International Civil Aviation
Organization
ACP-WGM 10 WP-04
26/04/05
WORKING PAPER
AERONAUTICAL COMMUNICATIONS PANEL (ACP)
WORKING GROUP M-10
Montreal, Canada 23 – 26 May 2005
Agenda Item :
4
RESOLUTION OF VDL MODE -3 AMENDMENT PROPOSALS
FAA/NASA
Weather Information Communications
Flight Testing Via VDL Mode 3 Broadcast Service
Presented By:
Peter Muraca
FAA Technical Center
Atlantic City, NJ
USA
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Background

Air / Ground Weather Information System flight testing was conducted
between the FAA, NASA Glenn, and Rockwell Collins at the FAA Technical
Center on April 11 - 13, 2005. Weather products were transmitted via the VDL
Mode 3 Subnetwork [report available mid-June 05’].
 Laboratory Testing (over RF) Conducted March 7 - 10, 2005 [report available]
 Laboratory Testing (attenuated antennas) Conducted November 15 - 18, 2004
[report available]
Objective



Validate the effectiveness of using the VHF Digital Link (VDL) Mode 3
broadcast communications technology as a digital data link to transmit
weather information to the aircraft.
Demonstrate integration between the NASA Glenn Ground Server, Rockwell
Collins VDL Mode 3 avionics suite, and the FAA VDL Mode 3 Ground System
for this work effort.
Utilize the VDL Mode 3 Broadcast service as specified in RTCA DO-224b
(MASPS) and ICAO Doc 9805.
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Communication System - Architecture
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NASA Glenn - Components

Data Logger

Ground Server

TCP/IP client/server

UDP/IP client/server

Weather Product Generator
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Rockwell Collins - Components

VHF Digital Radio (VDR) –
VHF-2100

Communications
Management Unit
(CMU-900)


Gables Radio Tuning
Panel (RTP)

Multifunction Control
Display Unit (MCDU)
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FAA - Components

Radio Interface Unit (RIU)

Real Time Platform (RTPF)
 Voice Channel Module
(Vocoder for each of 4 TDMA
timeslots)

Multimode Digital Radio (MDR)
Transmitter & Receiver

Channel Simulator (RF Attenuated
Circuit)

Ground Network Interface (GNI)
 IP Connection to NASA GRC
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NASA Lear Jet
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Flight Path
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Flight Tracker
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Results to Date

Weather products were successfully broadcasted from the WINCOMM ground server via
the VDL Mode 3 ground station and displayed on the Rockwell Collins Avionics, such
products included:









Metars
Graphical Precipitation Maps
Depiction Maps
Icing Maps
Winds Maps
Turbulence
1k product transmission = 1.2 seconds
3k product transmission = 4.0 seconds
26k transmission product = 55 seconds
VDL Mode 3 simultaneous voice and data was successfully conducted.
WINCOMM weather products were successfully broadcasted continuously, during fiveminute increments, for Subnetwork load tests.
Larger file size (26,000 bytes) weather products were broadcasted from the WINCOMM
ground server to test data capacity (data limit, transmission reliability, and assembly of
product on the avionics). File transfers were successful.
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Products –
Uplink Broadcast via VDL Mode 3
Depiction Weather Product
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Products –
Uplink Broadcast via VDL Mode 3
Nexrad Weather Product
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Products –
Uplink Broadcast via VDL Mode 3
Icing Weather Product
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Products –
Uplink Broadcast via VDL Mode 3
Metar Weather Product
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Products –
Uplink Broadcast via VDL Mode 3
Winds Weather Product
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Products –
Request / Reply via VDL Mode 3
Turbulence Weather Product
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Observers and Participants
Representation

FAA Technical Center

NASA Glenn Research Center

Rockwell Collins

FAA Flight Safety

FAA Aircraft Certification

Electronic Navigation Research Institute (ENRI) [Japan]

FAA Program Office
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Backup Slide 1
VDL Mode 3 Ground Station functioned as the link between the airborne segment
and the WINCOMM ground server and all transmissions were attenuated via the
channel simulator.
The GNI interface provided a gateway to the NASA Glenn Weather Server. The GNI
also provided a user interface in which to control multiple RIU protocol engines.
Internet Protocol (IP) gateway was added to the WJHTC ground system GNI that
allowed for two data services including a broadcast service and a point-to-point
request/reply link to the airborne segment.
The IP protocol provided network connectivity between the GRC Server, GNI and
Airborne Segment.
User Datagram Protocol (UDP) was used to transfer unicast datagrams from the GRC
ground server to the Airborne segment. (The GNI gateway decoded the IP protocol
fields to determine if UDP was signaled). The Transmission Control Protocol (TCP)
was used to support a request and reply service from the airborne segment to the
WINCOMM ground server. (The GNI gateway decoded the IP protocol fields to
determine if TCP was signaled and sent appropriate signals to the RIU protocol
engine for further actions).
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Backup Slide 2

WINCOMM Server, GNI, and RIU are physically connected to a hub via Ethernet cabling
– Socket connection (TCP/IP) between GNI and WINCOMM server (port 5001) for message
throttle control
• GNI receives flow control data from the MDR via the RIU
– GNI configures Ethernet port for promiscuous mode which allows all Network Layer traffic to
be visible
– An Ethernet packet socket configured for IP frames is opened and a “bind” is performed with
the Ethernet port
• This allows GNI to “sniff” for any IP packet (TCP or UDP) with the WINCOMM Server as
the source address and the Aircraft as the destination
• IP frames are not effected
– This is important since we rely on the IP Network Layer to segment any messages
that are too large for VDL Mode 3 (> 922 Bytes) and then reconstruct them at the
destination address
• GNI routes the IP packets to the appropriate RIU
– GNI opens a TCP/IP socket (server) with the RIU (client)
• IP packets destined for the Aircraft are sent across this connection as the datagram
payload of the TCP packets
– RIU IP Layer removes TCP header
• This leaves the IP packet datagrams destined for Aircraft
– RIU adds DLS framing to the IP packet datagrams
– RIU interfaces with the VDL Mode 3 MDR over a high speed serial link
• Message is sent over this connection to the MDR
– VDL Mode 3 MDR transmits data
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Backup Slide 3

VDL Mode 3 MDR -> RIU -> GNI -> WINCOMM Server
– VDL Mode 3 MDR receives data
– VDL Mode 3 MDR interfaces with the RIU over a high speed serial link
• Message destined for the WINCOMM Server is sent over this connection
– RIU removes DLS framing
– RIU – GNI TCP/IP socket
• IP packets destined for the WINCOMM Server are sent across this
connection as the payload of the TCP packets
– GNI IP Layer removes TCP header
• This leaves the IP packet datagrams destined for the WINCOMM Server
– GNI opens a RAW socket configured to include an IP header
• This allows GNI to send the IP packets to the Ethernet port and not alter
the IP header
– GNI IP Layer directs packets to the WINCOMM Server

All weather PDUs are sent from the WINCOMM Server as UDP datagrams.

All weather PDU requests and turbulence test messages are sent to the
WINCOMM Server from the Aircraft as TCP datagrams.
– The WINCOMM Server replies with a simple TCP “ack”
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Backup Slide 4

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Turbulence data is generated from on-board avionics sensors, in this test
flight, the data was generated via on-board computer.
Data collected is sent to the NASA ground server via TCP/IP over VDL
Mode 3 subnet
Ground server composes graphical Turbulence graphical product and
delivers it to the GNI for broadcast to aircraft
VDL Mode 3 Broadcast System implemented and tested
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