Conditional handover procedures

Abstract

A method of performing a conditional handover (CHO) procedure is described in some of the present embodiments. The method is performed by a user equipment (UE) and includes the following operations: receiving a plurality of CHO commands from a source base station, each CHO command having at least one triggering condition and corresponding to a target cell; determining whether one or more triggered cells exist by determining whether the at least one triggering condition for each CHO command in the plurality of CHO commands that corresponds to each of the one or more triggered cells is fulfilled; and after determining that the one or more triggered cells exist: selecting one of the one or more triggered cells, and performing a handover procedure to connect to the selected one of the one or more triggered cells.

What is claimed is: 
     
         1 . A method of performing a conditional handover (CHO) procedure by a user equipment (UE), the method comprising:
 receiving a plurality of CHO commands from a source base station, each CHO command having at least one triggering condition and corresponding to a target cell;   determining whether one or more triggered cells exist by determining whether the at least one triggering condition for each CHO command in the plurality of CHO commands that corresponds to each of the one or more triggered cells is fulfilled; and   after determining that the one or more triggered cells exist:
 selecting one of the one or more triggered cells, and 
 performing a handover procedure to connect to the selected one of the one or more triggered cells. 
   
     
     
         2 . The method of  claim 1 , wherein after determining that the one or more triggered cells exist, the method further comprises:
 releasing the plurality of CHO commands when the handover procedure is successfully performed.   
     
     
         3 . The method of  claim 1 , wherein each CHO command further comprises a CHO command priority. 
     
     
         4 . The method of  claim 1 , wherein the plurality of CHO commands have no priority or have a same priority. 
     
     
         5 . The method of  claim 2 , wherein releasing the plurality of CHO commands comprises releasing the at least one triggering condition associated with each CHO command. 
     
     
         6 . The method of  claim 2 , wherein each CHO command further has a target cell configuration of the corresponding target cell, and releasing the plurality of CHO commands comprises releasing the target cell configuration and one or more radio resources of each CHO command. 
     
     
         7 . The method of  claim 2 , wherein each CHO command further has a CHO command identifier (ID), and releasing the plurality of CHO commands comprises releasing the CHO command ID associated with each CHO command. 
     
     
         8 . A user equipment (UE), comprising:
 one or more non-transitory computer-readable media having computer-executable instructions embodied thereon; and   at least one processor coupled to the one or more non-transitory computer-readable media, and configured to execute the computer-executable instructions to cause the UE to:   receive a plurality of CHO commands from a source base station, each CHO command having at least one triggering condition and corresponding to a target cell;   determine whether one or more triggered cells exist by determining whether the at least one triggering condition for each CHO command in the plurality of CHO commands that corresponds to each of the one or more triggered cells is fulfilled; and   after determining that the one or more triggered cells exist:
 select one of the one or more triggered cells, and 
 perform a handover procedure to connect to the selected one of the one or more triggered cells. 
   
     
     
         9 . The UE of  claim 8 , wherein after determining that the one or more triggered cells exist, the at least one processor is further configured to execute the computer-executable instructions to cause the UE to:
 release the plurality of CHO commands when the handover procedure is successfully performed.   
     
     
         10 . The UE of  claim 8 , wherein each CHO command further comprises a CHO command priority. 
     
     
         11 . The UE of  claim 8 , wherein the plurality of CHO commands have no priority or have a same priority. 
     
     
         12 . The UE of  claim 9 , wherein releasing the plurality of CHO commands comprises releasing the at least one triggering condition associated with each CHO command. 
     
     
         13 . The UE of  claim 9 , wherein each CHO command further has a target cell configuration of the corresponding target cell, and releasing the plurality of CHO commands comprises releasing the target cell configuration and one or more radio resources of each CHO command. 
     
     
         14 . The UE of  claim 9 , wherein each CHO command further has a CHO command identifier (ID), and releasing the plurality of CHO commands comprises releasing the CHO command ID associated with each CHO command. 
     
     
         15 . A base station (BS) apparatus, comprising:
 one or more non-transitory computer-readable media having computer-executable instructions embodied thereon; and   at least one processor coupled to the one or more non-transitory computer-readable media, and configured to execute the computer-executable instructions to cause the BS apparatus to:   transmit a conditional handover (CHO) command to a user equipment (UE), the CHO command having a CHO command identifier (ID), a first target cell configuration and at least one triggering condition, the CHO command being transmitted such that the UE performs a handover procedure according to the CHO command to connect to a first target cell indicated in the CHO command in a case that the at least one triggering condition is fulfilled; and   transmit a conventional handover command to the UE after transmitting the CHO command, the conventional handover command having no triggering condition and indicating a second target cell,   wherein in a case that the at least one triggering condition is not fulfilled, the conventional handover command is transmitted such that:
 the UE performs a handover procedure according to the conventional handover command to connect to the second target cell indicated in the conventional handover command, and 
 the UE releases the CHO command when the handover procedure according to the conventional handover command is successfully performed, releasing the CHO command comprising releasing at least one of the first target cell configuration and one or more radio resources associated with the CHO command. 
   
     
     
         16 . The BS apparatus of  claim 15 , wherein in a case that the at least one triggering condition is not fulfilled, the at least one processor is further configured to execute the computer-executable instructions to cause the BS apparatus to:
 receive a CHO failure report from the UE.   
     
     
         17 . The BS apparatus of  claim 15 , wherein the CHO command comprises a CHO command priority. 
     
     
         18 . The BS apparatus of  claim 17 , wherein the CHO command priority is a default priority. 
     
     
         19 . The BS apparatus of  claim 15 , wherein releasing the CHO command further comprises releasing the CHO command ID associated with the CHO command. 
     
     
         20 . The BS apparatus of  claim 15 , wherein releasing the CHO command further comprises releasing the at least one triggering condition associated with the CHO command.