Method and apparatus for retransmission in sidelink communication

1 . An operation method of a transmitting terminal in a communication system, the operation method comprising:

transmitting, to a receiving terminal, first data based on a first retransmission scheme;

in response to that a preconfigured condition is satisfied, switching a retransmission scheme from the first retransmission scheme to a second retransmission scheme; and

transmitting, to the receiving terminal, second data based on the second retransmission scheme,

wherein the first retransmission scheme and the second retransmission scheme are distinguished according to whether a hybrid automatic repeat request (HARQ) feedback is transmitted,

wherein when the first retransmission scheme is a HARQ retransmission scheme, the second retransmission scheme is a blind retransmission scheme, and when the first retransmission scheme is the blind retransmission scheme, the second retransmission scheme is the HARQ retransmission scheme, and

wherein when the HARQ retransmission scheme is used, the HARQ feedback is transmitted, and when the blind retransmission scheme is used, the HARQ feedback is not transmitted.

2 . The operation method according to claim 1 , wherein the preconfigured condition is configured from the base station through higher layer signaling.

3 . The operation method according to claim 1 , wherein a case in which the preconfigured condition is satisfied is a case when negative acknowledgment (NACK) for the first data occurs n or more times or a case when a channel state between the transmitting terminal and the receiving terminal satisfies a reference, n being a natural number.

4 . The operation method according to claim 1 , further comprising transmitting, to the receiving terminal, a first indicator indicating that the retransmission scheme is switched, wherein the transmitting of the second data is performed after transmission of the first indicator.

5 . The operation method according to claim 4 , wherein the first indicator is included in first-stage sidelink control information (SCI) or second-stage SCI transmitted from the transmitting terminal to the receiving terminal.

6 . The operation method according to claim 1 , further comprising, when the retransmission scheme is switched, transmitting, to the base station, a second indicator indicating that the retransmission scheme is switched.

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

transmitting, to the base station, a third indicator requesting switching of the retransmission scheme; and

receiving, from the base station, a fourth indicator allowing switching of the retransmission scheme,

wherein the retransmission scheme is switched when the fourth indicator is received.

8 . The operation method according to claim 1 , further comprising receiving, from a base station, a fifth indicator requesting switching of the retransmission scheme, wherein the retransmission scheme is switched when the fifth indicator is received.

9 . The operation method according to claim 1 , wherein the retransmission scheme is switched in unit of a transport block (TB), code block group (CBG), or HARQ process.

10 . An operation method of a receiving terminal in a communication system, the operation method comprising:

receiving, from a transmitting terminal, first data based on a first retransmission scheme;

receiving, from the transmitting terminal, a first indicator indicating that a retransmission scheme is switched; and

receiving, from the transmitting terminal, second data based on a second retransmission scheme,

wherein the first retransmission scheme and the second retransmission scheme are distinguished according to whether a hybrid automatic repeat request (HARQ) feedback is transmitted,

wherein when the first retransmission scheme is a HARQ retransmission scheme, the second retransmission scheme is a blind retransmission scheme, and when the first retransmission scheme is the blind retransmission scheme, the second retransmission scheme is the HARQ retransmission scheme, and

wherein when the HARQ retransmission scheme is used, the HARQ feedback is transmitted, and when the blind retransmission scheme is used, the HARQ feedback is not transmitted.

11 . The operation method according to claim 10 , wherein the first indicator is included in first-stage sidelink control information (SCI) or second-stage SCI transmitted from the transmitting terminal to the receiving terminal.

12 . The operation method according to claim 10 , further comprising:

in response to that a preconfigured condition is satisfied, determining that the second retransmission scheme is switched to the first retransmission scheme; and

receiving, from the transmitting terminal, third data based on the first retransmission scheme.

13 . The operation method according to claim 12 , wherein the preconfigured condition is configured from the base station through higher layer signaling.

14 . The operation method according to claim 12 , wherein a case in which the preconfigured condition is satisfied is a case when negative acknowledgment (NACK) for the second data occurs n or more times or a case when a channel state between the transmitting terminal and the receiving terminal satisfies a reference, n being a natural number.

15 . A transmitting terminal in a communication system, the transmitting terminal comprising:

a processor; and

a memory storing one or more instructions executable by the processor,

wherein the one or more instructions are executed to perform:

transmitting, to a receiving terminal, first data based on a first retransmission scheme;

in response to that a preconfigured condition is satisfied, switching a retransmission scheme from the first retransmission scheme to a second retransmission scheme; and

transmitting, to the receiving terminal, second data based on the second retransmission scheme,

wherein the first retransmission scheme and the second retransmission scheme are distinguished according to whether a hybrid automatic repeat request (HARQ) feedback is transmitted,

wherein when the first retransmission scheme is a HARQ retransmission scheme, the second retransmission scheme is a blind retransmission scheme, and when the first retransmission scheme is the blind retransmission scheme, the second retransmission scheme is the HARQ retransmission scheme, and

wherein when the HARQ retransmission scheme is used, the HARQ feedback is transmitted, and when the blind retransmission scheme is used, the HARQ feedback is not transmitted.

16 . The transmitting terminal according to claim 15 , wherein the first indicator is included in first-stage sidelink control information (SCI) or second-stage SCI transmitted from the transmitting terminal to the receiving terminal.

17 . The transmitting terminal according to claim 15 , wherein the one or more instructions are further executed to perform: when the retransmission scheme is switched, transmitting, to the base station, a second indicator indicating that the retransmission scheme is switched.

18 . The transmitting terminal according to claim 15 , wherein the one or more instructions are further executed to perform:

transmitting, to the base station, a third indicator requesting switching of the retransmission scheme; and

receiving, from the base station, a fourth indicator allowing switching of the retransmission scheme,

wherein the retransmission scheme is switched when the fourth indicator is received.