Cellular Direct-connect In-Building Amplifier, with Outdoor Directional Yagi Antenna
Drawing showing an example of a direct-connect bidirectional amplifier connection between a 4G/5G router or modem to a directional antenna to improve indoor cellular reception. The direct attach amp is important for maximum power transfer.
Yagi antenna provides high gain but it needs to be oriented to the direction of maximum received signal strength. Other components include surge protector and a Wi-Fi router if the cellular device has no Wi-Fi capability.
See more on techniques to improve cellular signal.