Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Traffic analysis or control of aircraft
Reexamination Certificate
1998-04-06
2001-01-09
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Traffic analysis or control of aircraft
C701S024000, C701S036000, C244S075100
Reexamination Certificate
active
06173230
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a data link system between an aircraft and at least one land-based station and a procedure for surviving failure of the application computer on board the aircraft in order to maintain an operational link.
BACKGROUND ART
The authorities responsible for controlling air traffic have decided to supplement standard voice communication systems with digital communications means in order to maintain the high safety levels required in the light of recent increases in air traffic.
The International Civil Aviation Organization (ICAO) is developing and installing a global telecommunications network called ATN for this purpose and applying OSI standards.
The performance requirements of the data link system increase in areas of high traffic and uptime performances become a major objective.
THE ACARS NETWORK
Airline companies now use a digital system for communicating between aircraft and their operations centers. This system, called ACARS (Aircraft Communication and Reporting System), is described in references [1] and [2] listed at the end of the present description. The system is used to exchange messages concerning aerial operations as well as administrative messages.
The majority of recent aircraft are equipped with the ACARS system, which has now been use for some fifteen years. It is particularly useful to airline companies for real-time management of their fleets, carrying out maintenance, operational control and performance optimization operations. Most Air Traffic Control (ATC) communications nowadays use VHF and HF voice links.
The efficiency of the ACARS system over the last decade has led the aviation authorities to extend its use into Air Traffic Control. Use of this resource to complement standard voice communication links will maintain the high safety standards imposed by the current increase in air traffic.
The US Federal Aviation Administration (FAA) has already started introducing this data link system in the South Pacific region where air traffic is less dense. This is a prelude to the widespread application of the “Future Air Navigation System” (FANS) which combines new Communication, Navigation and Surveillance (CNS) resources.
Performance requirements vary according to the type of traffic area under consideration; these areas are divided into oceanic, domestic, terminal and airport areas. Requirements are at their most severe in terminal areas where the traffic is at its densest as aircraft come in to land. Performances are defined in terms of integrity, uptime, and system transmission times.
Air Traffic Network (ATN)
The performance objectives associated with the interoperability objectives of distributed applications have led the ICAO to define a global Air Traffic Network (ATN) that is more compatible with the ACARS system. The ATN is described in document reference [3] listed at the end of this description. The improvements relate to adapting ISO standard protocols to ground-air networks by replacing character-oriented message formats with bit-oriented formats. These protocols are suitable for Open System Interconnection data exchange (OSI).
Data links enable ground-based and on-board computers belonging to a variety of independent bodies such as aviation authorities and airline companies to dialog. These computers are supplied by a wide variety of producers and are often of different generations. Faced with this situation, a set of standardized communication protocols is defined and then installed, validated and tested on each system to be used for data communication in order to make dialog between computers of different origin possible.
The choice of communication means must be transparent to the application. In practice, S mode, Satellite, VHF, HF and gate-link data links are not all available in every area an aircraft may be located. In order, therefore, to ensure continuity of service, the on-board ATC applications need to make a transparent change to the type of data link used during the flight.
If these conditions are complied with it is possible to interconnected on-board or ground-based computers so that they communicate with one another irrespective of the type of communication system used (VHF, HF, satellite, cable, etc.) and without having to write dedicated adaptation programs. This is the Air Traffic Network (ATN) concept, based on the interoperability of different types of sub-network. The architecture and protocols of ATN comply with the Open Systems Interconnection (OSI) reference model issued by the ISO. This model is used as a working framework for defining the services and protocols used in the ATN.
The ATN is defined as an interconnection of data networks capable of providing a common communication service to meet the needs of air traffic control (ATSC) and the airline companies (AISC). This interconnection may include and use existing networks and infrastructures whenever possible. The service proposed must meet the operating safety and access security demands required by the air traffic control and airline company applications as well as offering various levels of service.
The OSI architecture puts the responsibility for routing onto computers known as Routers, thereby freeing the end systems from performing this function. This allows the end systems to remain relatively simple. An ATN user system, which may range from a complete ATC system to a simple personal computer, accesses the network services via an access point. A user first accesses the ATN via a sub-network such as an Ethernet network or X25 public network such as Transpac, which accesses an ATN router that is a subscriber of the sub-network. The user system is directly connected to the access sub-network via a physical connector and by using this sub-network it communicates with the ATN router. It accesses the ATN services via the ATN router. The user system must therefore include the hardware and software needed to use the access sub-network. It must also supply the Connectionless Network Protocol (CLNP) and the ES-IS routing data transfer protocol between the end systems (ES) and the routers (IS), the CLNP being a simple protocol supporting the exchange of messages known as datagrams between a transmitting entity and a receiving entity; the ES-IS protocol enables users and access routers to identify one another.
Like all networks, the ATN can never attain a 100% delivery probability; its performance can, however, come near this figure by eliminating the use of low-reliability sub-networks, by increasing the router commutation capacity and sub-network transmission, and due to the redundancy included in the architecture of the systems.
Open System Interconnection (OSI) Communication Model
The OSI model divides the data communication process into seven levels of service. Each level of service (or layer) uses the level directly below it to provide a more abstract service level. This type of architecture has the advantage of hiding the underlying structure of the communication system, which makes it possible to use the same interface accessing telecommunications services for very different transmission systems. An ATC system can therefore be developed and operated irrespective of the type of telecommunications system used. Two similar ES (End System) computers supporting the distributed application (one on-board and one on the ground) are installed at each end of the data communication system. A certain number of intermediate hidden computers are located between these two systems; their task is to route and relay data passing through the network. A representative (or entity) of each level of service is present in each of these computers. The ES computers contain at least the first four levels of service described below, while the intermediate computers only include the first three. The protocol of a given level enables two remote entities to exchange data concerning the service provided by that level.
Every transmission system includes physical transmission mediums that transmit binary data from one compu
Camus Paul
Rascol J{acute over (e)}r{circumflex over (o)}me
Aerospatiale - Societe Nationale Industrielle
Arthur Gertrude
Burns Doane Swecker & Mathis L.L.P.
Cuchlinski Jr. William A.
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