Methods for training of full-duplex wireless systems

1. An apparatus comprising:

a first full-duplex transceiver including:

an antenna configured to exchange radio-frequency signals with a second full-duplex transceiver;

a processor coupled to the antenna, the processor configured to:

measure a self-interference signal;

compare the self-interference signal with a threshold to determine whether a residual self-interference signal exceeds the threshold; and

in response to the determination that the residual self-interference signal exceeds the threshold, direct a self-training operation, the self-training operation using self-training signals that are phase-shifted versions of a set of distant-training signals.

2. The apparatus of claim 1 , wherein the processor is further configured to embed information based on a signal-to-interference plus noise ratio in a distant training signal transmitted to the second full-duplex transceiver.

3. The apparatus of claim 1 , wherein the processor is further configured to embed information on an index of a layer to use for self-training, including information related to phase of distant-training symbols sent to a distant counterpart.

4. The apparatus of claim 1 , wherein the processor is further configured to:

direct the self-training operation by transmission of self-training symbols in half-duplex mode; and

send a message to the second full-duplex transceiver to remain silent during the self-training operation.

5. The apparatus of claim 1 , wherein the processor is configured to:

transmit a first distant-training symbol of the set of distant-training symbols to the second full-duplex transceiver to teach the second full-duplex transceiver of a channel from the first to second full-duplex transceiver; and

receive a second distant-training symbol from the second full-duplex transceiver to enable teaching of the first full-duplex transceiver of a channel from the second to the first full-duplex transceiver.

6. The apparatus of claim 5 , wherein the processor is configured to transmit the first distant-training signal by time-multiplexing the first distant-training signal in half-duplex mode.

7. The apparatus of claim 5 , wherein the processor is configured to transmit the first distant-training signal by time-multiplexing the first distant-training signal in full-duplex mode.

8. The apparatus of claim 5 , wherein the processor is configured to transmit the first distant-training symbol by time-multiplexing the first distant-training symbol in a different time slot than a time slot used for receiving the second distant-training symbol.

9. The apparatus of claim 5 , wherein the processor is configured to transmit the first distant-training symbol by time-multiplexing the first distant-training symbol in a time slot equal to a time slot used for receiving the second distant-training symbol.

10. The apparatus of claim 8 , wherein the processor is configured to use the second distant-training symbol to determine self-interference in the channel from the second full-duplex transceiver to the first full-duplex transceiver.

11. The apparatus of claim 10 , wherein the processor is configured to direct the self-training operation based on the determined self-interference in the channel from the second full-duplex transceiver to the first full-duplex transceiver.

12. The apparatus of claim 11 , wherein the first transceiver sends a message to the second transceiver to delay performing a distant training operation if performing a self-training operation.

13. The apparatus of claim 1 , wherein the self-training operation comprises transmitting successively first and second distant-training symbols of the set of distant-training symbols from the first full-duplex transceiver to the second full-duplex transceiver with a time interval for the successive transmission that is adapted to a rate of variations in a channel from the first full-duplex transceiver to the second full-duplex transceiver.

14. The apparatus of claim 1 , wherein performing a self-training operation comprises transmitting a partial self-training signal that comprises multiple layers of different depths in a nested manner.