If it is not configured, the cellular interface is presented on the interface list either by modem USB address, or if serial modem is used, by modem name. This 'fake' interface name is replaced by 'proper' interface name (e.g., ppp0) when the first modem configuration is submitted.

The cellular interface should be configured by first enabling it in the TCP/IP tab, and then setting the Cellular tab. Note that the cellular interface can only be set as WAN using DHCP. The cellular interface configuration options are described below.

Cellular Configuration

The Cellular tab contains the following configuration parameters:

• Model - specifies the modem model.

• Network Technology - describes the network technology used by this modem.

  • HSDPA
  • EVDO

• Modem Identifier - provides a unique name for this modem.

• Interface # - provides a unique number for the modem interface (e.g., an interface # of 0 would name the modem interface ppp0).

• Dial String - instructs how the modem should attempt to connect. Typical dial strings are as follows:

  • HSPA modem - atd*99***1#
  • EVDO/CDMA modem - atd#777
    Note: This field is only visible for devices with the old ESF networking. For newer devices with NetworkManager, this field is automatically hidden by the UI.

• APN - defines the modem access point name. This parameter is mandatory for standard profiles and optional for generic ones. In the case of generic profiles, if it is left empty, the value is automatically picked up from the Mobile Broadband Provider the modem is registered to. If a value is filled, the APN value is explicitly configured. To avoid misconfiguration issues, it is strongly recommended to set it manually.

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APN value configuration

A good practice is to set the interface status to Disabled and then Enable For WAN when the APN is explicitly set. NetworkManager, indeed, will fallback to the default value if a wrong APN is specified, causing misleading behaviors. This does not happen if the interface is disabled and re-enabled after APN changes.

• Auth Type - specifies the authentication type.

  • None
  • Auto
  • CHAP
  • PAP

• Username - supplies the username; disabled if no authentication method is specified.

• Password - supplies the password; disabled if no authentication method is specified.

• Modem Reset Timeout - sets the modem reset timeout in minutes. If set to a non-zero value, the modem is reset after n consecutive minutes of unsuccessful connection attempts. If set to zero, the modem keeps trying to establish a PPP connection without resetting. The default value is 5 minutes.

• Reopen Connection on Termination - sets the persist option of the PPP daemon that specifies if PPP daemon should exit after connection is terminated. Note that the maxfail option still has an effect on persistent connections.

• Connection Attempts Retry Delay: Sets the holdoff parameter to instruct the PPP daemon on how many seconds to wait before re-initiating the link after it terminates. This option only has any effect if the persist option (Reopen Connection on Termination) is set to true. The holdoff period is not applied if the link was terminated because it was idle. The default value is 1 second.

• Connection Attempts - sets the maxfail option of the PPP daemon that limits the number of consecutive failed PPP connection attempts. The default value is 5 connection attempts. A value of zero means no limit. The PPP daemon terminates after the specified number of failed PPP connection attempts and restarts by the ModemMonitor thread.

• Disconnect if Idle - sets the idle option of the PPP daemon, which terminates the PPP connection if the link is idle for a specified number of seconds. The default value is 95 seconds. To disable this option, set it to zero.

• Active Filter - sets the active-filter option of the PPP daemon. This option specifies a packet filter (filter-expression) to be applied to data packets in order to determine which packets are regarded as link activity, and thereby, reset the idle timer. The filter-expression syntax is as described for tcpdump(1); however, qualifiers that do not apply to a PPP link, such as ether and arp, are not permitted. The default value is inbound. To disable the active-filter option, leave it blank.

• LCP Echo Interval - sets the lcp-echo-interval option of the PPP daemon. If set to a positive number, the modem sends LCP echo request to the peer at the specified number of seconds. To disable this option, set it to zero. This option may be used with the lcp-echo-failure option to detect that the peer is no longer connected.

• LCP Echo Failure - sets the lcp-echo-failure option of the PPP daemon. If set to a positive number, the modem presumes the peer to be dead if a specified number of LCP echo-requests are sent without receiving a valid LCP echo-reply. To disable this option, set it to zero.

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Notes about the APN parameter in generic profiles

The Access Point Name is an optional parameter in the generic profiles. If left empty, the value is automatically picked up from the Mobile Broadband Provider the modem is registered to. If a value is filled, the APN value is explicitly configured and the default value is overridden.

A good practice is to set the interface status to Disabled and then Enable For WAN when the APN is explicitly set. NetworkManager, indeed, will fallback to the default value if a wrong APN is specified, causing misleading behaviors. This does not happen if the interface is disabled and re-enabled after APN changes.

GPS

The GPS tab allows the user to enable or disable the GPS module provided by the cellular modem. The available properties are:

• Enable GPS: enables GPS module for the selected modem.
• GPS Mode (generic profiles only): specifies the GPS mode.
  • UNMANAGED: the GPS device of the modem will be setup but not directly managed, therefore freeing the serial port for other services to use. This can be used in order to perform the setup of the GPS and then have another service (like gpsd) parse the NMEA strings in order to extract the position informations.
  • MANAGED_GPS: the GPS device of the modem will be setup and directly managed (typically by ModemManager) therefore the serial port won't be available for other services to use.

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GPS modes availability

GPS modes available for the modem are dependent on the modem model, modem firmware version and ModemManager version installed on the system. Some modes may not be selectable if the modem does not support them.

For "device-specific profiles" the GPS mode is not available and implicitly set to UNMANAGED.

Therefore, to use the GPS module provided by the cellular modem with Kura's PositionService, the following considerations should be taken into account:

• The PositionService should be enabled. Serial settings of the PositionService should not be changed; it will be redirected to the modem GPS port automatically.
• To use the gpsd and serial PositionService providers with the GPS module provided by the cellular modem, the GPS mode should be set to UNMANAGED.
• To use the modemmanager PositionService provider with the GPS module provided by the cellular modem, the GPS mode should be set to MANAGED_GPS.

Refer to the Position Service section for more information.

Cellular Configuration with Telit Modems

This section applies to Telit products LE910-EU1, LE910-V2 EU/NA, LE910C1 and to other Telit products whose USB PID is 0x1201.

The following procedure MUST be followed to ensure that the authentication parameters used by the modem to register to an LTE network are effectively updated.

1. Invalidate the PDP context by modifying the APN parameter, setting it to any string as long as it is different from the current one
2. Apply changes
3. Set the desired values of APN, Auth Type, Username and Password
4. Apply changes

If PDP Context ID (CID) 1 is used in the Dial String, the modem will have to deregister from the network and register again before the PPP link can be established. This will automatically happen when the Modem Reset Timeout expires or after a power cycle of the device. Other PDP context identifiers do not require a re-registration of the modem after the authentication parameters are changed; in an LTE network, CID 1 is special as it is automatically activated on network registration and it is assigned the default EPS bearer. Usually it's not recommended to update this context unless explicitly required by the mobile network operator.

Please note that some mobile operators, especially in private APN subscriptions, do not allow activating more than one PDP context so for LTE networks CID 1 should always be preferred.

Cellular Linux Configuration

This section describes the changes applied by ESF at the Linux networking configuration. Please read the following note before proceeding with manual changes of the Linux networking configuration.

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Avoid Conflicting Configuration Changes

Eurotech does NOT recommend performing manual editing of the Linux networking configuration files when the gateway configuration is being managed through ESF. While Linux may correctly accept manual changes, ESF may not be able to interpret the new configuration resulting in an inconsistent state.

When the cellular configuration is submitted, ESF generates peer and chat scripts used by the PPP daemon to establish a PPP connection. Examples of these scripts for HSPA and EVDO modems are shown below.

Example Peer Script for HSPA Modem

921600
unit 0
logfile /var/log/HE910-D_2-1.5
debug
connect 'chat:v:f /etc/ppp/scripts/chat_HE910-D_2-1.5'
disconnect 'chat:v:f /etc/ppp/scripts/disconnect_HE910-D_2-1.5'
modem
lock
noauth
noipdefault
defaultroute
usepeerdns
noproxyarp
novj
novjccomp
nobsdcomp
nodeflate
nomagic
idle 95
active-filter 'inbound'
persist
holdoff 1
maxfail 5
connect-delay 1000

Example Chat Script for HSPA Modem

ABORT	"BUSY"
ABORT	"VOICE"
ABORT	"NO CARRIER"
ABORT	"NO DIALTONE"
ABORT	"NO DIAL TONE"
ABORT	"ERROR"
""	"+++ath"
OK	"AT"
OK	AT+CGDCONT=1,"IP","c1.korem2m.com"
OK	"\d\d\d"
""	"atd-99---1#"
CONNECT	"\c"

Example Peer Script for EVDO Modem

921600
unit 0
logfile /var/log/DE910-DUAL_1-1.5
debug
connect 'chat:v:f /etc/ppp/scripts/chat_DE910-DUAL_1-1.5'
disconnect 'chat:v:f /etc/ppp/scripts/disconnect_DE910-DUAL_1-1.5'
crtscts
lock
noauth
defaultroute
usepeerdns
idle 95
active-filter 'inbound'
persist
holdoff 1
maxfail 5
connect-delay 10000

Example Chat Script for EVDO Modem

ABORT	"BUSY"
ABORT	"VOICE"
ABORT	"NO CARRIER"
ABORT	"NO DIALTONE"
ABORT	"NO DIAL TONE"
ABORT	"ERROR"
""	"+++ath"
OK	"AT"
OK	"ATE1V1&F&D2&C1&C2S0=0"
OK	"ATE1V1"
OK	"ATS7=60"
OK	"\d\d\d"
""	"atd#777"
CONNECT	"\c"