Precoder selection for minimizing impact of cyclic shift port virtualization on communication performance in joint communication and sensing

1 . A method of joint communication and sensing of a target obstacle, comprising:

deploying an integrated sensing and communication (ISAC) node, comprising an ISAC transmitter having M transmitting antenna(s) and a radar receiver having L receiving antenna(s), wherein the M and L are integers;

transmitting radio frequency (RF) signals carrying data to a communication receiver by the M transmitting antenna(s) of the ISAC transmitter;

receiving radio frequency (RF) signals reflected by the target obstacle by the L receiving antenna(s);

obtaining a sensing result based on the reflected radio frequency (RF) signals; and

determining a sounding result based on a reference signal sent by the communication receiver;

wherein the RF signals transmitted by the M transmitting antenna(s) of the ISAC transmitter are applied with cyclic shift diversity; and

wherein the RF signals transmitted by the M transmitting antenna(s) of the ISAC transmitter contain precoders which are selected by aligning a range of communication direction linked to a communication channel between the ISAC node and the communication receiver with minimal capacity loss based on the sounding result.

2 . The method of claim 1 , wherein the radio frequency (RF) signals transmitted by the M transmitting antenna(s) of the ISAC transmitter are cyclic shifted in time domain.

3 . The method of claim 1 , wherein a virtual receiving array is generated by the M transmitting antenna(s) and the L receiving antenna(s).

4 . The method of claim 1 , wherein the radio frequency (RF) signals transmitted by the M transmitting antenna(s) of the ISAC transmitter are orthogonal frequency domain multiplexing (OFDM) signals.

5 . The method of claim 4 , wherein the radio frequency (RF) signals transmitted by the M transmitting antenna(s) of the ISAC transmitter form virtually orthogonal transmitter ports that are distinguishable at each of the L receiving antenna(s).

6 . The method of claim 1 , wherein the reference signal is an uplink reference signal.

7 . The method of claim 6 , wherein the uplink reference signal is a sounding reference signal (SRS) or a demodulation reference signal (DMRS).

8 . The method of claim 1 , wherein the precoders are selected to cause a frequency-domain flatness at an Angle of Departure (AoD), which is the ratio of a minimum value to the maximum value of the communication channel frequency domain response per resource element at the range of communication direction, to be close to 1.

9 . A method of joint communication and sensing of a target obstacle, comprising:

deploying an integrated sensing and communication (ISAC) node, comprising an ISAC transmitter having M transmitting antenna(s) and a radar receiver having L receiving antenna(s), wherein the M and L are integers;

transmitting radio frequency (RF) signals carrying data to a communication receiver by the M transmitting antenna(s) of the ISAC transmitter;

receiving radio frequency (RF) signals reflected by the target obstacle by the L receiving antenna(s);

obtaining a sensing result based on the reflected radio frequency (RF) signals; and

obtaining a transmit precoder matrix indicator (TPMI) index based on a feedback signal sent by the communication receiver;

wherein the RF signals transmitted by the M transmitting antenna(s) of the ISAC transmitter are applied with cyclic shift diversity; and

wherein the RF signals transmitted by the M transmitting antenna(s) of the ISAC transmitter contain precoders which are selected by aligning one or more communication direction(s) linked to a communication channel between the ISAC node and the communication receiver with minimal capacity loss based on the TPMI index.

10 . The method of claim 9 , wherein the radio frequency (RF) signals transmitted by the M transmitting antenna(s) of the ISAC transmitter are cyclic shifted in time domain.

11 . The method of claim 10 , wherein the precoders are selected to generate one or more mainlobe(s) of an Angle of Departure (AoD) whose direction(s) aligns with that corresponding to the minimum capacity loss at the communication receiver.

12 . The method of claim 9 , wherein the radio frequency (RF) signals are orthogonal frequency domain multiplexing (OFDM) signals.

13 . An integrated sensing and communication (ISAC) node, comprising:

an ISAC transmitter having M transmitting antenna(s) for transmitting radio frequency (RF) signals carrying data to a communication receiver; and

a radar receiver having L receiving antenna(s) for receiving radio frequency (RF) signals reflected by a target obstacle;

wherein the M and L are integers; and

wherein the ISAC node estimates a channel condition of a communication channel between the ISAC node and the communication receiver; and

wherein the RF signals transmitted by the M transmitting antenna(s) are applied with cyclic shift diversity and contain precoders which are selected by aligning a range of communication direction linked to the communication channel between the ISAC node and the communication receiver with minimal capacity loss based on the estimated channel condition.

14 . The ISAC node of claim 13 , wherein the radio frequency (RF) signals are cyclic shifted in time domain.

15 . The ISAC node of claim 13 , wherein a virtual receiving array is generated by the M transmitting antenna(s) and the N receiving antenna(s).

16 . The ISAC node of claim 13 , wherein the radio frequency (RF) signals transmitted by the M transmitting antenna(s) are orthogonal frequency domain multiplexing (OFDM) signals.

17 . The ISAC node of claim 16 , wherein the radio frequency (RF) signals transmitted by the M transmitting antenna(s) form virtually orthogonal transmitter ports that are distinguishable at each of the N receiving antenna(s).

18 . The ISAC node of claim 13 , wherein the channel condition of the communication channel between the ISAC node and the communication receiver is estimated based on a sounding reference signal (SRS) or a demodulation reference signal (DMRS) sent by the communication receiver.

19 . The ISAC node of claim 13 , wherein the channel condition of the communication channel between the ISAC node and the communication receiver is estimated based on a feedback signal containing a TPMI index sent by the communication receiver.

20 . The ISAC node of claim 13 , wherein the precoders are selected to cause a frequency-domain flatness at an Angle of Departure (AoD), which is the ratio of a minimum value to the maximum value of the communication channel frequency domain response per resource element at the range of communication direction, to be close to 1.