Systems and methods for adaptively-tuned digital self-interference cancellation

1. A system for adaptively-tuned digital self-interference cancellation comprising:

a transmit coupler, communicatively coupled to an analog transmit signal of a transmitter of a communications system, that samples the analog transmit signal to create a sampled analog transmit signal;

an analog self-interference canceller that generates an analog self-interference cancellation signal from the sampled analog transmit signal;

a receive coupler, communicatively coupled to an analog receive signal of a receiver of the communications system, that combines the analog self-interference cancellation signal with the analog receive signal, therefore reducing self-interference in the analog receive signal; and

a digital self-interference canceller that generates a digital self-interference cancellation signal from a digital transmit signal of the communications system, the digital self-interference canceller comprising:

a component generation system that generates a first set of self-interference cancellation signal components from the digital transmit signal;

a first multi-rate filter that, according to a transform configuration, combines the first set of self-interference cancellation signal components to generate the digital self-interference cancellation signal; and

a transform adaptor that updates the transform configuration;

wherein the digital self-interference cancellation signal is combined with a digital receive signal to form a digital residue signal; wherein the digital self-interference canceller generates a composite residue signal, non-identical to the digital residue signal, from the digital residue signal and the digital transmit signal; wherein the transform adaptor updates the transform configuration based on the composite residue signal.

2. The system of claim 1 , wherein the transform adaptor updates the transform configuration by computing a self-interference channel from the composite residue signal and updating the transform configuration based on the computed self-interference channel.

3. The system of claim 2 , wherein the transform adaptor converts the composite residue signal to a frequency domain to form a frequency-domain-converted composite residue signal and computes the self-interference channel based on the frequency-domain-converted composite residue signal.

4. The system of claim 3 , wherein the transform adaptor computes the self-interference channel in a time domain based on the frequency-domain-converted composite residue signal to form a time-domain-converted self-interference channel.

5. The system of claim 4 , wherein computing the self-interference channel further comprises computing the self-interference channel based on the frequency-domain composite residue signal.

6. The system of claim 5 , wherein computing the self-interference channel comprises computing the self-interference channel in a time domain based on the frequency-domain composite residue signal to form a time-domain-converted self-interference channel.

7. The system of claim 2 , wherein the digital self-interference canceller generates the composite residue signal by: converting the digital residue signal to a frequency domain to form a frequency-domain-converted digital residue signal; converting the digital transmit signal to the frequency domain to form a frequency-domain-converted digital transmit signal; and generating a frequency-domain composite residue signal from the frequency-domain-converted digital residue signal and the frequency-domain-converted digital transmit signal.

8. The system of claim 1 , wherein the transform adaptor updates the transform configuration by: generating an updated transform configuration in a frequency domain based on the composite residue signal; modifying the updated transform configuration in the frequency domain according to a transform modification configuration; converting the modified updated transform configuration to a time domain; and updating the transform configuration based on the time-domain-converted modified updated transform configuration.

9. The system of claim 8 , wherein the transform adaptor modifies the updated transform configuration by smoothing, in the frequency domain, at least one of a magnitude response of the updated transform configuration and a phase response of the updated transform configuration.

10. The system of claim 9 , wherein the transform adaptor smooths the response by identifying a rapidly varying section of the response and modifying the response in the rapidly varying section.

11. The system of claim 1 , wherein the transform adaptor updates the transform configuration by: generating the updated transform configuration in a frequency domain based on the composite residue signal; modifying the updated transform configuration in the frequency domain according to a transform modification configuration; converting the modified updated transform configuration to a time domain; and updating the transform configuration based on the time-domain-converted modified updated transform configuration.

12. The system of claim 11 , wherein modifying the updated transform configuration in the frequency domain causes a size reduction of the time-domain-converted modified updated transform configuration.

13. The system of claim 11 , wherein the transform adaptor modifies the updated transform configuration by smoothing a magnitude response in the frequency domain of the updated transform configuration.

14. The system of claim 13 , wherein the transform adaptor smooths the magnitude response by identifying a rapidly varying section of the magnitude response based on a derivative of the magnitude response with respect to frequency, and modifying the rapidly varying section to reduce the derivative of the magnitude response.

15. The system of claim 14 , wherein the transform adaptor modifies the rapidly varying section by replacing the rapidly varying section with an exponential decay response fit to the rapidly varying section.

16. The system of claim 14 , wherein the transform adaptor modifies the rapidly varying section by replacing the rapidly varying section with a polynomial response fit to the rapidly varying section.

17. The system of claim 14 , wherein the transform adaptor modifies the rapidly varying section by filtering the rapidly varying section using median filtering or convolution filtering.

18. The system of claim 11 , wherein the transform adaptor modifies the updated transform configuration by smoothing a phase response in the frequency domain of the updated transform configuration.

19. The system of claim 18 , wherein the transform smooths the phase response by identifying a rapidly varying section of the phase response based on a derivative of the phase response with respect to frequency, and modifying the rapidly varying section to reduce the derivative of the phase response.

20. The system of claim 19 , wherein the transform adaptor modifies the rapidly varying section by replacing the rapidly varying section with a linear response fit to the rapidly varying section.

21. The system of claim 19 , wherein the transform adaptor modifies the rapidly varying section by filtering the rapidly varying section using median filtering or convolution filtering.