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Carrier DVB-S2/S2X

DVB-S2/S2X (EN 302307) is introduced to improve the transmission capability in the same bandwidth as DVB-S. More complicated BCH and LDPC coding and high order modulation scheme such as QPSK, 8PSK, 16APSK and 32APSK are adopted.

1. Basic

State

Choice: On |Off

Default: On

Double-click or use the drop-down menu to control the operating state of the carrier.

Format

The format of the carrier.

Frequency Offset

Range: -40.0 to 40.0 MHz

Default: 0.000000 Hz

Set the frequency offset for the carrier relative to the signal generator’s frequency setting. The valid range will be different for every format due to the different over-sampling ratios.

For example, for 2 carriers configuration, set the center frequency of signal generator to 1 GHz, and make the two carriers distributed on the both sides of the center frequency with 5 MHz offset each. Therefore, the actual frequency of each carrier would be 1GHz+5MHz and 1GHz-5MHz respectively.

Initial Phase

Range: 0 to 359 degrees

Set the initial phase of the carrier.

Power

Range: -50 to 0 dB

Set the carrier’s power relative to the signal generator’s amplitude setting.

2. DVB-S2/S2X Settings

Filter Type

Choice: Nyquist \Root Nyquist

Default: Root Nyquist

Double-click or use the drop-down menu to select the filter type.

Conventionally, a data transmission system employs a Nyquist filter whose reply for an impulse is zero (0) for every interval T just before and after a peak (T: data transmission interval). As replies of adjacent data are zero on a sample point of other sampled data, interference between codes can be prevented.

To function as above, a Nyquist filter whose amplitude becomes half at the point where Nyquist frequency fN (=1/2T) is used, and it is odd-symmetrically rolled off with a squared cosine around the half amplitude point in the cutoff area. In this case the phase characteristics is not considered, or is designed to have linear phase characteristics usually.

Instead of a simple Nyquist filter, low-pass filters (root Nyquist filters) having equal amplitude are set for transmission and reception and their characteristics are made the same as that of the Nyquist filter above. In this case, the root Nyquist filter must have cosine characteristics that can be made the squared cosine characteristics above.

Roll-off Factor

Range: 0 to 1

Default: 0.35

Set the roll-off factor of DVB-S2/S2X.

DVB-S2/S2X have taken into consideration of various requirements of multiple service. For one thing, it supports a wide range of code rates (from 1/4 up to 9/10); for another, roll-off factor can be selected among 0.35, 0.25, 0.2, instead of the fixed 0.35 in DVB-S. With lower roll-off factor, higher spectrum efficiency can be achieved.  

Symbol Rate

Range: 300KHz to 100MHz

Default: 10MHz

Set the symbol rate of DVB-S2/S2X.

The symbol rate is matched to given transponder characteristics, since DVB-S.2 is suitable for use on different satellite transponder bandwidths and frequency bands, and in the case of multiple carriers per transponder (FDM), to the frequency plan adopted.

Support DVB-S2X

Choice: True | False

Default: False

Coupling: VL-SNR Header, FEC Frame, Modulation Type and Code Rate

Double-click or use the drop-down menu to select whether to support DVB-S2X.

VL-SNR Header

Choice: True | False

Default: False

Coupling: FEC Frame, Modulation Type and Code Rate. VL-SNR Header can only be activated in DVB S2X

Double-click or use the drop-down menu to select whether to insert VL-SNR Header in PLFRAME in DVB-S2X.

BB Header

Choice: On | Off

Default: On

Double-click or use the drop-down menu select whether to transmit BBHEADER in BBFRAME.

FEC Frame

Choice: Normal | Medium | Short

Default: Normal

Coupling: Modulation Type, Code Rate and Number of LDPC Blocks

Double-click or use the drop-down menu to select whether to use normal, medium or short LDPC block size in DVB-S2/S2X.

FEC encoding performs outer coding (BCH), Inner Coding (LDPC) and Bit interleaving. The input stream is composed of BBFRAMEs and the output stream of FECFRAMEs. Each BBFRAME (Kbch bits) shall be processed by the FEC coding subsystem, to generate a FECFRAME (nldpc bits). The parity check bits (BCHFEC) of the systematic BCH outer code shall be appended after the BBFRAME, and the parity check bits (LDPCFEC) of the inner LDPC encoder shall be appended after the BCHFEC field, as shown below.

Figure 2 FEC Encoding Data Structure

LDPC encoding provides two kinds of frame length, one is normal frame with length 64800 bit; the other is short frame with length 16200 bit (1/4 of normal frame), shown in the following figure.

Table 1 FECFRAME (normal and short) configurations and application areas

Modulation Type

Choice: BPSK | BPSK-S | QPSK | 8PSK | 8APSK | 16 APSK | 32 APSK | 64 APSK | 128 APSK | 256 APSK

Default: QPSK

Coupling: Code Rate

Double-click or use the drop-down menu to select the modulation type.

Code Rate

Choice: 1/5 | 1/4 | 1/3 | 2/5 | 1/2 | 3/5 | 3/5-L | 2/3 | 2/3-L | 3/4 | 4/5 | 5/6 | 2/9 | 7/9 | 8/9 | 9/10 | 11/45 | 13/45 | 9/20 | 11/20 | 4/15 | 8/15 | 11/15 | 5/9 | 26/45 | 28/45 | 29/45 | 31/45 | 32/45 | 23/36 | 25/36 | 13/18 | 77/90

Default: 3/4

Coupling: determines the value of Useful Bit Rate and Supported File Size

Double-click or use the drop-down menu to select the LDPC code rate of DVB-S2/S2X.

Insert Pilot

Choice: True | false

Default: True

DouDouble-click or use the drop-down menu to select whether to insert pilot at the physical layer in DVB-S2/S2X. For the VL-SNR mode, Insert Pilot is always True.

When Insert Pilot is enabled, a PILOT BLOCK composed of P = 36 pilot symbols will be inserted. Each pilot shall be an un-modulated symbol, identified by I = (1/√2), Q = (1/√2). The first PILOT BLOCK shall be inserted 16 SLOTs after the PLHEADER, the second after 32 SLOTs and so on, as represented in figure 13. If the PILOT BLOCK position coincides with the beginning of the next SOF, then the PILOT BLOCK is not transmitted. Besides, the pilot presence/absence in VCM (Variable Coding and Modulation) and ACM (Adaptive Coding and Modulation) can be changed on a frame-by-frame basis.

CRC-8 Encoder

Choice: True | False

Default: True

Double-click or use the drop-down menu to select whether to use CRC-8 before channal coding in DVB-S2/S2X.

Number of LDPC Blocks

Range: 188, 2*188, 3*188...

Default: 188

Select the number of LDPC blocks to be generated.

This is read only when Data Source Type is not Test Pattern.

Multi-path Channel

Default: OFF

Click in the right side of the cell to open the Multi-path Channel configuration window.

A multi-path channel which contains up to 20 paths can be set according to your test requirements.

3. Data Source Settings

Useful Bit Rate

The useful bit rate. The bit rate is determined by current bandwidth, encoding, modulation and framing configurations.

Supported File Size

The supported file size for current settings.

Payload

The TS payload settings.

Data Source Type

Normal: Test Pattern | Demo File | TS File | TS File Wizard

Default: Test Pattern

Double-click or use the drop-down menu to select which type to be used as the data source.

If "TS File" is selected, "File Name" is required; If "TS File Wizard" is selected, "File Wizard" is available.

Learn more about the different Data Source Types, refer to the page Data Source Type.

Pattern Bits

The data bits used as test pattern.

Click the right button to open "Data Pattern Selection" dialog and select test pattern to use.

SYNC Insertion

Choice: True | False

Default: False

Double-click or use the drop-down menu to determine whether a SYNC byte (0x47) should be inserted into the test pattern.

Video Type

Choice: NTSC | PAL | HD 1920x1080

Default: PAL

Double-click or use the drop-down menu to select whether the PAL, NTSC or HD 1920x1080 file is demo File. This cell is only enabled when Data Source Type is Demo File.

In DVB-S2/S2X, we provide both SDTV (Standard Definition Television) and HDTV (High Definition Television).

HD 1920x1080 is a choice for HDTV. 

There are two predominant worldwide video-based source material formats (SDTV), shown as follows:

• NTSC: National Television System Committee, the system used in America & Canada

• PAL: Phase Alternating Line, the system used in Western Europe and Australia

Table 2 NTSC parameters list

Table 3 PAL parameters list

File Name

Click on in the right side of the cell, and select the file name you set as payload.

The name of the TS file as data source.

Click the right button to select and open a TS file.

If DVB-T/H, DVB-C, DVB-S, ISDB-T "RS Encoder" is off or ISDB-T "Re-Multiplexer" is off, a TS file with 204 byte packets is required;

If ATSC "RS Encoder" is off, TS file with 208 byte packets is required.

For the other situation, TS file with 188 byte packets is required.

Auto Stuffing

Choice: ON | OFF

Default: ON

This cell is only enabled when Data Source Type is TS File. Double-click or use the drop-down menu to select whether or not to use auto-stuffing to agree with transport bit rate.

Loop Play

Choice: ON | OFF

Default: ON

This cell is only enabled when Data Source Type is TS File. Double-click or use the drop-down menu to determine whether or not to modify the TS file to make it suitable for loop play.