Self-interference cancellation

• US 10,284,356 B2
• Filed: 08/11/2014
• Issued: 05/07/2019
• Est. Priority Date: 02/03/2011
• Status: Active Grant

• Current Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Inventors: Bharadia, Dinesh, Katti, Sachin, McMilin, Emily, Jain, Mayank, Choi, Jung Il, Srinivasan, Kannan
• Primary Examiner(s): Rinehart, Mark H
• Assistant Examiner(s): Detse, Kokou R
• Application Number:
  US14/456,807
• Publication Number:
  US 20140348018A1
• Time in Patent Office: 1,730 Days
• Field of Search: 370252, 370278
• CPC Class Codes: H04B 1/126 having multiple inputs, e.g. auxiliary antenna for receiving interfering signal aerials in general H01Q
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver
• CPC Class Codes: H04B 1/56 with provision for simultaneous communication in two directions
• CPC Class Codes: H04L 5/1423 for simultaneous baseband signals
• CPC Class Codes: H04L 5/1461 Suppression of signals in the return path, i.e. bidirectional control circuits

Abstract

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.

Claims

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.