Communication system

1. A method performed by a user equipment (UE), the method comprising:

receiving a Radio Resource Control (RRC) release message for configuring a data radio bearer (DRB) enabled for small data transmission in a RRC Inactive state; and

transmitting, while the UE is in the RRC Inactive state, a small data the DRB configured by the RRC release message.

2. The method according to claim 1 , wherein

the transmitting is performed by using a resource associated with a ‘configured grant type-1’.

3. The method according to claim 1 , wherein

the transmitting is performed via a message forming part of a random access procedure.

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

adding information identifying the UE to the small data,

wherein the information is included in a Medium Access Control (MAC) Control Element (CE) or an RRC information element.

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

segmenting uplink data to form a plurality of the small data,

wherein the adding is performed by adding the information identifying the UE to at least one of the plurality of the small data.

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

determining whether a Quality of Service (QOS) Flow Identifier (QFI) associated with the small data can be mapped to the DRB, and

the transmitting is performed based on a result of the determining.

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

configuring at least one layer of the DRB.

8. The method according to claim 1 , wherein

the RRC release message includes information indicating whether a signaling radio bearer (SRB) is configured for the small data transmission in the RRC Inactive state.

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

triggering a RRC resume procedure in a case where a size of the small data is larger than an allowed maximum size.

10. The method according to claim 7 , wherein the configuring the at least one layer of the DRB includes at least one of:

configuring a Service Data Adaptation Protocol (SDAP) layer without an SDAP header;

using a shortened Packet Data Convergence Protocol (PDCP) sequence number and/or using a 1 byte PDCP header size;

using a Transparent Mode (TM) for the small data transmission using the DRB;

configuring a Medium Access Control (MAC) layer without a Logical Channel Identifier (LCID) and/or a Length field; and

configuring a fixed size MAC Protocol Data Unit (PDU) for the small data.

11. A method performed by an access network node, the method comprising:

transmitting a Radio Resource Control (RRC) release message for configuring a data radio bearer (DRB) enabled for small data transmission in a RRC Inactive state; and

receiving, from the UE while the UE is in the RRC Inactive state, a small data using the DRB configured by the RRC release message.

12. A user equipment (UE) comprising:

a memory storing instructions; and

at least one processor configured to process the instructions to:

receive a Radio Resource Control (RRC) release message for configuring a data radio bearer (DRB) enabled for small data transmission in a RRC Inactive state;

transmit, while the UE is in the RRC Inactive state, a small data using the DRB configured by the RRC release message.

13. An access network node comprising:

a memory storing instructions; and

at least one processor configured to process the instructions to:

transmit a Radio Resource Control (RRC) release message for configuring a data radio bearer (DRB) enabled for small data transmission in a RRC Inactive state; and

receive, from the UE while the UE is in the RRC Inactive state, a small data using the DRB configured by the RRC release message.