Methods, apparatus, and systems for delay spread measurement, reporting, and cyclic prefix determination

1 . A wireless transmit/receive unit (WTRU) comprising:

a processor configured to:

receive configuration information indicating a first transmission configuration indicator (TCI) state, a second TCI state, a first cyclic prefix (CP) size, a first channel state information-reference signal (CSI-RS) resource set, and a second CSI-RS resource set;

determine a first delay spread and a first measurement value associated with a first CSI-RS, wherein the first CSI-RS is received in a first CSI-RS resource based on the first TCI state and the first CP size, wherein the first CSI-RS resource is a CSI-RS resource in the first CSI-RS resource set;

determine a second delay spread and a second measurement value associated with a second CSI-RS, wherein the second CSI-RS is received in a second CSI-RS resource based on the second TCI state and a second CP size, wherein the second CSI-RS resource is a CSI-RS resource in the second CSI-RS resource set; and

send a first indication indicating whether the first delay spread is greater than or less than the first CP size.

2 . The WTRU of claim 1 , wherein the first indication indicates that the first delay spread is less than the first CP size, and wherein the processor is further configured to send a second indication indicating the second CSI-RS resource.

3 . The WTRU of claim 1 , wherein the first indication indicates that the first delay spread is greater than the first CP size, and wherein the processor is further configured to:

determine whether a difference between the first measurement value and the second measurement value is greater than a first threshold; and

send a request for a change in CP size if the difference between the first measurement value and the second measurement value is greater than the first threshold, or

send a second indication indicating the second CSI-RS resource if the difference between the first measurement value and the second measurement value is not greater than the first threshold.

4 . The WTRU of claim 1 , wherein the processor is configured to determine the first and second delay spreads and the second measurement value on a condition that a third measurement value associated with the first CSI-RS is below a second threshold.

5 . The WTRU of claim 1 , wherein the processor is configured to measure a first reference signal received power (RSRP) associated with a first CSI-RS resource of the first CSI-RS resource set.

6 . The WTRU of claim 5 , wherein the processor is configured to:

determine whether the first RSRP is greater than an RSRP threshold; and

measure a second RSRP associated with a second CSI-RS resource of the second CSI-RS resource set if the first RSRP is greater than the RSRP threshold.

7 . The WTRU of claim 1 , wherein the first indication indicates that the first delay spread is greater than the first CP size, and wherein the processor is configured to:

determine whether a difference between the first measurement value and the second measurement value is greater than a first threshold; and

send a second indication indicating the first delay spread if the difference between the first measurement value and the second measurement value is greater than the first threshold.

8 . The WTRU of claim 1 , wherein the first indication indicates that the first delay spread is greater than the first CP size, and the processor is configured to:

determine whether a difference between the first measurement value and the second measurement value is greater than a first threshold; and

send a request for a change in CP size if the difference between the first measurement value and the second measurement value is greater than the first threshold, or send a second indication indicating the second CSI-RS resource if the difference between the first measurement value and the second measurement value is not greater than the first threshold.

9 . The WTRU of claim 1 , wherein the processor is configured to send a CSI report that indicates a quantized delay spread associated with the first delay spread and the second delay spread.

10 . A method performed by a wireless transmit/receive unit (WTRU), the method comprising:

receiving configuration information indicating a first transmission configuration indicator (TCI) state, a second TCI state, a first cyclic prefix (CP) size, a first channel state information-reference signal (CSI-RS) resource set, and a second CSI-RS resource set;

determining a first delay spread and a first measurement value associated with a first CSI-RS, wherein the first CSI-RS is received in a first CSI-RS resource based on the first TCI state and the first CP size, wherein the first CSI-RS resource is a CSI-RS resource in the first CSI-RS resource set;

determining a second delay spread and a second measurement value associated with a second CSI-RS, wherein the second CSI-RS is received in a second CSI-RS resource based on the second TCI state and a second CP size, wherein the second CSI-RS resource is a CSI-RS resource in the second CSI-RS resource set; and

sending a first indication indicating whether the first delay spread is greater than or less than the first CP size.

11 . The method of claim 10 , wherein the first indication indicates that the first delay spread is less than the first CP size, and wherein the method further comprises sending a second indication indicating the second CSI-RS resource.

12 . The method of claim 10 , wherein the first indication indicates that the first delay spread is greater than the first CP size, and wherein the method further comprises:

determining whether a difference between the first measurement value and the second measurement value is greater than a first threshold; and

sending a request for a change in CP size if the difference between the first measurement value and the second measurement value is greater than the first threshold, or sending a second indication indicating the second CSI-RS resource if the difference between the first measurement value and the second measurement value is not greater than the first threshold.

13 . The method of claim 10 , further comprising determining the first and second delay spreads and the second measurement value on a condition that a third measurement value associated with the first CSI-RS is below a second threshold.

14 . The method of claim 10 , further comprising measuring a first reference signal received power (RSRP) associated with a first CSI-RS resource of the first CSI-RS resource set.

15 . The method of claim 14 , further comprising:

determining whether the first RSRP is greater than an RSRP threshold; and

measuring a second RSRP associated with a second CSI-RS resource of the second CSI-RS resource set if the first RSRP is greater than the RSRP threshold.

16 . The method of claim 10 , wherein the first indication indicates that the first delay spread is greater than the first CP size, and wherein the method further comprises:

determining whether a difference between the first measurement value and the second measurement value is greater than a first threshold; and

sending a second indication indicating the first delay spread if the difference between the first measurement value and the second measurement value is greater than the first threshold.

17 . The method of claim 10 , wherein the first indication indicates that the first delay spread is greater than the first CP size, and the method further comprises:

determining whether a difference between the first measurement value and the second measurement value is greater than a first threshold; and

sending a request for a change in CP size if the difference between the first measurement value and the second measurement value is greater than the first threshold, or sending a second indication indicating the second CSI-RS resource if the difference between the first measurement value and the second measurement value is not greater than the first threshold.

18 . The method of claim 10 , further comprising sending a CSI report that indicates a quantized delay spread associated with the first delay spread and the second delay spread.