In-band on-channel digital broadcasting method and system

• US 20010050926A1
• Filed: 06/11/2001
• Published: 12/13/2001
• Est. Priority Date: 06/19/1996
• Status: Active Grant

• Current Assignee: Derek D. Kumar
• Original Assignee: Derek D. Kumar
• Inventors: Kumar, Derek D.
• Granted Patent: US 7,046,694 B2
• Time in Patent Office: Days
• US Class Current: 370/529
• CPC Class Codes: H04H 20/30 by a single channel
• CPC Class Codes: H04H 2201/183 FM digital or hybrid
• CPC Class Codes: H04H 2201/20 digital audio broadcasting [DAB]
• CPC Class Codes: H04H 60/07 characterised by processes or methods for the generation
• CPC Class Codes: H04L 1/0054 Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/02 by diversity reception
• CPC Class Codes: H04L 1/08 by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence

Abstract

A method and system are provided for the transmission and reception of an In-band On-channel (IBOC) FM-band digital audio broadcast (DAB) signal. The IBOC DAB signal is generated in the transmitter to substantially occupy the upper and lower sideband frequency regions in the RF emission mask for the conventional broadcast analog FM-band. Redundant source bit information is transmitted in both the upper and lower sidebands so that the loss of information in either one but not both sidebands due to large amounts of interference or distortion, caused by, for example, first-adjacent interference, does not deleteriously affect the IBOC DAB receiver performance. The system exhibits both frequency-diversity and time-diversity. The receiver determines which codeword bit estimate, corresponding to either upper or lower sideband signals, is less likely to be erroneous. The receiver system selects between decoded estimates for each pair of demodulated ECC codewords or combines both ECC codeword estimates prior to decoding in certain embodiments.

Claims

1. An in-band on-channel (IBOC) digital broadcast receiver comprising:

receiving means for receiving an IBOC digital signal with source bit information which is duplicated by redundant modulation of signals in both upper and lower sidebands of a predetermined radio frequency (RF) mask;

demodulation means for demodulating the received IBOC signals in both the upper and lower sidebands;

determination means for determining whether the demodulated redundant source bit information in the upper sideband or the lower sideband is less likely to be erroneous; and

selection means for selecting the demodulated source bit information determined by said determination means as less likely to be erroneous without requiring prior knowledge as to which sideband is less likely to be deleteriously affected.

2. The IBOC receiver of

claim 1

, wherein said receiving means is further for receiving within said mask an analog FM signal in a central region of said mask about a center frequency, said analog FM signal and at least one of said redundant IBOC signals in said upper and lower sidebands being received simultaneously.

3. The IBOC receiver of

claim 1

, further including processing means for processing the demodulated and selected source bit information and forwarding same to a user.

4. The IBOC receiver of

claim 1

, further comprising means for combining demodulated information generated prior to combined source bit information determination, from both the upper and lower sidebands when said determination means determines that the likelihood of error in the demodulated or recovered source bit information in the upper and lower sidebands is substantially equal.

5. The IBOC receiver of

claim 1

, further comprising upper and lower sideband demodulators and a time diversity delay means, wherein said diversity delay means is located prior to said determination means, said delay means compensating for a corresponding delay in an IBOC transmitter thereby rendering the receiver robust against certain deleterious events which may affect both the upper and lower sideband signals at substantially the same time.

16. The IBOC receiver of

claim 1

, wherein said determination means compares accumulated branch metrics at a codeword terminating state from Viterbi decoding of codeword estimates determined from demodulation of the upper and the lower sideband signals.

17. The IBOC receiver of

claim 1

, wherein said determination means compares a Hamming distance between codeword estimates determined from demodulation of the upper and lower sideband signals and corresponding re-encoded decoded codewords.

22. The IBOC receiver of

claim 1

, including only one antenna, and wherein the upper and lower sideband signals representing the redundant source bit information are one of:

(i) identical modulated upper and lower sideband RF signals; and

(ii) differently modulated upper and lower sideband signals representing substantially the same source bit information.

6. A method of receiving an in-band on-channel (IBOC) digital broadcast radio frequency (RF) signal via a receiver comprising the steps of:

receiving the IBOC digital signal having redundant source bit information in both an upper and a lower sideband relative to a center frequency;

determining, in the receiver, whether the source bit information in the redundantly modulated upper sideband or the lower sideband is less likely to contain source bit errors; and

selecting, in the receiver, the source bit information determined in said determining step to be less likely to contain errors, so that the method of receiving is robust against adjacent channel interference.

7. The method of

claim 6

, wherein said receiving step further includes receiving an analog FM signal located between said upper and lower sidebands together with said redundant IBOC signals in the upper and lower sidebands.

8. The method of

claim 7

, further comprising the step of separating the received analog FM signal from the IBOC digital signals and thereafter separately demodulating said IBOC signals and said analog FM signal;

wherein said upper and lower sidebands include duplicate source bit information as the redundancy; and

wherein the duplicate source bit information transmitted in the upper sideband is received at a different point in time than the corresponding duplicate source bit information transmitted in the lower sideband so that the system is robust against deleterious effects which may affect both sidebands at once.

9. The method of

claim 6

, further comprising the step of time delaying demodulated information prior to source bit determination of at least one of the received IBOC upper and lower sideband signals in the receiver so as to compensate for a corresponding delay in an IBOC digital signal transmitter thereby rendering the receiver robust against certain deleterious effects which may affect both sideband signals at once.

10. The method of

claim 6

, wherein the source bit information in both the upper and lower sidebands is completely redundant and includes ancillary data.

23. The method of

claim 6

, wherein said determining step determines to combine demodulator information from the upper and lower sideband signals when it is determined that the likelihood of error in the demodulated or recovered source bit information from the upper and lower sideband signals is approximately equal, and thereafter combining the demodulator information from the upper and lower sideband signals to recover source bits.

11. An in-band on-channel (IBOC) digital audio broadcast (DAB) communication system including a transmitter and at least one receiver, the IBOC DAB system comprising:

a transmitter including an analog FM signal generator, an upper sideband digital signal generator, and a lower sideband digital signal generator, said transmitter for combining an analog FM signal generated by said FM signal generator together with digital sideband signals from said upper and lower sideband generators into a composite signal to be transmitted wherein said sideband signals each include source bit information;

means for transmitting said composite signal;

an IBOC DAB receiver for receiving said composite signal, said receiver including an FM analog demodulator, an upper sideband digital demodulator, and a lower sideband digital demodulator;

said receiver further including a comparing device for determining which of (i) recovered source bit information from demodulation of the upper sideband IBOC DAB signal, and (ii) recovered source bit information from demodulation of the lower sideband IBOC DAB signal, is less likely to be erroneous; and

said receiver further including a selector for selecting for further processing and forwarding to a user the demodulated or recovered source bit information from sideband signals determined by said comparing device to be less likely to include source bit errors.

12. The system of

claim 11

, wherein said transmitter includes a time delay device for delaying the source bit information in one of the upper and lower sidebands, and said receiver includes a corresponding time delay device for delaying source bit information in the other of the upper and lower sidebands, so that the system is robust against unexpected deleterious effects which may affect the upper and lower sideband signals at once.

13. The system of

claim 11

, wherein said transmitter transmits redundant source bit information in said upper and lower sidebands and wherein the upper and lower sideband signals representing the redundant source bit information may or may not be identical although the information therein is redundant.

14. The system of

claim 11

, wherein each of the upper and lower sideband signals includes a plurality of orthogonal or approximately orthogonal subcarrier signals.

15. The system of

claim 14

, wherein the subcarrier signals in each of the upper and lower sidebands are modulated, in said transmitter, as pairs with m-ary pragmatic trellis coded modulation (PTCM) where each transmitted codeword has a finite-length and is terminated at a predetermined state.

18. The system of

claim 11

, wherein said comparing device further decides whether to (i) select recovered source bit information from demodulation of one of the upper and lower sideband signals or to (ii) combine information determined from demodulation of the upper and lower sideband signals and recover source bit information from the combined information.

19. A method of receiving a digitally modulated signal comprising the steps of:

receiving the digitally modulated signal which has source bit information duplicated in redundant modulation of signals in both an upper and lower sideband relative to a predetermined center frequency;

demodulating the received signals from both the upper and lower sidebands;

determining which of demodulated recovered source bit information from demodulation of one of the upper and lower sideband signals is less likely to be erroneous; and

selecting the sideband information from one of the demodulated upper or lower sideband signals, whichever was determined in said determining step as less likely to have errors in the demodulated or recovered source bit information.

20. The method of

claim 19

wherein said receiving step further includes receiving the redundantly modulated upper sideband signals at a different time than the corresponding modulated lower sideband signals whereby the method is robust against certain deleterious effects which may affect both sideband signals at once.

21. A method of transmitting an IBOC DAB radio frequency (RF) signal in an IBOC DAB RF communication system which is robust to certain deleterious effects, the method comprising the steps of:

providing a source message which is to be transmitted to a corresponding receiver;

using the source message to generate codewords which are used to redundantly data-modulate a set of subcarrier signals in an upper sideband and a lower sideband of a predetermined RF mask over a plurality of baud intervals so that the resulting sideband signals include redundant source bit information thus providing frequency diversity;

time-delaying the codewords for one of the modulated upper and lower sideband signals relative to the corresponding codewords for the modulation of the other sideband in order to create time diversity in the upper and lower sidebands;

generating an analog FM-band signal to be transmitted; and

transmitting, via an antenna, the analog FM-band signal and said redundant sideband signals to an IBOC DAB receiver.