The UTStarcom USB Diagnostic Serial Port (WDM) Windows driver is a device driver used to enable communication between a computer and UTStarcom mobile devices, particularly when used for diagnostics or development purposes. The "WDM" part of the name refers to Windows Driver Model, a driver architecture used by Microsoft to ensure compatibility with various types of hardware on Windows systems.

This driver typically comes into play when you connect a UTStarcom device (like a mobile phone or modem) to your computer via a USB port for purposes such as firmware updates, diagnostics, or other advanced troubleshooting tasks. The USB diagnostic serial port allows the PC to interact with the mobile device as though it were connected through a serial port, enabling tools like diagnostic utilities to communicate with the device.