- EI核心期刊
It is accepted that human sensors have the abilities of reflecting and recording the information only concerning the form and quantity of external stimuli, whereas the process of intelligent cognition and decision-making in brain should depend not only on the formal information but on the content and value information. A question is thus raised: where and how is the formal information conversed to content and value information? This is one of the kernel questions in intelligence science. An attempt is proposed here to apply the comprehensive information theory to explore the secret of the conversion, thereafter propose a preliminary hypothesis on the mechanism of the conversion that may be named as the theory of information content understanding.
Low density parity check codes are used to multiple access channels and the user-specific check matrices are used as the unique characteristics. A simplified algorithm is adopted to update the output message of multiple access channel factor nodes. Density evolution algorithm with Gaussian approximations is designed for the message propagation process of multi-user low density parity check codes. Based on the Gaussian approximation algorithm, the degree sequences for irregular low density parity check codes are optimized by using differential evolution algorithm. Analysis and simulation results show that the designed low density parity check codes have good performance on multiple access channel.
A three-dimensional localization algorithm is put forward for the sake of reducing location error and improving algorithm applicability. Combined with weighted filtration to successful sample points, it uses the method of sampling in three-dimensional space and range constraint to acquire three-dimensional coordinates of nodes. The algorithm can be executed in hop-based or range-based mode according to different node function. Three sampling schemes are adopted to analyze and compare the localization algorithm. Simulation results show this three-dimensional localization algorithm can respectively achieve location error under 25% and 35% of communication radius when anchor ratio is 20% and ranging error is 50% of communication radius.
For the weakness of low string matching speed in intrusion detection field, a fast improved algorithm to perform multiple pattern matching in a string was presented. In general, the algorithm described does not need to test each character in the string. By making full use of the results of matching successes and failures, the algorithm can often bypass inspection of as many characters as possible and get all matching locations after one quick search.Secondly,the new algorithm can match Chinese string due to using a combinatorial state automaton. Experimental results demonstrate that the proposed algorithm achieves excellent performance of detection and is helpful to reduce systematical missing package rate.
A parallel interference cancellation based mobile localization algorithm was proposed to mitigate the multiple access interference and to improve the location accuracy in mobile positioning systems. The proposed algorithm will mitigate the near-far effect and the multiple access interference of positioning signals from different base stations by iterative estimating and parallel interference cancellation. Simulation results show that the proposed algorithm will improve the accuracy of mobile localization.
A new channel estimation based on subspace in two multiple input multiple output （MIMO-OFDM） systems is discussed. The proposed method estimates noise subspace with reduced-rank orthogonal iteration for low computational complexity. The over-sampled autocorrelation matrix is transformed by colored noise whitening. A new method to estimate colored noise covariance matrix with training sequences is developed for improving the convergence rate of channel estimation. Simulation results illustrate that the proposed method can get good performance.
It’s well known that the spam-short-messages are annoying cell-phone users and mobile service providers everyday. A new spam-short-messages filtering system, combining online filtering with offline classifying, is presented. The system can filter messages efficiently according to the sending behavior characteristics and the messages contents. Additionally, a self-learning mechanism is designed based on its operators’ feedback. It enables the classifiers of the system to improve themselves according to the filtering results. Compared with traditional methods, the presented method has better performance in terms of filtering efficiency and accuracy.
Based on theories of simulated annealing(SA)、genetic algorithm(GA)、parthenon-genetic algorithm(PGA) and simulated annealing genetic algorithm(SAGA), the major merits and shortcomings of SA、GA and PGA are analyzed. According to the merits complementary nature of SA and PGA, a new algorithm --Parthenon-Genetic simulated annealing algorithm is proposed. The synthesizing of the merits of the two algorithms, reconstruction operation of gene in every generation in PGA has been improved. The traditional cooling method has been improved too. Between the operations of two generations, the algorithm adds a process which sorts the chromosomes in according to fitness function. In experiments we three groups city data’s traveling salesman problem (TSP) problems with the five algorithms mentioned above are used. It shows that the SAPGA’s average optimal solution is the least, and the convergence time is the shortest.
An extension technique from orthogonal frequency division multiplexing（OFDM） named overlapped frequency division multiplexing (OVFDM) is presented. Compared to the orthogonality between the carriers in OFDM system, OVFDM focus on the general frequency spacing of subcarriers. The method proposed not only improves the spectral efficiency of OFDM system but generates the coding constraint relationship. The detection algotirhm in the receiver is actually a frequency domain maximum likelihood sequence detection (MLSD) after using window function, and the complexity is limited moreover. Because OVFDM is not depend on the orthogonality among subcarriers but on the convolution constraint relationship among them, its spectral efficiency could be improved optionally. And the system’s spectrum and power are more effective because there exists no cyclic prefix. Analysis and simulation verify the validity of this theory.
With respect to information hiding system under passive attacks, a concrete statistical model of information hiding system was built and its performance was analyzed, including security, distortion distance metric, and channel capacity. The solution to channel capacity can be regarded, subjected to average hamming distortion distance and average security coefficient, as an optimization problem,. As long as the required parameters are given, the optimization problem of channel capacity will be easy be solved when using optimization theory. Finally, the channel capacity of statistical model is derived on the condition that both original cover sequence and secret information sequence obey to uniform distributions.
A mathematic model based on cyclic-server multi-queue (CSMQ) is proposed to analyze how the threshold puts influences on the system stability, the mean waiting time and the delay variance of dynamic bandwidth allocation algorithms without no head of line (HOL) blockings over Ether passive optical network （EPON). The proposed model consists of self-similar traffic model and two-buffer model. Simulation results verifies all the conclusions.
A district management strategy based on Chord model of peer to peer (P2P) network was proposed, in which nodes’ identities contain district location information to enhance the matching degree of the structured Hash algorithm between the logical overlay and underlying physical network. The strategy has realized P2P search from globe to region, especially in regions where the resources research become more often. Search efficiency has significant advantages than the traditional Chord model. The simulation results show that the district management strategy has remarkable advantages in average routing hops, delay and bandwidth.
The construction of symmetric correlation immune functions with n variables is equivalent to the solution in the binary field for a certain linear equation. When solving the equivalent equation of this linear equation, a part of solutions for this linear equation will be found out in six cases. Numbers of symmetric correlation immune functions with n variables are constructed in these cases. Four of the six constructions are found firstly.
A transitory classified keys management based on LKH (logical key hierarchy) was presented for clustered WSN (wireless sensor network). In the method, Diffie-Hullman keys agreement and LKH were used to distribute three types of keys which would be referred in the communications between nodes. The event-trigger based dynamic update strategy was launched to secure keys when network’s topology varies. The experiment shows that the key agreement efficiently reduces the communication and storage with slight calculation overload, and dynamic update strategy accommodates to the network topology changes and improves system’s security.
In a fully-loaded orthogonal frequency division multiplexing (OFDM) cellular environment with a frequency reuse factor equal to 1, any users moving at the cell boundary at a high speed will suffer both an inter-carrier interference caused by the time varying (TV) channels and an inter-cell interference. The scheme of pilot design in the downlink at the cell boundary is addressed, aiming at mitigating the two interferences mentioned above. The properties of the pilots are described, and the simulation results are presented.
To analyze the node throughput in wireless mesh networks (WMNs) based on IEEE 802.11 under fairness guarantee, an analysis model for multi-rate WMNs is proposed. The model calculates the data transmission time on the links with different data rate, and looks for the bottleneck collision domain (BCD) where the offered load was transmitted with the longest time. When the offered load in BCD is given, the value of largest node throughput can be achieved. The analysis value is according with the simulations results, and the model can analyze the node throughput in multi-rate WMNs accurately.
A novel particle filter is proposed to estimate the channel response and the frequency offset for uplink multiple input multiple output-orthogonal frequency division multiple access (MIMO-OFDMA) systems. First, the channel response and the frequency offset are described as auto-regressive (AR) model and generalized auto-regressive (GAR) model, respectively. Then the Rao-Blackwellization theory is evolved to reduce the complexity of particle filtering. The frequency offset can be estimated using the particle filter, and the channel response is updated using the Kalman filter. Simulation results show that the proposed scheme has lower block error rate than the regular particle filter, while the processing complexity increases a little.
A joint H.264 rate control and error resilience coding scheme is proposed to overcome constraints of low delay mobile video applications. The estimated transmission error sensitivity (ES) of the current frame and its contained macroblocks (MB) derived in pre-encoding stage are used to adaptively allocate target bits for frame and MB respectively. An importance level is set to each video slice based on the percentage of its contained high ES MBs, and an unequal error protection (UEP) with Turbo-codes is applied to slices based on their importance levels. Simulation shows that our scheme can obtain more than 1dB luminance PSNR gain on average compared with the conventional H.264 rate control and error resilience algorithms.
To solve the combination problem of conflict evidence in information fusion, a combination approach of conflict evidence based on proportional belief assignment criterion is presented. Firstly, the drawbacks of original Dempster’s rule of combination as well as several alternative combination approaches proposed so far are analyzed. Secondly, a new mass function based on proportional belief assignment criterion is combined. Finally, the results of numerical examples show that the new combination method can efficiently solve the Zadeh counterintuitive contradiction, the loss of majority opinion, robustness and the fairness of original and improved Dempster’s rules of combination.
According to the characteristic of real-time changes of available channels in cognitive radio network, a new comparability based adaptive clustering algorithm (CBAC) in application of graph theory is proposed. Based on the comparability of users’ available channels and the consideration of mobility of cognitive radio users, the algorithm optimizes the clustering result in cognitive radio network via computing the node’s weight. Experiments show that the CBAC algorithm increases the number of the link’s average available channels and has higher spectrum utilization rate and lower communication overhead than that of traditional clustering algorithms.
An improvement in the state transition model of intrusion tolerance system was proposed and a semi-Markov process (SMP) model is built. The steady-state probability of each state in the model is computed. In order to evaluate the security attributes quantitatively, the SMP model is used to study availability, integrity and confidentiality of intrusion tolerance system under four kinds of attacks. The numerical result is presented and analyzed. The results show that they are useful references to taking effective measures to tolerate the different attacks.
The dynamic characteristic of the space flexible manipulator driven by harmonic retarder fixed in joint was researched under hamilton’s canonical equations. Considering the flexible effect of the harmonic retarders, the style of dynamic constraint of the flexible beam during control was analyzed; then, the modal frequency and vibration shapes related to the control parameters and hamonic retarder’s rigidity parameter were obtained. Referering to both the joint and the beam flexibility, the dynamic equations coupled control parameters were built. The dynamic responses under different control parameters were simulated with examples, therefore, the validity of the system model was certificated.
To resolve the controllable of proxy signature, a restricted-times proxy signature scheme was suggested to control the proxies’ capabilities from quantity. The implement of the scheme was described. The controllability，the correctness, the security and the efficiency were analyzed.
Adaptive bit and power allocation is introduced in two hop orthogonal frequency division multiplexing – amplify and forward (OFDM-AF) relaying systems. The optimization problem for bit and power allocation in the systems is presented. Aiming at the problem, an adaptive bit and power allocation algorithm is proposed, it takes advantage of the idea of Greedy algorithm to maximize throughput subject to the constraint of reliable transmission requirement and transmit power. Simulations indicate that the algorithm will improve the system availability greatly with guaranteeing reliable transmission.
Distributed detection can increase the performance of the whole sensor network, however, it can not ensure to achieve optimum performance by only taking one specific fusion rule in any situations. The detection probability and false alarm probability of single node as well as the node number should also be considered for determining the fusion rule. An analysis fusion rule for distributed detection is introduced under the assumption that all the sensors are similar and operate at the same level of false alarm probability and detection probability. These properties and conditions can be used to increase the detection probability and to lower the false alarm probability. Finally a computation example is given for further justification.
The modulation diversity scheme of bit-interleaved space-time coded modulation was proposed. The method to achieve modulation diversity and the optimal rotated angle of the constellation to reach the maximum diversity gain were analyzed. The impact on the system of bit-interleaved space-time coded modulation with iterative decoding (BI-STCM-ID) was studied. The expression of pairwise error possibility (PEP) and bit metric for decoding were presented. Analysis and simulation results show that modulation diversity can greatly improve the performance of BI-STCM-ID under Rayleigh fading channels. Furthermore, modulation diversity combined with space-time diversity has the complementary effects on improving the performance of both fast and slow fading channels.
Based on researching the existing accounting schemes, a new compound charging scheme with considering both of the quality and content of the service was presented. The scheme can be applied in all kinds of services with different qualities and contents in order to charge them differentiated. The new scheme integrates some popular accounting schemes’ character, such as flat-rate, Usage-based, Priority and content-based accounting, and will meet varieties of demands of internet accounting, such as requirement of clarity, difference, availability, scalability and reasonability. Application in CNGI-QOSM system verifies the feasibility of this scheme.
Role-based access control (RBAC) introduced the concept of role to improve the assignment and management of privilege. RBAC is a secure, effective method of access control. The constraints model is an important one of the standard models of international committee for information technology standard (INCITS). After introducing the standard models of RBAC, the mechanism of static constraints is extended by introducing the static cardinality constraints and static privilege constraints. These constraints are formalized defined, and the system and administrative functional specification are extended to support the new constraints. The extended constraints will enhance the management of authority and the practicability, reliability of RBAC system.
To solve suboptimal routing problem caused by network mobility basic support protocol, a novel route optimization solution is proposed which makes difference between handover inside and outside local mobility domain, modifies localized mobility management framework, extends prefix information option in router advertisement message and adopts corresponding address delegation and movement detection strategies. This solution can provide optimized routing, reduce signaling and latency and shorten tunnel length as well, especially when mobile network moves frequently.
Methods of wavelet transform are effective methods of time-frequency analysis under the background of strong noise. A method to estimate the frequency of multi-carrier M-ary Phase-Shift Keying (MC-PSK) signals is showed, it uses Haar’s wavelet transform. Simulation is used. The algorithm is compared to modified carmer-rao bound(MCRB), it shows that the methods of wavelet transform can accurately estimate the carrier frequency of MC-PSK signals without prior knowledge. The estimation performance is effected by phase noise very slightly．