342 results about "Belief propagation" patented technology

A low density parity check (LDPC) code that is particularly well adapted for hardware implementation of a belief propagation decoder circuit is disclose& The LDPC code is arranged as a macro matrix (H) whose rows and columns represent block columns and block rows of a corresponding parity check matrix (Hpc). Each non-zero entry corresponds to a permutation matrix, such as a cyclically shifted identity matrix, with the shift corresponding to the position of the permutation matrix entry in the macro matrix. The block columns of the macro matrix are grouped, so that only one column in the macro matrix group contributes to the parity check sum in any given row. The decoder circuitry includes a parity check value estimate memory which may be arranged in banks that can be logically connected in various data widths and depths. A parallel adder generates extrinsic estimates that are applied to parity check update circuitry for generating new parity check value estimates. These parity check value estimates are stored back into the memory, and are forwarded to bit update circuits for updating of probability values for the input nodes. Variations including parallelism, time-sequencing of ultrawide parity check rows, and pairing of circuitry to handle ultrawide code rows, are also disclosed.

A decoder for performing soft decision iterative decoding of a cyclic code based on belief propagation, includes an information exchange control unit, an X processor, and a Z processor. The information exchange control unit takes pix-metrics that were calculated by the X processor for nonzero elements in each of n-cyclic shifts of the parity-check polynomial of the code, and distributes the pix-metrics to the Z processor as the piz-metrics for a corresponding check node. The information exchange control unit takes lambdaz-metrics that were calculated by the Z processor for nonzero elements in each of n-cyclic shifts in a reverse order of the parity-check polynomial, and distributes them to the X processor as lambdax-metrics for the corresponding code node. The operation of the information exchange control unit can be represented by the Tanner graph associated with an extended parity-check matrix, which is produced by adding k rows to the parity-check matrix of the cyclic code.

Disclosed is an apparatus having a detector for an iterative LDPC-coded MIMO-OFDM system, where the detector is configured to use a structured irregular LDPC code in conjunction with a belief propagation algorithm. Also disclosed is an apparatus having a detector for a structured irregular LDPC-coded MIMO-OFDM system, where the detector is configured to use an iterative Recursive Least Squares-based data detection and channel estimation technique. Corresponding methods and computer program products are also disclosed.

The present invention includes a technique for updating messages that originate at the constraint nodes of bi-partite graphs in Low Density Parity Check codes. The technique computes only two outgoing magnitudes at each constraint node and exhibits no measurable performance loss as compared to exact belief propagation which computes a unique magnitude for each departing edge from a given constraint node. The technique eliminates the need for memory based table look-up in the constraint node processing and has been implemented, in one embodiment, using only shift, add, and comparison operations.