Uplink grant allocation for RACH-less lower layer mobility
An apparatus configured to: receive, from a source cell, a physical downlink control channel order, wherein the physical downlink control channel order comprises, at least, an indication of a target cell; transmit, to the target cell, a random access channel signaling; receive an indication of an uplink grant and an indication of a timer value associated with the uplink grant; and receive, from the source cell, an indication to perform cell change to the target cell.
1 . An apparatus comprising:
at least one processor; and
at least one memory storing instructions that, when executed with the at least one processor, cause the apparatus at least to:
receive, from a source cell, a physical downlink control channel order, wherein the physical downlink control channel order comprises, at least, an indication of a target cell;
transmit, to the target cell, a random access channel signaling;
receive an indication of an uplink grant and an indication of a timer value associated with the uplink grant, wherein the indication of the uplink grant and the indication of the timer value are received via a random access response to the random access channel signaling;
receive, from the source cell, an indication to perform cell change to the target cell;
transmit, to the source cell, an indication of a capability of the apparatus to maintain at least one timer for a plurality of candidate target cells associated with the uplink grant;
receive the random access response to the random access channel signaling, wherein the random access response comprises, at least, the indication of the uplink grant and the indication of the timer value, wherein the random access response further comprises a timing advance value for the target cell;
start a validity timer for the uplink grant based, at least partially, on the timer value, wherein the validity timer is started at a time determined based, at least partially, on receiving the random access response;
in response to the indication to perform cell change to the target cell, determine whether the uplink grant is valid based, at least partially, on the validity timer;
stop the validity timer in response to:
the received indication to perform cell change to the target cell, and
a determined change in a radio condition with respect to the target cell;
perform cell change to the target cell,
wherein the determined change in the radio condition comprises a quality of a synchronization signal block associated with the target cell being below a threshold; and
maintain the validity timer, maintain the uplink grant, and maintain a synchronization signal block associated with the uplink grant, after the cell change to the target cell, wherein the uplink grant is associated with a quasi co-location reference corresponding to a beam used for the random access channel signaling.