In addition, when the same SSB is transmitted through multiple beams, the SSB may be beam-group specific. In this case, a terminal may only find the optimal DL Tx beam groups (or a DL wider beam) instead of a specific accurate (or narrow) beam. Also, in this case, it may be considered that the DL beam calibration is not fully done, and further procedure for finding out the exact DL Tx beam for the terminal may be performed.

FIG. 13 shows a structure of a base station according to an exemplary embodiment of the present invention.

As shown in FIG. 13, a base station 1 according to an exemplary embodiment of the present invention includes a processor 110, a memory 120, and a transceiver 130. The processor 110 may be configured to implement the methods described with reference to FIG. 1 or FIG. 12.

The memory 120 is connected to the processor 110, and stores various kinds of information related to operations of the processor 110 therein. The memory 120 may store instructions that are to be executed in the processor 110 therein or load and temporally store instructions from a storage unit (not shown) therein. The processor 110 may execute the instructions stored or loaded in the memory 120. The processor 110 and the memory 120 are connected to each other through a bus (not shown), and input and output interfaces (not shown) may also be connected to the bus.

The transceiver 130 may be configured to transmit/receive a signal, and for example, to receive a preamble message and to transmit a RAR.