Granted Patent B2

US 12,262,421 · App. 18/625,422 · Granted Mar 25, 2025

Inventor: Hisashi Futaki (Tokyo, JP)

Assignee: NEC CORPORATION

H04W74/0833

Abstract

Claims (84)

1. A method performed by a User Equipment (UE), the method comprising:

receiving, from a communication apparatus, information indicating a maximum number of preamble transmissions of a 2-step Contention Based Random Access (CBRA);

transmitting a first message of the 2-step CBRA to the communication apparatus;

receiving a second message of the 2-step CBRA from the communication apparatus,

wherein the second message includes:

a Medium Access Control (MAC) subheader associated with a fallback, and

an uplink grant indicating an uplink resource used for transmission of a third message of a 4-step CBRA;

transmitting, to the communication apparatus, the third message of the 4-step CBRA based on the uplink grant in a case where the UE receives the second message;

falling back to the 4-step CBRA after a number of preamble transmissions of the 2-step CBRA reaches the maximum number of preamble transmissions of the 2-step CBRA; and

keeping a counter for counting the number of preamble transmissions in a case of the falling back to the 4-step CBRA.

2. The method according to claim 1 , further comprising:

in a case where a preamble identifier included in a Random Access Preamble Identifier (RAPID) field of the second message of the 2-step CBRA matches an index of a preamble transmitted in the first message of the 2-step CBRA, considering that the second message of the 2-step CBRA has been successfully received.

3. The method according to claim 1 , further comprising:

in a case where a window regarding a random access response expires and a preamble identifier included in a Random Access Preamble Identifier (RAPID) field of the second message of the 2-step CBRA does not match an index of a preamble transmitted in the first message of the 2-step CBRA, performing transmission of the first message of the 2-step CBRA.

4. The method according to claim 1 , further comprising:

receiving a Physical Downlink Control Channel (PDCCH) addressed to a Temporary Cell Radio Network Temporary Identifier (C-RNTI) in the second message;

considering that contention resolution is unsuccessful in a case where a Medium Access Control Protocol Data Unit (MAC PDU) of a fourth message of the 4-step CBRA has been successfully decoded but a UE Contention Resolution Identity MAC Control Element (CE) included in the MAC PDU of the fourth message does not match a Common Control Channel Service Data Unit (CCCH SDU) transmitted in the third message of the 4-step CBRA; and

selecting which one of the 2-step CBRA and the 4-step CBRA is used to restart a random access, based on a count value of a PREAMBLE_TRANSMISSION_COUNTER that is used to count a number of preamble transmissions of the 2-step CBRA.

5. The method according to claim 4 ,

wherein the counter is

PREAMBLE_TRANSMISSION_COUNTER, and

wherein the information is received by a Radio Resource Control (RRC) message.

6. The method according to claim 1 ,

wherein the information indicates a maximum number of preamble transmissions of the 4-step CBRA.

7. The method according to claim 1 ,

wherein the first message of the 2-step CBRA is transmitted in a cell of the communication apparatus,

wherein the second message of the 2-step CBRA is received in the cell, and

wherein the falling back to the 4-step CBRA after the number of preamble transmissions of the 2-step CBRA reaches the maximum number of preamble transmissions of the 2-step CBRA includes falling back to the 4-step CBRA in the cell after the number of preamble transmissions of the 2-step CBRA reaches the maximum number of preamble transmissions of the 2-step CBRA.

8. The method according to claim 1 ,

wherein the MAC subheader is a MAC subheader indicating the fallback from the 2-step CBRA to the 4-step CBRA.

9. The method according to claim 1 ,

wherein the third message is a message 3 (msg 3 ) in the 4-step CBRA.

10. The method according to claim 1 ,

wherein the communication apparatus is a Next Generation Radio Access Network (NG-RAN) node or a gNB.

11. A method performed by a communication apparatus, the method comprising:

transmitting, to a User Equipment (UE), information indicating a maximum number of preamble transmissions of a 2-step Contention Based Random Access (CBRA);

receiving a first message of the 2-step CBRA from the UE;

transmitting a second message of the 2-step CBRA to the UE,

wherein the second message includes:

a Medium Access Control (MAC) subheader associated with a fallback, and

an uplink grant indicating an uplink resource used for transmission of a third message of a 4-step CBRA; and

receiving, from the UE, the third message of the 4-step CBRA transmitted based on the uplink grant in a case where the second message is transmitted,

wherein the information is used for falling back to the 4-step CBRA after a number of preamble transmissions of the 2-step CBRA reaches the maximum number of preamble transmissions of the 2-step CBRA, and

wherein a counter for counting the number of preamble transmissions is kept in a case of the falling back to the 4-step CBRA.

12. The method according to claim 11 ,

wherein the counter is

PREAMBLE_TRANSMISSION_COUNTER, and

wherein the information is transmitted by a Radio Resource Control (RRC) message.

13. The method according to claim 11 ,

wherein the information indicates a maximum number of preamble transmissions of the 4-step CBRA.

14. The method according to claim 11 ,

wherein the first message of the 2-step CBRA is received in a cell of the communication apparatus,

wherein the second message of the 2-step CBRA is transmitted in the cell, and

wherein the information is used for falling back to the 4-step CBRA in the cell after the number of preamble transmissions of the 2-step CBRA reaches the maximum number of preamble transmissions of the 2-step CBRA.

15. The method according to claim 11 ,

wherein the MAC subheader is a MAC subheader indicating the fallback from the 2-step CBRA to the 4-step CBRA.

16. The method according to claim 11 ,

wherein the third message is a message 3 (msg 3 ) in the 4-step CBRA.

17. The method according to claim 11 ,

wherein the communication apparatus is a Next Generation Radio Access Network (NG-RAN) node or a gNB.

18. A User Equipment (UE) comprising:

at least one memory; and

at least one processor coupled to the at least one memory and configured to:

receive, from a communication apparatus, information indicating a maximum number of preamble transmissions of a 2-step Contention Based Random Access (CBRA);

transmit a first message of the 2-step CBRA to the communication apparatus;

receive a second message of the 2-step CBRA from the communication apparatus,

wherein the second message includes:

a Medium Access Control (MAC) subheader associated with a fallback, and

an uplink grant indicating an uplink resource used for transmission of a third message of a 4-step CBRA;

transmit, to the communication apparatus, the third message of the 4-step CBRA based on the uplink grant in a case where the UE receives the second message;

fall back to the 4-step CBRA after a number of preamble transmissions of the 2-step CBRA reaches the maximum number of preamble transmissions of the 2-step CBRA; and

keep a counter for counting the number of preamble transmissions in a case of the fall back to the 4-step CBRA.

19. A communication apparatus comprising:

at least one memory; and

at least one processor coupled to the at least one memory and configured to:

transmit, to a User Equipment (UE), information indicating a maximum number of preamble transmissions of a 2-step Contention Based Random Access (CBRA);

receive a first message of the 2-step CBRA from the UE;

transmit a second message of the 2-step CBRA to the UE,

wherein the second message includes:

a Medium Access Control (MAC) subheader associated with a fallback, and

an uplink grant indicating an uplink resource used for transmission of a third message of a 4-step CBRA; and

receive, from the UE, the third message of the 4-step CBRA transmitted based on the uplink grant in a case where the second message is transmitted,

wherein the information is used for falling back to the 4-step CBRA after a number of preamble transmissions of the 2-step CBRA reaches the maximum number of preamble transmissions of the 2-step CBRA, and

wherein a counter for counting the number of preamble transmissions is kept in a case of the falling back to the 4-step CBRA.

Priority Claims (1)

Continuity (2)

References Cited (30)