Ground-to-air telephone calling system and related method for directing a call to a particular passenger

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FIELD OF THE INVENTION

The present invention relates to a ground-to-air telephone system which permits a ground based caller to establish telephonic communication with an airborne telephone of unknown location.

BACKGROUND INFORMATION

Airborne telephone systems are well known and widely used. Such systems are typically utilized by a passenger on an aircraft to initiate a telephone call to a ground based party connected to the public switched telephone network (PSTN). Through such systems, an airborne party can initiate telephone calls to any telephone in the world. Such calls are transmitted from the airborne telephone to ground stations which route the telephone calls by way of the PSTN to the called party.

However, if a ground based party wishes to call an airborne telephone using such a system, the ground based party must know which specific ground station is within transmission range of the aircraft. This requirement necessitates that the ground based party know the particular location of the aircraft at any given time, thereby presenting prohibitive mapping requirements. As a result, ground-to-air telephone calls are seldom attempted because of the infeasibility of knowing the particular location of an aircraft at any given time.

Mobile ground telephone systems, such as cellular systems, are known, wherein a central location coordinates the selection of calls, i.e., the central location selects which ground station is in communication with the mobile telephone and routes and completes the call accordingly. Such mobile ground systems are inadequate for airborne use, however, because the use of such a central location in airborne applications causes inadequate contention between ground stations for the selection of channel frequencies.

SUMMARY OF THE INVENTION

In view of the foregoing, an object of the present invention is to provide a ground-to-air telephone system by which a ground based caller can initiate a telephone call to an airborne telephone of unknown location.

An additional object of the present invention is to provide a ground-to-air telephone system in which no modifications or variations are required to known airborne telephones.

Another object of the present invention is to permit selected activation of ground stations to provide a ground-to-air telephone system with regional or national extent.

A further object of the present invention is to eliminate contention between ground stations for channel frequencies.

A further object of the present invention is to provide a ground-to-air telephone system for a multi-telephone configuration on board an aircraft.

A further object of the present invention is to provide a ground-to-air telephone system capable of directing a call to a particular passenger.

To achieve the foregoing desires and objects, and in accordance with the purposes of the invention as embodied and broadly described herein, the present invention provides a system for establishing a communication link between a ground-based caller and a passenger on board an aircraft, the aircraft having a plurality of telephones, the system comprising a device for assigning a traveler assigned number (TAN) to the passenger, the TAN comprising a code to uniquely identify the passenger; a device for assigning an aircraft identification number (AIN) to the aircraft, the AIN comprising a code to uniquely identify the aircraft; a first correlation device for correlating the passenger's TAN to a predetermined seat assignment on the aircraft; a device for generating a data signal in response to a telephone call to the passenger from the caller, the data signal including the passenger's seat assignment, the aircraft AIN, and the caller's telephone number; a signal transmitting and receiving network for receiving the data signal and transmitting a call signal over a predetermined geographic area, the call signal including the passenger's seat assignment; a device, on board the aircraft, for receiving the call signal; a second correlation device, on board the aircraft and responsive to the seat assignment information in the call signal, for correlating the call signal with a predetermined telephone on board the aircraft; a switching device, on board the aircraft and responsive to the second correlation device for establishing a call connection to the predetermined telephone; a device, on board the aircraft and responsive to the call signal, for transmitting a response signal; and a device, included in the signal transmitting and receiving network and responsive to the response signal, for calling the caller's telephone number and completing a communication link to the caller when the caller answers the telephone call.

Additional desires and objects of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred implementations of this invention and, together with the general description given above and the detailed description of the preferred implementations given below, serve to explain the principles of the invention.

FIG. 1 is a general block diagram of a presently preferred embodiment of a ground-to-air telephone calling system incorporating the teachings of the present invention;

FIG. 2 is a detailed block diagram of a ground station utilized in the system of FIG. 1;

FIGS. 3a-3c are diagrams illustrating the formats of particular signals used in the system of FIG. 1;

FIGS. 4a-4d are flow charts of the operation of a ground-to-air telephone system incorporating the teachings of the present invention;

FIG. 5 illustrates a ground-to-air telephone system which includes a plurality of telephones on an aircraft in accordance with another embodiment of the present invention;

FIG. 6A illustrates an aircraft telephone/seating arrangement in accordance with one embodiment of the present invention;

FIG. 6B illustrates an aircraft telephone/seating arrangement in accordance with another embodiment of the present invention;

FIG. 7A is a flow diagram illustrating the operation of a ground-to-air telephone system in accordance with one embodiment of the present invention;

FIG. 7B is a flow diagram illustrating the operation of a transceiver and call distribution device in accordance with one embodiment of the invention; and

FIG. 8 illustrates a ground-to-air telephone system which includes a plurality of telephones on an aircraft in accordance with another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, there is shown a generalized block diagram illustrating a ground-to-air telephone calling system incorporating the teachings of the present invention. The system of FIG. 1 includes a telephone 20, a national paging control computer (NPCC) 22, an uplink unit 24, a satellite 26, a plurality of downlink units 28, a plurality of ground stations 30, a plurality of transmit/receive units 32, and an aircraft 34 having an airborne telephone 37 thereon.

Telephone 20 is coupled to the input of NPCC computer 22 via the public switched telephone network (PSTN). The output of NPCC computer 22 is coupled to the input of uplink unit 24 and passes a data signal 21 thereto.

Uplink unit 24, satellite 26, downlink units 28, ground stations 30, and transmit/receive units 32 form a signal transmitting and receiving network which covers any preselected geographic region. Data signal 21 is subsequently uplinked by uplink unit 24 to satellite 26 which transmits data signal 21 to downlink units 28. The output of each downlink unit 28 is coupled to an input of a corresponding ground station 30. Ground stations 30 receive data signals 21 from downlink units 28. An output of each ground station 30, i.e., a call signal 31, is coupled to an input of a corresponding transmit/receive unit 32. Each transmit/receive unit 32 subsequently transmits call signal 31 to possible aircraft locations. If the airborne telephone 37 on aircraft 34 receives a call signal from any transmit/receive unit 32, then an aircraft response 35 is formed and transmitted from the airborne telephone to the transmit/receive unit 32 from which the call signal was received. Aircraft response signal 35 is then passed from an output of transmit/receive unit 32 to an input of the corresponding ground station 30. Ground station 30 is coupled to the calling party over the PSTN.

In accordance with the teachings of the present invention, the calling party, via telephone 20, initiates a telephone call to NPCC computer 22. After receiving the telephone call, NPCC computer 22 then prompts the calling party to input an air-ground radiotelephone automated service (AGRAS) number, representing an identification number of the airborne telephone to be called. NPCC computer 22 further prompts the calling party to input a call-back number to which a subsequent telephone call can be placed to reach the calling party. After input of this information via telephone 20 over the PSTN, the calling party then hangs up his telephone.

NPCC computer 22 automatically generates data signal 21, which includes the call-back number, and passes data signal 21 to uplink unit 24 via standard techniques, i.e., land lines, microwave transmissions, etc. The format of data signal 21 fully comports with established protocol filed with the FCC and will be discussed below in more detail in connection with FIGS. 3a-3c. Uplink unit 24 then transmits data signal 21 to satellite 26 in a conventional manner. Likewise, data signal 21 is reflected by satellite 26 to downlink units 28, as is known in the art. Each down link unit 28 has associated with it a corresponding ground station 30 and transmit/receive unit 32. Preferably, down link units 28 are distributed nationwide, thus providing nationwide ground-to-air calling ability. The structure and function of ground stations 30 will be discussed below in more detail in connection with FIG. 2.

Data signal 21 received from satellite 26 by downlink unit 28 is automatically passed to ground station 30. Ground station 30 receives and unpacks data signal 21 and outputs call signal 31, which comprises the AGRAS number and a ground station identification number. Each ground station is assigned to a unique ground station identification number and, therefore, each call signal 31 output from a ground station 30 is unique. Each call signal 31 is transmitted by its corresponding transmit/receive unit 32.

If aircraft 34 is within transmission range of a particular transmit/receive unit 32, then the call signal transmitted by that transmit/receive unit will be received by the airborne telephone on aircraft 34. In response thereto, the airborne telephone forms and transmits aircraft response signal 35 on the same frequency channel on which call signal 31 was received, i.e., to the same transmit/receive unit 32 which transmitted the call signal received. Aircraft response signal 35 is passed from transmit/receive unit 32 to its corresponding ground station 30. In response to aircraft response signal 35, ground station 30 automatically initiates a telephone call over the PSTN to telephone 20. When the calling party answers the call, the calling party is connected via ground station 30 and transmit/receive unit 32 to the airborne telephone 37 located in aircraft 34.

FIG. 2 is a more detailed block diagram of ground station 30 illustrated in FIG. 1. Specifically, ground station 30 includes a first receiver 36, an unpacking unit 38, a first comparator 40, a queue 42, a second comparator 44, a second receiver 46, and a PSTN coupler 48.

An input of first receiver 36 receives data signal 21 from satellite 26, as illustrated in FIG. 1. Data signal 21 is passed from an output of first receiver 36 to an input of unpacking unit 38. Unpacking unit 38 unpacks the data signal 21 and outputs the call-back number to queue 42. Unpacking unit 38 further outputs call signal 31 to first comparator 40. Call signal 31 includes the AGRAS number of the airborne telephone to be called, as well as ground station identifying information. First comparator 40 compares the AGRAS number contained in call signal 31 against a list of invalid AGRAS numbers. If the AGRAS number contained in call signal 31 is found by first comparator 40 to be not invalid (i.e. valid), then call signal 31 is output from first comparator 40 to a corresponding transmit/receive unit 32.

As described above, call signal 31 is transmitted by transmit/receive unit 32 to potential locations of aircraft 34. If aircraft 34 is within the transmission range of transmit/receive unit 32, then the airborne telephone on aircraft 34 returns aircraft response signal 35 to the same transmit/receive unit 32. Aircraft response signal 35 is output from transmit/receive unit 32 to an input of second receiver 46. Second receiver 46 outputs aircraft response signal 35 to an input of second comparator 44 which verifies that ground station identifying information included in aircraft response signal 35 corresponds to the address of the ground station receiving the aircraft response signal. If aircraft response signal 35 has been received by the correct ground station 30, aircraft response signal 35 is output from second comparator 44 to an input of queue 42. Queue 42 then outputs the call-back number to an input of PSTN coupler 48 which initiates a telephone call to the calling party over the PSTN.

The formats of various signals used in the ground-to-air telephone calling system of the present invention will now be described in detail in connection with FIGS. 3a-3c. As shown in FIG. 3a, data signal 21 includes a start-of-header (SOH) flag 50, a header 52, a start-of-text (STX) flag 54, data blocks 56, and end flag (ETX) 58, and cyclic redundancy check code (CRC) 60.

SOH flag 50 preferably comprises one byte of data and identifies the beginning of header 52. Header 52 indicates the source and destination of each data block 56 and is described in more detail below in connection with FIG. 3b. STX flag 54 preferably comprises one byte of data and identifies the beginning of data blocks 56. Data blocks 56 are discussed in more detail below in connection with FIG. 3c. ETX flag 58 preferably comprises one byte of data and identifies the end of data blocks 56. CRC 60 preferably comprises two bytes of data which check for errors in the format of data signal 21.

As shown in FIG. 3b, header 52 includes a destination address 62, an inertia field 64, a source address 66, and a serial number 68. Destination address 62 preferably comprises four bytes of data allowing for the identification of 65,535 possible destination addresses identifying ground stations selected to receive data signal 21. By varying destination address 62, regional programmability of ground stations may be achieved. Inertia field 64 preferably comprises two bytes of data and represents a value used to determine whether a particular data signal 21 is still valid. Source address 66 preferably comprises four bytes of data representing a source address within NPCC computer 22. Serial number 68 preferably comprises two bytes of data and is used to uniquely identify a particular data signal 21 in order to prevent redundant transmission.

As illustrated in FIG. 3c, data block 56 is of a variable length and includes a data block type field 70, a page type field 72, a page class field 74, an RF channel designator field 76, an RF zone designator field 78, a function code field 80, a cap code field 82, a message text field 84, and an end-of-block (ETB) field 86.

Data block type field 70 preferably comprises one byte of data and describes the format of data block 56. Page type field 72 preferably comprises one byte of data and describes a signalling code used with the