Terminal apparatus, base station apparatus, control method, and computer-readable storage medium for executing random access procedure

1. A terminal apparatus that executes a two-step random access procedure or a four-step random access procedure to establish a connection with a base station apparatus, comprising:

one or more processors; and

one or more memories that stores computer-readable instruction for causing, when executed by the one or more processors, the terminal apparatus to:

transmit a first message of the two-step random access procedure including a preamble and predetermined information for connection establishment; and

transmit, in a case where a number of unsuccessful attempts to receive the first message by the base station apparatus exceeds a predetermined number, a second message to be transmitted from the terminal apparatus to the base station apparatus in the four-step random access procedure,

wherein communication between the base station apparatus and the terminal apparatus is performed using at least one of a plurality of bandwidth parts included in a usable frequency band,

the predetermined number is set for each one of the plurality of bandwidth parts, and

in a case where the number exceeds the predetermined number set for one bandwidth part used to transmit the first message from among the plurality of bandwidth parts, the terminal apparatus transmits the second message.

2. The terminal apparatus according to claim 1 , wherein

the predetermined number is a maximum number of transmission attempts of a random access preamble in a four-step random access procedure.

3. The terminal apparatus according to claim 1 , wherein

the predetermined number is a number different from a maximum number of transmission attempts of a random access preamble in a four-step random access procedure.

4. The terminal apparatus according to claim 1 , wherein

the terminal apparatus transmits the second message in response to receiving an instruction transmitted from the base station apparatus in response to the number exceeding the predetermined number.

5. The terminal apparatus according to claim 1 , wherein

the second message is a preamble transmitted via the first message.

6. The terminal apparatus according to claim 1 , wherein

the second message is a preamble different from a preamble transmitted via the first message.

7. The terminal apparatus according to claim 4 , wherein

the second message is a message transmitted after a random access response in the four-step random access procedure.

8. The terminal apparatus according to claim 4 , wherein

the instruction is included in a reply message to the first message in the two-step random access procedure.

9. The terminal apparatus according to claim 8 , wherein

the instruction is reported to the terminal apparatus by using first identification information in transmission of a first portion of the reply message; and

the first identification information is different from second identification information used in transmission of the first portion via the reply message in a case where the first message is successfully received.

10. The terminal apparatus according to claim 8 , wherein

the instruction is reported to the terminal apparatus by transmitting first information via a second portion of the reply message; and

the first information is different from second information transmitted via the second portion via the reply message in a case where the first message is successfully received.

11. The terminal apparatus according to claim 10 , wherein

the first information is information corresponding a random access response in the four-step random access procedure.

12. A base station apparatus, comprising:

one or more processors; and

one or more memories that stores computer-readable instruction for causing, when executed by the one or more processors, the base station apparatus to report a predetermined number to a terminal apparatus such that the terminal apparatus transmits, in a case where the number of unsuccessful attempts to receive a first message transmitted from the terminal apparatus including a preamble and predetermined information for connection establishment of a two-step random access procedure exceeds a predetermined number, a second message to be transmitted in a four-step random access procedure,

wherein communication between the base station apparatus and the terminal apparatus is performed using at least one of a plurality of bandwidth parts included in a usable frequency band,

the predetermined number is set for each one of the plurality of bandwidth parts, and

in a case where the number exceeds the predetermined number set for one bandwidth part used to transmit the first message from among the plurality of bandwidth parts, the terminal apparatus transmits the second message.

13. The base station apparatus according to claim 12 , wherein

the second message is a random access preamble in the four-step random access procedure.

14. The base station apparatus according to claim 12 , wherein

in a case where, for the first message, the preamble is detected but a number of unsuccessful attempts to receive the predetermined information exceeds the predetermined number, the base station apparatus transmits to the terminal apparatus a message instructing the terminal apparatus to transmit the second message.

15. The base station apparatus according to claim 14 , wherein

the second message is a message transmitted after a random access response in the four-step random access procedure.

16. A control method executed by a terminal apparatus capable of executing a two-step random access procedure or a four-step random access procedure to establish a connection with a base station apparatus, the control method comprising:

transmitting a first message of the two-step random access procedure including a preamble and predetermined information for connection establishment; and

transmitting, in a case where a number of unsuccessful attempts to receive the first message by the base station apparatus exceeds a predetermined number, a second message to be transmitted from the terminal apparatus to the base station apparatus in the four-step random access procedure;

wherein communication between the base station apparatus and the terminal apparatus is performed using at least one of a plurality of bandwidth parts included in a usable frequency band,

the predetermined number is set for each one of the plurality of bandwidth parts, and

in a case where the number exceeds the predetermined number set for one bandwidth part used to transmit the first message from among the plurality of bandwidth parts, the terminal apparatus transmits the second message.

17. A non-transitory computer-readable storage medium that stores a program for causing a computer, provided in a terminal apparatus capable of executing a two-step random access procedure or a four-step random access procedure to establish a connection with a base station apparatus, comprising:

transmitting a first message of the two-step random access procedure including a preamble and predetermined information for connection establishment and

transmitting in a case where a number of unsuccessful attempts to receive the first message by the base station apparatus exceeds a predetermined number, a second message to be transmitted from the terminal apparatus to the base station apparatus in the four-step random access procedure,

wherein communication between the base station apparatus and the terminal apparatus is performed using at least one of a plurality of bandwidth parts included in a usable frequency band,

the predetermined number is set for each one of the plurality of bandwidth parts, and

in a case where the number exceeds the predetermined number set for one bandwidth part used to transmit the first message from among the plurality of bandwidth parts, the terminal apparatus transmits the second message.