Method and apparatus for improving msg3 transmission of random access procedure in a wireless communication system

Abstract

A method and apparatus are disclosed, from the perspective of the UE, for performing random access procedure. In one embodiment, the method includes the UE receiving a message from a network. The message includes a TTI information of Msg3. In addition, the method includes the UE transmitting a preamble to the network. The method also includes the UE receiving a Msg2 from the network for responding the preamble. The method further includes the UE performing a Msg3 transmission to the network according to the TTI information of Msg3.

1 . A method of a UE (User Equipment), comprising:
 the UE receives a Msg2 containing a TTI (Transmission Timer Interval) information of a Msg3, associated with uplink, from a network, wherein the TTI information includes a TTI duration of the Msg3, associated with uplink, and a start timing offset of the Msg3, associated with uplink.   
     
     
         2 . The method of  claim 1 , further comprising:
 the UE selects the TTI information of the Msg3, from among multiple TTI information of the Msg3, based on random access purpose.   
     
     
         3 . The method of  claim 1 , further comprising:
 the UE selects the TTI information of the Msg3, from among multiple TTI information of the Msg3, based on a PRACH (Physical Random Access Channel) resource set or a preamble set.   
     
     
         4 . The method of  claim 1 , further comprising:
 the UE selects the TTI information of the Msg3, from among multiple TTI information of the Msg3, based on highest priority of logical channel having data available for transmission.   
     
     
         5 . The method of  claim 1 , further comprising:
 the UE performs one or more transmissions according to the TTI information of the Msg3.   
     
     
         6 . The method of  claim 1 , wherein the TTI information of the Msg3 is included in a common field for multiple RARs in the Msg2. 
     
     
         7 . The method of  claim 1 , wherein the Msg2 is a random access response. 
     
     
         8 . A User Equipment (UE), comprising:
 a control circuit;   a processor installed in the control circuit; and   a memory installed in the control circuit and operatively coupled to the processor;   wherein the processor is configured to execute a program code stored in the memory to:
 receive a Msg2 containing a TTI (Transmission Time Interval) information of a Msg3, associated with uplink, from a network, wherein the TTI information includes a TTI duration of the Msg3, associated with uplink, and a start timing offset of the Msg3, associated with uplink. 
   
     
     
         9 . The UE of  claim 8 , wherein the processor is further configured to execute the program code stored in the memory to:
 select the TTI information of the Msg3, from among multiple TTI information of the Msg3, based on random access purpose.   
     
     
         10 . The UE of  claim 8 , wherein the processor is further configured to execute the program code stored in the memory to:
 select the TTI information of the Msg3, from among multiple TTI information of the Msg3, based on a PRACH (Physical Random Access Channel) resource set o or a preamble set.   
     
     
         11 . The UE of  claim 8 , wherein the processor is further configured to execute the program code stored in the memory to:
 select the TTI information of the Msg3, from among multiple TTI information of the Msg3, based on highest priority of logical channel having available data.   
     
     
         12 . The UE of  claim 8 , wherein the processor is further configured to execute the program code stored in the memory to:
 perform one or more transmissions according to the TTI information of the Msg3.   
     
     
         13 . The UE of  claim 8 , wherein the TTI information of the Msg3 is included in a common field for multiple RARs in the Msg2. 
     
     
         14 . The UE of  claim 8 , wherein the Msg2 is a random access response. 
     
     
         15 . A non-transitory computer-readable medium comprising processor-executable instructions that, when executed by a UE (User Equipment), cause performance of operations, the operations comprising:
 receiving a Msg2 containing a TTI (Transmission Timer Interval) information of a Msg3, associated with uplink, from a network, wherein the TTI information includes a TTI duration of the Msg3, associated with uplink, and a start timing offset of the Msg3, associated with uplink.   
     
     
         16 . The non-transitory computer-readable medium of  claim 15 , the operations further comprising:
 performing one or more transmissions according to the TTI information of the Msg3.   
     
     
         17 . The non-transitory computer-readable medium of  claim 15 , wherein the TTI information of the Msg3 is included in a common field for multiple RARs in the Msg2. 
     
     
         18 . The non-transitory computer-readable medium of  claim 15 , wherein the Msg2 is a random access response. 
     
     
         19 . The non-transitory computer-readable medium of  claim 15 , the operations further comprising:
 selecting the TTI information of the Msg3, from among multiple TTI information of the Msg3, based on random access purpose.   
     
     
         20 . The non-transitory computer-readable medium of  claim 15 , the operations further comprising:
 selecting the TTI information of the Msg3, from among multiple TTI information of the Msg3, based on a PRACH (Physical Random Access Channel) resource set or a preamble set.