SYSTEMS AND METHODS FOR MITIGATION OF SELF-INTERFERENCE IN SPECTRALLY EFFICIENT FULL DUPLEX COMMINUCATIONS

• US 20160285486A1
• Filed: 03/23/2015
• Published: 09/29/2016
• Est. Priority Date: 03/23/2015
• Status: Active Grant

• Current Assignee: Hong Kong Applied Science And Technology Research Institute Co., Ltd.
• Original Assignee: Hong Kong Applied Science And Technology Research Institute Co., Ltd.
• Inventors: Qin, Wen, Du, Yuanyuan, Mak, Angus Chi Keung, Ding, Jiewei, Kwan, Man Wai, Tsang, Kong Chau
• Granted Patent: US 9,698,836 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04B 1/123 using adaptive balancing or compensation means adaptive filter circuits and algorithms H03H
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver
• CPC Class Codes: H04B 17/345 Interference values signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR] H04B17/336
• CPC Class Codes: H04B 2001/0408 with power amplifiers
• CPC Class Codes: H04L 5/14 Two-way operation using the same type of signal, i.e. duplex

Abstract

Systems and methods which provide mitigation of self-interference in spectrally efficient full duplex (e.g., transmit and receive using the same frequency simultaneously) communications are described. Embodiments provide an interference mitigation structure having a multi-tap vector modulator interference cancellation circuit operable to cancel time varying multipath interference in the analog RF domain. A multi-tap vector modulator interference cancellation circuit of embodiments may comprise part of a multi-stage interference cancellation circuit, such as a multi-stage interference cancellation circuit comprising a multi-tap vector modulator interference cancellation circuit and a digital residual interference cancellation circuit. A digital residual interference cancellation circuit of embodiments provides residual interference cancellation. A multi-stage interference cancellation circuit configuration of embodiments is operable to provide cancellation of strong multipath signals as well as cancellation of residual multipath signals, including interference in the received signal associated with circulator leakage, antenna reflection and multipath.

Claims

1. A multi-stage self-interference cancellation system, the system comprising:

a transmit signal sampling module coupled to a transmit signal path of a communication station and operable to sample a transmit signal after modification of the transmit signal by a nonlinear component of the transmit signal path, wherein the communication station is operable to transmit and receive using a same frequency simultaneously;

a receive signal sampling module coupled to a receive signal path of the communication station and operable to sample a radio frequency (RF) receive signal as received by the communication station including self-interference from the simultaneous transmitting and receiving using the same frequency;

a channel estimation module coupled to the transmit signal sampling module and the receive signal sampling module and operable to receive sampled signals therefrom, the channel estimation module having circuitry providing RF channel parameters based upon a transmit sample signal from the transmit signal sampling module and a receive sample signal from the receive signal sampling module;

an analog cancellation module coupled to the receive signal path and operable to provide an RF cancellation signal thereto, wherein combining the RF receive signal and the RF cancellation signal provides cancellation of strong self-interference resulting in a residual signal; and

a digital cancellation module coupled to the receive signal path and operable to provide a residual cancellation signal thereto, wherein combining the residual signal and the residual cancellation signal provides a desired receive signal having the self-interference mitigated.

2. The system of claim 1, wherein the nonlinear component of the transmit signal path comprises a power amplifier.

3. The system of claim 1, wherein the channel estimation module comprises:

a baseband channel estimation module; and

a RF channel conversion module, wherein the RF channel conversion module provides the RF channel parameters using a channel estimation provided by the baseband channel estimation module.

4. The system of claim 3, wherein the baseband channel estimation module comprises a channel estimation algorithm module adapted to calculate a RF channel response and a output block adapted to output the RF channel response as multipath in-phase and quadrature coefficients, and wherein the RF channel conversion module comprises a digital to analog converter (DAC) adapted to convert the multipath in-phase and quadrature coefficients to an analog signal and a filter adapted to smooth in-phase and quadrature coefficient changes in the analog signal.

5. The system of claim 4, wherein the channel estimation algorithm module is operable to calculate a correlation between the sampled signals from the transmit signal sampling module and the receive signal sampling module, to interpolate the results of the correlation using a sinc function, and to calculate a plurality of delay relationships.

6. The system of claim 3, wherein the transmit signal sampling module comprises:

a coupler coupled to an output of the nonlinear component and operable to obtain a sample of the transmit signal;

a down-converter operable to down convert the sample of the transmit signal;

a filter operable to reject an unwanted portion of the transmit signal prior to analog to digital conversion thereof; and

an analog to digital converter (ADC) operable to provide a digital representation of at least a portion of the sampled transmit signal to the channel estimation module.

7. The system of claim 6, wherein the receive signal sampling module comprises:

a coupler coupled to an output of a receive front-end of the communication station and operable to obtain a sample of the receive signal;

a down-converter operable to down convert the sample of the receive signal;

a filter operable to reject an unwanted portion of the receive signal prior to analog to digital conversion thereof; and

an ADC operable to provide a digital representation of at least a portion of the sampled receive signal to the channel estimation module.

8. The system of claim 1, wherein the analog cancellation module comprises:

a multi-tap vector modulation module adaptively operable in response to RF channel parameters provided by the channel estimation module.

9. The system of claim 8, further comprising:

a splitter coupled to the transmit signal path and operable to split a sample of the transmit signal into a plurality of transmit signal instances;

a plurality of delay paths coupled to the splitter and operable to provide different delays with respect to the plurality of transmit signal instances, wherein the multi-tap vector modulation module comprises a plurality of vector modulators coupled to the plurality of delay paths and operable to modulate the delayed transmit signal instances based upon the RF channel parameters;

a combiner coupled to the plurality of vector modulators and operable to combine the modulated transmit signal instances provided thereby into a modulated cancellation signal;

a low noise amplifier coupled to the combiner and operable to provide amplification of the modulated cancellation signal; and

a coupler coupled to the receive signal path and operable to provide the modulated cancellation signal to the receive path for combining with the receive signal.

10. The system of claim 1, wherein the digital cancellation module comprises:

a residual channel estimation module coupled to the transmit signal sampling module and a portion of the receive signal path carrying the residual signal and operable to receive sampled signals therefrom, the residual channel estimation module having circuitry providing residual channel estimation parameters based upon the transmit sample signal from the transmit signal sampling module and the residual signal; and

a cancellation signal generator module coupled to the residual channel estimation module, wherein the cancellation signal generator module provides the residual cancellation signal using residual channel estimation parameters.

11. The system of claim 10, wherein the cancellation signal generator module comprises a finite impulse response (FIR) module.

12. The system of claim 10, wherein the residual channel estimation module is adapted to provide the residual channel estimation parameters based upon at least one of a correlation channel estimation based on a known transmit signal, a correlation channel estimation based on a known training sequence, a frequency domain channel estimation based on a pilot, or an adaptive filter based on least means squared (LMS) or recursive least squares (RLS).

13. The system of claim 1, further comprising:

a digital pre-distortion (DPD) module disposed in the transmit signal path and coupled to the receive signal sampling module and operable to receive sampled signals therefrom, wherein the DPD module pre-distorts the transmit signal in the transmit signal path using the sampled signals.

14. A multi-stage self-interference cancellation method, the method comprising:

sampling a transmit signal in a transmit signal path of a communication station after modification of the transmit signal by a nonlinear component of the communication station, wherein the communication station is operable to transmit and receive using a same frequency simultaneously;

sampling a radio frequency (RF) receive signal in a receive signal path of the communication station, wherein the RF receive signal sampled includes self-interference from the simultaneous transmitting and receiving using the same frequency;

determining a channel estimation using the sampled transmit signal and the sampled RF receive signal;

providing RF channel parameters based upon the determined channel estimation;

generating an analog RF cancellation signal using multi-tap vector modulation, wherein the multi-tap vector modulation is adaptively controlled for time varying channel response using the RF channel parameters;

combining the RF receive signal and the RF cancellation signal to provide cancellation of strong self-interference resulting in a residual signal;

determining a residual channel estimate using the sampled transmit signal and a sample of the residual signal;

generating a digital residual cancellation signal using the residual channel estimate; and

combining the residual signal and the residual cancellation signal to provide a desired receive signal having the self-interference mitigated.

15. The method of claim 14, wherein the nonlinear component of the transmit signal path comprises a power amplifier.

16. The method of claim 14, wherein the determining a channel estimation comprises:

calculating a correlation between the sampled transmit signal and the sampled RF receive signal;

interpolating the results of the correlation using a sinc function; and

calculating a plurality of delay relationships for the adaptively controlling the multi-tap vector modulation.

17. The method of claim 14, wherein the generating an analog RF cancellation signal using multi-tap vector modulation comprises:

splitting a sample of the transmit signal into a plurality of transmit signal instances;

for each transmit signal instance of the plurality of transmit signal instances, providing different delays with respect to the transmit signal instances;

for each transmit signal instance of the plurality of transmit signal instances, providing in-phase and quadrature signal components for the transmit signal instances;

for each transmit signal instance of the plurality of transmit signal instances, mixing the in-phase and quadrature components of the transmit signal instance with in-phase and quadrature control inputs of the RF channel parameters; and

combining the plurality of transmit signal instances after the mixing to thereby provide a modulated cancellation signal.

18. The method of claim 14, wherein determining the residual channel estimation comprises:

providing residual channel estimation parameters based upon at least one of a correlation channel estimation based on a known transmit signal, a correlation channel estimation based on a known training sequence, a frequency domain channel estimation based on a pilot, or an adaptive filter based on least means squared (LMS) or recursive least squares (RLS).

19. A system for providing interference cancellation, the system comprising:

a channel estimation module operable to receive sampled signals from a transmit signal path of a communication station and sampled signals from a receive signal path of the communication station, the channel estimation module having circuitry providing RF channel parameters based upon a transmit sample signal from the transmit signal sampling module and a receive sample signal from the receive signal sampling module, wherein the RF channel parameters are utilized in providing interference cancellation of a received RF signal to result in a residual signal; and

a residual channel estimation module operable to receive sampled signals from the transmit signal path and sampled signals from a portion of the receive signal path carrying the residual signal, the residual channel estimation module having circuitry providing residual channel estimation parameters based upon the transmit sample signal from the transmit signal sampling module and the residual signal.

20. The system of claim 19, wherein the communication station is operable to transmit and receive using a same frequency simultaneously, wherein the signal sampled from the transmit signal path and the signal sampled from the receive signal path are in the same frequency.

21. The system of claim 19, wherein the signals sampled from the transmit signal path are sampled after modification of a transmit signal by a nonlinear component of the communication station.

22. The system of claim 19, further comprising:

an analog cancellation module coupled to the receive signal path and operable to provide an RF cancellation signal thereto, wherein the RF cancellation signal is generated using the RF channel parameters, and wherein combining the RF receive signal and the RF cancellation signal provides cancellation of strong self-interference resulting in the residual signal.

23. The system of claim 22, wherein the analog cancellation module comprises:

a multi-tap vector modulation module adaptively operable in response to RF channel parameters provided by the channel estimation module.

24. The system of claim 22, wherein the channel estimation module comprises:

a baseband channel estimation module; and

a RF channel conversion module, wherein the RF channel conversion module provides the RF channel parameters using a channel estimation provided by the baseband channel estimation module.

25. The system of claim 24, wherein the baseband channel estimation module comprises a channel estimation algorithm module adapted to calculate a RF channel response and a output block adapted to output the RF channel response as multipath in-phase and quadrature coefficients, and wherein the RF channel conversion module comprises a digital to analog converter (DAC) adapted to convert the multipath in-phase and quadrature coefficients to an analog signal and a filter adapted to smooth in-phase and quadrature coefficient changes in the analog signal.

26. The system of claim 25, wherein the channel estimation algorithm module is operable to calculate a correlation between the sampled signals from the transmit signal sampling module and the receive signal sampling module, to interpolate the results of the correlation using a sinc function, and to calculate a plurality of delay relationships.

27. The system of claim 19, wherein the residual channel estimation module is adapted to provide the residual channel estimation parameters based upon at least one of a correlation channel estimation based on a known transmit signal, a correlation channel estimation based on a known training sequence, a frequency domain channel estimation based on a pilot, or an adaptive filter based on least means squared (LMS) or recursive least squares (RLS).

28. The system of claim 19, further comprising:

a cancellation signal generator module coupled to the residual channel estimation module, wherein the cancellation signal generator module provides a residual cancellation signal using residual channel estimation parameters.

29. The system of claim 28, wherein the cancellation signal generator module comprises a finite impulse response (FIR) module.