Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
1999-12-22
2003-09-23
Tran, Pablo N (Department: 2685)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S013200, C455S503000, C370S324000, C370S310000, C370S503000, C375S354000
Reexamination Certificate
active
06625463
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to serial data communications generally and, more particularly, to a methodology for the synchronization of super frames in an integrated services digital broadcasting for satellites (ISDB-S) system.
BACKGROUND OF THE INVENTION
Data may be serially transmitted one bit at a time along a data transmission path. The serial data can be transmitted in groups of bits called frames. The frames are delimited by synchronization codes that identify the beginning or the end of each frame. The synchronization codes must be identified in the data stream before the significance of the data contained in the frame can be determined. When a synchronization code is identified, a signal can be generated to synchronize a data recovery circuit to the contents of the frame. The synchronization of the data recovery circuit to the frame is frame synchronization. The frames can be grouped into super frames. The synchronization of a super frame is super frame synchronization.
Referring to
FIG. 1
, a diagram of a satellite transmission system
10
illustrating a satellite data transmission path is shown. A data signal
12
is sent using electromagnetic waves from an uplink station
14
to a satellite
16
. The data signal
12
can contain one or more integrated services digital broadcasting for satellites (ISDB-S) system super frames. The satellite
16
can recover the data from the data signal
12
and/or relay the data signal
12
using electromagnetic waves to a downlink ground station
18
. The ground station
18
can recover the data from the data signal
12
. Both the satellite
16
and the ground station
18
can use a data recovery circuit that is synchronized to the data signal
12
by a synchronization detector circuit. Since the data signal
12
is sent using electromagnetic waves, the data signal
12
can contain noise. A measurement of a power ratio between signal and noise acquired by the data signal
12
is the signal-to-noise ratio (SNR). As the SNR of the signal
12
decreases, synchronization and data recovery become more difficult.
Referring to
FIG. 2
, a diagram of an ISDB-S super frame
20
is shown. In an integrated services digital broadcasting for satellites (ISDB-S) system, frame structure is organized into super frames
20
. Each super frame contains eight frames
22
a
-
22
g
. Each frame has an embedded unique word W
1
(e.g., ECD28h) in its header to identify the start of the frame
22
. In addition, the first frame
22
a
of a super frame
20
has a unique word W
2
(e.g., OB677h) in its header to identify the start of the super frame
20
. Each of the subsequent seven frames
22
b
-
22
g
have a unique word W
3
(e.g., F4988h) in the same position as the unique word W
2
in the first frame
22
a
. The unique words W
2
and W
3
are digital complements of each other (e.g., W
2
=!W
3
).
In a conventional method of super frame synchronization, a state machine is constructed based on the detection of only the unique word W
2
. The embedded unique words W
3
are not used in super frame synchronization. Using only the unique word W
2
to acquire super frame synchronization has the disadvantage of a high false lock probability, especially in a low signal-to-noise ratio (SNR) environment. Since the super frame is quite large, a high probability of false lock makes super frame synchronization based on a single unique word unreliable. A solution is needed to provide a reliable super frame synchronization.
SUMMARY OF THE INVENTION
The present invention concerns an apparatus comprising a first circuit and a second circuit. The first circuit may be configured to generate a first detection signal and a second detection signal in response to (i) an input signal, (ii) a first control signal, and (iii) a second control signal. The second circuit may be configured to generate a first output signal and a second output signal in response to (i) the first detection signal, (ii) the second detection signal, and (iii) a third control signal.
The objects, features and advantages of the present invention include providing a method of synchronizing super frames in an integrated services digital broadcasting for satellites (ISDB-S) system that may (i) reduce the probability of false locks, (ii) detect two unique words, (iii) use one detection region for detecting two unique words, (iv) use one unique word detector to detect two unique words, (v) adjust parameters in response to a signal-to-noise ration, and/or (vi) provide a more reliable frame synchronization.
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patent: 4847877 (1989-07-01), Besseyre
patent: 5646947 (1997-07-01), Cooper et al.
patent: 5740168 (1998-04-01), Nakamura et al.
patent: 5982761 (1999-11-01), Dutta
patent: 5991279 (1999-11-01), Haugli et al.
patent: 6195402 (2001-02-01), Hiramatsu
patent: 6204725 (2001-03-01), Ohishi
patent: 6341125 (2002-01-01), Hong et al.
Lu Bo
Xiao Chusong
LSI Logic Corporation
Maiorana PC Christopher P.
Tran Pablo N
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