Which wireless setup method is considered rare?

The rare wireless setup method among the choices is USB. This method typically involves a physical connection where a device is set up via a USB cable, which contrasts with other methods that leverage wireless communication for configuration. While USB can be effective for certain initial setups or firmware updates, it lacks the convenience and flexibility of entirely wireless methods.

In comparison, the other options, such as PIN, Push-button, and NFC, are techniques designed to facilitate easy and quick wireless pairing of devices. PIN setup typically involves entering a numeric code on each device, enabling secure communication without needing a wired connection. Push-button setup, often referred to as WPS (Wi-Fi Protected Setup), allows users to connect devices with a simple press of a button, streamlining the process significantly. NFC (Near Field Communication) also enables quick setup by simply bringing two NFC-enabled devices close together, facilitating secure exchange of setup information.

Thus, USB's reliance on a physical connection makes it less common in scenarios where wireless setups are preferred for their ease and convenience.