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

1. A method of performing a random access by an apparatus in a wireless communication system, the method comprising:

transmitting, to a base station, a first random access preamble using a first uplink (UL) transmission (TX) beam based on a first power;

identifying whether a random access response (RAR) is received in response to the first random access preamble;

if the RAR is not received, determining which beam is used to transmit a second random access preamble;

if the first UL TX beam is determined to be used to transmit the second random access preamble, identifying a second power by ramping up the first power by a first value;

transmitting the second random access preamble using the first UL TX beam based on the second power; and

if a second UL TX beam different from the first UL TX beam is determined to be used to transmit the second random access preamble, transmitting the second random access preamble using the second UL TX beam based on the first power.

2. The method of claim 1 , further comprising:

if the RAR is not received and a number of transmissions of random access preamble reaches a maximum value, determining that a random access has failed.

3. The method of claim 1 , further comprising:

receiving information on association between occasions for synchronization signal (SS) block and a subset of resources for random access preamble.

4. The method of claim 3 , further comprising:

determining a first downlink (DL) reception (RX) beam based on a downlink signal of the SS block; and

identifying the first UL TX beam corresponding to the determined first DL RX beam.

5. The method of claim 3 , wherein the determining of which beam is used to transmit the second random access preamble comprises:

determining a DL RX beam based on a downlink signal of the SS block; and

identifying a UL TX beam corresponding to the determined DL RX beam.

6. An apparatus in a wireless communication system, the apparatus comprising:

a transceiver configured to transmit and receive signals; and

at least one processor configured to:

transmit, to a base station, a first random access preamble using a first uplink (UL) transmission (TX) beam based on a first power,

identify whether a random access response (RAR) is received in response to the first random access preamble,

if the RAR is not received, determine which beam is used to transmit a second random access preamble,

if the first UL TX beam is determined to be used to transmit the second random access preamble, identify a second power by ramping up the first power by a first value,

transmit the second random access preamble using the first UL TX beam based on the second power; and

if a second UL TX beam different from the first UL TX beam is determined to be used to transmit the second random access preamble, transmit the second random access preamble using the second UL TX beam based on the first power.

7. The apparatus of claim 6 , wherein the at least one processor is further configured to:

If the RAR is not received and a number of transmissions of random access preamble reaches a maximum value determining that a random access has failed.

8. The apparatus of claim 6 , wherein the at least one processor is further configured to:

receive information on association between occasions for synchronization signal (SS) block and a subset of resources for random access preamble.

9. The apparatus of claim 6 , wherein the at least one processor is further configured to:

determine a first downlink (DL) reception (RX) beam based on a downlink signal of the SS block, and

identify the first UL TX beam corresponding to the determined first DL RX beam.

10. The apparatus of to claim 6 , wherein the at least one processor is further configured to:

determine a DL RX beam based on a downlink signal of the SS block, for determining which beam is used to transmit the second random access preamble, and

identify a UL TX beam corresponding to the determined DL RX beam.