Conditional handover management

Abstract

A user device (UE) receives, from a source base station while the user device is operating in a source cell of the source base station, a conditional handover configuration providing information for user device operation within a candidate target cell of a candidate base station, and a corresponding condition for handing over to the candidate target cell of the candidate base station (1202). In some implementations, prior to determining that the condition is satisfied, the UE receives, from the source base station, a handover command message for immediate handover to a target base station (1204), and after receiving the handover command message, releases the conditional handover configuration (1206) and performs an immediate handover to the target base station (1208).

What is claimed is: 
     
         1 . A method, in a user device, comprising:
 receiving, by processing hardware of the user device and from a source base station while the user device is operating in a source cell of the source base station, a conditional handover configuration providing information for user device operation within a candidate target cell of a candidate base station, and a corresponding condition for handing over to the candidate target cell of the candidate base station;   prior to determining that the condition is satisfied, receiving, by the processing hardware and from the source base station, a handover command message for immediate handover to a target base station; and   after receiving the handover command message,
 releasing, by the processing hardware, the conditional handover configuration, and 
 performing an immediate handover to the target base station. 
   
     
     
         2 . The method of  claim 1 , wherein performing the immediate handover to the target base station includes performing a random access procedure with the target base station, and wherein releasing the conditional handover configuration comprises releasing the conditional handover configuration after performing the random access procedure. 
     
     
         3 . The method of  claim 1 , wherein releasing the conditional handover configuration comprises releasing the conditional handover configuration in response to the handover command message. 
     
     
         4 . The method of  claim 3 , wherein the handover command message includes an indication to release the conditional handover configuration, and wherein releasing the conditional handover configuration in response to receiving the handover command message comprises releasing the conditional handover configuration in response to the indication included in the handover command message. 
     
     
         5 . The method of  claim 1 , wherein receiving the conditional handover configuration and the corresponding condition includes receiving an RRC container message that includes (i) an RRC reconfiguration that includes the conditional handover configuration and (ii) the corresponding condition. 
     
     
         6 . A method, in a user device, comprising:
 receiving, from a source base station and while the user device is operating in a source cell of the source base station, a first conditional handover configuration providing information for user device operation within a first candidate target cell of a first candidate base station;   monitoring, by processing hardware of the user device, whether a first condition associated with a conditional handover to the first candidate target cell is satisfied;   receiving, from the source base station and while the user device is operating in the source cell, a second conditional handover configuration providing information for user device operation within a second candidate target cell covered by a second candidate base station;   monitoring, by the processing hardware, whether a second condition associated with a conditional handover to the second candidate target cell is satisfied;   determining, by the processing hardware and while monitoring whether the first and second conditions are satisfied, that the first condition is satisfied; and   in response to determining that the first condition is satisfied, performing a handover to the first candidate target cell, and releasing, by the processing hardware, the second conditional handover configuration.   
     
     
         7 . The method of  claim 6 , further comprising:
 after performing the handover to the first candidate target cell, determining, by the processing hardware, that the first conditional handover configuration is no longer valid.   
     
     
         8 . The method of  claim 6 , wherein releasing the second conditional handover configuration further comprises releasing all conditional handover configurations, other than the first conditional handover configuration, with which the user device was configured. 
     
     
         9 . A method, in a base station, comprising:
 sending, by processing hardware of the base station and to a user device while the user device is operating in a source cell of the base station, a conditional handover configuration providing information for user device operation within a candidate target cell of a candidate base station, and a corresponding condition for handing over to the candidate target cell of the candidate base station; and   causing, by the processing hardware, the user device to release the conditional handover configuration and perform an immediate handover to a target base station prior to the user device determining that the condition is satisfied, at least by sending, to the user device, a handover command message for immediate handover to the target base station.   
     
     
         10 . The method of  claim 9 , wherein causing the user device to perform the immediate handover to the target base station includes causing the user device to perform a random access procedure with the target base station, and wherein causing the user device to release the conditional handover configuration comprises causing the user device to release the conditional handover configuration after performing the random access procedure. 
     
     
         11 . The method of  claim 9 , wherein causing the user device to release the conditional handover configuration comprises causing the user device to release the conditional handover configuration in response to the handover command message. 
     
     
         12 . The method of  claim 11 , wherein the handover command message includes an indication to release the conditional handover configuration, and wherein causing the user device to release the conditional handover configuration in response to the handover command message comprises causing the user device to release the conditional handover configuration in response to the indication included in the handover command message. 
     
     
         13 . The method of  claim 9 , wherein sending the conditional handover configuration and the corresponding condition includes sending an RRC container message that includes (i) an RRC reconfiguration that includes the conditional handover configuration and (ii) the corresponding condition.