1.586 SCC-Device

The SCC-Device logical device manages the equipment which is necessary to let the NMS control a VLC via SCC (Satellite Control Channel). In each SCC controlled VLC there must be exactly one SCC-Device, this device must be named SCC .

In the simples case, the SCC-Device controls the satellite modem which implements the physical data link to the NMS. The SCC-Device als is prepared to manage more complex equipment setups where additional equipment like frequency converters or power amplifiers are involved in the reception or transmission of the SCC signals.

Even though not mandatory, it makes sense to give the modem used for SCC the same name on every VLC. E.g. the recovery macro described at the bottom of this chapter may be identical for all VLCs if the devices are named the same.

Device window pages

The following table shows which device window pages are available with this individual device type. Tool-bar functions not mentioned here are described at the general description of device windows .

• --- Shows the actual control channel state. When viewed from the NMS, one always will see 'receiving data from the NMS' marked green. Using a client which is directly connected to the VLC via Ethernet, the state of the connection to the NMS can be monitored by means of this display.
• --- The faults page. The SCC-Device only knows a 'communication fault' which signals that the heartbeat messages from the NMS are missing.
• --- The device info page.
• --- The maintenance page. The configuration parameters described below are set at this page.

Configuration parameters

The table below explains the configuration parameters which interconnect the SCC-Device to the devices it monitors / controls. Unused parameters should be left empty.

• parameter --- description
• txOnId --- The parameter ID used to switch the SCC carrier on/off which VLC transmits during a point to point connection. Usually something like 'SCC-MODEM.tx.on'.
• txPwrId --- The parameter ID of the setting which controls the transmit power while the VLC transmits an SCC signal. Example: 'SCC-MODEM.tx.power'.
• txPwrCal --- In the NMS, the definition of the SCC inbound channel the VLC uses contains the transmit power expressed as EIRP (dBW). As the 'txPwrId' usually sets a modem output level, the 'txPwrCal' is used to convert these values:
  • If the SCC-Device directly controls a modem output level, set the 'txPwrCal' value to the EIRP (dBW), the VLC (theoretically) transmits with the modem output level set to 0 dBm.
  • If the SCC-DEvice is configured to set the transmit power through a 'Level-Control' or a 'Level-Set' logical device, set 'txPwrCal' to zero and configure the EIRP calibration in the device controlling the power.
• txDataRateId --- The parameter ID of the setting which controls the transmit data rate of the inbound data stream. Example: 'SCC-MODEM.tx.mod.dataRate'.
• txFrequencyId --- The parameter ID of the setting which controls the transmit frequency. Example: 'SCC-MODEM.tx.frequency'.
• txFrequencyOffs --- The 'txFrequencyOffs' value gets subtracted from the SCC channel transmit frequency to achieve the frequency set at the modem. If you set the frequency through a 'Frequency-Split' logical device rather than controlling the modem directly, set this value to zero and let the Frequency-Split device manage the frequency offsets.
• rxDataRateId --- The parameter ID of the setting which controls the receive data rate of the outbound data stream. Example: 'SCC-MODEM.rx.dem.dataRate'.
• rxFrequencyId --- The parameter ID of the setting which controls the receive frequency. Example: 'SCC-MODEM.rx.frequency'.
• rxFrequencyOffs --- The 'rxFrequencyOffs' value gets subtracted from the SCC channel receive frequency to achieve the frequency set at the modem. If you set the frequency through a 'Frequency-Split' logical device rather than controlling the modem directly, set this value to zero and let the Frequency-Split device manage the frequency offsets.
• timeout --- If the SCC-Device does not recognize the NMS' heartbeat for the time specified here, it assumes that the channel is down and starts to scan the two outbound channel definitions it received from the NMS.

Recovery through macro

If the SCC-Device misses the heartbeat messages from the NMS, it scans the two OUTBOUND channel definitions it did receive from the NMS before. Before setting the frequency and data rate defined for a channel, the SCC-Device checks if there is a macro called 'scc-recovery' in the 'macros' subdirectory. If such a macro is present it gets executed before the channel frequency and data rate is set.

Such a recovery macro should contain all device settings necessary to receive the NMS' outbound channel. Beside general modem settings this macro may include the position of waveguide switches, the frequency setting of a downconverter or other parameters. It however must not contain a command which switches on the SCC carrier in the VLC.

If a parameter the VLC requires to receive the NMS outbound channel gets displaced by accident, the communication with the NMS immediately breaks down. This mistake cannot be undone via SCC as the VLC does not receive any data from the NMS. If this parameter is backed up in the scc-recovery macro, the SCC-Device successfully will reinitialize the communication equipment during the recovery / channel scanning process.

A recovery macro gets recorded like any other macro while the VLC is 'online'. The Macro Management window provides a particular toolbar button which lets you store a macro as a scc-recovery macro on the VLC with a single mouse click.

Variables defined by this device driver