Herein provided are methods and systems for decoding polar codes. A data flow graph relating to a predetermined polar code is converted to a tree graph comprising rate-zero nodes, rate-1 nodes, and rate-R nodes. A rate-R node within the binary tree is replaced with a maximum likelihood node when predetermined conditions are met thereby replacing a sub-tree of the tree graph with a single maximum likelihood node.

An encoding method and encoder of a time-varying LDPC-CC with high error correction performance are provided. In an encoding method of performing low density parity check convolutional coding (LDPC-CC) of a time varying period of q using a parity check polynomial of a coding rate of (n1)/n (where n is an integer equal to or greater than 2), the time varying period of q is a prime number greater than 3, the method receiving an information sequence as input and encoding the information sequence using Equation 1 as a g-th (g=0, 1, . . . , q1) parity check polynomial to satisfy 0.

Syndrome calculation circuitry for a decoder of codewords having a first number of symbols, where the decoder receives a second number of parallel symbols, and where the first number is not evenly divisible by the second number, includes multipliers equal in number to the second number. Each multiplier multiplies a symbol by a coefficient based on a root of a field of the decoder. The multipliers are divided into a number of groups determined as a function of a modulus of the first number and the second number. Adders equal in number to the groups add outputs of multipliers in respective ones of the groups. Accumulation circuitry accumulates outputs of the adders. Output circuitry adds outputs of the adders to an output of the accumulation circuitry to provide a syndrome. Selection circuitry directs outputs of the adders to the accumulation circuitry or the output circuitry, and resets the accumulation circuitry.

A decoding method includes that when encoding at a sending terminal, for a m-order primitive polynomial P(x), a primitive field element in galois field GF(2.sup.m) is represented by ?; a lookup table f(?.sup.j) for different power exponents of ? is established, where the value of j is selected from all the integers ranging from 0 to 2m?1, with a total number of 2m; a generator polynomial G(x) is expanded to obtain a polynomial with respect to x, with coefficients being an addition or subtraction of the power exponents of ?; a remainder polynomial R(x), obtained by dividing code word polynomial Q(x) by the generator polynomial G(x), is a polynomial with respect to x, with coefficients being an addition or subtraction of the power exponents of ?; and the coefficients of the generator polynomial G(x) and the remainder polynomial R(x) are both calculated using data found in the lookup table f(?.sup.j).

A method of operation of a decoder includes receiving first data at the decoder. The method further includes generating second data at the decoder based on the first data. The second data is generated by adjusting an error locator polynomial based on an error parity of the first data.

Syndrome calculation circuitry for a decoder of codewords having a first number of symbols, where the decoder receives a second number of parallel symbols, and where the first number is not evenly divisible by the second number, includes multipliers equal in number to the second number. Each multiplier multiplies a symbol by a coefficient based on a root of a field of the decoder. The multipliers are divided into a number of groups determined as a function of a modulus of the first number and the second number. Adders equal in number to the groups add outputs of multipliers in respective ones of the groups. Accumulation circuitry accumulates outputs of the adders. Output circuitry adds outputs of the adders to an output of the accumulation circuitry to provide a syndrome. Selection circuitry directs outputs of the adders to the accumulation circuitry or the output circuity, and resets the accumulation circuitry.

A decoder configured to decode a representation of the codeword includes an error locator polynomial generator circuit. The error locator polynomial circuit is configured to generate an error locator polynomial based on a decode operation that includes iteratively adjusting values of a first polynomial, a second polynomial, a third polynomial, and a fourth polynomial. The error locator polynomial circuit is also configured to initialize the third polynomial based on even-indexed coefficients of a syndrome polynomial and initialize the fourth polynomial based on odd-indexed coefficients of the syndrome polynomial.

The inventive concepts relate to an operation method of an error correction decoder correcting an error of data read from a nonvolatile memory. The operation method may include receiving the data from the nonvolatile memory, performing a first error correction with respect to the received data in a simplified mode, and performing, when the first error correction fails in the simplified mode, a second error correction with respect to the received data in a full mode. When the first error correction of the simplified mode is performed, a part of operations of the second error correction of the full mode may be omitted.

Bits in a received word that is based on a codeword of a polar code are decoded to generate decoded bits. A lower-order partial sum is updated based on the decoded bits, and a higher-order partial sum based on the lower-order partial sum is computed. The higher-order partial sum computation is a live computation performed during decoding of a subsequent bit in the received word in some embodiments. In decoding the subsequent bit, nodes in a Data Dependency Graph (DDG) of the polar code may be traversed in a reverse order relative to node indices of at least some of the nodes in the DDG. A reverse order may also be applied to partial sum computations, to combine multiple lower-order partial sums that are based on previously decoded bits according to a reverse order relative to an order in which at least some of the previously decoded bits were decoded.

Provided is a CRC calculation circuit capable of dealing with various types of generator polynomials with a simple configuration. A CRC calculation circuit (100) includes a generator polynomial register (110) configured to store polynomial data, and a plurality of CRC calculation units (120) connected in series and provided so as to correspond to the number of bits of input data. The CRC calculation units (120) each include a barrel shifter (121) configured to shift calculated data by one bit using the input data or output data from a pre-stage CRC calculation unit as the calculated data; an XOR circuit (122) configured to perform XOR calculation of the shifted data and the polynomial data; and a multiplexer (123) configured to select, based on the calculated data, the shifted data or calculation result data.