A Preferred Roaming List (PRL) is a small file stored in CDMA modems (Verizon Wireless, Sprint) that contains a list of the carriers cell tower IDs and those of its roaming partners.

As cellular carriers add and move towers, merge, divest and otherwise reconfigure their networks, the PRL information in your 3G PC-Card modem can get out of date. This can result in your inability to make connections or your modem trying to communicate with a tower other than the one closest to it.

Mobile 3G devices in laptops, buses, vans, trains, etc are more likely to be affected by out of date PRL files than stationary 3G devices, however all devices should have their PRL information updated periodically.  For mobile devices, updating the PRL every 60 to 90 days is recommended.

To update the PRL file in your 3G PC-Card modem:

1. Power down the LAN-Cell
2. Remove the modem card from the LAN-Cell
3. Insert the modem card into a laptop that has the support software for that 3G modem model loaded
4. Launch the support software and look for a menu option to re-activate the modem or update the modem's firmware
   • For Verizon Wireless cards (VZAccess Manager), this option is under Options > Activation 
   • For Sprint cards (Sprint Mobile Broadband) it is under Menu > Settings (you must also call Sprint Technical Support to request the PRL update be sent to your device)
   • For Alltel cards (Axcess) it is under Tools > Activation

You cannot update the PRL file from inside the LAN-Cell.  Follow the procedures above.

GSM carriers (AT&T, T-Mobile, etc.) do not store PRL files in their 3G modems, so no PRL update is required.  However it is still a good idea to periodically check for modem firmware updates to ensure that you are getting the maximum performance from your device.