UE uplink timing for non-terrestrial networks

1 . An apparatus for a non-terrestrial network (NTN) user equipment (UE), the apparatus comprising:

processing circuitry to configure the NTN UE to:

determine a timing advance adjustment is to be applied for an uplink (UL) transmission to a 5 th generation NodeB (gNB) through a Global Navigation Satellite System (GNSS) satellite;

receive, from the gNB, a configuration of a periodicity for estimating a UE-specific timing advance (TA) based on GNSS position and satellite ephemeris information;

estimate the UE-specific TA at the periodicity provided by the configuration;

limit a change of the timing advance adjustment between a maximum aggregate adjustment rate and a minimum aggregate adjustment rate to establish a TA that is dependent on the UE-specific TA; and

transmit, to the gNB through the GNSS satellite, the UL transmission using the TA; and

a memory configured to store the TA.

2 . The apparatus of claim 1 , wherein the TA is further dependent on a common TA, an integer timing-advance N TA , and a fixed offset N TA,offset .

3 . The apparatus of claim 1 , wherein:

the minimum aggregate adjustment rate is Tp per second,

the maximum aggregate adjustment rate is Tq per 200 ms, and

Tp and Tq depend on a subcarrier spacing (SCS) of the UL transmission.

4 . The apparatus of claim 1 , wherein the processing circuitry further configures the NTN UE to adjust the TA based on a message from the gNB.

5 . The apparatus of claim 4 , wherein the message is a medium access control (MAC) control element (CE) message.

6 . The apparatus of claim 1 , wherein the processing circuitry further configures the NTN UE to receive, in a broadcast transmission from the gNB, an update periodicity to periodically update the TA.

7 . The apparatus of claim 1 , wherein the processing circuitry further configures the NTN UE to receive, in dedicated signaling from the gNB, an update periodicity to periodically update the TA.

8 . The apparatus of claim 1 , wherein the processing circuitry further configures the NTN UE to determine whether to apply open loop or closed loop TA updates dependent on a network configuration based on broadcast signaling from the gNB.

9 . The apparatus of claim 1 , wherein the processing circuitry further configures the NTN UE to determine whether to apply open loop or closed loop TA updates dependent on a network configuration based on dedicated signaling from the gNB.

10 . The apparatus of claim 3 , wherein the processing circuitry further configures the NTN UE to:

adjust the TA gradually toward an updated UE-specific TA value by limiting timing changes within the maximum and minimum aggregate adjustment rates, excluding changes due to satellite position updates, and

after open loop TA updates are configured, autonomously estimate a UE-specific TA based on GNSS position and satellite ephemeris information without performing a TA procedure with the gNB.

11 . The apparatus of claim 1 , wherein the maximum aggregate adjustment rate and the minimum aggregate adjustment rate excluding changes to the timing advance due to satellite position updates and changes to a common timing advance (N TA,common ) between a previous uplink transmission and a current uplink transmission.

12 . The apparatus of claim 1 , wherein a configured periodicity for estimating the UE-specific TA is independent from a periodicity at which the gNB provides TA commands for a feeder link component of the TA.

13 . The apparatus of claim 1 , wherein the processing circuitry further configures the NTN UE to maintain a validity timer for the UE-specific TA based on a configured periodicity, and re-estimate the UE-specific TA upon expiration of the validity timer.

14 . A non-transitory computer-readable storage medium that stores instructions for execution by one or more processors of a non-terrestrial network (NTN) user equipment (UE), the one or more processors to configure the NTN UE to, when the instructions are executed:

determine a timing advance adjustment is to be applied for an uplink (UL) transmission to a 5 th generation NodeB (gNB) through a Global Navigation Satellite System (GNSS) satellite;

receive, from the gNB, a configuration of a periodicity for estimating a UE-specific timing advance (TA) based on GNSS position and satellite ephemeris information;

estimate the UE-specific TA at the periodicity provided by the configuration;

limit a change of the timing advance adjustment between a maximum aggregate adjustment rate and a minimum aggregate adjustment rate to establish a TA that is dependent on the UE-specific TA; and

transmit, to the gNB through the GNSS satellite, the UL transmission using the TA.

15 . The medium of claim 14 , wherein the TA is further dependent on a common TA, an integer timing-advance N TA , and a fixed offset N TA,offset .

16 . The medium of claim 14 , wherein:

the minimum aggregate adjustment rate is Tp per second,

the maximum aggregate adjustment rate is Tq per 200 ms, and

Tp and Tq depend on a subcarrier spacing (SCS) of the UL transmission.

17 . The medium of claim 14 , wherein the one or more processors further configure the NTN UE to, when the instructions are executed, adjust the TA based on a message from the gNB.

18 . The medium of claim 17 , wherein the message is a medium access control (MAC) control element (CE) message.

19 . The medium of claim 14 , wherein the one or more processors further configure the NTN UE to, when the instructions are executed, receive, in a broadcast transmission from the gNB, an update periodicity to periodically update the TA.

20 . The medium of claim 14 , wherein the one or more processors further configure the NTN UE to, when the instructions are executed, receive, in dedicated signaling from the gNB, an update periodicity to periodically update the TA.