51 results about "Density evolution" patented technology

The invention discloses a density evolution based polarization code constructing method and polarization code coding and decoding system. According to the invention, the code length N and the information bit length K of an information code to be processed are obtained, an expectation value set of a log-likelihood ratio probability density function of N bit channels, K bit channels are selected as the information bit channels according to the expectation value set and information bit information index vector quantity is generated; an information bit sequence and a fixed bit sequence are mixed and the mixed bit vector quantity is multiplied by a polarization code for generating a matrix so as to output an encoding sequence; the encoding sequence is modulated and input into a transmission channel and the sequence output by the transmission channel is subjected to decoding operation by adopting a polarization code decoding algorithm, bit error probability and frame error rate of the decoded code are calculated and a design signal to noise ratio is changed, the above operation is repeated until the bit error probability and frame error rate become the minimum. The method and system provided by the invention are suitable for general binary system memoryless channels, the bit error probability and frame error rate are low, the calculation complexity is low and the communication performance of a communication system is improved.

Embodiments of the invention provide a method and device for determining channel reliability in polarization coding modulation. The method comprises: dividing a channel into m binary input channels, carrying out channel polarization transformation, and using a Gaussian approximation algorithm to calculate a log likelihood ratio Gaussian distribution mean corresponding to the polarization sub-channels according to the equivalent noise variance of the binary input channels obtained by splitting, so as to determine the reliability of the polarization sub-channels. Since the method provided by the invention adopts the Gaussian approximation algorithm, the problem of calculation complexity caused by calculating the channel reliability by using a density evolution tool is avoided. Compared with the scheme of calculating the channel reliability by using the density evolution tool, the calculation complexity of the method provided by the invention is obviously reduced.

The invention relates to the technical filed of the error correction and coding of communication and information systems and discloses a method for generating a quasi-cyclic low density parity check code. The method comprises the following steps: according to the requirements on code rate and code length of the low density parity check code to be designed and system requirements, determining a degree distribution sequence which is selected by adopting a density evolution method; setting the column weight of each column of a basic matrix according to the selected degree distribution sequence; setting the positions and values of non-zero elements in each column in the basic matrix according to the column weights of the basic matrix to obtain the basic matrix; and expanding the obtained basic matrix into a check matrix. At the same time, the invention also discloses a method for coding the quasi-cyclic low density parity check code and provides corresponding devices. The methods and the devices provided by the embodiment of the invention enable finally obtained code words to effectively reduce influences of cycle overlapping.

A method involves receiving an LDPC coded bitstream and demultiplexing the received LDPC coded bitstream using an optimized demultiplexer, the optimized demultiplexer being designed by:substituting Q levels of a constellation mapper by Q parallel binary erasure channels;optimizing a density evolution of erasure probability over said binary erasure channels for a plurality of demultiplexer offsets; andidentifying from the plurality of demultiplexer offsets those with a minimum number of check node decoder collisions.

A method and apparatus are described for constructing efficient Slepian-Wolf codes for inputs that do not have uniform probability distributions, and for channels which are not symmetric. Whereas conventional Wyner-Ziv video compression systems assume symmetrical probability distributions and ignore the marginal distribution component, the invention incorporates the marginal distribution component by combining the marginal distribution and conditional distributions as input to a transform that generates a symmetrical output, which is then fed into the conventional density evolution method.

A method of generating structured irregular LDPC codes for a wireless network such as a wireless local area network (WLAN) system, allowing systematic generation of improved code ensembles using density evolution, and providing essentially the best tradeoff between decoding threshold and decoding complexity. Such an LDPC code has a higher diversity order for MIMO systems, with better built-in interleaving capability. Further, the code dimension can be tailored to 802.11n system parameters such as the number of sub-carriers and delay. The code also provides an improved girth control scheme, provides flexible length with different expanding factors, and supports simple encoding and shortening for multiple rates.

A method of generating structured irregular LDPC codes for a wireless network such as a wireless local area network (WLAN) system, allowing systematic generation of improved code ensembles using density evolution, and providing essentially the best tradeoff between decoding threshold and decoding complexity. Such an LDPC code has a higher diversity order for MIMO systems, with better built-in interleaving capability. Further, the code dimension can be tailored to 802.11n system parameters such as the number of sub-carriers and delay. The code also provides an improved girth control scheme, provides flexible length with different expanding factors, and supports simple encoding and shortening for multiple rates.

Algebraic method to construct LDPC (Low Density Parity Check) codes with parity check matrix having CSI (Cyclic Shifted Identity) sub-matrices. A novel approach is presented by which identity sub-matrices undergo cyclic shifting, thereby generating CSI sub-matrices that are arranged forming a parity check matrix of an LDPC code. The parity check matrix of the LDPC code may correspond to a regular LDPC code, or the parity check matrix of the LDPC code may undergo further modification to transform it to that of an irregular LDPC code. The parity check matrix of the LDPC code may be partitioned into 2 sub-matrices such that one of these 2 sub-matrices is transformed to be a block dual diagonal matrix; the other of these 2 sub-matrices may be modified using a variety of means, including the density evolution approach, to ensure the desired bit and check degrees of the irregular LDPC code.

According to a quasi-cyclic low density parity check code basis matrix construction method, node distribution acquired through optimization of a density evolution algorithm is used, then a stretch factor Z is set, the circle length of the LDPC code check matrix and external message scale of the circle are jointed optimized, finally, a QC-LDPC code basis matrix with excellent performances is generated through extension. Each element in the basis matrix is corresponding to one Z*Z dimensional all-zero matrix, a unit matrix or a cyclic shift matrix of the unit matrix. But in construction of high code rate QC-LDPC code, the contradiction of limitation of matrix row number and maximum line number usually occurs, namely, the maximum line number is greater than the row number. To solve the problem, the invention provides construction of the basis matrix through a method increasing line number through superposition of a plurality of cyclic shift matrixes, namely, multiple cyclic shift matrixes are embedded in a single block matrix. The "superposition" operation is binary addition, the constructed basis matrix not only guarantees the cycle performance of the QC-LDPC code, but also meets the requirement of optimization of codon performance through increase of minimum code distance.

Disclosed is a density evolution algorithm based on a refined definition of node and edge densities for different parts of the code. In particular, density functions ƒV(1)(i) and ƒV(2)(i) of the output edges of the variable nodes with degree i within different codeword regions w1 and we, respectively, are defined and then calculated. Further, density functions ƒC(1)(j) and ƒC(2)(j) of the output edges for check nodes with degree j within codeword regions w1 and we, respectively, are defined and then calculated. Mixture density functions of output check edges connecting variable nodes in the first codeword region and the second codeword region are then calculated to determine an LDPC code design.

The invention discloses a coding method of code-rate-variable low-density parity-check codes (LDPCs) of which the performance approximates to the channel capacity, and mainly solves the problem of difficulty in performance optimization of the prior concatenated Zigzag codes, which is caused by limitation on space optimization. The coding method is realized through the following steps: firstly, a parameter Gamma of a precoder is optimized; subsequently, an information bit group is divided into two subgroups, wherein one subgroup is coded via an accumulator, and a coding result is combined with the other subgroup to serve as output of the precoder; afterwards, the output of the precoder is sent into concatenated Zigzag code coders to be coded, and check bit groups are obtained; and finally, the information bit group is combined with the check bit groups to form code words. The LDPC codes obtained through the method are named as pre-coding concatenated Zigzag codes, and the pre-coding concatenated Zigzag codes can conveniently realize performance optimization and support various code rates. A density evolution computational method and a computer simulation result show that decoding thresholds of the pre-coding concatenated Zigzag codes approximate to a Shannon limit, and the pre-coding concatenated Zigzag codes have excellent performance at different code rates and different lengths.

The invention relates to a method for evaluating the anti-seismic property of a building. The method comprises the following steps: (1) establishing a random seismic motion input model meeting the requirement according to the site condition, generating seismic waves under the seismic category setting condition, and selecting three actually recorded seismic waves and a manually simulated seismic wave to be inputted; (2) performing the seismic response analysis of a deterministic structure through a finite element model, and obtaining the displacement response among structure layers and the axial force response of an isolation bearing in the X direction and the Y direction under the seismic motion input action by using a probability density evolution equation when the seismic category of the structure is set; (3) on the basis of the random seismic response analysis of a seismic isolation structure, calculating the extreme values of response indexes, finally, giving out the degree of reliability of related indexes, and evaluating whether the degree of reliability meets the anti-seismic requirement or not. The seismic response condition of a multiple-degree-of-freedom system can be objectively and comprehensively evaluated on the basis of a probability density evolution method, and the anti-seismic property of the building is reliably and accurately evaluated.

A method involves receiving an LDPC coded bitstream and demultiplexing the received LDPC coded bitstream using an optimized demultiplexer, the optimized demultiplexer being designed by:substituting Q levels of a constellation mapper by Q parallel binary erasure channels;optimizing a density evolution of erasure probability over said binary erasure channels for a plurality of demultiplexer offsets; andidentifying from the plurality of demultiplexer offsets those with a minimum number of check node decoder collisions.

The invention discloses a method for optimally controlling magnetorheological damping of a random seismic excitation system. In the method, the active optimal control design is carried out by adopting a physical random optimal control strategy with the two-step optimizing character according to a control system with a random seismic excitation structure; the active optimal control grain design iscarried out by adopting a second order statistic evaluation criterion of the system to obtain an optimal control law parameter and thus the target active optimal control force for the design of a magnetorheological damping optimal control system is determined; and by adopting the target active optimal control force realized by tracking as a control criterion, the magnetorheological damping optimal control design is carried out by adopting a delimitation Hrovat semi-active random control strategy. In the invention, on the basis of a probability density evolution theory frame, the hedge of describing the classical random optimal control of a power system by using an Ito random differential equation is broken through; and the method opens up a new path for the active random optimal control.

A method for analyzing the basic data of a Chinese herbal compound based on PK-PD (Pharmacokinetics-Pharmacodynamics) comprises the following steps: 1) conducting steady transformation on original PK and PD data obtained by experiments; 2) drawing a virtual observation sample at random based on the empirical distribution function of the PK or PD data of each time point by a re-sampling method based on the overall observation numerical value of the sample, forming a virtual sample orbit through the virtual observation of multiple time points, and simulating the PK or PD measurement process; 3) calculating the accumulative effect of each time point, respectively calculating the relationships between selected PK indexes and PD indexes, and analyzing differences among different groups; 4), calculating the variation rates of the PD indexes of each virtual sample orbit about each herbal ingredient at each time point, and obtaining the action effect of the PK indexes on the PD indexes through the density evolution process of the variation rates. The relationships between the ingredients and the PD indexes are found through the quantitative analysis of the variation relationships between the PK data and the PD data.

A method for compensating pattern placement errors during writing a pattern on a target in a charged-particle multi-beam exposure apparatus including a layout generated by exposing a plurality of beam field frames using a beam of electrically charged particles, wherein each beam field frame has a respective local pattern density, corresponding to exposure doses imparted to the target when exposing the respective beam field frames. During writing the beam field frames, the positions deviate from respective nominal positions because of build-up effects within said exposure apparatus, depending on the local pattern density evolution during writing the beam field frames. To compensate, a displacement behavior model is employed to predict displacements; a local pattern density evolution is determined, displacements of the beam field frames are predicted based on the local pattern density evolution and the displacement behavior model, and the beam field frames are repositioned accordingly based on the predicted values.

The invention discloses a seismic reliability design method for a building seismic support hanger. The seismic reliability design method is characterized by including: establishing a building-structure three-dimensional spatial analysis model of a to be installed seismic support hanger; generating N seismic-wave acceleration-time curves with probability; calculating floor response spectra at the center of the floor plan of the building structure under input of seismic waves; calculating extreme probability density function curves of floor plan response spectrum values on self-seismic periodicpoints; calculating the extreme probability density function curves of axial stress of an inclined strut of the seismic support hanger to acquire the reliability that the inclined strut of the seismicsupport hanger does not have seismic damage. The probability density evolution theory is combined with the floor response spectroscopy to perform the seismic design for the building seismic support hanger in terms of reliability, and seismic performance of the seismic support hanger is evaluated reliably and accurately.

The invention discloses a double-layer lengthened LDPC (Low Density Parity Check) code-based relay transmission method, which mainly solves the problems of local optimization of a double-layer lengthened LDPC code and high complexity existing in the prior art. The method is implemented through the following steps: (1) broadcasting a message by a source node; (2) decoding by a relay node; (3) coding by the relay node; (4) modulating by the relay node; (5) forwarding by the relay node; (6) decoding by a destination node. According to the method, an integral optimization method is adopted during design of the double-layer lengthened low-density parity check code, and the transmission rates in two links of a full duplex relay channel can be kept maximum simultaneously; a double-layer gaussian approximate density evolution algorithm is adopted during optimization of the double-layer lengthened low-density parity check code, so that the method has the advantage of low decoding complexity and is suitable for an actual wireless communication system.

The invention discloses a reliability analysis method for a hybrid uncertainty structure. The method comprises the steps: firstly, respectively adopting a random variable and an interval variable to represent a random uncertainty parameter and a cognitive uncertainty parameter; generating a probability representative point and an attached probability according to a probability density function ofthe random variable; for each probability representative point, calculating upper and lower bound values of a structure performance function in an interval variable distribution interval; finally, according to the PDEM, numerically solving a generalized probability density evolution equation, and acquiring a structural reliability distribution interval. According to the method, the defects of poorprecision, low calculation efficiency and narrow application range of a traditional reliability analysis method under the hybrid uncertainty are overcome, the method better conforms to engineering practice, and a foundation is laid for reliability-based hybrid uncertainty structural design and optimization.

The invention discloses a wing structure stochastic-feature value analysis method based on probability density evolution, and belongs to the field of structure design. Uncertainty factors existing ina large complex structure are fully considered, and a stochastic method is utilized to quantitatively characterize uncertain parameters under a condition that sample information is sufficient. A finite-element equation of structure free-vibration is established, feature value analysis is transformed into a generalized feature value problem through modal coordinates, and feature value sensitivity is derived. A feature value probability density evolution equation is established on the basis thereof, and the feature value sensitivity is introduced into the equation to obtain a feature value probability density evolution equation based on sensitivity analysis. The feature value probability density evolution equation is reduced to a standard form through introducing new variables, and a finite-difference method and a total-variation-difference reduction format are employed to obtain a feature value probability density function by solving. Numerical results show that the feature value probability density function obtained by the method of the invention is in better agreement with a Monte Carlo method, and calculation time can be greatly reduced.

The invention discloses a diamond wire breaking detection device and a wire breaking prediction method thereof. The diamond wire breaking detection device comprises a capacitive sensor group, a preprocessing circuit, an A / D converter and a computer, wherein the capacitive sensor group carries out real-time monitoring and detection on the diamond wire; the diamond wires of different abrasion degrees enable the capacitive sensor group to output corresponding capacitance value signals of different sizes; the capacitance value signals are filtered and amplified through the preprocessing circuit, and the signals have fidelity and can be amplified to intensity which can be identified; the processed signals are transmitted to the computer through the A / D converter; and the computer carries out statistical analysis through the obtained capacitance value signals to represent the state of the diamond wire. The wire breaking prediction method specifically comprises the following steps that: the capacitive sensor group monitors the abrasion situation of the diamond wire in real time, the capacitance value signal which contains the abrasion situation of the diamond wire is output, after the capacitance value signal is calculated and analyzed through the computer, the probability density evolution law curve of the tested diamond wire can be obtained, and diamond wire breaking prediction canbe realized according to the probability density evolution law curve.

The invention relates to the technical field of mobile communication, in particular to an LDPC decoding method for improving minimum offset sum based on density evolution. The method comprises the following steps of calculating a channel message value received by a variable node; updating a check node and the variable node, and updating the external information transmitted between the check node and the variable node by using an optimal offset factor value; calculating a hard decision value of the variable node, and performing hard decision; and judging whether the hard decision meets a checkmatrix, and if so, outputting the hard decision as a decoding result. According to the method, the LLR message values before and after variable node updating are used for weighting in the number domain, so that the oscillation of the LLR information of the variable node during the decoding process is relieved, and the decoding convergence speed is increased; a density evolution method and the weighted average are adopted to calculate the offset factors under each signal-to-noise ratio, the linear approximation processing is combined to obtain the optimal offset factor, and the optimal offset factor is used as a constant to be stored in hardware, so that the redundant hardware calculation consumption is not increased during the implementation process.

The invention discloses a transmission precision reliability analysis method for an industrial robot speed reducer with a crack gear. The method comprises the steps of analyzing firstly, uncertainty factors of the industrial robot speed reducer; secondly, analyzing the meshing rigidity of the gear with the cracks by using a finite element simulation method, further solving a kinetic equation, andcalculating a transmission error of the gear with the cracks; then calculating a probability density function of the output error of the industrial robot speed reducer by applying a probability density evolution theory and a Dirac function; and finally, calculating the transmission precision reliability of the industrial robot speed reducer with the crack gear by using a Monte Carlo simulation method. According to the method, probability density evolution and a Dickelas function are applied to reliability evaluation of mechanical parts, and multi-degree-of-freedom linear and nonlinear mechanical structure dynamic performance response depiction and reliability calculation under uncertainty factor input can be described in a high-precision and high-efficiency mode.

The invention discloses a wallboard aeroelasticity stability analysis method considering hybrid uncertainty, and belongs to the field of aeroelasticity design of wallboards, and aims to quantitativelycharacterize uncertain mixing parameters by using a random model and an interval model in allusion to an uncertain mixing environment where random variables and interval variables coexist so as to establish an aeroelasticity stability analysis model for the wallboard containing the uncertain mixing parameters. On the basis, a probability density evolution method and an interval uncertainty propagation analysis method are combined, and a random-interval uncertainty propagation analysis method is provided. According to the interval mixing probability density evolution method, the probability statistical characteristics of the wall plate aeroelasticity response interval boundary can be estimated when the parameter fluctuation is large, the limitation of a traditional method on calculation efficiency and applicability is overcome, and the research blank of wall plate aeroelasticity stability analysis under the mixed uncertain environment is filled.

The invention discloses an efficient calculation method of probability failure risk assessment based on probability density evolution theory, belonging to the field of risk assessment. Aiming at the rotor disk of aero-engine, the density evolution equation of failure probability is established when probability failure risk assessment is carried out. By using the mapping relation between probability distributions in the density evolution equation of failure probability, the mapping omega 0 of failure domain at the initial time is obtained. Based on the detection probability of nondestructive testing, the detection region is defined in the failure region with corresponding proportion. Then, the mapping omega 0 of the detection domain at the initial time is obtained by using the mapping relation established by the density evolution equation of the failure probability. By integrating the joint probability density function in the failure domain and the detection domain, the failure probability of the roulette disc under the number of cycles N is obtained. The invention guarantees the requirement of the calculation precision of the failure risk assessment, and effectively improves the calculation efficiency of the failure probability.

The invention discloses an LT code encoding and decoding method and system. According to the method, a traditional Gaussian approximation tracking mean value method is modified into a mode of trackinga check node and outputting an error rate by a variable node, an obtained error rate result is closer to actual code word performance compared with a traditional Gaussian approximation (tracking meanvalue) method, and the coding and decoding precision is improved; the bit error rate result obtained by adopting the method is basically consistent with the discrete density evolution result, but thecomplexity is greatly reduced, and compared with a Monte Carlo simulation method, the method is shorter in time consumption, and the coding and decoding efficiency is improved. In addition, by meansof the method, the target bit error rate can be directly set during degree distribution optimization, it is guaranteed that a result obtained through optimization (namely code words with the optimizeddegree distribution) meets the target bit error rate under the condition that the code rate is as large as possible (namely code word cost is low), and therefore the degree distribution function optimized through the method has good bit error rate performance.

The invention relates to a reliability analysis-based foundation seismic isolation structure system optimization method, which comprises the following steps of: 1) calculating random seismic responseof a foundation seismic isolation structure under a seismic action according to a probability density evolution theory; (2) converting a first-time reliability exceeding solving problem into a probability density function solving problem of an equivalent extremum variable by utilizing an equivalent extremum event criterion, and solving a corresponding probability density function by utilizing a probability density evolution theory so as to obtain the dynamic reliability of the whole structure; 3) determining key design parameters in the seismic isolation support restoring force model through variance sensitivity analysis; and 4) constructing a probability criterion taking the overall reliability of the basic seismic isolation structure system as a constraint and a target, and performing parameter optimization on the key design parameters by adopting a genetic algorithm so as to optimize the basic seismic isolation structure system. Compared with the prior art, the method has the advantages that the calculation result with higher precision can be obtained more conveniently and quickly, the calculation amount is reduced and the like.

The invention relates to an earthquake dynamic reliability analysis method for a slope support structure. The method comprises the following steps of generating a series of random earthquake dynamic acceleration time history based on a random earthquake dynamic model; establishing a finite element dynamic analysis model, and calculating to obtain a series of support structure seismic displacementtime history; establishing and solving a generalized probability density evolution equation of the slope supporting structure to obtain a numerical solution of a displacement probability density function of the supporting structure at each moment; and obtaining an earthquake dynamic reliability result according to the numerical solution of the support structure displacement probability density function at each moment. Compared with the prior art, a series of seismic oscillation acceleration time history is generated on the basis of the random seismic oscillation model to represent randomness of seismic oscillation, solving is carried out on the basis of finite element dynamic analysis, and seismic horizontal displacement of the slope supporting structure is adopted as an evaluation index of the anti-seismic property of the supporting structure; intensity and frequency non-stationary characteristics of an earthquake, an amplification effect of seismic oscillation and dynamic nonlinearity of rock-soil body parameters are considered.