Methods and systems for efficient uplink (UL) synchronization maintenance with a deactivated secondary cell group (SCG)
A wireless transmit/receive unit (WTRU) may receive indication information indicating an uplink (UL) configuration and one or more triggering conditions for transmission of UL signals. Based on reception of a deactivation command or fulfillment of a condition for WTRU-triggered deactivation of a secondary cell group (SCG), the WTRU may deactivate the SCG. Based on the UL configuration and the fulfillment of the one or more triggering conditions, the WTRU may transmit the UL signals via the SCG. The WTRU may receive, via a master cell group (MCG), an in-synch or out-of-synch indication for the SCG. Based on the reception of the out-of-synch indication including a timing advance (TA) delta value, the WTRU may update a UL TA towards the SCG based on the TA delta value. Using the updated UL TA towards the SCG, the WTRU may transmit one or more subsequent UL signals via the SCG.
1 . A method for use in a wireless transmit/receive unit (WTRU), the method comprising:
receiving, from a first node, indication information indicating an uplink (UL) configuration of one or more random access channel (RACH) preambles, including a power level for the one or more RACH preambles;
transmitting, to a second node, the one or more RACH preambles at the received power level for the one or more RACH preambles;
receiving, via the first node, a synchronization indication for the second node;
based on the reception of the synchronization indication for the second node, wherein the synchronization indication for the second node includes timing advance (TA) information, updating a UL TA towards the second node based on the TA information and restarting a time value associated with the second node; and
transmitting, using the updated UL TA towards the second node, one or more UL signals to the second node.
2 . The method of claim 1 , further comprising:
running a time value associated with the second node, including keeping running of the time value associated with the second node.
3 . The method of claim 1 , wherein the indication information further indicates one or more triggering conditions for transmission of the one or more RACH preambles, wherein the one or more triggering conditions for transmission of the one or more RACH preambles include timing information.
4 . The method of claim 3 , wherein the transmission of the one or more RACH preambles to the second node is based on the UL configuration and fulfillment of the one or more triggering conditions for transmission of the one or more RACH preambles.
5 . The method of claim 1 , wherein the TA information is a timing advance command (TAC) and includes a TA delta value.
6 . The method of claim 1 , wherein the synchronization indication is one of an in-synch indication or an out-of-synch indication.
7 . The method of claim 6 , further comprising:
based on reception of the in-synch indication, restarting running of a time value associated with the second node.
8 . The method of claim 7 , further comprising:
based on the time value associated with the second node, transmitting UL data via the second node without using a random access (RA) procedure.
9 . The method of claim 6 , further comprising:
based on reception of the out-of-synch indication for the second node, wherein the out-of-synch indication for the second node does not include a TA delta value, stopping running of a time value associated with the second node and considering the second node out of synchronization with the WTRU.
10 . A wireless transmit receive unit (WTRU) comprising:
a transceiver; and
a processor operatively coupled to the transceiver; wherein:
the transceiver is configured to receive, from a first node, indication information indicating an uplink (UL) configuration of one or more random access channel (RACH) preambles, including a power level for the one or more RACH preambles;
the processor and the transceiver are configured to transmit, to a second node, the one or more RACH preambles at the received power level for the one or more RACH preambles;
the transceiver is configured to receive, via the first node, a synchronization indication for the second node;
the processor and the transceiver are configured to, based on the reception of the synchronization indication for the second node, wherein the synchronization indication for the second node includes timing advance (TA) information, update a UL TA towards the second node based on the TA information and restart a time value associated with the second node; and
the processor and the transceiver are configured to transmit, using the updated UL TA towards the second node, one or more UL signals to the second node.
11 . The WTRU of claim 10 , wherein the processor is further configured to run a time value associated with the second node including keeping running of the time value associated with the second node.
12 . The WTRU of claim 10 , wherein the indication information further indicates one or more triggering conditions for transmission of the one or more RACH preambles, wherein the one or more triggering conditions for transmission of the one or more RACH preambles include timing information.
13 . The WTRU of claim 12 , wherein the transmission of the one or more RACH preambles to the second node is based on the UL configuration and fulfillment of the one or more triggering conditions for transmission of the one or more RACH preambles.
14 . The WTRU of claim 10 , wherein the TA information is a timing advance command (TAC) and includes a TA delta value.
15 . The WTRU of claim 10 , wherein the synchronization indication is one of an in-synch indication or an out-of-synch indication.
16 . The WTRU of claim 15 , wherein the processor and the transceiver are further configured to, based on reception of the in-synch indication, restart running of a time value associated with the second node.
17 . The WTRU of claim 16 , wherein the processor and the transceiver are further configured to, based on the time value associated with the second node, transmit UL data to the second node without using a random access (RA) procedure.
18 . The WTRU of claim 15 , wherein the processor and the transceiver are further configured to, based on reception of the out-of-synch indication for the second node, wherein the out-of-synch indication for the second node does not include a TA delta value, stop running of a time value associated with the second node and consider the second node out of synchronization with the WTRU.