mm Wave Initial Cell Search Analysis under UE Rotational Motion

Millimeter wave (mmW) communication has emerged as a promising component of the access link for 5G cellular systems. In order to overcome the higher free-space path loss at these frequencies, high gain, and therefore highly directional, antennas are being proposed at both ends of the link. Furthermore, in order to maintain a mobile connection with an acceptable quality of service (QOS), these highly directional antennas also need to be electronically steerable. This required dual-end steerability adds significant system complexity in terms of both initial access and connected mode procedures. Therefore, these various procedures which were originally designed for the current sub 6 GHz systems need to be re-investigated in light of this added complexity. Traditionally, sub 6 GHz mobility studies mainly focused on translational motion; however, with the dual-end highly directional links being proposed for mmW communications, rotational motion also becomes a concern. In this paper, we study the effects these steerable links have on initial network access procedures, especially in the presence of user equipment (UE) rotational motion.