VoIP Air Traffic Management Test Solutions

Welcome to another edition of GL's Newsletter providing information on our Air Traffic Management (ATM) test solutions that rigorously test Analog, TDM, Ethernet and IP communications networks.


Traditional ATM is migrating from Analog/TDM to IP-based voice communications and control. This transition takes many years to safely cutover and the new technologies must be rigorously tested prior to deployment on operational Air Traffic Communications networks.

GL offers cutting edge solutions for testing next generation ATM networks. This includes the ability to emulate and load test equipment such as Controller Working Positions (CWP), Voice Communication Systems (VCS), Ground Radio Stations (GRS), Analog-to-IP converters, Gateways, and more. Components can be accurately tested for timing, performance, and functionalities. The GL test tools for next generation ATM offer signaling and traffic emulation per the ED-137 standards, monitoring the quality of service per ED-138, and providing critical network delay and voice quality measurements.

GL's ED-137 and ED-138 Voice over IP Test Tools have been widely welcomed by Global Air Navigation Service Providers and VCS/Radio/Gateway/Recorder companies who have found them to be essential tools during development, functionality testing, performance testing, factory acceptance testing, deployment and field testing.

Measuring the delay in hybrid ATM networks is critical to ensure clear and quick communication between air traffic controllers and pilots. Recognizing, capturing, timestamping, and correlating events at Analog, TDM and IP interfaces are necessary. Delay measurements should be conducted repeatedly to ensure that the device and network under test is performing consistently over time.

GL has developed Timing Measurements in Air Traffic Management (TM-ATM) test suite to accurately emulate end points in ATM networks and provide critical timing measurements for various types of delay occurrences in signaling and voice transmission through the network. It includes all necessary hardware and software to identify, capture, timestamp, and correlate events at Analog, TDM and IP interfaces.

TM-ATM Solution for Timing Measurements

TM-ATM Solution for Timing Measurements

TM-ATM Solution is a custom suite of test tools designed to accurately measure various types of delay occurrence in signaling and voice transmission. It includes all necessary hardware and software to identify, capture, time stamp, and correlate events at Analog, TDM and IP interfaces.

Important applications of TM-ATM are:

  • Delay measurements for:
    • Push To Talk (PTT), PTT confirmation, PTT release, PTT release confirmation
    • Squelch on/off
    • End-to-end voice delay for PTT, and Squelch
    • Main/Standby Tx/Rx transfer
    • Main/Standby Tx/Rx transfer confirmation
    • Remote Receiver Mute/ Unmute
    • Remote Receiver Mute/Unmute Confirmation
  • Supports for end-to-end Voice Quality measurement using industry standard ITU algorithms (PESQ and POLQA)
  • Measure consistency and reliability by doing multiple iterations
  • Load testing can be performed on air to ground and ground to ground by generating hundreds of calls to achieve the required Peak Busy Hour and Peak Busy Minute loads

Key features include:

  • Centralized control and reporting of the tests
  • Ability to interface with Analog, TDM and IP based systems
  • Customize test suite to measure delay and voice quality across Analog to/from IP, Analog to/from Analog, and IP to/from IP
  • Automated tests to run multiple iterations for accuracy and consistency
  • Timing accuracy using different clock sources - Local clock, GPS, Master and Slave
  • GPS mode is suitable for field testing
  • Local/Master/Slave modes are suitable for Lab testing
  • Supports audio/tone transmission and recording
  • Outputs routable packets for field testing
  • Up to 32 hardware-based filters for wirespeed filtering
  • Each filter is 120 bytes User defined Raw hex filter
  • Each filter works in trigger mode for filtering a single packet
  • Flexible filters for complex filtering
  • Supports Voice detection in IP packets and Voice Delay calculation
  • End-to-end voice quality using ITU-T standard algorithms (POLQA)
  • Measured delays for every iteration are logged to CSV file

GL's solutions includes rack mount and portable hardware equipment deployed across the Air Traffic Management network. These include:

  • MAPS™ Administrator:
    • Controls all the components of TM-ATM test suite and runs the tests to perform measurements
    • Calculates the time difference between posted events and reports the precise one-way delay at different points in the network
    MAPS™ Administrator
  • MAPS™ ED-137 Radio Emulator:
    • Emulates Air-Ground calls (as per ED-137), and multiple CWPs or GRSs
    • Can emulate PTT/Squelch, send and record audio to perform end-to-end voice delay and quality measurement
    • Emulates all radio events such as Main/Standby Tx Rx switching, Mute/Unmute Receiver etc.
    MAPS™ ED-137 Radio Emulator
  • Packet Analyzer:
    • Deployed in-line on an Ethernet network. Timestamps packets as they pass through using GPS. Filters can be defined for which packets to timestamp and copy the packet out through the Drop Port
    • Packet filtering can be based on Layer 2 (Ethernet), Layer 3 (IP), and Layer 4 (UDP/TCP) headers
    • Can generate TTL triggers (1 Microsecond pulse) for each filter passed
    • Can be controlled remotely and provides Command Line Interface/Application Programming Interface for automation
    Packet Analyzer
  • 2-Port Audio Analyzer:
    • Emulate Controller (PTT and Audio); Generates TTL triggers based on PTT On, PTT Off, Audio Start and Audio Detect (on or off)
    • Inject and record analog signals at the CWP/VCS, Radio and VoIP gateway interfaces
    • Can be controlled remotely and provides Command Line Interface/Application Programming Interface for automation
    2-Port Audio Analyzer
  • Event Data Logger:
    • Receives events from the Packet Analyzers with GPS timestamping
    • Processes received events, sends notifications to the MAPS™ Administrator
    • Detects audio in RTP packets to identify the beginning of voice in the stream
  • Discrete Signal Logger w/96 Ports:
    • Monitors IO channels of the Sensoray for low-to-high and high-to-low transitions
    • Used to filter and forward desired events/frames
    • Filters can be applied to port #2 and port #3 (16 filters available on each port). Each filter is 40 bytes in length and filtered frames are sent out on port #1
    • Monitors TTL output from the Audio Analyzers and Packet Analyzers and generates a corresponding IP packet to send to the Event Data Logger
    Discrete Signal Logger w/96 Ports
  • Voice Quality Testing Software: This software performs end-to-end voice quality assessment using industry standard ITU algorithms (PESQ and POLQA) across the ATM network.

Below is a typical Air Traffic Management network showing the role of emulators and analyzers. We emulate air-to-ground, ground-to-ground, and recorder interfaces as per ED-137 standards. All IP traffic can be monitored using PacketScan™ and analyzed either locally or remotely using NetSurveyorWeb™ applications.

Voice Quality Testing Software

In the sections below we briefly discuss our emulators and analyzers used for testing VoIP based ATM network and equipment.

MAPS™ ED137 Radio emulates air-to-ground calls by emulating either CWP/VCS or GRS. MAPS™ emulator supports both version B and C of ED-137 volume 1 Radio. Hundreds of CWPs or Radios can be emulated and can generate bulk air-to-ground calls using a single instance/license. Can be used to test functionality and performance of CWP, VCS, GRS and Radio Gateways. MAPS™ ED137 Radio is validated against VOTER versions and volumes for GRS and VCS Radio ED137/1C compliance.

MAPS™ ED137 Telephone emulates ground-to-ground calls by emulating CWP/VCS. Supports both version B and C of ED-137 volume 2 Telephone. Hundreds of CWPs can be emulated and can generate bulk ground-to-ground calls using a single instance/license. Can be used to test functionality and performance of CWP/VCS. Validated against VOTER_4.1.30.3 for VCS-Telephony-Interface-Test cases.

MAPS™ ED137 Recorder emulates Recorder interface at VCS, GRS and Recorder server as per version B and C of ED-137 volume 4 Recorder. Can be configured as either CWP or GRS or Recorder to emulate recorder interface at that node. Hundreds of CWP/GRS/Recorders can be configured to emulate bulk Recording sessions.

PacketScan™ is an all-IP Network Monitoring software, which offers powerful features to capture and monitor A-G and G-G calls in the ATM network. The application can capture, segregate, monitor and collect statistics such as Packet loss, delay, jitter and MOS scores on all the captured calls. It can also act as a probe in the network and send Call Detailed Records to a centralized database to facilitate centralized and remote monitoring of the probes/network.

NetSurveyorWeb™ is a web-based client application, which facilitates real-time data display, navigate through historical records, filter the collected VoIP traffic summary, and graphically analyze the Call volume, Mean Opinion Score (MOS), Packet loss, Failed calls, Completed calls, Post Dial Delay, and more. Generates alarms and e-mail notifications to report configured failures in the network. NetSurveyorWeb™ Lite version can be deployed on the Probe (PacketScan™) system with limited database (of 9 GB storage) on the same system.

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