Television transmission system using spread spectrum and orthogonal frequency-division multiplex

An apparatus for encoding an input signal for transmission, said input signal comprising a first stream of words, each word of which is N samples wide, N being a positive number, said apparatus comprising:

• a first stage receiving the first stream of words and generating a first output sample stream therefrom;
• and
• a second stage receiving said first output sample stream and generating a frequency division multiplex (FDM) output signal therefrom,
• wherein for each word of said first word stream said first stage generates N serial samples of said first output sample stream, each of said N serial samples being formed by a different combination of a set of more than one of the N samples of said each word, and
• wherein said FDM output signal is equivalent to the sum of P subcarriers of different frequencies, each multiplied by a different sample of said first output sample stream, and wherein P is an integer.

An apparatus for decoding a received frequency division multiplex (FDM) signal to extract data or information from which said FDM signal is derived, said apparatus comprising:

• a first stage receiving and decoding said received FDM signal to generate a stream of decoded samples;
• and
• a second stage receiving the stream of decoded samples and generating a first output signal therefrom, said first output signal representing a portion of the data or information from which the FDM signal was derived,
• said first stage comprising an FDM decoder that generates a plurality of demultiplexed signal streams from said received FDM signal, each stream of said plurality of demultiplexed signal streams equivalent to the received FDM signal multiplied by a different one of a plurality of subcarriers and integrated over time and wherein said stream of decoded samples is derived from said plurality of demultiplexed signal streams;
• and
• said second stage comprising a spread spectrum demodulator that multiplies a first intermediate sample stream by each of M pseudorandom sequences and integrates over time to produce M second sample streams therefrom, wherein said first intermediate sample stream is derived from said stream of decoded samples and said first output signal is derived from the M second sample streams, M being a positive number.

A television transmission system for encoding a television production signal for transmission, the television production signal comprising a first input signal and a second input signal, said second input signal representing data that requires a higher quality transmission than data associated with said first input stream, said television system comprising:

• a first stage, a second stage, and a transmitter,
• said first stage comprising a first converter generating a first plurality of signal components from said first input signal, a spread spectrum modulator producing a plurality of spread spectrum signals from said plurality of signal components, and a combiner combining said plurality of spread spectrum signals to produce a first output signal stream;
• said second stage comprising an input stage combining said first output signal stream with said second input signal to produce an intermediate input signal, a second converter generating a second plurality of signal components from said intermediate input signal, a frequency division multiplex (FDM) modulator that produces an FDM output signal from said second plurality of signal components, said FDM output signal being equivalent to the sum of a plurality of subcarriers of different frequencies, each multiplied by one of the signal components of said second plurality of signal components,
• said transmitter stage receiving the FDM output signal and generating a television transmission signal therefrom.

A method of decoding a received television signal that is made available in the form of a complex symbol stream in which a first class of data and a second class of data are encoded, said method comprising:

• determining an amplitude of the complex signal stream, said amplitude representing the first class of data;
• and
• extracting phase information from said complex symbol stream, wherein said phase information represents said second class of data,
• wherein said second class data requires a higher-quality transmission than said first class data.

An apparatus for encoding an input signal for transmission, said input signal comprising a first stream of words, each word of which is N samples wide, N being a positive number, said apparatus comprising:

• a first stage receiving the first stream of words and generating a first output sample stream therefrom;
• and
• a second stage receiving said first output sample stream and generating a frequency division multiplex (FDM) output signal therefrom,
• wherein for each word of said first stream of words said first stage generates N serial samples of said first output sample stream, each of said N serial samples being formed by a different combination of a set of more than one of the N samples of said each word, and
• wherein said second stage comprises a Discrete Fourier Transform (DFT) module and a parallel-to-serial converter, wherein said DFT module produces a parallel output stream by generating the discrete Fourier transform of a second word stream that is derived from said first output sample stream and wherein said parallel-to-serial converter generates said FDM output signal from the parallel output stream of said DFT module.

An apparatus for decoding a received frequency division multiplex (FDM) signal to extract a version of a television production signal from which said FDM signal was derived, said apparatus comprising:

• a first stage receiving and decoding said received FDM signal to generate a stream of decoded samples;
• and
• a second stage receiving the stream of decoded samples and generating a first output signal therefrom, said first output signal representing a first part of the extracted version of the television production signal from which the FDM signal was derived,
• said first stage comprising an FDM decoder that generates a plurality of demultiplexed signal streams from said received FDM signal, each stream of said plurality of demultiplexed signal streams equivalent to the received FDM signal multiplied by a different one of a plurality of subcarriers and integrated over time and wherein said stream of decoded samples is derived from said plurality of demultiplexed signal streams;
• and
• said second stage comprising:
• an input stage that receives said stream of decoded samples and extracts a first intermediate sample stream and a second output signal therefrom, said second output signal representing a second part of the extracted version of the television production signal from which the FDM signal was derived;
• a spread spectrum demodulator that multiplies said first intermediate sample stream by each of M pseudorandom sequences and integrates over time to produce M second sample streams therefrom, wherein said first output signal is derived from the M second sample streams, M being a positive number,
• wherein said second part of extracted version of the television production signal required a higher-quality transmission than said first part.