摘要:
A system and a method for determining a quasi-cyclic (QC) low-density parity-check (LDPC) code, such that the QC LDPC code has no trapping sets are disclosed. A set of matrices representing a family of QC LDPC codes are acquired, wherein each QC LDPC code is a tail-biting spatially-coupled code of girth not less than eight, and wherein each column of each matrix in the set has a weight not less than four. Based on a trapping set pattern, a matrix from the set of matrices is selected such that the matrix represents the QC LDPC code with no trapping sets. The matrix can be stored into a memory.
摘要:
A method estimates parameters of 3-phase voltage signals to synchronize a power grid in a presence of a voltage unbalance by transforming the 3-phase voltage signals to αβ-reference signals using a Clarke transformation matrix, and estimating sinusoidal signals and corresponding quadrature signals of the αβ-reference signals using an extended Kalman filter, and determining a phase angle of a positive sequence based on a relationship of the phase angle to the estimated the sinusoidal signals.
摘要:
A method generates a combined-replica group-shuffled iterative decoder, comprising. First. an error-correcting code and an iterative decoder for an error-correcting code is received by the method. Multiple group-shuffled sub-decoders for the error-correcting code are constructed, based on the iterative decoder. Then, the multiple group-shuffled sub-decoders are combined into a combined-replica group-shuffled iterative decoder.
摘要:
A system and a method determine a quasi-cyclic (QC) low-density parity-check (LDPC) code corresponding to a protograph and having a predetermined girth. At least several elements of the connectivity matrix representing the protograph are duplicated along at least one line of duplication to produce an inflated connectivity matrix, wherein values of at least several elements in the connectivity matrix form a pattern indicated by the predetermined girth. A hierarchical quasi-cyclic (HQC) LDPC code corresponding to the inflated connectivity matrix is determined and at least several elements of a matrix representing the HQC LDPC code are removed, such that the matrix is squashed along the line of duplication to produce the QC LDPC code.
摘要:
A code to be decoded by message-passing is represented by a factor graph. The factor graph includes variable nodes indexed by i and constraint nodes indexed by a connected by edges for transferring messages mi→a outgoing from the variable nodes to the constraint nodes and messages ma→i incoming from the constraint nodes to the variable nodes. The messages mi→a are initialized based on beliefs bi of a received codeword. The messages ma→i are generated by overshooting the messages mi→a at the constraint nodes. The beliefs bi are updated at the variable nodes using the messages ma→i. The codeword is outputted if found, otherwise, the messages mi→a are updated using a correction for the overshooting.
摘要:
A system and a method for determining a quasi-cyclic (QC) low-density parity-check (LDPC) code, such that the QC LDPC code has no trapping sets are disclosed. A set of matrices representing a family of QC LDPC codes are acquired, wherein each QC LDPC code is a tail-biting spatially-coupled code of girth not less than eight, and wherein each column of each matrix in the set has a weight not less than four. Based on a trapping set pattern, a matrix from the set of matrices is selected such that the matrix represents the QC LDPC code with no trapping sets. The matrix can be stored into a memory.
摘要:
Biometric parameters acquired from human forces, voices, fingerprints, and irises are used for user authentication and access control. Because the biometric parameters are continuous and vary from one reading to the next, syndrome codes are applied to determine biometric syndrome vectors. The biometric syndrome vectors can be stored securely while tolerating an inherent variability of biometric data. The stored biometric syndrome vector is decoded during user authentication using biometric parameters acquired at that time. The syndrome codes can also be used to encrypt and decrypt data.
摘要:
A method represents a correlated set of images. The correlation can be spatial or temporal. A lossy operation is applied to each image in the correlated set to generate a coarse image. The coarse image is encoded losslessly to yield an encoded coarse image. Each image is also represented by syndrome bits. The combination of the encoded coarse images and the syndrome bits represent the correlated set of images.
摘要:
A method decodes a soft-input cost function for an [N,k]q linear block error- correcting code that has a fast sparse transform factor graph (FSTFG) representation, such as Reed-Solomon codes. First, the code is selected and its FSTFG representation is constructed. The representation is simplified and is made redundant if the improved performance is more important than the increased decoding complexity. An encoding method consistent with the representation is selected. A set of message-update and belief-update rules are selected. The messages are initialized according to a soft-input cost function. An iterative decoding cycle is then begun, in which the first step consists of updating the messages according to the pre-selected message-update rules. In the second step of the decoding cycle, a trial code word is determined from the messages, the pre- selected message-update rules, and the encoding method. In the third step of the decoding cycle, the tentative output code word of the decoding method is replaced with the trial code word if the trial code word has lower cost. Finally, the decoding cycle terminates if a termination condition is true, and outputs the tentative code word, and otherwise repeats the decoding cycle. The decoding method can be combined or concatenated with other decoding methods for FSTFG codes.
摘要:
A method decodes a received word for a binary linear block code based on a finite geometry. First, a parity check matrix representation of the code is defined. The received word is stored in a channel register. An active register represents a current state of the decoder. Each element in the active register can take three states, representing the two possible states of the corresponding bit in the word, and a third state representing uncertainty. Votes from parity checks to elements of the active register are determined from parity checks in the matrix, and the current state of the active register. A recommendation and strength of recommendation for each element in the active register is determined from the votes. The elements in the active register are then updated by comparing the recommendation and strength of recommendation with two thresholds, and the state of the corresponding bit in the received word. When termination conditions are satisfied, the decoder outputs the state of the active register. If the decoder outputs a state of the active register that does not correspond to a codeword, a new representation for the code using a parity check matrix with substantially more rows is chosen, and the decoding cycle is restarted.