User equipment handover from a network energy saving cell
Various aspects of the present disclosure relate to user equipment (UE) handover from a network energy saving cell. A timeline of different events allows the UE to make a reliable decision on executing a handover to a target cell, e.g., by providing the UE with the knowledge that there is a finite time before the source cell sleeps and therefore measurement or evaluation to find a target cell for handover may continue. For example, a remaining time to sleep (RTS) value may be defined that indicates an amount of time that the source cell remains active after sending a cell switch off indication to the UE. The source cell enters sleep only after the RTS time indicated in the cell switch off indication elapses. The UE remains active in the source cell until the RTS time elapses and performs measurement and measurement evaluation of candidates.
1 . A user equipment (UE) for wireless communication, comprising:
at least one memory; and
at least one processor coupled with the at least one memory and configured to cause the UE to:
receive, from a network entity, a first signaling indicating a conditional handover configuration that includes one or more handover conditions for one or more candidate cells, a first timer value, and a second timer value;
start a first timer with the first timer value in response to determining that the one or more handover conditions indicated in the first signaling are fulfilled for a candidate cell of the one or more candidate cells;
receive, from the network entity, a second signaling before expiry of the first timer; and
in response to the second signaling, execute handover to the candidate cell, stop the first timer, and start a second timer with the second timer value.
2 . The UE of claim 1 , wherein the at least one processor is configured to cause the UE to restart measuring and evaluating handover conditions for the candidate cell upon expiry of the first timer.
3 . The UE of claim 1 , wherein the first signaling includes a radio resource control (RRC) connection reconfiguration message for the one or more candidate cells.
4 . The UE of claim 1 , wherein the second signaling comprises a layer 1 signaling.
5 . The UE of claim 1 , wherein the one or more handover conditions include one or more measurement events and based on at least one of radio condition evaluation, time condition evaluation, or location condition evaluation.
6 . The UE of claim 1 , wherein the candidate cell comprises a target cell in response to determining that the one or more handover conditions indicated in the first signaling are fulfilled for the candidate cell.
7 . The UE of claim 6 , wherein to execute the handover execution is to tune to a frequency of the target cell, synchronize to a downlink channel of the target cell, and initiate a random access channel (RACH) procedure to announce arrival of the UE to the target cell.
8 . A user equipment (UE) for wireless communication, comprising:
at least one memory; and
at least one processor coupled with the at least one memory and configured to cause the UE to:
receive, from a network entity (NE), a first signaling indicating a conditional handover configuration that includes one or more handover conditions for one or more candidate cells;
receive, from the NE, a second signaling indicating start of a sleep time of the NE; and
execute handover to a candidate cell of the one or more candidate cells after receipt of the second signaling and in response to determining that the one or more handover conditions indicated in the first signaling are fulfilled for the candidate cell.
9 . The UE of claim 8 , wherein to execute handover to the candidate cell is to execute handover to the candidate cell after receipt of the second signaling, prior to expiration of a remaining time to sleep (RTS) value, and in response to determining that the one or more handover conditions indicated in the first signaling are fulfilled for the candidate cell.
10 . The UE of claim 9 , wherein the second signaling includes the RTS value.
11 . The UE of claim 9 , wherein the first signaling includes the RTS value.
12 . The UE of claim 9 , wherein the at least one processor is configured to cause the UE to:
receive, from the NE, a discontinuous transmission (DTX) or discontinuous reception (DRX) configuration; and
determine the RTS value based at least in part on the discontinuous transmission (DTX) or discontinuous reception (DRX) configuration.
13 . The UE of claim 9 , wherein the at least one processor is configured to cause the UE to:
receive, from the NE, a downlink control information (DCI) configuration; and
determine the RTS value based at least in part on the DCI configuration.
14 . The UE of claim 8 , wherein the one or more handover conditions include one or more measurement events and based on at least one of radio condition evaluation, time condition evaluation, or location condition evaluation.
15 . The UE of claim 8 , wherein the candidate cell comprises a target cell in response to determining that the one or more conditions indicated in the first signaling are fulfilled for the candidate cell.
16 . The UE of claim 15 , wherein to execute the handover execution is to tune to a frequency of the target cell, synchronize to a downlink channel of the target cell, and initiate a random access channel (RACH) procedure to announce arrival of the UE to the target cell.
17 . A base station for wireless communication, comprising:
at least one memory; and
at least one processor coupled with the at least one memory and configured to cause the base station to:
transmit, to a user equipment (UE), a first signaling indicating a conditional handover configuration that includes one or more handover conditions for one or more candidate cells; and
transmit, to the UE, a second signaling indicating start of a sleep time of the base station to cause the UE to execute handover to a candidate cell of the one or more candidate cells in response to determining that the one or more handover conditions indicated in the first signaling are fulfilled for the candidate cell.
18 . The base station of claim 17 , wherein the one or more handover conditions include one or more measurement events and based on at least one of radio condition evaluation, time condition evaluation, or location condition evaluation.
19 . A processor for wireless communication, comprising:
at least one controller coupled with at least one memory and configured to cause the processor to:
receive, from a network entity, a first signaling indicating a conditional handover configuration that includes one or more handover conditions for one or more candidate cells, a first timer value, and a second timer value;
start a first timer with the first timer value in response to determining that the one or more handover conditions indicated in the first signaling are fulfilled for a first candidate cell of the one or more candidate cells;
receive, from the network entity, a second signaling before expiry of the first timer; and
in response to the second signaling, execute handover to the first candidate cell, stop the first timer, and start a second timer with the second timer value.
20 . The processor of claim 19 , wherein the at least one controller is configured to cause the processor to restart measuring and evaluating handover conditions for the first candidate cell upon expiry of the first timer.