3.2.3. CRC parameters

The following parameters concern the Cyclic Redundancy Check (CRC) module. CRC bits can be concatenated to the information bits in order to help the decoding process to know if the decoded bit sequence is valid or not.

Note

The CRC is only available for some specific decoders that have been designed to take advantage of the CRC like in [Crc-LST12, Crc-TLLeGal+16].

Warning

Using a CRC does not guarantee to know if the decoded frame is the good one, it can be a false positive. It is important to adapt the size of the CRC with the frame size and the targeted FER.

3.2.3.1. --crc-type, --crc-poly

Type

text

Default

NO

Examples

--crc-type "32-GZIP"

--crc-poly "0x04C11DB7" --crc-size 32

Select the CRC type you want to use among the predefined (or not) polynomials.

Table 3.1 shows a list of the predefined polynomials. If you want a specific polynomial that it is not available in the table you can directly put the polynomial in hexadecimal. In this case you have to specify explicitly the size of the polynomial with the --crc-size parameter. The type NO deactivates the CRC.

Table 3.1 List of the predefined CRC polynomials.

Type	Polynomial	Size
32-GZIP	0x04C11DB7	32
32-CASTAGNOLI	0x1EDC6F41	32
32-AIXM	0x814141AB	32
32-KOOPMAN	0x32583499	32
30-CDMA	0x2030B9C7	30
24-LTEA	0x864CFB	24
24-RADIX-64	0x864CFB	24
24-FLEXRAY	0x5D6DCB	24
24-5GA	0x864CFB	24
24-5GB	0x800063	24
24-5GC	0xB2B117	24
21-CAN	0x102899	21
17-CAN	0x1685B	17
16-IBM	0x8005	16
16-CCITT	0x1021	16
16-PROFIBUS	0x1DCF	16
16-OPENSAFETY-B	0x755B	16
16-OPENSAFETY-A	0x5935	16
16-DNP	0x3D65	16
16-T10-DIF	0x8BB7	16
16-DECT	0x0589	16
16-CDMA2000	0xC867	16
16-ARINC	0xA02B	16
16-CHAKRAVARTY	0x2F15	16
16-5G	0x1023	16
15-MPT1327	0x6815	15
15-CAN	0x4599	15
14-DARC	0x0805	14
13-BBC	0x1CF5	13
12-CDMA2000	0xF13	12
12-TELECOM	0x80F	12
11-FLEXRAY	0x385	11
11-5G	0x621	11
10-CDMA2000	0x3D9	10
10-ATM	0x233	10
8-WCDMA	0x9B	8
8-SAE-J1850	0x1D	8
8-DARC	0x39	8
8-DALLAS	0x31	8
8-CCITT	0x07	8
8-AUTOSAR	0x2F	8
8-DVB-S2	0xD5	8
7-MVB	0x65	7
7-MMC	0x09	7
6-CDMA2000-A	0x27	6
6-CDMA2000-B	0x07	6
6-DARC	0x19	6
6-ITU	0x03	6
5-ITU	0x15	5
5-EPC	0x09	5
5-USB	0x05	5
4-ITU	0x3	4
1-PAR	0x1	1

3.2.3.2. --crc-size

Type

integer

Range

\(]0 \to \infty[\)

Examples

--crc-size 8

Size the CRC (divisor size in bits minus one), required if you selected an unknown CRC.

3.2.3.3. --crc-implem

Type

text

Allowed values

STD FAST INTER

Default

FAST

Examples

--crc-implem FAST

Select the CRC implementation you want to use.

Description of the allowed values:

Value	Description
STD	The standard implementation is generic and support any size of CRCs. On the other hand the throughput is limited.
FAST	This implementation is much faster than the standard one. This speedup is achieved thanks to the bit packing technique: up to 32 bits can be computed in parallel. This implementation does not support polynomials higher than 32 bits.
INTER	The inter-frame implementation should not be used in general cases. It allow to compute the CRC on many frames in parallel that have been reordered.

3.2.3.4. References

Crc-LST12

B. Li, H. Shen, and D. Tse. An adaptive successive cancellation list decoder for polar codes with cyclic redundancy check. IEEE Communications Letters (COMML), 16(12):2044–2047, December 2012. doi:10.1109/LCOMM.2012.111612.121898.

Crc-TLLeGal+16

T. Tonnellier, C. Leroux, B. Le Gal, B. Gadat, C. Jégo, and N. Van Wambeke. Lowering the error floor of turbo codes with CRC verification. IEEE Wireless Communications Letters (WCL), 5(4):404–407, August 2016. doi:10.1109/LWC.2016.2571283.