Initial Access in Millimeter Wave Cellular Systems

TLDR

Millimeter‑wave bands are attractive for next‑generation cellular systems because of their massive spectrum, yet initial access is challenging due to the need to search a large angular space with highly directional transmissions. The study compares design options for scanning and signaling procedures to evaluate access delay and system overhead. The authors analyze various scanning and signaling designs, taking into account channel structure and multiple‑access considerations. The analysis shows that low‑resolution fully digital architectures significantly outperform single‑stream analog beamforming.

Abstract

Millimeter wave (mmWave) bands have attracted considerable recent interest for next-generation cellular systems due to the massive available spectrum at these frequencies. However, a key challenge in designing mmWave cellular systems is initial access-the procedure by which a mobile device establishes an initial link-layer connection to a cell. MmWave communication relies on highly directional transmissions and the initial access procedure must thus provide a mechanism by which initial transmission directions can be searched in a potentially large angular space. Design options are compared considering different scanning and signaling procedures to evaluate access delay and system overhead. The channel structure and multiple access issues are also considered. The results of our analysis demonstrate significant benefits of low-resolution fully digital architectures in comparison with single stream analog beamforming.