Wireless communications in high speed train operation

1 . A method performed by a user equipment (UE) comprising:

obtaining a maximum timing advance (TA) for wireless communications to apply for a serving base station (BS) switching in a high speed train (HST) network;

updating the TA for wireless communications according to TA commands as the UE proceeds along a track in the HST network;

determining that a BS panel serving the UE has switched to a new BS panel along the track; and

responsive to determining that the BS panel serving the UE has switched to the new BS panel, setting the TA to a minimum TA for wireless communication or to the maximum TA for wireless communications based on a direction of travel of the HST with respect to the new BS panel.

2 . The method of claim 1 , wherein obtaining the maximum TA comprises receiving the maximum TA from the HST network.

3 . The method of claim 1 , wherein obtaining the maximum TA comprises obtaining the maximum TA by inspection of timing advance at the point of panel/BS change on a previous occasion.

4 . The method of claim 1 , wherein obtaining the maximum TA comprises obtaining the maximum TA by a pre-configuration of maximum TA on a previous occasion.

5 . The method of claim 1 , further comprising determining that the UE is in the HST network, the HST network comprising a uni-directional HST network.

6 . The method of claim 5 wherein determining that the UE is in the HST network comprises receiving an indication that the UE is in the HST network.

7 . The method of claim 1 , wherein determining that the BS panel serving the UE has switched to the next BS comprises determining that the BS panel serving the UE has switched based on a transmission configuration indicator (TCI) switch.

8 . The method of claim 1 , wherein determining that the BS panel serving the UE has switched to the next BS comprises determining that the BS panel serving the UE has switched based on a handover of the UE to the next BS.

9 . The method of claim 1 , wherein determining that the BS panel serving the UE has switched to the next BS comprises determining that the BS panel serving the UE has switched based on receiving a signal indicating a change in the BS panel serving the UE.

10 . The method of claim 1 wherein setting the TA to the minimum TA for wireless communication or to the maximum TA for wireless communications comprises setting the TA to the maximum TA responsive to the HST traveling towards the new BS panel immediately after handover or TCI change.

11 . The method of claim 1 wherein setting the TA to the minimum TA for wireless communication or to the maximum TA for wireless communications comprises setting the TA to the minimum TA responsive to the HST traveling away from the new BS panel immediately after handover or TCI change.

12 . A method performed by a user equipment (UE) comprising:

determining a Doppler shift relating to a speed of a high speed train (HST);

using a first base station (BS) panel to transmit and receive wireless communications in a bi-directional HST network based on the Doppler shift;

determining that the first BS panel serving the UE has switched to a second BS panel; and

using the second panel to transmit and receive wireless communications in the bi-directional HST network based on a reversed Doppler shift.

13 . The method of claim 12 , further comprising:

determining that the UE is in a bi-directional high speed train (HST) network.

14 . The method of claim 12 wherein determining that the UE is in the bi-directional HST network comprises receiving an indication that the UE is in the bi-directional HST network.

15 . The method of claim 12 , wherein determining the Doppler shift comprises: using a frequency reference source independent of signals received from base stations along a track the UE is traveling along in the bi-directional HST network.

16 . The method of claim 15 , wherein using the frequency reference source independent of signals received from the base stations comprises:

using a frequency source provided by an onboard operation control system for the HST; or

using a global positioning system (GPS) to determine the Doppler shift.

17 . The method of claim 12 , wherein determining that the BS panel serving the UE has switched to a second BS panel comprises:

determining that the BS panel serving the UE has switched based on a transmission configuration indicator (TCI) switch;

determining that the BS panel serving the UE has switched based on a handover of the UE to a next BS; or

determining that the BS panel serving the UE has switched based on receiving a signal indicating a change in the BS panel serving the UE.

18 . A method performed by a user equipment (UE) in a bi-directional high speed train (HST) network deployment, the method comprising:

maintaining a first Doppler-compensated demodulation frequency for use with a forward pointing antenna panel and relating to a first speed of an HST, for the forward pointing antenna panel;

determining a second Doppler-compensated demodulation frequency for use with a backwards pointing antenna panel and relating to a second speed of an HST for the backwards pointing antenna panel;

responsive to switching to the forward pointing panel, switching to the first Doppler-compensated demodulation frequency in transmitting and receiving wireless communications in the bi-directional HST network; and

responsive to switching to the backward pointing panel, switching to the second Doppler-compensated demodulation frequency in transmitting and receiving wireless communications in the bi-directional HST network.

19 . The method of claim 18 , further comprising:

determining that the UE is in a bi-directional HST network.

20 . The method of claim 18 wherein maintaining the first Doppler-compensated demodulation frequency comprises using signals only received with the forward pointing antenna panel to maintain the first Doppler-compensated demodulation frequency.

21 . The method of claim 18 wherein maintaining the second Doppler-compensated demodulation frequency comprises using signals only received with the backward pointing antenna panel to maintain the second Doppler-compensated demodulation frequency.

22 . A method performed by a user equipment (UE) in a bi-directional high speed train (HST) network having a track covered by a plurality of beams for wireless communications, the method comprising:

receiving a configuration having timing advance values associated with the plurality of beams;

setting the timing advance to the timing advance value associated with a first beam of the plurality of beams presently covering the UE; and

responsive to the UE transitioning from the first beam to a second beam during movement of the HST, setting the timing advance to the timing advance value associated with the second beam.