The proposed approach combined with spatial smoothing technique is further investigated in the case that coherent signals are more than two. Analysis shows that new approach can avoid generating “phantom” angles while providing accurate DOA estimation. Therefore the proposed method operates at a lower computational complexity compared with conventional methods. Simulation results demonstrate the effectiveness of presented algorithm.
To improve the overall performance of the network, a transmission mechanism of probability based on the Markov model has been proposedfair bandwidth allocation scheme between uplink and downlink flows. There is no need to make changes to the distributed coordination function protocol of station. Only by adjusting the minimum contention window and transmission probability of access point, the fairness between uplink and downlink can be achieved. Detailed simulation results show that the scheme can achieve fairness between uplink and downlink flows with the total throughput increased.
A joint parameters estimation algorithm for orthogonal frequency division multiplexing (OFDM) signals was presented based on cyclic autocorrelation function(CAF). Joint estimation of the chip time, the symbol time and symbol useful time parameters of OFDM signals can be realized with the algorithm only by searching the distance between the peaks in the corresponding plane. And a method based on frequency domain accumulation for calculating the CAF of OFDM signals was adopted in low signal noise ratio. The validity of the algorithm was proved by simulations.