Inter-satellite link aided UE positioning in non-terrestrial network

1. An apparatus for wireless communication at a user equipment (UE), comprising:

memory;

at least one transceiver; and

at least one processor communicatively connected to the memory and the at least one transceiver, the at least one processor configured to:

receive, from a first satellite, a first positioning reference signal (PRS) at a first reception time (T_ Rx _ sat _ 1 );

receive, from a second satellite, a second PRS at a second reception time (T_ Rx _ sat _ 2 ) and an indication of a transmission-reception time difference (T sat_2_Tx→Rx ), the transmission-reception time difference (T sat_2_Tx→Rx ) being a difference between a time the second satellite transmits the second PRS to the UE and a time the second satellite receives a reference signal (RS) from the first satellite; and

calculate a reference signal time difference (RSTD) for the first PRS and the second PRS based at least in part on the first reception time of the first PRS (T_ Rx _ sat _ 1 ), the second reception time of the second PRS (T_ Rx _ sat _ 2 ), and the transmission-reception time difference (T sat_2_Tx→Rx ).

2. The apparatus of claim 1 , wherein the RSTD for the first PRS and the second PRS (RSTD_ 1_2 ) is calculated based on:

RSTD_1_2= T_ Rx_sat_1 −T_ Rx _ sat _ 2 −( T gap,iner-sat_RS_1→PRS_1 +T prop,sat_1→sat_2 +T sat_2_Tx→Rx ),

wherein the T gap,iner-sat_RS_1→PRS_1 is a time gap between a time the first satellite transmits the first PRS to the UE and a time the first satellite transmits the RS to the second satellite, and the T prop,sat_1→sat_2 is a signal propagation time between the first satellite and the second satellite.

3. The apparatus of claim 2 , wherein the at least one processor is further configured to:

receive, from the first satellite, an indication of the T gap,iner-sat_RS_1→PRS_1 .

4. The apparatus of claim 2 , wherein the at least one processor is further configured to:

receive, from the second satellite, an indication of the T prop,sat_1→sat_2 .

5. The apparatus of claim 1 , wherein the transmission-reception time difference (T sat_2_Tx→Rx ) is associated with one or more of: a satellite identifier (ID), a transmission reception point (TRP) ID, a PRS ID, or a timestamp.

6. The apparatus of claim 1 , wherein the at least one processor is further configured to:

calculate a position of the UE based at least in part on the RSTD for the first PRS and the second PRS.

7. An apparatus for wireless communication at a first satellite, comprising:

memory;

at least one transceiver; and

at least one processor communicatively connected to the memory and the at least one transceiver, the at least one processor configured to:

transmit, to a second satellite, a reference signal (RS) at a first transmission time;

transmit, to a user equipment (UE), a positioning reference signal (PRS) at a second transmission time; and

transmit, to the UE, an indication of a time gap (T gap,iner-sat_RS_1→PRS_1 ) between the first transmission time and the second transmission time.

8. The apparatus of claim 7 , wherein the second satellite has a capability to provide baseband onboard processing.

9. The apparatus of claim 7 , wherein the RS is a second PRS.

10. The apparatus of claim 7 , wherein the at least one processor is further configured to:

receive, from a gateway or a location management function (LMF), a resource allocation for transmitting the RS.

11. The apparatus of claim 7 , wherein the at least one processor is further configured to:

receive, from a gateway or a location management function (LMF), a resource allocation for transmitting the RS.

12. The apparatus of claim 7 , wherein the at least one processor is further configured to:

receive, from a gateway or a location management function (LMF), a configuration of one or more transmission beams for transmitting the RS.

13. An apparatus for wireless communication at a second satellite, comprising:

memory;

at least one transceiver; and

at least one processor communicatively connected to the memory and the at least one transceiver, the at least one processor configured to:

receive, from a first satellite, a reference signal (RS) at a first reception time;

transmit, to a user equipment (UE), a positioning reference signal (PRS) at a first transmission time; and

transmit, to the UE, an indication of a transmission-reception time difference (T sat_2_Tx→Rx ) between the first reception time and the first transmission time.

14. The apparatus of claim 13 , wherein the second satellite has a capability to provide baseband onboard processing.

15. The apparatus of claim 13 , wherein the at least one processor is further configured to:

transmit, to the UE, an indication of a signal propagation time (T prop,sat_1→sat_2 ) between the first satellite and the second satellite.

16. The apparatus of claim 13 , wherein the transmission-reception time difference (T sat_2_Tx→Rx ) is associated with one or more of: a satellite identifier (ID), a transmission reception point (TRP) ID, a PRS ID, or a timestamp.

17. The apparatus of claim 13 , wherein the at least one processor is further configured to:

receive, from a gateway or a location management function (LMF), a configuration to transmit the PRS based on the RS.

18. The apparatus of claim 13 , wherein the at least one processor is further configured to:

receive, from a gateway or a location management function (LMF), a measurement gap for receiving the RS.

19. The apparatus of claim 13 , wherein the RS is a second PRS.

20. The apparatus of claim 13 , wherein the at least one processor is further configured to:

receive, from a gateway or a location management function (LMF), a resource allocation for receiving the RS.

21. The apparatus of claim 13 , wherein the at least one processor is further configured to:

receive, from a gateway or a location management function (LMF), a configuration of one or more reception beams for receiving the RS.

22. An apparatus for wireless communication at a user equipment (UE), comprising:

memory;

at least one transceiver; and

at least one processor communicatively connected to the memory and the at least one transceiver, the at least one processor configured to:

receive, from a first satellite, a first positioning reference signal (PRS) at a first reception time (T_ Rx _ sat _ 1 );

receive, from a second satellite, a second PRS at a second reception time (T_ Rx _ sat _ 2 ), the second PRS being transmitted from the first satellite and relayed to the UE via the second satellite; and

calculate a reference signal time difference (RSTD) for the first PRS and the second PRS based at least in part on the first reception time of the first PRS (T_ Rx _ sat _ 1 ), the second reception time of the second PRS (T_ Rx _ sat _ 2 ), and a group delay (T GD_BP ) associated with the second satellite.

23. The apparatus of claim 22 , wherein the second satellite does not have a capability to provide baseband onboard processing.

24. The apparatus of claim 22 , wherein the RSTD for the first PRS and the second PRS (RSTD_ 1_2 ) is calculated based on:

RSTD_1_2= T_ Rx_sat_1 −T_ Rx _ sat _ 2 −( T gap,PRS_2→PRS_1 +T prop,sat_1→sat_2 +T GD_BP ),

wherein the T gap,PRS_2→PRS_1 is a time gap between a time the first satellite transmits the first PRS to the UE and a time the first satellite transmits the second PRS to the second satellite, and the T prop,sat_1→sat_2 is a signal propagation time between the first satellite and the second satellite.

25. The apparatus of claim 24 , wherein the at least one processor is further configured to:

receive, from the first satellite, an indication of the T gap,PRS_2→PRS_1 .

26. The apparatus of claim 24 , wherein the at least one processor is further configured to:

receive, from the second satellite, an indication of the T prop,sat_1→sat_2 .

27. The apparatus of claim 22 , wherein the at least one processor is further configured to:

receive, from a location management function (LMF), the group delay (T GD_BP ) via assistance data (AD).

28. The apparatus of claim 22 , wherein the group delay (T GD_BP ) is associated with one or more of: a satellite identifier (ID) or a transmission reception point (TRP) ID.

29. The apparatus of claim 22 , wherein the at least one processor is further configured to:

calculate a position of the UE based at least in part on the RSTD for the first PRS and the second PRS.

30. The apparatus of claim 22 , wherein the second PRS is not a re-generated signal of the first PRS.