Note: Descriptions are shown in the official language in which they were submitted.
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Description
DIGITAL BROADCASTING SYSTEM AND METHOD OF
PROCESSING DATA
Technical Field
[1] The present invention relates to a digital broadcasting system, and
more
particularly, to a digital broadcasting system and a method of processing data
that can receive
and transmit (or process) digital broadcast signals.
Background Art
[2] The Vestigial Sideband (VSB) transmission method, which is adopted as
the
standard for digital broadcasting in North America and the Republic of Korea,
is a system
using a single carrier method. Therefore, the receiving performance of the
receiving system
may be deteriorated in a poor channel environment.
Disclosure of Invention
[3] Particularly, since resistance to changes in channels and noise is more
highly
required when using portable and/or mobile broadcast receivers, the receiving
performance
may be even more deteriorated when transmitting mobile service data by the VSB
transmission method.
According to one aspect of the present invention, there is provided a method
of
processing data in a transmitting system, the method comprising: Reed-Solomon
(RS) and
Cyclic Redundancy Check (CRC) encoding mobile service data in an RS frame
unit;
converting data bytes of the RS and CRC encoded mobile service data into data
bits of the
mobile service data; encoding the data bits of the mobile service data at a
coding rate of 1/2 or
1/4; inserting an MPEG header place holder, a non-systematic RS parity place
holder and a
main service data place holder into a data group having the encoded mobile
service data;
deinterleaving data in the data group including the MPEG header place holder,
the
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non-systematic RS parity place holder and the main service data place holder;
removing the
main service data place holder and the non-systematic RS parity place holder,
replacing the
MPEG header place holder with an MPEG header, and forming mobile service data
packets
including the mobile service data and the replaced MPEG header in the data
group, wherein
the mobile service data packets include a mobile audio data packet and a
mobile non-audio
data packet for a mobile handheld broadcast receiver; adjusting a relative
position of main
service data packets to compensate displacement of the main service data
packets, the
displacement being occurred due to a multiplexing process of the mobile and
main service
data packets, wherein a corresponding program clock reference (PCR) value is
adjusted when
at least one main service data packet is re-positioned and wherein the main
service data
packets include a main audio data packet and a main non-audio data packet for
a conventional
broadcast receiver; and multiplexing the mobile service data packets with the
main service
data packets to transmit on a same channel.
According to another aspect of the present invention, there is provided a
transmitter in a transmitting system, the transmitter comprising: a packet
jitter mitigator for
adjusting a relative position of main service data packets to compensate
displacement of the
main service data packets, the displacement being occurred due to a
multiplexing process of
mobile service data packets and the main service data packets, wherein a
corresponding
program clock reference (PCR) value is adjusted when at least one main service
data packet is
re-positioned and wherein the main service data packets include a main audio
data packet and
a main non-audio data packet for a conventional broadcast receiver; a pre-
processor for Reed-
Solomon (RS) and Cyclic Redundancy Check (CRC) encoding mobile service data in
an RS
frame unit, converting data bytes of the RS and CRC encoded mobile service
data into data
bits of the mobile service data, encoding the data bits of the mobile service
data at a coding
rate of 1/2 or 1/4, inserting an MPEG header place holder, a non-systematic RS
parity place
holder and a main service data place holder into a data group having the
encoded mobile
service data, deinterleaving data in the data group including the MPEG header
place holder,
the non-systematic RS parity place holder and the main service data place
holder, removing
the main service data place holder and the non-systematic RS parity place
holder, replacing
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the MPEG header place holder with an MPEG header, and forming the mobile
service data
packets including the mobile service data and the replaced MPEG header in the
data group,
wherein the mobile service data packets include a mobile audio data packet and
a mobile non-
audio data packet for a mobile handheld broadcast receiver; and a multiplexer
for
multiplexing the mobile service data packets being outputted from the pre-
processor with the
main service data packets being outputted from the packet jitter mitigator to
transmit on a
same channel.
According to still another aspect of the present invention, there is provided
a
method of processing data in a receiving system, the method comprising:
receiving a
broadcast signal, wherein the broadcast signal comprises mobile service data
packets and
main service data packets, the mobile service data packets being multiplexed
with the main
service data packets on a same channel, wherein the mobile service data
packets have a
mobile audio data packet and a mobile non-audio data packet for a mobile
handheld broadcast
receiver, and the main service data packets have a main audio data packet and
a main non-
audio data packet for a conventional broadcast receiver, wherein the mobile
service data
packets further include mobile service data, the mobile service data being pre-
processed by a
transmitting system in steps comprising: Reed-Solomon (RS) - Cyclic Redundancy
Check
(CRC) encoding the mobile service data in an RS frame unit; converting data
bytes of the RS
and CRC encoded mobile service data into data bits of the mobile service data;
encoding the
data bits of the mobile service data at a coding rate of 1/2 or 1/4; inserting
an MPEG header
place holder, a non-systematic RS parity place holder and a main service data
place holder
into a data group having the encoded mobile service data; deinterleaving data
in the data
group including the MPEG header place holder, the non-systematic RS parity
place holder
and the main service data place holder; removing the main service data place
holder and the
non-systematic RS parity place holder, replacing the MPEG header place holder
with an
MPEG header, and forming mobile service data packets including the mobile
service data and
the replaced MPEG header in the data group; and multiplexing the formed mobile
service data
packets with main service data packets, wherein the main service data packets
are adjusted to
compensate for temporal displacement of the main service data packets
occurring due to the
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multiplexing of the mobile service data packets and main service data packets
in the
transmitting system, and wherein a corresponding program clock reference (PCR)
value is
adjusted when at least one main service data packet is re-positioned;
demodulating the
received broadcasting signal; and performing error correction decoding on the
mobile service
data within the mobile service data packets of the demodulated broadcast
signal in order to
correct an error generated in the mobile service data.
According to yet another aspect of the present invention, there is provided a
receiving system for processing data, the receiving system comprising: a tuner
for receiving a
broadcast signal, wherein the broadcast signal comprises mobile service data
packets and
main service data packets, the mobile service data packets being multiplexed
with the main
service data packets on a same channel, wherein the mobile service data
packets have a
mobile audio data packet and a mobile non-audio data packet for a mobile
handheld broadcast
receiver, and the main service data packets have a main audio data packet and
a main non-
audio data packet for a conventional broadcast receiver, wherein the mobile
service data
packets further include mobile service data, the mobile service data being pre-
processed by a
transmitting system in steps comprising: Reed-Solomon (RS) - Cyclic Redundancy
Check
(CRC) encoding the mobile service data in an RS frame unit; converting data
bytes of the RS
and CRC encoded mobile service data into data bits of the mobile service data;
encoding the
data bits of the mobile service data at a coding rate of 1/2 or 1/4; inserting
an MPEG header
place holder, a non-systematic RS parity place holder and a main service data
place holder
into a data group having the encoded mobile service data; deinterleaving data
in the data
group including the MPEG header place holder, the non-systematic RS parity
place holder
and the main service data place holder; removing the main service data place
holder and the
non-systematic RS parity place holder, replacing the MPEG header place holder
with an
MPEG header, and forming mobile service data packets including the mobile
service data and
the replaced MPEG header in the data group; and multiplexing the formed mobile
service data
packets with main service data packets, wherein the main service data packets
are adjusted to
compensate for temporal displacement of the main service data packets
occurring due to the
multiplexing of the mobile service data packets and main service data packets
in the
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transmitting system, and wherein a corresponding program clock reference (PCR)
value is
adjusted when at least one main service data packet is re-positioned; a
demodulator for
demodulating the received broadcasting signal; a decoder for performing error
correction
decoding on the mobile service data within the mobile service data packets of
the
demodulated broadcast signal in order to correct an error generated in the
mobile service data.
[4] Some embodiments of the present invention may provide a digital
broadcasting
system and a data processing method that substantially obviate one or more
problems due to
limitations and disadvantages of the related art.
[5] Some embodiments of the present invention may provide a digital
broadcasting
system and a method of processing data that are highly resistant to channel
changes and noise.
[6] Some embodiments of the present invention may provide a digital
broadcasting
system and a method of processing data that can enhance the receiving
performance of a
receiving system by performing additional encoding on mobile service data and
by
transmitting the processed data to the receiving system.
[7] Additional features of embodiments of the invention will be set forth
in part in
the description which follows and in part will become apparent to those having
ordinary skill
in the art upon examination of the following or may be learned from practice
of the invention.
[8] A method of processing data in a transmitting system of a digital
broadcasting
system may include creating a data group including a plurality of mobile
service data packets,
re-adjusting a relative position of at least one main service data packet of a
main service data
section, the main service data section including a plurality of main service
data packets, and
multiplexing the mobile service data of the data group and the main service
data of the main
service data section in burst units. Herein, a position of an audio data
packet among the main
service data packets of the main service data section may be readjusted. Also,
a position of an
audio data packet included in the main service data section may be re-adjusted
based upon a
multiplexing position of the main service data section.
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[9] In another aspect of the present invention, a service multiplexer in a
transmitting system includes a main service multiplexer, a mobile service
multiplexer, and a
multiplexer. The main service multiplexer multiplexes compression-encoded main
service
data and main ancillary data. The mobile service multiplexer multiplexes
compression-
encoded mobile service data and mobile ancillary data. And, the multiplexer
multiplexes
output data of the main service multiplexer and output data of the mobile
service multiplexer,
thereby outputting the multiplexed data to at least one transmitter located in
a remote site.
[10] In a further aspect of the present invention, a transmitter of a
digital broadcast
transmitting system includes a demultiplexer, a packet jitter mitigator, a pre-
processor, and
multiplexer. The demultiplexer receives and demultiplexes multiplexed main
service data and
mobile service data. The packet jitter mitigator adjusts a position of at
least one main service
data packet included in a main service data section, the main service data
packet being
demultiplexed and outputted from the demultiplexer. The pre-processor performs
additional
encoding on the mobile service data being demultiplexed and outputted from the
demultiplexer, and creates a data group including a plurality of encoded
mobile service data
packets. And, the multiplexer multiplexes and outputs, in burst units, the
mobile service data
of the data group being outputted from the pre-processor and the main service
data of the
main service data section being outputted from the packet jitter mitigator.
[11] It is to be understood that both the foregoing general description and
the
following detailed description of the present invention are exemplary and
explanatory and are
intended to provide further explanation of the invention as claimed.
[12] Some embodiments of the present invention may have one or more of the
following advantages. More specifically, some embodiments of the present
invention may be
robust against (or resistant to) any error that may occur when transmitting
mobile service data
through a channel. And, some embodiments of the present invention may also be
highly
compatible to the conventional system. Moreover, some embodiments of the
present
invention may also receive the mobile service data without any error even in
channels having
severe ghost effect and noise.
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[13] Additionally, by performing error correction encoding and error
detection
encoding processes on the mobile service data and transmitting the processed
data, some
embodiments of the present invention may provide robustness to the mobile
service data,
thereby enabling the data to effectively respond to the frequent change in
channels. Also, in
some embodiments when the main service data and the mobile service data are
multiplexed in
a burst structure, a relative position of a main service data packet is re-
adjusted and then
multiplexed, thereby mitigating packet jitter, which may occur when the
receiving system
receives the multiplexed main service data packet.
[14] Furthermore, some embodiments of the present invention may be even
more
effective when applied to mobile and portable receivers, which are also liable
to a frequent
change in channel and which require protection (or resistance) against intense
noise.
Brief Description of the Drawings
[15] The accompanying drawings, which are included to provide a further
understanding of the invention and are incorporated in and constitute a part
of this application,
illustrate embodiment(s) of the invention and together with the description
serve to explain the
principle of the invention. In the drawings:
[16] FIG. 1 illustrates a block diagram showing a general structure of a
digital
broadcasting system according to an embodiment of the present invention;
[17] FIG. 2 illustrates a block diagram showing an example of a service
multiplexer
of FIG. 1;
[18] FIG. 3 illustrates a block diagram showing an example of a pre-
processor of
FIG. 2;
[19] FIG. 4 illustrates a block diagram showing an example of a
transmitter of FIG.
1;
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[20] FIG. 5(a) to FIG. 5(d) illustrate a process of realigning main service
data
according to an embodiment of the present invention; and
[21] FIG. 6 illustrates a block diagram showing a structure of a digital
broadcast
receiving system according to an embodiment of the present invention.
Detailed Description
[22] Reference will now be made in detail to various embodiments of the
present
invention, examples of which are illustrated in the accompanying drawings.
Wherever
possible, the same reference numbers will be used throughout the drawings to
refer to the
same or like parts. In addition, although the terms used in the present
invention are selected
from generally known and used terms, some of the terms mentioned in the
description of the
present invention have been selected by the applicant at his or her
discretion, the detailed
meanings of which are described in relevant parts of the de-
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scription herein. Furthermore, it is required that the present invention is
understood,
not simply by the actual terms used but by the meaning of each term lying
within.
[23] In the present invention, the mobile service data may either consist of
data including
information such as program execution files, stock information, weather
forecast, and
so on, or consist of audio/video (A/V) data. Additionally, the known data
refer to data
already known based upon a pre-determined agreement between the transmitter
and the
receiver. Furthermore, the main service data consist of data that can be
received from
the conventional receiving system, wherein the main service data include A/V
data.
Also, a data service using the mobile service data may include weather
forecast
services, traffic information services, stock information services, viewer
participation
quiz programs, real-time polls & surveys, interactive education broadcast
programs,
gaming services, services providing information on synopsis, character,
background
music, and filming sites of soap operas or series, services providing
information on
past match scores and player profiles and achievements, and services providing
in-
formation on product information and programs classified by service, medium,
time,
and theme enabling purchase orders to be processed. Herein, the present
invention is
not limited only to the services mentioned above.
[24] The present invention relates to a transmission system that can be
compatible with
the conventional transmission method. Additionally, the transmission system
may also
multiplex the main service data and mobile service data of the same channel,
and then,
transmit the multiplexed data. When using the transmitting system according to
the
present invention, the mobile service data may be received while the user is
in a mobile
state (i.e., traveling). Also, the mobile service data may be received with
stability
despite the noise and diverse distortion occurring in the channel.
[25] Furthermore, the transmitting system according to the present invention
may perform
additional encoding, and insert data pre-known by both transmitting and
receiving
systems (i.e., known data) and transmit the processed data, thereby enhancing
the
receiving performance. The present invention may also mitigate packet jitter
when
multiplexing the main service data and the mobile service data.
[26] FIG. 1 illustrates a block diagram showing a general structure of a
transmitting
system according to an embodiment of the present invention. Herein, the
transmitting
system includes a service multiplexer 110 and a transmitter 120. Herein, the
service
multiplexer 110 is located in the studio of each broadcast station, and the
transmitter
120 is located in a specific predetermined site. The transmitter 120 may be
located in a
plurality of different locations. Also, the plurality of transmitters may
share the same
frequency. And, in this case, the plurality of transmitters transmits the same
signal. Ac-
cordingly, in the receiving system 130, a channel equalizer may compensate
signal
distortion, which is caused by a reflected wave, so as to recover the original
signal. A
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variety of methods may be used for data communication each of the transmitters
120,
which are located in remote positions, and the service multiplexer 110. For
example,
an interface standard such as a synchronous serial interface for transport of
MPEG-2
data (SMPTE-310M).
[27] FIG. 2 illustrates a block diagram of a service multiplexer according to
an em-
bodiment of the present invention. Referring to FIG. 2, the service
multiplexer includes
a main service multiplexer 230 for multiplexing and outputting main service
data, a
mobile service multiplexer 260 for multiplexing and outputting mobile service
data,
and a multiplexer 270 for multiplexing and outputting the service data from
both
service multiplexers 230 and 260. More specifically, the main service data are
encoded
and compressed by a main A/V system 210, which are the outputted to the main
service multiplexer 230. Herein, if there is a plurality of main service data
types, a
plurality of main AN systems may be provided. The main service multiplexer 230
multiplexes the output of the main AN system 210 and main ancillary/control
data 220
and, then, outputs the multiplexed data to the multiplexer 270.
[28] Similarly, the mobile service data are encoded and compressed by a mobile
A/V
system 240, which are the outputted to the mobile service multiplexer 260.
Herein, if
there is a plurality of mobile service data types, a plurality of mobile A/V
systems may
be provided. The mobile service multiplexer 260 multiplexes the output of the
mobile
A/V system 240 and mobile ancillary/control data 250 and, then, outputs the
mul-
tiplexed data to the multiplexer 270.
[29] The multiplexer 270 multiplexes the output of the main service
multiplexer 230 and
the output of the mobile service multiplexer 260 and, then, outputs the
multiplexed
data to at least one of the transmitters. The output data of the multiplexer
270 is
configured to have a MPEG-2 transport stream (TS) format. At this point, if
the service
data being transmitted to the transmitter 120 from the service multiplexer
110, are
configured only of the main service data, the service multiplexer 110
transmits the
main service data to the transmitter 120 at a data rate of approximately 19.39
Mbps.
[30] However, when the service multiplexer 110 multiplexes the main service
data and the
mobile service data and outputs the multiplexed data to the transmitter 120,
the service
multiplexer 110 transmits the main service data at a data rate lower than
19.39 Mbps.
This applies more to the mobile service data, since additional error
correction encoding
is performed by the transmitter 120, thereby reducing the data rate.
Therefore, the
output data rate of the multiplexer 270 included in the service multiplexer
110, which
multiplexes and outputs main service data and mobile service data, is always
equal to
or less than 19.39 Mbps.
[31] If the output of the service multiplexer 110 is required to be maintained
at a constant
data rate (e.g., at 19.39 Mbps), null data or null data packet are/is inserted
in at least
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one of the main service multiplexer 230, the mobile service multiplexer 260,
and the
multiplexer 270, thereby setting the data rate of the final output data to a
constant data
rate. For example, when a main service data rate is set to 15 Mbps, and when a
mobile
service data rate is set to 1 Mbps, and when the output data rate of the
service mul-
tiplexer 110 is required to be maintained at 19.39 Mbps, the multiplexer 270
may insert
null data or a null data packet to the final output data, thereby setting the
final output
data rate to 19.39 Mbps. Herein, the null data may be generated from the
multiplexer
270 or generated from an external part.
[32] The transmitter 120 receiving the null data should first remove the null
data and then
process the remaining data. Therefore, identification information for
identifying the
null data is required by the transmitter 120. A multiplexer for inserting the
null data
multiplexing and transmitting the identification information along with the
null data
will be given as an exemplary embodiment of the present invention.
[33] For example, when the multiplexer 270 inserts null data, identification
information
for identifying the null data is also multiplexed and transmitted by the
multiplexer 270.
Herein, the identification information may use a value pre-decided based upon
an
agreement between the transmitting system and the receiving system, or the
identi-
fication information may be configured as a separate set of data.
Alternatively, the
identification information may also use a modified position value, the
position value
being predetermined in the null data packet.
[34] For example, in the present invention, a synchronization byte value
within a header
of a null data packet may be modified, so as to be used as the identification
in-
formation. Alternatively, a transport error indicator flag may be set to '1',
so as to be
used as the identification information. Herein, any value that can identify
the null data
may be used as the identification information. Therefore, the present
invention is not
limited only to the examples given in the description set forth herein.
[35] Meanwhile, the main service ancillary data may include main service
program
specific information (PSI)/program and system information protocol (PSIP) in-
formation. Similarly, the mobile service ancillary data may include mobile
service PSI/
PSIP information. Additionally, mobile service control data may also be
included.
And, in this case, information for controlling a transmission network may also
be
included in the control data. Furthermore, when the multiplexer 270
multiplexes the
main service data packet and the mobile service data packet, the multiplexer
270 may
include a packet identifier (PID) for identifying each of the main service
data packet
and the mobile service data packet, respectively. In another example, a
bitwise
inversion may be performed on a MPEG synchronization byte of the mobile
service
data packet, so as to identify the mobile service data packet from the main
service data
packet.
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[36] FIG. 3 illustrates a block diagram of a transmitter according to the
present invention.
Referring to FIG. 3, the transmitter includes a demultiplexer (DEMUX) 301, a
packet
jitter mitigator 302, an pre-processor 303, and a first multiplexer 304.
Additionally, the
transmitter also includes a data randomizer 305, a RS encoder/non-systematic
RS
encoder 306, a data interleaver 307, a parity replacer 308, a non-systematic
RS encoder
309, a trellis-encoding module 310, a second multiplexer 311, a pilot inserter
312, a
modulator 313, and a radio frequency (RF)-up converter 314.
[37] FIG. 4 illustrates a block diagram of the pre-processor 303 according to
an em-
bodiment of the present invention. Herein, the pre-processor 303 includes a
data
randomizer 401, a RS frame encoder 402, a block processor 403, a group
formatter
404, a data deinterleaver 405, and a packet formatter 406. In transmitter
having the
above-described structure, the demultiplexer 301 separates main service data
and
mobile service data by demultiplexing the data transmitted from the service
mul-
tiplexer. Then, the separated main service data are outputted to the packet
jitter
mitigator 302, and the separated mobile service data are outputted to the pre-
processor
303.
[38] At this point, when the service multiplexer 110 inserts null data in
order to match the
data rate and transmits the processed data, the demultiplexer 301 refers to
identi-
fication information transmitted along with the processed data so as to
discard the null
data. Then, the deultiplexer 301 demultiplexes only remaining data, which are
then
outputted to each corresponding block. The pre-processor 303 performs
additional
encoding so that the mobile service data can respond more effectively to noise
and
channel environment that undergoes frequent changes. For this, the mobile
service data
separated by the demultiplexer 301 are outputted to the data randomizer 401 of
the pre-
processor 303.
[39] The data randomizer 401 receives mobile service data and randomizes the
received
data, thereby outputting the processed mobile service data to the RS frame
encoder
402. At this point, by having the data randomizer 401 randomize the mobile
service
data, a later randomizing process on the mobile service data performed by a
data
randomizer 305, which is positioned in a later block, may be omitted. The
randomizer
of the conventional system may be identically used as the randomizer for
randomizing
the mobile service data. Alternatively, any other type of randomizer may also
be used
for this process.
[40] The RS frame encoder 402 performs at least one of an error correction
encoding
process and an error detection encoding process on the inputted randomized
mobile
service data so as to provide robustness on the corresponding mobile service
data.
Thus, by providing robustness on the mobile service data, a group error that
may occur
due to a change in the frequency environment can be scattered, thereby
enabling the
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corresponding data to respond to the severely vulnerable and frequently
changing
frequency environment. The RS frame encoder 402 may also include a row per-
mutation process, which permutes mobile service data having a predetermined
size in
row units. Herein, RS encoding is applied as the error correction encoding
process, and
cyclic redundancy check (CRC) encoding is applied as the error detection
encoding
process. When performing RS encoding, parity data that are to be used for
error
correction are generated. And, when performing CRC encoding, CRC data that are
to
be used for error detection are generated.
[41] In this embodiment of the present invention, the RS encoding will be
adopting a
forward error correction (FEC) method. The FEC corresponds to a technique for
com-
pensating errors that occur during the transmission process. The CRC data
generated
by CRC encoding may be used for indicating whether or not the mobile service
data
have been damaged by the errors while being transmitted through the channel.
In the
present invention, a variety of error detection coding methods other than the
CRC
encoding method may be used, or the error correction coding method may be used
to
enhance the overall error correction ability of the receiving system.
[42] As described above, the mobile service data encoded by the RS frame
encoder 402
are inputted to the block processor 403. The block processor 403 then encodes
the
inputted mobile service data at a coding rate of G/H (wherein, G is smaller
than H (i.e.,
G<H)) and then outputted to the group formatter 404. More specifically, the
block
processor 113 divides the mobile service data being inputted in byte units
into bit units.
Then, the G number of bits is encoded to H number of bits. Thereafter, the
encoded
bits are converted back to byte units and then outputted. For example, if 1
bit of the
input data is coded to 2 bits and outputted, then G is equal to 1 and H is
equal to 2 (i.e.,
G=1 and H=2). Alternatively, if 1 bit of the input data is coded to 4 bits and
outputted,
then G is equal to 1 and H is equal to 4 (i.e., G=1 and H=4). Hereinafter, the
former
coding rate will be referred to as a coding rate of 1/2 (1/2-rate coding), and
the latter
coding rate will be referred to as a coding rate of 1/4 (1/4-rate coding), for
simplicity.
[43] Herein, when using the 1/4 coding rate, the coding efficiency is greater
than when
using the 1/2 coding rate, and may, therefore, provide greater and enhanced
error
correction ability. For such reason, when it is assumed that the data encoded
at a 1/4
coding rate in the group formatter 404, which is located near the end portion
of the
system, are allocated to a region in which the receiving performance may be de-
teriorated, and that the data encoded at a 1/2 coding rate are allocated to a
region
having excellent receiving performance, the difference in performance may be
reduced. At this point, the block processor 403 may also receive additional
information
data, such as signaling information including system information. Herein, the
ad-
ditional information data may also be processed with either 1/2-rate coding or
1/4-rate
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coding as in the step of processing the enhance data.
[44] Thereafter, additional information data, such as signaling information,
is also
considered the same as the mobile service data and processed accordingly. The
signaling information is information required that a receiving system receives
and
processes data included in a data group. The signaling information may include
data
group information, multiplexing information, burst information, and so on.
[45] Meanwhile, the group formatter 404 inserts mobile service data that are
outputted
from the block processor 403 in corresponding regions within a data group,
which is
configured in accordance with a pre-defined rule. Also, with respect to the
data dein-
terleaving process, each place holder or known data are also inserted in
corresponding
regions within the data group. At this point, the data group may be divided
into at least
one hierarchical region. Herein, the type of mobile service data being
inserted to each
region may vary depending upon the characteristics of each hierarchical
region. For
example, each region may be divided based upon the receiving performance
within the
data group.
[46] Herein, the data group is divided into a plurality of different regions
so that each
region can be used for different purposes. More specifically, a region having
less or no
interference from the main service data may provide a more enhanced (or
powerful)
receiving performance as compared to a region having relatively more
interference
from the main service data. Furthermore, when using a system inserting and
transmitting known data into the data group, and when a long known data
sequence is
to be consecutively inserted into the mobile service data, a known data
sequence
having a predetermined length may be consecutively inserted into a region
having no
interference from the main service data. Conversely, in case of the regions
having in-
terference from the main service data, it is difficult to consecutively insert
long known
data sequences and to periodically insert the known data into the
corresponding regions
due to the interference from the main service data.
[47] In addition, the group formatter 404 also inserts supplemental (or
ancillary) data,
such as signaling information that notifies the overall transmission
information, other
than the mobile service data in the data group. Also, apart from the encoded
mobile
service data outputted from the block processor 403, the group formatter 404
also
inserts MPEG header place holders, non-systematic RS parity place holders,
main
service data place holders, which are related to data deinterleaving in a
later process.
Herein, the main service data place holders are inserted because the mobile
service
data bytes and the main service data bytes are alternately mixed with one
another based
upon the input of the data deinterleaver. For example, based upon the data
outputted
after the data-deinterleaving process, the place holder for the MPEG header
may be
allocated at the very beginning of each packet.
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[48] Furthermore, the group formatter 404 either inserts known data generated
in ac-
cordance with a pre-determined method or inserts known data place holders for
inserting the known data in a later process. Additionally, place holders for
initializing
the trellis encoding module 310 are also inserted in the corresponding
regions. For
example, the initialization data place holders may be inserted in the
beginning of the
known data sequence. Herein, the size of the mobile service data that can be
inserted in
a data group may vary in accordance with the sizes of the trellis
initialization data or
known data, MPEG headers, and RS parity data.
[49] The output of the group formatter 404 is inputted to the data
deinterleaver 405. And,
the data deinterleaver 405 deinterleaves data by performing an inverse process
of the
data interleaver on the data and place holders within the data group, which
are then
outputted to the packet formatter 406. The packet formatter 406 removes the
main
service data place holders and the RS parity place holders that were allocated
for the
deinterleaving process from the deinterleaved data being inputted. Then, the
packet
formatter 406 groups the remaining portion and replaces the 4-byte MPEG header
place holder with an MPEG. Also, when the group formatter 404 inserts known
data
place holders, the packet formatter 406 may insert actual known data in the
known data
place holders, or may directly output the known data place holders without any
modi-
fication in order to make replacement insertion in a later process.
Thereafter, the
packet formatter 406 identifies the data within the packet-formatted data
group, as
described above, as a 188-byte unit mobile service data packet (i.e., MPEG TS
packet),
which is then provided to the first multiplexer 304.
[50] The first multiplexer 304 multiplexes the mobile service data packet of
the 188-byte
unit outputted from the packet formatter 406 and the main service data packet
in ac-
cordance with a pre-defined multiplexing method. Then, the first multiplexer
304
outputs the multiplexed data packets to the data randomizer 305. Herein, the
mul-
tiplexing method may vary in accordance with various variables of the system
design.
One of the multiplexing methods of the first multiplexer 304 consists of
providing a
burst-on section and burst-off section along a time axis, as shown in FIG.
5(a), and,
then, transmitting a plurality of data groups during a burst-on section and
transmitting
only the main service data during the burst-off section. At this point, main
service data
may also be transmitted in the burst-on section. More specifically, as shown
in FIG.
5(b), a plurality of consecutive mobile service data packets are grouped to
form a data
group. And, a plurality of such data groups is mixed with main service data
packets so
as to create a burst-on section.
[51] In this case, mobile service data and main service data co-exist in a
burst-on section,
as shown in FIG. 5(a), and only the main service data exist in the burst-off
section.
Therefore, the main service data section transmitting the main service data
exist in both
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the burst-on section and the burst-off section. At this point, the number of
main service
data packets included in the main service data section within the burst-on
section and
the number of main service data packets included in the main service data
section
within the burst-off section may be equal to or different from one another.
When the
mobile service data are transmitted in burst units, as described above, a
receiving
system that only receives the mobile service data may turn on the power only
during
the burst-on section so as to receive the corresponding data. Also, in this
case, the
receiving system may turn off the power during burst-off section, thereby
preventing
the main service data from being received. Thus, the receiving system is
capable of
reducing excessive power consumption.
11521 However, since a data group including mobile service data in-between the
data bytes
of the main service data during the packet multiplexing process, the shifting
of the
chronological position (or place) of the main service data packet becomes
relative.
Also, a system object decoder (i.e., MPEG decoder) for processing the main
service
data of the digital broadcast receiving system, receives and decodes only the
main
service data and recognizes the mobile service data packet as a null data
packet.
Therefore, when the system object decoder of the receiving system receives a
data
group including mobile service data and a main service data packet that is
multiplexed
with the data group, a packet jitter occurs.
11531 At this point, since a multiple-level buffer for the video data exists
in the system
object decoder and the size of the buffer is relatively large, the packet
jitter generated
from the first multiplexer 304 does not cause any serious problem in case of
the video
data. However, since the size of the buffer for the audio data is relatively
small, the
packet jitter may cause considerable problem. More specifically, due to the
packet
jitter, an overflow or underflow may occur in the buffer for the main service
data of the
receiving system (e.g., the buffer for the audio data). Therefore, the packet
jitter
mitigator 302 re-adjusts the relative position of the main service data packet
so that the
overflow or underflow does not occur in the system object decoder.
11541 In the present invention, examples of repositioning places for the audio
data packets
within the main service data in order to minimize the influence on the
operations of the
audio buffer will be described in detail. FIG. 5(c) illustrates, in TS packet
units, a main
service data section within the burst-on section that is being inputted to the
packet jitter
mitigator 302 of the transmitter. The packet jitter mitigator 302 repositions
audio
packets of the main service data section, as shown in FIG. 5(d), so that the
audio data
packets of the main service can be positioned as equally and uniformly as
possible.
The standard for repositioning the audio data packets in the main service data
performed by the packet jitter mitigator 302 will now be described. Herein, it
is
assumed that the packet jitter mitigator 302 knows the same multiplexing
information
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as that of the first multiplexer 304, which is placed further behind the
packet jitter
mitigator 302.
1551 Firstly, if one audio data packet exists in the main service data section
(e.g., the main
service data section positioned between two data groups) within the burst-on
section,
the audio data packet is positioned at the very beginning of the main service
data
section. Alternatively, if two audio data packets exist in the corresponding
data section,
one audio data packet is positioned at the very beginning and the other audio
data
packet is positioned at the very end of the main service data section.
Further, if more
than three audio data packets exist, one audio data packet is positioned at
the very
beginning of the main service data section, another is positioned at the very
end of the
main service data section, and the remaining audio data packets are positioned
between
the first and last audio data packets at equal intervals (as shown in FIG.
5(c) and FIG.
5(d)).
1561 Secondly, during the main service data section within the burst-off
section, which is
placed immediately before the beginning of a burst-on section (i.e., during a
burst-off
section), the audio data packet is placed at the very end of the main service
data
section. Thirdly, during a main service data section within the burst-off
section
subsequent to the burst-on section, the audio data packet is positioned at the
very
beginning of the main service data section. And, finally, the data packets
other than
audio data packets are positioned in accordance with the inputted order in
vacant
spaces (i.e., spaces that are not designated for the audio data packets).
Meanwhile,
when the positions of the main service data packets are relatively re-
adjusted, as-
sociated program clock reference (PCR) values may also be modified
accordingly. The
PCR value corresponds to a time reference value for synchronizing the time of
the
system target decoder. Herein, the PCR value is inserted in a specific region
of a TS
packet and then transmitted.
1571 In the example of the present invention, the packet jitter mitigator 302
also performs
the operation of modifying the PCR value. The output of the packet jitter
mitigator 302
is inputted to the first multiplexer 304. As described above, the first
multiplexer 304
multiplexes the main service data packet outputted from the packet jitter
mitigator 302
with the mobile service data packet outputted from the pre-processor 303 into
a burst
structure in accordance with a pre-determined multiplexing rule. Then, the
first mul-
tiplexer 304 outputs the multiplexed data packets to the data randomizer 305.
1581 If the inputted data correspond to the main service data packet, the data
randomizer
305 performs the same randomizing process as that of the conventional
randomizer.
More specifically, the synchronization byte within the main service data
packet is
deleted. Then, the remaining 187 data bytes are randomized by using a pseudo
random
byte generated from the data randomizer 305. Thereafter, the randomized data
are
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outputted to the RS encoder/non-systematic RS encoder 306.
[59] On the other hand, if the inputted data correspond to the mobile service
data packet,
the data randomizer 305 deletes the synchronization byte from the 4-byte MPEG
header included in the mobile service data packet and, then, performs the
randomizing
process only on the remaining 3 data bytes of the MPEG header. Thereafter, the
randomized data bytes are outputted to the RS encoder/non-systematic RS
encoder
306. Additionally, the randomizing process is not performed on the remaining
portion
of the mobile service data excluding the MPEG header. In other words, the
remaining
portion of the mobile service data packet is directly outputted to the RS
encoder/
non-systematic RS encoder 306 without being randomized. This is because a ran-
domizing process has already been performed on the mobile service data in the
data
randomizer 401. Also, the data randomizer 305 may or may not perform a
randomizing
process on the known data (or known data place holders) and the initialization
data
place holders included in the mobile service data packet.
[60] The RS encoder/non-systematic RS encoder 306 performs an RS encoding
process
on the data being randomized by the data randomizer 305 or on the data
bypassing the
data randomizer 305, so as to add 20 bytes of RS parity data. Thereafter, the
processed
data are outputted to the data interleaver 307. Herein, if the inputted data
correspond to
the main service data packet, the RS encoder/non-systematic RS encoder 306
performs
the same systematic RS encoding process as that of the conventional system,
thereby
adding the 20-byte RS parity data at the end of the 187-byte data.
Alternatively, if the
inputted data correspond to the mobile service data packet, the RS encoder/
non-systematic RS encoder 306 performs a non-systematic RS encoding process.
At
this point, the 20-byte RS parity data obtained from the non-systematic RS
encoding
process are inserted in a pre-decided parity byte place within the mobile
service data
packet.
[61] The data interleaver 307 corresponds to a byte unit convolutional
interleaver. The
output of the data interleaver 307 is inputted to the parity replacer 308 and
to the non-
systematic RS encoder 309. Meanwhile, a process of initializing a memory
within the
trellis encoding module 310 is primarily required in order to decide the
output data of
the trellis encoding module 310, which is located after the parity replacer
308, as the
known data pre-defined according to an agreement between the receiving system
and
the transmitting system. More specifically, the memory of the trellis encoding
module
310 should first be initialized before the received known data sequence is
trellis-
encoded.
[62] At this point, the beginning portion of the known data sequence that is
received cor-
responds to the initialization data place holder and not to the actual known
data.
Herein, the initialization data place holder has been included in the data by
the group
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formatter 404 in an earlier process. Therefore, the process of generating
initialization
data and replacing the initialization data place holder of the corresponding
memory
with the generated initialization data are required to be performed
immediately before
the inputted known data sequence is trellis-encoded.
[63] Additionally, a value of the trellis memory initialization data is
decided and
generated based upon a memory status of the trellis encoding module 310.
Further, due
to the newly replaced initialization data, a process of newly calculating the
RS parity
and replacing the RS parity, which is outputted from the data interleaver 307,
with the
newly calculated RS parity is required. Therefore, the non-systematic RS
encoder 309
receives the mobile service data packet including the initialization data
place holders,
which are to be replaced with the actual initialization data, from the data
interleaver
307 and also receives the initialization data from the trellis encoding module
310.
[64] Among the inputted mobile service data packet, the initialization data
place holders
are replaced with the initialization data, and the RS parity data that are
added to the
mobile service data packet. Thereafter, a new non-systematic RS parity is
calculated
and then outputted to the parity replacer 308. Accordingly, the parity
replacer 308
selects the output of the data interleaver 307 as the data within the mobile
service data
packet, and the parity replacer 308 selects the output of the non-systematic
RS encoder
309 as the RS parity data. Then, the selected data are outputted to the
trellis encoding
module 310.
[65] Meanwhile, if the main service data packet is inputted or if the mobile
service data
packet, which does not include any initialization data place holders that are
to be
replaced, is inputted, the parity replacer 308 selects the data and RS parity
that are
outputted from the data interleaver 307. Then, the parity replacer 308
directly outputs
the selected data to the trellis encoding module 310 without any modification.
The
trellis encoding module 310 converts the byte-unit data to symbol units and
performs a
12-way interleaving process so as to trellis-encode the received data.
Thereafter, the
processed data are outputted to the second multiplexer 311.
[66] The second multiplexer 311 inserts a field synchronization signal and a
segment syn-
chronization signal to the data outputted from the trellis encoding module 310
and,
then, outputs the processed data to the pilot inserter 312. Herein, the data
having a pilot
inserted by the pilot inserter 312 are modulated by the modulator 313 in
accordance
with a pre-decided modulating method. Thereafter, the modulated data are
transmitted
to each receiving system through the radio frequency (RF) up-converter 314.
[67] FIG. 6 illustrates a block diagram showing a structure of a receiving
system
according to the present invention. The receiving system of FIG. 6 uses known
data in-
formation, which is inserted in the mobile service data section and, then,
transmitted by
the transmitting system, so as to perform carrier synchronization recovery,
frame syn-
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chronization recovery, and channel equalization, thereby enhancing the
receiving per-
formance. Referring to FIG. 6, the receiving system includes a tuner 601, a de-
modulator 602, an equalizer 603, a known sequence detector 604, a block
decoder 605,
a data deformatter 606, a RS frame decoder 607, a data derandomizer 608, a
data dein-
terleaver 609, a RS decoder 610, and a data derandomizer 611. Herein, for
simplicity
of the description of the present invention, the data deformatter 606, the RS
frame
decoder 607, and the data derandomizer 608 will be collectively referred to as
a mobile
service data processing unit. And, the data deinterleaver 609, the RS decoder
610, and
the data derandomizer 611 will be collectively referred to as a main service
data
processing unit.
[68] More specifically, the tuner 601 tunes a frequency of a particular
channel and down-
converts the tuned frequency to an intermediate frequency (IF) signal. Then,
the tuner
601 outputs the down-converted IF signal to the demodulator 602 and the known
sequence detector 604. The demodulator 602 performs self gain control, carrier
recovery, and timing recovery processes on the inputted passband IF signal,
thereby
modifying the IF signal to a baseband signal. Then, the demodulator 602
outputs the
newly created baseband signal to the equalizer 603 and the known sequence
detector
604. The equalizer 603 compensates the distortion of the channel included in
the de-
modulated signal and then outputs the error-compensated signal to the block
decoder
605.
[69] At this point, the known sequence detector 604 detects the known sequence
place
inserted by the transmitting end from the input/output data of the demodulator
602 (i.e.
, the data prior to the demodulation process or the data after the
demodulation process).
Thereafter, the place information along with the symbol sequence of the known
data,
which are generated from the detected place, is outputted to the demodulator
602 and
the equalizer 603. Also, the known sequence detector 604 outputs a set of
information
to the block decoder 605. This set of information is used to allow the block
decoder
605 of the receiving system to identify the mobile service data that are
processed with
additional encoding from the transmitting system and the main service data
that are not
processed with additional encoding. In addition, although the connection
status is not
shown in FIG. 6, the information detected from the known sequence detector 604
may
be used throughout the entire receiving system and may also be used in the
data de-
formatter 606 and the RS frame decoder 607. The demodulator 602 uses the known
data symbol sequence during the timing and/or carrier recovery, thereby
enhancing the
demodulating performance. Similarly, the equalizer 603 uses the known data so
as to
enhance the equalizing performance. Moreover, the decoding result of the block
decoder 605 may be fed-back to the equalizer 603, thereby enhancing the
equalizing
performance.
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[70] Meanwhile, if the data being inputted to the block decoder 605, after
being channel-
equalized by the equalizer 603, correspond to the mobile service data having
additional
encoding and trellis encoding performed thereon by the transmitting system,
trellis
decoding and additional decoding processes are performed on the inputted data
as
inverse processes of the transmitting system. Alternatively, if the data being
inputted to
the block decoder 605 correspond to the main service data having only trellis
encoding
performed thereon, and not the additional encoding, only the trellis decoding
process is
performed on the inputted data as the inverse process of the transmitting
system. The
data group decoded by the block decoder 605 is outputted to the data
deformatter 606,
and the main service data are outputted to the data deinterleaver 609.
[71] More specifically, if the inputted data correspond to the main service
data, the block
decoder 605 performs Viterbi decoding on the inputted data so as to output a
hard
decision value or to perform a hard-decision on a soft decision value, thereby
outputting the result. Meanwhile, if the inputted data correspond to the
mobile service
data, the block decoder 605 outputs a hard decision value or a soft decision
value with
respect to the inputted mobile service data. In other words, if the inputted
data
correspond to the mobile service data, the block decoder 605 performs a
decoding
process on the data encoded by the block processor and trellis encoding module
of the
transmitting system.
[72] At this point, the RS frame encoder of the pre-processor included in the
transmitting
system may be viewed as an external code. And, the block processor and the
trellis
encoder may be viewed as an internal code. In order to maximize the
performance of
the external code when decoding such concatenated codes, the decoder of the
internal
code should output a soft decision value. Therefore, the block decoder 605 may
output
a hard decision value on the mobile service data. However, when required, it
may be
more preferable for the block decoder 605 to output a soft decision value.
[73] Meanwhile, the data deinterleaver 609, the RS decoder 610, and the data
de-
randomizer 611 are blocks required for receiving the main service data.
Therefore, the
above-mentioned blocks may be omitted from the structure of a receiving system
that
only receives the mobile service data. The data deinterleaver 609 performs an
inverse
process of the data interleaver included in the transmitting system. In other
words, the
data deinterleaver 609 deinterleaves the main service data outputted from the
block
decoder 605 and outputs the deinterleaved main service data to the RS decoder
610.
[74] The RS decoder 610 performs a systematic RS decoding process on the
deinterleaved
data and outputs the processed data to the data derandomizer 611. The data de-
randomizer 611 receives the output of the RS decoder 610 and generates a
pseudo
random data byte identical to that of the randomizer included in the
transmitting
system. Thereafter, the data derandomizer 611 performs a bitwise exclusive OR
(XOR)
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operation on the generated pseudo random data byte, thereby inserting the MPEG
syn-
chronization bytes to the beginning of each packet so as to output the data in
188-byte
main service data packet units.
[75] Meanwhile, the data being outputted from the block decoder 605 to the
data de-
formatter 606 are inputted in the form of a data group. At this point, the
data de-
formatter 606 already knows the structure of the data that are to be inputted
and is,
therefore, capable of identifying the signaling information, which includes
the system
information, and the mobile service data from the data group. Thereafter, the
data de-
formatter 606 outputs the identified signaling information to a block for
processing
signaling information (not shown) and outputs the identified mobile service
data to the
RS frame decoder 607. At this point, the data deformatter 606 removes the
known
data, trellis initialization data, and MPEG header, which were inserted in the
main
service data and data group, and also removes the RS parity, which was added
by the
RS encoder/non-systematic RS encoder or non-systematic RS encoder of the
transmitting system, from the corresponding data. Thereafter, the processed
data are
outputted to the RS frame decoder 607. More specifically, the RS frame decoder
607
receives only the RS encoded and/or CRC encoded mobile service data that are
transmitted from the data deformatter 606.
[76] The RS frame decoder 607 performs an inverse process of the RS frame
encoder
included in the transmitting system so as to correct the error within the RS
frame.
Then, the RS frame decoder 607 adds the 1-byte MPEG synchronization service
data
packet, which had been removed during the RS frame encoding process, to the
error-
corrected mobile service data packet. Thereafter, the processed data packet is
outputted
to the data derandomizer 608. The data derandomizer 608 performs a
derandomizing
process, which corresponds to the inverse process of the randomizer included
in the
transmitting system, on the received mobile service data. Thereafter, the
derandomized
data are outputted, thereby obtaining the mobile service data transmitted from
the
transmitting system.
[77] It will be apparent to those skilled in the art that various
modifications and variations
can be made in the present invention without departing from the spirit or
scope of the
inventions. Thus, it is intended that the present invention covers the
modifications and
variations of this invention provided they come within the scope of the
appended
claims and their equivalents.
