3.2.4.4.1. Polar Encoder parameters

3.2.4.4.1.1. --enc-type

Type:text
Allowed values:POLAR AZCW COSET USER
Default:POLAR
Examples:--enc-type AZCW

Type of the encoder to use in the simulation.

Description of the allowed values:

Value Description
POLAR Select the standard Polar encoder.
AZCW See the common --enc-type parameter.
COSET See the common --enc-type parameter.
USER See the common --enc-type parameter.

3.2.4.4.1.2. --enc-no-sys

Enable non-systematic encoding. By default the encoding process is systematic.

3.2.4.4.1.3. --enc-fb-gen-method

Type:text
Allowed values:FILE GA TV
Examples:--enc-fb-gen-method FILE

Select the frozen bits generation method.

Description of the allowed values:

Value Description
GA Select the GA method from [Tri12].
TV Select the TV method which is based on Density Evolution (DE) approach from [TV13], to use with the --enc-fb-awgn-path parameter.
FILE Read the best channels from an external file, to use with the --enc-fb-awgn-path parameter.

Note

By default, when using the GA or the TV method, the frozen bits are optimized for each SNR point. To override this behavior you can use the --enc-fb-sigma parameter.

Note

When using the FILE method, the frozen bits are always the same regardless of the SNR value.

3.2.4.4.1.4. --enc-fb-awgn-path

Type:path
Rights:read only
Examples:--enc-fb-awgn-path example/path/to/the/right/place/

Set the path to a file or a directory containing the best channels to select the frozen bits.

An ASCII file is expected, for instance, the following file describes the most reliable channels optimized for a codeword of size \(N = 8\) and for an AWGN channel where the noise variance is \(\sigma = 0.435999\):

8
awgn
0.435999
7 6 5 3 4 2 1 0

Given the previous file, if we suppose a Polar code of size \(N = 8\) with \(K = 4\) information bits, the frozen bits are at the 0, 1, 2, 4 positions in the codeword. The strategy is to freeze the less reliable channels.

Warning

The FILE frozen bits generator expects a file and not a directory.

Warning

The TV frozen bits generator expects a directory and not a file. AFF3CT comes with input configuration files, a part of those configuration files are a set of best channels pre-generated with the TV method (see conf/cde/awgn_polar_codes/TV/).

3.2.4.4.1.5. --enc-fb-sigma

Type:real number
Examples:--enc-fb-sigma 1.0

Selects the noise variance \(\sigma\) for which the frozen bits will be optimized. All the noise points in the simulation will use the same frozen bits configuration.

3.2.4.4.1.6. References

[TV13]I. Tal and A. Vardy. How to construct polar codes. IEEE Transactions on Information Theory (TIT), 59(10):6562–6582, October 2013. doi:10.1109/TIT.2013.2272694.
[Tri12]P. Trifonov. Efficient design and decoding of polar codes. IEEE Transactions on Communications (TCOM), 60(11):3221–3227, November 2012. doi:10.1109/TCOMM.2012.081512.110872.