This paper from Microosft provides information about portable Wi-Fi hotspots for Windows 8. It provides guidelines for device manufacturers to offer experiences on a Wi-Fi hotspot backed by mobile broadband (including a mobile phone) that are similar to experiences Windows would offer on a native mobile broadband connection. It assumes that the reader is familiar with Wi-Fi and mobile broadband in Windows 8, as well as device companion applications.

Download: Building Portable Hotspots for Windows 8 - Microsoft Download Center - Download Details