If the LAN-Cell 3 disconnects and reconnects every few minutes, check the following:

1. Signal Strength
   Reboot the LAN-Cell and immediately check the signal strength. Poor signal can cause frequent disconnections. 
   
   
2. WAN Fail-Over Connectivity Check
   Go to the Setup > WAN Advanced screen.  If the Ping Target Type is Default Gateway, your ISP may not respond to ping requests, resulting in the LAN-Cell's WAN connection going up and down repeatedly.  Change the setting to Custom and enter the IP address of a device that is highly reliable and fast. Google's public DNS service (8.8.8.8) is a common choice.  Also consider increasing the Consectutive Failure Tolerance and Max Reply Wait Time settings, especially on 3G networks or if your signal strength is poor.
   
   
3. Antenna Connections
   Check that any external antenna connections are secure to the USB modem and that all other connections are tight. If any connectors are located outdoors, they must be waterproofed to prevent moisture from entering the coaxiable cable and shorting the signal.