Communication system
First Claim
1. A digital TV receiver comprising:
- a receiving section for receiving a PSK (Phase Shift Key) modulation signal comprising a plurality of signal points disposed on specific phases of a given constellation in a signal space diagram;
a demodulator for demodulating the received signal from said receiving section into a digital signal;
an error correcting section for error correcting a demodulation signal from said demodulator; and
an image expander for expanding an error-corrected signal from said error correcting section to a video signal, thereby outputting a video signal, wherein said demodulator demodulates the received signal as first and second PSK signals, said first PSK signal representing a first data stream to be reproduced, said first PSK signal comprising n-value signal points, said second PSK signal representing both said first data stream and a second data stream to be reproduced, said second PSK signal comprising m-value signal points, where m is an integer larger than n, wherein the m-value signal points of said second PSK signal are divisible into n groups of signal points which are distinguishable from one another in the signal space, and said demodulator distinguishes said n groups of signal points from one another as the n-value signal points of said first PSK signal by demodulating the received signal as said first PSK signal, and wherein high priority information is demodulated at least in said first data stream.
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Abstract
At the transmitter side, carrier waves are modulated according to an input signal for producing relevant signal points in a signal space diagram. The input signal is divided into, two, first and second, data streams. The signal points are divided into signal point groups to which data of the first data stream are assigned. Also, data of the second data stream are assigned to the signal points of each signal point group. A difference in the transmission error rate between first and second data streams is developed by shifting the signal points to other positions in the space diagram expressed at least in the polar coordinate system. At the receiver side, the first and/or second data streams can be reconstructed from a received signal. In TV broadcast service, a TV signal is divided by a transmitter into, low and high, frequency band components which are designated as a first and a second data streams respectively. Upon receiving the TV signal, a receiver can reproduce only the low frequency band component or both the low and high frequency band components, depending on its capability. Furthermore, a communication system based on an OFDM system is utilized for data transmission of a plurality of subchannels, wherein the subchannels are differentiated by changing the length of a guard time slot or a carrier wave interval of a symbol transmission time slot, or changing the transmission electric power of the carrier.
105 Citations
11 Claims
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1. A digital TV receiver comprising:
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a receiving section for receiving a PSK (Phase Shift Key) modulation signal comprising a plurality of signal points disposed on specific phases of a given constellation in a signal space diagram;
a demodulator for demodulating the received signal from said receiving section into a digital signal;
an error correcting section for error correcting a demodulation signal from said demodulator; and
an image expander for expanding an error-corrected signal from said error correcting section to a video signal, thereby outputting a video signal, wherein said demodulator demodulates the received signal as first and second PSK signals, said first PSK signal representing a first data stream to be reproduced, said first PSK signal comprising n-value signal points, said second PSK signal representing both said first data stream and a second data stream to be reproduced, said second PSK signal comprising m-value signal points, where m is an integer larger than n, wherein the m-value signal points of said second PSK signal are divisible into n groups of signal points which are distinguishable from one another in the signal space, and said demodulator distinguishes said n groups of signal points from one another as the n-value signal points of said first PSK signal by demodulating the received signal as said first PSK signal, and wherein high priority information is demodulated at least in said first data stream. - View Dependent Claims (2, 3, 4)
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5. A digital TV receiver comprising:
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a receiving section for receiving a PSK (Phase Shift Key) modulation signal comprising m-value signal points disposed on specific phases of a given constellation in a signal space diagram and representing a first data stream and a second data stream to be reproduced;
a demodulator for demodulating said PSK modulation signal from said receiving section into a digital signal;
an error correcting section for error correcting a demodulation signal from said demodulator; and
an image expander for expanding an error-corrected signal from said error correcting section to a video signal, wherein said demodulator includes means for demodulating said PSK signal comprising m-value signal points as another PSK signal, said another PSK signal comprising n-value signal points and representing only said first data stream, where n is an integer smaller than m, and wherein high priority information is demodulated at least in said first data stream.
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6. A signal transmission apparatus for transmitting a first data stream and a second data stream, said signal transmission apparatus comprising:
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a first error correction code (ECC) encoder operable to encode the second data stream to produce a first encoded data stream;
an interleaver operable to interleave the first encoded data stream to produce an interleaved data stream;
a second error correction code (ECC) encoder operable to encode the interleaved data stream to produce a second encoded data stream;
a modulator operable to assign each of the first data stream and the second encoded data stream to a respective constellation in a vector space diagram to produce modulated signals wherein the number of signal points of the constellation for the first data stream is different from the number of signal points of the constellation for the second encoded data stream;
an Inverse Fast Fourier Transformer (IFFT) operable to convert the modulated signals into an IFFT converted signal according to Orthogonal Frequency Division Multiplexing; and
a transmitter operable to transmit the IFFT converted signal, wherein the first data stream has data for demodulation including the number of signal points of the constellation for the second encoded data stream.
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7. A signal receiving apparatus comprising:
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a Fast Fourier Transformer (FFT) operable to convert a received signal into a FFT converted signal according to Orthogonal Frequency Division Multiplexing, the received signal having information of a first data stream and an encoded data stream, wherein each of the first data stream and the encoded data stream is assigned to a respective constellation in a vector space diagram, and the number of signal points of the constellation for the first data stream is different from the number of signal points of the constellation for the encoded data stream, and the first data stream having data for demodulation including the number of signal points of the constellation for the encoded data stream;
a demodulator operable to demodulate the FFT converted signal to produce the first data stream and the encoded data stream, wherein the encoded data stream is produced according to the data for demodulation;
a first error correction code (ECC) decoder operable to decode the encoded data stream to produce a first decoded data stream;
a de-interleaver operable to de-interleave the first decoded data stream to produce a de-interleaved data stream; and
a second error correction code (ECC) decoder operable to decode the de-interleaved data stream to produce a second decoded data stream.
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8. A signal transmission system for transmitting and receiving a first data stream and a second data stream, the system comprising a signal transmission apparatus and a signal receiving apparatus,
said signal transmission apparatus comprising: -
a first error correction code (ECC) encoder operable to encode the second data stream to produce a first encoded data stream;
an interleaver operable to interleave the first encoded data stream to produce an interleaved data stream;
a second error correction code (ECC) encoder operable to encode the interleaved data stream to produce a second encoded data stream;
a modulator operable to assign each of the first data stream and the second encoded data stream to a respective constellation in a vector space diagram to produce modulated signals wherein the number of signal points of the constellation for the first data stream is different from the number of signal points of the constellation for the second encoded data stream;
an Inverse Fast Fourier Transformer (IFFT) operable to convert the modulated signals into an IFFT converted signal according to Orthogonal Frequency Division Multiplexing; and
a transmitter operable to transmit the IFFT converted signal, and said signal receiving apparatus comprising;
a Fast Fourier Transformer (FFT) operable to convert the IFFT converted signal into a FFT converted signal according to Orthogonal Frequency Division Multiplexing;
a demodulator operable to demodulate the FFT converted signal to produce the first data stream and the second encoded data stream, wherein the second encoded data stream is produced according to the data for demodulation;
a first error correction code (ECC) decoder operable to decode the second encoded data stream to produce the interleaved data stream;
a de-interleaver operable to de-interleave the interleaved data stream to produce the first encoded data stream; and
a second error correction code (ECC) decoder operable to decode the first encoded data stream to produce the second data stream, wherein the first data stream has data for demodulation including the number of signal points of the constellation for the second encoded data stream.
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9. A signal transmission method for transmitting a first and a second data stream, comprising:
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first error correction code (ECC) encoding the second data stream to produce a first encoded data stream;
interleaving the first encoded data stream to produce an interleaved data stream;
second error correction code (ECC) encoding the interleaved data stream to produce a second encoded data stream;
assigning each of the first data stream and the second encoded data stream to a respective constellation in a vector space diagram to produce modulated signals wherein the number of signal points of the constellation for the first data stream is different from the number of signal points of the constellation for the second encoded data stream;
converting the modulated signals into an IFFT (Inverse Fast Fourier Transform) converted signal according to Orthogonal Frequency Division Multiplexing; and
transmitting the IFFT converted signal, wherein the first data stream has data for demodulation including the number of signal points of the constellation for the second encoded data stream.
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10. A signal receiving method comprising:
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converting a received signal into a FFT (Fast Fourier Transform) converted signal according to Orthogonal Frequency Division Multiplexing, the received signal having information of a first data stream and an encoded data stream, wherein each of the first data stream and the encoded data stream is assigned to a respective constellation in a vector space diagram, and the number of signal points of the constellation for the first data stream is different from the number of signal points of the constellation for the encoded data stream, and the first data stream having data for demodulation including the number of signal points of the constellation for the encoded data stream;
demodulating the FFT converted signal to produce the first data stream and the encoded data stream, wherein the encoded data stream is produced according to the data for demodulation;
first error correction code (ECC) decoding the encoded data stream to produce a first decoded data stream;
de-interleaving the first decoded data stream to produce a de-interleaved data stream; and
second error correction code (ECC) decoding the de-interleaved data stream to produce a second decoded data stream.
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11. A signal transmitting and receiving method for transmitting and receiving a first data stream and a second data stream, the method comprising a signal transmission method and a signal receiving method,
said signal transmission method comprising: -
first error correction code (ECC) encoding the second data stream to produce a first encoded data stream;
interleaving the first encoded data stream to produce an interleaved data stream;
second error correction code (ECC) encoding the interleaved data stream to produce a second encoded data stream;
assigning each of the first data stream and the second encoded data stream to a respective constellation in a vector space diagram to produce modulated signals wherein the number of signal points of the constellation for the first data stream is different from the number of signal points of the constellation for the second encoded data stream;
converting the modulated signals into an IFFT (Inverse Fast Fourier Transform) converted signal according to Orthogonal Frequency Division Multiplexing; and
transmitting the IFFT converted signal, and said signal receiving method comprising;
converting the IFFT converted signal into a FFT (Fast Fourier Transform) converted signal according to Orthogonal Frequency Division Multiplexing;
demodulating the FFT converted signal to produce the first data stream and the second encoded data stream, wherein the second encoded data stream is produced according to the data for demodulation;
first error correction code (ECC) decoding the second encoded data stream to produce the interleaved data stream;
de-interleaving the interleaved data stream to produce the first encoded data stream; and
second error correction code (ECC) decoding the first encoded data stream to produce the second data stream, wherein the first data stream has data for demodulation including the number of signal points of the constellation for the second encoded data stream.
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Specification