Noise cancelling amplify-and-forward (in-band) relay with self-interference cancellation

• US 10,700,766 B2
• Filed: 04/17/2018
• Issued: 06/30/2020
• Est. Priority Date: 04/19/2017
• Status: Active Grant

• Current Assignee: Amir Keyvan Khandani
• Original Assignee: Amir Keyvan Khandani
• Inventors: Khandani, Amir Keyvan
• Primary Examiner(s): Dean, Raymond S
• Application Number:
  US15/955,439
• Publication Number:
  US 20180309502A1
• Time in Patent Office: 805 Days
• CPC Class Codes: H03H 7/12 Bandpass or bandstop filters with adjustable bandwidth and fixed centre frequency H03H7/09 takes precedence; automatic control of bandwidth in amplifiers H03G5/16
• CPC Class Codes: H04B 7/0857 using maximum ratio combining techniques, e.g. signal-to- interference ratio [SIR], received signal strenght indication [RSS]
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
• CPC Class Codes: H04B 7/15535 Control of relay amplifier gain amplifier gain control in general H03G3/00; gain control reducing self - or loop interference H04B7/15578
• CPC Class Codes: H04B 7/15557 Selecting relay station operation mode, e.g. between amplify and forward mode, decode and forward mode or FDD - and TDD mode
• CPC Class Codes: H04B 7/15578 by gain adjustment
• CPC Class Codes: H04L 5/14 Two-way operation using the same type of signal, i.e. duplex
• CPC Class Codes: H04L 5/1461 Suppression of signals in the return path, i.e. bidirectional control circuits
• CPC Class Codes: H04W 72/23 in the downlink direction of a wireless link, i.e. towards a terminal

Abstract

The methods and systems for amplify-and-forward (in-band) relaying relate to beamforming techniques including receive and transmit beamforming for reducing self-interference, and improving Signal-to-Noise Ratio (SNR), or Signal to Interference plus Noise Ratio (SINR), of an incoming signal (to be relayed). The incoming signal is amplified and retransmitted simultaneously with the incoming signal, and over the same frequency band as that of an incoming signal.

Claims

1. An apparatus comprising:

a receive front-end including a plurality of receive antennas configured to perform receive beamforming, wherein the plurality of receive antennas include a respective first plurality of radio frequency beamforming filters, and wherein the receive front-end operates within at least a first frequency band and is responsive to an incoming radio frequency signal;

an amplification stage coupled to the receive front end, the amplification stage configured to amplify the incoming radio frequency signal received at the receive front-end and to produce an amplified incoming radio frequency signal;

a transmit front-end coupled to the amplification stage to receive the amplified incoming radio frequency signal, wherein the transmit front-end includes a plurality of transmit antennas configured to perform transmit beamforming, wherein the plurality of transmit antennas include a respective second plurality of radio frequency beamforming filters, and wherein the transmit front-end operates within at least the first frequency band, the transmit front-end being configured to transmit the amplified incoming radio frequency signal to a distant receiver while the receive front-end is receiving the incoming radio frequency signal;

a signature signal generation circuit coupled to the transmit front-end, wherein the signature signal generation circuit is configured to generate a signature signal that is included within the first frequency band in which the amplified incoming radio frequency signal is to be transmitted, and wherein the signature signal includes a periodic sequence to distinguish the signature signal from the transmitted amplified incoming radio frequency signal; and

a self-interference measurement circuit configured to generate beamforming control signals to control at least one of (i) the plurality of receive antennas including the respective first plurality of radio beamforming filters or (ii) the plurality of transmit antennas including the respective second plurality of beamforming filters, wherein the self-interference measurement circuit is further configured to (i) detect the signature signal present at the receive front-end to measure self-interference and (ii) to generate the beamforming control signals based on the detected signature signal such that an amount of the transmitted amplified incoming radio frequency signal and the signature signal leaked from the transmit front-end back to the receive front-end is reduced.

2. The apparatus of claim 1, wherein each of the plurality of receive antennas separately receives the incoming radio frequency signal to enable radio frequency combining and amplification, and wherein the respective first plurality of radio frequency beamforming filters are configured to create a receive null with respect to the transmit front-end so as to reduce a signal leakage from the transmit front-end back to the receive front-end.

3. The apparatus of claim 1, wherein each of the respective first plurality of radio frequency beamforming filters in the receive front-end is configured to increase a beamforming gain to improve a signal-to-noise ratio of the amplified incoming radio frequency signal.

4. The apparatus of claim 1, wherein the plurality of transmit antennas receive the amplified incoming radio frequency signal for transmit to the distant receiver via the respective second plurality of radio frequency beamforming filters that are configured to produce a transmit null with respect to the receive front-end so as to reduce a signal leakage from the transmit front-end back to the receive front-end.

5. The apparatus of claim 1, wherein each of the respective first plurality of radio frequency beamforming filters in the receive front-end or each of the respective second plurality of radio frequency beamforming filters in the transmit front-end has at least two states, wherein the at least two states include a 0°

phase shift and a 180°

phase shift, and wherein each filter having the at least two states is configured such that the at least two states are controlled selectively to improve isolation between the receive front-end and the transmit front-end.

6. The apparatus of claim 1, wherein the plurality of transmit antennas receive the amplified incoming radio frequency signal for transmit to the distant receiver via the respective second plurality of radio frequency beamforming filters, and wherein the respective second plurality of radio frequency beamforming filters are configured to produce one or more transmit beams that focus the amplified incoming radio frequency signal onto the distant receiver.

7. The apparatus of claim 5, wherein the at least two states further include a disconnect state.

8. The apparatus of claim 1 further comprising:

a training signal generation circuit coupled to the transmit front-end, wherein the training signal generation circuit is configured to generate a training signal that is included with the amplified incoming radio frequency signal for transmit, and wherein the training signal provides initial training for adapting to self-interference between the receive front-end and the transmit front-end.

9. The apparatus of claim 1, wherein the transmit front-end and the receive front end operate within at least two frequency bands simultaneously relaying uplink and downlink radio frequency signals in a Frequency Division Duplex (FDD) wireless network.

10. The apparatus of claim 9, wherein:

the plurality of receive antennas are organized into at least two sets of receive antennas, the first set of receive antennas operating within the first frequency band and a second set of receive antennas operating within a second frequency band, and

the plurality of transmit antennas are organized into at least two sets of transmit antennas, the first set of transmit antennas operating within the first frequency band and a second set of transmit antennas operating within the second frequency band.

11. The apparatus of claim 10, wherein a number of receive antennas in the at least two sets of receive antennas is greater than a number of transmit antennas in the at least two sets of transmit antennas.

12. The apparatus of claim 10, wherein each of the the plurality of receive antennas includes a corresponding radio frequency beamforming filter that has a connected state and a disconnected state.

13. The apparatus of claim 12, wherein one or more of the radio frequency beamforming filters in the at least two sets of receive antennas are in the disconnected state to prevent signals from corresponding one or more receive antennas from entering a radio frequency combiner to improve signal-to-noise ratio.

18. The apparatus of claim 1, wherein the periodic sequence comprises a binary Alexis sequence.

19. The apparatus of claim 1, wherein the self-interference measurement circuit is further configured to evaluate a level of the signature signal over a given observation basis to measure an amount of self-interference over the first frequency band.

20. The apparatus of claim 19, wherein the given observation basis comprises an observation coordinate system including a discrete set of equally spaced points over the first frequency band.

14. An apparatus comprising:

a receive front-end including a plurality of receive antennas configured to perform receive beamforming, wherein the plurality of receive antennas include a respective first plurality of radio frequency beamforming filters, and wherein the receive front-end operates within at least a first frequency band and is responsive to an incoming radio frequency signal;

an amplification stage coupled to the receive front end, the amplification stage configured to amplify the incoming radio frequency signal received at the receive front-end and to produce an amplified incoming radio frequency signal;

a transmit front-end coupled to the amplification stage to receive the amplified incoming radio frequency signal, wherein the transmit front-end includes a plurality of transmit antennas configured to perform transmit beamforming, wherein the plurality of transmit antennas include a respective second plurality of radio frequency beamforming filters, and wherein the transmit front-end operates within at least the first frequency band, the transmit front-end being configured to transmit the amplified incoming radio frequency signal to a distant receiver;

a signature signal generation circuit coupled to the transmit front-end, wherein the signature signal generation circuit is configured to generate a signature signal that is included within the first frequency band in which the amplified incoming radio frequency signal is to be transmitted, and wherein the signature signal includes a periodic sequence to distinguish the signature signal from the transmitted amplified incoming radio frequency signal; and

a self-interference measurement circuit configured to generate beamforming control signals for the transmit front-end and the receive front-end, wherein the self-interference measurement circuit is further configured to (i) detect the signature signal present at the receive front-end to measure self-interference and (ii) to generate the beamforming control signals based on the detected signature signal such that the signature signal leaked from the transmit front-end back to the receive front-end is reduced.

15. The apparatus of claim 14, wherein the periodic sequence comprises a binary Alexis sequence.

16. The apparatus of claim 14, wherein the self-interference measurement circuit is further configured to evaluate a level of the signature signal over a given observation basis to measure an amount of self-interference over the first frequency band.

17. The apparatus of claim 16, wherein the given observation basis comprises an observation coordinate system including a discrete set of equally spaced points over the first frequency band.