Forward error correction coding for AM 9kHz and 10kHz in-band on-channel digital audio broadcasting systems
View Patent ↗A method of broadcasting an AM compatible digital audio broadcasting signal includes: producing an analog modulated carrier signal centrally positioned in a radio channel, wherein the analog modulated carrier signal is modulated by an analog signal, producing a plurality of digitally modulated subcarrier signals in the radio channel, wherein the digitally modulated subcarrier signals are modulated using complementary pattern-mapped trellis code modulation (CPTCM) including a code mapped to overlapping partitions including an upper main partition, a lower main partition, an upper backup partition and a lower backup partition, and a non-overlapping tertiary partition, and transmitting the analog modulated carrier signal and the plurality of digitally modulated subcarrier signals. Transmitters that broadcast the signal and receivers that receive the signal, and the reception method are also included.
1. A method of receiving an AM compatible digital audio broadcasting signal, the method comprising:
using an antenna to receive an analog modulated carrier signal centrally positioned in a radio channel, and a plurality of digitally modulated subcarrier signals in the radio channel, wherein the digitally modulated subcarrier signals are modulated using complementary pattern-mapped trellis code modulation (CPTCM) including a code mapped to overlapping partitions including an upper main partition, a lower main partition, an upper backup partition and a lower backup partition, and a non-overlapping tertiary partition; and
using a demodulator to demodulate the analog modulated carrier signal and the plurality of digitally modulated subcarrier signals; and
using an output device to produce an output signal in response to the demodulating step.
2. The method of claim 1 , wherein the code forms a single stream audio signal.
3. The method of claim 2 , wherein the subcarrier signals in the upper backup partition and the lower backup partition are modulated using 16-QAM.
4. The method of claim 1 , wherein the subcarriers include upper main subcarriers, lower main subcarriers, upper backup subcarriers, lower backup subcarriers, and tertiary subcarriers, with the power spectral density of each of the upper main subcarriers, lower main subcarriers, upper backup subcarriers, lower backup subcarriers, being at least 40 dBc below the power spectral density of an analog modulated carrier in the same channel as the subcarriers, and the power spectral density of each of the tertiary subcarriers, being at least 50 dBc below the power spectral density of the analog modulated carrier.
5. The method of claim 4 , wherein the subcarriers further include timing subcarriers and integrated digital service subcarriers; and
each of the subcarriers is located at one of a plurality of evenly spaced frequency locations, with the timing subcarriers being at locations + 1 and − 1 , the upper tertiary subcarriers being at locations + 2 through + 26 , the lower tertiary subcarriers being at locations − 2 through − 26 , the upper main subcarriers being at locations + 28 through + 52 , the lower main subcarriers being at locations − 28 through − 52 , the upper backup subcarriers being at locations + 54 through + 78 , the lower backup subcarriers being at locations − 54 through − 78 , and the integrated digital service subcarriers being at locations + 27 , + 53 , − 27 and − 53 .
6. The method of claim 4 , wherein the subcarriers further include timing subcarriers and integrated digital service subcarriers; and
each of the subcarriers is located at one of a plurality of evenly spaced frequency locations, with the timing subcarriers being at locations + 1 and − 1 , the upper tertiary subcarriers being at locations + 2 through + 26 , the lower tertiary subcarriers being at locations − 2 through − 26 , the upper main subcarriers being at locations + 28 through + 52 , the lower main subcarriers being at locations − 28 through − 52 , the upper backup subcarriers being at locations + 54 through + 73 , the lower backup subcarriers being at locations − 54 through − 73 , and the integrated digital service subcarriers being at locations + 27 , + 53 , − 27 and − 53 .
7. The method of claim 4 , wherein the subcarriers further include timing subcarriers and integrated digital service subcarriers; and
each of the subcarriers is located at one of a plurality of evenly spaced frequency locations, with the timing subcarriers being at locations + 1 and − 1 , the upper tertiary subcarriers being at locations + 2 through + 26 , the lower tertiary subcarriers being at locations − 2 through − 26 , the upper main subcarriers being at locations + 28 through + 52 , the lower main subcarriers being at locations − 28 through − 52 , the upper backup subcarriers being at locations + 57 through + 81 , the lower backup subcarriers being at locations − 57 through − 81 , and the integrated digital service subcarriers being at locations + 27 , + 53 , − 27 and − 53 .
8. A receiver receiving an AM compatible digital audio broadcasting signal, the receiver comprising:
an input for receiving an analog modulated carrier signal centrally positioned in a radio channel, and a plurality of digitally modulated subcarrier signals in the radio channel, wherein the digitally modulated subcarrier signals are modulated using complementary pattern-mapped trellis code modulation (CPTCM) including a code mapped to overlapping partitions including an upper main partition, a lower main partition, an upper backup partition and a lower backup partition, and a non-overlapping tertiary partition;
a demodulator for demodulating the plurality of subcarriers with the partitioned bits; and
an output for producing an output signal in response to the demodulator.
9. The receiver of claim 8 , wherein the code forms a single stream audio signal.
10. The receiver of claim 9 , wherein the subcarrier signals in the upper backup partition and the lower backup partition are modulated using 16-QAM.
11. The receiver of claim 8 , wherein the subcarriers include upper main subcarriers, lower main subcarriers, upper backup subcarriers, lower backup subcarriers, and tertiary subcarriers, with the power spectral density of each of the upper main subcarriers, lower main subcarriers, upper backup subcarriers, lower backup subcarriers, being at least 40 dBc below the power spectral density of an analog modulated carrier in the same channel as the subcarriers, and the power spectral density of each of the tertiary subcarriers, being at least 50 dBc below the power spectral density of the analog modulated carrier.
12. The receiver of claim 11 , wherein the subcarriers further include timing subcarriers and integrated digital service subcarriers; and
each of the subcarriers is located at one of a plurality of evenly spaced frequency locations, with the timing subcarriers being at locations + 1 and − 1 , the upper tertiary subcarriers being at locations + 2 through + 26 , the lower tertiary subcarriers being at locations − 2 through − 26 , the upper main subcarriers being at locations + 28 through + 52 , the lower main subcarriers being at locations − 28 through − 52 , the upper backup subcarriers being at locations + 54 through + 78 , the lower backup subcarriers being at locations − 54 through − 78 , and the integrated digital service subcarriers being at locations + 27 , + 53 , − 27 and − 53 .
13. The receiver of claim 11 , wherein the subcarriers further include timing subcarriers and integrated digital service subcarriers; and
each of the subcarriers is located at one of a plurality of evenly spaced frequency locations, with the timing subcarriers being at locations + 1 and − 1 , the upper tertiary subcarriers being at locations + 2 through + 26 , the lower tertiary subcarriers being at locations − 2 through − 26 , the upper main subcarriers being at locations + 28 through + 52 , the lower main subcarriers being at locations − 28 through − 52 , the upper backup subcarriers being at locations + 54 through + 73 , the lower backup subcarriers being at locations − 54 through − 73 , and the integrated digital service subcarriers being at locations + 27 , + 53 , − 27 and − 53 .
14. The receiver of claim 11 , wherein the subcarriers further include timing subcarriers and integrated digital service subcarriers; and
each of the subcarriers is located at one of a plurality of evenly spaced frequency locations, with the timing subcarriers being at locations + 1 and − 1 , the upper tertiary subcarriers being at locations + 2 through + 26 , the lower tertiary subcarriers being at locations − 2 through − 26 , the upper main subcarriers being at locations + 28 through + 52 , the lower main subcarriers being at locations − 28 through − 52 , the upper backup subcarriers being at locations + 57 through + 81 , the lower backup subcarriers being at locations − 57 through − 81 , and the integrated digital service subcarriers being at locations + 27 , + 53 , − 27 and − 53 .