Random access for millimeter-wave cellular systems with directional beams

The overall duration of random access (RA) in millimeter-wave (mm-wave) cellular systems with directional beams is protracted because preambles should be transmitted in all directions of Tx and Rx beams. In this paper, two different types of RA preambles (RAPs; TYPE-1 and TYPE-2) are proposed with multiple antenna arrays to reduce the RA duration. It is shown by simulation that the TYPE-2 RAP is well-suited for RA in mm-wave cellular systems with multiple directional beams because of high detection probability in a multi-user environment, shorter processing time, and reasonably low complexity.