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Application Note

Using ASTi's Tactical Data Link/Data Bridge Feature (#26.1)

Part I (DACS Model Builder & Telestra 2)

Equipment Required

  • Model Builder (MB) version 3.12 or later.
  • Tactical Data Link, DIS and Radio options enabled (MB version 3.12).
  • 1500 credits to support the Tactical Data Link feature (MB versions 4.01 - 4.04c)
  • 500 additional credits for each radio that will support the Tactical Data Link feature (MB versions 4.04d or later)
  • Digital Audio Communications System (DACS) with both Host and DIS Interface cards installed (DIS network)
  • DACS with Host Interface card and Telestra (HLA network)

NOTE: Model Builder versions prior to 4.04b support only data transfer over the DIS network. When using versions prior to 4.04b refer to Part III of this document for instructions on how to transmit and receive TDL information between radios that are located on the same system.

Tactical Data Link/Data Bridge Overview

In its simplest terms, the tactical data is passed from the Host interface of one DACS to the Host interface of another DACS using the DIS network as a conduit.

NOTE: The following notes apply to using the Tactical Data Link over a DIS network. TDL may also be used to bridge data over HLA. Please refer to Part V of this document for detailed information on TDL and HLA.

A Host computer bundles the tactical data to be transmitted into a standard DIS Signal PDU (which also identifies the transmitting radio) and sends it to the DACS Host interface.

The Model Builder application software radio environment then transmits the Signal PDU onto the DIS network assuming the target radio is:

  1. Turned on with valid parameters such as frequency, modulation type, transmit power, etc.
  2. Actively transmitting
  3. For MB versions prior to 4.06A only: Configured properly for data transmission (in "digital" instead of "analog" mode).

Other DACS units connected to the DIS network that contain virtual radios may receive this data depending on the state of the receiving radios. In order for the radio to receive data it must be:

  1. Turned on with valid parameters such as frequency, modulation type, etc.
  2. In-tune, In-range of the transmitting radio
  3. For MB versions prior to 4.06A only: Configured properly for data reception (in "digital" instead of "analog" mode).

If the receiving radio meets these criteria, Signal PDUs are bridged from the DIS network to the local Host network and passed to the local Host.

Signal PDUs transferred via this process are unchanged by the DACS except for the Site, Host, Entity, and Radio IDs. These fields are modified at the receiving end to reflect the receiving system and radio IDs (i.e., the local host will not see the transmitter's ID string, but will instead see the receiving system's Site, Host, Entity and Radio IDs).

In addition, the applications software does not act upon or interpret any of the data embedded in the Signal PDU. The system is simply used as a transport mechanism through the radio environment. If necessary for the simulation, the virtual radios may also transmit tactical and voice data simultaneously.

Model Builder versions 4.04b and later also have the capability to bridge Receiver (RXer) and Signal PDUs to the Host Interface. It is useful to couple over the RXer PDUs because these PDUs contain the DIS information for the receivers on that platform, their state, the DIS information of in-tune transmitters, and the received signal strength from those transmitters. The receiver states are 0 = off, 1 = on and 2 = on and receiving. Bridging the signal PDUs over to the Host Interface is only used as a debugging tool, and should be used with a great deal of caution because there can be a tremendous amount of network traffic going to the Host due to these PDUs.

Manually Enabling the Data Bridge from the Model Builder Environment

It is recommended that the user have the Model Builder Reference Manual on hand when configuring objects in the MB environment. The Reference Manual has information regarding configuration of the Host and DIS interfaces.

  1. To enable the Host-DIS bridge in Model Builder, starting from the Main Model Page, go to:

    DIS network >> Options >> Signal PDUs

    and toggle the field from "Bridge Off" to "Bridge->Host".
    1. The field immediately to the right has the default value of "Data", leave this value as is if you only want to couple the data PDUs to the host.
    2. Use the arrow keys to highlight the "Data" field then use +/- keys to change to "Data+RX" if you want to couple the data and receiver PDUs to the host.
    3. Use the arrow keys to highlight the blank field next to the "Data" field and use the +/- keys to change the field from blank to "Voice". This sends the signal PDUs to the Host Interface for debugging as well as the communications model.
  2. To modify the TDL network settings, go to:

    DIS network >> Bridge

    NOTE: This menu option is available only if the TDL Bridge has been enabled in the configuration file (see below).

    Set the "DIS Ports" TX and RX values; ensure that the port numbers used are different than those of the Host Interface. The default values are as follows:

    6994 - MB versions prior to 4.06
    53100 - MB versions 4.06 and later

    You will see the "Local Address IP" is in yellow, indicating that it cannot be changed from this page. This value is a reflection of the Host Interface address.

    The "Broadcast PDUs IP" field sets the destination address for Signal PDUs bridged from the DACS to the Host. This field appears in blue, indicating that it can be changed from this page. The default value is

    Note that any changes made on this page will only apply for the current session. Once Model Builder is exited or the system is shut down, these settings will no longer be in effect. For permanent configuration, see next section "Enabling the Bridge in the Configuration File".

Enabling the Bridge in the Configuration File

  1. The configuration file command is DIS_BRIDGE = ON. If this field is set, then step 1 in the above section is not necessary.
    1. The configuration file must include the DIS = ON command. This command MUST precede the DIS_BRIDGE = ON entry (i.e., there is an order dependency for these commands). Failure to follow this command order can result in failure of the TDL bridge.
    2. To couple the both receiver and data PDUs to the Host, use the configuration file command: DIS_BRIDGE=Data+RX. The data PDUs, when present, are automatically coupled over when the bridging option is enabled.
    3. To couple over the signal PDUs for debugging purposes, use the configuration file command: DIS_Bridge=Data+Voice.
    4. To couple over all 3, use the configuration file command: DIS_BRIDGE=DATA+RX+Voice, in that order.

  2. The default IP address for all packets bridged from the DIS network is broadcast to IP address To modify this, use the command DIS_BRIDGE:TX_BROADCAST_IP = xx.xx.xx.xx, where xx.xx.xx.xx is the desired destination IP address.

  3. If you want the default port numbers to be something other than the default value, the configuration file command is DIS_BRIDGE:UDP_PORT = xxx, where xxx is the desired port value.

Configuring the Radio Object for Data Transmission

  1. To actively transmit data through the radio, toggle the "Data Signal TX" field on page 1 of the Radio Object from "Off" to "On".

    If the radio was not transmitting, the words "Active TX" would appear in yellow in the lower right hand corner of the Radio Object when transmission was enabled. If the radio was already actively transmitting voice data when the Data Signal TX field was toggled, then the tactical information would be transmitted along with the voice signal.

    Note that the Data Signal TX enable has a field where a Control Object could be inserted. The Control Object provides for local or remote toggling of the data transmission feature.

    NOTE: In MB versions 4.09 and later, the radio object includes a "TX VoiceLockout" field. When this field is set to "On", the radio will prevent a voice signal from being transmitted while the Data Signal TX field is "On".

  2. For MB versions prior to 4.06A only: In order for the Radio Object to be capable of transmitting tactical data, the Voice field must be set to "Digital" for the corresponding mode number. The Voice field is found on page 4 of the Radio Object. Refer to the Model Builder Reference Manual for additional information on the radio types and modes of operation.

Configuring the Radio Object for Data Reception

  1. Set the Power/Mode field so that it matches the type of the transmitting radio.
  2. For MB versions prior to 4.06A only: Ensure that the receiving radio's Voice field is also set to "Digital".
  3. The receiving radio must be in-range of and in tune with the transmitting radio in order for communications to occur.
  4. When a radio is actively receiving, the site, host, entity number and ID of the transmitting radio are shown in yellow at the bottom of the Radio Object page.

Simulation Hint

Model Builder will allow the nearly instantaneous transmission of signal PDUs over the DIS network (within the constraints of the network). This may not be accurate for your simulation needs. It does not reflect the baud rate of the transmitting radio, nor does it reflect the length of the message sent. To create an accurate simulation, add a bit of delay into the model before sending the data, or the host could simply delay sending over the data once the radio has been keyed.

More importantly, to ensure that the data is sent in its entirety, pass the data from the host to the transmitting radio towards the end of the data transmission keying. Also, have the host key the radio for transmission several seconds before the data is sent from the host. This will permit the receiving radio to acquire the transmitting radio before the data is sent. Since the DACS sends the data all at once, have the host send the signal PDU near the end of the transmit key.

Timing Diagram