我尝试使用华为的 LTE Stick (e3372) 连接到互联网。我安装了usb-modeswitch、ppp和wvdial。modewswitch 工作正常。该设备安装在 /dev/ttyUSB0 上，我可以在其中发送 AT 命令。我想与 wvdial 连接，但它总是说“PPP 守护进程已死：调制解调器挂断了电话（退出代码 = 16）”我的 wvdial 命令的控制台打印是：
pi@raspberrypi:~ $ sudo wvdial
--> WvDial: Internet dialer version 1.61
--> Initializing modem.
--> Sending: ATZ
ATZ
OK
--> Sending: ATQ0 V1 E1 S0=0
ATQ0 V1 E1 S0=0
OK
--> Sending: AT+CGDCONT=1,"IP","drei.at"
AT+CGDCONT=1,"IP","drei.at"
OK
^DSFLOWRPT:00000062,00000000,00000000,0000000000000000,0000000000000084,00000000,00000000
--> Modem initialized.
--> Sending: ATDT*99#
--> Waiting for carrier.
ATDT*99#
CONNECT
--> Carrier detected. Starting PPP immediately.
--> Starting pppd at Thu Mar 2 14:08:21 2017
--> Pid of pppd: 1142
--> Using interface ppp0
--> pppd: ���v[08]��[01]
--> pppd: ���v[08]��[01]
--> pppd: ���v[08]��[01]
--> pppd: ���v[08]��[01]
--> pppd: ���v[08]��[01]
--> Disconnecting at Thu Mar 2 14:08:52 2017
--> The PPP daemon has died: A modem hung up the phone (exit code = 16)
--> man pppd explains pppd error codes in more detail.
--> Try again and look into /var/log/messages and the wvdial and pppd man pages for more information.
--> Auto Reconnect will be attempted in 5 seconds
--> Initializing modem.
--> Sending: ATZ
--> Sending: ATQ0
--> Re-Sending: ATZ
^CCaught signal 2: Attempting to exit gracefully...
--> Modem not responding.
--> Disconnecting at Thu Mar 2 14:09:00 2017
我的 wvdial 配置文件：
[Dialer Defaults]
Init1 = ATZ
Init2 = ATQ0 V1 E1 S0=0
Init3 = AT+CGDCONT=1,"IP","drei.at"
Modem Type = Analog Modem
Baud = 9600
New PPPD = yes
Modem = /dev/ttyUSB0
ISDN = 0
Phone = *99#
Password = ;
Username = ;
Stupid Mode = 1
Dialer Attemps = 2
Carrier Check = off
是什么导致 ppp 守护进程挂起？