The way of networking is mainly through WiFi or built-in SIM card + WiFi, and the way to access the Internet through the Bluetooth connection of the mobile phone is relatively rare. Most of the WiFi connections currently only support 2.4G. Most of the SIM cards currently support 3G networks, but this has the potential risk that operators can’t use this function after canceling 2G and 3G networks. Fitness trackers using this web standard are not recommended.
Why not use 4G network modules in large numbers? Standby power consumption, power consumption, antenna tuning, and interference performance are all places to consider. It is a big challenge to design a communication-related design like a mobile phone with such a small area. For the SIM card, it is not recommended to choose a smart watch or fitness tracker with a built-in SIM card that cannot be replaced. It is common to match some virtual carrier numbers. The most excessive is to directly solder the SIM card to the watch or fitness tracker. If you don’t use your watch for rigid calling, it’s best not to buy a smart watch or fitness tracker that supports a SIM card.