Fast Initial Access Technique for Millimeter-Wave Systems Using Retrodirective Arrays

The beam alignment procedure in mmWave systems requires a significant overhead because it increases proportional to the product of the number of transmitting beams and number of receiving beams. In this paper, we propose an initial access technique that can significantly reduce the beam training overhead in mmWave cellular systems, using retrodirective array (RDA). A preamble sequence is designed to identify the base station (BS), mobile station (MS) and beams simultaneously transmitted from the BS, using the Zadoff-Chu sequence. The ambiguity condition is derived so that we can identify the ID of BS, MS and beams for beam alignment. Simulation results show that the proposed technique can correctly detect the parameters for beam alignment in mmWave cellular systems.