Method and apparatus for performing random access in wireless communication system

1. A terminal in a wireless communication system, the terminal comprising:

a transceiver; and

at least one processor configured to:

control the transceiver to receive, from a base station (BS), a radio resource control (RRC) reconfiguration message comprising a reconfiguration with synchronization,

control the transceiver to transmit, to the BS, a first message comprising a physical random access channel (PRACH), a physical uplink shared channel (PUSCH), and a cell radio network temporary identity (C-RNTI) medium access control (MAC) control element (CE) based on the reconfiguration with synchronization, control the transceiver to receive, from the BS, a first physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH), wherein:

for the case when the BS receives the PRACH and does not receive the PUSCH, the first PDCCH is a PDCCH addressed to random access RNTI (RA-RNTI) and the PDSCH includes a fallback random access response (RAR); and

for the case when the BS receives the PUSCH, the first PDCCH is a PDCCH addressed to a C-RNTI corresponding to the C-RNTI MAC CE and the PDSCH includes an absolute timing advance command MAC CE,

determine that a RAR reception is successful based on at least one of the fallback RAR or the PDSCH,

when a discontinuous reception (DRX) is configured for the terminal via a RRC signalling, determine that an active time for the DRX includes a time while a second PDCCH indicating a new transmission addressed to the C-RNTI corresponding to the C-RNTI MAC CE has not been received after determining that the RAR reception is successful, and

monitor the second PDCCH during the active time.

2. The terminal of claim 1 ,

wherein the reconfiguration with synchronization comprises at least one of a terminal identity, timer information, or resource information for random access, and

wherein the resource information for random access comprises at least one of first dedicated resource information for contention-free 4-step random access comprising first synchronization signal block (SSB) resource information, or second dedicated resource information for contention-free 2-step random access comprising second SSB resource information and resource information for the PUSCH of the first message.

3. The terminal of claim 1 , wherein the at least one processor is further configured to determine to perform a 2-step random access procedure:

when the terminal receives, from the BS, both resource information for 4-step random access and resource information for 2-step random access and first reference signal received power (RSRP) of downlink pathloss reference signal is above a first RSRP threshold configured by the BS,

when the terminal receives, from the BS, the resource information for 2-step random access and does not receive the resource information for 4-step random access, or

when the reconfiguration with synchronization includes dedicated resource information for contention-free 2-step random access.

4. The terminal of claim 1 ,

wherein the reconfiguration with synchronization comprises dedicated resource information for contention-free 4-step random access, and

wherein the at least one processor is further configured to determine to perform a 4-step random access procedure.

5. The terminal of claim 2 ,

wherein the reconfiguration with synchronization comprises second dedicated resource information for contention-free 2-step random access comprising second SSB resource information associated with a plurality of SSBs, and

wherein the at least one processor is further configured to:

identify whether at least one SSB with a second reference signal received power (RSRP) above a second RSRP threshold among the plurality of SSBs is available,

when the at least one SSB with the second RSRP above the second RSRP threshold among the plurality of SSBs is available, determine to perform contention-free random access, and

when the at least one SSB with the second RSRP above the second RSRP threshold among the plurality of SSBs is not available, determine to perform contention-based random access.

6. The terminal of claim 1 , wherein the reconfiguration with synchronization indicates a handover command.

7. A base station (BS) in a wireless communication system, the BS comprising:

a transceiver; and

at least one processor configured to:

control the transceiver to transmit, to a terminal, a radio resource control (RRC) reconfiguration message comprising a reconfiguration with synchronization,

control the transceiver to receive, from the terminal, a first message comprising a cell radio network temporary identity (C-RNTI) medium access control (MAC) control element (CE) based on the reconfiguration with synchronization,

identify whether the BS receives at least one of a physical random access channel (PRACH) or a physical uplink shared channel (PUSCH) via the first message,

when the BS receives the PRACH and the PUSCH, control the transceiver to transmit, to the terminal, a third message comprising a first physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH) comprising an absolute timing advance command MAC CE,

when the BS receives the PRACH and does not receive the PUSCH, control the transceiver to transmit, to the terminal, a fallback random access response (RAR), and

control the transceiver to transmit, to the terminal, a second PDCCH,

wherein the second PDCCH is received by the terminal configured with a discontinuous reception (DRX) during active time, and

wherein the active time comprises a time while the second PDCCH indicating a new transmission addressed to a C-RNTI corresponding to the C-RNTI MAC CE has not been received after determining by the terminal that a RAR reception is successful.

8. The BS of claim 7 ,

wherein the reconfiguration with synchronization comprises at least one of a terminal identity, timer information, or resource information for random access, and

wherein the resource information for random access comprises at least one of first dedicated resource information for contention-free 4-step random access comprising first synchronization signal block (SSB) resource information, or second dedicated resource information for contention-free 2-step random access comprising second SSB resource information and resource information for the PUSCH of the first message.

9. The BS of claim 7 , wherein the terminal performs a 2-step random access procedure:

when the terminal receives, from the BS, both resource information for 4-step random access and resource information for 2-step random access and first reference signal received power (RSRP) of downlink pathloss reference signal is above a first RSRP threshold configured by the BS,

when the terminal receives, from the BS, the resource information for 2-step random access and does not receive the resource information for 4-step random access, or

when the reconfiguration with synchronization comprises dedicated resource information for contention-free 2-step random access.

10. The BS of claim 7 , wherein the terminal performs a 4-step random access procedure when the reconfiguration with synchronization includes dedicated resource information for contention-free 4-step random access.

11. The BS of claim 8 ,

wherein the reconfiguration with synchronization comprises second dedicated resource information for contention-free 2-step random access comprising second SSB resource information associated with a plurality of SSBs,

wherein the terminal performs contention-free random access when at least one SSB with a second RSRP above a second RSRP threshold among the plurality of SSBs is available, and

wherein the terminal performs contention-based random access when the at least one SSB with the second reference signal received power (RSRP) above the second RSRP threshold among the plurality of SSBs is not available.

12. The BS of claim 7 , wherein the reconfiguration with synchronization indicates a handover command.

13. A method, performed by a terminal, in a wireless communication system, the method comprising:

receiving, from a base station (BS), a radio resource control (RRC) reconfiguration message comprising a reconfiguration with synchronization;

transmitting, to the BS, a first message comprising a physical random access channel (PRACH), a physical uplink shared channel (PUSCH), and a cell radio network temporary identity (C-RNTI) medium access control (MAC) control element (CE) based on the reconfiguration with synchronization,

receiving, from the BS, a first physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH), wherein:

for the case when the BS receives the PRACH and does not receive the PUSCH, the first PDCCH is a PDCCH addressed to random access RNTI (RA-RNTI) and the PDSCH includes a fallback random access response (RAR); and

for the case when the BS receives the PUSCH, the first PDCCH is a PDCCH addressed to a C-RNTI corresponding to the C-RNTI MAC CE and the PDSCH includes an absolute timing advance command MAC CE,

determining that a RAR reception is successful based on at least one of the fallback RAR or the PDSCH;

when a discontinuous reception (DRX) is configured for the terminal via a RRC signalling, determining that active time for the DRX includes a time while a second PDCCH indicating new transmission addressed to the C-RNTI corresponding to the C-RNTI MAC CE has not been received after determining that the RAR reception is successful; and

monitoring the second PDCCH during the active time.

14. The method of claim 13 ,

wherein the reconfiguration with synchronization comprises at least one of a terminal identity, timer information, or resource information for random access, and

wherein the resource information for random access comprises at least one of first dedicated resource information for contention-free 4-step random access comprising first synchronization signal block (SSB) resource information, or second dedicated resource information for contention-free 2-step random access comprising second SSB resource information and resource information for the PUSCH of the first message.

15. The method of claim 13 , further comprising determining to perform a 2-step random access procedure:

when the terminal receives, from the BS, both resource information for 4-step random access and resource information for 2-step random access and first reference signal received power (RSRP) of downlink pathloss reference signal is above a first RSRP threshold configured by the BS,

when the terminal receives, from the BS, the resource information for 2-step random access and does not receive the resource information for 4-step random access, or

when the reconfiguration with synchronization includes dedicated resource information for contention-free 2-step random access.

16. The method of claim 14 ,

wherein the reconfiguration with synchronization comprises second dedicated resource information for contention-free 2-step random access comprising second SSB resource information associated with a plurality of SSBs, and

wherein the method further comprises:

identifying whether at least one SSB with a second reference signal received power (RSRP) above a second RSRP threshold among the plurality of SSBs is available;

when the at least one SSB with the second RSRP above the second RSRP threshold among the plurality of SSBs is available, determining to perform contention-free random access; and

when the at least one SSB with the second RSRP above the second RSRP threshold among the plurality of SSBs is not available, determining to perform contention-based random access.

17. A method, performed by a base station (BS), in a wireless communication system, the method comprising:

transmitting, to a terminal, a radio resource control (RRC) reconfiguration message comprising a reconfiguration with synchronization;

receiving, from the terminal, a first message comprising a cell radio network temporary identity (C-RNTI) medium access control (MAC) control element (CE) based on the reconfiguration with synchronization;

identifying whether the BS receives at least one of a physical random access channel (PRACH) or a physical uplink shared channel (PUSCH) via the first message;

when the BS receives the PRACH and the PUSCH, transmitting, to the terminal, a third message comprising a first physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH) comprising an absolute timing advance command MAC CE;

when the BS receives the PRACH and does not receive the PUSCH, transmitting, to the terminal, a fallback random access response (RAR); and

transmitting, to the terminal, a second PDCCH,

wherein the second PDCCH is received by the terminal configured with a discontinuous reception (DRX) during active time, and

wherein the active time comprises a time while the second PDCCH indicating new transmission addressed to a C-RNTI corresponding to the C-RNTI MAC CE has not been received after determining by the terminal that a RAR reception is successful.

18. The method of claim 17 ,

wherein the reconfiguration with synchronization comprises at least one of a terminal identity, timer information, or resource information for random access, and

wherein the resource information for random access comprises at least one of first dedicated resource information for contention-free 4-step random access comprising first synchronization signal block (SSB) resource information, or second dedicated resource information for contention-free 2-step random access comprising second SSB resource information and resource information for the PUSCH of the first message.

19. The method of claim 17 , wherein the terminal performs a 2-step random access procedure:

when the terminal receives, from the BS, both resource information for 4-step random access and resource information for 2-step random access and first reference signal received power (RSRP) of downlink pathloss reference signal is above a first RSRP threshold configured by the BS;

when the terminal receives, from the BS, the resource information for 2-step random access and does not receive the resource information for 4-step random access; or

when the reconfiguration with synchronization includes dedicated resource information for contention-free 2-step random access.

20. The method of claim 17 ,

wherein the reconfiguration with synchronization comprises second dedicated resource information for contention-free 2-step random access comprises second SSB resource information associated with a plurality of SSBs,

wherein the terminal performs contention-free random access when at least one SSB with a second reference signal received power (RSRP) above a second RSRP threshold among the plurality of SSBs is available, and

wherein the terminal performs contention-based random access when the at least one SSB with the second RSRP above the second RSRP threshold among the plurality of SSBs is not available.