Data link in CNS/ATM Data link Aeronautical telecommunication network (ATN) data link: Air-ground data link Error decreasing High reliability Data transmission in high speed Data link High accuracy in transmission Print of information Decreasing of traffic in communication channels Transmission of data in text or even in media To decrease of controllers workload To decrease of crew workload Data link To understand the information easily and rapidly. To display the information in any media like windows. Data link Data link is the basic component of communication between air traffic controller (ATC) and aircraft. Data link in CNS/ATM Data link channels: ATC Mode-S VHFDL(VDL) HFDL AMSS ATC Mode-S data link capability: A/C to ground stations (downlink) ground stations to A/C (uplink) air to air ATC Mode-S ATC Mode-S Transponders support: all surveillance functions (UF 0,UF 4,UF 5, DF 0,DF 4,DF 5,DF 11). - bidirectional air to air data link (UF 16, DF16) - ground to air data uplink (comm. A) - air to ground data downlink (comm. B) - uplink ELM & downlink ELM. ATC Mode-S / ELS SI codes are the way to identify interrogating stations in order that the A/C can selectively answer to them. So, only the interrogating station receives the reply. Also, the flight ID (flight number) is downlinked to ground. ATC Mode-S / ELS ATC Mode-S / EHS ATC Mode-S Enhanced Surveillance (EHS) was mandatory with effective date of march 2007. Enhanced Surveillance is the first stage in making use of air derived data in the form of Downlink Air Parameters (DAPs), either directly to controller or to ATC systems. ATC Mode-S / EHS - magnetic heading - selected altitude - true track angle - track angle rate - indicated airspeed - mach number - true airspeed - ground speed - roll angle - vertical rate ATC Mode-S / EHS information transmitted to ground causes the controller to supervise accurately on the aircraft. The controllers receive much more information and the quality is increased. In high density traffic like Europe, all of the parameters will be easily available to the controllers and so, the pilot has not to report them. ATC Mode-S / EHS Therefore, the pilot might not use the VHF voice which causes decreasing of VHF bands traffic. The DAPs from different systems on the A/C, are received by ATC Mode-S Transponder. The Transponder downlink them as the replies of the interrogations. The project causes decreasing of the errors in controllers supervision. ATC Mode-S Extended Length Memory (ELM): 16 words 80 bits in each interrogation 16 words 80 bits in each reply ATC Mode-S data link Long messages are transmitted using Extended Length Message (ELM) capability. ELM is capable of transmitting up to sixteen 80 bits message segments, air to ground or ground to air. No surveillance data is considered in ELM. ELM can be acknowledged by a single reply or interrogation. ATC Mode-S data link ELMs uplinked need not be replied to individually, but can be acknowledged in a reply containing a summary of the received interrogations. Downlinked ELMs are transmitted only after authorization by the interrogator. The segments are transmitted in comm D replies. VHF Data Link In future, voice communication will be used for critical messages: To avoid traffic Landing clearance at airports with heavy traffic. It will serve as back up for data link. The VHF Data Link (VDL) operation requires a VHF digital radio (VDR). VHF Data Link VDL is essential for ATN implementation. The VDL formats specify a protocol for delivering data packets between airborne equipment and ground systems. The protocol is different to that used in the aircraft communication addressing and reporting system (ACARS). VHF Data Link The difference is that the VDL provides a capacity 13 times greater than the equivalent of 25 KHz VHF channel. VDL Mode-1 This mode has been especially designed to use ACARS. VDL mode-1 is a low speed bit oriented data transfer system. It uses carrier sense multiple access (CSMA) methodology. VDL Mode- 1 VHF analogue radios: for data exchange since the late 70s. ACARS system has been developed and has grown considerably. VDL Mode-1 has been especially designed to use ACARS modulation equipment and radio. ACARS and VDL mode-1 is a low speed bit oriented data transfer system. VDL Mode-2 VDL- Mode 2 uses same technology, but is not capable of handling voice communication. Average data transmission is 31.5 kbps. It employs a globally dedicated common signaling channel of 136.975 MHz. VDL Mode-2 VDL Mode-2 is the minimum requirement in CNS/ATM. Commercial services are available at the time being. VDL Mode-2 transmits coded data. (ie. in CPDLC) It is not necessary to send letters and numbers like ACARS. VDL Mode-2 The message “Climb to and maintain FL350” requires about 10 bits. This is the technology to speed transmission of information. Bit rate: 31.5 kbps Modulation: D8PSK A/C address is the same as ATC Mode-S Address (24 bits) VDL Mode-2 A/C and ground stations exchanges the information in frames. Each four frames of information require one acknowledgement. Data link communication according to the protocol specified in ICAO VDL Mode-2 and AMSS Data 3 standards. VDL Mode-2 VHF Digital Radios capable for ACARS don’t meet the requirements of the protocol ICAO VDL Mode-2. VDL Mode-2 is not capable of handling voice communication. VDL Mode-2 Communication Management Unit (CMU) or Air Traffic Service Unit (ATSU) manage transmission of digital information of the following systems: CPDLC (using VDL Mode-2) ADS-B (in future VDL Mode-4 probabely) ATC Mode-S VDL Mode-2 Communication Management Unit (CMU) or Air Traffic Service Unit (ATSU) should be capable to handle the ISO-8208 (X.25 protocol specified in ICAO VDL standard. VDL Mode-3 VDL Mode-3 is an integrated digital data and communication system. VDL Mode-3 uses four radio channels on a carrier (with a 25 KHz spacing). VDL Mode-3 uses a data link technology called TDMA. It is presently is not available for operational use. HF data link (HFDL) HF data link (HFDL) is another communication channel to transmit data from ground station to A/C and via versa. HFDL uses HF frequencies. HFDL is the only standby system for aeronautical mobile satellite system (AMSS) in oceanic / remote areas. HF data link (HFDL) The propagation anomalies rarely affect the entire HF frequency band. HFDL communicates with a number of adequate frequencies available in the HF band, to find the best frequency for transmission of data packages anywhere and at any time. HF data link (HFDL) Upon a suitable frequency is found, a log-on message is sent to ground station. Upon receiving of log-on confirmation, the information is sent (downlink) to ground station. A new frequency search is initiated after ground station has not acknowledged. HF data link (HFDL) Bit rate: 300 to 1800 bps. range: 6000 km coverage: oceanic and polar region HF data link (HFDL) In this mode aircraft can contact three or more HFDL ground stations constantly and its hub can become ATN routers. HF data link (HFDL) The A/C equipped with: HFDL Control Panel HF Data Unit plus HF Voice Radio or HF Data Radio HF data link (HFDL) HFDL important role: Not SATCOM equipped A/C , long range Data link for polar regions Aeronautical Mobile Satellite Services (AMSS) VHF Data link /ATC Mode-S Data link: - line-of sight restriction. - certain range - require support of ground stations, electric power, maintenance, etc. not appropriate for oceanic / long range communication. Aeronautical Mobile Satellite Services (AMSS) HFDL it is unsafe, medium quality, technical support, low speed, etc. Satellite communication: - high-quality voice and data communication services. Aeronautical Mobile Satellite Services (AMSS) AMSS provides: - digital voice and data services Data link: - communication services - broadcast (WAAS, EGNOS) AMSS Geostationary satellites Coverage: long range, oceanic, non-polar Bit rate: 10.5 kbps in max. Data link capability ICAO AMSS Standard data 3 AMSS L-band: 1545 to 1555 MHz 1646.5 to 1656.5 MHz. AMSS Services: - CPDLC - ADS-B - etc. AMSS Current SDUs provide services to ACARS will be replaced by SDUs which meet the requirements specified in AMSS Data 3 standard. Controller-Pilot Data Link Communication (CPDLC) The Air Traffic Control (ATC) system relies heavily on voice communications between air traffic controllers and pilots. It is to relay control instructions and other information critical to safe and expeditious flight. Controller-Pilot Data Link Communication (CPDLC) These communications are required to support coordination of aircraft movement in all phases of flight, to ensure: Aircraft separation Transmit advisories and clearances To provide aviation weather services. Controller-Pilot Data Link Communication (CPDLC) As air travel continues to increase, controller-pilot communication has increased to the saturation point during peak traffic periods at many locations. The workload of controllers increased more and more. This wastes more time on the ATC voice channel as repeated attempts to communicate are made. Controller-Pilot Data Link Communication (CPDLC) Saturation: no additional aircraft can be handled within the controller's assigned airspace . Controller-Pilot Data Link Communication (CPDLC) Air Ground Data Link (AGDL): a means of communications between pilots and controllers, using data link instead of voice. This type of communication between pilots and controllers is often referred to as Controller-Pilot Data Link Communications (CPDLC). Controller-Pilot Data Link Communication (CPDLC) Air Ground Data Link helps to solve the of the voice channels, the important problem for Air Traffic Controllers. introducing an AGDL introduces an alternative means of communication between the aircrew and the controllers, data link. CPLDC is used to relay routine messages from aircrew to controllers and via versa. Controller-Pilot Data Link Communication (CPDLC) CPDLC Data link messages (uplinks): - Check microphone (AMC) - Change SSR code/- Squawk ident - Contact (ACM) - Direct flight to turn and heading - Altimeter settings for conforming of flight level instructions Controller-Pilot Data Link Communication (CPDLC) - Initial contact altitude verification to ensure that pilot and controller's - Understanding of a flight's altitude clearance agrees on check-in - Voice frequency assignments for hand-offs or radio transmitter problems - Crossing restrictions for arrival and departure transitions/to comply with airspace restrictions Controller-Pilot Data Link Communication (CPDLC) - Menu text for weather alert or traffic flow conditions. - Route clearances Controller-Pilot Data Link Communication (CPDLC) CPDLC allows the information, such as aircraft parameters, to be down linked to the ground stations automatically. Controller-Pilot Data Link Communication (CPDLC) Data link messages (downlinks): - Altitude - Speed - Heading - Turn - Climb/descent/maintain flight level (ACL) - Flight plan Controller-Pilot Data Link Communication (CPDLC) Aircrew answer ATC instructions by data link and request routings from ATC. All of these messages will be exchanged without the need for voice read-back. CPDLC communication: not intended to be as fast as voice. It is designed to pass routine messages, where time is not an critical factor. Controller-Pilot Data Link Communication (CPDLC) The best analogy one could make for air/ground data link or CPDLC is that of a mobile phone. The use of CPDLC in high-density traffic airspace offers the potential to reduce voice channel traffic and to improve the saturation. Controller-Pilot Data Link Communication (CPDLC) Using CPDLC reduces the pilot's and the air traffic controller's communication workload and allows them to concentrate on other essential tasks. CPDLC transmits the information through VDL Mode-2 or geostationary satellites. Controller-Pilot Data Link Communication (CPDLC) CPDLC is windows-based for the controller. All of the actions are performed via the radar screen, using a mouse, the data link window and pre-defined menus. Controller-Pilot Data Link Communication (CPDLC) Colors are used to highlight the different states of a message. Uplink message awaiting a response from crew, is displayed in light green to the controller. Controller-Pilot Data Link Communication (CPDLC) Downlink request from the aircrew will display in white. The colors show in the data link window.
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