Second, this book aims to provide a comprehensive overview of the current, new and future communication systems dedicated to air-ground communication datalinks. At the same time, the International Civil Aviation Organization (ICAO) started the definition of the Aeronautical Telecommunication Network, including their air-ground sub-network.
History and definition
From voice to data link
It was in the late 1970s that airlines became convinced of the advantages of data link-based communication. Considering Data Link operation, as explained in [ICA 06], an aircraft is considered FANS-1/A equipped if it has air traffic services facility notification (AFN) capabilities.
Communication traffic classes
This class reunites communications related to non-secure voice and data services for passengers and crew members for personal communication. These regulatory restrictions do not apply to non-critical communications, even though they may have to meet some application-specific requirements (eg delay for passenger telephony).
Main actors and organizations
Their main objectives are focused on the definition of principles and techniques for international air navigation. The airlines are currently users of data link communication systems, mainly for ATSC, AOC or AAC.
Systems architecture
ACARS
It is described in several ARINC documents: the protocol is described in ARINC 620 (ground-ground interface) and ARINC 618 (air- . ground interface), but several other documents (among others or 619) deal with ACARS. Thus, this definition excludes the air-ground subnetwork, which may be used by different networks (e.g.
FANS 1/A
These applications were designed as bit-oriented applications and their operation required a QoS that the ACARS network could not provide by itself. These applications use exactly the same ATSC-specific features as described earlier: in particular, end-to-end CRC and additional ground addressing.
ATN baseline 1 and FANS 2/B
Regarding routing protocols, ICAO believed that intra-domain routing will be a local matter and the choice of the related routing protocol will remain implementation specific. As mentioned before, the performance of the air-ground sub-network will be consistent with the operating environment, and VDL mode 2 was chosen as the air-ground sub-network due to its high bandwidth, low delay and lower cost.
Radio subnetworks for air–ground communications
Radio resource management
Still in the case of S-ALOHA, S = 0.1 means that 10% of the time slots are used to send a useful data packet. In the part of the curve with a positive slope, the access technique behaves correctly: an increase in network load (growing G) results in increased efficiency.
VHF communications
The first step in VDL Mode 2 mobility management is, of course, service detection by avionics systems. Several simulation studies have been performed since the first VDL mode 2 subnet definitions.
SATCOM
However, the advantages of a geostationary orbit from a geometry perspective come with limitations in the design of the communication system. The use of the channel is controlled by allocation and release signaling at the beginning and end of each call or fax transmission. After powering on, the AES terminal must first retrieve the parameters of the AMSS system.
HF communications
Interoperability tests and operational integration of the AMSS JCAB regional service within the global Inmarsat system were carried out in 2006. Sixty-six active satellites are required to ensure full Earth coverage, 10 spare satellites are also deployed for system reliability [ICA 10a]. It should be noted that the channel reference frequency (the one found in the regulatory documents) is shifted to 1.4 kHz from the center frequency of the phase modulated carrier.
Data link related research projects
- Topics of interest
- European project: SESAR
- North American project: NextGen
- Designing emerging communication systems for data link
According to the scientific purpose of this book, only WPs related to data link communications will be described in detail. Design of developing communication systems for data link (for both SESAR WP and NextGen technologies) SESAR WP and NextGen technologies). The first, dedicated to data link communication in the vicinity of the airport (less than 10 km), is the AeroMACS communication system.
Emerging communication systems
Integrated end-to-end communication
An important aspect that will require a great effort for aircraft manufacturers is the integration of the new data links in the aircraft. Likewise, it is not possible to multiply the number of specific antennas on the aircraft. In such a context, new protocols have recently been identified as possible candidate technologies for use in handling the mobility of the aircraft while maintaining communication when moving between different ground stations.
Future aeronautical communication
The role of the service-specific convergence sublayer (CS) is to map the external network data received from higher layers via the service access point (SAP) of the CS into service data units (SDUs) of the MAC and transfer it to the MAC common part sublayer (CPS). ) via MAC SAP. Depending on the propagation conditions of the communication channel, appropriate modulation and coding schemes are selected. Quite similar to the principle used in DVB-S2/RCS2 systems, the decision of the ground station is controlled by the measurements made by the terminal receiver in the aircraft.
Sharing information: the SWIM concept
Why does ATM need SWIM?
Information must be structured and organized to provide broad interoperability between the various ATM stakeholders. Therefore, the idea behind SWIM is to equip providers and users of ATM information with a complete integrated information management system to improve communication between them. With SWIM, it should soon be possible to move from the current and inefficient ATM system, described in Figure 3.1, to a more efficient system, such as that described in Figure 3.2.
SWIM principles
SWIM technical components
This element of SWIM will be based on harmonized conceptual and logical data models that will provide global and common information modeling to the various ATM stakeholders. Indeed, many new SWIM concepts will need to be prototyped and validated in order to propose new SWIM applications. SWIM designers will need to develop and implement related changes in various user systems and applications.
Multilink operational concept
Multilink operational concept requirements
The MLOC extent is applicable to all airspace areas except Oceanic Remote Polar (ORP) regions where only satellite is available. Also, transitions between airspaces are also considered within the scope of MLOC (ie when an aircraft moves from one airspace to another). Considering the heterogeneity of the criteria mentioned above, the link selection procedure can be a tedious task.
Vertical handover in MLOC
First, the capabilities and performances offered by a given data link system to meet the required QoS for an ATS service must be considered. Several studies have been conducted to match these criteria and select the best data link system. First step is data link registration, where each available data link system is contacted by the multilink system to establish a connection.
IP mobility
IP mobility requirements for the FCI
Since IP mobility protocols are designed with mobility needs in mind, most of them meet this requirement. Then the IP mobility protocols must provide multiple network prefixes for a complete set of systems within the same on-board network. Security is relevant to reliability and availability of operational services, so IP mobility protocols should integrate fault-tolerant techniques.
IP mobility candidate solutions
Existing IP mobility protocols can be classified into routing-based and mapping-based approaches. Well-known IP mobility protocols that fall into this category are Mobile IP, Network Mobility (NEMO), and Proxy Mobile IP (PMIP). Wide-area IP Network Mobility (WINMO) is a hybrid IP mobility protocol that combines routing-based and mapping-based approaches.
IP mobility: open issues
Routing-based approaches state that each node has a fixed IP address during the mobility procedure regardless of its geographic position. Instead of keeping track of each mobile position, map-based approaches provide a dynamic IP address that maps to a unique identifier for each node. However, route-based and mapping protocols do not have the same complexity regarding session continuity: while route-based approaches do not need any further modifications at the transport layer due to the use of fixed IP addresses, mobility must be somehow "Hidden" at the transport layer in map-based protocols using a home address (HoA).
Traffic segregation
Context
In addition, coverage and high availability are very important requirements for data link communication, which means that mass deployment of earth stations supporting mobility must be done. Continuity of service is more or less supported by existing IP mobility protocols, as they were designed to maintain Traffic Control Protocol (TCP) sessions while moving. Nevertheless, providing a dedicated satellite link for operational services appears to be an expensive and long-term solution.
Traffic segregation and priority
For example, cryptographic signatures can be used within the tunnel, guaranteeing the integrity of the operational data traffic. On the airside, DAMA generates capacity requests (CRs) on a time slot basis and sends them to the Network Control Center (NCC), which responds within the Time Burst Time Plan (TBTP) containing the capacity allocations (one TBTP per frame). . Depending on the interconnection scenario, prioritization can be performed to associate packets with the CRs generated by the DAMA agent.
Certification issues for multiplexing solutions
This new version takes into account the latest developments in terms of model-driven approaches for software system design. The emphasis is placed on model-driven approaches capable of automatically generating software codes by taking as input only high-level models that represent the various characteristics and behaviors of the final system. DO-331 (Model-Based Development and Verification): in addition to DO-178 C, this standard deals with tools and methods used to automatically generate software and to validate these high-level models in line with initial system specifications.
Aeronautical network communications security
Levels of deployment for security mechanisms
In the scope of the EUROCONTROL/FAA Action Plan 17 [EUR 07b], AeroMACS system has been identified as the C-band technology candidate best suited to the provision of dedicated aeronautical communication services on the airport surface (this technology has been detailed in the previous chapters) . In [ALI 04], the authors depicted the scalability issues associated with the use of IPSec in the scope of ATN networks. In the context of ATN/IPS network architecture, we can also deploy additional security mechanisms at the transport layer.
Security controls coordination
Integrity, authentication, confidentiality, link key establishment, and secure routing were discussed regarding their potential to mitigate the most critical threats. The EDS application aims to distribute information assets such as software and data when the aircraft is in maintenance, in production or on the ground at the terminal. PKI systems have been mentioned as possible security solutions without a real assessment or adaptation to the specific aviation context.
Future aeronautical communication means
AANET-based air/ground communications
AANET principles and properties
In the case of oceanic airspace, earth station positions were determined on islands and coasts along the tracks to ensure optimal connectivity. In oceanic airspace, this communication range should be 350 km to ensure an average connectivity of more than 90% per day. Of course, the number of hops to the ground station depends on the considered communication range.
AANET access layer considerations
Also, to accommodate the decentralized nature of the network, it seems desirable to maintain random access as a dynamic allocation of resources (Demand Assignment Multiple Access). For example, the superiority of the CDMA approach over Carrier Sense Multiple Access (CSMA) access is shown in [PRO 07]. System capacity is governed by the interference level for the data channel.
AANET communications performances
Aeronautical Telecommunication/VHF Data Link Network (ATN/VDL) Mode 2 is incorporated within the framework of FANS 2/B and is currently deployed, either as an ATN subnet or as an additional Communications Addressing and Reporting System subnet of Aircraft (ACARS). The first, dedicated to short-range airport location data link communication, is the Aeronautical Mobile Airport Communication System (AeroMACS). Finally, this book summarizes the current state of the art of air-to-ground data link communications for Air Traffic Management (ATM).
