Self-interference cancellation
A wireless communication device includes, in part, an analog interference cancellation circuit and a controller. The analog cancellation circuit includes a multitude of delay paths each including a delay element and a variable attenuator. The controller dynamically varies the attenuation level of each of the variable attenuators in accordance with the frequency response characteristic of that attenuator to remove a portion of a self-interference signal present in a signal received by the device. The device measures the frequency response characteristic of the communication channel, used in determining the attenuation levels, via one or more preamble symbols. A second portion of the self-interference signal is removed by the device using a multitude of samples of a transmitted signal and a multitude of samples of a signal to be transmitted.
1. A system for full-duplex signal shaping for a full-duplex radio comprising:
An analog self-interference cancellation component, coupled to a transmit line and a receive line of the full-duplex radio, that removes a first portion of self-interference from a receive signal of the full-duplex radio; the analog self-interference cancellation component comprising:
a plurality of signal paths, each signal path including a delay element and a scaling element, wherein each signal path receives a sampled transmit signal and outputs a delayed and weighted transmit signal;
a combiner that combines the delayed and weighted transmit signals of the plurality of signal paths to form a self-interference signal representative; and
a controller that controls parameters of the scaling elements; and
A digital filter engine, coupled to the transmit line and the receive line of the full-duplex radio, that removes a second portion of self-interference from the receive signal.
2. The system of claim 1 , wherein the digital filter engine includes programmable filters, intermediate frequency converters, and a filter engine API; wherein the filter engine API configures the programmable filters and intermediate frequency converters to perform full-duplex signal shaping.
3. The system of claim 2 , wherein one of the programmable filters is a finite response filter.
4. The system of claim 1 , wherein the controller further controls parameters of the delay elements.
5. The system of claim 1 , wherein the scaling elements comprise a variable attenuator and parameters of the scaling elements comprise a variable attenuator attenuation value.
6. The system of claim 5 , wherein the controller controls parameters of the scaling elements based on sinc function intersections with an estimated self-interference signal; wherein the controller adapts the parameters of the scaling elements using an iterative optimization algorithm.
7. The system of claim 6 , wherein the iterative optimization algorithm includes selecting a subset of coefficients based on a coefficient selection algorithm.
8. The system of claim 1 , wherein the controller controls parameters of the scaling elements by determining signal path responses, measuring self-interference, and adapting the parameters of the scaling elements based on the signal path responses and the self-interference.
9. The system of claim 1 , wherein the controller controls parameters of the scaling elements by receiving signal path response data, generating a first self-interference signal estimate, applying a first set of parameter values based on the first self-interference signal estimate, generating a second self-interference signal estimate using the first set of parameter values, and applying a second set of parameter values based on the second self-interference signal estimate.
10. A method for full-duplex signal shaping for a full-duplex radio comprising:
receiving a receive signal of a full-duplex radio;
performing analog self-interference cancellation to remove a first portion of self-interference from the receive signal; wherein performing analog self-interference cancellation comprises receiving a transmit signal of a full-duplex radio; generating a set of delayed versions of the transmit signal; scaling the set of delayed versions of the transmit signal to produce a set of delayed and scaled signals; combining the set of delayed and scaled signals to create a combined signal; and subtracting the combined signal from the receive signal; and
performing digital self-interference removal to remove a second portion of self-interference from the receive signal.
11. The method of claim 10 , wherein the receive signal is received on a plurality of wireless spectrum fragments.
12. The method of claim 10 , further comprising:
after subtracting the combined signal from the receive signal, downconverting the receive signal;
filtering the receive signal; and
converting the receive signal from an analog signal to a digital signal before performing digital self-interference removal.
13. The method of claim 12 , wherein performing digital self-interference removal comprises digital filtering.
14. The method of claim 12 , wherein performing digital self-interference removal comprises cancelling linear digital self-interference and cancelling non-linear digital self-interference.
15. The method of claim 14 , wherein performing digital self-interference removal further comprises correcting gain and phase error.
16. The method of claim 15 , wherein performing digital self-interference removal further comprises cancelling local oscillator leakage.
17. The method of claim 14 , wherein cancelling linear digital self-interference comprises estimating self-interference channel coefficients, wherein estimating self-interference channel coefficients includes selecting a subset of coefficients according to a coefficient selection algorithm.
18. The method of claim 14 , wherein cancelling non-linear digital self-interference comprises estimating non-linear self-interference model coefficients, wherein estimating non-linear self-interference model coefficients includes selecting a subset of coefficients according to a coefficient selection algorithm.
19. The method of claim 10 , further comprising adapting analog self-interference cancellation by determining signal path responses, measuring self-interference, and adapting the parameters of the scaling elements based on the signal path responses and the self-interference.
20. The method of claim 10 , further comprising adapting analog self-interference cancellation by receiving signal path response data, generating a first self-interference signal estimate, applying a first set of parameter values based on the first self-interference signal estimate, generating a second self-interference signal estimate using the first set of parameter values, and applying a second set of parameter values based on the second self-interference signal estimate.