# 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 CUSTOM POW2 POW2 --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 STD FAST STD --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 --qnt-range 1.0

Select the min/max bounds for the CUSTOM quantizer.

## 3.2.8.4. --qnt-bits¶

Type: integer 8 else see Table 3.8 --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 3 else see Table 3.9 --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