Digital Video Broadcasting DVB in Satellite Communications

Technical Introduction to Geostationary Satellite Communication Systems Original Prepared by Telesat Canada

Slide Number 1Rev -, July 2001



Introduction to DVBDVB stands for Digital Video Broadcasting.

DVB is the most used transport stream standard for the distribution of digital video material over satellite and cable.

At the end of 1991, a consortium of European broadcasters, manufacturers, public and private media groups, and regulatory bodies came together to form the European Launching Group (ELG). The ELG was tasked to develop a digital terrestrial TV standard.

In September 1993 a Memorandum of Understanding (MOU) was signed by all members of the ELG. The MOU established the rules by which the members would work together to develop the new standard.

Once the MOU was signed, the ELG became the DVB group.

Vol 6: Digital Video

Sec 5: Digital Video Broadcasting

6.5.1: Introduction to DVB



Introduction to DVBThe DVB consortium now comprises over 225 organizations from more than 30 countries around the world.

While DVB was being defined in Europe, a similar program was taken place in the US (ATSC), driven by an advisory committee of the United States Federal Communications Commission (FCC).

The DVB standard was from the start intended to define an internationally accepted standard for the distribution of digital television programming.

ATSC’s main goal was to provide a guideline to the FCC to define a US Standard for the distribution of digital television.






Introduction to DVB The DVB consortium did not define a new standard for the compression of audio or video programs. Instead, it opted to use the MPEG 2 standard.

The DVB standard defines the rules regarding framing structure, channel coding, modulation scheme, and the service information table (SIT), and it provide some guidelines for the implementation of a common conditional access system.

The first standard issued by the DVB consortium defines the distribution of digital programming over satellite using the QPSK modulation scheme. This standard was issue at the end of 1993. The second major standard was one defining cable distribution using 64QAM (1994). A terrestrial distribution standard was issued in 1996.






Introduction to DVBThe most important DVB standards are:

Framing structure, channel coding and modulation DVB-S Satellite SystemsDVB-C Cable SystemsDVB-T Digital Terrestrial SystemsDVB-MT Microwave Digital Terrestrial Systems

Conditional AccessDVB-CA Conditional Access SystemDVB-CS Common Scrambling System

OtherDVB-SI Service Information SystemDVB-VBI VBI informationDVB-Data Data Information






Philosophy of the DVB ConsortiumThe DVB consortium’s philosophy is based on the following four factors:

Open System: The standards are available worldwide to anyone for a nominal cost.

Interoperable: Equipment that complies to the DVB standard is fully compatible with other DVB-compliant equipment built by another manufacturer.

Flexible: Supports various video formats (PAL, NTSC, SECAM, HDTV), audio, data signals. It will also support multimedia data and interactive services.

Market-led: This is not a government driven standard. The standard was developed for manufacturers and users of the technology by manufacturing and user groups.



6.5.2: Philosophy of the DVB Consortium



MPEG 2 SystemThe DVB standard supports the MPEG 2 PSI tables

Program Association Table (PAT),

Program Map Table (PMT)

Conditional Access Table (CAT).

The DVB standard defines its own Network Information Table (NIT) based on the recommendations from the MPEG group. The specification for the NIT will be discussed in a later part of this section dealing with the DVB SI table.

The standard supports four different video formats and three aspect ratios. The standard supports MPEG 2 layer II audio.

Vol 6: Digital Video, Sec 5: Digital Video Broadcasting

Part 3: MPEG 2 Standard

6.5.3.1: MPEG 2 System



Program Associated Table (PAT)The PAT is used to indicate the Packet Identifier (PID) value for each program or SI table within the the MPEG transport stream. The PAT provides the PID value for the PMT associated with each program.

The PID value is used by the decoder to sort the different packets so that it can later regroup those with similar PID’s to recreate the original program elementary stream (PES).

The PAT is always set with PID 0x0000.

DVB recommends that the PAT should be transmitted at an interval equal to or less than 100 milliseconds.






Figure 6.5.3.1a Relation Between PAT, PMT, CAT and NIT

P A T P M T0x0036

PID 0x0036

PID 0x0037 P M T0x0037

C A T0x0001

N IT0x0010

V ideo0x1420

A ud io0x1430

V ideo0x155 0

A ud io0x156 0

A ud io0x157 0

PID 0x0001

PID 0x0010

PID 0x1420

PID 0x1430

PID 0x1550

PID 0x1560

PID 0x1570

Pro gram 1

Pro gram 2






Program Associated Table (PAT)Table ID assignment0x00 PAT0x01 CAT0x02 program map section0x03 transport stream description0x40 network info (actual network)0x41 network info (other network)0x42 service description section (actual

transport stream)0x46 service description section(other

transport stream)0x4A bouquet association section0x4E event information section (actual

transport stream, present/following)

Program Association Table 0x0000

O ne loopper

program

table ID 0x00

section syntax indicator

8

1

zero 1

reserved 2

section length 12

transport stream ID 16

reserved 2

version num ber 5

current next indicator 1

section number 8

last section num ber 8

program zero 16

reserved 3

program num ber 3

reserved 13

program m ap PID 5

netw ork PID 13

CRC 32 32



6.5.3.1: MPEG 2 SystemFigure 6.5.3.1ba P

rogram A

ssociated Table (PA

T)



Program Associated Table (PAT)Table ID assignment0x004F event information table (other

transport stream, present-following)

0x0070 time date section0x0071 running status section0x0072 stuffing section0x0073 time offset section0x007E discontinuity information section0x007F selection information section

Program Association Table 0x0000

O ne loopper

program

table ID 0x00


8

1

zero 1

reserved 2

section length 12


reserved 2

version num ber 5


section number 8


program zero 16

reserved 3

program num ber 3

reserved 13

program m ap PID 5

netw ork PID 13

CRC 32 32



6.5.3.1: MPEG 2 SystemFigure 6.5.3.1bb P

rogram A

ssociated Table (PA

T)



Program Map Table (PMT)One PMT per program or service. Each PMT is assigned a PID by the compression system.

Table ID 0x02.

The PMT is used to identify the PID of each PES found in this service. It is also used to identify the corresponding Program Clock Reference (PCR) for this service.

Program M ap Table (PID assigned)

One loopper

elem entarystream

table ID 0x02


8

1

zero 1

reserved 2

section length 12

program num ber 16

reserved 2

version num ber 5


section num ber 8


PCR PID 13

reserved 4

descriptor

reserved 8

stream type 3

program info length 12

CRC 32 32

reserved 3

reserved 13

elem entary PID 4

reserved 12

descriptor

ES info length 5



6.5.3.1: MPEG 2 SystemFigure 6.5.3.1ca P

rogram M

ap Table (PM

T)



Program Map Table (PMT)A program could consist of one video PES and the audio PES associated with the video.

This program would be assigned one PMT which would direct the decoder to the PID associated to that video and audio PES.

Another program could consist of the same video PES and another audio PES (another language) associated with the video.

A different PMT would be used for this program.

Program M ap Table (P ID assigned)

One loopper

elem en tarystream

tab le ID 0x02


8

1

zero 1

reserved 2

section leng th 12

program num ber 16

reserved 2

version number 5

current next ind icator 1

section num ber 8


PC R PID 13

reserved 4

descriptor

reserved 8

stream type 3

program info length 12

CRC 32 32

reserved 3

reserved 13

elem entary PID 4

reserved 12

descriptor

ES info length 5



6.5.3.1: MPEG 2 SystemFigure 6.5.3.1cb P

rogram M

ap Table (PM

T)



PAT PM T0x0036

PID 0x0036

PID 0x0037 PM T0x0037

C AT0x0001

N IT0x0010

V ide o0x1420

A ud io0x1430

V ideo0x1550

A ud io0x1560

A ud io0x1570

PID 0x0001

PID 0x0010

PID 0x1420

PID 0x1430

PID 0x1550

PID 0x1560

PID 0x1570

Pro gram 1

Program 2

PM T0x0038

V ideo0x1 420

A ud io0x1 440

PID 0x1420

PID 0x1440

Pro gram 3

PID 0x0038

PID 0x1420is present in

program 1 and 3

Figure 6.5.3.1d P MT Table when Sharing Two Video PES’s between Three Programs






Program Map Table (PMT)PMT descriptor and their tag valueVideo stream 0x02 Copyright0x0DAudio stream 0x03 Maximum bitrate 0x0EHierarchy 0x04 Private data indicator 0x0FRegistration 0x05 Smoothing buffer0x10Data stream alignment 0x06 STD0x11Target background grid 0x07 IBP0x12Video window 0x08 User private0x14CA 0x09 Mosaic0x51ISO 639 language 0x0A Stream identifier0x52System clock 0x0B Teletext0x56Multiplex buffer utilization 0x0C Subtitling0x59

Service move0x60






Conditional Access Table (CAT)PID address set to 0x0001.

Table ID 0x01.

The CAT provides information on the conditional access system used within this multiplex (if any).

The specific information for the CA system is proprietary to the manufacturer and hence not readily available.

The CAT must indicate the location of the EMM (Entitlement Management Message).

Conditional Access Table 0x0001

table ID 0x01


8

1

zero 1

reserved 2

section length 12

reserved 18

reserved 2

version num ber 5


section num ber 8


descrip tor

CR C 32 32




Figure 6.5.3.1e Conditional Access Table (CAT)


Slide Number 17Rev -, July 2001 Vol 6: Digital Video, Sec 5: Digital Video Broadcasting


6.5.3.2: Video

Figure 6.5.3.2 MPEG-2 Profiles and Levels



VideoDVB adopted the MPEG 2 standard, but has put some restrictions on, and additions to, that standard.

The DVB standards state that the system shall comply with the following profiles and levels:

Standard Definition Television (SDTV)

• Main Profile and Main Level

High Definition Television (HDTV)

• Main Profile and High Level

The system can also operate at one of the other profiles or levels. The DVB standard supports 25 and 30 Hz SDTV or HDTV systems.



6.5.3.2: Video



VideoThe DVB standard specifies that compliant systems will at least support the following aspect ratios:

4:3 (standard home television format)

16:9 (wide television format)

2.21:1 (35 mm film format… this aspect ratio is only an option with SDTV systems)



6.5.3.2: Video



VideoA DVB compliant system shall support a least the following luminance resolutions (horizontal x vertical) for a full screen picture:

25 Hz SDTV 30 Hz SDTV

720 x 576 720 x 480

544 x 576 640 x 480

480 x 576 544 x 480

352 x 576 480 x 480

352 x 288 352 x 480

352 x 240



6.5.3.2: Video



VideoThe DVB standard specifies that the luminance resolution for a 25 and 30 Hz HDTV signal shall not exceed:

• 1152 lines per frame

• 1920 luminance samples per line

The DVB standard recommends that a 25 and 30 Hz HDTV bitstream have a luminance resolution for one picture frame of:

• 1080 lines per frame

• 1920 luminance samples per line with an associated frame rate of 25 Hz or 29.97 Hz with two interlaced fields per frame



6.5.3.2: Video



AudioThe DVB standard supports the MPEG 2 Audio Layer II standards. Compliance with MPEG 2 Audio Layer III is optional, not mandatory.

The minimum audio requirements specified in the DVB standard are:

MPEG 1 single channel

MPEG 1 dual channel

MPEG 1 joint stereo

MPEG 1 stereo

MPEG 2 multi-channel audio, backward compatible to MPEG 1 (mandatory for encoders, but not for integrated receiver decoders (IRD))



6.5.3.3: Audio



AudioThe audio will support the following sampling rates:

32 kHz, 44.1 kHz and 48 kHz

Support for the following sampling rates is optional:

16 kHz, 22.05 kHz and 24 kHz

The following bit rates are supported:

Layer I 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416 or 448 kbps

Layer II 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, or 384 kbps



6.5.3.3: Audio



PM TProgram n

PATPID 0x0000

CATPID 0x0001

PM TProgram 2

PM TProgram 1

M PEG PSI DVB M andatory S I Tables

NITPID 0x0010(Actual TS)

PID forPM T is

Assigned

SDTPID 0x0011(Actual TS)

EITPID 0x0012(Actual TS

present/fo llow ing)

TDTPID 0x0014

(T im e and Date)

DVB Optional S I Tables

NITPID 0x0010(O ther TS)

SDTPID 0x0011(O ther TS)

EITPID 0x0012(O ther TS

present/fo llow ing)

RSTPID 0x0013

BATPID 0x0011

EITPID 0x0012(Actu al TSschedule)

EITPID 0x0012(O ther TSschedu le)

TOTPID 0x0014

STPID 0x0010 to

PID 0x0014



6.5.4: DVB SI Tables

Figure 6.5.4 DVB SI Tables



DVB Mandatory SI TablesFor a system to be DVB compliant it must support the following SI tables:

PAT - Program Association Table (MPEG)

CAT - Conditional Access Table (MPEG)

PMT - Program Map Table (MPEG)

NIT - Network Information Table (DVB)

SDT - Service Description Table (DVB)

EIT -Event Information Table (DVB)

TDT - Time and Date Table (DVB)


Part 4: DVB SI Tables

6.5.4.1: DVB Mandatory SI Tables



Network Information Table (NIT)PID address set to 0x0010.

Table ID 0x40 (actual network.)

Table ID 0x41 (other network-optional.)

The NIT provides information on a group of programs or transport streams. The NIT is used to provide information on the system used to deliver the data stream.

More than one NIT can be identified per system. This can be useful when you need to identify a present and past network (e.g. combining service from two networks in a new system.)

Network Information Table 0x0010

table ID (refer to text)


8

1

reserved for future use 1

reserved 2

section length 12


reserved 2

version number 5


section number 8

last section number 8


network descriptors length 12


original network ID 13

reserved future use 5

transport stream loop length 12

CRC 32 32

descriptor


transp. descrip. length 13

descriptor




Figure 6.5.4.1aa Netw

ork Information Table (N

IT)





Figure 6.5.4.1b Example: Combining Two Transport Streams in a New Transport Stream



Network Information Table (NIT)The NIT can be used to identify whether the delivery system is for satellite or cable media. A satellite IRD will disregard the incoming transport stream if the NIT identifies the transport stream as being delivered by a system other than a satellite system (e.g. a cable system).

The NIT can be used to link the information from several satellite services as if they were one system. The NIT enables the sharing of information such as the Electronic Program Guide (EPG) of a Direct to Home (DTH) system.

N etw ork In form ation Table 0x0010

table ID (re fer to text)


8

1

reserved for fu ture use 1

reserved 2

section leng th 12


reserved 2

version number 5


section num ber 8



netw ork descrip tors length 12


orig ina l netw ork ID 13

reserved fu ture use 5

transport stream loop leng th 12

C RC 32 32

descriptor



descriptor




Figure 6.5.4.1ab Netw


IT)



Network Information Table (NIT)NIT Descriptors:Network name 0x40

Service list 0x41

Stuffing 0x42

Satellite delivery system 0x43

Cable delivery system 0x44

Linkage 0x4A

Terrestrial delivery system 0x5A

Multilingual network name 0x5B

Private data specifier 0x5F

N etw ork In form ation Table 0x0010

table ID (re fer to text)


8

1


reserved 2

section leng th 12


reserved 2

version number 5


section num ber 8



netw ork descrip tors length 12




transport stream loop leng th 12

C RC 32 32

descriptor



descriptor




Figure 6.5.4.1ac Netw


IT)



Service Description Table (SDT)PID address set to 0x0011

Table ID 0x40 (actual stream)

Table ID 0x41 (other stream-optional)

Each transport stream is assigned a SDT sub-table.

Service Description Table 0x0011



8

1

reserve fo r future use 1

reserved 2

section length 12


reserved 2

version num ber 5


section num ber 8


orig ina l network ID 16



EIT schedule flag 1

descrip tor

service ID 16

C RC 32 32

EIT pres/foll flag 1

running status 3

free CA m ode 1

descrip tor loop length 12

pres/foll = p resent fo llow ing




Figure 6.5.4.1ca Service Description Table (SDT)



Service Description Table (SDT)The SDT is used to provide information on the following parameters:

• Service name

• Service provider

• Presence of EIT schedule for service

• Scrambling ON/OFF• Name of the bouquet service

(grouping of services)• Linkage to a network or system

(e.g. DirectTV)

Service Description Tab le 0x0011



8

1

reserve for fu ture use 1

reserved 2

section length 12


reserved 2

version num ber 5


section num ber 8


original netw ork ID 16



E IT schedule flag 1

descrip tor

service ID 16

C RC 32 32

E IT pres/fo ll flag 1

runn ing status 3

free CA m ode 1

descriptor loop length 12

pres/fo ll = p resent fo llow ing




Figure 6.5.4.1cb Service Description Table (SDT)



Service Description Table (SDT)SDT DescriptorsStuffing 0x42Bouquet name 0x47Service 0x48Country availability 0x49Linkage 0x4ANVOD reference 0x4BTime shifted service 0x4CMosaic 0x51CA identifier 0x53Telephone 0x57Multilingual service name 0x5DPrivate data specifier 0x5F

Service Description Tab le 0x0011



8

1

reserve for fu ture use 1

reserved 2

section length 12


reserved 2

version num ber 5


section num ber 8


original netw ork ID 16



E IT schedule flag 1

descrip tor

service ID 16

C RC 32 32

E IT pres/fo ll flag 1

runn ing status 3

free CA m ode 1

descriptor loop length 12

pres/fo ll = p resent fo llow ing




Figure 6.5.4.1cc Service Description Table (SDT)



Event Information Table (EIT)PID address set to 0x0012

• Table ID 0x4E (actual stream, present/following)

• Table ID 0x4F (other stream, present/following)

• Table ID 0x50-0x5F (actual stream, schedule)

• Table ID 0x60-0x6F (other stream, schedule)

The EIT is used to transmit information about the services provided by the different programs within the multiplex.

Event In form ation Table 0x0012



8

1

reserve for future use 1

reserved 2

section length 12

service ID 16

reserved 2

version num ber 5


section number 8




start tim e 6

dura tion 1

descrip tor

event ID 16

C RC 32 32

runn ing status 1

free C A m ode 1

descriptor loop leng th 12

segm ent last section no 8

last tab le ID 8




Figure 6.5.4.1da Event Inform

ation Table (EIT)



Event Information Table (EIT)The EIT provides information on the present service (e.g. “S.L. CHI”), next service (e.g. “JADAL”) and future service (e.g. “American Movie”) for each program. In this example the program would consist of the video and audio PES for MTV, Arabsat 3A, Fourth Bouquet.

Example:Present service S.L. CHI

(20:30 to 21:30)

Following service JADAL

(21:30 to 23:30)

Future service American Movie

(23:30 to 01:30)




8

1


reserved 2

section length 12

service ID 16

reserved 2

version num ber 5


section number 8




start tim e 6

dura tion 1

descrip tor

event ID 16

C RC 32 32

runn ing status 1

free C A m ode 1



last tab le ID 8




Figure 6.5.4.1db Event Inform

ation Table (EIT)



Event Information Table (EIT)EIT DescriptorsStuffing 0x42Linkage 0x4AShort event 0x4DExtended event 0x4ETime shifted event 0x4FComponent descriptor 0x50CA identifier 0x53Content 0x54Parental rating 0x55Telephone 0x57Multilingual component 0x5EPrivate data specifier 0x5FShort smoothing buffer 0x61




8

1


reserved 2

section length 12

service ID 16

reserved 2

version num ber 5


section number 8




start tim e 6

dura tion 1

descrip tor

event ID 16

C RC 32 32

runn ing status 1

free C A m ode 1



last tab le ID 8




Figure 6.5.4.1dc Event Inform

ation Table (EIT)



Time and Date Table (TDT)PID address set to 0x0014

Table ID 0x70

The TDT is used to transmit the actual UTC time. The time is coded as a modified Julian Date (MJD).

The IRD may use the TDT to synchronize internal clocks. The TDT is transmitted at least every 30 seconds.

Tim e and D ate Table 0x0014

table ID 0x70


8

1


reserved 2

section length 12

U TC tim e 40




Figure 6.5.4.1e Time and Date Table (TDT)



DVB Optional SI TableThe DVB standard also defines the usage of other SI tables that are not required for DVB compliance. The implementation of these tables is left to the manufacturers discretion and may or may not be required, depending on the application for the multiplex system.

NIT - Network Information Table (other network)

SDT - Service Description Table (other stream)

EIT - Event Information Table (other stream)

BAT - Bouquet Association Table

RST - Running Status Table

ST - Stuffing Table

TOT - Time Offset TableVol 6: Digital Video, Sec 5: Digital Video Broadcasting


6.5.4.2: DVB Optional SI Tables



Optional NIT, SDT and EIT TablesPID address 0x0010 for NIT

0x0011 for SDT

0x0012 for EIT

Table ID 0x41 for NIT (other network)

0x41 for SDT (other stream)

0x4F for EIT (other stream, present/following)

0x4F for EIT (other stream, schedule)

The optional NIT, SDT and EIT tables use the same framing structure explained in the previous sections.






Optional NIT, SDT and EIT TablesThe NIT can be used to provide information on the network from which a transport stream originated. The implementation of the NIT for other networks is optional. The implementation of the NIT for the actual network is mandatory.

The optional SDT table provides information on streams from another mutliplex. Depending on the way this table is implemented, the optional SDT table can reduce the access time of a consumer IRD (e.g. DTH application) seeking obtain service information from another multiplex.

The implementation of the SDT for other stream is optional. The implementation of the SDT for the actual stream is mandatory.






Optional NIT, SDT and EIT TablesThe EIT optional table provides present/following and scheduling information for content located on another stream. This, then, allows the sharing of information between streams, which in turn reduces the acquisition time for this information within IRDs.

The implementation of the EIT for other streams is optional. The implementation of the EIT for the actual stream is mandatory.






Bouquet Association Table (BAT)PID address set to 0x0011

Table ID 0x4A

The BAT is an optional table. The BAT is used to group several services together. The services under a BAT could be common to several networks. Several bouquets could be found within the same network.

The BAT could be used to group television programs from the same provider that are distributed on a different multiplex on the same satellite.

Bouquet Association Table 0x0011

table ID 0x4A


8

1


reserved 2

section length 12

bouquet ID 16

reserved 2

version num ber 5


section num ber 8




transport stream loop length 12

TS descr length

bouquest descrip tors length 12

CRC 32 32


original network ID 16





Figure 6.5.4.2a Bouquet A

ssociation Table (BA

T)



Running Status Table (RST)PID address set to 0x0013

Table ID 0x71

The RST provides a means by which the IRDs or VCRs can perform a very accurate switching (e.g. VCR recording) at the start of an event. This is done by setting the equipment to detect the RST command and then waiting for the table to be received.

The running status table is not transmitted in a continuous fashion. It is transmitted at predetermined times for the control of the IRDs or VCRs.

R unning Status Table 0x0013

table ID 0x71


8

1


reserved 2

section length 12

runn ing status

service ID 16

event ID 16



orig inal network ID 16




Figure 6.5.4.2b Running Status Table (RST)



Stuffing Table (ST)PID address set to 0x0013

Table ID 0x72

The ST table is an optional table. It is used to authorize the replacement of complete SI tables.

This is sometime required to remove invalid tables that are not required by specific delivery systems.

Stuffing Table

table ID 0x72


8

1


reserved 2

section length 12

data byte 8




Figure 6.5.4.2c Stuffing Table (ST)



Time Offset Table (TOT)PID address set to 0x0014

Table ID 0x73

The TOT table is used to supply the UTC time/date. It also provides the difference between that time and the local time.

The TOT can provide the difference between UTC and local time for several geographical regions.

Tim e O ffset Table 0x0014

tab le ID 0x73


8

1


reserved 2

section length 12

descriptor

C RC 32 32

U TC tim e 40

reserved 4

descriptors loop length 12




Figure 6.5.4.2d Time Offset Table (TOT)


Slide Number 45Rev -, July 2001 Vol 6: Digital Video


6.5.5: Satellite Standards (DVB-S)

Figure 6.5.5a Typical MPEG 2 Encoded DVB Compliant Satellite Delivery System



MPEG 2video

encoder

MPEG 2audio

encoderMPEG 2

audioencoder

MPEG 2video

encoder

MPEG 2audio

encoderdata

encoder

programMUX

programMUX

MPEG 2audio

encoder

programMUX

transportMUX

Typical MPEG 2 Program Encoding, Program Mux and Transport Stream Mux Block Diagram




Figure 6.5.5b



MUXadaptation& energydispersal

outercoding(Reed

Solomon188/204)

innercoding

(convolu-tional code)

Qbasebandshapping

QPSKModulator

Functional Block Diagram of a DVB Compliant Satellite QPSK Modulator

I

convolut.interleaving

I = 12 bytes

BB

Interface& Sync

data

CK

clock & sync generator and rate control




Figure 6.5.5c



Functional Block Diagram of a DVB Compliant Satellite QPSK Demodulator

carrier & clock recovery

DEMUXadaptation& energydispersalremoval

outercoding

decoder(Reed

Solomon188/204)

innercoding

decoder(Viterbi)Q

MatchedFilter

QPSKDemod

I convolut.interleaving

I = 12 bytes

BB

Interface& Sync

data

U

Syncdecoder

clock & sync generatorcode rate control




Figure 6.5.5d


Slide Number 49Rev -, July 2001 Vol 6: Digital Video



Figure 6.5.5e Typical RF Transmit (Uplink) and Receiver (Downlink) Systems Used for Satellite Distribution



MUX Adaptation and Energy DispersalThe input of the DVB modulator will consist of the MPEG 2 transport stream. The DVB modulator will output a modulated or unmodulated carrier centered at 70 or 140 MHz.

The MPEG 2 transport stream will be organized in fixed length packets of 188 bytes including 1 synch word-byte (01000111 - 47 Hex).

To avoid the emission of an unmodulated carrier and to ensure adequate binary transitions, the data of the MPEG 2 transport stream must be randomized in a process shown in the next slide.

The randomization is required to comply with ITU Radio Regulations.


Part 5: Satellite Standards (DVB-S)

6.5.5.1: MUX Adaptation and Energy Dispersal



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

1 0 0 1 0 1 0 1 0 0 0 0 0 0 0In itia lization sequence

ex-orand

ex-or00000011...

Enable C lear/random izeddata input

Random ized/de-random ized

data output

Randomizer/de-random izer Diagram

PR BS G enerator

PR BS O /P Enable/D isable




Figure 6.5.5.1 Randomizer/de-randomizer Diagram



MUX Adaptation and Energy DispersalA Pseudo Random Binary Sequence (PRBS) generator is used in the randomizing/de-randomizing process. The polynomial for the PRBS generator shall be

1 + X14 + X15

A sequence of 1001010100000000 is inserted at the start of every eight transport packets.

The sync byte of the first packet of the group of eight is bit-wise inverted from 47 Hex to B8 Hex. This is done to provide an initialization signal for the descramblers . The process is referred to as the “Transport Multiplex Adaptation”.






MUX Adaptation and Energy DispersalThe generation of the PRBS sequence will continue during the transmission of the DVB transport packet but its output will be disabled. This will aid the synchronization of the bit stream.

The output of the PRBS generator will be activated when there are no bits being inputted in the modulator or if a non-compliant MPEG 2 stream is provided to the input of the modulator.

This is done so as to ensure that the modulator does not output a non-modulated carrier to the satellite.

The PRBS period has a length of 1503 bytes (7 x 188 bytes + 1 x 187).






Forward Error Correction (FEC)There are two process of forward error correction defined by the DVB standard for satellite operation:

Outer Coding: based on Reed Solomon code (188/204)

Inner Coding: punctured convolutional codes



6.5.5.2: Forward Error Correction (FEC)



Outer Coding (RS)The outer coding is intended to work with the MPEG 2 framing structure for a multiplexed transport stream. The MPEG 2 packet is composed of 187 bytes of data with 1 sync byte.

187 bytesSync1 byte

Packet from a M ultip lexed M PEG 2 Transport Stream

The randomized transport packet will resemble something like this:

R187 B

Sync8

Random ized Transport Packet

R187 B

Sync1

R187 B

Sync2

R187 B

Sync3

R187 B

Sync4

R187 B

Sync5

R187 B

Sync6

R187 B

Sync7

R187 B

Sync8

R187 B

Sync1

PRBS period = 1503 bytes




Figure 6.5.5.2a Packet from a Multiplexed MPEG 2 Transport Stream

Figure 6.5.5.2b Randomized Transport Packet



Outer Coding (RS)The Reed Solomon code RS (204,188, T=8) is applied to each randomized transport packet (188 bytes) to generate an error correction code at the packet level.

187 bytesSync1 byte

Error Pro tected Packet Using Reed Solom on Code RS (204,188,8)

RS (204,188,8)16 bytes

204 bytes

The new data stream is:

203Bytes

Sync8

203Bytes

Sync1

203Bytes

Sync2

203Bytes

Sync3

203Bytes

Sync4

203Bytes

Sync5

203Bytes

Sync6

203Bytes

Sync7

203Bytes

Sync8

203Bytes

Sync1




Figure 6.5.5.2c Error Protected Packet Using Reed Solomon Code RS (204, 188, 8)

Figure 6.5.5.2d New Data Stream



Inner CodingThe DVB standard states that a DVB compliant modulator or receiver will be support convolutional coding with code rates of 1/2, 2/3, 3/4, 5/6 and 7/8. Other rates can be used, but as a minimum these five rates must be implemented before a system is considered compliant to the DVB standard.

When trying to lock to a carrier, a receiver will try each of the code rate until it acquires lock.






Convolutional InterleavingThe convolutional interleaver is a set of shift registers with fixed delays. Convolutional interleaving is used in conjunction with the inner convolutional coding process.

Satellite induced errors tend to be bursty in nature, and Reed Solomon coding is not at its best when faced with bursts of errors. Convolutional interleaving is used to distribute the information in a given packet across multiple packets. If the resultant data stream in now subjected to a bursty error, the affected bits are then de-interleaved and the error is spread evenly over the entire data stream. The Reed Solomon algorithm can now treat these as dribble errors and correct for them.

The interleaver is specified by a maximum interleaving depth usually denoted by I. In a DVB compliant system, I is set to 12. To help the synchronization, all sync bytes are processed through the first path (path “0”) of the interleaver and de-interleaver.



6.5.5.3: Convolutional Interleaving



F unctiona l B lock D ia g ram o f a D V B C om plian t C o nvo lu tion a l In te rle ave r an d D e-in terle ave r

M =17B

2*M = 34B

3*M = 51B

4*M = 68 B

5*M = 85 Bytes

11*M = 187 Bytes

.

.

.

FIFO shift reg istors

C onvo lu lt ion a l In te rle ave r C on vo lu lt ion a l D e -in te rle ave r

M =17B

2*M = 34B

3*M = 51B

4*M = 68 B

5*M = 85 Bytes

11*M = 187 Bytes...

Sync W ord Route

Sync W ord Route

1 byte perposition

1 byte perposition




Figure 6.5.5.3a Functional Block Diagram of a DVB Compliant Convolutional Interleaver and De-Interleaver



203Bytes

Sync8

R ee d S o lom o n P acke t (204 by tes)

1

204 bytes

2 3 4 5 6 7 8 9 10 11 12

T w e lve C on secu tive P acke ts a t the Inpu t o f th e C on vo lu tiona l In te rlea ve r

204 bytes

Packet 1Byte 1 to 17

(Packe t 1 to 12)


(Packe t 1 to 12)


(Packet 1 to 12)


(Packe t 1 to 12)


(Packet 1 to 12)

Packet 12Byte 188 to 204(Packet 1 to 12)

. . .

T w e lve R esu lting P acke ts a t the O u tpu t o f the C onvo lu tiona l In te rleaver

204 bytes


(Packe t 1 to 12)


(Packe t 1 to 12)


(Packet 1 to 12)


(Packe t 1 to 12)


(Packet 1 to 12)

Packet 12Byte 188 to 204(Packet 1 to 12)

. . .

T w e lve P acke ts a t the Inpu t o f the C onvo lu tiona l D e -in te rleave r

1

204 bytes

2 3 4 5 6 7 8 9 10 11 12

T w e lve R esu lting P acke ts a t the O u tpu t o f the C onvo lu tiona l D e -in te rlea ve r




Figure 6.5.5.3b

Figure 6.5.5.3c

Figure 6.5.5.3d



Baseband Shaping and QPSK ModulationSatellite transmissions are notorious for distortions in phase and amplitude. Consequently, we have to use a modulation technique that is sturdy enough to survive these distortions.

The most used modulation technique is Quadrature Phase Shift Keying (QPSK). This mode of modulation is sometimes referred to as four phase shift keying (4-PSK).

In QPSK modulation, a cosine carrier is varied in phase while keeping a constant amplitude and frequency. Data signal are represented by the change in phase between two time periods.



6.5.5.4: Baseband Shaping and QPSK Modulation



I = 0Q = 0

I = 0Q = 1

I = 1Q = 1

I = 1Q = 0

+x-x

+y

-y

Baseband Shaping and QPSK ModulationThe data being transferred is represented as the combination of two amplitude modulated signals such that

s(t) = xcos(t) + ysin(t)

s(t) = I + Q signals

The two signals are phase offset by 90°.

Where a value of :

+x equals I = “0”, +y equals Q = “0”

-x equals I = “1”, -y equals Q = “1”




Figure 6.5.5.4a Baseband Shaping and QPSK Modulation



+x-x

+y

-y

As indicated previously, digital satellite transmission is subject to distortion in phase and amplitude.

A QPSK modulated system is more robust to these distortions. The following drawing shows a constellation of points that were recorded over time. Each point shows a displacement from its ideal phase/amplitude location.

Even with these slight distortions, however, we can still recognize the samples as one of the four states defined in QPSK modulation.




Figure 6.5.5.4b Baseband Shaping and QPSK Modulation

Baseband Shaping and QPSK Modulation



Modulation Inner Code Spectral Modem Note 1

Efficiency Implementation(bits/symbol) (dB) (dB)

QPSK 1/2 0.92 0.8 4.5QPSK 2/3 1.23 0.8 5.0QPSK 3/4 1.38 0.8 5.5QPSK 5/6 1.53 0.8 6.0QPSK 7/8 1.61 0.8 6.48PSK 2/3 1.84 1.0 6.98PSK 5/6 2.30 1.4 8.98PSK 8.9 (note 2) 2.46 1.5 9.416QAM 3/4 (note 2) 2.76 1.5 9.016QAM 7/8 3.22 2.1 10.7

Note 1: Required Eb/No for BER = 2x10-4 before RS and QEF after Reed Solomon



6.5.5.5: Performance Requirements



Performance Requirements Example of Bit Rates Versus Transponder Bandwidth

BW BW Rs Ru Ru Ru Ru Ru(at 3 dB) (at 1 dB) 1.28 1/2 2/3 3/4 5/6 7/8[MHz] [MHz] [Mbaud] [Mbps] [Mbps] [Mbps] [Mbps] Mbps]

54 48.6 42.2 38.9 51.8 58.3 64.8 68.046 41.4 35.9 33.1 44.2 49.7 55.2 58.040 36.0 31.2 28.8 38.4 43.2 48.0 50.436 32.4 28.1 25.9 34.6 38.9 43.2 45.433 29.7 25.8 23.8 31.7 35.6 39.6 41.630 27.0 23.4 21.6 28.8 32.4 36.0 37.827 24.3 21.1 19.4 25.9 29.2 32.4 34.026 23.4 20.3 18.7 25.0 28.1 31.2 32.8



6.5.5.5: Performance Requirements



Conditional Access (DVB-CA) Currently, any DVB compliant receiver or decoder can decode a DVB stream and display the content of its elementary stream. In the case of a broadcast program ANY DVB compliant receiver or decoder could have access to any video and audio program within the DVB stream.

This works well in most cases, but many broadcasters are concerned with copyright issues or distribution issues. In their view they cannot permit everyone to have access to their program while it is transmitted over satellite. To prevent unauthorized viewers from getting access to the program within a DVB stream, we have to add a Conditional Access (CA) system to the DVB stream at the encoding location. We can then use this CA system to control who has access to the content of the DVB stream.



6.5.6: Conditional Access (DVB-CA)



Conditional Access (DVB-CA)A conditional access system can be considered as having two parts: the decryption and the descrambling systems.

The decryption translates coded keys received by the IRDs that are necessary for the proper operation of the descrambling system.

The descrambler takes the coded keys to unscramble the video and audio programs within a DVB stream. In other words, the descrambler is used to make the receive pictures and sound intelligible. This is done based on information provided by the decryption system.

Standardization of the CA system has been deemed undesirable, since a single common CA standard is more vulnerable to hacking, which could mean loss of revenue to many broadcasters.






Conditional Access (DVB-CA)CA technology has, in the past, worked in a closed manner. Each manufacturer used its own structures and rules for its CA system. Information on CA systems were seldom shared between companies.

After many discussions within the DVB group, it was decided to propose the following CA standards and recommendations:

SimulCrypt

MultiCrypt

General CA Measures and Recommendations






SimulCrypt A Common Scrambling Algorithm allows the same program (with different embedded CA bitstreams) to be viewed on several receivers with different CA systems.

The DVB stream would be used to carry multiple CA messages required to enable the scrambled program within the different receivers.

The DVB SimulCrypt system is based on the concept of shared scrambling and descrambling methods


Part 6: Conditional Access (DVB-CA)

6.5.6.1: SimulCrypt




6.5.6.1: SimulCrypt

Figure 6.5.6.1 SimulCrypt System Architecture



SimulCryptEvent Information Scheduler (EIS) - Provides the necessary

information to the DVB table to update the EIT table (SI Generator). It also provides information to the ECMG regarding changes in CA for different programs within a PES.

SimulCrypt Synchronizer (SCS) - Acquires the control words (CW) from the CWG. Supplies the CW to the ECMGs. Acquires ECMs from the ECMGs. Synchronizes ECMs with their associated Crypto Period (CP). Submit ECM to the MUX. Supplies CW to the scrambler for the duration of the CP.

Entitlement Control Message Generator (ECMG) - Generates ECMs based on CWs received from the SCS.



6.5.6.1: SimulCrypt



SimulCryptEntitlement Management Message Generator (EMMG) - The

EMMG is supplied by the manufacturer. The EMMG initiates connections to the MUX.

Private Data Generator (PDG) - The PDG is similar to the EMMG but is used to carry other CA related private data.

Custom Service Information Generator (SIG) - Generates private service information (SI). It interfaces with the SI and PSI generators.

Multiplex Configuration (MUX Config) - As the name implies, this interface is used to configure the multiplexor.



6.5.6.1: SimulCrypt



SimulCryptSI Generator - Generates the Service Information Tables (SIT).

It takes information from the EIS and the Custom SI servers supplied by the CA providers.

Program Specific Information (PSI) Generator - Generates the Program Specific Information for the system.

Multiplexer (MUX) - Multiplexes the program transport streams, plus SI tables, PSI tables and CA information (EMMs, SCS)

Scrambler (SCR) - Specification for the common scrambling system is not available. The information is considered confidential and its access is limited by the ETSI.

Control Word Generator (CWG) - for security reason the CWG definition is not available.



6.5.6.1: SimulCrypt



MultiCryptThe MultiCrypt standard defines a common interface between a standard PCMCIA module and a DVB receiver.

The PCMCIA card is used as a smart card or a CA reader that can be inserted in a DVB compliant receiver for CA descrambling. The smart card is configured to operate with a known CA system.

To descramble a DVB compliant signal, the user must find the appropriate smart card compatible with the CA system used. The common interface allows a user to use the same receiver to receive different signals that have been scrambled using different CA system. It is only necessary to have the appropriate smart card for each CA system.



6.5.6.2: MultiCrypt




6.5.6.2: MultiCrypt

Figure 6.5.6.2a DVB Receiver Using Common Interface for CA (DVB-CI)

MultiCrypt



DVB Measures and Recommendations • Code of conduct for access to digital decoders

• Recommendations for anti-piracy legislation for digital video broadcasting

• Licensing of CA systems to manufacturers should be on fair and reasonable terms and should not exclude the common interface

• CA systems should allow simple transcontrol. Cable operators should be able to remove CA used for satellite and terrestrial distribution and the add their own CA data



6.5.6.3: DVB Measures and Recommendations



DVB Interfaces The DVB group has defined the following three interface standards:

ASI Asynchronous Serial Interface

SPI Synchronous Parallel Interface

SSI Synchronous Serial Interface

Of the three interfaces, ASI is the one currently being used by the industry.



6.5.7: DVB Interface



DVB InterfacesASI Asynchronous Serial Interface

75 ohm BNC connector270 MbpsUni-directional transmission link

SPI Synchronous Parallel Interface25 D type connectorTwo version of SPI specification

• LVDS (Low Voltage Differential Signaling)- use low voltage swing of about 350 mV- ANSI/TIA/EIA-644

• Parallel Emitter Coupled Logic (ECL)SSI Synchronous Serial Interface

SMPTE 310M



6.5.7: DVB Interface



Other DVB StandardsThis presentation is intended to cover satellite distribution. A short description of the DVB standard for cable distribution and digital terrestrial television will be provided in this section. Further information on these distribution methods can be obtained from the following DVB standards

• EN 300 429 Framing Structure, Channel Coding, and Modulation for Cable Services

• EN 300 744 Framing Structure, Channel Coding, and Modulation for Digital Terrestrial Television



6.5.8: Other DVB Standards



DVB Standards for Cable Services This standard is similar to the one proposed for the DVB-S services. Cable service does not use QPSK modulation as it is better served by using 16QAM, 32QAM, 64QAM, 128QAM or 256QAM.

Useful Ru Total Ru Cable Occupied Modulation

(w RS) Symbol Rate BW Scheme[Mbps] [Mbps] [Mbaud] [MHz]

38.1 41.34 6.89 7.92 64 QAM31.9 34.61 6.92 7.96 32 QAM25.2 27.34 6.84 7.86 16 QAM18.9 20.52 3.42 3.93 64 QAM16.0 17.40 3.48 4.00 32 QAM12.8 13.92 3.48 4.00 16 QAM9.6 10.44 1.74 2.00 64 QAM8.0 8.70 1.74 2.00 32 QAM6.4 6.96 1.74 2.00 16 QAMVol 6: Digital Video, Sec 5: Digital Video Broadcasting

Part 8: Other DVB Standards

6.5.8.1: DVB Standard for Cable Services (DVB-C)



MUXadaptation& random iz

ation

outercoding(Reed

Solom on188/204)

differencia lencoding

basebandshapping

QAMm odulator

C on cep tu a l B lo ck D ia g ram o f C a b le H ead -en d

convolut.interleaving

I = 12 bytes

BB

Interface& Sync

data

CK

clock & sync generator and rate contro l

Byte to m -tuple

conversion Q

I

C oncep tua l B lo ck D ia gra m o f C a b le IR D

carrier, clock and sync recovery

energydispersalrem oval

outerdecoding

(ReedSolom on188/204)

differencialdecoding

m atchedfilter

&equalizer

QAMdem od

convolut.de-

interleaving

I = 12 bytes

BB

Interface& Sync

data

CK

sym bol tobyte

m appingQ

I



6.5.8.1: DVB Standard for Cable Services (DVB-C)

Figure 6.5.8.1a Conceptual Block Diagram of Cable Head-end

Figure 6.5.8.1b Conceptual Block Diagram of Cable IRD



DVB Standards for Digital Terrestrial Television The standard for digital terrestrial television, DVB-S and DVB-C share a common platform. The changes between the three standards are usually only those required to deal with the different medium used to distribute the signal.

DVB-S has to deal with interference from analog and digital signals transmitted to/from neighboring transponders or satellites. Satellite receivers are also affected by bursty noise caused by local RF interference.

DVB-C defines operation in a closed environment where the only problems are loss due to the cable run and distortion due to the medium. Both problems are usually reduced by the addition of equalizers and amplifiers in the network. The cable distribution usually has to deal with a fixed medium with limited bandwidth.



6.5.8.2: DVB Standard for Digital Terrestrial Television (DVB-T)



DVB Standards for Digital Terrestrial TelevisionFor digital terrestrial television, we have to share the UHF frequency band with other analog transmission. Any digital transmission in this frequency band will be subject to a high level of co-channel interference (CCI) and adjacent channel interference (ACI) from NTSC/PAL/SECAM analog services.

The DVB standard defines the use of an OFDM (Orthogonal Frequency Division Multiplexing) system with concatenated error correcting coding.

You can find more information on this standard by referring to EN 300 744 V1.1.2 (1997-08).



6.5.8.2: DVB Standard for Digital Terrestrial Television



DVB Transport Tests The DVB group has defined three levels of potential errors:

Priority 1 Priority 2 Priority 3TS sync Transport NIT

Sync Byte CRC SI Repetition Rate

PAT PCR Buffer

Continuity PCR Accuracy SDT

PMT CAT EIT

PID RST

TDT



6.5.9: DVB Transport Test

Date post:	09-Apr-2017
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