Distributed unit, central unit, radio access network node, and method therefor

Abstract

A Distributed Unit (DU) (2) of a base station sends a first message to a Central Unit (1) of the base station in response to detecting initiation of a conditional mobility of a radio terminal (3) from a first cell served by the DU (2) to a second cell. It is thus for example possible to allow a Central Unit (CU) to be aware of satisfaction of an execution condition of a conditional mobility (or initiation of the conditional mobility).

What is claimed is: 
     
         1 . A distributed unit of a base station, the distributed unit comprising:
 at least one memory; and   at least one processor coupled to the at least one memory and configured to send a first message to a central unit of the base station in response to detecting initiation of a conditional mobility of a radio terminal from a first cell served by the distributed unit to a second cell.   
     
     
         2 . The distributed unit according to  claim 1 , wherein the at least one processor is configured to:
 determine whether a planned mobility of the radio terminal is the conditional mobility; and   if the planned mobility is the conditional mobility, delay the transmission of the first message to the central unit as compared to a case where the planned mobility is not the conditional mobility.   
     
     
         3 . The distributed unit according to  claim 1 , wherein the first message is sent during a signaling procedure for changing a context regarding the radio terminal. 
     
     
         4 . The distributed unit according to  claim 3 , wherein
 the signaling procedure is a UE Context Modification procedure, and   the first message is a UE CONTEXT MODIFICATION RESPONSE message.   
     
     
         5 . The distributed unit according to  claim 1  wherein the first message is sent to the central unit to indicate downlink data that is not yet transmitted to the radio terminal. 
     
     
         6 . The distributed unit according to  claim 5 , wherein the first message is a DOWNLINK DATA DELIVERY STATUS frame. 
     
     
         7 . The distributed unit according to  claim 1  wherein the at least one processor is configured to detect the initiation of the conditional handover by receiving a report that is transmitted from the radio terminal in response to satisfaction of an initiation condition of the conditional mobility. 
     
     
         8 . The distributed unit according to  claim 1  wherein the at least one processor is configured to detect the initiation of the conditional handover by autonomously determining satisfaction of an initiation condition of the conditional mobility. 
     
     
         9 . The distributed unit according to  claim 8 , wherein the at least one processor is configured to transmit a conditional mobility initiation command to the radio terminal in response to the satisfaction of the initiation condition of the conditional mobility. 
     
     
         10 . The distributed unit according to  claim 9 , wherein the at least one processor is configured to send to the central unit a configuration for the conditional mobility initiation command, prior to the transmission of the conditional mobility initiation command. 
     
     
         11 . The distributed unit according to  claim 1  wherein the second cell is served by the distributed unit, another distributed unit of the base station, or another base station different from the base station. 
     
     
         12 . A method for a distributed unit of a base station, the method comprising: sending a first message to a central unit of the base station in response to detecting initiation of a conditional mobility of a radio terminal from a first cell served by the distributed unit to a second cell. 
     
     
         13 . The method according to  claim 12 , further comprising:
 determining whether a planned mobility of the radio terminal is the conditional mobility; and   if the planned mobility is the conditional mobility, delaying the transmission of the first message to the central unit as compared to a case where the planned mobility is not the conditional mobility.   
     
     
         14 . The method according to  claim 12 , wherein the first message is sent during a signaling procedure for changing a context regarding the radio terminal. 
     
     
         15 . The method according to  claim 14 , wherein
 the signaling procedure is a UE Context Modification procedure, and   the first message is a UE CONTEXT MODIFICATION RESPONSE message.   
     
     
         16 . The method according to  claim 12 , wherein the first message is sent to the central unit to indicate downlink data that is not yet transmitted to the radio terminal. 
     
     
         17 . The method according to  claim 16 , wherein the first message is a DOWNLINK DATA DELIVERY STATUS frame. 
     
     
         18 .- 20 . (canceled) 
     
     
         21 . A central unit of a base station, the distributed unit comprising:
 at least one memory; and   at least one processor coupled to the at least one memory and configured to:
 control a conditional mobility of a radio terminal from a first cell served by the distributed unit to a second cell; and 
 receive from the distributed unit a first message which the distributed unit sends in response to detecting initiation of the conditional mobility. 
   
     
     
         22 . The central unit according to  claim 21 , wherein the at least one processor is configured to send, to the distributed unit, information explicitly or implicitly indicating whether a planned mobility of the radio terminal is the conditional mobility. 
     
     
         23 . The central unit according to  claim 21  wherein the at least one processor is configured to know that the conditional mobility of the mobile terminal has been initiated by receiving the first message. 
     
     
         24 .- 36 . (canceled)