PPP for GSM/GPRS/3G

w5500 Is it possible to connect the w5500 directly to a GSM/GPRS/3G modem so that modem acts as an internet gateway?
There are many GSM/GPRS/3G modems available with serial interface for use with AT and PPP/3GPP, but very few that have an ethernet interface to connect direct to one of the w5500 ethernet ports to act as the gateway.
I’d rather not have to have an external chip to do ethernet to serial/AT/PPP/3GPP if I can avoid it.
If possible, how does the w5500get configured to do this?
If not possible, is there an alternative Wiznet product which can do this taskt.
Thanks,