Questions to be answered:

1. How is the technical working principle of VHF Data Link and ADS-B? What are differences?
2. Which role play the two concepts for Air Traffic Management?
3. Which data are exchanged?

An individual essay is requested with appx. 1.000 words max.

 

Air Traffic Management

1. How is the technical working principle of VHF Data Link and ADS-B? What are differences?

An aircraft can have an onboard network to gather data, which, in turn, connects to a ground network through a data link. The system that is currently under development is the VHF Data Link, or VDL. VHF Data Link is a system through which data is transmitted between air vehicles and ground vehicles. VDL is controlled by a communications management unit, CMU, which has no controls, display or indicators (Helfrik, 2012).

VHF is a line of digital communication in the range of 118-137 MHz. This mode assumes the use of radio equipment for analog VHF communication for data exchange and frequency shift keying with a minimum phase shift (MSK), which provides data transfer rate over the air-to-ground communication channel of 2400 bps. The type of access to the communication channel is CSMA. The analog of this system is the ACARS system.
ADS-B (automatic dependent surveillance - broadcast) is a method of surveillance that uses GPS position information and is the key to the free flight concept. When the transponder of the aircraft receives a request from the ground-based radar, it acknowledges receipt of request with a pulse-position modulation (PPM) signal at 1090 MHz. Regardless of the request from the ground-based radar, approximately every second an extended squitter is transmitted by plane. This squitter contains the coordinates of the location of the aircraft.

ADS-B is based on the GPS system (not necessarily IRS) to determine the exact coordinates of an aircraft in space. The information about the position of the aircraft is combined with other data, such as the type of the aircraft, its speed, number, flight, heading, and vertical speed, and broadcasted approximately every second (Zimmerman, 2013). Other aircrafts and ground stations equipped with ADS-B within the radius of approximately 150 miles receive this information. Ground stations combine information received from different points with additional information received from ground-based radars and non-ADS-B devices and retransmits data to all aircrafts within the service radius. Aircraft and weather information can be displayed in the cabin of pilots if the aircraft is equipped with ADS-B.

2. Which role play the two concepts for Air Traffic Management?

Traffic information Service Broadcast Mode, TIS-B, is broadcasted from GBT in the ADS-B time slot. It provides state vector information from non-ADS-B equipped aircraft, which has been determined from other sources. Although the TIS-B message is broadcast in the ADS-B segment and can be handled in the same fashion as ADS-B messages from aircraft, it is important to identify the message as ground information. This prevents airborne equipment from ranging on a ground station as if it were an airborne unit.

VHF data link as well as ADS-B has the function of transferring data to a control point on the ground. However, unlike ADS-B, the VHF Data Link sends data of an intrinsic nature. These data contain information which helps to identify the location of the object, meteorological data, aircraft status data and others. The two systems made a significant contribution to the development of Air Traffic Management. Thus, in accordance with ARINC-750, a VHF-band on-board radio with VHL mode should provide:

1. Two-way simplex voice communication of the crew with ground services ATM and also between the crews of aircrafts in the air while working with a grid of frequencies 25 and 8.33 kHz, including the regime with offset carriers;

2. Automated data exchange in the air-to-ground and air-to-ground speed 2400 bps using the built-in or external modem AM-MSK for operation in the ACARS system;

3. Automated data exchange in the air-to-ground and air-to-ground speed 31500 bps when using the built-in D8PSK modem for operation in the ATN system;

4. Continuous monitoring of accuracy of radio serviceability to promptly replace block with preservation of information about the detected faults on the last 10 flight segments in non-volatile memory and interaction with on-board maintenance module or system localization of failures.

3. Which data are exchanged?

The VDL provides a range of messages, such as Air Traffic Service, which includes air traffic control and flight information services. For aeronautical operation control, messages include weather, flight plan, weight and balance, flight progress, flight following, gate assignment in flight emergencies, departure and delay information, and checklists.

ADS-B data contains information about the location, height, speed, and state of the equipment. Information is deciphered using GNSS (GPS).

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