Multi-subcarrier modulation for HDTV transmission

• US 5,243,629 A
• Filed: 09/03/1991
• Issued: 09/07/1993
• Est. Priority Date: 09/03/1991
• Status: Expired due to Term

• Current Assignee: American Telephone & Telegraph Company (AT&T, Inc.)
• Original Assignee: AT&T, Inc.
• Inventors: Wei, Lee-Fang
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): VO, DON NGUYEN
• Application Number:
  US07/753,491
• Time in Patent Office: 735 Days
• Field of Search: 375/27, 375/38, 375/40, 375/100, 375/102, 375/58, 375/59, 370/69.1, 370/71, 370/73, 371/43, 371/37.1, 455/8
• US Class Current: 375/299
• CPC Class Codes: H04L 27/2604 Multiresolution systems by means of multiresolution subcarriers H04L27/183, H04L27/3488
• CPC Class Codes: H04N 21/2383 Channel coding or modulation of digital bit-stream, e.g. QPSK modulation arrangements for detecting or preventing errors in the information received by adapting the channel coding H04L1/0009; analogue front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 21/4382 Demodulation or channel decoding, e.g. QPSK demodulation analog front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 7/015 High-definition television systems
• CPC Class Codes: H04N 7/0806 the signals being two or more video signals H04N7/0803, H04N7/081 take precedence

Abstract

A high definition television (HDTV) signal is transmitted by a multi-subcarrier transmission scheme in which each subcarrier is used to carry a different class of HDTV information.

Claims

1. A method for processing an information signal comprising the steps of

separating the information signal into a plurality of classes of information such that at least one of the plurality of classes of information is more important for reception of the information signal than the other ones of the plurality of classes of information,

encoding the plurality of classes of information to provide a plurality of encoded symbols such that the more important information has more error protection than the remaining ones of the plurality of classes of information, and

modulating the plurality of encoded symbols into a plurality of subchannels within a frequency band, each subchannel occupying a different frequency spectrum.

2. The method of claim 1 wherein the frequency band is assigned to a different signal.

3. The method of claim 2 wherein the modulating step place the more important information into a subchannel that does not contain a carrier of the different signal.

4. The method of claim 1 wherein the encoding step includes the steps of

channel encoding each one of the plurality of classes of information to provide a plurality of encoded outputs, and

mapping each one of the plurality of encoded outputs to signal constellation to provide the plurality of encoded symbols.

5. The method of claim 4 wherein the channel encoding step for the more important information is different from the channel encoding step of at least one other of the plurality of classes of information.

6. The method of claim 5 wherein the channel encoding step operates in accordance with an error correcting code.

7. The method of claim 5 wherein the channel encoding step operates in accordance with coded modulation.

8. The method of claim 5 wherein the channel encoding step operates in accordance with coded modulation and an error correcting code.

9. The method of claim 4 wherein the mapping step for the more important information uses a signal point constellation that is different from at least one other of the signal point constellations used for the other plurality of classes of information.

10. The method of claim 1 wherein the encoding step uses a symbol rate for the more important class of information that is different from the symbol rate of a least one other class of information.

11. A method for transmitting a first signal in a frequency band allocated to a second signal comprising the step of

dividing the frequency band into a number of subchannels,

separating the first signal into a plurality of classes of information such that at least one of the plurality of classes of information in more important for reception of the information signal than the other ones of the plurality of classes of information, and

assigning the more important information to a subchannel that is different from those subchannels that are subject to substantial interference from the second signal.

12. The method of claim 11 wherein the assigning step includes the steps of

encoding each one of plurality of classes of information, and

frequency modulating the encoded plurality of classes of information to the respective subchannel.

13. The method of claim 11 wherein the first signal is a High Definition Television signal, the second signal is a National Television System Committee signal, and the more important information is assigned to a subchannel that is different from those subchannels that are subject to substantial interference from the visual, chroma or aural carriers of the National Television System Committee signal.

14. A method for transmitting a first signal in a frequency band allocated to a second signal comprising the steps of

dividing the frequency band into a number of subchannels,

separating the first signal into a plurality of classes of information such that at least one of the plurality of classes of information is more important than the other ones of the plurality of classes of information for reception of the information signal, and

assigning the more important information to a subchannel that does not contain a carrier of the second signal.

15. The method of claim 14 wherein the first signal is a High Definition Television signal, the second signal is a National Television System Committee signal, and the more important information is assigned to a subchannel that is different from those subchannels that contain the visual, chroma or aural carriers of the signal.

16. A method for processing a signal, the signal being comprised of a plurality of subchannels, each subchannel carrying a class of information, with one subchannel carrying the more important information, said plurality of subchannels occupying a frequency band that is assigned to a different signal, with the subchannel that is carrying the more important information being different from those subchannels that are subject to substantial interference from the different signal, the method comprising the steps of

receiving the signal,

filtering the received signal to provide the plurality of subchannels,

demodulating each one of the received plurality of subchannels to provide a plurality of received encoded symbols,

decoding each one of the plurality of received encoded symbols to provide the plurality of classes of information, and

combining each one of the plurality of classes of information in a predetermined manner, which takes into account which subchannel carried the more important information, to recreate the information signal.

17. Apparatus for processing an information signal comprising

means for separating the information signal into a plurality of classes of information such that at least one of the plurality of classes of information is more important than the other ones of the plurality of classes of information for reception of the information signal,

means for providing unequal levels of error protection to the plurality of classes of information to provide a plurality of encoded symbols for each one of the plurality of classes of information such that the more important information has more error protection than the remaining ones of the plurality of classes of information, and

means for modulating the plurality of encoded symbols for each one of the plurality of classes of information to a plurality of subchannels within a frequency band, each subchannel occupying a different frequency spectrum.

18. The apparatus of claim 17 wherein the frequency band is assigned to a different signal.

19. The apparatus of claim 18 wherein the means for modulating places the more important information into a subchannel that does not contain a carrier of the different signal.

20. The apparatus of claim 17 wherein the means for providing unequal error protection further comprises

channel encoding means for each one of the plurality of classes of information to provide a plurality of encoded outputs, and

means for mapping each one of the plurality of encoded outputs to a signal constellation to provide the plurality of encoded symbols.

21. The apparatus of claim 20 wherein the channel encoding means for the more important information is different from the channel encoding means of at least one other of the plurality of classes of information.

22. The apparatus of claim 20 wherein the means for mapping the more important information uses a signal point constellation that is different from at least one other of the signal point constellations used for the other plurality of classes of information.

23. The apparatus of claim 17 wherein the means for providing unequal error protection uses a symbol rate for the more important class of information that is different from the symbol rate of at least one other class of information.

24. Apparatus for processing a signal, the signal being comprised of a plurality of subchannels, each subchannel carrying a class of information, with one subchannel carrying the more important information, said plurality of subchannels occupying a frequency band that is assigned to a different signal, with the subchannel that is carrying the more important information being different from those subchannels that are subject to substantial interference from the different signal, the apparatus comprising

means for receiving the signal,

means for filtering the received signal to provide the plurality of subchannels,

means for demodulating each one of the received plurality of subchannels to provide a plurality of received encoded symbols,

means for decoding each one of the plurality of received encoded symbols to provide the plurality of classes of information, and

means for combining each one of the plurality of classes of information in a predetermined manner, which takes into account which subchannel carried the more important information, to recreate the information signal.