Systems and methods for non-linear digital self-interference cancellation

1. A system for non-linear digital self-interference cancellation comprising:

a pre-processor communicatively coupled to a digital transmit signal of a full-duplex wireless communication system that generates a first pre-processed digital transmit signal from the digital transmit signal;

a non-linear transformer that transforms the first pre-processed digital transmit signal into a non-linear self-interference signal according to a transform configuration; wherein the non-linear transformer comprises a first transform path and a second transform path;

wherein the first transform path comprises a model component that generates a first order non-linear self-interference signal component from the first pre-processed digital transmit signal;

wherein the second transform path comprises an upsampler that upsamples the first pre-processed digital transmit signal by a factor of three to create an upsampled signal, a model component that generates a third order non-linear self-interference signal component from the upsampled signal, a low-pass filter that removes undesired high frequency components from the third order non-linear self-interference signal component, and a downsampler that downsamples the third order nonlinear self-interference signal component by a factor of three;

a transform adaptor that sets the transform configuration of the non-linear transformer; and

a post-processor that combines the non-linear self-interference signal with a digital receive signal of the full-duplex wireless communication system.

2. The system of claim 1 , wherein the nonlinear transformer creates the non-linear self-interference signal from a weighted sum of the first order and third-order non-linear self-interference signal components.

3. The system of claim 1 , further comprising a linear transformer that transforms a second preprocessed digital transmit signal into a linear self-interference signal according to a transform configuration.

4. The system of claim 3 , wherein the first pre-processed and second pre-processed digital transmit signals are substantially identical.

5. The system of claim 3 , wherein the pre-processor splits the digital transmit signal into non-linear components and linear components, wherein the first pre-processed digital transmit signal is primarily composed of the non-linear components and the second pre-processed digital transmit signal is primarily composed of the linear components.

6. The system of claim 1 , wherein the nonlinear transformer uses a generalized memory polynomial model.

7. The system of claim 6 , wherein the transform configuration comprises generalized memory polynomial coefficients and the generalized memory polynomial coefficients are adapted by the transform adaptor according to a gradient-descent optimization algorithm.

8. The system of claim 1 , further comprising a digital pre-distortion circuit that performs digital pre-distortion on the digital transmit signal and passes a pre-distorted digital transmit signal to a transmitter of the full-duplex wireless communication system, and an analog signal sampler that provides RF transmit signal samples to the system, wherein the RF transmit signal samples are used to adjust the digital pre-distortion circuit.

9. A method for non-linear digital self-interference cancellation comprising:

receiving a digital transmit signal of a full-duplex wireless communication system;

transforming the digital transmit signal into a non-linear self-interference signal according to a transform configuration; wherein transforming the digital transmit signal comprises generating a first non-linear self-interference signal component and a second non-linear self-interference signal component, and combining the first and second non-linear self-interference signal components to create the non-linear self-interference signal; wherein generating the first non-linear self-interference signal component comprises processing the digital transmit signal with a first-order model component and generating the second non-linear self-interference signal component comprises upsampling the digital transmit signal by a factor of three, processing the digital transmit signal with a third-order model component, filtering the digital transmit signal, and downsampling the digital transmit signal by a factor of three; and

combining the non-linear self-interference signal with a digital receive signal of the full-duplex wireless communication system.

10. The method of claim 9 further comprising adapting the transform configuration dynamically based on the non-linear self-interference signal and the digital receive signal.

11. The method of claim 10 , wherein adapting the transform configuration comprises adapting the transform configuration according to a gradient descent algorithm.

12. The method of claim 9 , further comprising pre-processing the digital transmit signal into a linear digital transmit signal and a non-linear digital transmit signal, further comprising transforming the linear digital transmit signal into a linear self-interference signal, wherein transforming the digital transmit signal into a non-linear self-interference signal comprises transforming the non-linear digital transmit signal into a non-linear self-interference signal.

13. The method of claim 9 , further comprising digitally pre-distorting the digital transmit signal using a digital pre-distortion circuit.

14. The method of claim 13 , wherein the digital pre-distortion circuit is adapted according to samples of an RF transmit signal of the full-duplex wireless communication system.