modem reset

I have an idea to write something (script/app) that works entirely w/out internet connection (i.e. modem powered off, but with the router working fine; so all LAN devices can still talk to each other, there's just no WAN), and will check the modems status every X amount of time, say every 5 or...

Is there any way to restart a 3G modem without rebooting the router? I'm currently using a Sierra Wireless U598 in my Asus RT-AC56R (380.69). The device works great when it works, but tends to go offline randomly. The only way I have been able to get it to reconnect is to bounce the router...