Television – Image signal processing circuitry specific to television – Noise or undesired signal reduction
Reexamination Certificate
2001-08-20
2004-07-06
Hsia, Sherrie (Department: 2614)
Television
Image signal processing circuitry specific to television
Noise or undesired signal reduction
C348S021000, C348S554000, C348S726000
Reexamination Certificate
active
06760077
ABSTRACT:
CROSS REFERENCE TO RELATED ART
This application claims the benefit of Korean Patent Application No. 2001-3304, filed on Jan. 19, 2001, which is hereby incorporated by reference in their entirety.
This application incorporates by reference in their entirety co-pending U.S. application Ser. No. 09/933,353, mailed via Express Mail No. EF334462230US entitled “VSB COMMUNICATION SYSTEM” and Ser. No. 09/933,280, mailed via Express Mail No. EF334462226US entitled “VSB TRANSMISSION SYSTEM FOR PROCESSING SUPPLEMENTAL TRANSMISSION DATA.”
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a digital television reception system, and more particularly, to a 8T-VSB (Vestigial Sideband) reception system resistant to ghost and noise and receiving and decoding supplemental data in addition to MPEG data.
2. Description of the Related Art
The United States of America has employed ATSC 8T-VSB (8 Trellis-Vestigial Sideband) as a standard since 1995, and has been broadcasting in the ATSC 8T-VSB since the later half of 1998. South Korea also has employed the ATSC 8T-VSB as a standard. South Korea started test broadcasting in May 1995, and has since August 2000 put in place a regular test broadcasting system. The advancement of technology allows the transmission of digital television (DTV) in the same 6 MHz bandwidth currently used by NTSC.
FIG. 1
illustrates a block diagram of a conventional ATSC 8T-VSB transmission system
25
(“VSB transmission system”). The VSB transmission system
25
generally comprises a data randomizer
1
, Reed-Solomon coder
2
, data interleaver
3
, Trellis coder
4
, multiplexer
5
, pilot inserter
6
, VSB modulator
7
and RF converter
8
.
Referring to
FIG. 1
, there is a data randomizer
1
for receiving and making random MPEG data (video, audio and ancillary data). The data randomizer
1
receives the MPEG-II data output from an MPEG-II encoder. Although not shown in
FIG. 1
, the MPEG-II encoder takes baseband digital video and performs bit rate compression using the techniques of discrete cosine transform, run length coding, and bi-directional motion prediction. The MPEG-II encoder then multiplexes this compressed data together with pre-coded audio and any ancillary data that will be transmitted. The result is a stream of compressed MPEG-II data packets with a data frequency of only 19.39 Mbit/Sec. The MPEG-II encoder outputs such data to the data randomizer in serial form. MPEG-II packets are 188 bytes in length with the first byte in each packet always being the sync or header byte. The MPEG-II sync byte is then discarded. The sync byte will ultimately be replaced by the ATSC segment sync in a later stage of processing.
In the VSB transmission system
25
, the 8-VSB bit stream should have a random, noise-like signal. The reason being that the transmitted signal frequency response must have a flat noise-like spectrum in order to use the allotted 6 MHz channel space with maximum efficiency. Random data minimizes interference into analog NTSC. In the data randomizer
1
, each byte value is changed according to known pattern of pseudo-random number generation. This process is reversed in the VSB receiver in order to recover the proper data values.
The Reed-Solomon coder
2
of the VSB transmission system
25
is used for subjecting the output data of the data randomizer
1
to Reed-Solomon coding and adding a 20 byte parity code to the output data. Reed Solomon encoding is a type of forward error correction scheme applied to the incoming data stream. Forward error correction is used to correct bit errors that occur during transmission due to signal fades, noise, etc. Various types of techniques may be used as the forward error correction process.
The Reed-Solomon coder
2
takes all 187 bytes of an incoming MPEG-II data packet (the sync or header byte has been removed from 188 bytes) and mathematically manipulates them as a block to create a digital sketch of the block contents. This “sketch” occupies 20 additional bytes which are added at the tail end of the original 187 byte packet. These 20 bytes are known as Reed-Solomon parity bytes. The 20 Reed-Solomon parity bytes for every data packet add redundancy for forward error correction of up to 10 byte errors/packet. Since Reed-Solomon decoders correct byte errors, and bytes can have anywhere from 1 to 8 bit errors within them, a significant amount of error correction can be accomplished in the VSB reception system. The output of the Reed-Solomon coder
2
is 207 bytes (187 plus 20 parity bytes).
The VSB reception system will compare the received 187 byte block to the 20 parity bytes in order to determine the validity of the recovered data. If errors are detected, the receiver can use the parity bytes to locate the exact location of the errors, modify the corrupted bytes, and reconstruct the original information.
The data interleaver
3
interleaves the output data of the Reed-Solomon coder
2
. In particular, the data interleaver
3
mixes the sequential order of the data packet and disperses or delays the MPEG-II packet throughout time. The data interleaver
3
then reassembles new data packets incorporating small sections from many different MPEG-II (pre-interleaved) packets. The reassembled packets are 207 bytes each.
The purpose of the data interleaver
3
is to prevent losing of one or more packets due to noise or other harmful transmission environment. By interleaving data into many different packets, even if one packet is completely lost, the original packet may be substantially recovered from information contained in other packets.
The VSB transmission system
25
also has a trellis coder
4
for converting the output data of the data interleaver
3
from byte form into symbol form and for subjecting it to trellis coding. In the trellis coder
4
, bytes from the data interleaver
3
are converted into symbols and provided one by one to a plurality of Trellis coders and precoders
32
-
1
to
32
-
12
, shown in FIG.
7
.
Trellis coding is another form of forward error correction. Unlike Reed-Solomon coding, which treated the entire MPEG-II packet simultaneously as a block, trellis coding is an evolving code that tracks the progressing stream of bits as it develops through time.
The trellis coder
4
adds additional redundancy to the signal in the form of more (than four data levels, creating the multilevel (8) data symbols for transmission. For trellis coding, each 8-bit byte is split up into a stream of four, 2-bit words. In the trellis coder
4
, each 2-bit input word is compared to the past history of previous 2-bit words. A 3-bit binary code is mathematically generated to describe the transition from the previous 2-bit word to the current one. These 3-bit codes are substituted for the original 2-bit words and transmitted as the eight level symbols of 8-VSB. For every two bits that enter the trellis coder
4
, three bits come out.
The trellis decoder in the VSB receiver uses the received 3-bit transition codes to reconstruct the evolution of the data stream from one 2-bit word to the next. In this way, the trellis coder follows a “trail” as the signal moves from one word to the next through time. The power of trellis coding lies in its ability to track a signal's history through time and discard potentially faulty information (errors) based on a signal's past and future behavior.
A multiplexer
5
is used for multiplexing a symbol stream from the trellis coder
4
and synchronizing signals. The segment and the field synchronizing signals provide information to the VSB receiver to accurately locate and demodulate the transmitted RF signal. The segment and the field synchronizing signals are inserted after the randomization and error coding stages so as not to destroy the fixed time and amplitude relationships that these signals must possess to be effective. The multiplexer
5
provides the output from the trellis coder
4
and the segment and the field synchronizing signals in a time division manner.
An output packet of the data interleaver
3
comprises the 20
Choi In Hwan
Gu Young Mo
Kang Kyung Won
Kwak Kook Yeon
Hsia Sherrie
Lee Hong Degerman Kang & Schmadeka
LG Electronics Inc.
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