3.2.8. Quantizer parameters

The quantizer is a module that ensures the real numbers transformation from a floating-point representation to a fixed-point representation. This module is enabled only if the receiver part of the communication chain works on a fixed-point representation (cf. the --sim-prec, -p parameter).

Warning

Some decoders are not fixed-point ready, please refer to the decoders documentation for more details.

3.2.8.1. --qnt-type

Type

text

Allowed values

CUSTOM POW2

Default

POW2

Examples

--qnt-type CUSTOM

Select the quantizer type.

Description of the allowed values (\(Y_i\) stands for a floating-point representation and \(Q_i\) for the fixed-point representation of a real number):

Value	Description
CUSTOM	\(Q_i = \begin{cases} +v_{sat} & \text{when } v_i > +v_{sat} \\ -v_{sat} & \text{when } v_i < -v_{sat} \\ v_i & \text{else} \end{cases}\), with \(v_i = \lfloor \frac{Y_i}{\Delta} \rceil \text{ and } v_{sat} = 2^{p_b - 1} - 1 \text{ and } \Delta = \frac{|p_r|}{v_{sat}}\)
POW2	\(Q_i = \begin{cases} +v_{sat} & \text{when } v_i > +v_{sat} \\ -v_{sat} & \text{when } v_i < -v_{sat} \\ v_i & \text{else} \end{cases}\), with \(v_i = \lfloor Y_i * F \rceil \text{ and } v_{sat} = 2^{p_b - 1} - 1 \text{ and } F = 2^{p_d}\)

Where \(p_r\), \(p_b\) and \(p_d\) are respectively given through the --qnt-range, --qnt-bits and --qnt-dec parameters.

3.2.8.2. --qnt-implem

Type

text

Allowed values

STD FAST

Default

STD

Examples

--qnt-implem FAST

Select the implementation of the quantizer.

Description of the allowed values:

Value	Description
STD	Select a standard implementation.
FAST	Select a fast implementation, only available for the POW2 quantizer.

3.2.8.3. --qnt-range

Type

real number

Examples

--qnt-range 1.0

Select the min/max bounds for the CUSTOM quantizer.

3.2.8.4. --qnt-bits

Type

integer

Default

8 else see Table 3.8

Examples

--qnt-bits 1

Set the number of bits used in the fixed-point representation.

Note

If the amplitude of the current number exceeds the maximum amplitude that can be represented with the current quantization, then a saturation is applied (c.f. the --qnt-type parameter).

Table 3.8 Default values of the total number of bits for the different codes.

Code	Value
LDPC	6
POLAR	6
REP	6
RSC	6
RSC_DB	6
TPC	6 on 8-bit and 8 on 16-bit
TURBO	6
TURBO_DB	6

3.2.8.5. --qnt-dec

Type

integer

Default

3 else see Table 3.9

Examples

--qnt-dec 1

Set the position of the decimal point in the quantified representation.

Table 3.9 Default values of the decimal point position for the different codes.

Code	Value
LDPC	2
POLAR	1
REP	2
RSC	1 on 8-bit and 3 on 16-bit
RSC_DB	1 on 8-bit and 3 on 16-bit
TPC	2 on 8-bit and 3 on 16-bit
TURBO	2 on 8-bit and 3 on 16-bit
TURBO_DB	2 on 8-bit and 3 on 16-bit