Module ldpc 

CCSDS LDPC (AR4JA) codes (CCSDS 131.0-B-5). CCSDS LDPC (Low-Density Parity-Check) Forward Error Correction

Implements the AR4JA LDPC codes specified in CCSDS 131.0-B-5.

Supported TM Codes

Code	Rate	k	n	Circulant	M (block)
TM1280	4/5	1024	1280	32	128
TM1536	2/3	1024	1536	64	256
TM2048	1/2	1024	2048	128	512
TM5120	4/5	4096	5120	128	512
TM6144	2/3	4096	6144	256	1024
TM8192	1/2	4096	8192	512	2048

Encoding

Systematic encoding using compact generator matrices derived from the CCSDS AR4JA parity-check matrix. The generator exploits the circulant structure: one row per circulant block is stored, and the other rows are obtained by rotation.

Decoding

Layered min-sum belief propagation with fixed-point (i16) LLRs. The H matrix is expanded on-the-fly using the PI_K permutation function defined by theta/phi lookup tables per CCSDS 131.0-B-5.

Structs

LdpcCode

Describes a CCSDS AR4JA LDPC code.

LdpcFecDecoder

LDPC hard-decision decoder implementing FecDecoder.

LdpcFecEncoder

LDPC encoder implementing FecEncoder.

Enums

LdpcError

Errors from LDPC operations.

Statics

CODE_TM1280

TM1280: Rate 4/5, k=1024, n=1280.

CODE_TM1536

TM1536: Rate 2/3, k=1024, n=1536.

CODE_TM2048

TM2048: Rate 1/2, k=1024, n=2048.

CODE_TM5120

TM5120: Rate 4/5, k=4096, n=5120.

CODE_TM6144

TM6144: Rate 2/3, k=4096, n=6144.

CODE_TM8192

TM8192: Rate 1/2, k=4096, n=8192.

Functions

bytes_to_llr

Converts packed bytes to hard LLR values.

decode

Decodes using layered min-sum belief propagation.

decode_hard

Convenience decoder for hard-decision received data.

encode

Encodes information bits into a systematic LDPC codeword.

llr_to_bytes

Extracts hard decisions from LLR values into packed bytes.

syndrome_check

Checks if hard decisions satisfy all parity checks.