TERMINAL DEVICE, BASE STATION DEVICE, METHOD, AND RECORDING MEDIUM
[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.