Apparatus and method for performing random access in beam-formed system

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

transmitting, to a base station, a first random access preamble using a first transmission beam based on a first power;

identifying whether a random access response is received from the base station as a response to the first random access preamble;

identifying whether a second transmission beam is changed from the first transmission beam, in case that the random access response is not received;

in case that the second transmission beam is not changed, incrementing a counter associated with preamble transmission power ramping, identifying a second power for transmitting a second random access preamble based on the counter, and transmitting the second random access preamble using the first transmission beam based on the second power; and

in case that the second transmission beam is changed, transmitting, to the base station, the second random access preamble using the second transmission beam based on the first power.

2. The method of claim 1 , further comprising:

selecting a first synchronization signal block (SSB) among at least one SSB based on signal strength of the first SSB being above a threshold,

wherein the first random access preamble is transmitted in a first physical random access channel (PRACH) occasion corresponding to the first SSB.

3. The method of claim 2 , further comprising:

receiving, from the base station, configuration information by a broadcast signaling or a dedicated signaling, the configuration information including information on PRACH occasions and information on association between the PRACH occasions and SSBs.

4. The method of claim 3 , wherein the first PRACH occasion corresponding to the first SSB is identified based on the configuration information.

5. The method of claim 1 , further comprising:

selecting a second SSB among at least one SSB based on signal strength of the second SSB being above a threshold,

wherein the second random access preamble is transmitted in a second PRACH occasion corresponding to the second SSB.

6. The method of claim 5 , further comprising:

receiving, from the base station, configuration information by a broadcast signaling or a dedicated signaling, the configuration information including information on PRACH occasions and information on association between the PRACH occasions and SSBs.

7. The method of claim 6 , wherein the second PRACH occasion corresponding to the second SSB is identified based on the configuration information.

8. The method of claim 1 , wherein different SSBs correspond to different beams.

9. The method of claim 1 , wherein in case that the second transmission beam is changed, the counter is not incremented.

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

a transceiver; and

at least one processor configured to:

transmit, to a base station via the transceiver, a first random access preamble using a first transmission beam based on a first power,

identify whether a random access response is received from the base station as a response to the first random access preamble,

identify whether a second transmission beam is changed from the first transmission beam, in case that the random access response is not received,

in case that the second transmission beam is not changed, increment a counter associated with preamble transmission power ramping, identify a second power for transmitting a second random access preamble based on the counter, and transmit, to the base station via the transceiver, the second random access preamble using the first transmission beam based on the second power, and

in case that the second transmission beam is changed, transmit, to the base station via the transceiver, the second random access preamble using the second transmission beam based on the first power.

11. The terminal of claim 10 , wherein the at least one processor is further configured to:

select a first synchronization signal block (SSB) among at least one SSB based on signal strength of the first SSB being above a threshold, and

transmit the first random access preamble in a first physical random access channel (PRACH) occasion corresponding to the first SSB.

12. The terminal of claim 10 , wherein the at least one processor is further configured to:

select second SSB among at least one SSB based on signal strength of the second SSB being above a threshold, and

transmit the second random access preamble in a second PRACH occasion corresponding to the second SSB.

13. The terminal of claim 12 , wherein the at least one processor is further configured to receive, from the base station via the transceiver, configuration information by a broadcast signaling or a dedicated signaling, the configuration information including information on PRACH occasions and information on association between the PRACH occasions and SSBs.

14. The terminal of claim 13 , the at least one processor is further configured to identify the second PRACH occasion corresponding to the second SSB based on the configuration information.

15. The terminal of claim 11 , wherein the at least one processor is further configured to receive, from the base station via the transceiver, configuration information by a broadcast signaling or a dedicated signaling, the configuration information including information on PRACH occasions and information on association between the PRACH occasions and SSBs.

16. The terminal of claim 15 , wherein the at least one processor is further configured to identify the first PRACH occasion corresponding to the first SSB based on the configuration information.

17. The terminal of claim 10 , wherein different SSBs correspond to different beams.

18. The terminal of claim 10 , wherein the at least one processor is further configured to maintain the counter in case that the second transmission beam is changed from the first transmission beam.