United States Patent [191
`Gilhousen
`
`-~ [11] Patent Number:
`[45] Date of Patent:
`
`5,519,761
`
`May 21, 1996 _
`
`[54] AIRBORNE RADIOTELEPHONE
`COMMUNICATIONS SYSTEM
`
`[75] Inventor: Klein S. Gilhousen, Bozeman, Mont.
`
`[73] Assignee: QUALCOMM Incorporated, San
`Diego, Calif.
`
`[21] Appl. No: 272,061
`[22]
`Filed:
`Jul. 8, 1994
`
`Int. Cl.6 ..................................................... .. H04Q 7/38
`[51]
`[52] US. Cl.
`. 379/59; 379/58; 379/60;
`455/11.1; 455/33.2
`[58] Field of Search ................................ .. 379/58, 59, 60,
`379/63; 455/9, 11.1, 12, 13, 15, 33.1, 33.2,
`33.4, 54.1, 56.1, 66
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`2/1991 Lee ....................................... .. 455/54.1
`4,249,181
`4,419,766 12/1983 Goeken et a1. .
`.... .. 455/62
`4,607,389
`8/1986 Halgn'mson
`.. 455/11.1
`
`
`
`5,067,172 11/1991 Schloemer 5,073,900 12/1991 Mallinckrodt
`
`'
`
`.. 455/34
`
`375/1
`455/56.1
`6/1992 Choate ......... ..
`.... .. 379/59
`4/1995 Bhagat et al.
`8/1995 Frey et a1. .............................. .. 379/58
`
`5,123,112
`5,408,515
`5,444,762
`
`FOREIGN PATENT DOCUMENTS
`
`9300629 7/1993 WIPO .
`
`OTHER PUBLICATIONS
`
`Ericsson Review Article “The Future of Cellular Tele
`phony”, No. l, 1990, by Jansson et al.
`Seimens Telecom Report, “Third Generation Mobile Com
`munications”, No. 3-4, 1992, pp. 17—21, By Dr. Armbriister.
`
`IEE Conference Article“’I'he Provision of GSM Cellular
`Radio Environments Within Passenger Aircraft Operating
`Over Europe”, pp. 172-176, 1989, by Casewell.
`“Prodat Aeronautical Communication System Overall
`Architecture and Preliminary Test Results”, The IEEE Com
`munications Society and Seattle Section, Roger Rogard et
`al., 1987, pp. 5l3—518.
`“Terrestrial Flight Telephone System for Aeronautical Pub
`lic Correspondence: Overview and Handover Performance”,
`E. Berruto et al., 11312 MRC Mobile Radio Conference,
`13—l4—l5 Nov. 1991, Nice, France, (1991) Valbonne,
`France.
`“Terrestrial Flight Telephone System: Integration Issues for
`a Pan-European Network”, F i?h Nordic Seminar on digital
`Mobile Radio Communications, G. D’Aria et al, Oct. 12,
`1992, pp. 123-130.
`Primary Examiner——Dwayne D. Bost
`Attorney, Agent, or Firm—Russell B. Miller
`[57]
`ABSTRACT
`
`The airborne radio communications system of the present
`invention enables an airborne radio to communicate with the
`ground based cellular radiotelephone system. The present
`invention also enables the ground based system to keep track
`of the location of the airborne radiotelephone and page it
`when a call from the ground based telephone system is
`received. The ground base station is connected to upward
`radiating antennas that form airborne cells. As the aircraft
`with the radio ?ies through the airborne cells, the airborne
`relay receives the signals from the base station and relays
`them to the radio. If the radio is transmitting signals, the
`relay transmits those signals, through the airborne cells, to
`the base station. As the aircraft moves from cell to cell, the
`radio is handed off to the next cell to maintain communi
`cations with the ground.
`
`4 Claims, 3 Drawing Sheets
`
`150
`
`l 10 r
`f 1 15 \\ MOBILE SWITCHING
`OFFICE
`
`
`
`\
`
`PSTN
`
`120
`
`/
`BASE
`STATION
`
`———
`
`-
`
`———-—
`
`I
`
`Petitioners' Ex. 1008 - Page 1
`
`

`
`US. Patent
`
`May 21, 1996
`
`_ Sheet 1 of 3
`
`5,519,761
`
`2925
`
`
`
`
`5 \ ozEotBm 5502 Ill/l]
`
`mm<m momma 25m
`
`m:.\ . 2 _ K
`
`m2 _
`
`H .UE
`
`Petitioners' Ex. 1008 - Page 2
`
`

`
`US. Patent
`
`May 21, 1996
`
`Sheet 2 of 3
`
`5,519,761
`
`r 215
`
`FIG. 2
`
`O00
`O00
`O00
`O00
`
`I
`
`O00
`O00
`GOO
`000
`
`I
`
`O00
`O00
`GOO
`O00
`
`I
`205
`
`3O 1
`REGISTER /
`RADIOTELEPHONE
`WITH NEAREST CELL
`
`RADIOT ELEPHON E
`OR LANDLINE
`INITIATED CALL
`COMMUNICATED
`BETWEEN
`REPEATER AND
`RADIOTELEPHONE
`
`AIRBORNE
`SUBSYST EM
`RECEIVING AND
`AMPLIFYING
`RADIO SIGNAL
`
`3 1 0
`
`320
`
`325
`
`FIG. 3
`
`GROUND
`SUBSYST EM RELAYS
`SIGNALS TO PSTN
`AND VICE VERSA
`
`Petitioners' Ex. 1008 - Page 3
`
`

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`Petitioners' Ex. 1008 - Page 4
`
`

`
`5,519,761
`
`1
`AIRBORNE RADIOTELEPHONE
`COMlVIUNICATIONS SYSTEM
`
`BACKGROUND OF THE INVENTION
`
`5
`
`I. Field of the Invention
`The present invention relates to the ?eld of communica
`tions. More particularly, the present invention relates to
`cellular radiotelephone communications between an air
`plane and a ground based station.
`11. Description of the Related Art
`Present communications technology enables aircraft pas
`sengers to make telephone calls to anywhere in the world
`from any properly equipped airplane. Large airline-type
`aircraft as well as smaller general aviation-type aircraft can
`be equipped with the radiotelephone equipment.
`A radiotelephone conversation is typically accomplished
`by ?rst entering the telephone number to be called as well as
`credit card information to pay for the call. The radiotele
`phone then connects with one of 70-80 radiotelephone base
`stations, also known as cells, on the ground. The cell to
`which it connects depends on to which base station the
`aircraft is closest when the call is initiated. The cells, each
`connected to the public switched telephone network
`(PSTN), cover most of the continental United States, thus
`allowing a telephone call to be initiated from an aircraft
`almost anywhere.
`Aircraft radiotelephones, however, experience a number
`of problems. First, the aircraft based radiotelephone does not
`register in the ground based system. The ground based
`system, therefore, does not know the location of the aircraft
`radiotelephone. This restricts the aircraft radiotelephone to
`initiating calls; it cannot receive calls since the ground
`system does not know where to forward calls.
`Another problem is that the aircraft radiotelephone system
`does not perform hand-o?'s between cells as is done in
`ground based cellular radiotelephone systems when the
`radiotelephone reaches the edge of the cell. This results in
`the call from the aircraft radiotelephone being dropped when
`the aircraft reaches the limit of the cell’s coverage. There is
`a resulting need for an airborne radiotelephone system that
`is compatible with the ground based cellular radiotelephone
`system. In other words, an airborne radiotelephone system is
`needed that enables ground initiated telephone calls to be
`received by the airborne radiotelephone in addition to the
`call from the airborne radiotelephone being handed off to the
`next cell as it reaches the edge of the cell’s coverage.
`
`15
`
`20
`
`25
`
`35
`
`45
`
`SUMMARY OF THE INVENTION
`
`The system of the present invention encompasses an
`airborne communications system having a ground based
`subsystem and an airborne based subsystem. The airborne
`based subsystem includes a radio for transmitting and
`receiving radio signals and an airborne radio repeater for
`relaying the radio signals from the airborne radio to the
`ground based subsystem. The radio repeater also relays radio
`signals from the ground based subsystem to the airborne
`radio. The ground based subsystem includes a base station
`that is coupled to a public switched telephone network
`(PSTN) for transmitting PSTN originated signals and receiv
`ing relayed radio signals. The base station has at least one
`upward radiating antenna for transmitting and receiving the
`radio signals.
`
`55
`
`65
`
`2
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 shows the airborne radiotelephone communica
`tions system of the present invention.
`FIG. 2 shows the airborne based subsystem of the present
`invention.
`FIG. 3 shows a ?owchart of the process of the present
`invention.
`FIG. 4 shows a block diagram of an alternate embodiment
`of the present invention.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`The airborne radiotelephone communication system of
`the present invention is illustrated in FIG. 1. This system is
`comprised of two subsystems: the ground based subsystem
`(105) and the airborne based subsystem (125).
`The ground based subsystem (105), in the preferred
`embodiment, is the code division multiple access (CDMA)
`cellular radiotelephone system. An alternate embodiment
`uses the time division multiple access system. Another
`alternate embodiment uses the present advanced mobile
`phone system (AMPS). A typical CDMA radiotelephone
`system is discussed in greater detail in U.S. Pat. No. 4,901,
`307 to Gilhousen et al. and assigned to Qualcomm, Inc.
`The ground based radiotelephone system is comprised of
`a base station (120), also known as a cell site, coupled to a
`mobile switching center (115) that is coupled to the public
`switched telephone network (PSTN) (110). The base station
`(120) communicates with the mobile radiotelephones and
`switches the signals from the radiotelephones to the mobile‘
`switching center (115). The base station (120) also provides
`the proper channels to the radiotelephone, thus enabling
`communication with the base station. The mobile switching
`center (115) switches the signals from the base station (120)
`to the PSTN (110) and vice versa.
`Each base station (120) is coupled to an antenna (150) that
`receives and radiates the CDMA radiotelephone signals. In
`the preferred embodiment, the antenna (150) is identical to
`typical cell site antennas that are well known to one skilled
`in the art. An alternate embodiment uses an antenna that
`radiates upward. This upward radiation forms a cell that is
`elevated above the ground allowing the airborne radiotele
`phone to travel through the elevated cells in the same
`manner that a mobile radiotelephone on the ground travels
`through terrestrial cells. An antenna that forms this type of
`elevated cell is a typical directional antenna that is well
`known in the art.
`A block diagram of the airborne based subsystem of the
`present invention is illustrated in FIG. 2. This subsystem
`uses a CDMA-type radiotelephone (205) to communicate
`with a radiotelephone signal repeater (210), having an
`antenna, that is located in the aircraft. In the preferred
`embodiment, the repeater (210) also has an ampli?er to
`increase the signal’s gain that is being communicated to the
`repeater.
`The repeater (210) receives the signals from the indi
`vidual radiotelephones (205) within the aircraft and relays
`them to an antenna (215) mounted on the outside of the
`aircraft. The outside antenna (215) relays the signals to the
`base station on the ground. This subsystem may have a
`single radiotelephone, as in a small aircraft, or multiple
`radiotelephones, as in an airline size aircraft.
`The airborne subsystem also operates in the reverse
`direction. Telephone calls from the PSTN to the base station
`
`Petitioners' Ex. 1008 - Page 5
`
`

`
`5,519,761
`
`3
`on the ground are transmitted to the outside antenna (215)
`that relays them to the repeater (210) mounted in the aircraft.
`The repeater’s antenna communicates the signal to the
`proper radiotelephone (205) in the aircraft. The radiotele
`phones (205) determine which signal is to be decoded by the
`process described in Gilhousen et al. and in the Telecom
`munications Industries Association/Electronic Industries
`Association Interim Standard 95 (T1A/EIA/IS-95).
`In an alternate embodiment, the radiotelephone signal
`repeater is replaced by an airborne base station that has the
`ability to register the radiotelephones on the aircraft. The
`airborne base station then registers the radiotelephone with
`the ground based subsystem. This base station has the same
`functionality of its ground-based counterpart but on a much
`smaller scale since it does not have to handle the thousands
`of radiotelephones of the ground-based station.
`The airborne communications system of the present
`invention operates in a similar way to the ground based
`CDMA radiotelephone system discussed in Gilhousen et al.
`A ?owchart of this operation is illustrated in FIG. 3.
`The process begins by the airborne repeater registering
`the radiotelephone with the nearest cell site (301). This is
`accomplished in the same manner as a terrestrial radiotele
`phone registers with the ground based radiotelephone sys
`tem; the repeater searches for the strongest pilot signal and
`registers with that cell. This registration process involves the
`radiotelephone’s telephone number and electronic serial
`number being transmitted to the base station. The registra
`tion process is described in greater detail in US. Pat. No.
`5,289,527 to Tiedemann and assigned to Qualcomm, Inc.
`The radiotelephone or ground-based land-line telephone
`system can now initiate a call (310). The call from the
`radiotelephone is received by the airborne repeater and
`ampli?ed (320) before being transmitted to the ground base
`station. The ground base station then transmits the call to the
`mobile switching center that routes the call to the PSTN
`where it is then connected to the called telephone number
`(325).
`The signals from the PSTN to the airborne radiotelephone
`are routed in the reverse of the radiotelephone initiated call.
`The mobile switching center switches the call to the base
`station to which the radiotelephone is registered. The base
`station then transmits the signal (325) to the airborne exter
`nal antenna that relays it to the aircraft repeater (320). The
`repeater ampli?es it and transmits the ampli?er signal to the
`radiotelephone in the aircraft.
`The present invention also enables a ground telephone or
`radiotelephone to contact an airborne radiotelephone. Since
`the repeater has registered the airborne radiotelephone with
`the proper ground base station, the mobile switching center
`knows to which base station the call is to be routed. Once the
`call is routed to the proper base station it is transmitted to the
`airborne repeater which then ampli?es the call and transmits
`it to the radiotelephones on the aircraft. As discussed above,
`the radiotelephones then determine which signal is to be
`decoded.
`Another bene?t of the present invention is the hand-off
`capability. Once the aircraft reaches the fringe of the present
`cell site, the radiotelephone begins the hand-off process
`described in Tiedemann. The signals from the ground base
`stations are received by the external antenna of the airborne
`subsystem and repeated to the radiotelephones. This enables
`the radiotelephones to search for the strongest pilot signal of
`the next cell and register with that base station. The deter
`mining factor on when the quality of the pilot signal has
`been reduced to the point that a hand-off is required is when
`
`10
`
`15
`
`25
`
`45
`
`50
`
`55
`
`65
`
`4
`the pilot signal drops a predetermined amount. This amount
`may be different for every system and is set to optimize the
`system performance.
`In the alternate embodiment, the airborne repeater is
`replaced by a base station-type unit that registers the radio
`telephone aboard the aircraft. A block diagram of the air
`borne base station is illustrated in FIG. 4. Once the radio
`telephone is registered with the aircraft base station, the
`aircraft base station then searches for the strongest pilot
`signal from a ground base station and registers with that base
`station.
`Referring to FIG. 4, the airborne base station is comprised
`of a number of base station transceivers (410) that are the
`link between the radiotelephone and the base station. The
`CDMA interconnect subsystem (415) routes the signals
`between the transceivers (410) and the rest of the base
`station. The call control processor (420) controls signaling
`with the radiotelephones, controls all call processing, and
`allocates the base station resources. The time and frequency
`unit (430) provides the timing and frequency signals for the
`base station. The base station manager (435) performs
`initialization, con?guration, and performance management
`of the base station. And ?nally, the selector bank subsystems
`(440) processes and formats the data between the ground
`base stations and the radiotelephone. The selector bank
`subsystems (440) are connected to the aircraft’s external
`antenna (315) to receive and radiate the radiotelephone
`signals.
`Other embodiments using the airborne base station may
`have diiferent components and different features. A base
`station that simply registers the radiotelephone and relays
`this registration to the ground base station is also within the
`scope of the present invention.
`I claim:
`1. A communications system comprising:
`an airborne based subsystem for transmitting radio signals
`to, and receiving communication signals having a qual
`ity level from, a ?rst base station of a plurality of base
`stations in a ground based subsystem, and if the quality
`level of said ?rst base station’s communication signal
`is less than a predetermined amount, transmitting the
`radio signals to, and receiving the communication
`signals from, a second base station of said plurality of
`base stations, the airborne based subsystem compris
`ing:
`an airborne radio for originating the radio signals and
`receiving the communication signals, and selecting
`the second base station in response to the quality
`level of the second base station’s communication
`signal; and
`an airborne radio repeater for relaying the radio signals
`from the airborne radio to the ground based sub
`system and for relaying the communication signals
`from the ground based subsystem to the airborne
`radio;
`the ground based subsystem being coupled to a public
`switched telephone network (PSTN) and having at least
`one upward radiating antenna for transmitting the com
`munication signals and receiving the radio signals.
`2. The communications system of claim 1 wherein the
`plurality of upward radiating antennas emits a radiation
`pattern de?ning a plurality of airborne cells.
`3. A communications system comprising:
`an airborne based subsystem for transmitting radio signals
`to, and receiving communication signals having a qual
`ity level from, a ?rst base station of a plurality of base
`
`Petitioners' Ex. 1008 - Page 6
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`

`
`5,519,761
`
`5
`stations in a ground based subsystem, and if the quality
`level of said ?rst base station’s communication signal
`is less than a predetermined amount, transmitting the
`radio signals to, and receiving the communication
`signals from, a second base station of said plurality of 5
`base stations, the airborne based subsystem compris-
`ing: _
`_
`_
`‘
`‘
`_
`an airborne radiotelephone for originating the f?dlo
`signals and receiving the communication signals,
`and selecting the second base station in response to 10
`the quality level of the second base station’s com-
`munication signal; and
`an airborne base station for registering the radiotele-
`phone with the ground based subsystem and relaying
`the radio signals from the airborne radiotelephone to
`
`6
`the ground based subsystem and for relaying the
`communication Signals from the ground based Sub
`system to the airborne radio;
`I
`_
`the ground based Subsystem belng coupled to '3 P111311c
`switched telephone network (PSTN), and having a
`plurality of upward radiating antennas for transmitting
`the communication signals and receiving the radio
`signals.
`th
`t m f 1 .m 3 wh .
`4 Th Com m t.
`'
`e
`u ca Ions Sys 6 0 c 21
`6mm e
`plurality of upward radiating antennas emits a radiation
`Pattern de?ning a plurality of airborne cens
`
`* * * * *
`
`Petitioners' Ex. 1008 - Page 7