DVBS-APSK Demodulator Baseband

DVB-S2/S2X/SH standard-specific APSK demodulation

• 

Libraries:
Satellite Communications Toolbox / Modulation / Digital Baseband Modulation

Description

The DVBS-APSK Demodulator Baseband block demodulates the input signal using Digital Video Broadcasting (DVB-S2/S2X/SH) standard-specific amplitude phase shift keying (APSK) demodulation.

This icon shows the block with all ports enabled:

Ports

Input

In — DVB-S2/S2X/SH standard-specific APSK modulated signal

scalar | vector | matrix

DVB-S2/S2X/SH standard-specific APSK modulated signal, specified as a scalar, vector, or matrix. When this input is a matrix, each column is treated as an independent channel. This port is unnamed until the Var port is enabled.

Data Types: double | single
Complex Number Support: Yes

Var — Noise variance

positive scalar | vector of positive values

Noise variance, specified as a positive scalar or vector of positive values. When the noise variance or signal power result in computations involving extreme positive or negative magnitudes, see DVB Compliant APSK Soft Demodulation for demodulation decision type considerations.

Dependencies

This parameter applies when Noise variance source is set to Input port.

Data Types: double | single

Output

Out — Demodulated signal

scalar | vector | matrix

Demodulated signal, returned as a scalar, vector, or matrix. The dimensions of the demodulated signal depend on the specified Output type and Decision type. This port is unnamed on the block.

Output type	Decision type	Demodulated Signal Description	Dimensions of Demodulated Signal
Integer	—	Demodulated integer values in the range [0, (M – 1)]	The output signal has the same dimensions as the input signal.
Bit	Hard decision	Demodulated bits	The number of rows in the output signal is log2(M) times the number of rows in the input signal. Each demodulated symbol is mapped to a group of log2(M) elements in a column, where the first element represents the MSB and the last element represents the LSB.
	Log-likelihood ratio	Log-likelihood ratio value for each bit
	Approximate log-likelihood ratio	Approximate log-likelihood ratio value for each bit
M is the value of Modulation order.

Use Output data type to specify the output data type.

Parameters

To edit block parameters interactively, use the Property Inspector. From the Simulink^® Toolstrip, on the Simulation tab, in the Prepare gallery, select Property Inspector.

DVB standard suffix — Standard suffix

S2 | S2X | SH

Standard suffix for DVB modulation variant, specified as S2, S2X, or SH.

Frame length — Frame length

Normal (default) | Short

Frame length, specified as Normal or Short.

Dependencies

This parameter applies only when DVB standard suffix is set to S2 or S2X.

Modulation order — Modulation order

16 (default) | integer

Modulation order, specified as a power of two. The modulation order specifies the total number of points in the constellation of the input signal. The list of valid modulation orders varies depending on the setting for DVB standard suffix and Frame length.

DVB standard suffix	Frame length	Modulation order Options
S2	Normal or Short	16 or 32
S2X	Normal	8, 16, 32, 64, or 256
	Short	16 or 32
SH	Not applicable	16

Code identifier — Code identifier

2/3 | character vector

Code identifier, specified as a character vector. The list of valid code identifier values varies depending on the setting for DVB standard suffix, Frame length, and Modulation order. This table lists the available options for Code identifier values.

Modulation order	DVB standard suffix	Frame length	Code identifier Options
8	S2X	Normal	100/180 or 104/180
16	S2 or S2X	Normal	2/3, 3/4, 4/5, 5/6, 8/9, or 9/10
		Short	2/3, 3/4, 4/5, 5/6, or 8/9
16	S2X	Normal	26/45, 3/5, 28/45, 23/36, 25/36, 13/18, 140/180, 154/180, 100/180, 96/180, 90/180, 18/30, or 20/30
		Short	7/15, 8/16, 26/45, 3/5, or 32/45
32	S2 or S2X	Normal	3/4, 4/5, 5/6, 8/9, or 9/10
		Short	3/4, 4/5, 5/6, or 8/9
32	S2X	Normal	128/180, 132/180, 140/180, or 2/3
		Short	2/3 or 32/45
64	S2X	Normal	128/180 , 132/180, 7/9, 4/5, or 5/6
128	S2X	Normal	135/180 or 140/180
256	S2X	Normal	116/180, 124/180, 128/180, 20/30, or 135/180

For more information, refer to Tables 9 and 10 in the DVB-S2 standard [1] and Table 17a in the DVB-S2X standard [2].

Dependencies

This parameter applies only when DVB standard suffix is set to S2 or S2X.

Constellation scaling — Constellation scaling

Outer radius as 1 (default) | Unit average power

Constellation scaling, specified as Outer radius as 1 or Unit average power.

Dependencies

This input argument applies only when DVB standard suffix is set to S2 or S2X.

Output type — Output type

Integer (default) | Bit

Output type, specified as Integer or Bit.

Decision type — Demodulation decision type

Hard decision (default) | Log-likelihood ratio | Approximate log-likelihood ratio

Demodulation decision type, specified as Hard decision, Log-likelihood ratio, or Approximate log-likelihood ratio. See DVB Compliant APSK Soft Demodulation for algorithm selection considerations.

Dependencies

This parameter applies when Output type is set to Bit.

Noise variance source — Noise variance source

Property (default) | Input port

Noise variance source, specified as:

• Property — The noise variance is set using the Noise variance parameter.

• Input port — The noise variance is set using the Var input port.

Noise variance — Noise variance

1 (default) | positive scalar | vector of positive values

Noise variance, specified as a positive scalar or vector of positive values.

• When specified as a scalar, that value is used on all elements in the input signal.

• When specified as a vector, the vector length must be equal to the number of columns in the input signal. Each noise variance vector element is applied to its corresponding column in the input signal.

When the noise variance or signal power result in computations involving extreme positive or negative magnitudes, see DVB Compliant APSK Soft Demodulation for demodulation decision type considerations.

Dependencies

This parameter applies when Noise variance source is set to Property and Decision type is set to either Log-likelihood ratio or Approximate log-likelihood ratio.

Output data type — Output data type

double (default) | ...

Output data type, specified as one of the acceptable values from this table. Acceptable Output data type values depend on the Output type and Decision type parameter values.

Output type	Decision type	Output data type Options
Integer	Not applicable	double, single, int8, uint8, int16, uint16, int32, or uint32
Bit	Hard decision	double, single, int8, uint8, int16, uint16, int32, uint32, or logical
	Log-likelihood ratio or Approximate log-likelihood ratio	The output signal is the same data type as the input signal.

Dependencies

This parameter applies only when Output type is set to Integer or when Output type is set to Bit and Decision type is set to Hard decision.

Simulate using — Type of simulation to run

Code generation (default) | Interpreted execution

Type of simulation to run, specified as Code generation or Interpreted execution.

• Code generation — Simulate the model by using generated C code. The first time you run a simulation, Simulink generates C code for the block. The model reuses the C code for subsequent simulations unless the model changes. This option requires additional startup time, but the speed of the subsequent simulations is faster than with the Interpreted execution option.

• Interpreted execution — Simulate the model by using the MATLAB^® interpreter. This option shortens startup time, but the speed of subsequent simulations is slower than with the Code generation option. In this mode, you can debug the source code of the block.

Block Characteristics

Data Types	Boolean | double | integer | single
Multidimensional Signals	yes
Variable-Size Signals	no

More About

DVB-S2/S2X/SH

Digital video broadcasting (DVB) standards specify S2, S2X, and SH standard-specific amplitude phase shift keying (APSK) modulation. For further information on the DVB-S2/S2X/SH standards, see [1], [2], and [3], respectively.

DVB Compliant APSK Hard Demodulation

The hard demodulation algorithm applies amplitude phase decoding as described in [4].

DVB Compliant APSK Soft Demodulation

For soft demodulation, two soft-decision log-likelihood ratio (LLR) algorithms are available: exact LLR and approximate LLR. The exact LLR algorithm is more accurate but has slower execution speed than the approximate LLR algorithm.

Note

The exact LLR algorithm computes exponentials using finite precision arithmetic. For computations involving very large positive or negative magnitudes, the exact LLR algorithm yields:

• Inf or -Inf if the noise variance is a very large value

• NaN if the noise variance and signal power are both very small values

The approximate LLR algorithm does not compute exponentials. You can avoid Inf, -Inf, and NaN results by using the approximate LLR algorithm.

Tips

• For faster execution of the DVBS-APSK Demodulator Baseband block, set the Simulate using parameter to:

  • Code generation when using hard decision demodulation.

  • Interpreted execution when using soft decision demodulation.

References

[1] ETSI Standard EN 302 307 V1.4.1. "Digital Video Broadcasting (DVB); Second generation framing structure, channel coding and modulation systems for Broadcasting, Interactive Services, News Gathering and other broadband satellite applications (DVB-S2)." European Telecommunications Standards Institute. Valbonne, France, 2005-03.

[2] ETSI Standard EN 302 307-2 V1.1.1. "Digital Video Broadcasting (DVB); Second generation framing structure, channel coding and modulation systems for Broadcasting, Interactive Services, News Gathering and other broadband satellite applications (DVB-S2X)." European Telecommunications Standards Institute. Valbonne, France, 2015-02.

[3] ETSI Standard EN 302 583 V1.1.1. "Digital Video Broadcasting (DVB); Framing structure, channel coding and modulation for Satellite Services to Handheld devices (SH)." European Telecommunications Standards Institute. Valbonne, France, 2008-03.

[4] Sebesta, J. “Efficient Method for APSK Demodulation.” Selected Topics on Applied Mathematics, Circuits, Systems, and Signals (P. Pardalos, N. Mastorakis, V. Mladenov, and Z. Bojkovic, eds.). Vouliagmeni, Athens, Greece: WSEAS Press, 2009.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2018b

R2024b: Moved to Satellite Communications Toolbox from Communications Toolbox

Previously, DVBS-APSK Demodulator Baseband required Communications Toolbox™.