User equipment timing synchronization for CSI-RS based radio resource management

1. A method, comprising:

at a user equipment (UE) being served by a serving cell of a network:

receiving, from the serving cell, a measurement configuration message indicating the UE is to measure channel state information reference signals (CSI-RS) from a target cell of the network, wherein the measurement configuration message does not include Synchronization Signal Block (SSB) information for the target cell but further comprises an indication of whether the target cell transmits SSBs;

determining, based on at least the measurement configuration message, a time and frequency resource on which the CSI-RS of the target cell are to be transmitted; and

measuring the CSI-RS of the target cell.

2. The method of claim 1 , wherein the measurement configuration message indicates the target cell transmits SSBs.

3. The method of claim 1 , wherein the measurement configuration message indicates the target cell does not transmit SSBs.

4. The method of claim 2 , wherein the measurement configuration message comprises a timing of the serving cell and an offset value indicating an offset of a timing for the target cell, the method further comprising:

deriving a timing of the target cell based on, at least, the timing of the serving cell and the offset value, wherein a timing of the target cell indicates the time resource.

5. The method of claim 4 , wherein, when the offset value is equal to 0, the offset value is indicated by a single bit in the measurement configuration message.

6. The method of claim 2 , wherein the measurement configuration message comprises a timing of the serving cell, the method further comprising:

determining a search window in which at least one CSI-RS symbol is transmitted by the target cell based on, at least, a cell phase synchronization error and a propagation delay difference between the serving cell and the target cell.

7. The method of claim 2 , further comprising:

determining a search window in which at least one SSB is transmitted by the target cell;

detecting the at least one SSB in the search window;

synchronizing with the target cell based on the at least one SSB, wherein the SSB comprises the time and frequency resource on which the CSI-RS of the target cell are to be transmitted.

8. The method of claim 7 , wherein the search window is determined based on, at least, a timing of the serving cell, wherein the timing of the serving cell is included in the measurement configuration message.

9. The method of claim 2 , wherein the measurement configuration message further comprises configuration information indicating the UE is to perform System Frame Number (SFN) and Frame Timing Difference (SFTD) measurements between the serving cell and the target cell, the method further comprising:

performing SFTD measurements between the serving cell and the target cell; and

determining a timing difference between the serving cell and the target cell based on the SFTD measurements, wherein the timing resource is determined based on the timing difference and a timing of the serving cell included in the measurement configuration message.

10. A user equipment (UE), comprising:

one or more processors configured to:

receive, from a serving cell, a measurement configuration message indicating the UE is to measure channel state information reference signals (CSI-RS) from a target cell of the network, wherein the measurement configuration message does not include Synchronization Signal Block (SSB) information for the target cell but further comprises an indication of whether the target cell transmits SSBs;

determine, based on at least the measurement configuration message, a time and frequency resource on which the CSI-RS of the target cell are to be transmitted; and

measure the CSI-RS of the target cell; and

a transceiver to transmit the CSI-RS measurements to the serving cell.

11. The UE of claim 10 , wherein the measurement configuration message indicates the target cell transmits SSBs.

12. The UE of claim 10 , wherein the measurement configuration message indicates the target cell does not transmit SSBs.

13. The UE of claim 12 , wherein the measurement configuration message comprises a timing of the serving cell and an offset value indicating an offset of a timing for the target cell, the one or more processors further configured to:

derive a timing of the target cell based on, at least, the timing of the serving cell and the offset value, wherein a timing of the target cell indicates the time resource.

14. The UE of claim 13 , wherein, when the offset value is equal to 0, the offset value is indicated by a single bit in the measurement configuration message.

15. The UE of claim 12 , wherein the measurement configuration message comprises a timing of the serving cell, the one or more processors further configured to:

determine a search window in which at least one CSI-RS symbol is transmitted by the target cell based on, at least, a cell phase synchronization error and a propagation delay difference between the serving cell and the target cell.

16. The UE of claim 11 , wherein the one or more processors are further configured to:

determine a search window in which at least one SSB is transmitted by the target cell;

detect the at least one SSB in the search window;

synchronize with the target cell based on the at least one SSB, wherein the SSB comprises the time and frequency resource on which the CSI-RS of the target cell are to be transmitted.

17. The UE of claim 15 , wherein the search window is determined based on, at least, a timing of the serving cell, wherein the timing of the serving cell is included in the measurement configuration message.

18. The UE of claim 11 , wherein the measurement configuration message further comprises configuration information indicating the UE is to perform System Frame Number (SFN) and Frame Timing Difference (SFTD) measurements between the serving cell and the target cell, the one or more processors further configured to:

perform SFTD measurements between the serving cell and the target cell; and

determine a timing difference between the serving cell and the target cell based on the SFTD measurements, wherein the timing resource is determined based on the timing difference and a timing of the serving cell included in the measurement configuration message.

19. A non-transitory computer readable storage medium comprising instructions that when executed by a processor perform operations, comprising:

receiving, from a serving cell, a measurement configuration message indicating the UE is to measure channel state information reference signals (CSI-RS) from a target cell of the network, wherein the measurement configuration message does not include Synchronization Signal Block (SSB) information for the target cell but further comprises an indication of whether the target cell transmits SSBs;

determining, based on at least the measurement configuration message, a time and frequency resource on which the CSI-RS of the target cell are to be transmitted; and

measuring the CSI-RS of the target cell.

20. The non-transitory computer readable storage medium of claim 19 , wherein the measurement configuration message indicates one of the target cell transmits SSBs or the target cell does not transmit SSBs.