CA1340967C - Satellite cellular telephone and data communication system - Google Patents
Satellite cellular telephone and data communication systemInfo
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- CA1340967C CA1340967C CA000617034A CA617034A CA1340967C CA 1340967 C CA1340967 C CA 1340967C CA 000617034 A CA000617034 A CA 000617034A CA 617034 A CA617034 A CA 617034A CA 1340967 C CA1340967 C CA 1340967C
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Abstract
A system for facilitating global cellular/trunked mobile communication is disclosed. This system permits communication with hand held and mobile mounted cellular telephones. The system permits two-way communications anywhere on or above the earth up to a particular height above the earth of several hundred nautical miles. The system employs a number of low-earth orbiting satellites moving about the earth in orbit. Links are provided from the satellites directly to the users and via the public switched telephone network to other users. The satellites are interconnected via linker in a ring structure surrounding the earth. Switching is performed by each of the satellites. In addition, each of the satellites hands off a call as it moves out of the range of a particular user.
Description
-~- 1340967 SATELLITE CELLULAR TELEPHONE AND DATA COMMUNICATION SYSTEM
The present inveni~ion pertains to global mobile communications and more' particularly to a satellite cellular telephone and data comnnunication system.
Present geostationary satellite communication systems allow point-to-point communication. That is, the satellite functions as a relay station or a "bent pipe". The satellite simply receives information from one point on earth and transmits it to another fixed point on earth.
One such po~_nt-to--point satellite communication system is shown in U.S. Patent: 4,720,873. This system shows point-to-point communic:ation~> through a satellite for network programming and a.dverti.sing purposes.
Some basic multiplexing functions may be supplied within the satellites c>f a satellite communication system.
One such system i.s shown in U.S. Patent 4,480,328. This patent teaches a satellite communication system in which the satellite is a relay station for TDMA multiplexed data.
The above-me~ntione~d systems and other systems teach the use of a single satellite for communications from one point to another. These satellite systems show no selectivity or switching of data among' a plurality of users.
Accordingly, it i~; an object of the present invention to provide a global low-earth orbiting multiple satellite cellular communication system which interfaces directly among a number of cellular telephone and data transmission equipped 3~~ users and also interfaces these users to the public switched telephone network (PSTN).
~dmmary of the Inv n inn In accomplishing the object of the present invention, a novel satellite cellu7_ar telephone and data communication system is shown.
A satellite cellular telephone communication system
The present inveni~ion pertains to global mobile communications and more' particularly to a satellite cellular telephone and data comnnunication system.
Present geostationary satellite communication systems allow point-to-point communication. That is, the satellite functions as a relay station or a "bent pipe". The satellite simply receives information from one point on earth and transmits it to another fixed point on earth.
One such po~_nt-to--point satellite communication system is shown in U.S. Patent: 4,720,873. This system shows point-to-point communic:ation~> through a satellite for network programming and a.dverti.sing purposes.
Some basic multiplexing functions may be supplied within the satellites c>f a satellite communication system.
One such system i.s shown in U.S. Patent 4,480,328. This patent teaches a satellite communication system in which the satellite is a relay station for TDMA multiplexed data.
The above-me~ntione~d systems and other systems teach the use of a single satellite for communications from one point to another. These satellite systems show no selectivity or switching of data among' a plurality of users.
Accordingly, it i~; an object of the present invention to provide a global low-earth orbiting multiple satellite cellular communication system which interfaces directly among a number of cellular telephone and data transmission equipped 3~~ users and also interfaces these users to the public switched telephone network (PSTN).
~dmmary of the Inv n inn In accomplishing the object of the present invention, a novel satellite cellu7_ar telephone and data communication system is shown.
A satellite cellular telephone communication system
- 2 -establishes communication among a plurality of users. This communication sy~;tem includes satellite switches positioned in low-earth orbit. Wireless communication links couple the users to the satellite switches. The satellite switches establish a communication link between selected ones of the users.
Each user's present location is determined and the system is periodically updated. Then the satellites relay these locations to the proper ground-based data base for 1~ storage. When a mobile: user places a call, the satellite which is in his spatial vicinity handles the call. When a mobile user is called, the satellite switches route the call through the appropriate satellites to the called user's current location. Other user-unique data may also be stored at these same data base storage sites.
~3rief I~ _ri ~t i_pn Of the Drawi nay FIG. 1 is a layout diagram depicting the satellite 2() switching system configuration of the present invention.
FIG. 2 is a block diagram depicting the interconnection of the satellite switching units with its association mobile users and interconnection to the public switched telephone network.
FIG. 3 is a projection of the areas served by a plane of cellular sate llite switches about the earth.
FIG. 4 is a block diagram of a data base arrangement for a satellite cellular communication system.
Desc>n Of h r f rrP~ Fmhn~imPnt Referring to FIG. 1, a satellite configuration for the satellite cellular telephone communication system is shown.
In this configural:ion, <~ number of satellites are shown in low-earth orbit. A number of satellites are placed in each orbiting plane. ~Chere a re several orbiting planes (3 through 8) as shown which are highly inclined in nature and provide switching coverage for t=he entire earth.
Each user's present location is determined and the system is periodically updated. Then the satellites relay these locations to the proper ground-based data base for 1~ storage. When a mobile: user places a call, the satellite which is in his spatial vicinity handles the call. When a mobile user is called, the satellite switches route the call through the appropriate satellites to the called user's current location. Other user-unique data may also be stored at these same data base storage sites.
~3rief I~ _ri ~t i_pn Of the Drawi nay FIG. 1 is a layout diagram depicting the satellite 2() switching system configuration of the present invention.
FIG. 2 is a block diagram depicting the interconnection of the satellite switching units with its association mobile users and interconnection to the public switched telephone network.
FIG. 3 is a projection of the areas served by a plane of cellular sate llite switches about the earth.
FIG. 4 is a block diagram of a data base arrangement for a satellite cellular communication system.
Desc>n Of h r f rrP~ Fmhn~imPnt Referring to FIG. 1, a satellite configuration for the satellite cellular telephone communication system is shown.
In this configural:ion, <~ number of satellites are shown in low-earth orbit. A number of satellites are placed in each orbiting plane. ~Chere a re several orbiting planes (3 through 8) as shown which are highly inclined in nature and provide switching coverage for t=he entire earth.
3 - 1340967 This satellite cellular structure is somewhat analogous to the present day cellular mobile telephone system. In that system, cellular sites are fixed and users are mobile. As a user travels from. one cell site to another, his telephone call is handed off from one cellular switching unit to another.
In the present invention, users are relatively fixed at any given time while the satellites, which are the cells, are in continuous movement. With a hand-held or mobile mounted 1~~ cellular telephone, connection to one of the satellite switches shown in FIG. 1 is made directly from the hand-held mobile mounted or remotely fixed telephone to one of the nearest satellite switches. Each satellite is moving about the earth. As the satellite which originally acted as the switching unit for a particular user leaves a cell of that switch, the user's call is "handed off" to the appropriate adjacent cell. A~3jacent cells may be cells within one satellite or cells of other satellites located either in a particular orbiting plane or an adjacent orbiting plane.
Users may "roam", but this roaming distance is relatively small compared to the traveling distance of the satellite switches.
Similar to t:he cellular mobile telephone system, the satellite cellular communication system provides spectral 2_'> efficiency. This means that the same frequency may be simultaneously used by different satellite switches.
Spectral efficiency is provided by the spatial diversity between the satel:Lite switches and users.
The users ma~~ be located anywhere on a land mass, on 3G the water or in the air at an altitude less than that of the low-earth orbiting satellites. For example, a person on one land mass could call a person on another land mass, a person on a boat or a person in an aircraft.
Low power hand-held mobile mounted or fixed radio 35 telephones may be used ~~n this system. The power requirement is less than 10 watts wS_th present technology.
In this system, each satellite shown is a switching unit. Current satellite communication systems act primarily 13409fi7
In the present invention, users are relatively fixed at any given time while the satellites, which are the cells, are in continuous movement. With a hand-held or mobile mounted 1~~ cellular telephone, connection to one of the satellite switches shown in FIG. 1 is made directly from the hand-held mobile mounted or remotely fixed telephone to one of the nearest satellite switches. Each satellite is moving about the earth. As the satellite which originally acted as the switching unit for a particular user leaves a cell of that switch, the user's call is "handed off" to the appropriate adjacent cell. A~3jacent cells may be cells within one satellite or cells of other satellites located either in a particular orbiting plane or an adjacent orbiting plane.
Users may "roam", but this roaming distance is relatively small compared to the traveling distance of the satellite switches.
Similar to t:he cellular mobile telephone system, the satellite cellular communication system provides spectral 2_'> efficiency. This means that the same frequency may be simultaneously used by different satellite switches.
Spectral efficiency is provided by the spatial diversity between the satel:Lite switches and users.
The users ma~~ be located anywhere on a land mass, on 3G the water or in the air at an altitude less than that of the low-earth orbiting satellites. For example, a person on one land mass could call a person on another land mass, a person on a boat or a person in an aircraft.
Low power hand-held mobile mounted or fixed radio 35 telephones may be used ~~n this system. The power requirement is less than 10 watts wS_th present technology.
In this system, each satellite shown is a switching unit. Current satellite communication systems act primarily 13409fi7
- 4 --as a relay station or '''bent pipe". That is, they provide fixed point-to-point communications. In the present invention, a swii=ching function is provided within each of the orbiting satE~llites.
As previou sly mentioned, each of the orbiting planes of satellites is hi<fihly inclined in the preferred embodiment of the invention. OrbitlIlg satellite planes with lower inclination are also workable. However, the lower inclination requires more satellite switching units and/or 7.0 higher orbiting altitudes to achieve whole earth coverage than does the hicfihly inclined orbiting satellite configuration.
In a preferred embodiment, highly inclined orbit configuration, it. was iFound that satisfactory earth coverage 7.5 could be accomplished caith forty-eight (48) low earth orbiting satellit=es. '.Chese satellites could be arranged in six (6) highly inclined orbiting planes, eight (8) satellites per plane. Other configurations could be used. Other lower inclined orbiting arrangements would require substantially a0 more satellites in ordE~r to achieve the same coverage of the earth as highly :inclined configuration.
Each satellite contains a satellite switching unit, suitable antennas 11 (helical antennas for up/down links and lenses for cross links,, for example) and an unfolding array 25 of solar cells 1? along with storage batteries (not shown) connected to the solar cells to provide power for the switching unit. The satellite buses or vehicles themselves are low-earth orbiting satellites such as those commercially available. The satellsites are put into orbit by a launching 30 vehicle. When in orbit., the solar cell array is opened and the switching unit thereby activated. The satellites are then individuall~r brought on line via standard telemetry, tracking and cont=rol ('.CT&C) channels to form the network.
As shown in FIG. 1, a user A with a hand-held telephone ~~5 goes off-hook. ~~his request for a channel is received by a particular satel'~ite 1,, as shown in F:CG. 1. A frequency channel is assigned to the user and the caller's desired number is then routed through the syst=em. Each satellite is 1 3 44 96 ~
As previou sly mentioned, each of the orbiting planes of satellites is hi<fihly inclined in the preferred embodiment of the invention. OrbitlIlg satellite planes with lower inclination are also workable. However, the lower inclination requires more satellite switching units and/or 7.0 higher orbiting altitudes to achieve whole earth coverage than does the hicfihly inclined orbiting satellite configuration.
In a preferred embodiment, highly inclined orbit configuration, it. was iFound that satisfactory earth coverage 7.5 could be accomplished caith forty-eight (48) low earth orbiting satellit=es. '.Chese satellites could be arranged in six (6) highly inclined orbiting planes, eight (8) satellites per plane. Other configurations could be used. Other lower inclined orbiting arrangements would require substantially a0 more satellites in ordE~r to achieve the same coverage of the earth as highly :inclined configuration.
Each satellite contains a satellite switching unit, suitable antennas 11 (helical antennas for up/down links and lenses for cross links,, for example) and an unfolding array 25 of solar cells 1? along with storage batteries (not shown) connected to the solar cells to provide power for the switching unit. The satellite buses or vehicles themselves are low-earth orbiting satellites such as those commercially available. The satellsites are put into orbit by a launching 30 vehicle. When in orbit., the solar cell array is opened and the switching unit thereby activated. The satellites are then individuall~r brought on line via standard telemetry, tracking and cont=rol ('.CT&C) channels to form the network.
As shown in FIG. 1, a user A with a hand-held telephone ~~5 goes off-hook. ~~his request for a channel is received by a particular satel'~ite 1,, as shown in F:CG. 1. A frequency channel is assigned to the user and the caller's desired number is then routed through the syst=em. Each satellite is 1 3 44 96 ~
- 5 -a distributed local processor and determines how switching of the call is to occur. Satellite 1 switches the call to the appropriate cell contained either within its own cell complement or to the appropriate satellite cell complement.
The path is determined by each satellite switching unit until the call is rece:Lved by satellite 2. Satellite 2 then routes this call to the particular hand-held user B shown in FIG. 1.
Although two hand--held users are shown, the users may be on the water, in a moving vehicle, airborne or part of a PSTN where the 1_nk is through a gateway. Each satellite is a local processor. The' system determines to which appropriate sate_lite or cell the call is to be switched.
Each satellite determines an optimal path from itself to the next appropriate satellite. These determinations may be made based upon the ot:fice code portion of the telephone number of the called user.
Each satellite typically may project four (4) or more lobes onto the earth and contain four (4) or more corresponding ce_Lls for switching. These lobes of coverage are achieved via antennas (helical typically) with fixed beam widths appropriate to t=he number of lobes. Overlapping cells will be differentiated using present cellular techniques.
These areas or lobes are shown in FIG. 3 for one particular plane of satellites about the earth. This figure depicts a high inclined orbiting satellite cellular switches. Each satellite determ_Lnes the optimal path from it to the next satellite through which to route a particular call or data transmission. These s<~tellite switches operate on data packets and therefore rnay transmit digital voice or data.
Downlink and upl_Lnk dat=a/digital voice is received on an FDM
basis demodulated and then packetized for satellite-to-satellite commun_Lcation.
FIG. 2 depicas the interconnection of a portion of one plane of satellites. In addition, the connection of the satellite to the satellite's corresponding mobile users and to the public sw_~tched telephone network is shown. Three satellites are shown. Satellite 40, Satellite 50 and Satellite 60. Satellit=e 40 is connected to Satellite 50 by
The path is determined by each satellite switching unit until the call is rece:Lved by satellite 2. Satellite 2 then routes this call to the particular hand-held user B shown in FIG. 1.
Although two hand--held users are shown, the users may be on the water, in a moving vehicle, airborne or part of a PSTN where the 1_nk is through a gateway. Each satellite is a local processor. The' system determines to which appropriate sate_lite or cell the call is to be switched.
Each satellite determines an optimal path from itself to the next appropriate satellite. These determinations may be made based upon the ot:fice code portion of the telephone number of the called user.
Each satellite typically may project four (4) or more lobes onto the earth and contain four (4) or more corresponding ce_Lls for switching. These lobes of coverage are achieved via antennas (helical typically) with fixed beam widths appropriate to t=he number of lobes. Overlapping cells will be differentiated using present cellular techniques.
These areas or lobes are shown in FIG. 3 for one particular plane of satellites about the earth. This figure depicts a high inclined orbiting satellite cellular switches. Each satellite determ_Lnes the optimal path from it to the next satellite through which to route a particular call or data transmission. These s<~tellite switches operate on data packets and therefore rnay transmit digital voice or data.
Downlink and upl_Lnk dat=a/digital voice is received on an FDM
basis demodulated and then packetized for satellite-to-satellite commun_Lcation.
FIG. 2 depicas the interconnection of a portion of one plane of satellites. In addition, the connection of the satellite to the satellite's corresponding mobile users and to the public sw_~tched telephone network is shown. Three satellites are shown. Satellite 40, Satellite 50 and Satellite 60. Satellit=e 40 is connected to Satellite 50 by
- 6- 1340967 link i. Satellite 50 is connected to Satellite 60 by link i+l. Satellite 60 is connected to the next sequential satellite of the plane (not shown) via link i+2. Satellite 40 is connected to the next preceding satellite (not shown) via link i-1. Each plane of satellites forms a ring of connected satellites around the earth.
As previously mentioned, the drawing of FIG. 2 shows one plane of the satellites. In addition, each satellite is connected to one or more satellites in other orbiting planes.
That is, each satellite: is connected to a previous and next satellite in its orbiting plane and to one or more satellites in other orbiting planes.
The intersat:ellite links link i-l, link i, etc. may be implemented via data transmission on a microwave beam or via a laser beam. E~:istinc~ technologies currently provide for such data transmission.
Connection between the satellites and its mobile users is achieved by beams j--1, and j+1, for example. These beams correspond to the' lobe:> shown in FIG. 3 and to the switching cells mentioned above. These beams are achieved via the satellite up/down link antennas which provide communication to users via the users omnidirectional antenna. The limit on the number of users that a particular satellite may handle at one time depends on bandwidth allocated plus power available on the satellite.. Typically this number may be 50,000 users per satellite.
Satellite 40 is shown connected to a trunk site or gateway 10 via beam j-.L. Any satellite, such as Satellite 40, is capable o~= transmitting and receiving data from a ?0 gateway, such as gatew<iy 10. This gateway link can be accomplished using the packetized data similar to the satellite-to-satE~llite links.
Gateway 10 .includes units which .interconnect to the public switched telephone network (PSTN) 20. All public ?5 switched telephone network users 30 are connected to the public switched t=elephone network 20. As a result of the satellite 40 being connected through gateway 10 to PSTN 20, a mobile user of the satellite cellular system which is connected direct7_y via a beam to a satellite may transmit voice or data vi~~ the r>atellite structure (satellite-to-satellite via coi:responding links), through gateway 10, through the public switched telephone network 20 to selected users of the PSTPJ 30 or. vice versa.
Each satellite provides several data transmission beams. These data transmission beams project the lobes of coverage shown in FIG. 3 which depicts four beams. Each satellite projects four such lobes. As shown in FIG. 2, a satellite may use: one or more of its beams to provide interface to a gateway. At least one beam is required for establishing a 19_nk between each gateway and the satellite.
Typically a sate7_lite 7_inks to only one gateway. One gateway provides sufficient trunking to interconnect a number of mobile users to t:he public switched telephone network 20.
Each satellite performs internal switching among its four beams or ce__ls. This is analogous to intraoffice switching for conventional telecommunication systems.
The up/down linking arrangement between the satellites c0 and its mobile users or gateways via t:he beams may transmit and receive data in the' range of approximately 2.1 to 3.9 GHz, for example. The present technology and band availability makE~s this a preferred data transmission range.
However, the scope of l.he present invention is not limited to data transmission exclusively within this range.
As previously mentioned, the data (digital voice or data) is transmu=ted in packet form. As a result, high-speed data transmission as well as voice data transmission may be accomplished via the satellite system. Data transmission rates, given the present available bandwidths, are a least 1200 baud. However, with extended bandwidth, substantially hi~~her data rates can be achieved by this system.
FIG. 4 depicts one satellite switching unit 100 directly connected to mobile users 120 via beam 102.
Satellite 100 is conne~~ted to data base computer 110 via beam 104. Satellite 100 is also connected to data base computer 130 via beam 106. Thia connection may be direct via a beam 1340967 _ _8_ 106 as shown in E'IG. 4 or indirect through other satellites to data base computer 3_30.
A mobile user might "roam" or travel in a home area.
The home area may be a city, such as New York, Los Angeles, etc. The data base connputer 110 contains all the information relative to each of its mobile users. As long as a particular mobile user is operating within his home area, all the available inj=ormat_Lon concerning that user is available at the local home area data base computer.
If, for example, a home area user in Los Angeles travels to New York Cit=y and attempts to use his satellite cellular telephone for communication, the data base computer in the user's ne5a area,, New York City, is not aware of the existence of that. user. If data base computer 110 is the mobile user's home area, Los Angeles, data base computer 110 has all the information for this particular mobile user. As a result, the mobile user would not be allowed to place calls because he was not recognized by his home area's data base computer.
In order to overcome this problem, each mobile user is periodically intc~rrogai~ed by the system as to its location so when he goes off-hook, his call for service can be recognized and routed. Howcwer, :since the data base of a particular user is stored in his home area data base computer via the c5 satellite system,, the satellite system first interrogates the home area to determine that he is no .longer there and to obtain the user's switching information. When that determination is made, the new home area's data base computer can be updated to include this "roaming" user. As a result, ~0 this user is then allowed to originate and receive calls in his new area. Bescause the satellite system interrogates the user's home data base computer to determine his location, the user can be found throughout the entire satellite system.
Thus, the system provides the capability for finding ~'~5 "roaming" users and establishing communications with them.
To facilitate tracking of each mobile user, each mobile telephone provides a control signal which is periodically monitored so that when a subscriber originates a call, the _ g _ nearest satellite can track him and through the satellite network interrogate his home data base computer to determine his pertinent customer information. The mobile telephone may automatically indicate to the satellite network a new location for updating the data base computer. This control signal allows the incoming calls of "roaming" users to be validated via satellite-to-satellite linking to the home area's data base computer.
Each satellite in the satellite cellular communication system is self-navigating. That is, it uses the Global Positioning Satellite system (GPS) or time and ephemeris data from which to compute its location information. In addition, from the fixed location of the Global Positioning Satellite system or other vehicle, each satellite can determine its position and alter its course accordingly to stay within its proper orbit while providing switching services.
Each satellite may switch a call intrasatellite (within the particular switching unit or cell) or may connect the call via a microwave or laser links (Link i, i+1, etc.) to another satellite within its plane or out of plane (adjacent). Each. satellite may distinguish a particular telephone number and determine whether that number is within its own calling area or the area of another,satellite. If it is within the area of another satellite, the call is cross-linked to the nexa appropriate satellite or cell which makes the same determination until the satellite serving that telephone number is reached. That satellite down-links to the particular mobile u~.ser sought to be called. Due to this structure, the satellite network provides a distributed nodal switching capability. Each satellite is a local switch for a particular area, but th.e area is constantly changing.
Therefore, calls are handed-off as satellites move out of the range of a particular telephone user.
Various multiplexing techniques (i.e. FDMA, TDM CDMA, etc.) may be used to enhance the transmission capability between various satellites on the links as shown in FIG. 2.
Since the s~ritching units of this system are orbiting the earth and relatively secure from tampering, this system 0 _ 134~96~
provides the capability to support secure voice and data transmission via data encryption and decryption techniques commonly known in the art. Since the switching units enjoy the security of being hundreds of miles above the earth, the system also lends itse7_f to military communication applications.
Although thf~ curr<~nt preferred embodiment of the invention has been illustrated, and that form described in detail, it will be readily apparent to those skilled in the art that various modif_'Lcations may be made therein without departing from the spirit of the invention or from the scope of the appended <~laims .
As previously mentioned, the drawing of FIG. 2 shows one plane of the satellites. In addition, each satellite is connected to one or more satellites in other orbiting planes.
That is, each satellite: is connected to a previous and next satellite in its orbiting plane and to one or more satellites in other orbiting planes.
The intersat:ellite links link i-l, link i, etc. may be implemented via data transmission on a microwave beam or via a laser beam. E~:istinc~ technologies currently provide for such data transmission.
Connection between the satellites and its mobile users is achieved by beams j--1, and j+1, for example. These beams correspond to the' lobe:> shown in FIG. 3 and to the switching cells mentioned above. These beams are achieved via the satellite up/down link antennas which provide communication to users via the users omnidirectional antenna. The limit on the number of users that a particular satellite may handle at one time depends on bandwidth allocated plus power available on the satellite.. Typically this number may be 50,000 users per satellite.
Satellite 40 is shown connected to a trunk site or gateway 10 via beam j-.L. Any satellite, such as Satellite 40, is capable o~= transmitting and receiving data from a ?0 gateway, such as gatew<iy 10. This gateway link can be accomplished using the packetized data similar to the satellite-to-satE~llite links.
Gateway 10 .includes units which .interconnect to the public switched telephone network (PSTN) 20. All public ?5 switched telephone network users 30 are connected to the public switched t=elephone network 20. As a result of the satellite 40 being connected through gateway 10 to PSTN 20, a mobile user of the satellite cellular system which is connected direct7_y via a beam to a satellite may transmit voice or data vi~~ the r>atellite structure (satellite-to-satellite via coi:responding links), through gateway 10, through the public switched telephone network 20 to selected users of the PSTPJ 30 or. vice versa.
Each satellite provides several data transmission beams. These data transmission beams project the lobes of coverage shown in FIG. 3 which depicts four beams. Each satellite projects four such lobes. As shown in FIG. 2, a satellite may use: one or more of its beams to provide interface to a gateway. At least one beam is required for establishing a 19_nk between each gateway and the satellite.
Typically a sate7_lite 7_inks to only one gateway. One gateway provides sufficient trunking to interconnect a number of mobile users to t:he public switched telephone network 20.
Each satellite performs internal switching among its four beams or ce__ls. This is analogous to intraoffice switching for conventional telecommunication systems.
The up/down linking arrangement between the satellites c0 and its mobile users or gateways via t:he beams may transmit and receive data in the' range of approximately 2.1 to 3.9 GHz, for example. The present technology and band availability makE~s this a preferred data transmission range.
However, the scope of l.he present invention is not limited to data transmission exclusively within this range.
As previously mentioned, the data (digital voice or data) is transmu=ted in packet form. As a result, high-speed data transmission as well as voice data transmission may be accomplished via the satellite system. Data transmission rates, given the present available bandwidths, are a least 1200 baud. However, with extended bandwidth, substantially hi~~her data rates can be achieved by this system.
FIG. 4 depicts one satellite switching unit 100 directly connected to mobile users 120 via beam 102.
Satellite 100 is conne~~ted to data base computer 110 via beam 104. Satellite 100 is also connected to data base computer 130 via beam 106. Thia connection may be direct via a beam 1340967 _ _8_ 106 as shown in E'IG. 4 or indirect through other satellites to data base computer 3_30.
A mobile user might "roam" or travel in a home area.
The home area may be a city, such as New York, Los Angeles, etc. The data base connputer 110 contains all the information relative to each of its mobile users. As long as a particular mobile user is operating within his home area, all the available inj=ormat_Lon concerning that user is available at the local home area data base computer.
If, for example, a home area user in Los Angeles travels to New York Cit=y and attempts to use his satellite cellular telephone for communication, the data base computer in the user's ne5a area,, New York City, is not aware of the existence of that. user. If data base computer 110 is the mobile user's home area, Los Angeles, data base computer 110 has all the information for this particular mobile user. As a result, the mobile user would not be allowed to place calls because he was not recognized by his home area's data base computer.
In order to overcome this problem, each mobile user is periodically intc~rrogai~ed by the system as to its location so when he goes off-hook, his call for service can be recognized and routed. Howcwer, :since the data base of a particular user is stored in his home area data base computer via the c5 satellite system,, the satellite system first interrogates the home area to determine that he is no .longer there and to obtain the user's switching information. When that determination is made, the new home area's data base computer can be updated to include this "roaming" user. As a result, ~0 this user is then allowed to originate and receive calls in his new area. Bescause the satellite system interrogates the user's home data base computer to determine his location, the user can be found throughout the entire satellite system.
Thus, the system provides the capability for finding ~'~5 "roaming" users and establishing communications with them.
To facilitate tracking of each mobile user, each mobile telephone provides a control signal which is periodically monitored so that when a subscriber originates a call, the _ g _ nearest satellite can track him and through the satellite network interrogate his home data base computer to determine his pertinent customer information. The mobile telephone may automatically indicate to the satellite network a new location for updating the data base computer. This control signal allows the incoming calls of "roaming" users to be validated via satellite-to-satellite linking to the home area's data base computer.
Each satellite in the satellite cellular communication system is self-navigating. That is, it uses the Global Positioning Satellite system (GPS) or time and ephemeris data from which to compute its location information. In addition, from the fixed location of the Global Positioning Satellite system or other vehicle, each satellite can determine its position and alter its course accordingly to stay within its proper orbit while providing switching services.
Each satellite may switch a call intrasatellite (within the particular switching unit or cell) or may connect the call via a microwave or laser links (Link i, i+1, etc.) to another satellite within its plane or out of plane (adjacent). Each. satellite may distinguish a particular telephone number and determine whether that number is within its own calling area or the area of another,satellite. If it is within the area of another satellite, the call is cross-linked to the nexa appropriate satellite or cell which makes the same determination until the satellite serving that telephone number is reached. That satellite down-links to the particular mobile u~.ser sought to be called. Due to this structure, the satellite network provides a distributed nodal switching capability. Each satellite is a local switch for a particular area, but th.e area is constantly changing.
Therefore, calls are handed-off as satellites move out of the range of a particular telephone user.
Various multiplexing techniques (i.e. FDMA, TDM CDMA, etc.) may be used to enhance the transmission capability between various satellites on the links as shown in FIG. 2.
Since the s~ritching units of this system are orbiting the earth and relatively secure from tampering, this system 0 _ 134~96~
provides the capability to support secure voice and data transmission via data encryption and decryption techniques commonly known in the art. Since the switching units enjoy the security of being hundreds of miles above the earth, the system also lends itse7_f to military communication applications.
Although thf~ curr<~nt preferred embodiment of the invention has been illustrated, and that form described in detail, it will be readily apparent to those skilled in the art that various modif_'Lcations may be made therein without departing from the spirit of the invention or from the scope of the appended <~laims .
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS
FOLLOWS:
1. A method of communication in a satellite cellular system, the method comprising the steps of:
communicating with a satellite; and handing-off that ongoing communication to another satellite.
communicating with a satellite; and handing-off that ongoing communication to another satellite.
2. A method of communication in a satellite cellular system, the method comprising the steps of:
communicating with a satellite; and contemporaneously terminating the communication via the communicating satellite and re-establishing the communication via another satellite, whereby the continuity of the communication is substantially maintained.
communicating with a satellite; and contemporaneously terminating the communication via the communicating satellite and re-establishing the communication via another satellite, whereby the continuity of the communication is substantially maintained.
3. A method of communication in a satellite cellular system, the method comprising the steps of:
users communicating with each other via uplinks and downlinks of a first satellite; and cellurlarly handing-off that ongoing communication by transferring the ongoing communication from the uplinks and the downlinks of the first satellite to different uplinks and downlinks of another satellite.
users communicating with each other via uplinks and downlinks of a first satellite; and cellurlarly handing-off that ongoing communication by transferring the ongoing communication from the uplinks and the downlinks of the first satellite to different uplinks and downlinks of another satellite.
4. A method of communication in a satellite cellular system, the method comprising the steps of:
users communicating with each other via cellular uplinks and cellular downlinks of a satellite; and contemporaneously terminating the communication via the cellular uplinks and the cellular downlinks of the communicating satellite and re-establishing the communication via cellular uplinks and cellular downlinks of another satellite, whereby the continuity of the ongoing communication of the users is substantially maintained via the satellite and the another satellite.
users communicating with each other via cellular uplinks and cellular downlinks of a satellite; and contemporaneously terminating the communication via the cellular uplinks and the cellular downlinks of the communicating satellite and re-establishing the communication via cellular uplinks and cellular downlinks of another satellite, whereby the continuity of the ongoing communication of the users is substantially maintained via the satellite and the another satellite.
5. A satellite cellular system comprising:
means for users communicating with each other via uplinks and downlinks of a satellite; and means within the satellite for cellularly handing-off that ongoing communication by transferring the ongoing communication to different uplinks and downlinks of another satellite.
means for users communicating with each other via uplinks and downlinks of a satellite; and means within the satellite for cellularly handing-off that ongoing communication by transferring the ongoing communication to different uplinks and downlinks of another satellite.
6. A cellular communication satellite for use in a satellite cellular system comprising:
means for receiving a cellular communication via uplinks and downlinks between users at the satellite;
and means within the satellite for handing-off that ongoing cellular communication between the users from a cell of the satellite by transferring the ongoing communication to a cell of another satellite.
means for receiving a cellular communication via uplinks and downlinks between users at the satellite;
and means within the satellite for handing-off that ongoing cellular communication between the users from a cell of the satellite by transferring the ongoing communication to a cell of another satellite.
7. A secure satellite cellular communication system for communicating among a plurality of users comprising:
a plurality of satellite switching means being positioned in orbit;
a plurality of subscriber units, each said subscriber unit for securely communicating with others of said subscriber units via uplinks and downlinks of a first satellite switching means; and means for cellularly handing-off the communication between said securely communication subscriber units by transferring the secure communication to uplinks and downlinks of a second satellite switching means.
a plurality of satellite switching means being positioned in orbit;
a plurality of subscriber units, each said subscriber unit for securely communicating with others of said subscriber units via uplinks and downlinks of a first satellite switching means; and means for cellularly handing-off the communication between said securely communication subscriber units by transferring the secure communication to uplinks and downlinks of a second satellite switching means.
8. A method of communication in a satellite cellular system, the method comprising the steps of:
users communicating with each other via uplinks and downlinks of a satellite; and cellularly handing-off that ongoing communication by transferring the ongoing communication from the uplinks and the downlinks to different uplinks and downlinks.
users communicating with each other via uplinks and downlinks of a satellite; and cellularly handing-off that ongoing communication by transferring the ongoing communication from the uplinks and the downlinks to different uplinks and downlinks.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US26384988A | 1988-10-28 | 1988-10-28 | |
| US263,849 | 1988-10-28 | ||
| CA000611234A CA1338020C (en) | 1988-10-28 | 1989-09-13 | Satellite cellular telephone and data communication system |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000611234A Division CA1338020C (en) | 1988-10-28 | 1989-09-13 | Satellite cellular telephone and data communication system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1340967C true CA1340967C (en) | 2000-04-18 |
Family
ID=33419206
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000617034A Expired - Lifetime CA1340967C (en) | 1988-10-28 | 1989-09-13 | Satellite cellular telephone and data communication system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1340967C (en) |
-
1989
- 1989-09-13 CA CA000617034A patent/CA1340967C/en not_active Expired - Lifetime
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| Date | Code | Title | Description |
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| MKEX | Expiry |
Effective date: 20170418 |