1.8 — Wad Manager

Ensure your Wii doesn't lose power during an installation. A power failure while writing to the NAND can be fatal for the hardware.

It can read WAD files from an SD card, USB storage device, or even via a network (SMB). Why It’s "Classic" (and Risky) Wad Manager 1.8

A: No. Wad Manager 1.8 only installs to internal NAND. For USB loading, use USB Loader GX with emuNAND. Ensure your Wii doesn't lose power during an installation

Based on your request, it is highly likely you are referring to the homebrew application used on the Nintendo Wii, rather than an academic paper. "WAD" is the file format used for Wii channels and system software. USB storage device