Welcome to another edition of GL’s Newsletter providing information on our Air Traffic Management (ATM) test solutions that facilitate the transition of technology and services from traditional analog/TDM to IP-based Voice Communications Systems.

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Overview

Traditional ATM is migrating from analog/TDM to IP-based voice communications and control. The migration transitions to an improved, optimized, and integrated communications test beds. Automated functional and performance testing are valuable and help accelerate the deployment of next generation ATM equipment and services.

GL offers standardized, portable, and high throughput/high density solutions for testing next generation ATM networks. This includes ability to simulate all entities, from Radio interfaces to the Controller Working Positions (CWPs), and measure network response times, delays, and load conditions.

The migration to Voice over Internet Protocol (VoIP) poses challenges, which requires a customized test solution. The ATM core network and all its underlying entities (CWP/VCS, GRS, Radio Gateways and Recorders) can be accurately tested for timing, performance, and functionalities. The GL test tools for next generation ATM offer signaling and traffic simulation per the ED-137 standards, monitoring quality of service per ED-138, and provide critical network delay and voice quality measurements.

Our 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 alike, who have found them to be essential tools during development phase, functionality testing, performance testing, Factory Acceptance Test phases, deployment phase, and 'in-the-field' testing.

Measuring the delay in hybrid ATM network is critical and needed to precisely measure the delay introduced by each network element as events propagate end-to-end. 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 as expected consistently over time.

To counter this issue GL has developed TM-ATM (Timing Measurements in Air Traffic Management) test suite to accurately simulate end points in ATM network 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.

Fig. 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 can be measured for
• 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)
• We can measure the 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

Salient features of TM ATM are

• 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 of 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 VoIP ATM Test Solution includes rack (suitable for lab testing), and portable (suitable for field testing) hardware units deployed across the Air Traffic Management network, which are briefly discussed below -

• MAPS™ Administrator: -
• It is a client application that controls all the components of TM ATM suite and runs the tests to perform measurements
• It Calculate the time difference between posted events from the Discrete Signal Logger and Packet Analyzer and reports precise measured delay at different points in the network.

• MAPS™ ED137 Radio Emulator: -
• Simulates Air-Ground calls (as per ED-137), and multiple CWPs or GRSs
• Can simulate PTT/Squelch, send and record audio to perform end-to-end voice delay and quality measurement
• Simulates all radio events such as Main/Standby TxRx switching, Mute/Unmute Receiver etc

• Packet Analyzer: -
• Filter packets of interest on multiple ports with 120-byte depth filters. Define what byte(s) of interest to be filtered at hardware-level
• Packet filtering can be based on all Layer 2 (Ethernet), Layer 3 (IP), and Layer 4 (UDP/TCP) headers
• Capable of routing filtered packet with GPS time stamp or generate TTL triggers (1 Microsecond pulse) for each filter passed
• Automation with other GL test solutions and CLI/API access for seamless integration with 3rd party test tools

• 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
• Automation with other GL test solutions and CLI/API access for seamless integration with 3rd party test tools

• Event Data Logger: -
• Software EDL receives events as tunneled IP packets with filtered packet and GPS timestamp
• EDL processes received events, sends notification for events to MAPS Administrator
• Supports detection of audio in RTP packets to identify the begin of voice burst in the stream



• Discrete Signal Logger w/96 Ports: -
• Used to monitor 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 Audio Analyzer and Packet Analyzer and generate corresponding IP packet

Packetizer: - works in tandem with the Audio Analyzer to convert analog events into packet events. The Packetizer monitors the TTL output from the Audio Analyzer, and for every trigger pulse received, it generates and transmits a timestamped IP packet.

• Voice Quality Testing (VQT): -The 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 simulate air-to-ground, ground-to-ground, and recorder interfaces as per ED-137 standards. Complete network can be probed using PacketScan™ and analyzed either locally or remotely using NetSurveyorWeb™ applications.

In the below section we will briefly discuss our emulators and analyzers used for testing VoIP based ATM network and equipment’s.

MAPS™ ED137 Radio simulates 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 simulated 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 4.1.30.1 and 4.1.30.2 volumes for GRS and VCS Radio ED137/1C compliance.

MAPS™ ED137 Telephone simulates 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 simulated 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 is used to simulate Recorder interface at VCS, GRS and Recorder server as per version B and C of ED-137 volume 4 Recorder. MAPS™ emulator can be configured as either CWP or GRS or Recorder to simulate recorder interface at that node. Hundreds of CWP/GRS/Recorders can be configured to simulate 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, MOS (Mean Opinion Score), 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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