About wireless coverage, generally, the lower the frequency the farther a wireless signal can travel. Therefore, devices on a 5 GHz network will tend to have a shorter range than those using 2.4 GHz....

Wired speed and wireless speed to WR841N are the speed, 1-1.1 mbps? If you restart the router, does it help? Reset it to factory defaults and reconfigure it.

The lower the frequency the farther a wireless signal can travel. Therefore, devices on a 5 GHz network will tend to have a shorter range than those using 2.4 GHz

WAN IP on status page of your router is private or public? http://www.tp-link.com/en/faq-785.html

C2 only supports VPN pass-through. VPN Passthrough does NOT mean the router can create a VPN endpoint. VPN Passthrough is a feature that allows VPN traffic created by other endpoints to "pass...

So you need a dual band router which can work with LTE USB dongle( NDIS USBModem)?