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ETSI TS 101 191 V1.3.1 (2001-01)
Technical Specification
Digital Video Broadcasting (DVB);
DVB mega-frame for Single Frequency Network (SFN)
synchronization
European Broadcasting Union Union Européenne de Radio-Télévision
EBU·UER
ETSI
2 ETSI TS 101 191 V1.3.1 (2001-01)
Reference
RTS/JTC-DVB-93
Keywords
Broadcasting, digital, video, DVB, TV
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© European Telecommunications Standards Institute 2001.
© European Broadcasting Union 2001.
All rights reserved.
ETSI
3 ETSI TS 101 191 V1.3.1 (2001-01)
Contents
Intellectual Property Rights ..........................................................................................................................4
Foreword.....................................................................................................................................................4
1 Scope.................................................................................................................................................5
2 References .........................................................................................................................................5
3 Definition and abbreviations ...............................................................................................................5
3.1 Definitions ................................................................................................................................................. 5
3.2 Abbreviations............................................................................................................................................. 5
4 General description............................................................................................................................6
4.1 SFN system blocks ..................................................................................................................................... 7
5 Mega-frame definition ........................................................................................................................8
6 Mega-frame Initialization Packet (MIP) ..............................................................................................9
6.1 Functions ................................................................................................................................................. 12
6.1.1 Transmitter time offset function ........................................................................................................... 12
6.1.2 Transmitter frequency offset function................................................................................................... 13
6.1.3 Transmitter power function .................................................................................................................. 13
6.1.4 Private data function ............................................................................................................................ 13
6.1.5 Cell id function ................................................................................................................................... 14
6.1.6 Enable function................................................................................................................................... 14
Annex A (normative): CRC decoder model...................................................................................15
Annex B (normative): Functional description of SFN synchronization........................................16
Annex C (normative): Reconfiguration of DVB-T modulator parameters by using the MIP......17
History ......................................................................................................................................................18
ETSI
4 ETSI TS 101 191 V1.3.1 (2001-01)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://www.etsi.org/ipr).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This Technical Specification (TS) has been produced by Joint Technical Committee (JTC) Broadcast of the European
Broadcasting Union (EBU), Comité Européen de Normalization ELECtrotechnique (CENELEC) and the European
Telecommunications Standards Institute (ETSI) (Broadcast).
NOTE: The EBU/ETSI JTC Broadcast was established in 1990 to co-ordinate the drafting of standards in the
specific field of broadcasting and related fields. Since 1995 the JTC Broadcast became a tripartite body
by including in the Memorandum of Understanding also CENELEC, which is responsible for the
standardization of radio and television receivers. The EBU is a professional association of broadcasting
organizations whose work includes the co-ordination of its members' activities in the technical, legal,
programme-making and programme-exchange domains. The EBU has active members in about 60
countries in the European broadcasting area; its headquarters is in Geneva.
European Broadcasting Union
CH-1218 GRAND SACONNEX (Geneva)
Switzerland
Tel: +41 22 717 21 11
Fax: +41 22 717 24 81
Digital Video Broadcasting (DVB) Project
Founded in September 1993, the DVB Project is a market-led consortium of public and private sector organizations in
the television industry. Its aim is to establish the framework for the introduction of MPEG-2 based digital television
services. Now comprising over 200 organizations from more than 25 countries around the world, DVB fosters
market-led systems, which meet the real needs, and economic circumstances, of the consumer electronics and the
broadcast industry.
ETSI
5 ETSI TS 101 191 V1.3.1 (2001-01)
1 Scope
The present document specifies a mega-frame, including a mega-frame initialization packet (MIP), which may be used
for synchronization of the Single Frequency Networks (SFN) as well as for the optional control of other important
parameters in an SFN.
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
• References are either specific (identified by date of publication and/or edition number or version number) or
non-specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies.
[1] ISO/IEC 13818-1 (1994): "Information Technology - Generic coding of moving pictures and
associated audio information: Systems".
[2] ETSI EN 300 744: "Digital Video Broadcasting (DVB); Framing structure, channel coding and
modulation for digital terrestrial television".
[3] ETSI EN 300 468: "Digital Video Broadcasting (DVB); Specification for Service Information (SI)
in DVB systems".
3 Definition and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
cell: for the definition of a cell, see EN 300 468 [3], clause 3.1
frame: for the definition of a DVB-T frame, see EN 300 744 [2], clause 4.4
super-frame: for the definition of a DVB-T super-frame, see EN 300 744 [2], clause 4.4
3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
CRC Cyclic Redundancy Check
DVB Digital Video Broadcasting
DVB-T DVB-Terrestrial
ERP Effective Radiated Power
GPS Global Positioning System
HP High Priority
LP Low Priority
MFN Multi Frequency Network
MFP Mega-Frame Packet
MIP Mega-frame Initialization Packet
MPEG Moving Pictures Expert Group
PID Packet IDentifier
pps pulse per second
ETSI
6 ETSI TS 101 191 V1.3.1 (2001-01)
RF Radio Frequency
RS Reed-Solomon
SFN Single Frequency Network
SI Service Information
STS Synchronization Time Stamp
SYNC SYNChronization
TPH Transport Packet Header
TPS Transport Parameter Signalling
TS Transport Stream
TX/RX Transmitter/Receiver
4 General description
Figure 1 shows a block diagram of a complete SFN system.
MPEG-2
remultiplexer
SFN
adapter
MPEG-2
TS
TX
Network
adapter
Distribution
Network
RX
Network
adapter
RX
Network
adapter
GPS (note)
10 MHz 1 pps
DVB-T
modulator
SYNC
system
GPS (note)
10 MHz 1 pps
DVB-T
modulator
SYNC
system
GPS (note)
10 MHz 1 pps
MPEG-2
TS
MPEG-2
TS
NOTE: Could be any common available frequency reference.
Figure 1: DVB-T primary distribution with SFN adaptation
The SFN functionality is an extension to the DVB system. The blocks associated with SFN functionality are the grey
boxes in figure 1. These blocks could be implemented either as separate equipment or integrated in the multiplexer
and/or the DVB-T modulator.
ETSI
7 ETSI TS 101 191 V1.3.1 (2001-01)
4.1 SFN system blocks
MPEG-2 re-multiplexer
The MPEG-2 re-multiplexer re-multiplexes the programmes from various input channels, updates the SI and provides
an MPEG-2 TS which, after SFN adaptation, is transmitted via the DVB-T modulators in the SFN.
SFN adapter
The SFN adapter forms a mega-frame, consisting of n TS-packets corresponding to 8 DVB-T frames in the 8K mode or
32 frames in the 2K mode, and inserts a Mega-frame Initialization Packet (MIP) with a dedicated PID value. Inserted
anywhere within a mega-frame of index M, the MIP of that mega-frame, MIPM, allows to uniquely identify the starting
point (i.e. the first packet) of the mega-frame M + 1. This is accomplished by using a pointer carried by the MIPM itself
to indicate its position with regards to the start of the mega-frame M + 1.
The time difference between the latest pulse of the "one-pulse-per-second" reference, derived e.g. from GPS, that
precedes the start of the mega-frame M + 1 and the actual start (i.e. first bit of first packet) of this mega-frame M + 1 is
copied into the MIP
M
. This parameter is called Synchronization Time Stamp (STS).
The time duration of a mega-frame is independent of the duration T
u, constellation and code rate of the DVB-T signal.
Four different time durations exist, for each type of channel width, depending on the chosen guard interval proportion,
as shown table 1a:
Table 1a
Guard Interval Channel width
(Δ/Tu) 6 MHz 7 MHz 8MHz
1/4 0,812 373 0,696 320 0,609 280
1/8 0,731 136 0,626 688 0,548 352
1/16 0,690 517 0,591 872 0,517 888
1/32 0,670 208 0,574 464 0,502 656
The output of the SFN adapter shall be fully DVB/MPEG-2 TS compliant.
Transmitter/Receiver network adapter
The network adapters shall provide a transparent link for the MPEG-2 TS from the central to the local units. The
maximum network delay - caused by the different paths of the transmission network - the SYNC system can handle is
1 second.
SYNC system
The SYNC system will provide a propagation time compensation by comparing the inserted STS with the local time
reference and calculate the extra delay needed for SFN synchronization. See annex B for an example of the
synchronization process.
DVB-T modulator
The modulator should provide a fixed delay from the input to the air interface. The information inserted in the MIP
could be used for the direct control of the modulator modes or control of other transmitter parameters. The modulator
clocks at the different sites have to be synchronized. Since it is a requirement of an SFN that all transmitted signals be
identical, the MPEG-2 TS inputs to the various DVB-T modulators have to be bit identical.
Global Positioning System (GPS)
GPS is one among many possible time references but it is the only one available globally. GPS receivers are available
which provide both a 10 MHz frequency reference and a 1 pulse per second (1 pps) time reference. The 1 pps time
reference, used in SFN synchronization, is divided into 100 ns steps of the 10 MHz clock. The 10 MHz system clock is
assumed to be available at all nodes in the network.
The functional blocks "SFN adapter" and "SYNC system" are additional elements for SFN use, and not necessary in
MFN applications.
ETSI
8 ETSI TS 101 191 V1.3.1 (2001-01)
5 Mega-frame definition
The output of the SFN adapter shall be a valid MPEG-2 TS, where the individual packets are organized in groups,
which constitute a mega-frame. Each mega-frame consists of n packets, where n is an integer number which depends on
the number of RS-packets per super-frame in the DVB-T mode that will be used for DVB-T emission of the
MPEG-2 TS (see EN 300 744 [2], clause 4.7). In the 8K mode n is (the number of RS-packets per super-frame) × 2. In
the 2K mode n is (the number of RS-packets per super-frame) × 8.
Each mega-frame contains exactly one Mega-frame Initialization Packet (MIP). The actual position may vary in an
arbitrary way from mega-frame to mega-frame. The pointer value in the MIP is used to indicate the start of the
following mega-frame. In figure 2 the overall structure of the mega-frame, including the positioning of the MIP, is
given. The exact definition of the MIP format is given in clause 6.
First Packet MIP Last Packet
MFP #0 MFP #1 ….. MFP #p ….. MFP #n-1 MFP #0
Pointer = (n-1) - p
The pointer indicates the location
of the first packet of the next
mega-frame.
Mega-frame
Figure 2: Overall mega-frame structure
The start of a mega-frame in the DVB-T signal is in the present document defined to coincide with the beginning of a
DVB-T super-frame and the start of an inverted sync byte, being part of transport multiplex adaptation.
The use of a mega-frame and the insertion of a MIP are additional elements for SFN use, and not necessary in MFN
applications.
ETSI
9 ETSI TS 101 191 V1.3.1 (2001-01)
6 Mega-frame Initialization Packet (MIP)
The MIP is an MPEG-2 compliant Transport Stream (TS) packet, made up of a 4-byte header and a 184-byte data field.
The organization of the MIP is shown in table 1b.
Table 1b: Mega-frame Initialization Packet (MIP)
Syntax Number of bits Identifier
mega-frame_initialization_packet(){
transport_packet_header 32 bslbf
synchronization_id 8 uimsbf
section_length 8 uimsbf
pointer 16 uimsbf
periodic_flag 1 bslbf
future_use 15 bslbf
synchronization_time_stamp 24 uimsbf
maximum_delay 24 uimsbf
tps_mip 32 bsblf
individual_addressing_length 8 uimsbf
for (i=0;i<N;i++){
tx_identifier 16 uimsbf
function_loop_length
for(i=0;i<N;i++){
function()
}
}
8 uimsbf
crc_32 32 rpchof
for (i=0, i<N,i++){
stuffing_byte
}
}
8 uimsbf
NOTE 1: Optional parameters are shown in italic.
NOTE 2: All parameter values in the MIPM apply to mega-frame M + 1, i.e. to the mega-frame pointed out by the pointer,
except for the tps_mip which describes the parameters of mega-frame M + 2. See annex C for details.
NOTE 3: For the definition of the CRC decoder model, see annex A.
NOTE 4: The length of a MIP shall always be 188 bytes.
transport_packet_header: The transport_packet_header shall comply with ISO/IEC 13818-1 [1] clause 2.4.3.2,
tables 2 and 3.
The PID value for the Mega-frame initialization Packet (MIP) shall be 0 x 15.
The payload_unit_start_indicator is not used by the SFN synchronization function and shall be set to 1.
The transport_priority value is not used by the SFN synchronization function and shall be set to 1.
The transport_scrambling_control value shall be set to 00 (not scrambled).
The adaptation_field_control value shall be set to 01 (payload only).
All other parameters are according to ISO/IEC 13818-1 [1] clause 2.4.3.2.
The Transport Packet Header (TPH) is mandatory.
Mandatory SFN parameters
synchronization_id: the synchronization_id is used to identify the synchronization scheme used (see table 2).
Table 2: Signalling format for the synchronization_id
Synchronization_id Function
0 x 00 SFN synchronization
0 x 01 - 0 x FF Future use
ETSI
10 ETSI TS 101 191 V1.3.1 (2001-01)
section_length: the section_length specifies the number of bytes following immediately after the section_length field
until, and including, the last byte of the crc_32 but not including any stuffing_byte. The section_length shall not exceed
182 bytes.
pointer: the pointer is a 2-byte binary integer indicating the number of transport packets between the MIP and the first
packet of the succeeding mega-frame.
The range of the pointer depends on the DVB-T mode used for emission.
periodic_flag: indicates if a periodic or an aperiodic insertion of the MIP is performed. Periodic insertion means that
the value of the pointer is not time varying. A "0" indicates aperiodic mode and a "1" indicates periodic mode. All SFN
"SYNC systems" shall be able to handle both aperiodic and periodic mode.
future_use: reserved for future use.
synchronization_time_stamp: the synchronization_time_stamp of MIPM contains the time difference, expressed as a
number of 100 ns steps, between the latest pulse of the "one-pulse-per-second" reference (derived e.g. from GPS) that
precedes the start of the mega-frame M + 1 and the actual start (i.e. beginning of first bit of first packet) of this
mega-frame M + 1.
maximum_delay: the maximum_delay contains the time difference between the time of emission of the start of megaframe
M+ 1 of the DVB-T signal from the transmitting antenna and the start of mega-frame M + 1 at the SFN adapter,
as expressed by the value of its synchronization_time_stamp in the MIPM. The value of maximum_delay shall be larger
than the sum of the longest delay in the primary distribution network and the delays in modulators, power transmitters
and antenna feeders. The unit is 100 ns and the range of maximum_delay is 0 x 000000 - 0 x 98967F, this equals a
maximum delay of 1 second.
tps_mip: the tps_mip consists of 32 bits, P
0
-P
31
. The relationship between the TPS as defined in EN 300 744 [2] and
tps_mip as defined in the present document is described in table 3.
ETSI
11 ETSI TS 101 191 V1.3.1 (2001-01)
Table 3: Relationship between TPS (as defined in EN 300 744 [2]) and tps_mip
(as defined in the present document)
Bit number (TPS) Format Purpose/Content Bit number (tps_mip)
s
0
see clause 4.6.2.1,
EN 300 744 [2]
Initialization Not used
s
1
- s
16
0011010111101110 or
1100101000010001
Synchronization word Not used
s
17
- s
22
see clause 4.6.2.3,
EN 300 744 [2]
Length indicator Not used
s
23
, s
24
see table 12,
EN 300 744 [2]
Frame number Not used
s
25
, s
26
see table 13,
EN 300 744 [2]
Constellation P
0,
P
1
s
27
, s
28
, s
29
see table 14,
EN 300 744 [2]
Hierarchy information P
2
,P
3
,P
4
s
30
, s
31
, s
32
see table 15,
EN 300 744 [2]
Code rate, HP stream P
5
,P
6
,P
7
s
33
, s
34
, s
35
see table 15,
EN 300 744 [2]
Code rate, LP stream P
5
,P
6
,P
7
s
36
, s
37
see table 16,
EN 300 744 [2]
Guard interval P
8,
P
9
s
38
, s
39
see table 17,
EN 300 744 [2]
Transmission mode P
10
,P
11
s
40
- s
47
see table 18,
EN 300 744 [2]
Cell identifier Not used
s48 - s
53
all set to "0" Reserved for future use P
15
- P
31
s54 - s67 BCH code Error protection Not used
- see table 4: "Signalling
format for the bandwidth"
Bandwidth of the RF channel P
12
,P
13
- see table 5: "Signalling
format for the bit stream
priority"
The priority of the transport stream P
14
NOTE: There are 17 bits allocated for future use in tps_mip, whereas there are 6 bits allocated in the TPS of
EN 300 744 [2].
Table 4: Signalling format for the bandwidth
Bits P
12
, P
13
Bandwidth
00 7 MHz
01 8 MHz
10 6 MHz
11 reserved for future use
Table 5: Signalling format for the bit stream priority
Bit P
14
Transmission mode
0 Low Priority TS
1 High Priority TS
P
0
-P
13
: in case of inconsistent values of P
0
-P
13
for the High Priority and Low Priority Transport Streams, the HP value is
valid. In case of change of DVB-T mode, see annex C for the time relationship between P
0
-P
13
and the TPS data of the
DVB-T signal.
individual_addressing_length: the individual_addressing_length field gives the total length of the individual
addressing field in bytes. If individual addressing of transmitters is not performed the field value is 0 x 00, indicating
that the crc_32 immediately follows the individual_addressing_length.
crc_32: this 32 bit crc_32 field contains the CRC value that gives a zero output of the registers in the decoder defined in
annex A of the present document, after processing all of the bytes in theMIP, excluding the stuffing bytes.
ETSI
12 ETSI TS 101 191 V1.3.1 (2001-01)
stuffing_byte: every stuffing_byte has the value 0 x FF.
Optional MIP section parameters
tx_identifier: the tx_identifier is a 16-bit word used to address an individual transmitter. The tx_identifier value
0 x 0000 is used as a broadcast address to address all transmitters in the network.
function_loop_length: the function_loop_length field gives the total length of the function loop field in bytes.
function: the functions are described in clause 6.1.
6.1 Functions
Parameters common to all functions:
function_tag: The function_tag specifies the function identification.
function_length: The function_length field gives the total length of the function field in bytes.
Table 6 gives the function_tag value for the functions defined in the present document. All functions are optional and
similar commands could be sent via a separate management network.
Table 6: Tag value of functions
Function function_tag value
tx_time_offset_function 0 x 00
tx_frequency_offset_function 0 x 01
tx_power_function 0 x 02
private_data_function 0 x 03
cell_id_function 0 x 04
enable_function 0 x 05
Future_use 0 x 06 - 0 x FF
6.1.1 Transmitter time offset function
The tx_time_offset_function is used to apply a deliberate offset in time of the transmitted DVB-T signal, relative to the
reference transmission time (STS + maximum_delay) modulo 107.
Table 7: Function transmitter time offset
Syntax Number of bits Identifier
tx_time_offset_function(){
function_tag 8 uimsbf
function_length 8 uimsbf
time_offset 16 tcimsbf
}
time_offset: The deliberate time offset of the mega-frames. The unit is 100 ns. The range is [-32 768,32 767] × 100 ns.
NOTE: The use of the complete range is not foreseen.
ETSI
13 ETSI TS 101 191 V1.3.1 (2001-01)
6.1.2 Transmitter frequency offset function
The tx_frequency_offset_function is used to apply a deliberate frequency offset of the centre frequency of the emitted
DVB-T signal relative to the centre frequency of the RF channel.
Table 8: Function transmitter frequency offset
Syntax Number of bits Identifier
tx_frequency_offset_function(){
function_tag 8 uimsbf
function_length 8 uimsbf
frequency_offset 24 tcimsbf
}
frequency_offset: The deliberate frequency offset relative to the centre frequency of the RF channel in use. The unit is
1 Hz. The range is [-8 388 608,8 388 607] × 1 Hz.
NOTE: The use of the complete range is not foreseen.
6.1.3 Transmitter power function
The tx_power_function can be used to configure the transmitter ERP.
Table 9: Function transmitter power
Syntax Number of bits Identifier
tx_power_function (){
function_tag 8 uimsbf
function_length 8 uimsbf
power 16 uimsbf
}
power: The power of the transmitter is defined as the ERP. The unit is 0,1 dB. The range is ([0,655 35] × 0,1) dBm.
NOTE: The use of the complete range is not foreseen.
6.1.4 Private data function
The private_data_function is used to send private data to the transmitters via the MIP.
Table 10: Function private data
Syntax Number of bits Identifier
private_data_function(){
function_tag 8 uimsbf
function_length 8 uimsbf
for (i=0;i<N;i++){
private_data 8 bsblf
}
}
private_data: The private data can be used for proprietary functions.
ETSI
14 ETSI TS 101 191 V1.3.1 (2001-01)
6.1.5 Cell id function
The cell_id_function can be used to configure the cell identifier of the transmitter.
Table 11: Function cell id
Syntax No. of bits Identifier
cell_id_function(){
function_tag 8 uimsbf
function_length 8 uimsbf
cell_id 16 uimsbf
wait for_enable_flag 1 bslbf
reserved_future_use 7 bslbf
}
cell_id: The cell_id [3] is used to uniquely identify the cell to which the transmitter belongs to.
wait_for_enable_flag: If this flag is set to "0" then the cell_id within the cell_id_function has to be inserted
immediately. If this flag is set to "1" then the cell_id within the cell_id_function has to be inserted immediately after
having received the corresponding enable_function.
6.1.6 Enable function
The enable_function can be used to execute the change of parameters provided by means of other MIP functions before.
Table 12: Function enable
Syntax No. of bits Identifier
enable_function(){
function_tag 8 uimsbf
function_length 8 uimsbf
for (i=0;i<N;i++=){
enabled_function_tag 8 uimsbf
}
}
enabled_function_tag: This 8-bit field indicates the function that is enabled by means of the enable_function. The
coding is according to table 6.
ETSI
15 ETSI TS 101 191 V1.3.1 (2001-01)
Annex A (normative):
CRC decoder model
The 32-bit CRC decoder is specified in figure A.1.
Figure A.1: 32-bit CRC decoder model
The 32 bit CRC decoder operates at bit level and consists of 14 adders + and 32 delay elements z (i). The input of the
CRC decoder is added to the output of z (31), and the result is provided to the input z (0) and to one of the inputs of
each remaining adder. The other input of each remaining adder is the output of z (i), while the output of each remaining
adder is connected to the input of z (i + 1), with i = 0, 1, 3, 4, 6, 7, 9, 10, 11, 15, 21, 22, and 25 (see figure A.1).
This is the CRC calculated with the polynomial:
x32 + x26 + x23 + x22 + x16 + x12 + x11 + x10 + x8 + x7 + x5 + x4 + x2 + x + 1
Before the CRC processing of the data of a MIP the output of each delay element z (i) is set to its initial value "1". After
this initialization, each byte of the MIP is provided to the input of the CRC decoder, including the four crc_32 bytes, but
excluding any stuffing byte. Each byte is shifted into the CRC decoder one bit at a time, with the most significant bit
(msb) first, i.e. from the TS packet sync byte 0 x 47 (0100 0111) first a "0" enter the CRC decoder, followed by a "1".
After shifting the last bit of the last crc_32 byte into the decoder, i.e. into z (0) after the addition with the output of
z (31), the output of all delay elements z (i) is read. In case of no errors, each of the outputs of z (i) has to be zero. At
the CRC encoder the crc_32 field is encoded with such value that this is ensured.
ETSI
16 ETSI TS 101 191 V1.3.1 (2001-01)
Annex B (normative):
Functional description of SFN synchronization
Ttransmitted
Transmitted Mega-frame
STS
1 second
Trec
maximum_delay
Tdelay
1 second
Transmission of first
Transport Packet of Megaframe
Received Mega-frame
NOTE: All values are in 100 ns (10 MHz clock)
Ttransmitted = (STS + maximum_delay) modulo 107 (from transmitter)
Tdelay = (STS + maximum_delay - Trec) modulo 107
Figure B.1
ETSI
17 ETSI TS 101 191 V1.3.1 (2001-01)
Annex C (normative):
Reconfiguration of DVB-T modulator parameters by using
the MIP
The tps_mip bits P
0
-P
14
, inserted in the MIP at the multiplexer, are used to reconfigure the parameters of the DVB-T
modulator. The bits P
0
-P
11
are also transmitted as the TPS bits s
25
- s
39
of the DVB-T signal, as information to the
receiver. In EN 300 744 [2], it is stated that the TPS information transmitted in super-frame m' bits s
25
- s
39
always apply
to super-frame m' + 1, whereas all other bits refer to super-frame m'. In order to define a non-ambiguous switch time the
following shall apply: Inserted in the MIP being sent in mega-frame 1, the tps_mip describes the parameters of
mega-frame 3. The DVB-T modulator will thus be able:
- first to update the data carried by its TPS carriers at the start of the last (i.e. the second in the 8K mode, and the
8th in the 2K mode) super frame of mega-frame 2;
- then to update its new configuration at the start of mega-frame 3.
time
Multiplexer
Mega-frame 1
Super-frame
SF1 SF2 SF1 SF2 SF1 SF2
Mega-frame 2 Mega-frame 3
Transmitter
Mega-frame 1
Super-frame
SF1 SF2 SF1 SF2 SF1 SF2
Mega-frame 2 Mega-frame 3
MIP containing
changed tps_mip
Pointer
New TPS data inserted in
the DVB-T super-frame
The new configuration of the
DVB-T modulator is executed at
the start of mega-frame 3
New TS bit rate according
to new tps_mip data.
Figure C.1: Reconfiguration of DVB-T modulator parameters by using the MIP
ETSI
18 ETSI TS 101 191 V1.3.1 (2001-01)
History
Document history
V1.1.1 February 1999 Withdrawn
V1.2.1 April 1998 Publication
V1.3.1 January 2001 Publication
ETSI TS 101 191 V1.3.1 (2001-01)
Technical Specification
Digital Video Broadcasting (DVB);
DVB mega-frame for Single Frequency Network (SFN)
synchronization
European Broadcasting Union Union Européenne de Radio-Télévision
EBU·UER
ETSI
2 ETSI TS 101 191 V1.3.1 (2001-01)
Reference
RTS/JTC-DVB-93
Keywords
Broadcasting, digital, video, DVB, TV
ETSI
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© European Broadcasting Union 2001.
All rights reserved.
ETSI
3 ETSI TS 101 191 V1.3.1 (2001-01)
Contents
Intellectual Property Rights ..........................................................................................................................4
Foreword.....................................................................................................................................................4
1 Scope.................................................................................................................................................5
2 References .........................................................................................................................................5
3 Definition and abbreviations ...............................................................................................................5
3.1 Definitions ................................................................................................................................................. 5
3.2 Abbreviations............................................................................................................................................. 5
4 General description............................................................................................................................6
4.1 SFN system blocks ..................................................................................................................................... 7
5 Mega-frame definition ........................................................................................................................8
6 Mega-frame Initialization Packet (MIP) ..............................................................................................9
6.1 Functions ................................................................................................................................................. 12
6.1.1 Transmitter time offset function ........................................................................................................... 12
6.1.2 Transmitter frequency offset function................................................................................................... 13
6.1.3 Transmitter power function .................................................................................................................. 13
6.1.4 Private data function ............................................................................................................................ 13
6.1.5 Cell id function ................................................................................................................................... 14
6.1.6 Enable function................................................................................................................................... 14
Annex A (normative): CRC decoder model...................................................................................15
Annex B (normative): Functional description of SFN synchronization........................................16
Annex C (normative): Reconfiguration of DVB-T modulator parameters by using the MIP......17
History ......................................................................................................................................................18
ETSI
4 ETSI TS 101 191 V1.3.1 (2001-01)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://www.etsi.org/ipr).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This Technical Specification (TS) has been produced by Joint Technical Committee (JTC) Broadcast of the European
Broadcasting Union (EBU), Comité Européen de Normalization ELECtrotechnique (CENELEC) and the European
Telecommunications Standards Institute (ETSI) (Broadcast).
NOTE: The EBU/ETSI JTC Broadcast was established in 1990 to co-ordinate the drafting of standards in the
specific field of broadcasting and related fields. Since 1995 the JTC Broadcast became a tripartite body
by including in the Memorandum of Understanding also CENELEC, which is responsible for the
standardization of radio and television receivers. The EBU is a professional association of broadcasting
organizations whose work includes the co-ordination of its members' activities in the technical, legal,
programme-making and programme-exchange domains. The EBU has active members in about 60
countries in the European broadcasting area; its headquarters is in Geneva.
European Broadcasting Union
CH-1218 GRAND SACONNEX (Geneva)
Switzerland
Tel: +41 22 717 21 11
Fax: +41 22 717 24 81
Digital Video Broadcasting (DVB) Project
Founded in September 1993, the DVB Project is a market-led consortium of public and private sector organizations in
the television industry. Its aim is to establish the framework for the introduction of MPEG-2 based digital television
services. Now comprising over 200 organizations from more than 25 countries around the world, DVB fosters
market-led systems, which meet the real needs, and economic circumstances, of the consumer electronics and the
broadcast industry.
ETSI
5 ETSI TS 101 191 V1.3.1 (2001-01)
1 Scope
The present document specifies a mega-frame, including a mega-frame initialization packet (MIP), which may be used
for synchronization of the Single Frequency Networks (SFN) as well as for the optional control of other important
parameters in an SFN.
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
• References are either specific (identified by date of publication and/or edition number or version number) or
non-specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies.
[1] ISO/IEC 13818-1 (1994): "Information Technology - Generic coding of moving pictures and
associated audio information: Systems".
[2] ETSI EN 300 744: "Digital Video Broadcasting (DVB); Framing structure, channel coding and
modulation for digital terrestrial television".
[3] ETSI EN 300 468: "Digital Video Broadcasting (DVB); Specification for Service Information (SI)
in DVB systems".
3 Definition and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
cell: for the definition of a cell, see EN 300 468 [3], clause 3.1
frame: for the definition of a DVB-T frame, see EN 300 744 [2], clause 4.4
super-frame: for the definition of a DVB-T super-frame, see EN 300 744 [2], clause 4.4
3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
CRC Cyclic Redundancy Check
DVB Digital Video Broadcasting
DVB-T DVB-Terrestrial
ERP Effective Radiated Power
GPS Global Positioning System
HP High Priority
LP Low Priority
MFN Multi Frequency Network
MFP Mega-Frame Packet
MIP Mega-frame Initialization Packet
MPEG Moving Pictures Expert Group
PID Packet IDentifier
pps pulse per second
ETSI
6 ETSI TS 101 191 V1.3.1 (2001-01)
RF Radio Frequency
RS Reed-Solomon
SFN Single Frequency Network
SI Service Information
STS Synchronization Time Stamp
SYNC SYNChronization
TPH Transport Packet Header
TPS Transport Parameter Signalling
TS Transport Stream
TX/RX Transmitter/Receiver
4 General description
Figure 1 shows a block diagram of a complete SFN system.
MPEG-2
remultiplexer
SFN
adapter
MPEG-2
TS
TX
Network
adapter
Distribution
Network
RX
Network
adapter
RX
Network
adapter
GPS (note)
10 MHz 1 pps
DVB-T
modulator
SYNC
system
GPS (note)
10 MHz 1 pps
DVB-T
modulator
SYNC
system
GPS (note)
10 MHz 1 pps
MPEG-2
TS
MPEG-2
TS
NOTE: Could be any common available frequency reference.
Figure 1: DVB-T primary distribution with SFN adaptation
The SFN functionality is an extension to the DVB system. The blocks associated with SFN functionality are the grey
boxes in figure 1. These blocks could be implemented either as separate equipment or integrated in the multiplexer
and/or the DVB-T modulator.
ETSI
7 ETSI TS 101 191 V1.3.1 (2001-01)
4.1 SFN system blocks
MPEG-2 re-multiplexer
The MPEG-2 re-multiplexer re-multiplexes the programmes from various input channels, updates the SI and provides
an MPEG-2 TS which, after SFN adaptation, is transmitted via the DVB-T modulators in the SFN.
SFN adapter
The SFN adapter forms a mega-frame, consisting of n TS-packets corresponding to 8 DVB-T frames in the 8K mode or
32 frames in the 2K mode, and inserts a Mega-frame Initialization Packet (MIP) with a dedicated PID value. Inserted
anywhere within a mega-frame of index M, the MIP of that mega-frame, MIPM, allows to uniquely identify the starting
point (i.e. the first packet) of the mega-frame M + 1. This is accomplished by using a pointer carried by the MIPM itself
to indicate its position with regards to the start of the mega-frame M + 1.
The time difference between the latest pulse of the "one-pulse-per-second" reference, derived e.g. from GPS, that
precedes the start of the mega-frame M + 1 and the actual start (i.e. first bit of first packet) of this mega-frame M + 1 is
copied into the MIP
M
. This parameter is called Synchronization Time Stamp (STS).
The time duration of a mega-frame is independent of the duration T
u, constellation and code rate of the DVB-T signal.
Four different time durations exist, for each type of channel width, depending on the chosen guard interval proportion,
as shown table 1a:
Table 1a
Guard Interval Channel width
(Δ/Tu) 6 MHz 7 MHz 8MHz
1/4 0,812 373 0,696 320 0,609 280
1/8 0,731 136 0,626 688 0,548 352
1/16 0,690 517 0,591 872 0,517 888
1/32 0,670 208 0,574 464 0,502 656
The output of the SFN adapter shall be fully DVB/MPEG-2 TS compliant.
Transmitter/Receiver network adapter
The network adapters shall provide a transparent link for the MPEG-2 TS from the central to the local units. The
maximum network delay - caused by the different paths of the transmission network - the SYNC system can handle is
1 second.
SYNC system
The SYNC system will provide a propagation time compensation by comparing the inserted STS with the local time
reference and calculate the extra delay needed for SFN synchronization. See annex B for an example of the
synchronization process.
DVB-T modulator
The modulator should provide a fixed delay from the input to the air interface. The information inserted in the MIP
could be used for the direct control of the modulator modes or control of other transmitter parameters. The modulator
clocks at the different sites have to be synchronized. Since it is a requirement of an SFN that all transmitted signals be
identical, the MPEG-2 TS inputs to the various DVB-T modulators have to be bit identical.
Global Positioning System (GPS)
GPS is one among many possible time references but it is the only one available globally. GPS receivers are available
which provide both a 10 MHz frequency reference and a 1 pulse per second (1 pps) time reference. The 1 pps time
reference, used in SFN synchronization, is divided into 100 ns steps of the 10 MHz clock. The 10 MHz system clock is
assumed to be available at all nodes in the network.
The functional blocks "SFN adapter" and "SYNC system" are additional elements for SFN use, and not necessary in
MFN applications.
ETSI
8 ETSI TS 101 191 V1.3.1 (2001-01)
5 Mega-frame definition
The output of the SFN adapter shall be a valid MPEG-2 TS, where the individual packets are organized in groups,
which constitute a mega-frame. Each mega-frame consists of n packets, where n is an integer number which depends on
the number of RS-packets per super-frame in the DVB-T mode that will be used for DVB-T emission of the
MPEG-2 TS (see EN 300 744 [2], clause 4.7). In the 8K mode n is (the number of RS-packets per super-frame) × 2. In
the 2K mode n is (the number of RS-packets per super-frame) × 8.
Each mega-frame contains exactly one Mega-frame Initialization Packet (MIP). The actual position may vary in an
arbitrary way from mega-frame to mega-frame. The pointer value in the MIP is used to indicate the start of the
following mega-frame. In figure 2 the overall structure of the mega-frame, including the positioning of the MIP, is
given. The exact definition of the MIP format is given in clause 6.
First Packet MIP Last Packet
MFP #0 MFP #1 ….. MFP #p ….. MFP #n-1 MFP #0
Pointer = (n-1) - p
The pointer indicates the location
of the first packet of the next
mega-frame.
Mega-frame
Figure 2: Overall mega-frame structure
The start of a mega-frame in the DVB-T signal is in the present document defined to coincide with the beginning of a
DVB-T super-frame and the start of an inverted sync byte, being part of transport multiplex adaptation.
The use of a mega-frame and the insertion of a MIP are additional elements for SFN use, and not necessary in MFN
applications.
ETSI
9 ETSI TS 101 191 V1.3.1 (2001-01)
6 Mega-frame Initialization Packet (MIP)
The MIP is an MPEG-2 compliant Transport Stream (TS) packet, made up of a 4-byte header and a 184-byte data field.
The organization of the MIP is shown in table 1b.
Table 1b: Mega-frame Initialization Packet (MIP)
Syntax Number of bits Identifier
mega-frame_initialization_packet(){
transport_packet_header 32 bslbf
synchronization_id 8 uimsbf
section_length 8 uimsbf
pointer 16 uimsbf
periodic_flag 1 bslbf
future_use 15 bslbf
synchronization_time_stamp 24 uimsbf
maximum_delay 24 uimsbf
tps_mip 32 bsblf
individual_addressing_length 8 uimsbf
for (i=0;i<N;i++){
tx_identifier 16 uimsbf
function_loop_length
for(i=0;i<N;i++){
function()
}
}
8 uimsbf
crc_32 32 rpchof
for (i=0, i<N,i++){
stuffing_byte
}
}
8 uimsbf
NOTE 1: Optional parameters are shown in italic.
NOTE 2: All parameter values in the MIPM apply to mega-frame M + 1, i.e. to the mega-frame pointed out by the pointer,
except for the tps_mip which describes the parameters of mega-frame M + 2. See annex C for details.
NOTE 3: For the definition of the CRC decoder model, see annex A.
NOTE 4: The length of a MIP shall always be 188 bytes.
transport_packet_header: The transport_packet_header shall comply with ISO/IEC 13818-1 [1] clause 2.4.3.2,
tables 2 and 3.
The PID value for the Mega-frame initialization Packet (MIP) shall be 0 x 15.
The payload_unit_start_indicator is not used by the SFN synchronization function and shall be set to 1.
The transport_priority value is not used by the SFN synchronization function and shall be set to 1.
The transport_scrambling_control value shall be set to 00 (not scrambled).
The adaptation_field_control value shall be set to 01 (payload only).
All other parameters are according to ISO/IEC 13818-1 [1] clause 2.4.3.2.
The Transport Packet Header (TPH) is mandatory.
Mandatory SFN parameters
synchronization_id: the synchronization_id is used to identify the synchronization scheme used (see table 2).
Table 2: Signalling format for the synchronization_id
Synchronization_id Function
0 x 00 SFN synchronization
0 x 01 - 0 x FF Future use
ETSI
10 ETSI TS 101 191 V1.3.1 (2001-01)
section_length: the section_length specifies the number of bytes following immediately after the section_length field
until, and including, the last byte of the crc_32 but not including any stuffing_byte. The section_length shall not exceed
182 bytes.
pointer: the pointer is a 2-byte binary integer indicating the number of transport packets between the MIP and the first
packet of the succeeding mega-frame.
The range of the pointer depends on the DVB-T mode used for emission.
periodic_flag: indicates if a periodic or an aperiodic insertion of the MIP is performed. Periodic insertion means that
the value of the pointer is not time varying. A "0" indicates aperiodic mode and a "1" indicates periodic mode. All SFN
"SYNC systems" shall be able to handle both aperiodic and periodic mode.
future_use: reserved for future use.
synchronization_time_stamp: the synchronization_time_stamp of MIPM contains the time difference, expressed as a
number of 100 ns steps, between the latest pulse of the "one-pulse-per-second" reference (derived e.g. from GPS) that
precedes the start of the mega-frame M + 1 and the actual start (i.e. beginning of first bit of first packet) of this
mega-frame M + 1.
maximum_delay: the maximum_delay contains the time difference between the time of emission of the start of megaframe
M+ 1 of the DVB-T signal from the transmitting antenna and the start of mega-frame M + 1 at the SFN adapter,
as expressed by the value of its synchronization_time_stamp in the MIPM. The value of maximum_delay shall be larger
than the sum of the longest delay in the primary distribution network and the delays in modulators, power transmitters
and antenna feeders. The unit is 100 ns and the range of maximum_delay is 0 x 000000 - 0 x 98967F, this equals a
maximum delay of 1 second.
tps_mip: the tps_mip consists of 32 bits, P
0
-P
31
. The relationship between the TPS as defined in EN 300 744 [2] and
tps_mip as defined in the present document is described in table 3.
ETSI
11 ETSI TS 101 191 V1.3.1 (2001-01)
Table 3: Relationship between TPS (as defined in EN 300 744 [2]) and tps_mip
(as defined in the present document)
Bit number (TPS) Format Purpose/Content Bit number (tps_mip)
s
0
see clause 4.6.2.1,
EN 300 744 [2]
Initialization Not used
s
1
- s
16
0011010111101110 or
1100101000010001
Synchronization word Not used
s
17
- s
22
see clause 4.6.2.3,
EN 300 744 [2]
Length indicator Not used
s
23
, s
24
see table 12,
EN 300 744 [2]
Frame number Not used
s
25
, s
26
see table 13,
EN 300 744 [2]
Constellation P
0,
P
1
s
27
, s
28
, s
29
see table 14,
EN 300 744 [2]
Hierarchy information P
2
,P
3
,P
4
s
30
, s
31
, s
32
see table 15,
EN 300 744 [2]
Code rate, HP stream P
5
,P
6
,P
7
s
33
, s
34
, s
35
see table 15,
EN 300 744 [2]
Code rate, LP stream P
5
,P
6
,P
7
s
36
, s
37
see table 16,
EN 300 744 [2]
Guard interval P
8,
P
9
s
38
, s
39
see table 17,
EN 300 744 [2]
Transmission mode P
10
,P
11
s
40
- s
47
see table 18,
EN 300 744 [2]
Cell identifier Not used
s48 - s
53
all set to "0" Reserved for future use P
15
- P
31
s54 - s67 BCH code Error protection Not used
- see table 4: "Signalling
format for the bandwidth"
Bandwidth of the RF channel P
12
,P
13
- see table 5: "Signalling
format for the bit stream
priority"
The priority of the transport stream P
14
NOTE: There are 17 bits allocated for future use in tps_mip, whereas there are 6 bits allocated in the TPS of
EN 300 744 [2].
Table 4: Signalling format for the bandwidth
Bits P
12
, P
13
Bandwidth
00 7 MHz
01 8 MHz
10 6 MHz
11 reserved for future use
Table 5: Signalling format for the bit stream priority
Bit P
14
Transmission mode
0 Low Priority TS
1 High Priority TS
P
0
-P
13
: in case of inconsistent values of P
0
-P
13
for the High Priority and Low Priority Transport Streams, the HP value is
valid. In case of change of DVB-T mode, see annex C for the time relationship between P
0
-P
13
and the TPS data of the
DVB-T signal.
individual_addressing_length: the individual_addressing_length field gives the total length of the individual
addressing field in bytes. If individual addressing of transmitters is not performed the field value is 0 x 00, indicating
that the crc_32 immediately follows the individual_addressing_length.
crc_32: this 32 bit crc_32 field contains the CRC value that gives a zero output of the registers in the decoder defined in
annex A of the present document, after processing all of the bytes in theMIP, excluding the stuffing bytes.
ETSI
12 ETSI TS 101 191 V1.3.1 (2001-01)
stuffing_byte: every stuffing_byte has the value 0 x FF.
Optional MIP section parameters
tx_identifier: the tx_identifier is a 16-bit word used to address an individual transmitter. The tx_identifier value
0 x 0000 is used as a broadcast address to address all transmitters in the network.
function_loop_length: the function_loop_length field gives the total length of the function loop field in bytes.
function: the functions are described in clause 6.1.
6.1 Functions
Parameters common to all functions:
function_tag: The function_tag specifies the function identification.
function_length: The function_length field gives the total length of the function field in bytes.
Table 6 gives the function_tag value for the functions defined in the present document. All functions are optional and
similar commands could be sent via a separate management network.
Table 6: Tag value of functions
Function function_tag value
tx_time_offset_function 0 x 00
tx_frequency_offset_function 0 x 01
tx_power_function 0 x 02
private_data_function 0 x 03
cell_id_function 0 x 04
enable_function 0 x 05
Future_use 0 x 06 - 0 x FF
6.1.1 Transmitter time offset function
The tx_time_offset_function is used to apply a deliberate offset in time of the transmitted DVB-T signal, relative to the
reference transmission time (STS + maximum_delay) modulo 107.
Table 7: Function transmitter time offset
Syntax Number of bits Identifier
tx_time_offset_function(){
function_tag 8 uimsbf
function_length 8 uimsbf
time_offset 16 tcimsbf
}
time_offset: The deliberate time offset of the mega-frames. The unit is 100 ns. The range is [-32 768,32 767] × 100 ns.
NOTE: The use of the complete range is not foreseen.
ETSI
13 ETSI TS 101 191 V1.3.1 (2001-01)
6.1.2 Transmitter frequency offset function
The tx_frequency_offset_function is used to apply a deliberate frequency offset of the centre frequency of the emitted
DVB-T signal relative to the centre frequency of the RF channel.
Table 8: Function transmitter frequency offset
Syntax Number of bits Identifier
tx_frequency_offset_function(){
function_tag 8 uimsbf
function_length 8 uimsbf
frequency_offset 24 tcimsbf
}
frequency_offset: The deliberate frequency offset relative to the centre frequency of the RF channel in use. The unit is
1 Hz. The range is [-8 388 608,8 388 607] × 1 Hz.
NOTE: The use of the complete range is not foreseen.
6.1.3 Transmitter power function
The tx_power_function can be used to configure the transmitter ERP.
Table 9: Function transmitter power
Syntax Number of bits Identifier
tx_power_function (){
function_tag 8 uimsbf
function_length 8 uimsbf
power 16 uimsbf
}
power: The power of the transmitter is defined as the ERP. The unit is 0,1 dB. The range is ([0,655 35] × 0,1) dBm.
NOTE: The use of the complete range is not foreseen.
6.1.4 Private data function
The private_data_function is used to send private data to the transmitters via the MIP.
Table 10: Function private data
Syntax Number of bits Identifier
private_data_function(){
function_tag 8 uimsbf
function_length 8 uimsbf
for (i=0;i<N;i++){
private_data 8 bsblf
}
}
private_data: The private data can be used for proprietary functions.
ETSI
14 ETSI TS 101 191 V1.3.1 (2001-01)
6.1.5 Cell id function
The cell_id_function can be used to configure the cell identifier of the transmitter.
Table 11: Function cell id
Syntax No. of bits Identifier
cell_id_function(){
function_tag 8 uimsbf
function_length 8 uimsbf
cell_id 16 uimsbf
wait for_enable_flag 1 bslbf
reserved_future_use 7 bslbf
}
cell_id: The cell_id [3] is used to uniquely identify the cell to which the transmitter belongs to.
wait_for_enable_flag: If this flag is set to "0" then the cell_id within the cell_id_function has to be inserted
immediately. If this flag is set to "1" then the cell_id within the cell_id_function has to be inserted immediately after
having received the corresponding enable_function.
6.1.6 Enable function
The enable_function can be used to execute the change of parameters provided by means of other MIP functions before.
Table 12: Function enable
Syntax No. of bits Identifier
enable_function(){
function_tag 8 uimsbf
function_length 8 uimsbf
for (i=0;i<N;i++=){
enabled_function_tag 8 uimsbf
}
}
enabled_function_tag: This 8-bit field indicates the function that is enabled by means of the enable_function. The
coding is according to table 6.
ETSI
15 ETSI TS 101 191 V1.3.1 (2001-01)
Annex A (normative):
CRC decoder model
The 32-bit CRC decoder is specified in figure A.1.
Figure A.1: 32-bit CRC decoder model
The 32 bit CRC decoder operates at bit level and consists of 14 adders + and 32 delay elements z (i). The input of the
CRC decoder is added to the output of z (31), and the result is provided to the input z (0) and to one of the inputs of
each remaining adder. The other input of each remaining adder is the output of z (i), while the output of each remaining
adder is connected to the input of z (i + 1), with i = 0, 1, 3, 4, 6, 7, 9, 10, 11, 15, 21, 22, and 25 (see figure A.1).
This is the CRC calculated with the polynomial:
x32 + x26 + x23 + x22 + x16 + x12 + x11 + x10 + x8 + x7 + x5 + x4 + x2 + x + 1
Before the CRC processing of the data of a MIP the output of each delay element z (i) is set to its initial value "1". After
this initialization, each byte of the MIP is provided to the input of the CRC decoder, including the four crc_32 bytes, but
excluding any stuffing byte. Each byte is shifted into the CRC decoder one bit at a time, with the most significant bit
(msb) first, i.e. from the TS packet sync byte 0 x 47 (0100 0111) first a "0" enter the CRC decoder, followed by a "1".
After shifting the last bit of the last crc_32 byte into the decoder, i.e. into z (0) after the addition with the output of
z (31), the output of all delay elements z (i) is read. In case of no errors, each of the outputs of z (i) has to be zero. At
the CRC encoder the crc_32 field is encoded with such value that this is ensured.
ETSI
16 ETSI TS 101 191 V1.3.1 (2001-01)
Annex B (normative):
Functional description of SFN synchronization
Ttransmitted
Transmitted Mega-frame
STS
1 second
Trec
maximum_delay
Tdelay
1 second
Transmission of first
Transport Packet of Megaframe
Received Mega-frame
NOTE: All values are in 100 ns (10 MHz clock)
Ttransmitted = (STS + maximum_delay) modulo 107 (from transmitter)
Tdelay = (STS + maximum_delay - Trec) modulo 107
Figure B.1
ETSI
17 ETSI TS 101 191 V1.3.1 (2001-01)
Annex C (normative):
Reconfiguration of DVB-T modulator parameters by using
the MIP
The tps_mip bits P
0
-P
14
, inserted in the MIP at the multiplexer, are used to reconfigure the parameters of the DVB-T
modulator. The bits P
0
-P
11
are also transmitted as the TPS bits s
25
- s
39
of the DVB-T signal, as information to the
receiver. In EN 300 744 [2], it is stated that the TPS information transmitted in super-frame m' bits s
25
- s
39
always apply
to super-frame m' + 1, whereas all other bits refer to super-frame m'. In order to define a non-ambiguous switch time the
following shall apply: Inserted in the MIP being sent in mega-frame 1, the tps_mip describes the parameters of
mega-frame 3. The DVB-T modulator will thus be able:
- first to update the data carried by its TPS carriers at the start of the last (i.e. the second in the 8K mode, and the
8th in the 2K mode) super frame of mega-frame 2;
- then to update its new configuration at the start of mega-frame 3.
time
Multiplexer
Mega-frame 1
Super-frame
SF1 SF2 SF1 SF2 SF1 SF2
Mega-frame 2 Mega-frame 3
Transmitter
Mega-frame 1
Super-frame
SF1 SF2 SF1 SF2 SF1 SF2
Mega-frame 2 Mega-frame 3
MIP containing
changed tps_mip
Pointer
New TPS data inserted in
the DVB-T super-frame
The new configuration of the
DVB-T modulator is executed at
the start of mega-frame 3
New TS bit rate according
to new tps_mip data.
Figure C.1: Reconfiguration of DVB-T modulator parameters by using the MIP
ETSI
18 ETSI TS 101 191 V1.3.1 (2001-01)
History
Document history
V1.1.1 February 1999 Withdrawn
V1.2.1 April 1998 Publication
V1.3.1 January 2001 Publication
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