Analysis of Broadcast Signaling for Millimeter Wave Cell Discovery

Abstract

Millimeter wave (mm-wave) communication is essential for the next generation cellular networks. To exploit mm-wave frequencies, directional transmissions have to be applied to compensate the high propagation loss. Due to directional transmissions, initial access procedure of mm-wave communication systems needs specific design compared to conventional networks operating at sub-6 GHz. This paper focuses on an important step in the initial access procedure, namely broadcast signaling design for cell discovery. An analysis of such design is conducted based on an information theoretical approach, where four fundamental beam patterns, which cover most of the design options, are compared. Their performances in terms of cell discovery latency and signaling overhead are analyzed. The analysis reveals three key findings: (i) the average cell discovery latency depends only on beam duration and frame length, if the entire beacon interval can be accommodated in one frame; (ii) for low latency, single beam exhaustive scanning provides the best performance, but results in high signaling overhead; (iii) simultaneous multi-beam scanning can significantly reduce the overhead, and provide the flexibility to achieve trade-off between latency and overhead. The analytical results are verified by extensive simulations.