Method and device for transmitting small data in wireless communication system
The present disclosure may provide a method of transmitting, by a user equipment (UE), small data in a wireless communication system. Here, a small data transmission method may include enabling a small data configuration in a UE; triggering, by the UE, a small data transmission; transmitting, by the UE, a common control channel (CCCH) and buffered data information to a base station in a random access channel (RACH) procedure; receiving a random access response (RAR) including an uplink (UL) grant from the base station based on the buffered data information; and transmitting the small data based on the UL grant.
1 . A method comprising:
receiving, by a wireless user device, system information indicating a plurality of physical random access channel (PRACH) configurations comprising a first PRACH configuration for small data transmission and a second PRACH configuration for small data transmission, wherein the first PRACH configuration comprises a plurality of random access channel (RACH) resources for small data transmission associated with a radio resource control (RRC) inactive state;
receiving, by the wireless user device in an RRC connected state, an RRC release message;
transitioning, by the wireless user device and based on the RRC release message, from the RRC connected state to the RRC inactive state;
transmitting, by the wireless user device in the RRC inactive state to a base station, a message A (MsgA) for a 2-step RACH procedure, wherein the MsgA comprises a preamble and MsgA physical uplink shared channel (MsgA PUSCH), wherein the MsgA PUSCH comprises a buffer status report medium access control control element (BSR MAC CE), and wherein the BSR MAC CE indicates a data size;
receiving, by the wireless user device in the RRC inactive state, a fallback random access response (RAR) comprising an uplink (UL) grant; and
based on the UL grant, transmitting, by the wireless user device in the RRC inactive state, a message 3 (Msg3) to the base station via a selected RACH resource for 4-step RACH procedure, wherein the Msg3 comprises common control channel (CCCH) data and small data,
wherein the first PRACH configuration comprises a first preamble group for 4-step RACH procedure, a second preamble group for 4-step RACH procedure, a third preamble group for 2-step RACH procedure, and a fourth preamble group for 2-step RACH procedure, and
wherein the second PRACH configuration comprises a fifth preamble group for 4-step RACH procedure, a sixth preamble group for 4-step RACH procedure, a seventh preamble group for 2-step RACH procedure, and an eighth preamble group for 2-step RACH procedure.
2 . The method of claim 1 , wherein the plurality of RACH resources for small data transmission associated with the RRC inactive state comprises at least one of:
a 2-step RACH resource; or
a 4-step RACH resource.
3 . The method of claim 1 , wherein the plurality of RACH resources for small data transmission associated with the RRC inactive state are configured on a bandwidth part (BWP).
4 . The method of claim 1 , wherein an amount of the small data does not exceed a data amount threshold.
5 . The method of claim 1 , further comprising:
retransmitting, by the wireless user device in the RRC inactive state, the Msg 3 .
6 . The method of claim 1 , further comprising:
after the transmitting the Msg 3 , maintaining, by the wireless user device, the RRC inactive state.
7 . The method of claim 1 , further comprising:
after the transmitting the small data, performing, by the wireless user device, a random access procedure to transition from the RRC inactive state to a second RRC connected state.
8 . The method of claim 1 , further comprising:
receiving, by the wireless user device, a message, for the selected RACH resource, indicating at least one of:
a mapping between one RACH occasion and one or more synchronization signal blocks (SSBs); or
a mapping between one or more contention-based preambles and one synchronization signal block (SSB).
9 . The method of claim 1 , wherein the RRC release message indicates:
a transition from the RRC connected state to the RRC inactive state; and
a small data configuration for the RRC inactive state.
10 . The method of claim 1 , further comprising:
determining, based on a measurement of a reference signal received power of a synchronization signal block (SSB), a 2-step RACH for transmission of uplink data or a 4-step RACH for transmission of the uplink data.
11 . The method of claim 1 , wherein the system information further indicates:
a second RACH resource for contention-based random access for transition to an RRC connected state; and
a third RACH resource for contention-free random access for transition to an RRC connected state.
12 . The method of claim 1 , wherein the system information further indicates:
a second RACH resource for 2-step random access for transition to an RRC connected state; and
a third RACH resource for 4-step random access for transition to an RRC connected state.
13 . A method comprising:
receiving, by a wireless user device, configuration parameters indicating a plurality of physical random access channel (PRACH) configurations, wherein the plurality of PRACH configurations comprise:
a plurality of first random access channel (RACH) resources for small data transmission associated with a radio resource control (RRC) inactive state;
a second RACH resource for contention-based random access; and
a third RACH resource for contention-free random access;
receiving, by the wireless user device in an RRC connected state, an RRC release message, wherein the RRC release message indicates transition from the RRC connected state to the RRC inactive state;
transmitting, by the wireless user device in the RRC inactive state to a base station, a message A (MsgA) for a 2-step RACH procedure, wherein the MsgA comprises a preamble and MsgA physical uplink shared channel (MsgA PUSCH), wherein the MsgA PUSCH comprises a buffer status report medium access control control element (BSR MAC CE), and wherein the BSR MAC CE indicates a data size;
receiving, by the wireless user device in the RRC inactive state, a fallback random access response (RAR) comprising an uplink (UL) grant; and
based on the UL grant, transmitting, by the wireless user device in the RRC inactive state, a message 3 (Msg3) to the base station via a selected RACH resource for 4-step RACH procedure, wherein the Msg3 comprises common control channel (CCCH) data and small data,
wherein the plurality of PRACH configurations comprises a first PRACH configuration for small data transmission, wherein the first PRACH configuration comprises a first preamble group for 4-step RACH procedure, a second preamble group for 4-step RACH procedure, a third preamble group for 2-step RACH procedure, and a fourth preamble group for 2-step RACH procedure, and
wherein the plurality of PRACH configurations further comprises a second PRACH configuration for small data transmission, and wherein the second PRACH configuration comprises a fifth preamble group for 4-step RACH procedure, a sixth preamble group for 4-step RACH procedure, a seventh preamble group for 2-step RACH procedure, and an eighth preamble group for 2-step RACH procedure.
14 . The method of claim 13 , further comprising:
after the transmitting the Msg3, maintaining, by the wireless user device, the RRC inactive state.
15 . The method of claim 13 , wherein the second RACH resource for contention-based random access comprises at least one of:
a 2-step RACH resource for contention-based random access for transition to an RRC connected state; or
a 4-step RACH resource for contention-based random access for transition to an RRC connected state.
16 . The method of claim 13 , wherein the third RACH resource for contention-free random access comprises at least one of:
a 2-step RACH resource for contention-free random access for transition to an RRC connected state; or
a 4-step RACH resource for contention-free random access for transition to an RRC connected state.
17 . The method of claim 13 , further comprising:
after the transmitting the Msg3, performing, by the wireless user device, a random access procedure to transition from the RRC inactive state to a second RRC connected state.