- Voice Communication
- Data Communication
Types of Communication in ATS
Communication Categories:
- G/G (Ground-Ground): Between ATC units
- A/G (Air-Ground): Between aircraft and ground stations
- A/A (Air-Air): Between aircraft (e.g. TCAS, oceanic flights)
Communication Priorities
- Safety: Highest priority
- Reliability: Ability to function under stated conditions
- Availability: Measured by MTBF (Mean Time Between Failures)
- Coverage: Geographic area of effective communication
- QoS (Quality of Service): Includes all above
- Latency: Time to establish communication
- GoS (Grade of Service): Probability of blocked/delayed traffic
- Call Setup Time: Should be < 2 seconds
ICAO Aeronautical Communication Services
- AFS (Aeronautical Fixed Service): G/G communication
- AMS (Aeronautical Mobile Service): A/G and A/A
- Aeronautical Radio Navigation Service
- Aeronautical Broadcasting Service: ATIS, VOLMET
Voice Communication System (VCS)
- A/G Radio: Pilot ↔ Controller
- G/G Telephone: ATC ↔ ATC
- VCS Functions:
- Access to radio equipment
- Telephone calls to adjacent centers
- Voice recording data
Technical Concepts
- Voice Bandwidth: 300 Hz – 3400 Hz
- Dynamic Range: Ratio of max to min signal amplitude
- High Fidelity: Accurate sound reproduction
- Communication Loop: Readback ensures message integrity
Transmission Principles:
- Wired (Telephone) and Wireless (Radio) systems
- Modulation: AM used in ATC
- Digitalization: Reduces distortion
- Electromagnetic Waves: No medium needed, travel at speed of light
Radio Spectrum
- VHF (117.975 – 137 MHz): Used for civil ATC voice
- HF (3 – 30 MHz): Long-range communication
- UHF/SHF/EHF: Surveillance, navigation
Channel Spacing:
- 25 kHz spacing → 760 channels
- 8.33 kHz spacing → 2280 channels (mandatory since 2018)
Regulation Bodies:
- ITU: Spectrum management
- WRC: International agreements
- ICAO: Protects aeronautical spectrum
Recording Systems
- Voice Recorder: Ambient, telephone, radio
- Data Recorder: Radar, data link
- Retention Periods:
- ICAO: 30 days (no incident)
- Skyguide: 36 days (no incident), 15 years (incident)
Broadcast Services
- ATIS: VHF broadcast of airport info, updated every 30 min
- VOLMET: Weather info for en-route planning, VHF + data link
User Demands
Controller:
- Select sector frequency
- Monitor neighboring sectors
- Switch TX/RX in case of failure
- Configure ACC for traffic situations
Pilot:
- Select frequency
- Monitor communications
- Use VHF/HF channels
- Receive alerts via SELCAL
Exam Questions
What are the types of communication in ATS?
- Voice Communication
- Data Communication
What are the communication sub-domains?
- Ground-Ground (G/G)
- Air-Ground (A/G)
- Air-Air (A/A)
What are the highest priorities in ATS communication?
- Safety
- Reliability (% availability)
- Availability (MTBF)
- Coverage
- Quality of Service (QoS)
- Latency
How many channels are available since 2018?
With 8.33 kHz spacing: 2280 channels
What does channel spacing prevent?
Interference between adjacent radio channels
ICAO retention time for recordings?
30 days in case of no incident
What is the radio part of VCS?
It provides the interface between ATC and the transmitter/receiver equipment.
What elements form a radio CWP?
- Push-to-talk (PTT)
- Microphone
- Headset
- Loudspeaker
What are the functions of the VCS?
- Access to radio equipment
- Telephone calls to adjacent centers
- Voice communication recording
Basic function of the receiver?
To receive high-frequency signals and demodulate them.
What circuit combines audio with RF (Radio Frequency)?
Modulator
What is the CLIMAX technique?
Offset carrier technique used to reduce interference; only works with 25 kHz spacing.
Difference between hot and cold standby?
- Hot standby: Backup system is active and ready
- Cold standby: Backup system is off and needs activation
Which future communication technique will be used?
VoIP (Voice over IP)
