Method and apparatus for triggering power headroom report for beam operation in a wireless communication system

Abstract

Methods and apparatuses for triggering a power headroom report for beam operation in a wireless communication system are disclosed herein. In one method, a user equipment (UE) uses multiple beams for transmission. The UEtriggers a power headroom report due to a change of a pathloss being larger than a threshold, wherein the pathloss is associated with a specific beam or a set of beams.

What is claimed is: 
     
         1 . A method for a user equipment (UE) operation, the method comprising:
 using multiple beams for transmission; and   triggering, by the UE, a power headroom report due to a change of a pathloss being larger than a threshold, wherein the pathloss is associated with a specific beam, wherein the pathloss is derived from a synchronization signal,   wherein a UE transmission power for an uplink (UL) transmission by the UE is controlled per a set of the multiple beams.   
     
     
         2 . The method of  claim 1 , wherein the power headroom is the difference between a UE calculated transmission power for the set of the multiple UE beams and a maximum transmission power on the set of the multiple UE beams. 
     
     
         3 . The method of  claim 1 , wherein the specific beam is a specific UE beam or a specific transmission/reception point (TRP) beam. 
     
     
         4 . The method of  claim 1 , wherein the set of the multiple beams is a set of UE beams or a set of TRP beams. 
     
     
         5 . The method of  claim 1 , wherein the transmission power is controlled based on a power control command sent from a base station to the UE. 
     
     
         6 . The method of  claim 1 , wherein the power headroom report includes a power headroom for the specific beam or the set of the multiple beams. 
     
     
         7 . The method of  claim 1 , wherein the UE does not determine whether the pathloss has changed if a transmission associated with the specific beam is not scheduled. 
     
     
         8 . The method of  claim 1 , wherein the change of the pathloss is derived from a comparison between a current pathloss value, associated with the specific beam, and a previous pathloss value, associated with the specific beam. 
     
     
         9 . The method of  claim 1 , wherein the synchronization signal is measured on the specific beam. 
     
     
         10 . A User Equipment (UE), comprising:
 a control circuit;   a processor installed in the control circuit; and   a memory installed in the control circuit and coupled to the processor;   wherein the processor is configured to execute a program code stored in the memory to:
 use multiple beams for transmission; 
 trigger a power headroom report due to a change of a pathloss being larger than a threshold, wherein the pathloss is associated with a specific beam, wherein the pathloss is derived from a synchronization signal, 
 wherein a UE transmission power for a UL transmission by the UE is controlled per a set of the multiple beams. 
   
     
     
         11 . The UE of  claim 10 , wherein the specific beam is a specific UE beam or a specific transmission/reception point (TRP) beam. 
     
     
         12 . The UE of  claim 10 , wherein the set of the multiple beams is a set of UE beams or a set of TRP beams. 
     
     
         13 . The UE of  claim 10 , wherein the UE transmission power is controlled based on a power control command sent from a base station to the UE. 
     
     
         14 . The UE of  claim 10 , wherein the power headroom report includes a power headroom for the specific beam or the set of the multiple beams. 
     
     
         15 . The UE of  claim 10 , wherein the UE does not determine whether the pathloss has changed if a transmission associated with the specific beams is not scheduled. 
     
     
         16 . The UE of  claim 10 , wherein the change of the pathloss is derived from a comparison between a current pathloss value, associated with the specific beam, and a previous pathloss value, associated with the specific beam. 
     
     
         17 . The UE of  claim 10 , wherein the synchronization signal is measured on the specific beam. 
     
     
         18 . A method for operating a UE, the method comprising:
 using multiple beams for transmission;   triggering, by the UE, a power headroom report due to a change of a pathloss being larger than a threshold, wherein the change of the pathloss is derived from a comparison between a current pathloss value, associated with a first beam of the multiple beams, and a previous pathloss value, associated with the first beam, and wherein the pathloss is derived from a synchronization signal; and   receiving a power control command to control UE transmission power for the first beam and UE transmission power for a second beam of the multiple beams.   
     
     
         19 . The method of  claim 18 , wherein the first beam is a first UE beam and the second beam is a second UE beam, or the first beam is a first transmission/reception point (TRP) beam and the second beam is a second TRP beam. 
     
     
         20 . The method of  claim 18 , further comprising deriving the UE transmission power for the first beam based on the pathloss and the power control command.