U.S. patent application number 12/262728 was filed with the patent office on 2009-04-23 for digital broadcast transmitter/receiver having an improved receiving performance and signal processing method thereof.
This patent application is currently assigned to Samsung Electronics Co., Ltd.. Invention is credited to Jin-hee Jeong, Kum-ran Ji, Jong-hun Kim, Joon-soo Kim, Yong-sik Kwon, Eui-jun Park, Jung-pil Yu.
Application Number | 20090106813 12/262728 |
Document ID | / |
Family ID | 38067419 |
Filed Date | 2009-04-23 |
United States Patent
Application |
20090106813 |
Kind Code |
A1 |
Park; Eui-jun ; et
al. |
April 23, 2009 |
DIGITAL BROADCAST TRANSMITTER/RECEIVER HAVING AN IMPROVED RECEIVING
PERFORMANCE AND SIGNAL PROCESSING METHOD THEREOF
Abstract
A digital broadcast transmitting/receiving system, and a signal
processing method thereof, includes a randomizer for randomizing a
transport stream into a specified position of which stuff bytes are
inserted, a stuff-byte exchanger for replacing the stuff bytes
included in data output from the randomizer with specified known
data, an RS encoder for performing an RS-encoding of data output
from the stuff-byte exchanger, an interleaver for interleaving data
output from the RS encoder, a trellis encoder for performing a
trellis encoding of data output from the interleaver, an RS parity
generator for generating a parity by performing an RS encoding of
data output from the RS encoder, and outputting the generated
parity to the trellis encoder, and a modulator/RF converter for
modulating data output from the trellis encoder and performing an
RF up-converting of the modulated data. The digital broadcast
receiving performance can be improved even in an inferior
multi-path channel by detecting the known data from the received
signal and using the known data for synchronization and
equalization in a digital broadcast receiver.
Inventors: |
Park; Eui-jun; (Seoul,
KR) ; Kwon; Yong-sik; (Seoul, KR) ; Kim;
Joon-soo; (Seoul, KR) ; Yu; Jung-pil;
(Suwon-si, KR) ; Jeong; Jin-hee; (Anyang-si,
KR) ; Ji; Kum-ran; (Seoul, KR) ; Kim;
Jong-hun; (Suwon-si, KR) |
Correspondence
Address: |
STEIN, MCEWEN & BUI, LLP
1400 EYE STREET, NW, SUITE 300
WASHINGTON
DC
20005
US
|
Assignee: |
Samsung Electronics Co.,
Ltd.
Suwon-si
KR
|
Family ID: |
38067419 |
Appl. No.: |
12/262728 |
Filed: |
October 31, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11475098 |
Jun 27, 2006 |
|
|
|
12262728 |
|
|
|
|
60739430 |
Nov 25, 2005 |
|
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Current U.S.
Class: |
725/151 |
Current CPC
Class: |
H04N 21/2383 20130101;
H04N 21/4346 20130101; H04H 60/07 20130101; H04N 21/23611 20130101;
H03M 13/2936 20130101; H04N 21/4382 20130101; H04L 25/03286
20130101; H04L 1/0065 20130101; H03M 13/253 20130101 |
Class at
Publication: |
725/151 |
International
Class: |
H04N 7/16 20060101
H04N007/16 |
Claims
1. A digital broadcast receiver, comprising: a tuner to receive a
stream; a demodulator to demodulate the refeived stream; and an
equalizer to equalize the demodulated stream, wherein the stream is
transmitted from a digital broadcast transmitter comprising a
trellis encoder which comprises: a first memory, a first
multiplexer (MUX) to output one of an input signal and a stored
value retrieved from the first memory by the first MUX according to
a control signal, a first adder to add the value stored in the
first memory and the output one of the input signal and the
retrieved from the first memory output by the first MUX according
to the control signal, a second memory, a third memory to be
connected to the second memory to store a value shifted from the
second memory, a second MUX to output one of another input signal
and the value stored in the third memory according to the control
signal, and a second adder to add the value stored in the third
memory and the output one of the another input signal and the value
stored in the third memory, and provide the second memory with the
added value.
2. The digital broadcast receiver as claimed in claim 1, further
comprising: a decoder to decode the equalized stream; a
deinterleaver to rearrange the decoded stream; and an RS decoder to
perform RS decoding of the rearranged stream.
3. The digital broadcast receiver as claimed in claim 2, further
comprising: a controller to provide the equalizer with known data
included in the stream.
4. A signal processing method for a digital broadcast receiver, the
method comprising: receiving a stream; demodulating the received
stream; and equalizing the demodulated stream, wherein the stream
is transmitted from a digital broadcast transmitter comprising: a
first memory, a first multiplexer (MUX) to output one of an input
signal and a stored value retrieved from the first memory according
to a control signal, a first adder to add the value stored in the
first memory and an output one of the input signal and the stored
value output by the first MUX, a second memory, a third memory to
store a value shifted from the second memory, a second MUX to
output one of another input signal and the value stored in the
third memory according to the control signal, and a trellis encoder
including a second adder to add the value stored in the third
memory and an output one of the another input signal and the stored
value output by the second MUX and provide the second memory with
the added value.
5. The signal processing method as claimed in claim 4, further
comprising: decoding the equalized stream; rearranging the decoded
stream; and performing RS decoding of the rearranged stream.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/475,098, filed Jun. 27, 2006, currently
pending, which claims priority from U.S. Provisional Patent
Application No. 60/739,430, filed on Nov. 25, 2005 in the United
States Patent and Trademark Office, the disclosures of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Aspects of the present invention relate to a digital
broadcast transmitter/receiver and a signal processing method
thereof, and more particularly to a digital broadcast
transmitter/receiver and a signal processing method thereof which
can improve the receiving performance of the system by inserting a
known sequence (also referred to as a "supplementary reference
sequence (SRS)") into a VSB (Vestigial Side Band) data stream and
transmitting the data stream with the inserted known sequence.
[0004] 2. Description of the Related Art
[0005] An ATSC (Advanced Television Systems Committee) VSB system
that is an American-type digital terrestrial broadcasting system is
a signal carrier type broadcasting system, and uses a field sync
signal in the unit of 312 segments. FIG. 1 is a block diagram
illustrating the construction of a transmitter/receiver of an ATSC
DTV standard as a general American-type digital terrestrial
broadcasting system.
[0006] The digital broadcast transmitter of FIG. 1 includes a
randomizer 110 for randomizing Moving Picture Experts Group-2
(MPEG-2) transport stream (TS), and a Reed-Solomon (RS) encoder 120
for adding RS parity bytes to the transport stream in order to
correct bit errors occurring due to the channel characteristic in a
transport process. An interleaver 130 interleaves the RS-encoded
data according to a specified pattern. A trellis encoder 140 maps
the interleaved data onto 8-level symbols by performing a trellis
encoding of the interleaved data at the rate of 2/3. The digital
broadcast transmitter performs an error correction coding of the
MPEG-2 transport stream.
[0007] The digital broadcast transmitter further includes a
multiplexer 150 for inserting a segment sync signal and a field
sync signal into the error-correction-coded data. A modulator/RF
converter 160 inserts a pilot tone into the data symbols into which
the segment sync signal and the field sync signal are inserted by
inserting specified DC values into the data symbols, performs a VSB
modulation of the data symbols by pulse-shaping the data symbols,
and up-converts the modulated data symbols into an RF channel band
signal to transmit the RF channel band signal. Accordingly, the
digital broadcast transmitter randomizes the MPEG-2 transport
stream, outer-codes the randomized data through the RS encoder 120
that is an outer coder, and distributes the coded data through the
interleaver 130. Also, the digital broadcast transmitter
inner-codes the interleaved data in the unit of 12 symbols through
the trellis encoder 140, performs the mapping of the inner-coded
data onto the 8-level symbols, inserts the field sync signal and
the segment sync signal into the coded data, performs the VSB
modulation of the data, and then up-converts the modulated data
into the RF signal to output the RF signal.
[0008] Meanwhile, the digital broadcast receiver of FIG. 1 includes
a tuner (not shown) for down-converting an RF signal received
through a channel into a baseband signal, and a demodulator 210 for
performing a sync detection and demodulation of the converted
baseband signal. An equalizer 220 compensates for a channel
distortion of the demodulated signal occurring due to a multi-path.
A Viterbi decoder 230 corrects errors of the equalized signal and
decodes the equalized signal to symbol data. A deinterleaver 250
rearranges the data distributed by the interleaver 130 of the
digital broadcast transmitter. An RS decoder 250 corrects errors,
and a derandomizer 260 de-randomizes the data corrected through the
RS decoder 250 and outputs an MPEG-2 transport stream.
[0009] Accordingly, the digital broadcast receiver of FIG. 1
down-converts the RF signal into the baseband signal, demodulates
and equalizes the converted signal, and then channel-decodes the
demodulated signal to restore to the original signal.
[0010] FIG. 2 illustrates a VSB data frame for use in the American
type digital broadcasting (8-VSB) system, into which a segment sync
signal and a field sync signal are inserted. As shown in FIG. 2,
one frame is composed of two fields. One field is composed of one
field sync segment that is the first segment and 312 data segments.
Also, one data segment in the VSB data frame corresponds to one
MPEG-2 packet, and is composed of a segment sync signal of four
symbols and 828 data symbols.
[0011] In FIG. 2, the segment sync signal and the field sync signal
are used for the synchronization and equalization in the digital
broadcast receiver. That is, the field sync signal and the segment
sync signal refer to known data between the digital broadcast
transmitter and receiver, which is used as a reference signal when
the equalization is performed in the receiver side.
[0012] As shown in FIG. 1, the VSB system of the American type
digital terrestrial broadcasting system is a single carrier system.
Thus, the system has the drawback in that it is weak in a
multi-path fading channel environment having the Doppler effect.
Accordingly, the performance of the receiver is greatly influenced
by the performance of the equalizer for removing the multi-path
fading.
[0013] However, according to the existing transport frame as shown
in FIG. 2, since the field sync signal that is the reference signal
of the equalizer 220 appears once for every 313 segments, its
frequency is quite low with respect to one frame signal, and this
causes the performance of equalization to deteriorate.
Specifically, it is not easy for the existing equalizer 220 to
estimate the channel using a small amount of data as above and to
equalize the received signal by removing the multi-path fading.
Accordingly, the conventional digital broadcast receiver has the
disadvantages that its receiving performance deteriorates in an
inferior channel environment, and especially in a Doppler fading
channel environment.
SUMMARY OF THE INVENTION
[0014] An aspect of the present invention is to provide a digital
broadcast transmitter/receiver and a signal processing method
thereof that can improve the receiving performance of the system by
generating and transmitting a transport signal with known data
added thereto in a transmitter side and by detecting the transport
signal in a receiver side.
[0015] Additional aspects and/or advantages of the invention will
be set forth in part in the description which follows and, in part,
will be obvious from the description, or may be learned by practice
of the invention.
[0016] According to an aspect of the present invention, a
transmitter comprises a randomizer for randomizing a transport
stream into a specified position of which stuff bytes are inserted,
a stuff-byte exchanger for replacing the stuff bytes included in
data output from the randomizer with specified known data, an RS
encoder for performing an RS-encoding of data output from the
stuff-byte exchanger, an interleaver for interleaving data output
from the RS encoder, a trellis encoder for performing a trellis
encoding of data output from the interleaver, an RS parity
generator for generating a parity by performing an RS encoding of
data output from the RS encoder, and outputting the generated
parity to the trellis encoder, and a modulator/RF converter for
modulating data output from the trellis encoder and performing an
RF up-converting of the modulated data.
[0017] According to an aspect of the invention, the trellis encoder
includes a memory for performing the trellis encoding, and performs
a memory initialization with respect to data input in the position
into which the stuff bytes are inserted.
[0018] According to an aspect of the invention, the trellis encoder
outputs a value for initializing the memory to the RS parity
generator, receives the parity generated by the RS parity
generator, and replaces a corresponding parity by the received
parity.
[0019] According to an aspect of the invention, the digital
broadcast transmitter further includes a controller for generating
a control signal that indicates information about the position into
which the stuff bytes are inserted, and controlling the memory
initialization of the trellis encoder.
[0020] According to an aspect of the invention, the controller
transmits position information of the stuff bytes and the known
data to be replaced in the corresponding position to the stuff-byte
exchanger, and transmits position information of an initialization
packet to the RS parity generator.
[0021] According to an aspect of the invention, the RS parity
generator includes a packet buffer for temporarily storing a packet
that includes an initialization area output from the RS
encoder.
[0022] According to an aspect of the invention, the packet buffer
receives and updates data changed according to the memory
initialization.
[0023] According to an aspect of the invention, the RS parity
generator further includes a byte mapper for mapping initialization
symbols output from the trellis encoder with specified bytes, and
outputting the mapped symbols to the packet buffer, an RS encoder
for performing an RS encoding of data output from the packet
buffer, and a symbol mapper for converting an output of the RS
encoder into specified symbols.
[0024] According to an aspect of the invention, the stuff bytes are
inserted into an adaptation field of the transport stream.
[0025] According to an aspect of the invention, the information
about a position and a length of the stuff bytes is inserted in a
specified position of the transport stream.
[0026] In another aspect of the present invention, there is
provided a signal transmission method for a digital broadcast
transmitter, which comprises randomizing a transport stream into a
specified position of which stuff bytes are inserted, replacing the
stuff bytes in the randomized data with specified known data,
performing an RS-encoding of data having the replaced stuff bytes,
interleaving the RS encoded data, performing a trellis encoding of
the interleaved data, generating a parity by performing an RS
encoding of the RS encoded data, and outputting the generated
parity for use in the trellis encoding, and modulating the trellis
encoded data and performing an RF up-converting of the modulated
data.
[0027] In still another aspect of the present invention, there is
provided a digital broadcast receiver, which comprises a
demodulator for receiving and demodulating a signal encoded by
inserting specified known data into stuff bytes inserted into a
specified position, an equalizer for equalizing the demodulated
signal, a Viterbi decoder for error-correcting and decoding the
equalized signal, a deinterleaver for deinterleaving output data of
the Viterbi decoder, and a derandomizer for performing a
derandomization of output data of the deinterleaver.
[0028] In still another aspect of the present invention, there is
provided a trellis encoder for a digital broadcast transmitter that
transmits transport stream formed by replacing stuff bytes inserted
into a specified position with specified known data, the trellis
encoder comprising a memory for performing a trellis encoding, and
performing a memory initialization with respect to data input in a
position into which the stuff bytes are inserted.
[0029] In still another aspect of the present invention, there is
provided a digital broadcast transmitter, which comprises a
randomizer for randomizing a transport stream into a specified
position of which stuff bytes are inserted, a stuff-byte exchanger
for replacing the stuff bytes included in data output from the
randomizer with specified known data, an RS encoder for performing
an RS-encoding of data output from the stuff-byte exchanger, an
interleaver for interleaving data output from the RS encoder, a
trellis encoder, including a memory, for performing a memory
initialization with respect to data input in a position into which
the stuff bytes are inserted, and performing a trellis encoding of
data output from the interleaver; an RS parity generator for
receiving a value for initializing the memory, generating a parity,
and outputting the generated parity to the trellis encoder, and a
modulator/RF converter for modulating data output from the trellis
encoder and performing an RF up-converting of the modulated
data.
[0030] In still another aspect of the present invention, there is
provided a signal processing method for a digital broadcast
transmitter, which comprises randomizing a transport stream into a
specified position of which stuff bytes are inserted, replacing the
stuff bytes in data output in the randomization with specified
known data, performing an RS-encoding of data output in the
stuff-byte replacing, interleaving data output in the RS encoding,
performing a trellis encoding of data output in the interleaving
and performing a memory initialization with respect to data input
in a position into which the stuff bytes are inserted, performing
RS parity generation by receiving a value for initializing the
memory, generating a parity, and outputting the generated parity
for the trellis encoding, and modulating data output in the trellis
encoding and performing an RF up-converting of the modulated
data.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] These and/or other aspects and advantages of the invention
will become apparent and more readily appreciated from the
following description of the embodiments, taken in conjunction with
the accompanying drawings of which:
[0032] FIG. 1 is a block diagram illustrating the construction of a
transmitting/receiving system of a general American-type digital
broadcasting (ATSC VSB) system;
[0033] FIG. 2 is a view illustrating the structure of an ATSC VSB
data frame;
[0034] FIG. 3 is a view illustrating the structure of a general
MPEG-2 transport stream packet;
[0035] FIG. 4 is a view illustrating the structure of an MPEG-2
transport stream packet that includes an adaptation field according
to the present invention;
[0036] FIG. 5a to 5e are views illustrating diverse formats of an
MPEG-2 transport stream packet that includes an adaptation field to
which stuff bytes are added according to aspects of the present
invention;
[0037] FIG. 6 is a block diagram illustrating the construction of a
digital broadcast transmitter according to an embodiment of the
present invention;
[0038] FIG. 7 is a view illustrating the construction of a trellis
encoder of a digital broadcast transmitter according to an
embodiment of the present invention;
[0039] FIG. 8 is a block diagram illustrating the construction of
an RS parity generator of a digital broadcast transmitter according
to an embodiment of the present invention;
[0040] FIG. 9 is a block diagram illustrating an example of an RS
parity generator of a digital broadcast transmitter according to an
embodiment of the present invention;
[0041] FIG. 10 is a view explaining an SRS area of an interleaver
according to an aspect of the present invention;
[0042] FIG. 11 is a view illustrating an input frame of an
interleaver according to an aspect of the present invention;
[0043] FIG. 12 is a view illustrating an output frame of an
interleaver according to an aspect of the present invention;
[0044] FIG. 13 is a view illustrating an input frame of a repeated
structure of an interleaver according to an aspect of the present
invention;
[0045] FIG. 14 is a view illustrating an input frame of a
stuff-byte exchanger according to an aspect of the present
invention;
[0046] FIG. 15 is a block diagram illustrating the construction of
a digital broadcast receiver according to an embodiment of the
present invention;
[0047] FIG. 16 is a block diagram illustrating the construction of
a digital broadcast transmitter according to another embodiment of
the present invention;
[0048] FIG. 17 is a view illustrating the construction of a trellis
encoder used in the transmitter of FIG. 16 according to an aspect
of the invention.
[0049] FIG. 18 is a flowchart provided to explain the operation of
a digital broadcast transmitter according to an embodiment of the
present invention; and
[0050] FIG. 19 is a flowchart provided to explain the operation of
a digital broadcast receiver according to an embodiment of the
present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0051] Reference will now be made in detail to the present
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings, wherein like reference
numerals refer to the like elements throughout. The embodiments are
described below in order to explain the present invention by
referring to the figures. Also, well-known functions or
constructions are not described in detail since they would obscure
the invention in unnecessary detail.
[0052] FIG. 3 is a view illustrating the structure of a general
MPEG-2 transport stream packet. Referring to FIG. 3, the general
MPEG-2 transport stream is composed of a TS header part of 4 bytes,
and an adaptation field or payload data of 184 bytes. As shown, TS
header part includes an 8 bit sync byte, a 1 bit transport error
indicator, a 1 bit payload start indicator, a 1 bit transport
priority indicator, a 13 bit packet identifier (PID), a 2 bit
transport scrambling control, a 2 bit adaptation field control, and
a 4 bit continuity counter.
[0053] FIG. 4 is a view illustrating the structure of an MPEG-2
transport stream packet that includes an adaptation field to which
stuff bytes are added according to an aspect of the present
invention. Referring to FIG. 4, the MPEG-2 transport stream
includes a header part of 4 bytes, an adaptation field of "n"
bytes, and payload data of "184-n" bytes. Two bytes of the
adaptation field include an adaptation field header (AF header)
including information about the length of the adaptation field.
Stuff bytes that simply occupy a space without containing
information may be inserted after the adaptation field header. The
existence/nonexistence of the adaptation field is determined by the
value of an adaptation field control bit in a TS header of the
transport stream. Also shown is at 8 bit etc indicator or flag.
[0054] In an aspect of the present invention, an MPEG-2 TS packet
in which stuff bytes are inserted into an adaptation field of a
transport stream such as a data format as illustrated in FIG. 4 is
used as an input of a transmitter. FIGS. 5a to 5e are views
illustrating diverse formats of an MPEG-2 transport stream into
which a supplementary reference sequence (SRS) is to be inserted in
order to implement the transmitter according to aspects of the
present invention. Here, for convenience in explanation, three
bytes after a sync byte of the transport stream are called a normal
header, first two types of the adaptation field are called an
adaptation field (AF) header.
[0055] Generally, the SRS is a special known sequence in a
deterministic VSB frame that is inserted in such a way that a
receiver equalizer can utilize this known sequence to mitigate
dynamic multi-path and other adverse channel conditions. The
equalizer uses these contiguous sequences to adapt itself to a
dynamically changing channel. When the encoder states have been
forced to a known Deterministic State (DTR) an appended
pre-calculated "known sequence" of bits (SRS pattern) is then
processed immediately in pre-determined way at specific temporal
locations at the Interleaver input of the frame. The resulting
symbols, at the Interleaver output, due to the way the ATSC
Interleaver functions will appear as known contiguous symbol
patterns in known locations in VSB frame, which is available to the
receiver as additional equalizer training sequence. The data to be
used in transport stream packets to create these known symbol
sequence is introduced into the system in a backward compatible way
using existing standard mechanisms. This data is carried in the
MPEG2 adaptation field. Hence existing standards are leveraged, and
compatibility is assured.
[0056] The RS Encoder preceding the Interleaver calculates the RS
parity. Due to resetting Trellis Coder Memory (TCM) encoders, the
calculated RS Parity bytes are wrong and need to be corrected. Thus
an additional processing step is involved to correct parity errors
in selected packets. All packets with parity errors will have their
RS parity re-encoded. A (52) segment byte interleaver with unique
time dispersion properties, that generates contiguous SRS pattern
is leveraged to have adequate time to re-encode parity bytes.
Required time to do this constraints the maximum number of SRS
bytes.
[0057] FIG. 5a shows the structure of an MPEG-2 packet data of a
basic form in a VSB system using the SRS data as a training
sequence. This MPEG-2 packet data includes a normal header part
(such as that shown in FIG. 3 and FIG. 4) composed of a one-byte
sync signal and a three-byte PID (Packet Identity), a two-byte
adaptation field (AF) header including information about the
position of the stuff bytes, and stuff bytes of a specified length
N. The remaining bytes of the packet data correspond to a normal
stream that is typical payload data. Since the start position of
the stuff bytes is fixed, the information about the byte position
is expressed by information about the length of the stuff bytes.
The stuff-byte length N may be in the range of 1 to 27. However, if
the start position is not fixed, it is understood that start
position information would be used.
[0058] FIGS. 5b to 5e illustrate packet structures having
adaptation fields in which other information, such as a program
clock reference (PCR), an original program clock reference (OPCR),
a splice countdown (splice_count), and the like, are included in
order to effectively use the SRS. In these cases, the adaptation
field is constructed to have a uniform size. A part except for the
AF header and information such as PCR, OPCR, splice-count, and
others, corresponds to the stuff bytes to which the SRS is to be
inserted.
[0059] FIG. 6 is a block diagram illustrating the construction of a
digital broadcast transmitting system according to an embodiment of
the present invention. Referring to FIG. 6, the digital broadcast
transmitter includes a randomizer 610, a stuff-byte exchanger 620,
an RS encoder 630, an interleaver 640, a trellis encoder 650, an RS
parity generator 660, a multiplexer 670, and a controller 680.
[0060] The randomizer 610 randomizes an input MPEG-2 transport
steam data in order to heighten the utility of an allocated channel
space. The data input to the randomizer 610 has the data format
formed by inserting stuff bytes, which have a specified length of
bytes, but does not include payload data as shown in FIGS. 5a to
5e, into a specified position of the input transport stream data.
The payload data includes audio and/or video data, and can further
include non AV data in other aspects of the invention.
[0061] The stuff-byte exchanger 620 generates known data that is a
specified sequence having a specified pattern prearranged between a
transmitter side and a receiver side. The stuff-byte exchanger 620
replaces the stuff bytes in a stuff-byte position of the randomized
data by the known data. The known data can easily be detected from
payload data to be transmitted, and thus is used for
synchronization and equalization in the receiver side. In an aspect
of the invention, the known data is SRS data.
[0062] The RS encoder 630 adds a parity of specified bytes to the
packet into which the known data is inserted by the stuff-byte
exchanger 620 to replace the stuff bytes in order to correct errors
occurring due to channels. The interleaver 640 performs an
interleaving of the data packet to which the parity output from the
first RS encoder 630 is added in a specified pattern.
[0063] The trellis encoder 650 converts the data output from the
interleaver 640 into data symbols, and performs a symbol mapping of
the data symbols through a trellis encoding method at the rate of
2/3. As shown, the trellis encoder 650 initializes a value
temporarily stored in its own memory device to a "00" state at the
start point of the known data, and performs the trellis encoding of
the known data. However, it is understood that other states can be
initialized at the start point. Also, the trellis encoder 650
outputs a value for initializing the memory to the RS parity
generator 660, receives a new parity generated by the RS parity
generator, and replaces the corresponding existing parity by the
received new parity.
[0064] The RS parity generator 660 generates a parity by performing
an RS encoding of the MPEG-2 packet received from the RS encoder
630 using the value for initializing the memory received from the
trellis encoder 650, and transmits the generated parity to the
trellis encoder 650.
[0065] The controller 680 transmits position information of the
stuff bytes and the known data to be replaced in the corresponding
position to the stuff-byte exchanger 620. Also, the controller 680
transmits the position information of an initialization packet that
includes a part used for the initialization among the packet of 187
bytes input to the RS parity generator 660 to the RS encoder 630,
so that only the initialization packet can be used. For convenience
in design, under the assumption that 27 or 26 stuff bytes are used
even if the stuff bytes the number of which is smaller than 27 are
used, 33 or 32 corresponding initialization packets are used as an
input of the RS parity generator 660. However, it is understood
that such an input need not be provided to the generator 660 in all
aspects of the invention, and that other numbers of initializations
can be used as the input.
[0066] Also, the controller 680 outputs signals for indicating the
initialization area and parity area to be replaced to the trellis
encoder 650. The trellis encoder 650 performs a memory
initialization using these signals, receives the parity generated
by the RS parity generation unit 660, and replaces the existing
parity by the received parity.
[0067] The multiplexer 670 inserts a segment sync signal into the
data converted into the symbols by the trellis encoder 650 in the
unit of a segment, and inserts a field sync signal into the data in
the unit of a field as the data format of FIG. 2. A modulator and
RF converter (not illustrated) performs a VSB modulation of a
signal into which a pilot signal has been inserted by performing a
pulse shaping of the signal, carrying the pulse-shaped signal on an
intermediate frequency (IF) carrier, and modulating the amplitude
of the signal, performs an RF conversion and amplification of the
modulated signal, and transmits an amplified RF-converted signal
through a channel allocated with a specified band.
[0068] Hereinafter, the construction and the operation of the
trellis encoder 650 of FIG. 7 will be explained in detail. The
trellis encoder 650 receives the initialization area and the parity
area to be replaced from the controller 680, initializes the
memory, and outputs the value used for the memory initialization to
the RS parity generator 660. Since the trellis encoder 650 has a
feedback structure, its output is affected by the previous memory
value. Accordingly, if the memory values of the trellis encoder 650
are not fixed although the stuff-byte exchanger 620 has replaced
the stuff bytes of the transport stream with specified known data,
the SRS of the known data may be output in various forms according
to the memory value. In order to solve this problem, the memory of
the trellis encoder 650 is initialized by changing an input value
of the trellis encoder 650 as large as the number of stuff bytes at
an SRS start point.
[0069] FIG. 7 is a view illustrating the construction of a trellis
encoder of a digital broadcast transmitter according to an
embodiment of the present invention. If a memory initialization
area for initializing the memory that exists in a start position of
the SRS is input to the trellis encoder 650, initial_sel operates
under the control of the controller 680, and a multiplexer (MUX)
outputs a new value (X1', X0') (i.e., zero forcing input) that
makes the memory state "0" instead of an input (X1, X0) previously
used in the trellis encoder 650. Here, since there are two memories
in a convolutional encoder of the trellis encoder 650, two
successive symbols (i.e., 4 (=2*2)-bit input) are required in order
to initialize the memories.
[0070] Specifically, the input X1, X0 are input to corresponding
multiplexers with the initial_sel. The multiplexer corresponding to
the input X1 further received an output D1, and has an output with
respect to which an exclusive OR function is performed using the
output D1. The result of the exclusive OR function is a mapping
input Z2, which is stored in a memory S2 as a next value of the
output D1. Once recalled from the memory S2, the output D1 is used
as the new value X1'.
[0071] The multiplexer corresponding to the input X0 is multiplexed
with a received output D1, and the output of the multiplexer is a
mapping input Z1 and the new value X0'. An exclusive OR function is
performed on the mapping input Z1 using the output D1, and a result
is stored in a memory S1. The output of the memory S1 is the
mapping input Z0, and is stored in a memory S0 to be recalled as
the output D1.
[0072] Table 1 shows eight states of three memories S0, S1, and S2,
and two successive input values for making the memory state
"0".
TABLE-US-00001 TABLE 1 Present Input Next state/ Input Initial
state t = 0 Present state t = 1 Next state Output select (S0, S1,
S2) (X1, X0) (S0, S1 , S2) (X1, X0) (S0, S1, S2) (z2, z1, z0) 1 0,
0, 0 0, 0 0, 0, 0 0, 0 0, 0, 0 000 1 0, 0, 1 0, 1 0, 0, 0 0, 0 0,
0, 0 000 1 0, 1, 0 0, 0 1, 0, 0 1, 0 0, 0, 0 000 1 0, 1, 1 0, 1 1,
0, 0 1, 0 0, 0, 0 000 1 1, 0, 0 1, 0 0, 0, 0 0, 0 0, 0, 0 000 1 1,
0, 1 1, 1 0, 0, 0 0, 0 0, 0, 0 000 1 1, 1, 0 1, 0 1, 0, 0 1, 0 0,
0, 0 000 1 1, 1, 1 1, 1 1, 0, 0 1, 0 0, 0, 0 000
[0073] The trellis encoder 650 of FIG. 7 outputs X1' and X0' used
for the memory initialization to the RS parity generator 660. Since
new input (X1', X0') is used as an input of the trellis encoder
650, the parity of the MPEG-2 packet that includes the value (X1,
X0) becomes an inaccurate parity. In order to form an accurate
parity, the trellis encoder 650 should construct the parity using
the new input (X1', X0') instead of the existing input (X1, X0).
The generation of the parity is performed through the RS parity
generator 660. The parity newly generated by the RS parity
generator 660 is sent to the trellis encoder 650, and the trellis
encoder 650 replaces the exiting parity by the newly generated
parity.
[0074] FIG. 8 is a block diagram illustrating the construction of
an RS parity generator of a digital broadcast transmitter according
to an embodiment of the present invention. Referring to FIG. 8, the
RS parity generator 660 includes a symbol-to-byte converter 810, a
data deinterleaver 820, a packet buffer 830, an RS encoder 840, a
data interleaver 850, and a byte-to-symbol converter 860. The
symbol-to-byte converter 810 receives an initialization symbol
composed of two bits from the trellis encoder 650, and performs a
symbol-to-byte conversion. According to an aspect of the invention,
the symbol-to-byte conversion is a reverse to the D.2
byte-to-symbol table of the "ATSC Digital Television Standard"
(document A/53), the disclosure of which is incorporated by
reference.
[0075] An example of the byte-to-symbol table is as follows:
TABLE-US-00002 Segment 0 Segment 1 Segment 2 Segment 3 Segment 4
Symbol Trellis Byte Bits Trellis Byte Bits Trellis Byte Bits
Trellis Byte Bits Trellis Byte Bits 0 0 0 7, 6 4 208 5, 4 8 412 3,
2 0 616 1, 0 4 828 7, 6 1 1 1 7, 6 5 209 5, 4 9 413 3, 2 1 617 1, 0
5 829 7, 6 2 2 2 7, 6 6 210 5, 4 10 414 3, 2 2 618 1, 0 6 830 7, 6
3 3 3 7, 6 7 211 5, 4 11 415 3, 2 3 619 1, 0 . . . . . . . . . 4 4
4 7, 6 8 212 5, 4 0 416 3, 2 4 620 1, 0 . . . . . . . . . 5 5 5 7,
6 9 213 5, 4 1 417 3, 2 5 621 1, 0 . . . . . . . . . 6 6 6 7, 6 10
214 5, 4 2 418 3, 2 6 622 1, 0 . . . . . . . . . 7 7 7 7, 6 11 215
5, 4 3 419 3, 2 7 623 1, 0 . . . . . . . . . 8 8 8 7, 6 0 204 5, 4
4 408 3, 2 8 612 1, 0 . . . . . . . . . 9 9 9 7, 6 1 205 5, 4 5 409
3, 2 9 613 1, 0 . . . . . . . . . 10 10 10 7, 6 2 206 5, 4 6 410 3,
2 10 614 1, 0 . . . . . . . . . 11 11 11 7, 6 3 207 5, 4 7 411 3, 2
11 615 1, 0 . . . . . . . . . 12 0 0 5, 4 4 208 3, 2 8 412 1, 0 0
624 7, 6 . . . . . . . . . 13 1 1 5, 4 5 209 3, 2 9 413 1, 0 1 625
7, 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . 19 7 7 5, 4 11
215 3, 2 3 419 1, 0 7 631 7, 6 . . . . . . . . . 20 8 8 5, 4 0 204
3, 2 4 408 1, 0 8 632 7, 6 . . . . . . . . . 21 9 9 5, 4 1 205 3, 2
5 409 1, 0 9 633 7, 6 . . . . . . . . . 22 10 10 5, 4 2 206 3, 2 6
410 1, 0 10 634 7, 6 . . . . . . . . . 23 11 11 5, 4 3 207 3, 2 7
411 1, 0 11 635 7, 6 . . . . . . . . . 24 0 0 3, 2 4 208 1, 0 8 420
7, 6 0 624 5, 4 . . . . . . . . . 25 1 1 3, 2 5 209 1, 0 9 421 7, 6
1 625 5, 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 7 7 3,
2 11 215 1, 0 3 427 7, 6 . . . . . . . . . . . . . . . . . . 32 8 8
3, 2 0 204 1, 0 4 428 7, 6 . . . . . . . . . . . . . . . . . . 33 9
9 3, 2 1 205 1, 0 5 429 7, 6 . . . . . . . . . . . . . . . . . . 34
10 10 3, 2 2 206 1, 0 6 430 7, 6 . . . . . . . . . . . . . . . . .
. 35 11 11 3, 2 3 207 1, 0 7 431 7, 6 . . . . . . . . . . . . . . .
. . . 36 0 0 1, 0 4 216 7, 6 8 420 5, 4 . . . . . . . . . . . . . .
. . . . 37 1 1 1, 0 5 217 7, 6 9 421 5, 4 . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . 47 11 11 1, 0 3 227 7, 6 . .
. . . . . . . . . . . . . . . . . . . . . . . . . 48 0 12 7, 6 4
216 5, 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 1
13 7, 6 5 217 5, 4 . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . 95 11 23 1, 0 . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . 96 0 24 7, 6 .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. 97 1 25 7, 6 . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . 767 11 191 1, 0 . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
768 0 192 7, 6 . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . 769 1 193 7, 6 . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
815 11 203 1, 0 3 419 7, 6 7 623 5, 4 11 827 3, 2 . . . . . . . . .
816 0 204 7, 6 4 408 5, 4 8 612 3, 2 0 816 1, 0 . . . . . . . . .
817 1 205 7, 6 5 409 5, 4 9 613 3, 2 1 817 1, 0 . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . 827 11 215 7, 6 3 419 5, 4 7 623 3, 2 11
827 1, 0 . . . . . . . . .
[0076] The data deinterleaver 820 deinterleaves the symbol-to-byte
converted value, and then outputs the deinterleaved value to the
packet buffer 830. The packet buffer 830 temporarily stores a
packet that includes the output of the data deinterleaver 820 and
the initialization area in the unit of 187 bytes output from the RS
encoder 630. The packet buffer 830 replaces the value in the
existing initialization area by a new value. In this case, all bits
constituting one byte are not used as the replaced input, but only
four upper bits of the byte used for the initialization are
replaced. The RS encoder 840 performs an RS encoding of the output
of the packet buffer 830, and adds the parity to the encoded
output. Here, the parity generated by the RS encoder 630 passes
through the data deinterleaver 820. The output of the data
deinterleaver 820 is byte-to-symbol-converted according to D.2
table of the "ATSC Digital Television Standard" (document A/53),
and is used as an input of the trellis encoder 650.
[0077] FIG. 9 is a block diagram illustrating an example of a
parity generator 660 of a digital broadcast transmitter, which
operates at high speed and solves a delay problem occurring during
the operation of the interleaver 850 and the deinterleaver 820,
according to an embodiment of the present invention. The parity
generator 660 of FIG. 9 includes include a byte mapper 910, a
packet buffer 920, an RS encoder 930, and a symbol buffer 940.
[0078] The byte mapper 910 performs mapping of the initialization
symbols input from the trellis encoder 650 onto the
byte-to-symbol-converted and interleaved value, and outputs the
mapped symbols to the packet buffer 920. The packet buffer 920
temporarily stores a packet that includes the output of the byte
mapper and the initialization area in the unit of 187 bytes output
from the RS encoder 650. After the data replacement is performed in
the packet buffer 920, the output of the packet buffer is
RS-encoded by the RS encoder 930, and then is input to the trellis
encoder 650 at high speed, through the symbol mapper 940. The
symbol mapper 940 simultaneously operates the interleaver and the
byte-to-symbol converter of FIG. 8.
[0079] FIGS. 10 to 14 are views illustrating data formats for
explaining an example of the operation of the present invention.
First, FIG. 10 is a view explaining the change of an SRS area of a
transport stream according to an interleaving operation of the
interleaver 640 according to an aspect of the present
invention.
[0080] The stuff bytes for the SRS that exist in 207 packets output
from the RS encoder 630 according to the interleaving appear
repeatedly in the unit of 52 segments. The stuff bytes are arranged
in a horizontal direction according to the interleaving. Here, the
first horizontal line corresponds to the first stuff byte, the
second horizontal line the second stuff byte, and the N-th
horizontal line the N-th stuff byte, respectively. As illustrated
in FIG. 2, the VSB frame has 312 data segments arranged after a
field sync segment. That is, since 312/52=6, six identical SRSs in
the unit of 52 segments are arranged after the field sync
segment.
[0081] FIG. 11 is a view illustrating an SRS area, an
initialization area, and an initialization packet RS parity, as
seen from the output of the RS encoder in the case where the length
of the stuff bytes is 27. The initialization packet RS parity is a
parity corresponding to the initialization area, and indicates the
parity to be replaced by a new parity according to the
initialization of the trellis encoder. As illustrated in FIG. 10, a
lower part of 52 bytes first appears after the interleaving, and
this part becomes the initialization area.
[0082] One to 27 stuff bytes can be used for the SRS according to
an aspect of the invention. When N stuff bytes are used for the
SRS, up to N parities corresponding to the initialization area
become the initialization packet RS parities as shown in FIG. 11.
For example, if one stuff byte is used, as shown in FIG. 11, the
initialization area of the first stuff byte has a size of 7 bytes,
and seven packets 52, 1, 2, 3, 4, 5, and 6 that include the
initialization area are used for the initialization. The
initialization area of the second stuff byte has a size of 8 bytes,
and packets 52, 1, 2, 3, 4, 5, 6, and 7 are used for the
initialization.
[0083] As illustrated, if N stuff bytes (i.e., the first stuff byte
to the N-th stuff byte) are used to form the SRS, packets 52, 1, 2,
3, . . . , N+4, and N+5 correspond to packets that include the
initialization area. That is, the parities of N+6 packets include
the initialization area, the parities become the initialization
packet RS parities, that will be replaced later. If N=27, parities
of the packets 52, 1, 2, 3, . . . , 31, and 32, i.e., 33 parities,
become the initialization packet RS parities.
[0084] On the other hand, since a TCM encoder used in the ATSC
performs a trellis encoding in the unit of 12 symbols, 12 TCM
encoders should be initialized for a complete initialization, but
are not required in all aspects of the invention. However, due to
causality, the first to fifth stuff bytes can initialize 7, 8, 9,
10, and 110 TCM encoders, respectively. Other stuff bytes used for
the SRS can all be used for the initialization. This number is
equal to the size of the initialization area of the respective
stuff byte as illustrated in FIG. 11. In FIG. 11, since four
symbols of the respective byte (two bits are used to construct one
symbol) pass through the same TCM encoder, one byte can initialize
one TCM encoder. As described above, since the initialization
becomes possible with only two symbols, i.e., 4 (=2*2) bits, only
four MSB bits of the initialization position are used for the
initialization, and four LSB bits are used to construct the
SRS.
[0085] FIG. 12 is a view illustrating the data format of an output
of the RS encoder 630 after the data passes through the data
interleaver 640. After the initialization area of 27 stuff bytes,
parities corresponding to only 33 packets, i.e., packets 52, 1, 2,
. . . , 31, and 32, appear. On the other hand, as described above,
the output of the trellis encoder 650 and the next memory state are
affected by the previous memory value. That is, if the previous
input is changed, an input to be used for the initialization is
changed. If the parity of the packet corresponding to the
initialization area precedes the initialization area, the input
value previously used to initialize the memory of the trellis
encoder 650 is changed due to the newly generated parity. In this
case, the initialization may not be performed, or an accurate
parity cannot be generated using the initialization value.
Accordingly, in order to prevent the parity of the initialization
packet from preceding the initialization area as shown in FIG. 12,
the maximum number of used stuff bytes becomes 27. However, it is
understood that, for other types of packets divided into other
numbers of segments, other maximum numbers of used stuff bytes can
be imposed.
[0086] For the reason as described above, the trellis encoder 650
can initialize up to seven first stuff bytes. The initialization
positions of the five remaining stuff bytes exist in the packets
47, 48, 49, 50, and 51, and since the parities of all the packets
to be replaced precede the initialization positions, parities
cannot be used for the initialization.
[0087] FIG. 13 is a view illustrating the structure of a TS packet
that is repeated in the unit of 52 segments. In FIG. 13, the output
form of the RS encoder 630 in the case where 27 stuff bytes are
used for the SRS is illustrated. If less than 27 stuff bytes are
used, the initialization packet RS parities are reduced as much as
a part corresponding to the reduced area. Since the non-initialized
part is not used for the SRS, it can be used for other purposes. In
the drawing, if the PCR is transferred through the 15.sup.th
packet, it invades one byte of the SRS since it occupies a 6-byte
space. In this case, the corresponding space is not used for the
SRS, and 6 bytes including the front 5 bytes are used to transmit
the PCR.
[0088] FIG. 14 is a view illustrating input values of a stuff-byte
exchanger for generating the SRS according to an aspect of the
present invention. The SRS pattern byte values are determined such
that after the specific known data pass through the TCM encoders,
the output specific known data has a spectrum similar to that of
pseudo noise and has an average DC (direct current) value close to
0. If less than 27 stuff bytes are used, the replacement is
performed as many as the number of the stuff bytes. For example, if
10 stuff bytes are used, the SRS is generated in replacement of 10
corresponding parts. The lower four bits of the initialization area
are used for the SRS, while certain values may enter into the upper
four bits. Also, any value may enter into a non-initialized part.
However, if the PCR is used, any other value cannot enter into the
PCR position so that the PCR is transferred as it is.
[0089] FIG. 15 is a block diagram illustrating the construction of
a digital broadcast receiver according to an embodiment of the
present invention. The digital broadcast receiver of FIG. 15
includes a demodulator 1510, an equalizer 1520, a Viterbi decoder
1530, a deinterleaver 1540, an RS decoder 1550, a derandomizer
1560, and a controller 1570. A tuner (not illustrated) converts an
RF signal received through a channel into a baseband signal, and
the demodulator 1510 performs a sync detection and demodulation of
the converted baseband signal. While described in terms of a
Viterbi decoder, it is understood that other decoders and/or symbol
identifiers can be used.
[0090] The equalizer 1520 compensates for a channel distortion of
the demodulated signal due to the multi-path of the channel. Also,
the equalizer 1520 receives the known data (such as SRS) from the
controller 1570, and uses it for the channel distortion
compensation. The Viterbi decoder 1530 error-corrects and decodes
the equalized signal from the equalizer 1520. The deinterleaver
1540 rearranges the data dispersed by the interleaver of the
transmitter.
[0091] The deinterleaved data is error-corrected through the RS
decoder 1550, and the error-corrected data is derandomized through
the derandomizer 1560, so that the data of the MPEG-2 transport
stream is restored. On the other hand, the controller 1570
transmits the SRS period and values of the SRS to the equalizer
1520 to use them for the performance improvement. The SRS period
and the values of the SRS are determined according to the mode, and
this mode may be predetermined or the mode signal may be
transmitted from the transmitter. In the case where the transmitter
sends the mode signal, the controller 1570 detects the mode signal,
and sends the SRS period and values of the SRS corresponding to the
mode to the equalizer 1520. In order to construct the SRS having
fixed values, its inputs should be determined as specified values
as shown in FIG. 14. In order to improve the performance, the
Viterbi decoder 1530 and/or the RS decoder 1550 receive accurate
values of the SRS from the controller 1570 instead of the decoding
output.
[0092] FIG. 16 is a block diagram illustrating the construction of
a digital broadcast transmitter according to another embodiment of
the present invention. The transmitter of FIG. 16 is a system that
uses the linear code characteristic of an RS encoder. An RS parity
generator 1660 uses only initialization symbols as its input. With
respect to 187 bytes except for the initialization symbols, the RS
parity generator 1660 considers them as inputs of "0", and outputs
a parity. Specifically and referring to FIG. 16, the digital
broadcast transmitter further includes a randomizer 1610, a
stuff-byte exchanger 1620, an RS encoder 1630, an interleaver 1640,
a trellis encoder 1650, a multiplexer 1670, and a controller 1680.
The randomizer 1610 randomizes an input MPEG-2 transport steam data
in order to heighten the utility of an allocated channel space. The
data input to the randomizer 1610 has the data format formed by
inserting stuff bytes, which have a specified length of bytes, but
does not include payload data as shown in FIGS. 5a to 5e, into a
specified position of the input transport stream data.
[0093] The stuff-byte exchanger 1620 generates known data that is a
specified sequence having a specified pattern prearranged between a
transmitter side and a receiver side. The stuff-byte exchanger 1620
replaces the stuff bytes in a stuff-byte position of the randomized
data by the known data. The known data can easily be detected from
payload data to be transmitted, and thus is used for
synchronization and equalization in the receiver side. The RS
encoder 1630 adds a parity of specified bytes to the packet into
which the known data is inserted by the stuff-byte exchanger 1620
in replacement of the stuff bytes in order to correct errors
occurring due to channels.
[0094] The interleaver 1640 performs an interleaving of the data
packet to which the parity output from the first RS encoder 1630 is
added in a specified pattern. The trellis encoder 1650 converts the
data output from the interleaver 1640 into data symbols, and
performs a symbol mapping of the data symbols through a trellis
encoding at the rate of 2/3. Here, the trellis encoder 1650
initializes the value temporarily stored in its own memory device
to a "00" state at the start point of the known data, and performs
the trellis encoding of the known data. Also, the trellis encoder
1650 outputs a value for initializing the memory to the RS parity
generator 1660, receives a new parity generated by the RS parity
generator 1660, and replaces the corresponding existing parity by
the received new parity.
[0095] The RS parity generator 1660 generates a parity by
performing an RS encoding of the MPEG-2 packet received from the RS
encoder 1630 using the value for initializing the memory received
from the trellis encoder 1650, and transmits the generated parity
to the trellis encoder 1650. The RS parity generator 1660 uses only
initialization symbols as its input. With respect to 187 bytes
except for the initialization symbols, the RS parity generator 1650
considers them as inputs of "0", and outputs the parity.
[0096] The controller 1680 transmits position information of the
stuff bytes and the known data to be replaced in the corresponding
position to the stuff-byte exchanger 1620. Also, the controller
1680 transmits the position information of an initialization packet
that includes a part used for the initialization among the packet
of 187 bytes input to the RS parity generator 1660 to the RS
generator 1660, so that only the initialization packet can be used.
For convenience in design, under the assumption that 27 or 26 stuff
bytes are used even if the stuff bytes the number of which is
smaller than 27 are used, 33 or 32 corresponding initialization
packets can be used as an input of the RS parity generator
1660.
[0097] Also, the controller 1680 outputs signals for indicating the
initialization area and parity area to be replaced to the trellis
encoder 1650. The trellis encoder 1650 performs a memory
initialization using these signals, receives the parity generated
by the RS parity generation unit 1660, and replaces the existing
parity by the received parity. The multiplexer 670 inserts a
segment sync signal into the data converted into the symbols by the
trellis encoder 1650 in the unit of a segment, and inserts a field
sync signal into the data in the unit of a field as the data format
of FIG. 2. A modulator and RF converter (not illustrated) performs
a VSB modulation of a signal into which a pilot signal has been
inserted by performing a pulse shaping of the signal, carrying the
pulse-shaped signal on an intermediate frequency (IF) carrier, and
modulating the amplitude of the signal, performs an RF conversion
and amplification of the modulated signal, and transmits an
amplified RF-converted signal through a channel allocated with a
specified band.
[0098] FIG. 17 is a view illustrating the construction of a trellis
encoder 1650 used to perform the above-described operation. The
trellis encoder 1650 performs an exclusive OR of a new input bit
required to initialize the memory and an input bit X0, X1 used as
the original input in the initialization area, and sends the result
X1', X0' of the exclusive OR to an RS parity generator 1660. The RS
parity generator 1660 generates a parity using this value only, and
performs an exclusive OR of the generated parity and the parity
input as the original input to be replaced by the generated parity
to use the resultant value of the exclusive OR. Accordingly, the
same parity as the parity used to replace the parity changed
according to the initialization is input, and the same operation is
performed.
[0099] As shown, new RS parity from the RS re-encoder p0, p1 and
the input bits X0, X1 are input to the corresponding multiplexers
1200. An exclusive OR operation is performed on the corresponding
new RS parity p0, p1 prior to being received at the corresponding
multiplexers 1200. According to the initial select and the parity
selection, the multiplexers 1200 output D0s to corresponding
multiplexers 1250.
[0100] For the output of the multiplexer 1250 corresponding to the
parity p1 and input bit X1, an exclusive OR operation is performed
with respect to an output D1 of memory S2. The output D1 is further
input to the multiplexer 1250. The result of the exclusive OR
operation is a mapping output Z2 for use with a corresponding TCM.
The mapping value Z2 is also stored in the memory S2 as the next
value for output D1. An exclusive OR operation is performed with
respect to the output D1 and the parity p1, and the result is
output as new input X1' used for the memory initialization to the
RS parity generator 660.
[0101] The output of the multiplexer 1250 corresponding to the
parity p0 and input bit X0 is a mapping value Z1 for use with a
corresponding TCM. An exclusive OR operation is performed with
respect to input bit X0 and the mapping value Z1, and the output is
the new input X0' used for the memory initialization to the RS
parity generator 660. An exclusive OR operation is further
performed on the mapping value Z1 with respect to an output D1 from
a memory S0, and the result of the exclusive OR operation is stored
in memory S1 to be output as mapping output Z0 for use with a
corresponding TCM. The mapping output Z0 is stored in the memory S0
as the next value for output D1. The output D1 is further input to
the multiplexer 1250 with the output D0.
[0102] FIG. 18 is a flowchart provided to explain the operation of
a digital broadcast transmitter according to an embodiment of the
present invention. The randomizer 610 receives and randomizes an
input transport steam (S100). The stuff-byte exchanger 620 inserts
the known data into a stuff region included in the transport stream
randomized by the randomizer 610, under the control of the
controller 680 (S110).
[0103] When the transport stream into which the known data has been
inserted is input, the encoder 630 performs an RS encoding for
adding a parity to the parity area included in the transport stream
packet (S120). The interleaver 640 performs an interleaving of the
data packet, to which the parity output from the RS encoder 620 is
added, in a specified pattern (S130). The trellis encoder 650
initializes the value temporarily stored in its own memory device
at a start point of the known data, and performs a trellis encoding
of the known data (S140).
[0104] The RS parity generator 660 generates a parity by performing
an RS encoding of the MPEG-2 packet received from the RS encoder
630 using the value for initializing the memory received from the
trellis encoder 650, and transmits the generated parity to the
trellis encoder (S150). The multiplexer 670 inserts a segment sync
signal into the data converted into the symbols by the trellis
encoder 650 in the unit of a segment and inserts a field sync
signal into the data in the unit of a field as the data format of
FIG. 2 (S160).
[0105] The modulator and RF converter (not illustrated) performs a
VSB modulation of a signal into which a pilot signal has been
inserted by performing a pulse shaping of the signal, carrying the
pulse-shaped signal on an intermediate frequency (IF) carrier, and
modulating the amplitude of the signal, performs an RF conversion
and amplification of the modulated signal, and transmits the
amplified RF-converted signal through a channel allocated with a
specified band (S170).
[0106] FIG. 19 is a flowchart provided to explain the operation of
a digital broadcast receiver according to an embodiment of the
present invention. The tuner (not illustrated) converts an RF
signal received through a channel into a baseband signal, and the
demodulator 1510 performs a sync detection and demodulation of the
converted baseband signal (S200). The equalizer 1520 performs the
equalization by compensating for the channel distortion of the
demodulated signal and removing the interference between the
received symbols (S210).
[0107] The Viterbi decoder 1530 error-corrects and decodes the
equalized signal (S220). The deinterleaver 1540 rearranges the data
dispersed by the interleaver of the transmitter (S230). The
deinterleaved data is error-corrected through the RS decoder 1550
(S240), and the error-corrected data is derandomized through the
derandomizer 1560, so that the data of the MPEG-2 transport stream
is restored (S250).
[0108] As described above, according to an aspect of the present
invention, the receiving performance of the digital broadcast
receiver such as the synchronization and the equalization can be
improved even in an inferior multi-path channel by generating and
inserting the stuff bytes into the MPEG-2 transport stream, and
transmitting the transport stream into which the known data is
inserted in replacement of the stuff bytes in the digital broadcast
transmitter, and by detecting the known data from the received
signal and using the known data for the synchronization and the
equalization in the digital broadcast receiver.
[0109] According to an aspect of the present invention, the
operation performance of the equalizer can be improved through the
proper adjustment of the amount and the pattern of the sequence of
the known data inserted into the transport stream, and thus the
receiving performance of the digital broadcast receiver can be
improved.
[0110] Although a few embodiments of the present invention have
been shown and described, it would be appreciated by those skilled
in the art that changes may be made in this embodiment without
departing from the principles and spirit of the invention, the
scope of which is defined in the claims and their equivalents.
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