Triggering timing synchronization in non-terrestrial networks
Methods and apparatuses for a timing advance report an NTN is provided. The method of UE comprises: receiving, from a BS, first information including satellite assistance information for a target satellite; receiving, from the BS, second information including timing information, wherein the timing information includes at least one of a start time and a time duration for a synchronization operation; determining whether a RACH-less synchronization operation is configured; and initiating, based on the satellite assistance information and the timing information, the synchronization operation by performing a RA procedure upon a determination that the RACH-less synchronization operation is not configured.
1 . A user equipment (UE) comprising:
a transceiver configured to:
receive, from a base station (BS), first information including satellite assistance information for a target satellite, and
receive, from the BS, second information including timing information, wherein the timing information includes at least one of a start time and a time duration for a synchronization operation; and
a processor operably coupled to the transceiver, the processor configured to:
determine whether a random access channel-less (RACH-less) synchronization operation is configured, and
initiate, based on the satellite assistance information and the timing information, the synchronization operation by performing a random access (RA) procedure upon a determination that the RACH-less synchronization operation is not configured.
2 . The UE of claim 1 , wherein:
the transceiver is further configured to receive third information including RACH-less synchronization information that comprises a timing advance (TA) parameter;
the processor is further configured to initiate, based on the RACH-less synchronization information, the synchronization operation by performing the RACH-less synchronization operation using the TA parameter;
the satellite assistance information includes at least one of ephemeris information, common TA parameters, an offset parameter, an epoch time, and a validity duration; and
the first, second, and third information is received via system information or a UE-dedicated radio resource control (RRC) message.
3 . The UE of claim 1 , wherein the transceiver is further configured to:
receive an UL grant; and
perform a first UL transmission after the RACH-less synchronization operation to the target satellite using the UL grant.
4 . The UE of claim 1 , wherein:
the transceiver is further configured to receive a network (NW) trigger indication for the synchronization operation; and
the NW trigger indication is identified as:
an intra-cell handover command via an RRC signaling,
an indication in downlink control information (DCI) included in a physical downlink control channel (PDCCH), or
a medium access control control element (MAC CE) including a configuration identification (ID) of a target satellite.
5 . The UE of claim 1 , wherein:
the processor is further configured to start or restart a validity timer for the target satellite when initiating a UL synchronization operation; and
the transceiver is further configured to transmit a timing advance (TA) report medium access control control element (MAC CE) for the target satellite in at least one of:
a message 3 (Msg3) or a message A (MsgA) transmitted in the RA procedure,
a first UL transmission after the RA procedure, or
the first UL transmission without a RACH.
6 . The UE of claim 1 , wherein:
the processor is further configured to:
start a timer when the UE receives a network (NW) trigger indication, or
start the timer based on the start time; and
the processor is further configured to set a timer duration of the timer as the time duration.
7 . The UE of claim 6 , wherein the processor is further configured to:
stop the timer when the RA procedure is completed or the RACH-less synchronization operation is completed; and
when the timer expires, perform the RA procedure to a serving cell based on the satellite assistance information for the target satellite or perform a radio resource control (RRC) re-establishment procedure.
8 . The UE of claim 1 , wherein:
the transceiver is further configured to receive, from the BS, a timing advance (TA) report request that is identified as:
an intra-cell handover command via an RRC signaling; or
a request indication in downlink control information (DCI) included in a physical downlink control channel (PDCCH) associated with a RACH;
the processor is further configured to perform the RA and generate a TA report medium access control control element (MAC CE); and
the transceiver is further configured to transmit, to the BS, the TA report MAC CE included in at least one of a message 3 (Msg3), a message A (MsgA), and a message after the RA procedure.
9 . The UE of claim 1 , wherein:
the transceiver is further configured to receive, from the BS, a timing advance (TA) report request that is identified as:
a medium access control control element (MAC CE) including at least one of a periodic TA report request, an aperiodic TA report request, and a semi-persistent TA report request;
a request indication included in a radio resource control (RRC) message, the RRC message being a UE information request message, or
an RRC reconfiguration message including a TA measurement configuration and a TA report configuration, the TA report configuration indicating at least one of the periodic TA report request, the aperiodic TA report request, and the semi-persistent TA report request;
the processor is further configured to generate the TA report; and
the transceiver is further configured to transmit, to the BS, the TA report in an RRC message or in a MAC CE included in a UL message.
10 . A method of a user equipment (UE), the method comprising:
receiving, from a base station (BS), first information including satellite assistance information for a target satellite;
receiving, from the BS, second information including timing information, wherein the timing information includes at least one of a start time and a time duration for a synchronization operation;
determining whether a random access channel-less (RACH-less) synchronization operation is configured; and
initiating, based on the satellite assistance information and the timing information, the synchronization operation by performing a random access (RA) procedure upon a determination that the RACH-less synchronization operation is not configured.
11 . The method of claim 10 , further comprising:
receiving third information including RACH-less synchronization information that comprises a timing advance (TA) parameter; and
initiating, based on the RACH-less synchronization information, the synchronization operation by performing the RACH-less synchronization operation using the TA parameter,
wherein:
the satellite assistance information includes at least one of ephemeris information, common TA parameters, an offset parameter, an epoch time, and a validity duration, and
the first, second, and third information is received via system information or a UE-dedicated radio resource control (RRC) message.
12 . The method of claim 10 , further comprising:
receiving an UL grant; and
performing a first UL transmission after the RACH-less synchronization operation to the target satellite using the UL grant.
13 . The method of claim 10 , further comprising receiving a network (NW) trigger indication for the synchronization operation,
wherein the NW trigger indication is identified as:
an intra-cell handover command via an RRC signaling;
an indication in downlink control information (DCI) included in a physical downlink control channel (PDCCH); or
a medium access control control element (MAC CE) including a configuration identification (ID) of a target satellite.
14 . The method of claim 10 , further comprising:
starting or restarting a validity timer for the target satellite when initiating a UL synchronization operation; and
transmitting a timing advance (TA) report medium access control control element (MAC CE) for the target satellite in at least one of:
a message 3 (Msg3) or a message A (MsgA) transmitted in the RA procedure,
a first UL transmission after the RA procedure, or
the first UL transmission without a RACH.
15 . The method of claim 10 , further comprising:
starting a timer when the UE receives a NW trigger indication, or
starting the timer based on the start time; and
setting a timer duration of the timer as the time duration.
16 . The method of claim 15 , further comprising:
stopping the timer when the RA procedure is completed or the RACH-less synchronization operation is completed; and
when the timer expires, performing the RA procedure to a serving cell based on the satellite assistance information for the target satellite or perform a radio resource control (RRC) re-establishment procedure.
17 . The method of claim 10 , further comprising:
receiving, from the BS, a timing advance (TA) report request that is identified as:
an intra-cell handover command via an RRC signaling, or
a request indication in downlink control information (DCI) included in a physical downlink control channel (PDCCH) associated with a RACH;
performing the RA and generate a TA report medium access control control element (MAC CE); and
transmitting, to the BS, the TA report MAC CE included in at least one of a message 3 (Msg3), a message A (MsgA), and a message after the RA procedure.
18 . The method of claim 10 , further comprising:
receiving, from the BS, a timing advance (TA) report request that is identified as:
a medium access control control element (MAC CE) including at least one of a periodic TA report request, an aperiodic TA report request, and a semi-persistent TA report request,
a request indication included in a radio resource control (RRC) message, the RRC message being a UE information request message, or
an RRC reconfiguration message including a TA measurement configuration and a TA report configuration, the TA report configuration indicating at least one of the periodic TA report request, the aperiodic TA report request, and the semi-persistent TA report request;
generating the TA report; and
transmitting, to the BS, the TA report in an RRC message or in a MAC CE included in a UL message.
19 . A base station (BS) comprising:
a processor; and
a transceiver operably coupled to the processor, the transceiver configured to:
transmit, to a user equipment (UE), first information including satellite assistance information for a target satellite, and
transmit, to the UE, second information including timing information, wherein the timing information includes at least one of a start time and a time duration for a synchronization operation,
transmit, to the UE, a third information indicating whether random access channel-less (RACH-less) synchronization operation is configured,
wherein:
when the indication indicates that the RACH-less synchronization operation is not configured, the synchronization operation is initiated based on the satellite assistance information and the timing information.
20 . The BS of claim 19 , wherein:
the third information includes RACH-less synchronization information that comprises a timing advance (TA) parameter; and
the transceiver is further configured to:
transmit an UL grant;
transmit a network (NW) trigger indication for the synchronization operation, the NW trigger indication being identified as:
an intra-cell handover command via an RRC signaling,
an indication in downlink control information (DCI) included in a physical downlink control channel (PDCCH), or
a medium access control control element (MAC CE) including a configuration identification (ID) of a target satellite;
transmit, to the UE, a TA report request; and
receive, from the UE, a TA report MAC CE for the target satellite.