Some drones, such as the DJI Spark, can use a so-called OTG (On The Go) connection. This connects the phone and remote controller via USB and the Wi-Fi network is no longer necessary. The Wi-Fi connection between remote and drone will remain active, but because there is no other Wi-Fi source nearby, the signal improves considerably so that you will experience a stable connection and video feed for longer.
Some tip for your OTG connection:
Note: OTG is officially not supported (anymore) by DJI and you may need to install a previous firmware update to get the most out of your OTG connection. Whether it is worth missing the latest update against a more stable connection, we cannot advise and depends on the updates. Many people still buy and use OTG satisfactorily and personally we do not fly without it.
Update: OTG is working properly again in the latest firmware updates!