1.661 TX-Channel

The TX-Channel logical device controls some parameters of an encoder / modulator / power amplifier transmit chain from a common channel database. The device complements the RX-Channel logical device which provides a similar function for receive chains.

TX-Channel supersedes the TX-LineSettings-CDB device, which no longer should be used for new applications. The TX-Channel device supports a larger number of parameters, may be used in M&C and in NMS environments and it supports an alternative operation mode / work flow. The name TX-Channel reflects that the set of parameters managed by the device extend the standard channel parameters.

Heart of the TX-Channel device is a central database (CDB) storing the line settings for all satellite channels used in the system. In a NMS environment the database is located in the NMS server, providing an synchronization mechanism which creates local (read-only) copies of the database for offline operation of the VLCs. In a NMS environment, the sat-nms client software looks up the channel lists directly at the NMS database server which significantly reduces the amount of data which has to be exchanged between NMS and VLC. In a M&C environment the CDB is located at the M&C server, no synchronization is required in this case.

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 .

• --- The main control (channel select) page for the device.
• --- The channel database editor page.
• --- The fault page. There is one fault signal the device (optionally) monitors, this fault is reported as "TX Chain" fault.
• --- The device info page.
• --- The maintenance page. The configuration parameters from this page are described below.

Operation (channel select)

The TX-Channel device supports two different operation modes / work flow settings which are selected by the 'workflowMode' configuration parameter.

With 'workflowMode=FILTER-BY-CHANNEL' (the default mode) the 'channel' field always shows all line settings data records. The auto-filter mode of the drop down box helps to find the desired satellite channel. Selecting a channel means to set all transmit parameters, the polarization switch and (if configured) also the antenna pointing from the satellite name stored with the selected data record. This operation mode may be used in M&C and NMS environments as well. Optionally, a switch matrix port may be controlled in this mode and the LO frequency may be automatically changed depending on the signal routing.

With 'workflowMode=FILTER-BY-SATELLITE', the 'channel' field only shows the channels of the satellite the antenna actually is pointed to. To move the antenna to another satellite, either the 'satellite' field in the TX-Channel's device screen may me used or the antenna may be controlled via it's own screen. Changing the antenna pointing automatically changes the subset of satellite channels displayed in the 'channels' field. This operation mode is only possible in M&C environments.

The FILTER-BY-SATELLITE mode provides a locking mechanism which permits to lock the settings of the transmit chain and the pointing of the antenna while the transmission is running. The locking mechanism is coupled to that one of RX-Channel devices working in FILTER-BY-SATELLITE mode as well. This means, locking the antenna for a transmission also locks the antenna pointing for all RX-Channel devices.

The TX-Channel device manages a number of transmit parameters, sets these parameters at the encoder, modulator etc. when a channel is selected. The following parameter may be managed by the TX-Channel device:

• txFrequency
• polarization
• symbolrate / bitrate
• dvb mode
• roll off
• pilots
• modulation
• packet size
• mpeg frame size
• video data rate
• video profile (see below)
• video coding format / profile
• nominal eirp
• reduced eirp for lineup
• audio data rate (1)
• audio data rate (2)
• audio data rate (3)
• audio data rate (4) For an installation of the software not necessarily all of these parameters are available. The TX-Channel device may be configured to ignore some of these parameters.

Please note, that the TX-Channel device neither sets nor clears the TX-ON state of the equipment. The operator is responsible to switch off the transmission before applying a satellite channel data record and also to perform the line up procedure as specified. The LineUp-Control logical device may be used to support the operator with this task. With the LineUp-Control device, the nominal and reduced eirp values from the database are set at this device rather than at the equipment itself. The operator then easily can set the transmit power values required during the line up procedure.

Instead of selecting the satellite and channel you also may enter the transmit parameters at the fields of the device screen. The TX-Channel device forwards these settings to the ancillary devices.

Output switching and LO calculations

When operated in 'workflowMode=FILTER-BY-CHANNEL', the device may control an input port of a combining matrix which routes the signal to a certain transmit chain. With the frequency range and LO frequency data defined in a configuration file, the device only offers the output routes which are valid for the selected transmit frequency. The LO frequency defined for the selected route is applied automatically to the transmit frequency and the frequency setting at the modulator is updated every time the output route changes.

To use this feature, the setup parameter 'config.switchId' must be set to the control parameter of the matrix input to use and a configuration with the frequency range and LO frequencies for all routes must be supplied (the format is described some paragraphs below).

Video profiles

The line settings database contains a parameter called "profile" which controls the basic video encoding mode for the encoder device. This profile contains the MPEG-2 / MPEG-4 selection, the MPEG profile/level and the 4.2.0/4.2.2 color subsampling setting.

Most video encoders don't provide a single parameter to set these values, but use several settings which may differ in name and values they offer to select. To overcome these differences, the TX-Channel device can use special device presets to set the profile parameter in a way individually specialized for the type of video encoder.

To use this feature, store device presets for the profiles you need. Each preset must be named exactly as the profile selection in the channel database (e.g. 'MPEG4-MP@HL-420'). The presets stored for this purpose should be edited in a way, that all parameters which could interfere with other database settings are removed, leaving only the parameters in the preset which set the profile properties.

Then configure the TX-Channel device to route the profile parameter ('profileId' configuration parameter) to the 'applyPreset' parameter of the encoder (e.g. 'ENC.applyPreset'). The TX-Channel device will apply the appropriate device preset when a channel from the database is selected.

Operation (database edit)

With the second page of the device window of the TX-Channel device channel definitions are edited, copied or deleted. All TX-Channel devices in a sat-nms NMS share one common channel database located at the NMS server. The VLC containing the TX-Channel device requires an online connection to the NMS central database in order to make any changes to the database. Selecting channels at this page or changing any channel parameters do not change the equipment settings.

• Change certain parameters of a channel:
  1. Select the channel to modify
  2. Edit the settings
  3. Click 'SAVE'Please note that if you change the channel name (composed of the satellite / channel id entries), this will store a new channel definition with the modified data, the old channel is kept unchanged in the database.The channel name may consist of letters (a-z, A-Z), digits, space characters and some punctuation characters (,.-_). All other characters are turned to underscore characters when the channel gets stored.
• Save the actual receive settings as a new channel:
  1. Click 'READ' to fill the fields from actual receive settings.
  2. Optionally complete the transmit parameters for the channel.
  3. Enter the desired satellite / channel name.
  4. Click 'SAVE'
• Delete a channel:
  1. Select the channel to delete
  2. Click 'DELETE'

Local database copy

The following paragraph only applies to NMS installations. M&C installation manage their CDB locally at the M&C server and do not require a local copy of the data.

sat-nms VLCs may be operated locally by connecting an M&C client directly to the VLC. This may be used as a backup operation mode in cases where the NMS server is down or unreachable. To uphold the TX-Channel functionality even in this backup case, the VLC maintains a local copy of the channel database. This copy is used if the CDB at the NMS is unreachable. You cannot edit the channels in this local backup copy, but you can apply stored channels to the IRD.

There are two ways to update the local copy of the channel database at the VLC:

1. At the "Database" page of the device window of a TX-Channel device click "VLC UPD". This requests the complete database contents from the NMS server and stores it locally.
2. Administrators may configure a VLC to update the local database copy in regular intervals. To make a VLC update it's local database copy automatically, add a line cdb.channels.syncInterval=#.# to the file vlc.properties and restart the VLC. '#.#' is the time interval in hours.

EBU DREAMS channel list import

The channel database is capable to import channel lists from the EBU DREAMS software. The DREAMS channel lists are distributed as two CSV tables, on for RX and one for TX. In the sat-nms channel database these lists get merged. EBU channels are marked "read-only" in the database, they only may be changed by importing a new EBU channel list.

To import a pair of EBU channel lists, click the "IMPORT" button at the "Database" page of the TX-Channel device's device screen. This opens a new window where the names of the files to import must be entered. The small buttons beside the file name entry fields open a file select dialog which lets you select the file names fom the directory.

After you have set the file names, click "READ". The software reads and parses the CSV files. It also matches corresponding RX and TX channels, because the sat-nms channel database stores only one entry for each channel containing both, the RX and TX parameters.

The software reports the number channels read from each file and the number of channels matched. Sometimes the numbers slightly differ, e.g. if the original channel names in the RX and TX lists are not really identical. You have to edit and repair the original files if you want to fix this.

If you are satisfied with the parsing result, click "IMPORT". This imports the channel definitions to the sat-nms database. All existing EBU channel definitions are deleted and replaced by the new ones. The user defined channels in the database remain unchanged by this.

Please note, that this procedure copies the EBU channels directly from the client PC to the NMS server, the TX-Channel device is not involved in this and does not recognize the new channels immediately. This happens with the next regular update of the channel list, max 5 minutes later.

Configuration parameters

At the maintenance page of the device window there are a couple of configuration parameters which must be set to interconnect the TX-Channel device with the transmit equipment.

Configuration file format

The TX-Channel's configuration file is a plain text file which defines the matrix / signal routing assignments. As this is a system wide assignment, you usually will edit one common configuration file for all TX-Channel devices connected to one output matrix.

In the file all empty lines and lines starting with a '#' character are ignored. All other lines are treated as table rows where the cells are separated by space characters. Each row describes one matrix input as follows:

Example:

#
#  tx switch matrix example file
#
#  matrix port                       low band edge
#  |     name           LO frequency |           high band edge
#  |     |              |            |           |
   01    UPC1-Ku        13000.0      14000.0     14500.0
   02    UPC2-Ku        13000.0      14000.0     14500.0
   03    UPC3-Ka1       26550.0      27500.0     28250.0
   04    UPC4-Ka2       27150.0      28100.0     28850.0
  

The TX-Channel device parses this file on startup and when it receives a new name for the configuration file. So when you change the configuration file in the running M&C system, the best way is to restart the M&C server process to make all devices read the configuration file again.

Variables defined by this device driver