Technical Field
[0001] The present disclosure relates to transmitting and receiving a-priori information in a
communication system.
[0002]
This application claims the benefit of U.S. Patent Application No. 14/566574 filed on
December 10, 2014, the entire contents of which are incorporated herein by reference.
Background Art
[0003] During the last decade, terrestrial broadcasting has evolved from analog to digital.
There exist several wideband digital communication techniques depending on a
broadcasting standard used. For example, direct sequence spread spectrum (DSSS) and
orthogonal frequency-division multiplexing (OFDM) are one of the latest schemes
used in wideband digital communication systems, whether wireless or over copper
wires. OFDM is a method of encoding digital data on multiple carrier frequencies and
is used in applications such as digital television and audio broadcasting, DSL Internet
access, wireless networks, power line networks, and 4G mobile communications.
[0004] Current digital broadcasting systems use fixed knowledge of a channel bandwidth at
a receiver. In addition to the specific information about the communications
technology used, the receiver needs the channel bandwidth or a sampling frequency to
demodulate received signals. Due to technical advancements, the channel bandwidth
and the sampling frequency may change over the years. As recognized by the present
inventor, there is a need to facilitate changes in channel bandwidth and/or sampling
frequency.
Summary of Invention
[0005] According to an embodiment of the present disclosure, there is provided a method of
a transmission apparatus for transmitting a-priori information. The method includes
generating, by circuitry of a transmission apparatus, the a-priori information based on a
sampling frequency and a channel bandwidth of a signal to be transmitted. The a-priori
information is appended to a data signal by the circuitry. The circuitry transmits the
data signal including the appended a-priori information to a reception apparatus.
[0006] According to an embodiment of the present disclosure, there is provided a
transmission apparatus that includes circuitry configured to generate a-priori in
formation based on a sampling frequency and a channel bandwidth of a data signal to
be transmitted, append the a-priori information to the data signal, and transmit the data
signal including the appended a-priori information to a reception apparatus.
[0007] According to an embodiment of the present disclosure, there is provided a method of
a reception apparatus for detecting a-priori information. The method includes
receiving, by circuitry of a reception apparatus, a transmitted signal. The transmitted
signal includes a-priori information appended to a data signal. The a-priori information
included in the transmitted signal is detected by the circuitry. Further, the circuitry de
termines a sampling frequency and a channel bandwidth associated with the
transmitted signal based on the detected a-priori information.
[0008] According to an embodiment of the present disclosure, there is provided a reception
apparatus. The reception apparatus includes circuitry configured to receive a
transmitted signal. The transmitted signal includes a-priori information appended to a
data signal. The circuitry detects the a-priori information included in the transmitted
signal and determines a sampling frequency and a channel bandwidth associated with
the transmitted signal based on the detected a-priori information.
Brief Description of Drawings
[0009] A more complete appreciation of the present disclosure and many of the attendant ad
vantages thereof will be readily obtained as the same becomes better understood by
reference to the following detailed description when considered in connection with the
accompanying drawings, wherein:
[0010] [fig. 1]Fig. 1 illustrates portions of a reception apparatus according to one embodiment.
[fig.2]Fig. 2 illustrates a flow diagram of an exemplary method for transmission of apriori
information.
[fig.3]Fig. 3 illustrates a flow diagram of an exemplary method for reception of a-prior
information.
[fig.4]Fig. 4 illustrates a preamble proposed by SONY corporation that includes apriori
information according to one embodiment.
[fig.5A]Fig. 5A illustrates a chirp signal according to one embodiment.
[fig.5B]Fig. 5B illustrates a two-tone signal according to one embodiment.
[fig.6]Fig. 6 illustrates a time domain and magnitude spectrum of a chirp signal
according to one embodiment.
[fig.7]Fig. 7 is a block diagram of an exemplary transmission apparatus.
[fig.8]Fig. 8 illustrates a proposed ATSC 3.0 physical layer architecture according to
one embodiment.
[fig.9]Fig. 9 is a block diagram of exemplary receiver circuitry of a reception
apparatus.
[fig. 10] Fig. 10 is a block diagram representation of exemplary receiver circuitry of a
reception apparatus using amplitude diversity.
[fig. 1l]Fig. 1 1 illustrates an exemplary reception apparatus.
[fig. 12] Fig. 12 is a block diagram showing an example of a hardware configuration of
a computer.
Description of Embodiments
[001 1] While the present disclosure is susceptible of embodiment in many different forms,
there is shown in the drawings and will herein be described in detail specific em
bodiments, with the understanding that the present disclosure of such embodiments is
to be considered as an example of the principles and not intended to limit the present
disclosure to the specific embodiments shown and described. In the description below,
like reference numerals are used to describe the same, similar or corresponding parts in
the several views of the drawings.
[0012] The terms "a" or "an", as used herein, are defined as one or more than one. The term
"plurality", as used herein, is defined as two or more than two. The term "another", as
used herein, is defined as at least a second or more. The terms "including" and/or
"having", as used herein, are defined as comprising (i.e., open language). The term
"coupled", as used herein, is defined as connected, although not necessarily directly,
and not necessarily mechanically. The term "program" or "computer program" or
similar terms, as used herein, is defined as a sequence of instructions designed for
execution on a computer system. A "program", or "computer program", may include a
subroutine, a program module, a script, a function, a procedure, an object method, an
object implementation, in an executable application, an applet, a servlet, a source code,
an object code, a shared library / dynamic load library and/or other sequence of in
structions designed for execution on a computer system.
[0013] Reference throughout this document to "one embodiment", "certain embodiments",
"an embodiment", "an implementation", "an example" or similar terms means that a
particular feature, structure, or characteristic described in connection with the em
bodiment is included in at least one embodiment of the present disclosure. Thus, the
appearances of such phrases or in various places throughout this specification are not
necessarily all referring to the same embodiment. Furthermore, the particular features,
structures, or characteristics may be combined in any suitable manner in one or more
embodiments without limitation.
[0014] The term "or" as used herein is to be interpreted as an inclusive or meaning any one
or any combination. Therefore, "A, B or C" means "any of the following: A; B; C; A
and B; A and C; B and C; A, B and C". An exception to this definition will occur only
when a combination of elements, functions, steps or acts are in some way inherently
mutually exclusive.
[0015] As technology advances, channel bandwidths and/or sampling frequencies used to
communicate data may change. These changes may result from factors such as a
change in communication scheme (e.g., different broadcasting techniques) or other
criteria (e.g., service provider specification). For example, the service provider may
choose an appropriate channel bandwidth for broadcasting 4K content or mobile
content. In another example, a service provider may control several adjacent channels
and could benefit from channel bonding.
[0016] In the last decade for example, the IEEE 802. 11 family includes many versions (a, b,
g, n, ac, etc.) where the modulation scheme is either OFDM or DSSS, the center
frequency is either 2.4 GHz or 5 GHz, the sampling frequency or data rate changed
from 1 Mbps to 780 Mbps, and the bandwidth has changed from 20 MHz to 160 MHz.
[0017] As the channel bandwidth and/or sampling frequency changes, devices are typically
replaced to take advantage of the technological advances. However, replacement of
such devices for each technological improvement is not only inflexible but costly and
wasteful. Thus, there is a need for indicating a-priori information, including the
bandwidth and sampling frequency, to account for different channel bandwidth options
because an initially set sampling frequency and bandwidth may not be constant
through the years, for example as apparent from the different versions of 802. 11. Em
bodiments of the present disclosure address these problems by providing the channel
bandwidth, sampling frequency, and/or multiplexing frequency to the reception
apparatus. This information may be provided along with, a separately from, an a s
sociated data stream.
[0018] The channel bandwidth and sampling frequency are included in a-priori information
and are needed by the reception apparatus to demodulate a received signal. Further, the
a-priori information optionally includes the multiplexing technique. In certain em
bodiments of the present disclosure, the-priori information is transmitted with the
signal. However, the a-priori information may be provided separately from the signal,
such as via a predetermined channel or by a predetermined server on the Internet. The
predetermined server may be a server that provides software updates to the reception
apparatus, provided by a service provider, or provided by specified entity such as the
FCC.
[0019] In certain embodiments, a-priori information is transmitted using a technique that
does not require prior knowledge of the channel bandwidth and/or the sampling
frequency by the reception apparatus. The a-priori information contains one or a com
bination of channel bandwidth and the sampling frequency. The a-priori information is
obtained before starting decoding at the reception apparatus. The reception apparatus
first processes the a-priori information to extract, or otherwise determine, the channel
bandwidth and the sampling frequency. The channel bandwidth and the sampling
frequency are then used in the decoding of digital information. The proposed method is
flexible and can be used with a variety of communication standards.
[0020] Fig. 1 illustrates components of a reception apparatus according to one embodiment.
A tuner 100 selects the radio frequency (RF) of a center channel from within a band of
transmitted RF signals. The tuner 100 rejects the unwanted out-of-band signals.
However, some channels adjacent to the center channel are also received. Graph 102
represents power spectral density (PSD) of the received RF signals. Graph 104
represents the PSD at the output of the tuner 100. The center channel is denoted by N.
As shown in the graph 104, some of the frequencies adjacent to the center channel N,
are present at the output of the tuner 100. Some portion of the neighboring channels
(N-l) and (N+l) remain due to the non-ideal nature of the band pass filter in the tuner
100.
[0021] The output signal from the tuner 100 is fed to an analog to digital converter (ADC)
108. The ADC 108 needs the sampling frequency to perform the analog to digital
conversion. The output signal from the ADC 108 is fed to the demodulator 106. The
demodulator 106 separates a standard baseband signal from the RF carrier that was
used to transmit it through a communication medium, for example air or a coaxial
cable. Using the standard developed by the Advanced Television Systems Committee
(ATSC), the bandwidth is fixed as regulated and thus known to the reception
apparatus. Once the tuner 100, is tuned to the desired frequency all of the energy in the
bandwidth is considered desired information. In current television systems, the
bandwidth is hardcoded by the manufacturer based on one or more standards im
plemented where the television system is to be used. Because the bandwidth is known,
the sampling frequency can be determined.
[0022] Fig. 2 illustrates a flow diagram of an exemplary method of a transmission apparatus
for transmitting a-priori information. At step S202, a user sets one or a combination of
a channel bandwidth and a sampling frequency. The user may be an operator of a
broadcasting station. For example, a broadcaster may own three adjacent channels and
may decide to combine the bandwidth of the channels. The transmission apparatus may
broadcast digital television broadcast signals in accordance with, for example,
standards set by the ATSC. At step S204, the transmission apparatus generates a
preamble. In one embodiment, the preamble includes the a-priori information. The
preamble may include a very small bandwidth signal that carries information, (e.g., 10
bits - 5 bits for sampling frequency, 5 bits for channel bandwidth).
[0023] The signal may be put on continuous pilots. In broadcasting systems, a pilot signal is
a signal, usually a single frequency, transmitted over a communications system for su
pervisory, control, equalization, continuity, synchronization, or reference purposes.
The continuous pilots have a known constant value that corresponds to specific frequencies.
In one embodiment, a phase change between a previous data carrier and the
continuous pilot may indicate "-1" and no phase change may indicate "+1". The
sampling frequency and the channel bandwidth are represented by their binary word
equivalent (e.g., the 10 bits described above). In one embodiment, the zero may be
mapped to "+1" and the one to "-1". In other embodiments the phase change in
dications and/or the mapping may be reversed, the number of continuous pilots cor
responds to different mode such as 8K, 16K, etc.
[0024] The a-priori information may be a chipped sequence with Gold codes that rides
below the noise. Gold codes are binary sequences that are highly orthogonal to one
another. The Gold codes strongly correlate, when they are exactly aligned. The Gold
codes are commonly used in satellite navigation and in code division multiple access
(CDMA) communication. The a-priori information is coded and then the coded a-priori
information is sent on the continuous pilots as explained above. The coded a-priori in
formation can be accumulated in time with a known Gold code or the like. Extracting
the a-priori information involves an FM demodulator adding accumulators in time with
a known code that has to vary across Doppler offsets and chip sequence offsets and
chip sequence offsets, which can add to channel change time.
[0025] In one embodiment, the a-priori information may be used with coded orthogonal
frequency division multiplexing (COFDM) based systems and the a-priori information
is transmitted in a chirp signal. In other embodiments, the a-priori information may be
transmitted using amplitude diversity.
[0026] The preamble may also include control, synchronization, information, or other
signaling data as would be understood by one of ordinary skill in the art. At step S206,
the preamble is appended to, or otherwise inserted into, an information signal or frame.
In another embodiment, the a-priori information is inserted into a portion of the in
formation signal or frame. At step S208, the signal (e.g., a digital television signal)
generated at step S206 is modulated and transmitted according to a communication
method as explained in detail later.
[0027] Fig. 3 illustrates a flow diagram of an exemplary method of a reception apparatus for
receiving a-priori information. At step S302, a signal is received by the reception
apparatus. For example, the reception apparatus receives a digital television broadcast
signal transmitted at step S208 through a wireless channel (e.g., a terrestrial broadcast
channel). The digital television broadcast signal includes audio/video content. At step
S304, the tuner selects an RF band (e.g., 20 MHz of UHF, VHF). At step S306, the
reception apparatus searches for, or otherwise detects, the a-priori information, as will
be explained later. At step S308, the a-priori information is extracted from the signal
(e.g., from the preamble). The extraction method depends on the type of method used
to transmit the a-priori information such as chirp signal, Gold code, QPSK codes, etc.
The reception apparatus may use a look-up table to obtain the channel bandwidth and
the sampling frequency based on the extracted a-priori information. At step S310, the
sampling frequency is provided to the ADC. The channel bandwidth is provided to the
tuner.
[0028] In one embodiment, the preamble and the a-priori information signal described above
are included in a digital television signal transmitted in a broadcasting system that
employs a COFDM scheme. COFDM is the same as OFDM except that forward error
correction is applied to the signal before transmission. OFDM is utilized in the ter
restrial digital TV broadcasting system DVB-T (used in Europe) and integrated
Services Digital Broadcasting for Terrestrial Television Broadcasting ISDB-T (used in
Japan). COFDM is expected to be used in the future implementation of ATSC 3.0,
which is now under discussion. COFDM is a multi-carrier modulation technique that
can provide good performance in some wireless environments. In COFDM, the
available bandwidth is divided into several orthogonal frequency sub-bands, which are
also called sub-carriers. The partial allocation of the data payload to each subcarrier
protects it against frequency selective fading. The number of sub-carriers may be
dependent on the standard used. For example, Digital Video Broadcasting for
Handhelds (DVB-H) uses 1705, 3409, or 6817 sub-carriers depending on the mode of
operation. ISDB-T uses 256, 512, or 1024 depending on the mode of operation.
[0029] Fig. 4 illustrates a preamble proposed by SONY Corporation that includes a-priori
information according to one embodiment. However, it should be noted that the apriori
information may be inserted into any other type of preamble or other portions of
a transmitted signal. The a-priori information is represented by one or more chirps. The
preamble includes a L I pre-signaling section 400, an emergency alert system (EAS)
section 402, and a LI post-signaling section 404. As shown the a-priori information
signal is inserted at the beginning of the L I pre-signaling section 400 according to one
embodiment. However, the a-priori information may be inserted in any other portion of
the preamble such as between any of the preamble sections or after the L I postsignaling
section.
[0030] A reception apparatus begins to demodulate the incoming signal after detecting the
preamble or GI which indicates the start of a COFDM frame. The reception apparatus
may use autocorrelation to find the start of the frame as the GI is a repeated portion of
the frame data. Inter symbol interference (ISI) may be canceled completely when the
cyclic prefix guard interval has a duration equal to or larger than the channel delay
spread. The CP is discarded at the reception apparatus, because it is only used to cancel
the effect of the ISI. The frame data may be encoded depending on the system used.
For example, the data may be BPSK, QPSK or QAM modulated. For example, in
DVB-T2, the subcarrier modulation scheme may be QPSK, 16-QAM, 64-QAM or
256-QAM.
[0031] In one embodiment, the preamble signal generated at step S204, includes a chirp
signal. The chirp signal is a signal that includes one or more chirp bursts in which the
frequency increases (up-chirp) or decreases (down-chirp) with time. A linear chirp may
be used. The chirp signal may be expressed as:
/ 0 ) = f +
where f0 is the starting frequency and k is the chirp rate and may be expressed as:
_ f f
where is the final frequency of the chirp at time ti. The chirp signal is similar to a
radar chirp in one embodiment.
[0032] Fig. 5A illustrates a chirp signal according to one embodiment. The starting
frequency or a burst may be chosen to be equal to a predetermined value. The prede
termined value may be equal to a predetermined lowest channel bandwidth, for
example as specified by a predetermined broadcasting standard (e.g., 5 MHz). The pre
determined value may be stored in a corresponding memory of the transmission and
the reception apparatus. The predetermined value may also be taken to equal to zero.
The chirp rate, which represents the rate of frequency increase, may be chosen based
on the sampling frequency. The final (highest) frequency is chosen to be equal to the
channel bandwidth obtained at step S202. A slope is defined as the difference between
the final frequency of the chirp minus the initial frequency of the chirp over the time
span of a burst (chirp period). For example, the chirp signal may start with a frequency
of 0MHz (f0=0MHz) to the final (highest) frequency of 6 MHz (fi=6MHz) which
represents the channel bandwidth. The chirp rate is taken to be 48/7, which represents
the sampling frequency fs. Thus, the chirp signal frequency should be varied from
0MHz to 6 MHz in a period of
The chirp signal may be generated digitally using a digital signal processor (DSP)
and a DAC using a direct digital synthesizer. Two or more bursts may be added to the
preamble of every frame or every Nth frame (where N is equal to 2 or greater). In Fig.
5A, two complete bursts 500, 502 are shown. Also, a partial burst 504 is shown.
[0033] The number of bursts may be based on the desired preamble size. The reception
apparatus may use multiple bursts to identify the boundaries of a burst. The reception
apparatus detects a change in the frequency to identify the beginning of the burst. Once
the beginning of the burst is identified, the reception apparatus can detect the
maximum frequency and the period of the burst. For example, the reception apparatus
determines a starting boundary of the second burst using the first burst, and an ending
boundary of the second burst using the following partial burst.
[0034] Fig. 5B illustrates a two-tone signal according to one embodiment. In one em
bodiment, the preamble signal includes the two-tone signal. Two or more bursts are
included in the preamble of every frame. Each burst may start with a frequency equal
to a predetermined value, which represents a first tone 506. The predetermined value
may be equal to a predetermined lowest channel bandwidth, for example as specified
by a predetermined broadcasting standard (e.g., 5 MHz). A second tone 508 has a
frequency equal to the channel bandwidth. The period T may be chosen to be equal to
ChannelBandwidth
SamplingFrequencyvalue
For example,
T = = 0.875/^
(48/7)
As another example, if the channel bandwidth that needs to be transmitted to the
receiver is 20 MHz and the sampling frequency is 48/7 MHz, then the period is chosen
as
1 = - = 2.9 1
(48/ 7) .
[0035] The chirp signal is repeated every COFDM frame according to one embodiment. The
preamble also contains data to indicate the type of data transmitted for example, audio,
video, and WiFi. The chirp signal may be inserted before or after the preamble of
signaling data included in the preamble. The chirp signal may be also generated using
analog circuitry.
[0036] Fig. 6 illustrates a time domain and magnitude spectrum of a chirp signal according
to one embodiment. The chirp signal is an FM signal with linear frequency
modulation. The reception apparatus include a FM demodulator tuned to the low 'chirp'
frequency (5MHz) to extract the 'chirp' and recover the channel bandwidth and the
sampling frequency. Trace 600 shows the real part of the chirp signal. Trace 602 shows
the magnitude spectrum of the chirp signal in the frequency domain. The limits
indicated in trace 602 show the portion used for the channel bandwidth estimation.
[0037] Fig. 7 illustrates a block diagram of a transmission apparatus. The transmission
apparatus may be used, for example, to transmit video images and audio signals in ac
cordance with the proposed ATSC 3.0 standard, DVB-T, Digital Video Broadcasting
for Handhelds (DVB-H), DVB-T2, or DVB-C2 standards. The transmission apparatus
includes a COFDM modulator 700, a preamble insertion module 704, a DAC 706, and
an antenna 708. The COFDM modulator 700 is further illustrated in Fig. 8. The
preamble insertion module 704 inserts the system parameters including the a-priori in
formation signal. The digital signal is transformed into an analog signal by the DAC
706 and then modulated to radio frequency. In other embodiments, the a-priori in
formation is inserted as an analog signal after the DAC 706. For example, a chirp
signal representing the a-priori information is inserted into the analog signal according
to a predetermined timing.
[0038] Fig. 8 illustrates an ATSC 3.0 physical layer architecture according to one em
bodiment. ATSC 3.0 is expected to improve and add functionality for broadcast
television. A framer 800 combines multiple input streams into a frame with many
physical layers or pipes. The scheduler 802 and scrambler 804 place the frames in a
selected order and scrambles data per pipe. A forward error correction unit 806 adds
information data protection per pipe. A bit interleaver 808 randomizes data bit
placement within a pipe to reduce a channel's effect. A mapper unit 810 assigns a
group of data bits to a symbol per pipe. A time interleaver unit 812 randomizes
symbols per pipe to reduce the channel's effect. An OFDM framer 814 combines
multiple inputs into a single stream and format it is frames. A frequency interleaver
randomizes data cells to reduce the channel's effect. A pilots insertion unit inserts
pilots and reserved tones for channel estimation and synchronization. Then, the
preamble that includes the a-priori information may be inserted. An IFFT unit 822
generates the COFDM waveform. The GI insertion unit inserts a repeated portion of
the COFDM waveform. The guard interval is used to combat ISI and inter-carrier in
terference (ICI) caused by delay spread in a communication channel. The GI length
may be chosen to match the level of multipath expected. For example, in digital audio
broadcasting (DAB), the guard interval length is chosen as one fourth of the receiver
integration period. DVB-H and ISDB-T support four different guard lengths of 1/4,
1/8, 1/16, and 1/32 of a COFDM symbol or frame data. Control information provides
the COFDM with parameters. For example, the control information may indicate the
level of protection for certain data. The modulation type is then chosen according to
the level of protection. For example, for high protection the modulation type is chosen
as QPSK.
[0039] Fig. 9 is a block diagram of exemplary receiver circuitry of a reception apparatus. In
one embodiment, the receiver circuitry is part of a digital television receiver device
that is incorporated into a fixed or mobile device such as a television set, a set top box,
smartphone, tablet computer, laptop, portable computer, or any other device configured
to receive television content. The receiver circuitry receives a digital television
broadcast signal from one or more transmission apparatuses via, for example, a ter
restrial broadcast.
[0040] An antenna 912 receives the modulated signal from the transmission apparatus
described in Fig. 7 and provides the modulated signal to a tuner 900. An FM de
modulator 902 is tuned to a predetermined channel bandwidth. The predetermined
channel bandwidth is stored in a memory. The predetermined channel bandwidth may
be the low 'chirp' frequency. In other embodiments, the FM demodulator 902 may step
through frequencies to find the channel bandwidth. The output of the FM demodulator
902 shows an offset. The offset indicates the actual channel bandwidth. For the
example, as discussed above, the offset is equal to 6 MHz, which indicates that the
channel bandwidth is 6 MHz. In another embodiment, instead of an offset, the
maximum frequency itself indicates the actual channel bandwidth.
[0041] The output of the FM demodulator 902 is fed to an a-priori key processor 906. The apriori
key processor 906 extracts the signal period to deduce the sampling frequency.
The a-priori key processor 906 outputs the channel bandwidth to the tuner 900 and the
sampling frequency to the ADC 904. The a-priori key processor may use a K-map
table stored in the memory to find the sampling frequency and channel bandwidth. An
exemplary k-map table is shown below.
[Table 1]
Frequency (M H )
Table : K-map table r sampling frequency retrieval
[0042] The FM demodulator 902 may also accumulate two or more bursts, for example, in
the case of a low energy channel, which permits operation close to the noise level. The
sampling frequency is calculated from the period as explained above. The sampling
frequency is used by an analog-to digital converter (ADC) 904 to convert the COFDM
signal into a digital form.
[0043] A COFDM demodulator 908 detects the guard interval for the COFDM transmission
in order to place an FFT window in each COFDM symbol period. In the COFDM de
modulator 908, a FFT unit performs an FFT on the COFDM symbols received and
provides frequency domain symbols. Then a receiver (Rx) data processor 910
processes (e.g., symbol demaps, deinterleaves, and decodes) the data symbol estimates
and provides decoded data. Although not shown in Fig. 9, the receiver circuitry may
include other processing units for timing acquisition, filtering, sample rate conversion,
direct current (DC) offset removal, frame detection, frame synchronization, and/or
other functions.
[0044] In selected embodiments, amplitude diversity also known as antenna diversity may
be used with COFDM. Antenna diversity is any one of several wireless diversity
schemes that use two or more antennas to improve the quality and reliability of a
wireless link. The channel bandwidth and the sampling frequency may be coded in the
LI -Pre signaling part of the COFDM signal. The preamble may be coded using a
QPSK (e.g., using the in-phase components of QPSK only, that is BPSK to send codes
of the sampling frequency and channel bandwidth) scheme with 1/2 code rate forward
error correction (FEC). The channel bandwidth and the sampling frequency may be
coded with a small amount of bits.
[0045] Fig. 10 is a block diagram of an exemplary receiver circuitry of a reception apparatus
using amplitude diversity. Fig. 10 shows two antennas 1014, 1016. Antennas 1014,
1016 continuously receive a signal from a transmission apparatus. Although two
antennas are shown in Fig. 10, the receiver circuitry using amplitude diversity may
include two or more antennas. The signal from each antenna may be multiplied by a
combining gain. The combining gain may be made proportional to the rms signal level
and inversely proportional to the mean square noise level in that channel. Each of the
signals received by antennas 1014, 1016 then has a different combining gain. In other
embodiments, the combination gain for all signals may set to the same value and not
changed thereafter. The signals are then co-phased using delays 1002, 1004 prior to
summing in order to ensure that all signals are added in phase for maximum diversity
gain. The summed signals are then used as the received signal. Further, in one em
bodiment, amplitude diversity is not required and only a single antenna is used. The
received signal is then fed to the tuner 1006. To retrieve the quadrature phase, from the
received signal, a Hilbert transform may be used. The Hilbert transform shifts the
received signal 90 degrees and retrieves the quadrature- phase samples from the inphase
samples. In order to avoid using a digital Hilbert transform unit, the in-phase
samples from the received signal should be used in one embodiment. Then, the signal
output from the tuner 1006 is fed to an envelope detector 1008. The envelope detector
1008 is an electronic circuit that takes a high frequency signal as input and provides an
output which is the envelope of the original signal. The envelope detector 1008 may
include a diode feeding an LC circuit. The diode may be connected to a resistor and a
capacitor in parallel from the output of the circuit to a ground. The output from the
envelope detector 1008 will be "1" or "0".
[0046] The output from the envelope detector 1008 is fed to a-priori key processor 1018.
The a-priori key processor 1018 retrieves the coded channel bandwidth and the
sampling frequency as the output from the envelope detector is the binary repre
sentation of the sampling frequency and the channel bandwidth. Once the coded
channel bandwidth and sampling frequency are retrieved from the a-priori key
processor 1008, the one or more codes are compared with a look-up table stored in the
memory to retrieve the channel bandwidth and the sampling frequency. In one embodiment,
5 BPSK symbols may be used to represent the sampling frequency and 5
BPSK symbols may be used to represent the channel bandwidth. Thus, a first look-up
table with 32 entries (2 5) may be used to retrieve the sampling frequency. Similarly, a
second look-up table with 32 entries (2 5) may be used to retrieve the channel
bandwidth. The channel bandwidth is then fed to the tuner 1006 to retrieve the signal.
The sampling frequency is fed to the ADC 1010. The output from the ADC 1010 is fed
to the demodulator 1012.
[0047] The receiver circuitry illustrated in Figs. 9 and 10 generally operate under control of
at least one processor, such as a CPU, which is coupled to memory, program memory,
and a graphics subsystem via one or more buses. An exemplary computer for con
trolling the receiver circuitry is further described below with respect to Fig. 12.
[0048] Fig. 11 illustrates an exemplary reception apparatus. The reception apparatus
includes a digital television receiver device that is incorporated into a fixed or mobile
device such as a television set, a set top box, smartphone, tablet computer, laptop,
portable computer, or any other device configured to receive television content.
[0049] The reception apparatus includes a tuner / demodulator 1102, which receives digital
television broadcast signals from one or more content sources (e.g., content source)
via, for example, a terrestrial broadcast. The tuner / demodulator 1102 includes one of
the receiver circuitry illustrated in Figs. 9 or 10 in certain embodiments. Depending on
the embodiment, the reception apparatus may alternatively or additionally be
configured to receive a cable television transmission or a satellite broadcast. The tuner
/ demodulator 1102 receives a signal, including for example an MPEG-2 TS or IP
packets, which may be demultiplexed by the demultiplexer 1104 or handled by
middleware and separated into audio and video (A/V) streams. The audio is decoded
by an audio decoder 1110 and the video is decoded by a video decoder 1114. Further,
uncompressed A/V data may be received via an uncompressed A/V interface (e.g., a
HDMI interface), if available.
[0050] In one embodiment, the received signal (or stream) includes supplemental data such
as one or a combination of closed caption data, a triggered declarative object (TDO), a
trigger, a virtual channel table, EPG data, NRT content, etc. Examples of the TDO and
trigger are described in ATSC Candidate Standard: Interactive Services Standard
(A/105:2014), S13-2-389r7, which is incorporated herein by reference in its entirety.
The supplemental data are separated out by the demultiplexer 1104. However, the A/V
content and/or the supplemental data may be received via the Internet 1130 and a
network interface 1126.
[0051] A storage unit may be provided to store non real time content (NRT) or Internetdelivered
content such as Internet Protocol Television (IPTV). The stored content can
be played by demultiplexing the content stored in the storage unit by the demultiplexer
1104 in a manner similar to that of other sources of content. Alternatively, the stored
content may be processed and presented to the user by the CPU 1138. The storage unit
may also store any other supplemental data acquired by the reception apparatus.
[0052] The reception apparatus generally operates under control of at least one processor,
such as the CPU 1138, which is coupled to a working memory 1140, program memory
1142, and a graphics subsystem 1144 via one or more buses (e.g., bus 1150). The CPU
1138 receives closed caption data from the demultiplexer 1104 as well as any other
supplemental data used for rendering graphics, and passes appropriate instructions and
data to the graphics subsystem 1144. The graphics outputted by the graphics subsystem
1144 are combined with video images by the compositor and video interface 1160 to
produce an output suitable for display on a video display.
[0053] Further, the CPU 1138 operates to carry out functions of the reception apparatus
including the processing of NRT content, triggers, TDOs, EPG data, etc. For example,
the CPU 1138 operates to execute script objects (control objects) contained in the
TDO, its trigger(s), etc., using for example a Declarative Object (DO) Engine stored in
the program memory 1142.
[0054] Although not illustrated in Fig. 11, the CPU 1138 may be coupled to any one or a
combination of the reception apparatus resources to centralize control of one or more
functions. In one embodiment, the CPU 1138 also operates to oversee control of the
reception apparatus including the tuner / demodulator 1102 and other television
resources.
[0055] Fig. 12 is a block diagram showing an example of a hardware configuration of a
computer that can be configured to perform functions of any one or a combination of
reception apparatus and transmission apparatus. For example, in one embodiment, the
computer is configured to perform the functions in the digital domain, such as the
COFDM modulator 700, preamble insertion module 704, COFDM demodulator 908, a
priori key processor 906 and receiver data processor 910.
[0056] As illustrated in Fig. 12 the computer includes a central processing unit (CPU) 1202,
read only memory (ROM) 1204, and a random access memory (RAM) 1206 inter
connected to each other via one or more buses 1208. The one or more buses 1208 are
further connected with an input-output interface 1210. The input-output interface 1210
is connected with an input portion 1212 formed by a keyboard, a mouse, a microphone,
remote controller, etc. The input-output interface 1210 is also connected an output
portion 1214 formed by an audio interface, video interface, display, speaker and the
like; a recording portion 1216 formed by a hard disk, a non-volatile memory or other
non-transitory computer readable storage medium; a communication portion 1218
formed by a network interface, modem, USB interface, fire wire interface, etc. ; and a
drive 1220 for driving removable media 1222 such as a magnetic disk, an optical disk,
a magneto-optical disk, a semiconductor memory, etc.
[0057] According to one embodiment, the CPU 1202 loads a program stored in the
recording portion 1216 into the RAM 1206 via the input-output interface 1210 and the
bus 1208, and then executes a program configured to provide the functionality of the
one or combination of the content source, the reception apparatus, and the transmission
apparatus.
[0058] A method which includes the features in the foregoing description provides
numerous advantages. In particular, the method and apparatus determines the channel
bandwidth and the sampling frequency from the preamble signal. The present
disclosure has the advantage of not requiring the a-priori knowledge of the sampling
frequency and the channel bandwidth. The broadcaster may easily change the
bandwidth by changing the chirp signal. The reception apparatus may receive
broadcasting signals with a plurality of channel bandwidths. The broadcaster has the
flexibility to control the channel bandwidth.
[0059] As described above, embodiments of the present disclosure include a plurality of
different ways for generating a-priori keys, including the use of a 'chirp' frequency and
amplitude diversity. In certain embodiments, the 'chirp' frequency implementation
spans the channel raster to mitigate frequency fading, is located in every preamble to
mitigate dropouts in time, allows for a simple FM demodulator at a receiver to extract
a-priori information of channel bandwidth and sampling frequency, and may allow ac
cumulated correlations to build up information out of the noise due to the repetitive
nature of same data.
[0060] Further, in certain embodiments, for the amplitude diversity implementation, the
QPSK modulated data with code rate 1/2 protected signaling may be done digitally,
delay and multiply circuits can be done to extract this data before an A/D, and may
allow accumulated correlations to build up information out of the noise due to the
repetitive nature of same data. Moreover, embodiments of the present disclosure
provide a manner of standardizing signal starting points to enable full flexibility for
future growth, providing such signaling in a compact way to reduce overhead, and
signaling starting point options before the digital samples are taken at receivers.
[0061] Numerous modifications and variations of the present disclosure are possible in light
of the above teachings. It is therefore to be understood that within the scope of the
appended claims, the present disclosure may be practiced otherwise than as specifically
described herein.
[0062] The above disclosure also encompasses the embodiments noted below.
[0063] (1) A method for transmitting a-priori information, the method including generating,
by circuitry of a transmission apparatus, the a-priori information based on a sampling
frequency and a channel bandwidth of a signal to be transmitted; appending, by the
circuitry, the a-priori information to a data signal; and transmitting, by the circuitry, the
data signal including the appended a-priori information to a reception apparatus.
(2) The method of feature (1), in which the step of generating includes generating a
chirp signal that represents the a-priori information, the chirp signal including at least
one burst with a chirp rate equal to the sampling frequency and with a maximum
frequency equal to the channel bandwidth.
(3) The method of feature (2), in which the chirp signal includes at least two identical
bursts.
(4) The method of feature (3), in which the beginning of one of the at least two
identical bursts is detected by a change in frequency between two of the at least two
identical bursts.
(5) The method of any of features (2) to (4), in which the chirp signal is appended to a
COFDM frame.
(6) The method of feature (5), in which the chirp signal is appended to a preamble of
the COFDM frame.
(7) The method of feature (1), in which the step of generating includes generating
binary code that represents the a-priori information, including the sampling frequency
and the channel bandwidth; and setting a phase of a continuous pilot based on the
binary code.
(8) The method of feature (7), in which the a-priori information is coded and ac
cumulated in time with a Gold code.
(9) A method for receiving a-priori information, the method including receiving, by
circuitry of a reception apparatus, a transmitted signal, the transmitted signal including
a-priori information appended to a data signal; detecting, by the circuitry, the a-priori
information included in the transmitted signal; and determining a sampling frequency
and a channel bandwidth associated with the transmitted signal based on the detected
a-priori information.
(10) The method of feature (9), further including adjusting a tuner that receives the
transmitted signal based on the determined channel bandwidth; and performing analog
to digital conversion of the received signal based on the determined sampling
frequency.
(11) The method of feature (9) or (10), in which the step of detecting includes
detecting a chirp signal that represents the a-priori information, the chirp signal
including at least one burst with a chirp rate equal to the sampling frequency and with
a maximum frequency equal to the channel bandwidth.
(12) The method of feature ( 11), in which the step of detecting includes performing
FM demodulation of the transmitted signal.
(13) The method of feature ( 11), in which the chirp signal includes at least two
identical bursts.
(14) The method of feature (13), in which the beginning of one of the at least two
identical bursts is detected by a change in frequency between two of the at least two
identical bursts.
(15) The method of any of features ( 11) to (14), in which the chirp signal is appended
to a COFDM frame.
(16) The method of feature (15), in which the chirp signal is appended to a preamble of
the COFDM frame.
(17) The method of feature (9), in which the step of detecting includes detecting a
phase of a continuous pilot, comparing the phase of the continuous pilot with a
previous data carrier, detecting a first code in response to determining that there is a
phase change, detecting a second code in response to determining that there is no phase
change, and retrieving one of the sampling frequency and the channel bandwidth using
a look-up table based on the detected code.
(18) The method of feature (17), in which the detected code represents coded a-priori
information, and the step of detecting the a-priori information further includes accu
mulating the detected code with a Gold code stored in a memory.
(19) A transmission apparatus, including circuitry configured to: generate a-priori in
formation based on a sampling frequency and a channel bandwidth of a data signal to
be transmitted; append the a-priori information to the data signal; and transmit the data
signal including the appended a-priori information to a reception apparatus.
(20) The transmission apparatus of feature (19), in which the circuitry is configured to
generate a chirp signal that represents the a-priori information, the chirp signal
including at least one burst with a chirp rate equal to the sampling frequency and with
a maximum frequency equal to the channel bandwidth.
(21) The transmission apparatus of feature (20), in which the chirp signal includes at
least two identical bursts.
(22) The transmission apparatus of feature (21), in which the beginning of one of the at
least two identical bursts is detected by a change in frequency between two of the at
least two identical bursts.
(23) The transmission apparatus of any of features (20) to (22), in which the chirp
signal is appended to a COFDM frame.
(24) The transmission apparatus of feature (23), in which the chirp signal is appended
to a preamble of the COFDM frame.
(25) The transmission apparatus of feature (19), in which the circuitry is configured to
generate a binary code that represents the a-priori information, including the sampling
frequency and the channel bandwidth; and setting a phase of a continuous pilot based
on the binary code.
(26) The transmission apparatus of feature (25), in which the a-priori information is
coded and accumulated in time with a Gold code.
(27) A reception apparatus, including circuitry configured to: receive a transmitted
signal, the transmitted signal including a-priori information appended to a data signal;
detect the a-priori information included in the transmitted signal; and determine a
sampling frequency and a channel bandwidth associated with the transmitted signal
based on the detected a-priori information.
(28) The reception apparatus of feature (27), in which the circuitry is configured to
adjust a tuner that receives the transmitted signal based on the determined channel
bandwidth; and perform analog to digital conversion of the received signal based on
the determined sampling frequency.
(29) The reception apparatus of feature (27) or (28), in which the circuitry is
configured to detect a chirp signal that represents the a-priori information, the chirp
signal including at least one burst with a chirp rate equal to the sampling frequency and
with a maximum frequency equal to the channel bandwidth.
(30) The reception apparatus of feature (29), in which the circuity is configured to
perform FM demodulation of the transmitted signal.
(31) The reception apparatus of feature (30), in which the chirp signal includes at least
two identical bursts.
(32) The reception apparatus of feature (31), in which the beginning of one of the at
least two identical bursts is detected by a change in frequency between two of the at
least two identical bursts.
(33) The reception apparatus of any of features (29) to (32), in which the chirp signal is
appended to a COFDM frame.
(34) The reception apparatus of feature (33), in which the chirp signal is appended to a
preamble of the COFDM frame.
(35) The reception apparatus of feature (27), in which the circuitry is configured to
detect a phase of a continuous pilot, compare the phase of the continuous pilot with a
previous data carrier, detect a first code in response to determining that there is a phase
change, detect a second code in response to determining that there is no phase change,
and retrieve one of the sampling frequency and the channel bandwidth using a look-up
table based on the detected code.
(36) The reception apparatus of feature (35), in which the detected code represents
coded a-priori information, and the step of detecting the a-priori information further
includes accumulating the detected code with a Gold code stored in a memory.

Claims
A method for transmitting a-priori information, the method comprising:
generating, by circuitry of a transmission apparatus, the a-priori in
formation based on a sampling frequency and a channel bandwidth of a
signal to be transmitted;
appending, by the circuitry, the a-priori information to a data signal;
and
transmitting, by the circuitry, the data signal including the appended apriori
information to a reception apparatus.
The method of claim 1, wherein the step of generating comprises:
generating a chirp signal that represents the a-priori information, the
chirp signal including at least one burst with a chirp rate equal to the
sampling frequency and with a maximum frequency equal to the
channel bandwidth.
The method of claim 2, wherein the chirp signal includes at least two
identical bursts.
The method of claim 3, wherein the beginning of one of the at least two
identical bursts is detected by a change in frequency between two of the
at least two identical bursts.
The method of claim 2, wherein the chirp signal is appended to a
COFDM frame.
The method of claim 5, wherein the chirp signal is appended to a
preamble of the COFDM frame.
The method of claim 1, wherein the step of generating comprises:
generating binary code that represents the a-priori information,
including the sampling frequency and the channel bandwidth; and
setting a phase of a continuous pilot based on the binary code.
The method of claim 7, wherein the a-priori information is coded and
accumulated in time with a Gold code.
A method for receiving a-priori information, the method comprising:
receiving, by circuitry of a reception apparatus, a transmitted signal, the
transmitted signal including a-priori information appended to a data
signal;
detecting, by the circuitry, the a-priori information included in the
transmitted signal; and
determining a sampling frequency and a channel bandwidth associated
with the transmitted signal based on the detected a-priori information.
PCT7JP2015/005905
The method of claim 9, further comprising:
adjusting a tuner that receives the transmitted signal based on the de
termined channel bandwidth; and
performing analog to digital conversion of the received signal based on
the determined sampling frequency.
The method of claim 9, wherein the step of detecting comprises:
detecting a chirp signal that represents the a-priori information, the
chirp signal including at least one burst with a chirp rate equal to the
sampling frequency and with a maximum frequency equal to the
channel bandwidth.
The method of claim 11, wherein the step of detecting comprises:
performing FM demodulation of the transmitted signal.
The method of claim 11, wherein the chirp signal includes at least two
identical bursts.
The method of claim 13, wherein the beginning of one of the at least
two identical bursts is detected by a change in frequency between two
of the at least two identical bursts.
The method of claim 11, wherein the chirp signal is appended to a
COFDM frame.
The method of claim 15, wherein the chirp signal is appended to a
preamble of the COFDM frame.
The method of claim 9, wherein the step of detecting comprises:
detecting a phase of a continuous pilot,
comparing the phase of the continuous pilot with a previous data
carrier,
detecting a first code in response to determining that there is a phase
change,
detecting a second code in response to determining that there is no
phase change, and
retrieving one of the sampling frequency and the channel bandwidth
using a look-up table based on the detected code.
The method of claim 17, wherein
the detected code represents coded a-priori information, and
the step of detecting the a-priori information further includes accu
mulating the detected code with a Gold code stored in a memory.
A transmission apparatus, comprising
circuitry configured to:
generate a-priori information based on a sampling frequency and a
WO 2016/092761 PCT/JP2015/005905
channel bandwidth of a data signal to be transmitted;
append the a-priori information to the data signal; and
transmit the data signal including the appended a-priori information to
a reception apparatus.
[Claim 20] A reception apparatus, comprising
circuitry configured to:
receive a transmitted signal, the transmitted signal including a-priori in
formation appended to a data signal;
detect the a-priori information included in the transmitted signal; and
determine a sampling frequency and a channel bandwidth associated
with the transmitted signal based on the detected a-priori information.