AAI Cover Page

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NEW TRENDS IN AERONAUTICAL AIR - GROUND
COMMUNICATION
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• AERONAUTICAL COMMUNICATIONS
• Encompass all the facets of Ground Air
  Communications
• The Communication Navigation scene is changing
  fast
• Introduction of Satellite, VOIP ATM systems
• The most vital is Air - Ground Communications
  between Aircraft
• Pilot and Ground - based Air Traffic
  Controllers (ATC)
• Our present talk is on advances in pilot - ATC
  Communications

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• AIR TRAFFIC CONTROL
• Service provided by ground - based controllers
• Prevent aircrafts from coming too close to each
  other
• Ensures orderly and expeditious flow of traffic
• Provides information to pilots, such as weather
  and
• navigation information

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• CONVENTIONAL ATC SYSTEM
• Predominantly voice - based
• Analogue modulation for Voice TX/ RX
• The communication clarity is prone to language
  ambiguities
• The TX/ RX use channel spacing of 25 kHz - large
  figure
• - difficulty in accommodating more frequencies

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• HANDICAPS OF THE CONVENTIONAL ATC SYSTEM
• Congestion of available frequency spectrum ( 118
  - 137 MHz)
• due to rapid increase in traffic demand for
  more
• frequencies
• Increase in no. of frequencies leads to small
  frequency
• separation (lt 1.0 MHz Typ.). This causes
  interference
• between different frequencies
• May lead to error by ATC controllers who may
  hear more
• than one voice at a time/ frequency
• 
  (Contd..)

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• It is estimated that available spectrum will be
  saturated by 2011
• Aircraft take-off/ landing delays
• Compromise in the safety of passengers and
  flight crew
• No common time base between Ground Air
• Aircraft position known only to ATC

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• WHAT IMPROVEMENTS CAN BE DONE?
• We must be able to reduce channel spacing of 25
  kHz
• to accommodate more channels
• Pilot should be provided with communication/
  navigation
• data on data links
• Data linking solution is critical - Free the
  pilot from using
• voice as much as possible
• VHF DATA LINK (VDL) technology should be
  implemented
• to provide effective and reliable
  communications
• (Contd...)

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• ICAO ( International Civil Aviation
  Organisation) FAA
• (Federal Aviation Agency), USA Plan to deploy
  digital
• Next Generation Communication (NEXCOM )
  program for
• digital voice and data
• Data link standard for these radios is VDL 2,3
  4 Mode.
• NEXCOM stress is on VDL 3
• System is capable of reorganizing transfer
  queues
• NEXCOM project will be completed by 2020 in
  phases.
• Trial already underway in some sectors in USA
  Europe

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• VDL Modes
• VDL 2
• Data only
• one channel
• VDL 3
• Both Voice and Data
• Four channels
• VDL 4
• Data only
• Allows aircraft localization accurately not only
  to
• controllers but also other authorized
  personnel

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• What are the options available to us?
• Improvement in available spectrum utilization
• European countries are utilizing 8.33 kHz
  channel spacing
• Data instead of voice communication
• Voice Communication in digital form

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Typical VDL 2 Controller Pilot Data Link
Communications (CPDLC) Architecture
VDR Transceiver
FAA
VDL-2 Ground Stations
Router
HID
NAS LAN
NADIN II
Service Provider
A/G ATN Router
G/G ATN Router
NADIN II
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• What is VDL 3?
• Based on D8PSK modulation
• Utilize TDMA scheme ( different time slots in 1
  channel)
• Provide both digital voice and data
• Provide many options

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• Why VDL 3 for NEXCOM?
• VDL 3 utilizes available spectrum more
  efficiently
• Each 25 kHz channel consist of 4 voice/ data
  channels
• Voice and Data available on same frequency
• Voice and Data are in digital form
• Ground station may also be controlled in VDL 3
• ( Contd....)

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• VDL 3 provides various options for voice/ data
  transmission
• VDL 3 increases the capability of VDL 2. In
  place of
• 1 digital data channel in VDL 2, 4 digital
  voice/ data
• channels are available in VDL 3
• In VDL 3 Time Division Multiple Access (TDMA)
• scheme is utilized

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• VDL 3 (Diagrammatic representation)

011
010
001
9.524 micro second (10.5 kHz)
101
110
111
001
45
000
101
Information Data Stream
100
110
100
Vector Phase Diagram
( Contd...)
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• Utilizes D8PSK modulation technique
• Data component is in direct phase which moves
  from
• one signal to another and on change of every
  45 degree,
• it represent different bits of data
• 31.5 kbps data rate
• Modulation technique used is similar to the one
  used
• in VDL Mode 2

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• VDL 3 (TDMA structure)

120 milliseconds
Slot A
Slot B
Slot C
Slot D
M sub-channel
V/ D Sub- channel
30 milliseconds
( Contd...)
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• Every slot is an independent Voice/ Data channel
• Management (M) channel, controls all other
  channels
• Voice/ Data ( V/ D) consists of Digitized Voice
  or
• digital data ( 4.8 kbps rate )

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• VDL 3 (Slot structure)

Data 576 bits
PG Band 2.71 ms
V/ D Sub- channel burst
30 milliseconds
Aircraft Transmission
System Data 96 bits
Data 576 bits
V/ D Sub- channel burst
M sub channel burst
21.8 milliseconds
Ground Transmission
( Contd...)
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• Management sub channel is transmitted from the
  ground
• for voice circuits
• Controls the system configuration
• Controls transmission direction
• Provides voice signal status

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• VDL 3 (System Configuration)
• 4V - Four different voice stations
• 2V2S - 2 different voice stations at 2 different
  places
• 2V2D - 2 different stations with 1 voice and 1
  data slot
• 3V1D - 1 common data channel for 3 different
  voice stations

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• VDL 3 (Operational advantages)
• Airborne lockout is present during ground
  transmission
• Ground control is present for Near
  simultaneous
• airborne transmission
• Simultaneous transmission is controlled from
  the ground
• Protections are provided against microphone
  faults

( Contd...)
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• Superior squelch operation
• Superior co-channel performance
• Noises from amplitude modulation do not effect
  its operation

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• VDL 3 (Structural advantages)
• Sufficient increase in available Voice and data
  channels
• Provision of dedicated voice and data channel
  for a station
• is available
• Both voice and data circuit may be present in
  one Transceiver
• for a station
• Various options are available for communications
  links at
• various places

( Contd...)
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• Switching from voice to data is easy
• Communication channel is selected on its own
• TDMA is not affected by aircraft movement

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Communications Transition - Mobile
CY
97
03
04
05
06
07
08
09
10
11
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13
14
15
02
01
00
99
98
NAS Modernization Phases
Phase 1
Phase 2
Phase 3
Step 1
Step 2
Step 3
Step 4
Mobile Comm Steps
VHF Radio -25 KHz
NEXCOM Radio - 25 KHz VHF AM (voice)
(voice)
ATC/AOC
NEXCOM Radios VDL Mode-3
Terrestrial
(voice and data)
VHF
Digital Link
VDL-Mode 2
(ACARS)
CPDLC Build 2
ATN-Compliant
Non-VHF communications

support advanced data link applications
Agency Mobile
FTS2001
HF Voice
SATCOM Voice
HF Data Link
ATC / AOC
(ARINC 622)
Oceanic
SAT and VHF Digital Link
HF and SATCOM
ATN Data Link
(with ARINC 622/FANS-1)
(not costed)
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• Other VDL Modes
• VDL 2
• Allows for data-only link
• Based on D8PSK modulation
• 25/ 8.33 kHz channel spacing
• Operating at 31.5kbps
• Physical media access is realized on Carrier
  Sense
• Multiple Access (CSMA) scheme

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• VDL Mode 4
• Allows operating data links onto a common shared
  
• channel resource
• Based on GFSK modulation
• 25/ 8.33 kHz channel spacing
• Operating at 19.2 kbps with a net link capacity
  of 14kbps

( Contd...)
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• Physical media access is realized on Self
  organizing
• Time Division Multiple Access (TDMA) scheme
• Each super frame composed of 4500 timeslots,
  whose
• duration is 13.33 ms
• Super Frame duration in all cases is 1 minute

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• Conclusion
• We are facing crisis in Communication
  capability in Civil
• aviation field
• Importance of data communication will increase
  and we
• need to do planning for it
• Temporary solutions will not be able to remove
  crisis
• Next generation Radios are required with VDL
  VOIP
• capability. Already being manufactured by a few
  vendors
• The transition from conventional to VDL ATC
  shall involve
• large - scale infrastructure changes at the
  ground aircraft level

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• Other Applications of VDL technology
• Can be used for Ground VHF / UHF Communication
• Can be used for Marine VHF / UHF Communication
• Can be used in HF Communication

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• Airports Authority of India (AAI) Project
• Supply of 300 sets of VHF TX/ RX RCU
• for Air Traffic Control
• Project Value INR 24 Crores
• Manufacturer M/s Selex Communications (OTE),
  Italy
• Project Duration January 2003 - May 2005

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THANK YOU