System and method for increasing throughput in digital radio broadcast receiver

1. A method for processing a digital radio broadcast signal, the method comprising:

receiving a digital radio broadcast signal comprising:

a first payload subcarrier group for conveying first content under control of an associated first plurality of reference subcarriers digitally modulated with a first signal constellation, and

a second payload subcarrier group for conveying second content under control of an associated second plurality of reference subcarriers digitally modulated with a second signal constellation; and

processing the digital radio broadcast signal at a first receiver to produce a first coherent reference signal estimate for the first plurality of reference subcarriers to extract the first content from the first payload subcarrier group for playback and to produce a second coherent reference signal estimate for the second plurality of reference subcarriers to disregard the second content.

2. The method of claim 1 , where receiving the digital radio broadcast signal comprises receiving an over-the-air in-band on-channel digital radio broadcast signal.

3. The method of claim 1 , where receiving the digital radio broadcast signal comprises receiving an FM digital audio broadcasting signal comprising a first sideband and a second sideband, where the first sideband comprises the first payload subcarrier group and the associated first plurality of reference subcarriers in the first sideband, and where the second sideband comprises the second payload subcarrier group and the associated second plurality of reference subcarriers.

4. The method of claim 3 , where the first sideband comprises a first partition for transmitting the first content as default digital content to a first receiver, and where the second sideband comprises a second, separate partition for transmitting the second content as enhanced digital content to a second receiver such that the first receiver perceives the second content as noise.

5. The method of claim 4 , where the second signal constellation comprises at least four rotating constellation points which are sequentially applied to modulate the associated second plurality of reference subcarriers.

6. The method of claim 3 , where the first sideband and second sideband are time multiplexed for transmission on a shared partition comprising a plurality of subcarriers.

7. The method of claim 6 , where the second signal constellation comprises a deceptive reference pattern of up to four constellation points which are sequentially applied to modulate the associated second plurality of reference subcarriers before reverting to the first signal constellation.

8. The method of claim 3 , where the first sideband and second sideband are multiplexed for transmission on shared subcarriers by modulating “I” components of shared reference subcarriers with the first signal constellation and simultaneously modulating “Q” components of shared reference subcarriers with the second signal constellation.

9. The method of claim 8 , where the second signal constellation comprises a plurality of alternating constellation points which are sequentially applied to modulate the “Q” components of shared reference subcarriers to cause the first receiver to derive a reference phase that is rotated by 45°.

10. The method of claim 1 , where processing the digital radio broadcast signal to produce the first coherent reference signal estimate comprises:

extracting reference subcarrier symbols transmitted on the first plurality of reference subcarriers;

combining the reference subcarrier symbols with a known reference sequence conjugate corresponding to the first signal constellation to produce a plurality of samples;

median filtering the plurality of samples to produce filtered samples; and

smoothing the filtered samples over the first plurality of reference subcarriers to produce the first coherent reference signal estimate for the first plurality of reference subcarriers to extract the first content from the first payload subcarrier group.

11. The method of claim 1 , where processing the digital radio broadcast signal to produce the second coherent reference signal estimate comprises:

extracting reference subcarrier symbols transmitted on the second plurality of reference subcarriers;

combining the reference subcarrier symbols with a known reference sequence conjugate corresponding to the first signal constellation to produce a plurality of samples;

median filtering the plurality of samples to produce filtered samples; and

smoothing the filtered samples over the second plurality of reference subcarriers to produce the second coherent reference signal estimate for the second plurality of reference subcarriers to disregard the second content from the second payload subcarrier group.

12. The method of claim 11 , further comprising producing erasure information for the second content in response to the second coherent reference signal estimate.

13. The method of claim 1 , further comprising processing the digital radio broadcast signal at a second receiver to produce a third coherent reference signal estimate for the second plurality of reference subcarriers to extract the second content from the second payload subcarrier group for playback at the second receiver.

14. A digital radio broadcast receiver comprising at least one recordable device having stored thereon executable instructions and data which, when executed by at least one processing device, cause the at least one processing device to process a digital radio broadcast signal by:

receiving a digital radio broadcast signal comprising:

a first payload subcarrier group for conveying first content under control of an associated first plurality of reference subcarriers digitally modulated with a first signal constellation, and

a second payload subcarrier group for conveying second content under control of an associated second plurality of reference subcarriers digitally modulated with a second signal constellation; and

processing the digital radio broadcast signal to produce a first coherent reference signal estimate for the first plurality of reference subcarriers to extract the first content from the first payload subcarrier group for playback and to produce a second coherent reference signal estimate for the second plurality of reference subcarriers to disregard the second content.

15. The digital radio broadcast receiver of claim 14 , wherein the executable instructions and data, when executed by at least one processing device, cause the at least one processing device to receive the digital radio broadcast signal by receiving an over-the-air in-band on-channel digital radio broadcast signal.

16. The digital radio broadcast receiver of claim 14 , wherein the executable instructions and data, when executed by at least one processing device, cause the at least one processing device to receive the digital radio broadcast signal by receiving an FM digital audio broadcasting signal comprising a first sideband and a second sideband, where the first sideband comprises the first payload subcarrier group and the associated first plurality of reference subcarriers in the first sideband, and where the second sideband comprises the second payload subcarrier group and the associated second plurality of reference subcarriers.

17. The digital radio broadcast receiver of claim 16 , where the first sideband comprises a first partition for conveying the first content as default digital content, and where the second sideband comprises a second, separate partition for conveying the second content as enhanced digital content such that the digital radio broadcast receiver perceives the second content as noise.

18. The digital radio broadcast receiver of claim 17 , where the second signal constellation comprises at least four rotating constellation points which are sequentially applied to modulate the associated second plurality of reference subcarriers.

19. The digital radio broadcast receiver of claim 16 , where the first sideband and second sideband are time multiplexed for transmission on a shared partition comprising a plurality of subcarriers.

20. The digital radio broadcast receiver of claim 19 , where the second signal constellation comprises a deceptive reference pattern of up to four constellation points which are sequentially applied to modulate the associated second plurality of reference subcarriers before reverting to the first signal constellation.

21. The digital radio broadcast receiver of claim 16 , where the first sideband and second sideband are multiplexed for transmission on shared subcarriers by modulating “I” components of shared payload subcarriers with the first content and simultaneously modulating “Q” components of shared payload subcarriers with the second content.

22. The digital radio broadcast receiver of claim 21 , where the second reference subcarrier signal constellation comprises a plurality of alternating constellation points which are sequentially applied to modulate the second plurality of reference subcarriers to cause the digital radio broadcast receiver to derive a reference phase that is rotated by 45°.

23. The digital radio broadcast receiver of claim 14 , wherein the executable instructions and data, when executed by at least one processing device, cause the at least one processing device to process the digital radio broadcast signal to produce a first coherent reference signal estimate by:

extracting reference subcarrier symbols transmitted on the first plurality of reference subcarriers;

combining the reference subcarrier symbols with a known reference sequence conjugate corresponding to the first signal constellation to produce a plurality of samples;

median filtering the plurality of samples to produce filtered samples; and

smoothing the filtered samples over the first plurality of reference subcarriers to produce the first coherent reference signal estimate for the first plurality of reference subcarriers to extract the first content from the first payload subcarrier group.

24. The digital radio broadcast receiver of claim 14 , wherein the executable instructions and data, when executed by at least one processing device, cause the at least one processing device to process the digital radio broadcast signal to produce a second coherent reference signal estimate by:

extracting reference subcarrier symbols transmitted on the second plurality of reference subcarriers;

combining the reference subcarrier symbols with a known reference sequence conjugate corresponding to the first signal constellation to produce a plurality of samples;

median filtering the plurality of samples to produce filtered samples; and

smoothing the filtered samples over the second plurality of reference subcarriers to produce the second coherent reference signal estimate for the second plurality of reference subcarriers to disregard the second content from the second payload subcarrier group.

25. The digital radio broadcast receiver of claim 24 , wherein the executable instructions and data, when executed by at least one processing device, cause the at least one processing device to produce erasure information for the second content in response to the second coherent reference signal estimate.

26. An article of manufacture comprising a non-transitory computer readable storage device having computer program instructions adapted to cause a processing system to:

control reception of an over-the-air in-band on-channel digital radio broadcast signal comprising:

a first payload subcarrier group for conveying first content under control of an associated first plurality of reference subcarriers digitally modulated with a first signal constellation, and

a second payload subcarrier group for conveying second content under control of an associated second plurality of reference subcarriers digitally modulated with a second signal constellation;

process the over-the-air in-band on-channel digital radio broadcast signal at a first receiver to produce a first coherent reference signal estimate for the first plurality of reference subcarriers to extract the first content from the first payload subcarrier group for playback and to produce a second coherent reference signal estimate for the second plurality of reference subcarriers to disregard the second content; and

produce erasure information for the second content in response to the second coherent reference signal estimate.

27. A digital radio broadcast receiver comprising at least one recordable device having stored thereon executable instructions and data which, when executed by at least one processing device, cause the at least one processing device to process a digital radio broadcast signal by:

receiving a digital radio broadcast signal comprising:

a first payload subcarrier group for conveying first content under control of an associated first plurality of reference subcarriers digitally modulated with a first signal constellation, and

a second payload subcarrier group for conveying second content under control of an associated second plurality of reference subcarriers digitally modulated with a second signal constellation; and

processing the digital radio broadcast signal to produce a first coherent reference signal estimate for the first plurality of reference subcarriers to extract the first content from the first payload subcarrier group for playback and to produce a second coherent reference signal estimate for the second plurality of reference subcarriers to extract the second content from the second payload subcarrier group for playback.

28. A transmitter, comprising:

a modulator for digitally modulating a first plurality of reference subcarriers with a first signal constellation, and for digitally modulating a second plurality of reference subcarriers with a second signal constellation;

processor circuitry for generating the digital radio broadcast signal by combining the first plurality of reference subcarriers with a first data payload subcarrier group for conveying first content under control of the first plurality of reference subcarriers, and by combining the second plurality of reference subcarriers with a second data payload subcarrier group for conveying second content under control of the second plurality of reference subcarriers; and

an amplifier for amplifying the digital radio broadcast signal for broadcast to a first receiver for processing to produce a first coherent reference signal estimate for the first plurality of reference subcarriers to extract the first content from the first data payload subcarrier group for playback and to produce a second coherent reference signal estimate for the second plurality of reference subcarriers to disregard the second content from the second data payload subcarrier group.

29. A digital radio broadcast transmitter comprising at least one recordable device having stored thereon executable instructions and data which, when executed by at least one processing device, cause the at least one processing device to broadcast a digital radio broadcast signal by:

modulating a first plurality of reference subcarriers and a second plurality of reference subcarriers with a first signal constellation and a second signal constellation, respectively;

combining the first plurality of reference subcarriers with a first data payload subcarrier group for conveying first content under control of the first plurality of reference subcarriers;

combining the second plurality of reference subcarriers with a second data payload subcarrier group for conveying second content under control of the second plurality of reference subcarriers; and

processing the digital radio broadcast signal for broadcast to a first receiver for processing to produce a first coherent reference signal estimate for the first plurality of reference subcarriers to extract the first content from the first data payload subcarrier group for playback and to produce a second coherent reference signal estimate for the second plurality of reference subcarriers to disregard the second content from the second data payload subcarrier group.