LTE Dial-up Connection Setup

LTE initiates a dial-up connection using circular dial control center (C-DCC). Two dial-up modes are available:

• Automatic dial-up (permanently online)

  The DCC initiates a dial-up connection to the PGW immediately after the router starts. The dial-up process does not need to be triggered by data packets. If the DCC fails to set up a connection with the PGW, it retries after an interval.

  This mode applies to users who are not charged based on the traffic or time, for example, users who have subscribed to yearly-package services.

• Dial-on-demand (not permanently online; traffic-triggered connection setup)

  The router sets up a connection only when data needs to be transmitted. When no traffic is transmitted on the connection within a specified period, the router tears down the connection to save traffic.

  This mode applies to users who are charged based on the traffic or time. For example, users of a traffic-package service can use a certain volume of traffic within a specified period.

As shown in Figure 12-2, when data needs to be transmitted or the dial-up timer expires, the router uses C-DCC to initiate a dial-up on a cellular interface and enables the LTE modem to connect to the PGW.

Figure 12-2 LTE dial-up connection setup

An LTE dial-up connection is set up in the following process:

1. When data needs to be transmitted or the dial-up timer expires, the router uses C-DCC to initiate a dial-up on a cellular interface. The cellular interface sends a connection setup request message to the LTE modem.
2. The LTE modem sends a connection setup request message to the PGW. The message contains user authentication information including the access point name (APN), user name, and password.
3. The PGW authenticates the user identity. After authentication succeeds, the PGW sets up a connection with the LTE modem and assigns an IP address to the LTE modem.
4. The LTE modem instructs the cellular interface to go Up physically.
5. The cellular interface negotiates with the LTE modem to obtain an IP address.
6. The cellular interface sets up a connection with the PGW and forwards data services.

The LTE module of the device does not support forwarding of DHCP packets.