Best method would be something like a Mikrotik Routerboard http://routerboard.com/RB922UAGS-5HPacD board which accepts a 3g/4g sim card andaa usb LTE modem. here is a link to one that is working http://www.oncloudnet.eu/en/connection-mikrotik-on-4g-lte/ I use routerboards and hotspotsystem in a few locations and they work well together, I have not used any 3g/4g options yet.
