Automatically starting pppd on boot requires: (1) setting the peer file to use, 2) configuring the PPP init script (this applies to all radios as of version 3.3.12),  and (3) telling the system to run the ppp init script on boot.

Set Peer File and Configure the PPP init script (applies to all radios as of version 3.3.12)

1. Issue ls /etc/ppp/peers to see the available peers files (gsm, cdma, etc.)
2. The file /etc/default/ppp configures the ppp start on boot. There are two parameters:CHECKREGISTRATION is used to decide whether or not to verify cellular network registration before attempting ppp. If the SIM is not yet registered with the carrier, ppp will fail.PPPTIMEOUT is the maximum accumulated amount of time to allow from the start of /etc/init.d/ppp to the time of cellular modem registration with cellular carrier. If the registration never occurs in the alloted time, boot time will be increased by the PPPTIMEOUT amount. For instance, if the SIM is pulled out or replaced, the PPPTIMEOUT must be endured before the firmware and chat script switch will occur.
3. Edit /etc/ppp/ppp_on_boot (with vi or sudo) and change

   $ PPPD call provider

   to your desired provider (gsm or lvw2)

   $ PPPD call gsm

4. Assuming you’ve already set your APN (except for CDMA and LVW2), manually start the init script and check your internet connection to test your change to ppp_on_boot

   mtcdt: /etc/init.d/ppp start

Set Init Script to Auto Start

1. Issue this command:

   mtcdt: update-rc.d ppp defaults

2. Reboot the device and test your connection
3. To stop ppp from automatically starting, issue

   mtcdt: update-rc.d -f ppp remove