Aeronautical Ground Data Unit (GDU)

Square Peg Communications Inc.’s Aeronautical Ground Data Unit (GDU) is a software application that runs on the generic Physical Layer Tester (PLT) platform. The GDU supports the testing of physical layer performance and protocol operation for Ground Earth Stations (GESs) and Aeronautical Earth Stations (AESs) implementing Inmarsat Aero services.

The GDU supports all of the Classic Aero channel types and also implements the Inmarsat Aero link layer. Interfaces are provided for external devices, including codecs, to be connected through the GDU to the equipment under test.

The GDU can run autonomously under external control. Alternatively a familiar Windows based user interface provides easy access to test functions. A powerful scripting language allows every feature of the GDU and equipment under test to be exercised in automated test cases and suites.

A complete set of Inmarsat AATS scripts is available, eliminating the requirement for a separate Micro-VAX. Scripts are also available to automate physical layer testing. For testing of normal operation and end-to-end connectivity, a GES emulator is also available.

  • Key Features

    General

    Integrates with legacy Inmarsat Access Approval Test System for link layer and network layer testing of AESs.
    Protocol Testing can also be performed using only the GDU.

    Compatibility

    Drop in replacement for TRL and SkyWave Ground Data Units

  • Transmit Capabilities

    Modulators

    1 - 5 simultaneous (1 – 4 on PLT-H platform)

    Channel Types & Rates

    P, R and T Channels:
    600, 1200, 2400, 4800 and 10,500 bps
    C Channels:
    8400 and 21000 bps

    Channel Impairments

    Independently-specifiable parameters:

    • Fixed carrier frequency error
    • Doppler rate, peak offset
    • Reacquisition carrier offset
    • Adjacent channel interference level and frequency offset
    • Co-channel interference level
    • I/Q gain and phase imbalance
    • Continuous phase noise spectrum, level
    • Discrete phase noise level
    • Fading model, bandwidth, C/M ratio, differential delay
    • Phase/amplitude jump distribution, magnitude, interval
    • Transmission path delay
    • Symbol rate error
    • HPA non-linearity
    • AWGN

    Link Layer

    Embedded implementation of Aero Link Layer

    Receive Capabilities

    Demodulators

    1 - 5 simultaneous (1 – 4 on PLT-H platform)

    Channel Types & Rates

    P, R and T Channels:
    600, 1200, 2400, 4800 and 10,500 bps
    C Channels:
    8400 and 21000 bps

    Link Layer

    Embedded implementation of Aero Link Layer

    Ethernet Interface Capabilities

    Medium

    10/100BaseT

    Functionality

    GESTE interface, remote control interface, GPIB interface (with Ethernet-to-GPIB converter)

    Serial Interface Capabilities

    Medium

    RS-232

    Functionality

    GESTE interface, AES control interface

    Avionics Interface Capabilities

    Medium

    ARINC-429 (with PCI ARINC-429 card)

    Functionality

    Label transmission / reception, Williamsburg bit-oriented protocol file transfer

    Logging Capabilities

    General

    GESTE interface messages
    Transmitted/received SUs
    Test sequence progress and outcome
    System events, faults, and abnormal conditions

    Script Capabilities

    General

    Procedure-based (like Basic, C or Pascal)
    Functions for string processing, math, user interaction, logging, I/O (serial, TCP/IP, GPIB)
    Integrated development environment

    GDU-specific

    Configuring and controlling modems
    Flexible definition of SU formats
    Formatting and sending SUs
    Receiving SUs
    Sending and receiving link layer LSDUs
    Generating signal blockage events

  • GDU Data Sheet

    GES Emulator Data Sheet

  • Physical Layer Tester (PLT-H) Physical Layer Tester (PLT-L)

    MSS L-band Radio Frequency Unit (RFU)

    ATC Interface Unit (AIU)

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