Initial access and beam management

mmWave operation is noteworthy. It opens frequency bands that were not accessible before – for example, Frequency Range 2 (FR2), as described in the first chapter. It brings more room for bigger bandwidth, which enables higher capacity and throughput. However, the transmission of mmWave is complicated. The path loss of mmWave due to free space propagation is much bigger than the typical LTE frequency. This culminates in limited cell coverage and cell size. To partially overcome this issue, directional beams are used on downlink transmission and uplink reception so that the path loss due to the free space propagation is partially compensated.

Directional transmissions enable new methods of multiplexing different users in the spatial domain, such as transmitting simultaneously to different directions instead of spatial multiplexing based on precoders, as with LTE. However, such directional transmissions mean that when connecting to the network...