Terminal device, base station device, method, and recording medium

Abstract

[Problem] To propose a mechanism that makes it possible to achieve stability of a RACH procedure and reduction in latency of the RACH procedure at the same time. [Solution] A terminal device including a selector that selects, in a RACH procedure, whether to transmit a first uplink message or a second uplink message to a base station device, the first uplink message being an uplink message of a two-step RACH procedure, the second uplink message being an uplink message of a four-step RACH procedure.

1 . A terminal device comprising a selector that selects, in a RACH procedure, whether to transmit a first uplink message or a second uplink message to a base station device, the first uplink message being an uplink message of a two-step RACH procedure, the second uplink message being an uplink message of a four-step RACH procedure. 
     
     
         2 . The terminal device according to  claim 1 , wherein the selector selects whether to transmit the first uplink message or the second uplink message to the base station device, on a basis of an RRC state of the terminal device. 
     
     
         3 . The terminal device according to  claim 2 , wherein the selector selects the second uplink message in a case where the RRC state of the terminal device is an idle mode, and selects the first uplink message in a case were the RRC state of the terminal device is an inactive mode or a connected mode. 
     
     
         4 . The terminal device according to  claim 1 , wherein the selector first selects the first uplink message, and, in a case where the two-step RACH procedure is unsuccessful, selects the second up message. 
     
     
         5 . The terminal device according to  claim 4 , wherein the selector selects the second up message in a case where the two-step RACH procedure is unsuccessful even if a number of transmissions of the first uplink message exceeds a predetermined threshold. 
     
     
         6 . The terminal device according to  claim 4 , wherein the selector recognizes, as an unsuccess of the two-step RACH procedure, no reception of a first downlink message of the two-step RACH procedure corresponding to the first uplink message from the base station device. 
     
     
         7 . The terminal device according to  claim 4 , wherein the selector recognizes, as an unsuccess of the two-step RACH procedure, reception of information designating switching to the four-step RACH procedure from the base station device. 
     
     
         8 . The terminal device according to  claim 1 , wherein the selector selects whether to transmit the first uplink message or the second uplink message to the base station device, on a basis of a cell in which the RACH procedure is performed. 
     
     
         9 . The terminal device according to  claim 1 , wherein the selector selects whether to transmit the first uplink message or the second uplink message to the base station device, on a basis of a use to which the RACH procedure is applied. 
     
     
         10 . The terminal device according to  claim 1 , wherein the selector selects a format of the first uplink message. 
     
     
         11 . The terminal device according to  claim 1 , wherein information included in the first uplink message is different from information included in the second uplink message. 
     
     
         12 . The terminal device according to  claim 1 , wherein a format of the first uplink message is different from a format of the second uplink message. 
     
     
         13 . A base station device comprising
 a setting section that sets, in a terminal device, a first selection reference for the terminal device to select whether to transmit a first uplink message or a second uplink message in a RACH procedure, the first uplink message being an uplink message of a two-step RACH procedure, the second uplink message being an uplink message of a four-step RACH procedure.   
     
     
         14 . The base station device according to  claim 13 , wherein the setting section sets, in the terminal device, a second selection reference for the terminal device to select a format of the first uplink message. 
     
     
         15 . A method executed by a processor, the method comprising
 selecting, in a RACH procedure, whether to transmit a first uplink message or a second uplink message to a base station device, the first uplink message being an uplink message of a two-step RACH procedure, the second uplink message being an uplink message of a four-step RACH procedure.   
     
     
         16 . A method executed by a processor, the method comprising
 setting, in a terminal device, a first selection reference for the terminal device to select whether to transmit a first uplink message or a second uplink message in a RACH procedure, the first uplink message being an uplink message of a two-step RACH procedure, the second uplink message being an uplink message of a four-step RACH procedure.   
     
     
         17 . A recording medium having a program recorded thereon, the program causing a computer to function as a selector that selects, in a RACH procedure, whether to transmit a first uplink message or a second uplink message to a base station device, the first uplink message being an uplink message of a two-step RACH procedure, the second uplink message being an uplink message of a four-step RACH procedure. 
     
     
         18 . A recording medium having a program recorded thereon, the program causing a computer to function as a setting section that sets, in a terminal device, a first selection reference for the terminal device to select whether to transmit a first uplink message or a second uplink message in a RACH procedure, the first uplink message being an uplink message of a two-step RACH procedure, the second uplink message being an uplink message of a four-step RACH procedure.