Network entry method of millimeter wave communication system and related apparatueses using the same

According to one of the exemplary embodiments, the proposed network entry method is applicable to a user equipment and includes: receiving, within an mmWave band, Q scan beams which have Q IDs over M mmWave time units as each mmWave time unit includes a payload region and a BF header region that includes N BSSs with each of the BSSs corresponding to a different one of the Q scan beams, wherein M, N, and Q are integers greater than 1 and M*N=Q; determining a best beam of the UE based on the BSSs of the Q scan beams; determining a best scan beam of the Q scan beams based on the BSSs of the Q scan beams after determining the best beam of the UE; and transmitting, within the mmWave band, a random access preamble (RAP) by using the best beam of the UE.