android tethering without using sim card?

My android phone has internet access through WiFi hotspot and it has no sim card inserted. I want to connect this phone to a router via usb or usb-to-rj45-wan-port whatever doable (there is some reason behind that to make the story short).

I can easily accomplish this configuration using PC (i.e., WiFi <–> PC network sharing <–> router), but when I try usb tethering on android it insists to have sim card although it can just use the WiFi connection to provide tethering service. Is there a way to achieve it?