Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
7 ~ ~
WORLDWIDE T~ECOMMUNICATIONS
SYSTEM USING SATELLI~ES
BAC~GROUND OF THE lNV~LlON
This invention relates to a wireless telephone system
for employing one or a plurality o~ orbiting satellites to allow
wireless telephone users (subscribers) communication access to a
terrestrial telephone system (whether private, government or
common carrier), and particularly to a wireless telephone
system, such as a cellular system, which permits subscriber
access to terrestrial telephone networ~s while the subscriber is
roaming in areas that do not have cellular telephone services.
There is a need to provide personal communications
anywhere on the earth. Current communications systems, for
example, cellular telephone systems, require terrestrial
cellular relay stations to intercept and link a cellular
radiotelephone transmission with conventional switched telephone
users and with other cellular telephone users. All of the
existing communications systems have limited user range.
Cellular telephone systems have been proposed which
account for roamers, i.e., cellular telephone users which roam
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outside a normal service area. The American Telephone and
Telegraph Corp. (AT&T) has proposed an inter-cellular data
network for interconnecting terrestrial cellular telephone
service areas using a terrestrial packet-switched network that
has nodes at the participating cellular telephone service areas
wherein packet-switched network data are accumulated in a
database of roaming cellular telephone users. The database
therein proposed would keep track of roamers and allow
terrestrial interconnection of the roamer to the telephone
system when the roamer is located in a cellular telephone
service area that is remote from a designated home cell. Certain
data are collected which would allow routing of calls to the
roaming user, allow issuance of billing information, and allow
collection of other system operation data.
Efforts are under way to utilize satellite technology
in cellular co~m-lnications. Satellite delivered telephone
services to mobile users have been proposed as the Mobile
Satellite System (MSS) in the USA. This system is now being
implemented by the American Mobile Satellite Corp. (AMSC). It
utilizes transceivers in the mobile unit (automobile for
example) operating in the L-band (1530-1560 MHz and 1646.5-
1660.5 MHz) that comml-nicate to a satellite at geosynchronous
orbit. This system is limited to serving just a small portion
of the earth. In addition to significant expense to the end
user for the transceiver apparatus, the system is subject to
noticeable relay delay due to transmission of the signals to and
from geosynchronous orbit. Fu~thermore, the cellular telephone
service providers must nevertheless implement a costly
additional inter-system network to direct calls to the mobile
transceiver apparatus. The current system as envisaged does not
have a method for locating the roaming user and directing the
call to the user.
U.S. Patent No. 4,972,456, assigned to GTE MobileNet,
discloses a cellular telephone ~satellite~ roaming system that
uses a satellite system to permit access to the cellular
telephone system when a user is located in areas outside of
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cellular telephone system coverage. This system does not
contemplate overhead orbiting satellites, but rather the system
would employ subsidiary cell sites in a terrestrial-based
cellular communications system.
Other patents relate to general information on cellular
telephone roaming systems which permit a user of one cellular
system to use another cellular system while traveling in areas
outside a home cellular system. These patents include U.S.
Patent Nos. 4,901,340; 4,972,460; and 4,833,701.
Motorola, Inc. announced on June 27, 1990 a proposed
crosslinked satellite network under the name IRIDIUM
described in European Patent
Publication EP 365,885, published May 2, 1990.
The IRIDIUM system envisions a constellation of
seventy-seven low-earth orbiting satellites in seven circular
polar orbits for supporting cellular telephone communications on
the earth's surface. In the IRIDIUM system, all handoff and
relays of communications traffic are handled in space directly
between satellites, so that the terrestrial telephone network is
bypassed. However, ground signal processing is required to set
up and place calls. Calls originating from outside the satellite
service areas must interrogate the home location of the user in
order to identify the user. The system requires that all
satellites be linked constantly to one another. Each of eleven
evenly-spaced satellites sharing an orbit plane is contemplated
to project thirty-seven communications cells on the earth's
surface. Additionally, each satellite has four intersatellite
links, thus forming a geodesic sphere for traffic communication
paths. ~ue to cost and channel limitation, it may be presumed
that the IRIDIUM system will not compete with the services
provided by terrestrial-based cellular communications systems.
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By a document dated November 2, 1990, Ellipsat
Corporation made application to the Federal Communications
Commission for authority to construct an elliptical orbit
satellite system to support, among other things, mobile voice
services in the United States through a constellation of six
satellites. The service has been presented as complementary of
and not competitive with existing and future (terrestrial)
cellular telephone services. The system contemplates the use by
end users of dual-mode transceivers using Code Division Multiple
Access (CDMA) modulation to effect communications with earth
satellites in extended-coverage elliptical orbit.
DI8C~OSURE OF lNV~. lON
According to the invention, a radio comml]n;cation
system capable of servicing a roaming user or the like outside
the range of terrestrial relay stations includes a packet-
switched network and database of all users, a satellite
com~lln;cations system having at least one but usually a
plurality of orbiting satellites over a terrestrial satellite
service area, a satellite control center, a single network
control center, at least one Network Coordinating Gateway (NCG)
but usually a plurality spread over a large geographic area,
gateways with a home user database and a roamer database and a
plurality of terrestrial commlln;cations links, wherein call
setup is controlled by processors and databases at the NCG(s)
and control and switching rely on ground-based equipment at the
gateways such that the orbiti~g satellites are integrated into a
ground-based telephone network and tariff structure. The system
operates by effecting commlln;cation between a terrestrial
wireless telephone end user transceiver apparatus and a
terrestrial communications link via only a single relay
(comprising a forward link and a reverse link3 through a single
satellite or a succession o~ relays through other orbiting
satellites wherein the relay station (satellite) is in motion
relative to the end user transceiver apparatus and to the
terrestrial communications link, wherein the ground-based
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equipment makes the ultimate decision on linking based on
satellite ephemeris information and end user information, and
wherein the end user transceiver apparatus, the orbiting
satellite and the terrestrial communications link cooperate to
effect hand-off from a first orbiting satellite to a second
orbiting satellite other than the first orbiting satellite. The
NCG(s) are capable of receiving requests for and assigning
satellite resources on an autonomous basis. The satellites are
simple relay stations which receive, translate in frequency,
amplify, and transmit signals. The satellites do not do "on-
board" processing, which implies demodulating the signal to
bits, manipulating the bits, and remodulating. The waveform
goes through the satellite unchanged. Also, there are no direct
satellite-to-satellite communication paths in the present
invention.
The present invention offers substantial advantages
while integrating with existing telephone systems. The invention
allows wireless telephone with automatic switching (cellular)
voice, data and facsimile communication to the public-switched
telephone network in areas not served by terrestrial cellular
telephone systems. The invention in particular provides enhanced
roaming cellular telephone services to cellular telephone
service areas that have poor coverage, gaps in coverage, and
other service area degradation. As a consequence, there is also
an increased ability to provide emergency communications
services, such as reporting of medical emergencies, roadside
breakdowns, tracking of stolen cars and other similar services
in all areas served by satellite.
The invention will be better understood by reference to
the following detailed description in connection with the
accompanying drawings.
BRIEF DE8CRIPTION OF THE DRAWING8
Fig. 1 is a figurative illustration of an integrated
wireless telephone and orbiting satellite communications system
in accordance with the invention.
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Fig. 2 is a figurative illustration of the integrated
wireless telephone and orbiting satellite communications system
showing how a first type of duplex communications circuit may be
set up.
Fig. 3 is a figurative illustration of the integrated
wireless telephone and orbiting satellite communications system
showing how a second type of duplex communications circuit may
be set up.
Fig. 4 is a system block diagram according to the
invention.
Fig. 5 is a block diagram of a wireless transceiver
apparatus for use by an end user.
Fig. 6 is a block diagram of a gateway terminal unit
for use in a cellular system according to the invention.
lS Fig. 7 is a block diagram of a network coordinating
gateway for use in a system according to the invention.
Fig. 8 is a block diagram of a network control center
for use in a system according to the invention.
Fig. 9 is a block diagram of a satellite system for use
in a system according to the invention.
Figs. lOA-lOL together are a flow chart of operation of
a specific embodiment of the invention.
DET~TT~n n~CCPTPTION OF q~ PRIS~c~usv EMBOVl~ ~S
An integrated wireless/satellite communications system
10 according to the invention is shown in Fig. 1. The system 10
may include private, government or cellular telephone systems
which themselves comprise gateways 12, 14, 16, 18, each having
the means to communicate with the satellite system 10. The
gateways may be conventionally-defined metropolitan service
areas (MSAs) 12, 14, 16 and rural service areas (RSAs) 18,
government telecommunications gateways, or private network
nodes. The system 10 may further include according to the
invention a network database 20 of users, a satellite
3S communications system with a single one or a plurality of low-
earth orbit satellites 22, each of which services a (moving)
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satellite service area 24, a network control 25, a satellite
control center 26, at least one network coordinating gateway 28,
a representative roaming end user 30, a packet switched network
32, and a plurality of satellite communications links, including
for example satellite telephone communications links 34, 36, a
network communications link 38, and a satellite control link 40.
This detailed description uses a cellular terrestrial
communications system as an example. As stated above, the
invention may alternatively be used with private or government
communications systems which may be slightly different than the
example given here. In government systems, the communication
links may be encrypted. In government and private systems, the
ground nodes may be connected only to a private network.
In the exemplary cellular telephone system, there are
contemplated existing and future terrestrial wireless telephone
systems. Herein they may be collectively referred to as a
Terrestrial Service Areas (TSAs).
In accordance with the invention, there is provided a
Satellite Service Area (SSA) 24 (which may be moving) having a
communications link 34 capable of servicing any roaming user 30
within the SSA 24. The satellite control center 26 is to provide
for proper operation of the satellite system 22 by means of
Satellite Control Links (SCL) 40 to and from a plurality of
satellites which are passing overhead. Other links include the
Network Coordinating Link (NCL) 38, the satellite-to-user link
34, and the satellite-to-gateway link 36.
The TSAs are linked ~by a nationwide packet switched
network (NWN) 32 which may be used to establish the network
database 20 of users. The NWN 32 may provide the service areas
with information necessary to locate roaming users, log in
users, log out users, allocate satellite resources, and set up
calls.
The satellite system 22 may comprise a single satellite
or a constellation of many satellites preferably in low-earth
near circular or possibly elliptical orbits. Each satellite is
provided with a communications subsystem which is capable of
"~ 7 ~7~
receiving uplink signals, converting them to downlink
frequencies, amplifying the signals, and transmitting the
signals back to the earth. The satellites do not incorporate
satellite-to-satellite links nor serve as bypass to ground-based
telecommunications facilities. The satellites are simple 'bent-
pipe" repeaters, do not perform any on-board signal processing
of the communications traffic, and do not have regenerative
repeaters. By on-board signal processing (a term commonly used
in the satellite industry), it is meant that the satellite
brings the RF signals down to bits, and further that the
satellite switches or otherwise manipulates the signals. The
lack of on-board signal processing of the communications traffic
is in sharp contrast to the prior art where on-board signal
processing is performed, e.g., U.S. patent 5,073,900 to
Mallinckrodt (col. 4 lines 35-39) and European patent
publication 0 365 885 to Bertiqer (col. 4 lines 7-9). As used
herein, "communications traffic" means the voice, data, or other
messages that a~e passed from the user 30 to the caller 107,
108, (Fig. 4) and 50, (Fig. ~) and vice versa.~communinications traffic~
does not include control signals that are sent from the earth to the
satellite 22. A regenerative repeater is defined in Sklar, B.,
Diqital Communications (Prentice Hall 1988), p. 232 as one which
demodulates and reconstitutes the digital information embedded
in the received waveforms before retransmission. A regenerative
repeater is defined in Pritchard, W.L. et al., Satellite
Communication SYstems Enqineerinq (Prentice Hall 2d ed. 1993),
p. 401 as follows: "... a regenerative repeater, utilizes
onboard signal processing of digital signals..."
The satellite control link 40 provides remote control
of satellite components and configurations. The network
coordinating link 38 provides for data transfer to and from a
network coordinating gateway 28 for the purpose of establishing
communications to and from a roaming user 30, for logging on to
the system (registration). The wireless telephone links 34, 36
are used for voice and data communications, position location
and other services between the user and various wireless
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telephone systems. The network control center 25 is used to
coordinate between NCGs 28, keep the network database 20 updated
to all NCGs 28, collect billing and system information, and
coordinate any information from the satellite control center 26
that the NCG(s) 28 might require, such as satellite ephemeris
and health.
The wireless telephone user equipment preferably may be
any commercially available unit that has the capability of
digital signal generation and a compatible modulation scheme
with the network into which it is to be integrated, combined
with digital and frequency generating equipment compatible with
the satellite system. Code Division Multiple Access (CDMA)
modulation or other modulation compatible with the satellite
relay system is contemplated.
SYST15M OPERATION:
Operation of the system according to the invention is
first described in connection with Fig. 2 and Fig. 3 as follows:
Notification is a first procedure. Each user has a home
gateway (HG). Each gateway 12, 14, 16 has a home user database
31 which contains information of all the users for which that
gateway is home. Each gateway 12, 14, 16 has a roamer database
27 of all the active roamers in the gateway's service area. The
roaming user 30 notifies the system, either by a special control
signal to the present satellite system 22 as shown in Fig. 2, by
a relay path A-C to a networ~ coordinating gateway (NCG) 28, or,
if in service area range, by ~ special control signal to the
nearest service area terrestrial base station 38, that the user
30 desires to use the satellite communications system. The
control signal is repeated by all satellites 22 in view of the
user 30 to any NCG(s) 28 in view of the satellite(s) 22. The
NCGs 28 have algorithms (such as closest to user) to choose
between or among NCGs 28. An NCG 28 is selected and takes the
request. The special control signal is processed by the NCG 28
and routed outward from the NCG 28 to the packet switched
network 32. The NCG 28 selects an Active Gateway (AG) 16, which
2105738
will handle all calls to and from the user 30 by a system
selected method (such as gateway closest to user, or special
gateway by request of user). The NCG 28 sends a message to AG
16. The network database 20 is updated to include the user 30
as a roamer in the satellite service area 24. The NCG 28 notes
the acceptability of the user 30, and the network database 20 is
updated to show the user 30 roaming in the SSA 24. The roamer
database 27 of active gateway 16 is then updated to show the
user 30 to be in the Satellite Service Area (SSA) 24. The
user~s home gateway database is updated to show that the user 30
is being serviced by active gateway 16. This condition exists
until the user 30 re-enters a service area of the terrestrial
cellular system or until the user 30 enters a different
satellite service area 24.
There are two kinds of telephone calls: incoming
tinbound) to the satellite system and the terrestrial network
from the (roaming) user 30; and outgoing (outbound) to the user
from the satellite system and the terrestrial network.
Incoming calls initiated by the user 30 begin with a
request to access the public switched telephone network (PSTN~.
The AG 16 processes the request and checks its databases 27, 31
for the user 30. Depending on ephemeris, satellite resources,
gateway resources and call destination, the call is accepted by
the AG 16. If necessary, the AG 16 requests satellite resources
from an NCG 28. The AG 16 could be a user's HG or any remote
TSA. The call is set up, for example as shown in Fig. 2, via
path A-B, under database cont~rol of the designated NCG 28 and
the selected TSA 16. The remote TSA 16 (the AG) then
acknowledges the request and processes the call to the call
destination 50 through a public switched circuit 17. Channels
and/or codes are assigned by the AG 16 assisted by the
designated NCG 28; and the gateway roamer database 27 at the
AG 16 is updated to show that the user equipment is busy. A
handoff processor 33 at the AG 16 is updated to enable handoff
from one satellite to another if required. The AG 16 notifies
the designated NCG 28, via the packet switched network 32, that
210.~738
the call is in process and states the satellite resources that
are being used, to allow the NCG 28 to note in its database 20
that the user 30 is busy. The home user database 31 of the
user's HG is updated to show the user 30 as busy and to show the
user~s AG 16.
Subsequent to call setup, the user 30 and the call
destination 50 are connected via two-way wireless (cellular)
telephone communications links A-B, as shown in Fig. 2. These
communications may be carried out using spread spectrum
modulation techniques and Code Division Multiple Access (CDMA)
channels, or other modulation compatible with the satellite
system, using equipment located at the user 30 position, and
equipment located at the remote TSA 16 in the satellite service
area (SSA) 24. The CDMA or other modulation signal is converted
to a voice signal at both the user 30 end and the remote TSA 16.
At the user 30 end, the signal is converted either to an analog
signal for voice and sent to a loudspeaker or headphones, or
converted to a digital signal and sent to another device for
further processing of data. At the remote TSA end 16 the signal
is received by antenna 38, converted to either a voice signal or
digital data, and sent via a PSTN switch (not shown) for further
routing via the public switched telephone network 17 to the call
destination 50. After communications is ended, a signal from
either end 30, 50 of an "on-hookH condition signifies end of
communication.
The call termination processes proceed as follows: the
AG 16 notifies the designated~CG 28 of call termination and
that the channel is free. The network database 20 is notified
of call termination and billing information, and is updated to
show the user 30 as not busy. The AG 16 updates its roamer
database 27 and resets handof~ processor 33. The AG 16 notifies
the user's HG via packet network 32 that the user 30 is not
busy. The HG updates its home user database 31 to show user 30
not busy.
Consider the situation where a remote location called
the "caller~' 50 desires to make a telephone call to a cellular
7 ~ ~'
telephone user 30 that is roaming and is not located in a
terrestrial cellular telephone service area (TCTSA~. The call
is initiated as shown in Fig. 3. The caller 50 uses the PSTN 21
to call the user's wireless (cellular) telephone number at the
userls HG 12 or perhaps some other equivalent location. The
call is transferred by the PSTN switch to the user's HG 12. The
HG 12 equipment 23 processes the call and, by accessing the home
user database 31, finds that the user 30 is roaming in the
satellite service area 24 and thereby knows to route the call ~o
the AG, which, for this example, we assume is the same as HG 12.
The HG equipment 23 then routes a request for --oute planning to
the route planner 25. The route planner 25 routes the call to
the AG 12. In this example, the AG 12 is the HG 23, so no more
call routing is required. The home TSA 12 makes a call setup
notification to the designated NCG 28 via packet network 32.
The AG 12, upon receiving the request signal, checks its
database 31 for user status, processes the information, and
based on the information in its database 31, satellite resources
and AG 12 resources, accepts or rejects the call.
If the AG 12 is another GTSA (not the user's ~G), such
as equipment 16, HG 12 requests a call setup to the AG 16 via
the packet network 32. The AG 16 checks satellite 22 channel
capacity and requests satellite 22 resources from the designated
NCG 28 if necessary via the packet network 32. The AG 16 hails
the user 30 and t-ansmits call setup information via the
satellite 22. The AG 16 notifies the HG 12 to route the call
to the AG 16 and to update its home user database 31 to show the
user 30 is busy. The call setup is as described above for the
home TSA 12.
If it accepts a call for connection, the AG 12, 16 sets
up the call. The AG 12, 16 transmits the request for access to
the user 30 through satellite 22. If accepted by the user 30, an
ac~nowledgment is transmitted to the AG 12, 16 through satellite
22. The AG 12, 16 updates the database 31 to show the user 30
to be busy, and signals the designated NCG 28 to update the
networ~ database 20 to show the user 30 to be busy.
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Subsequent to call setup, the user 30 and the caller 50
are connected via two-way wireless telephone communications
links via path A-D, as shown in Fig. 3. The AG 12, 16 notifies
the designated NCG 28 that the call is in progress and states
the satellite resources that are being used. The designated
NCG 28 updates the network database 20. The AG 12, 16 notifies
the HG 12 that the call is in progress. The HG 12 updates its
home user database 31 to show the user 30 busy. As before, the
communications are carried out over Code Division Multiple
Access (CDMA), or other compatible modulation, channels using
equipment located at the user 30 position, and equipment located
at the remote TSA 12 in the satellite service area 24. After
communications are ended, a signal from either end of an "on-
hook~ condition signifies end of communication.
The user 30 at some point may decide to either
terminate roaming in the SSA 24 or may re-enter a terrestrial
cellular service area. If the user 30 desires to terminate
roaming in the SSA 24, he has two options: First, the user 30
may put his equipment on standby, thereby causing his equipment
to not respond. This has the effect of temporarily making the
user 30 unavailable for taking outbound calls to him.
Alternatively, the user 30 may remove his identifying codes from
the network database 20 of SSA 24 roamers. To effect the
removal from the database 20, the user 30 must notify the AG 12,
16, typically via satellite 22, of intent to discontinue roaming
in the SSA 24. The AG 12, 16 receives the user 30 intention,
updates its roamer (or home us*r) database 27, 31 by deleting
the user 30, and notifies the designated NCG 28 to update the
network database 20 to show the user 30 as not roaming in the
SSA 24. The AG 12, 16 notifies the HG 12 to update its home
user database 31 to show that the user 30 is no longer roaming
in the SSA 24.
In Fig. 4 there are illustrated the principal control
elements in a cellular telephone system 10 for providing voice,
data and other electronic telephone services to portable and
mobile telephones located anywhere in a large geographical area.
13
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Terrestrial cellular telephone systems (TCTSs) 101, 102, which
are types of gateways 12, 14, 16, 18, are provided with antennas
103, 104, respectively, located at many base sites throughout a
geographical area to be served (e.g., SSA 24 o~ Figs. 1-3). The
TCTSs 101, 102 are connected to a telephone central office (TCO)
106 with voice (and data) landlines 120, 121 and with signaling
network (packet) land lines 130, 131. The TCTSs 101, 102 may be
any commercially available cellular telephone system or other
gateway equipment (e.g., private systems). The TCTSs 101, 102
may be equipped with satellite interface equipment (SIEs) 201,
202, respectively. The SIEs 201, 202 have second antennas 203,
204, respectively, that have the purpose of transmitting signals
to and receiving signals from satellites 301, 302.
A network coordinating gateway (NCG) 28 is like a TCTS
101, 102 without the cellular telephone switch (it can be co-
located with a TCTS). A NCG 28 has satellite interface
equipment 206, with at least one antenna 20S. The satellite
interface equipment 206 is connected to the packet network 32
through line 132 and interfaces with the coordination equipment
610. The TCTSs 101, 102 are connected to NCG 28 by landline 132
via TCO 106 or other su~itable means. The NCG 28 is connected to
network control (NC) ~ by landlines 140,141 via the TCO 106 or
other suitable means. The NC 25 is equipped with a network
controller 404 and the network database 20.
The TCO 106 connects the NC 25 to the NCG 28, and
connects the NCG 28 to the TCTSs 101, 102. The TCO 106 also
connects the TCTSs 101, 102 to the call destination telephones
107, 108. These telephones 107, 108 may be any commercially-
available product that can interface to a public switched
telephone system and transmit voice and/or data. Also shown in
Fig. 4 are Cellular Satellite Telephones (CSTs) 501, 502 which
can be the users described in ~igs 1-3. The Cellular Satellite
Telephones ~01, 502 are equipped with Cellular Telephones (CT~
503, 504, respectively, and antennas 505, 506, respectively,
which transmit to and receive signals from the TCTSs 101, 102
via antennas 103, 104, respectively. In addition, the cellular
14
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satellite telephones 501, 502 are equipped with Satellite RF
Units (SRFUs) 520, 521 and antennas 522, 523, which transmit to
and receive signals from the satellites 301, 302 (Fig. 4). The
CSTs 501, 502 also each include a Satellite Control Unit (SCU)
530, 531, respectively, which provides signaling functions to
the network.
Referring to Fig. 5, there is illustrated in more
detail a CST 501 of Fig. 4. The CST 501 may include a
conventional cellular telephone 503 equipped with a transceiver,
a handset, and many options (not shown), and it is expected that
the terrestrial roaming network may require digital terminals
for this purpose. The cellular telephone 503 accommodates
multiple telephone numbers and may be assigned a special
satellite roaming number. The CST 501 is further equipped with
a satellite control unit (SCU) 530, which includes storage for a
user number 532, a request/ACK generator 533 and a retry
generator 534. The CST 501 also includes a satellite RF ~nit
520, which includes encoders 524, decoders 525, a modem 526 and
a satellite RF converter 527.
When a satellite 22 is about to lose communication
between a user 30 and a TCTSA 12, 14, 16, 18 that is handling
the call, the active gateway 12, 16 initiates requests for a
handoff to another satellite 22. Satellite resources are
coordinated between the AG 12, 16 and the NCG 28 via the packet
network 32. The links to establish the handoffs are shown in
Fig. 4, which shows TCTS101 handing off the links to CST 501
from satellite 302 to satellite 301.
Referring to Fig. 6, there is shown in more detail a
unit of the terrestrial cellular telephone system (TCTS) 101.
The TCTS 101 with switch 221 may be any commercially available
cellular telephone system or other gateway equipment (e.g., a
private system). The TCTS 101 is interfaced to the Telephone
Central Office 106 via landlines 120. The system is also
interfaced by way of a signaling network (packet) to the TCO 106
by landlines 130 and there through to a network coordinating
gateway 28 (Fig. 4) via landline 132 or other suitable means.
~ 210 ~ 7 3 8
The TCTS cellular equipment 101 also includes special
equipment according to the invention for the purpose of
communicating to and from user Cellular Satellite Telephone
cs~
~ ) 501, 502 by way of radio links through the satellites 301,
302, 22. This special equipment, called the Satellite Interface
Equipment (SIE) 201 (Fig. 6), includes a handoff processor 2S0,
RF power monitor 251, and a Route Planner 240 which processes
outbound calls to users 30 from other callers 50 and provides
route planning to connect a caller 50 to a user 30 depending
upon user location, the satellite ephemeris, and other planning
criteria. The SIE 201 also includes a Cellular Telephone
Interface Unit 230 that processes and conditions the voice and
data signals and interfaces the call reguests, call termination
signals, and ACK data signals to the encoder 232, the Cellular
Telephone System 221 and the ~all Termination Processor 233. A
Call Request Processor 235 takes access data from the decoder
234, via the retry generator 239, and either directs it to the
Cellular Telephone Interface Unit 230 or routes it to the ACK
generator 236. Signals from the ACK generator and the Call
Termination Processor 233 are applied to the encoder 232. Modem
237 modulates signals from the encoder 232 and demodulates
signals from the Satellite RF Unit 238. The output from the
antenna 203 is applied to the RF unit 238 to receive signals
from the satellites 301, 302, 22. Likewise, the output of the
satellite RF unit 238 is applied to the antenna 203 in order to
transmit to the satellite(s) 301, 302, 22. The handoff
processor 250 monitors a call~signal and begins handoff
procedures when a signal is below a threshold or there is a
satellite 301, 302, 22 that would provide better service to the
user. The RF power monitor 251 checks the channel capacity of
the satellite(s) 301, 302, 22 in view of the gateway 12, 14, 16,
18, and informs the handoff processor 250 of channel
- availability. Gateway controller 260 checks information fed to
it by NCG 28 to determine availability of satellite 22
resources.
210.573 8
Referring to Fig. 7, there is shown in more detail the
Network Coordinating Gateway (NCG) 28. The NCG 28 may be co-
located at a TCTS 101, 102 and may use the SIE 206. The
difference between a regular gateway and a NCG 28 is that a NCG
28 comprises commercially available equipment with the express
purpose of monitoring the satellite(s) 22, of assigning user
channels, of creating and maint~in;ng a database 20 of cellular
telephone users that are nationwide or worldwide, and of
processing inbound and outbound call requests, and does not
necessarily have a cellular telephone switch.
A NCG 28 has at least one antenna 205 for communication
with the satellites 22 but usually a plurality of antennas 205
so that the NCG 28 can be in communication with all satellites
22 in view. This equipment 28 may consist of computers, memory
storage devices, interface equipment, modems and the like. This
system may contain or be interfaced to additional databases 613
and database management systems. The database 20 is mana~ed by
a network computer 612 and receives and exchanges data from and
with the Terrestrial Cellular Telephone Systems 101, 102 by way
of landline 132 connected via the TCO 106. The satellite
monitor 611 monitors the satellite(s) 22 in view of the NCG 28
and reports on channel capacity to the network computer 612.
The satellite database 613 contains information about which
satellites 22 will be in view of the NCG 28 at what time and at
what look angles, and indicates the satellite resources that are
available. The network computer 612 uses this information to
determine satellite 22 loading and assign channels
appropriately. The network computer 612 is connected to the
packet network 32 and to the encoder 232 and decoder 234 through
the cellular telephone interface unit (CTIU) 230. The CTIU 230
recognizes network requests such as roaming request, inbound
call requests, ACK regarding network requests and discontinuance
requests from users and routes those requests to the network
computer 612. The CTIU 230 receives messages from the network
computer 612 regarding ACK of requests from the user 30, call
setup information, calling information and hailing requests to a
210~738
specific user 30, and sends those messages to encoder 232. The
network computer 612 receives from the packet network 32 roaming
requests from the TCTSA 12, 14, 16, 18, gateway availability
from gateways 12, 14, 16, 18, ACK from gateways 12, 14, 16, 18,
user status from gateways 12, 14, 16, 18, channel usage from
gateways 12, 14, 16, 18, billing information from gateways 12,
14, 16, 18, system information and database information from
network control 25, requests for channel assignments from
gateways 12, 14, 16, 18, and logout requests from the TCTSA 12,
14, 16, 18. The network computer 612 transmits through the
packet network 32 to network control 25 satellite capacity,
billing information, database information and other system
information to the TCTSA 12, 14, 16, 18 regarding login and
logout requests, and to the gateways 12, 14, 16, 18 for channel
requests, user activity in the gateway's service area, call
setup information, location of home users, and other system
information.
Referring to Fig. 8, there is shown in more detail the
Network Control (NC) 25. The NC 25 comprises commercially
available equipment with the express purpose of creating and
maintaining a database 20 of cellular telephone users that are
nationwide or worldwide, collecting all billing and system usage
information, coordinating between NCGs 28, and coordinating
satellite 22 performance information that is pertinent to the
system and to the NCGs 28. This equipment 25 may consist of
computers, memory storage devices, interface equipment and the
like. This system 25 may cont~ain or be interfaced to additional
databases and database management systems. The network database
20 is managed by a network controller 404, receives and
exchanges data from and with the network coordinating gateway(s)
28 by way of landlines 140,141 connected via the TCO 106 or
other suitable means, and receives and exchanges data from and
with the Satellite Control Center 26.
A functional block diagram of the satellite 22 payload
301 is shown in Fig. 9. The satellite payload 301 comprises
Satellite Communications RF Translator (SCT) 306, communications
210~738
uplink RF receiver 302, communications downlink RF transmitter
303, satellite control uplink/downlink RF receiver/transmitter
304, satellite controller 305, and support elements not shown.
The communications uplink RF receiver 302 receives
signals from transmitters on the ground by an antenna, and
applies the signals to the SCT 306. The SCT 306 translates the
signals from the uplink frequency to the downlink frequency and
applies the signals to the communications downlink RF
transmitter 303. The communications downlink RF transmitter 303
amplifies the signals, and transmits the signals to the ground
by an antenna.
A separate set of satellite control links, shown as the
satellite control uplink/downlink receiver/transmitter 304, are
used for controlling the satellite subsystems, for maintA;ning
the satellite operation software, and for reporting subsystem
status. The uplink signals to the satellite 22 are sent by
receiver 304 to satellite controller 305, where they are
downconverted to baseband. The satellite controller 30S decodes
the control messages and performs the appropriate actions.
Digital signals from other portions of the satellite 22,
databases, buffers, storage, and satellite operation software
are applied to the satellite controller 305. The satellite
controller 305 encodes these signals and sends the signals to
the satellite control uplink/downlink receiver/transmitter 304
for conversion to RF and transmission to the ground. Satellite
controller 305 does not handle any of the communications
traffic, i.e. the voice, data~or other messages that are passed
from the user 30 to the caller 107, 108, 50 and vice versa. As
stated previously, there is no on-board signal processing of the
communications traffic in the present invention.
It is useful to understand the operation of the system
by users and callers. A user 30 is defined to be an operator
who is equipped with a device capable of requesting access,
making and receiving calls with equipment 501, 502 shown in Fig.
4 via satellites 301, 302, 22 cellular telephone system
equipment 101, 102 or the equivalent, terrestrial lines or
_ 210~73~
equivalent means 120, 121, telephone central office or other
central switching means 106, and terrestrial lines or other
equivalent means 123, 124 to callers 107, 108, 50. A caller is
defined to be an operator who is equipped with a device capable
of requesting access, making and receiving calls with equipment
107, 108 via terrestrial lines or equivalent means 123, 124, and
telephone central office or other switching 106, and terrestrial
lines or equivalent means 120, 121 and cellular telephone system
equipment 101, 102 or the equivalent, and via satellites 301,
302, 22 to the user 30 equipped with equipment 501, 502.
The following description details the method of
operation of the system for carrying out several processes.
These processes are;
#1 Establishing a user 30 as a roamer in a SSA 24
#lA Request for roaming by user 30 in SSA 24
#lB Request for roaming by user 30 in a TCTSA 12, 14, 16, 18
#2 Call initiation by a user 30 (an Inbound Call)
#2A Call request (Inbound)
#2B NCG 28 acceptance of calls from user 30
#2C Inbound call setup process, AG 16 acceptance
#2D Inbound call acceptance retry notice
#2E Inbound call duplex operation
#2F Handoff of inbound and outbound calls
#2G Call termination of inbound and outbound calls
#3 Call initiation by a caller 50 (an Outbound Call)
#3A Call request (Outbound)
#3B NCG 28 acceptance of calls from caller 50 (Outbound)
#3C Outbound call setup process, AG 16 acceptance
#3D Outbound call duplex operation
#3E Handoff of Outbound calls
#3F Call termination (Outbound call)
#4 Notification to discontinue roaming by user 30
-- --~
210~7~8
#4A Request to discontinue roaming by user 30 in SSA 24
#4B Request to discontinue roaming by user 30 in a TCTSA
12, 14, 16, 18
These processes and their sub-processes as explained
hereinafter are outlined in a flow chart shown in Figs. 10A
through 10L.
ES$ABLISHING A USER 3 0 AS A ROAMI~R IN A SSA 24:
Consider a user 30 wishing to be established as a
roamer. The user 30 must establish that he is an authorized
user 30 to have access to the commt]n;cations facility ~Fig. 4;
Fig. 10A Step B, Fig. 10B). The user 30 has two options; he may
notify Network Coordinating Gateway (NCG) 28 of his intention
while in a SSA and out of range of a TCTSA 12, 14, 16, 18 and
have his request processed via a satellite relay to the NCG 28
(Fig. 10B, Steps Bl, B2, B3); or he may make his request via a
participating TCTSA 12, 14, 16, 18 (Steps Bl, B4, B3). These
two cases are now described:
REQUEST FOR ROAMING BY U~ER 30 IN ggA 24:
Referring to Fig. 2, a method of a user 30 signaling the NCG
28 that he wishes to roam is illustrated. In this case the
potential roamer 30 is located in the SSA 24 and not in a TCTSA
12, 14, 16, 18. The user 30,~operating the wireless satellite
telephone 501, 502, either manually or automatically actuates
user request Unit 535 (Fig. 5) which activates Request/ACK
generator 533 and formats a preset user number 532 onto a data
stream and passes it to encoder 524. Encoder 524 processes the
datastream into a signal and routes it to modem 526 for
modulating the signal, which passes it to Satellite RF Converter
527, which then activates the satellite antenna 522 and causes
an RF signal to emanate from the device.
The user 30 transmits data to the NCG 28 through the
satellite 22. The data include user identification number and a
request for roaming. This signal is transmitted via link 34A in
Fig. 9 to the satellite 22. The signal is received by the
S communications uplink RF receiver 302, which applies the signal
to the SCT 306, which translates the frequency of the signal,
and applies it to the communications downlink RF transmitter 303
which amplifies and transmits the signal to the ground by an
antenna. The satellite 22 transmits the signal via link 38C to
the NCG 28~ The signals are received by the NCG equipment 28
(Fig. 7) by antenna 205 and applied to the satellite RF unit(s)
23~. There may be more than one satellite 22 in view of the
user 30. Each satellite 22 repeats the signal to the ground.
There may be one or more NCGs 28 in view of each satellite 22.
After processing by satellite RF unit(s) 238, the
signal is applied to modem 237 for demodulation and thence to
decoder 234. After decoding, the signal is applied to cellular
telephone interface unit 230 which recognizes the data as a
login request and passes the data to network computer 612.
Network computer 612 chooses to accept the call or not based on
an algorithm which contains the location of the other NCGs 28
and based on the user 30 location. The NCG 28 may perform a
position location on the user 30 if necessary.
Network computer 612 sends an ACK signal on a preset
frequency to the user 30 by sending a signal to cellular
telephone interface unit 230 which signals call request
processor 235. Call request processor 235 signals ACK generator
236 to signal the user 30 through the satellite 22 that it has
received the roaming request. This ACK signal is applied to
encoder 232 and modem 237 and passed to satellite RF unit(s)
23~. ~fter processing, it is applied to antenna 205 for
transmitting to satellite 22.
Referring to Fig 9, the ACK signal is transmitted over
link 38C~ to satellite 22. The ~ignal is received by
satel ite 22 and transmitted over link 36A to the user 30.
,L
2105738
Referring to Fig. 5, the signal is received by the user
satellite telephone 501 by its antenna 522 and applied to the
userls satellite RF converter 527. The resulting signal is
passed to modem 526 for demodulation then decoded by decoder
525. The resulting signal is sent to request/ACK generator 533
which shifts the cellular telephone 503 to stand-by.
Network computer 612 also selects the active gateway
(AG) 16 that is going to be used based on user 30 location or
other criteria given by the system 10. Network computer 612
then verifies the user 30 as acceptable for authorization to use
the system 10. If the user 30 is not acceptable for
authorization to use the system 10, network computer 612 does
not update network database 20 and ignores the user 30 request.
Upon acceptability of the user 30 as an authorized user, network
computer 612 updates network database 20 to show the user 30 as
being active, the user 30 location, and the selected AG 16. The
computer 612 interrogates the network database 20 for the
identity of the user's home gateway (HG) . The HG may be outside
the confines of SSA 24, but for purposes of this discussion we
will assume that HG is one of 12, 14, 16, 18.
The network computer 612 sends the user ID along with
user location and the selected AG 16 to the user's HG 12, 14,
16, 18 via the packet network 32 through landlines 132. The
data are received by the HG 12, 14, 16, 18 by the cellular
telephone system 101 through landlines 130. The cellular
telephone system 101 updates the home user database 31 to show
the user 30 as roaming, the user's location and the AG 16.
Network computer 612 sends user ID, user location and
the call setup information to the AG 16. This information might
include call setup transmit and receive channels, transmit and
receive codes if CDMA is used, and other information, by
formatting a message which contains the data and sending them to
the cellular telephone interface unit (CTIU) 230 (Fig. 6), which
routes the data to the packet switch network 32 through
landlines 132. The data are received by the AG 16, 102 by
cellular telephone system 222 through landlines 131. The
23
7'~ ~ ~
'_
cellular telephone system 222 updates the roamer database 27 to
show the user 30 as roaming, the user's location, and call setup
information.
The AG 16 then sends call setup data to the user 30
through the selected satellite 22. This information mi~ht
include call setup transmit and receive channels, transmit and
receive codes if C~MA is used, and other information, by
formatting a message which contains the data and sending them to
the cellular telephone interface unit 230 (Fig. 6), which
applies the signal to encoder 232 and modem 237 and thence to
satellite RF unit(s) 238. After processing, the signal is
applied to antenna 203 for transmitting to the satellite 22.
Referring to Fig. 9, the ACK signal is transmitted over link 36B
to the satellite 22. The signal is received by the
lS satellite 22 and transmitted over link 36A to the user 30.
Referring to Fig. 5, the signal is received by the user
satellite telephone 501 by its antenna 522 and applied to the
user's satellite RF converter 527. The resulting signal is
passed to modem 526 for demodulation, then decoded ~y decoder
525. The resulting signal is sent to request/ACK generator 533
which shifts the cellular telephone 503 to the proper channel
for non-CDMA operation, or provides modem 526 with t~e call CDMA
codes for reception and goes to ready.
REQU13ST FOR ROAMING BY A UgER 30 IN A TCTSA 12, 14, 16, 18:
The second method of requesting roaming in an SSA 24 is
to make the request while in a TCTSA 12, 14, 16, 18. The user
30 either manually or automatically activates his wireless
satellite telephone transceiver User Request Unit 535 (Fig. S).
~ signal, including the user number, location, and codes to
indicate the user 3~ wishes to roam in the SSA 24, is sent to
the Cellular Telephone System (CTS) 101, 102 by antenna 505
(Fig. 4; Fig. lOB, Step B4). The CTS 101, 102 formats a data
signal which is conveyed via landline 130, 131 to the TCO iO6
and then to the NCG 28 via landline 132.
210~738
....
Referring to Fig. 7, the signal is then applied to
network computer 612, which updates network database 20 and
interrogates database 20 to verify the user 30 as acceptable for
authorization to use the system 10. Network computer 612 then
verifies the user 30 as acceptable for authorization to use the
system 10. If the user 30 is not acceptable for authorization
to use the system 10, network database 20 is not updated and
network computer 612 sends a message to the CTS, 101, 102 to
ignore the request via the packet network 32 through landlines
132. Upon acceptability of the user 30 as an authorized user,
computer 612 selects the active gateway AG 16 that is going to
be used and updates network database 20 to show user 30 as being
active, user location, and the selected AG 16.
Network computer 612 sends user ID, user location and
the call setup information to the AG 16. This information might
include call setup transmit and receive channels, transmit and
receive codes if CDMA is used, and other information, by
formatting a message which contains the data and sending them to
the cellular telephone interface unit (CTIU) 230 (Fig. 6), which
routes the data to the packet switch network 32 through
landlines 132. The data are received by the AG 16, 102 by
cellular telephone system 222 through landlines 131. The
cellular telephone system 222 updates the roamer database 27 to
show the user 30 as roaming, the user's location, and call setup
information.
Network computer 612 interrogates the network database
20 for the user's home gateway (HG) 12, 14, 16, 18, 101. The
network computer 612 sends thè user ID along with user location
and the selected AG 16 to the user's HG 12, 14, 16, 18, 101 via
the packet network 32 through landlines 132. The data are
received by the HG 12, 14, 16, 18, 101 by the cellular telephone
system 221 through landlines 130. The cellular telephone system
221 updates the home user database 31 to show the user 30 as
roaming, the user's location, and the AG 16. The network
computer 612 then sends a message to the CTS 101, 102 to
transmit to the user 30 call setup data, which might include
21 0~ 738
.
call setup, transmit and receive channels, transmit and receive
codes if CDMA is used, and other information. The CTS 101, 102
transmits this data to the user 30. The user 30 receives this
data and goes to ready.
CAI.L INITIATION BY A USER 30 (AN INBOUND CAI~L):
Referring to Fig. 5, the process to initiate a call
from a user 30 while roaming in an SSA 24 is as follows:
CA~L REQUEST (IN~OUND):
To make a call request, the user 30 dials the
destination telephone 107, 108, 50 telephone number by the use
of the keypad of the Cellular Telephone 503 (See Fig. lOA Step
C, Fig. lOC Step Cl). The number is passed to the Satellite
Control Unit 530 and into Request/ACK generator 533. The user
number 532 is added to the signal and passed to encoder 524 and
processed into a data stream which is applied to modem 526. Two
methods are available for the user 30 to access the satellite
22. Method 1: An FDM-FM or other modulation using contention
multiple access, operating on a hailing channel, may be used to
signal the satellite 22. Method 2: A special identifying CDMA
code is placed in the User Request Unit 535. The satellite 22
simply repeats to the ground the signals it receives, so the
method makes no difference to the satellite 22. The resulting
modulated signal is then applied to the Satellite RF Converter
527 and routed to the satellite antenna 522 and transmitted to
the satellite(s) 22 within range. The satellite(s) 22 within
range repeat the signal to the ground.
. ~
~ 2lO~738
AG 16, 101 ACC~PTANCE OF CAL~S FROM USER 30 (INBOUND):
In the process of accepting calls at the AG 101, 16,
the signals are received by antenna 203 and applied to the
Satellite RF Unit 238 as shown in Fig. 6. The signals are
processed, applied to modem 237, thence to decoder 234 and the
CTIU 230. The CTIU 230 sends the user ID and Call Destination
to the gateway controller 260. The gateway controller 260
checks the information being fed to it by the NCG 28 to see if
there are satellite 22 resources, and if there are resources,
the channels that are available. If no satellite resources are
available, the gateway controller 260 sends a message to CTIU
230 to signal the user 30 to retry (method described below). If
satellite 22 resources are available, the user ID is checked
against the stored ID information held in the database ~or
acceptability of the user 30 (Fig. 10D, D3). If no access is
detected, the call request is terminated (Fig. 10C, C2; Fig.
10D, D5). If access is allowed (D5), the gateway controller 260
checks the availability of the gateway 12, 14, 16, 18 resources.
If gateway 12, 14, 16, 18 resources are not available, the
gateway controller 260 sends a request to the NCG 28 to check
for other available gateways 12, 14, 16, 18. If no other
gateways 12, 14, 16, 18 are available, network computer 612
sends a message to the AG 16, 101 to signal the user 30 to retry
(method described below). If another gateway 12, 14, 16, 18 is
available, network computer 612 selects this gateway 12, 14, 16,
18 as the new AG because the current AG 16, 101 is not available
or because of a system choice~ The network computer 612 sends a
message to the current AG 16, 101 that a new AG 12, 14, 18 has
been selected. The current AG 16, 101 removes user 30 from
database 27. The network computer 612 sends user ID and user
location to the new AG 12, 14, 18 and to the user's HG 12, 14,
16, 18 via the packet network 32 through landlines 132. The AG
12, 14, 18 receives the information and updates its roamer
database 27 and the HG 12, 14, 16, 18 receives the information
and updates its home user database 31.
2 ~ ~ ~ 7':~ ~
INBOUND CAI-~ S~:TUP PROCESS/AG ACCEPTANC~3:
If the current AG 16, 101 is available or a new AG 12,
14, 18 was selected, the gateway controller 260 sends the call
information to the user by the same method as call setup as
described in the request for SSA 24 roaming. The user 30
receives call information, sets transmit and receive
frequencies, sets transmit and receive codes if CDMA is being
used, and goes to stand-by. The cellular telephone interface
unit 230 at the AG 16, 101 processes the call and applies the
desired destination number to the cellular telephone system
w/switch 221. The CTIU 230 at the AG 16, 101 generates ACK
codes for the call request processor 235 and destination code
signals for the cellular telephone system with its switch 221.
Referring first to the ACK codes, the call request processor 235
signals the ACK generator 236 to signal the user 30 that it is
ready to place the call. This ACK signal is applied to encoder
232 and modem 237, and passed to satellite RF unit(s) 238.
After processing, the signal is applied to antenna 203 for
transmitting to the satel ite 22. Referring to Fig. 9, the A~K
signal is transmitted over link 34D or link 36B'
depending on whether the gateway is the home gateway 12 or a
remote gateway 14,16,18. The satellite 22 relays the signal
over link 36A to the user 30.
Referring to Fig. 5, the signal is received by the user
satellite telephone 501 by its antenna 522 and applied to the
user's satellite RF converter 527. The resulting signal is
passed to modem S26 for demodulation then decoded by decoder
525. The signal is sent to request/ACK generator 533. ~he user
30 and the gateway 16, 101 now have a full duplex link for
passing two-way communications traffic.
Referring now to the destination signals sent to the
cellular telephone switch 221, in its normal fashion the
cellular telephone system w/switch 221, as shown in Fig. 4, via
the terrestrial system lines 120, 121, connects to the desired
call destination 107, 108, 50 via the telephone central office
106. Once the call destination 107, 108, 50 answers the call,
full duplex operation begins. The CTIU 230 at the AG 16, 101
sends a message to the NCG 28 to update database 20 to show call
in progress by formatting a message and sending it to the CTS
221 which sends the message to the NCG 28. The data are
received by the NCG 28 by the cellular telephone system 223
through landlines 132 which send the data to the CTIU 230. The
CTIU 230 routes the message to the network computer 612 which
updates network database 20 to show that the user 30 has a call
in progress. The CTIU 230 at the AG 16, 101 sends the user ID
along with ~call in progress" to the user's HG 12, 14, 16, 18,
101 via the packet network 32 through landlines 131. The data
are received by the HG 12, 14, 16, 18, 101 by the cellular
telephone system 221 through landlines 130. The cellular
telephone system 221 updates the home user database 31 to show
the user 30 as having a call in progress. The Handoff Processor
250 at the AG 16, 101 is updated with the information regarding
this duplex call.
INBOUND CALL ACCEPTANCE RFTRY NOTICE (CALL NOT AC~ v):
If the call is not accepted (Fig. 10C, Steps C1, C2),
the gateway controller 260 generates codes indicating NOT OK -
RETRY, formats a signal to the user 30 to show that the call
must be retried, and formats a message and sends it to the CTIU
230, which passes the data to encoder 232. The encoded signal
is applied to modem 237 for modulation, applied to Satellite RF
Unit 238 and, after processing there, applied to antenna 203 for
transmitting to the satellite 22. Referring to Fig. 9, the NOT
OK - RETRY signal is transmitted over link 34D or link 36B'
depending on whether the gateway is the home gateway 12 or a
remote gateway 14,16,18. The satellite 22 relays the signal
over link 36A to the user 30.
Referring to Fig. 5, the retry signal is received by
the user's satellite antenna 522 and passed to the user's
Satellite RF Unit 527. The resulting datastream is demodu~ated
by modem 526 and passed to decoder 525. The decoded retry
signal is applied to Retry Generator 534. When, after a
29
~ A
~ q~ ~,7~;
prescribed time delay, the comparator in Retry Generator 534
shows positive, it signals the call request generator 533 to
retry. A counter limits the number of retries.
INBOUND CALL DUPLEX PROC~SS:
Reference is made to Figs. 4 and 9 for signal routing
and satellite operation, to Fig. 5 for user equipment operation,
and to Fig. 6 for gateway operation.
USER TO CAhL DESTINATION DIREC~ION:
Referring to Fig. 5 to consider the user's end of a
duplex call, user 30 communicates to the call destination 107,
108, 50 by activating Cellular Telephone 503 which passes
digital voice or data to encoder 524, which encodes the signal
into a datastream, which is passed to modem 526. Modem 526
modulates the signal and passes it to Satellite ~F Converter 527
for transmission to the satellite 22 by the antenna 522.
This signal from user 30 is transmitted via link 34A
in Fig. 9 to satellite 22. The signal is received by the
communications uplink RF receiver 302, then applied to the SCT
306, which translates the frequency of the signal, and applies
it to the communications downlink RF transmitter 303, which
amplifies and transmits the signal to the ground by an antenna.
The satellite 22 transmits the signal via link 36B or 36D
depending on the gateway 12, 14, 16, 18 selected in the call
setup process.
Referring to Fig. 6, the signals are received by the
MSA/RSA equipment 101 by antenna 203 and applied to the
satellite RF unit(s) 238. After processing, the signal is
applied to modem 237 and thence to decoder 234 if necessary.
(If the user equipment generates data that conform to industry
standards, the decoding step may be bypassed.) After decoding,
the signal is applied to the cellular telephone interface unit
230 and thence to the Cellular Telephone System w/switch 221.
3S The system then applies the signal to the terrestrial interface
7 ~ ~ ~s
120 via the telephone central office la6 and thence to the call
destination device 107, 108, 50 (Figs. 2 and 4).
CALL DESTINATION 107, 108, 50 TO USER 30 DIRECTION:
In a similar manner, the signals from the call
destination 107, 108, 50 are processed. Referring to Figs. 2
and 4, the call destination user 107, 108, 50 activates his
Telephone Device 107, 108 which passes his voice or data over
landlines 123, 124 to the Telephone Central Office (TCO) 106.
According to the invention, these signals are routed to the
selected Terrestrial Cellular Telephone System 101, 102 by
landlines 120, 121. The landline system is not bypassed.
Referring to Fig. 6, the exemplary Cellular Telephone System 221
routes the signals to the Cellular Telephone Interface Unit 230
where the signals are processed and fed to encoder 232. After
encoding, the signals are applied to modem 237 for modulation
and sent to the Satellite RF Unit 238. The resulting RF signal
is sent to the antenna 203 for transmission to the Satellite
301, 302, 22.
This signal from the gateway 12, 14, 16 18 is
transmitted to satellite 22 via link 36B' or 34D (Fig. 9),
depending on the gateway selected in the call setup process.
The signal is received by the communications uplink RF receiver
302, which applies the signal to the SCT 306, which translates
the frequency of the signal and applies the signal to the
communications downlink RF transmitter 303, which amplifies and
transmits the signal to the ground by an antenna. The satellite
22 transmits the signal via link 36A to the user 30.
Referring to Fig. 5, the user 30 receives
communications in the following manner: the signals are
received by the antenna 522 and sent to Satellite RF converter
527, then passed to modem 526. The demodulated baseband signals
are then decoded by decoder 525 and sent to the cellular
telephone 503 for further processing into audio or data.
HANDOFF OF INBOUND AND OUTBOUND CALLS:
The handoff of both inbound and outbound calls is
accomplished by similar means. The handoff processor 33 senses
user signal level below a preset level over a prescribed length
of time or a handoff is required given the satellites 22 in view
of the AG 16. Subsequent handoffs are accomplished in the same
manner, with the second satellite 22 taking the place of the
original satellite 22 and a third satellite taking the place of
the new satellite 22, and so on.
The handoff processor 33 signals modem 237 to search
the other satellites 22 in view for the user 30. If the user 30
is not found on the other satellites 22, the handoff processor
33 is reset and after a prescribed length of time the signal
level will be checked to see if the hand-off procedure should
start again. If the user 30 is found on another satellite 22,
the handoff processor 33 checks the input from the RF power
monitor 251 if channel capacity is acceptable. If not
acceptable, the handoff processor 33 picks an accepta~le channel
frequency and new CMDA codes if required. The handoff
processor 33 formats a message containing the new transmit and
receive frequencies (and new codes if required) and sends the
message to modem 237 for modulation. Modem 237 modulates the
message and applies the signal to the Satellite RF Unit 238.
The resulting RF signal is sent to the antenna 203 for
transmission to the original Satellite ~01, 302, 22.
Referring to Fig. 9, the signals are transmitted from
the gateway 12, 14, 16, 18 over link 34D or link 36B~
depending on the gateway selected during the call setup process.
The signals are downlinked to the user 30 via link 36A
Referring to Fig. 5, the user 30 receives
communications in the following manner: the signals are
received by the antenna 522 and sent to Satellite RF converter
527, then passed to modem 526. The demodulated baseband signals
are then decoded by decoder 52S. The resulting signal is sent
to request/ACK generator 533 which shifts the cellular telephone
503 to the proper channel and provides modem 526 with the call
32
"' ~ f~
CDMA codes for reception and goes to ready. The request/ACK
generator 533 sends an ACK to handoff processor 33 at the AG 16
through the satellite 22. The handoff processor 33 receives the
ACK and shifts satellite RF unit 238 to new transmit and receive
frequencies. Handoff processor 33 signals the satellite RF unit
238 to send its transmissions and receptions to the new
satellite 22 and the call continues.
If there was adequate channel capacity on the new
satellite 22 at the original frequencies, handoff processor 33
signals the satellite RF unit 238 to send its transmissions and
receptions to the new satellite 22 and the call continues. The
handoff processor 33 formats a message for the NCG 28 regarding
the new satellite 22 and new frequency assignment if required,
and sends the message to the packet network 32 through landlines
130. The data are received by the NCG 28 by the CTIU 230
through landlines 132. The CTIU 230 routes the message to
network computer 612 which updates network database 20 to show
the new call information.
2 0 CAI-L T~R~TN~TION OF INBOUND AND OUTBOUND CAL~S:
Calls are terminated in the same manner for user 30
initiated calls or caller 107, 108, 50 generated calls (Fig. lOC
to Fig. lOF or Fig. lOG to Fig. lOJ) as follows: Referring to
Fig. 6, the Cellular Telephone System 221 senses an on-hook
condition, from either the user 30 or the call destination 107,
108, 50, and signals the Cellular Telephone Interface Unit
(CTIU) 230 to activate call termination. The CTIU 230 signals
the call termination processor 233 to generate a call
termination signal and route it to the encoder 232. The encoded
signal is then applied to modem 237 for modulation, and this
modulated signal is routed to the Satellite RF Unit 238. The
resulting RF signal is sent to antenna 203 for transmission to
the Satellite 301, 302,22.
This signal from the gateway 12, 14, 16, 18 is
transmitted via link 36B' or 34D (Fig. 9), depending on
the gateway selected in the call setup process, to the satellite
22. The signal is received by the communications uplink RF
receiver 302, which applies the signal to the SCT 306, which
translates the frequency of the signal and applies it to the
communications downlink RF transmitter 303, whish amplifies and
transmits the signal to the ground by an antenna. The satellite
22 transmits the signal via link 36A to the user 30.
Referring to Fig. 5, the user 30 receives
communications in the following manner: the signal is received
by the antenna 522 and sent to the Satellite RF converter 527,
then passed to modem 526 for demodulation. The demodulated
baseband signals are then decoded by decoder 525 and sent to the
cellular telephone 503, which discontinues the call.
The Cellular Telephone System 101, 102 also activates
codes which are transmitted over landlines 130 to the NCG 28.
Referring to Fig. 4, these signals are routed over the network
landlines 130, 131 to the TCO 106 and thence to the NCG 28 by
landline 132. Referring to Fig. 7, these signals are processed
by network computer 612, which updates the network database 20
to show the user not busy. Certain other business data are also
routed to the NCG 28, such as billing information, call time,
rates, or other such information. The gateway controller 260 at
the AG 16 notifies the home gateway (HG) 12, 14, 16, 18, 101,
102, via packet switched network 32, through landlines 130 via
telephone central office 106 or other such network, of the
current status of the user. The data are received by the ~G 12,
14, 16, 18, 101, 102 by the cellular telephone system 221
through landlines 130. The cellular telephone system 221
updates the home user database 31 to show the user 30 as not
busy. The AG 16 resets processors and updates databases.
Referrin~ ~o Fig. 6, the cellular telephone system w/switch 221
then updates the roamer database 27 to show the user not busy.
CALL INITIATION BY A ~T-T-R~ 107, 108, 50 (AN OUTBOUND CALL):
Referring to Fig. 4, the process to initiate a call
from a caller 107, 108, 50 to a user 50 roaming in a service
area is as follows:
34
: h~
' ~3
,,
2105738
CAL~ REQUEST (ouTsouND):
A call request is made when a caller 107, 108, 50 makes
a terrestrial PSTN or other network call to the user's home or
equivalent TCTSA (gateway) 12, 14, 16, 18, 101, 102, rather than
to a nearby uplink, which would bypass the normal terrestrial
structure. The call is routed to the user's HG 12, 14, 16, 18,
101, 102 via the normal terrestrial structure. Referring to
Fig. 4, the caller 107, 108, 50 using a telephone device 107,
108 dials the telephone number of the user equipment 501, 502 by
the use of any means provided by the device 107, 108. The
number is passed via the terrestrial lines or equivalent means
123, 124 to the Telephone Central Office 106 or other central
switching office, and thence via terrestrial lines or equivalent
means 120, 121 to the Cellular Telephone System equipment 101,
102 located at the usér's home gateway 12, 14, 16, 18, 101, 102.
Referring to Fig. 6, the request for access to the user
30 is processed by the Cellular Telephone System w/switch 221,
which interrogates the home user database 31 to determine if the
user 30 is roaming in the SSA 24. If the user 30 is roaming in
the SSA 24 and is not busy, the HG 12, 14, 16, 18, 101, 102
reacts in one of two ways: A) the HG sends an access number to
the caller 107, 108, 50 for the caller to redial, which will
ring at the AG 16; or B) the user number, location, active
gateway (AG) 16, and other user data are retrieved from the
database 31 and passed to the satellite interface equipment 201.
The signal is applied to the ~oute planner 240. The route
planner processes the information, and, using stored satellite
ephemeris and user information, selects the routing of the call
to the AG 16 . The call is routed to the AG 16 through the
normal terrestrial structure.
AG 16 AC~l .ANCE OF CALBS FROM C~T.T.T~.T~ 107, 108, 50 (OUTBOUND):
The gateway controller 260 at the AG 16 receives the
call through landlines 120 or by the caller using the access
number which is received by the CTS 120 at the AG 16 and the CTS
21057~8
120. The gateway controller 260 checks the information being
fed to it by the RF Power Monitor 251 and from the NCG 28 to see
if there are satellite 22 resources, and if there are resources,
the channels that are available.
s If no satellite 22 resources are available, the gateway
controller 260 formats a message to signal caller 107, 108, 50
that the system 10 is busy and to retry, and sends the message
to CTS 221. The cellular telephone system 221 at the AG 16
receives the message and signals the caller 107, 108, 50 that
the system 10 is busy and to retry.
If satellite 22 resources are available, the gateway
controller 260 checks the availability of resources at the AG
16. If resources at the AG 16 are not available, the gateway
controller 260 sends a request to the NCG 28 to check for other
gateways 12, 14, 16, 18. If no other gateways are available,
the network computer 612 formats a message to signal caller 107,
108, 50 that the system 10 is busy and to retry, and sends the
message to CTIU 230. The CTIU 230 sends the message to the AG
101, 102, 16 via the packet network 32 through landlines 132.
The cellular telephone system 221 at the HG 12, 14, 16, 18, 101,
102 receives the message through landlines 130 and signals the
caller 107, 108, 50 that the system 10 is busy and to retry. If
another gateway 12, 14, 16, 18 is available, the network
computer 612 selects this gateway 12, 14, 16, 18 as the new AG,
because the current AG 16 is not available, or because of a
system choice. The network computer 612 sends a message to the
current AG 16, 101 that a new~AG 12, 14, 18 has been selected.
The current AG 16, 101 removes user 30 from database 27. The
network computer 612 sends user ID and user location to the new
AG 12, 14, 18, and to the user~s HG 12, 14, 16, 18, 101, 102 via
the packet network 32 through landlines 132. The AG 16 receives
the information and updates its roamer database 27 and the HG
12, 14, 16, 18, 101, 102 receives the information and updates
i~s home user data~ase 31.
The gateway controller 260 at the AG 12, 14, 16, 18
formats a hailing message for the user 30 and sends the message
7 ~ ~ ~
to the CTIU 230, which routes the message to the encoder 232.
The message is processed by modem 237 and satellite RF unit 238,
and transmitted to the satellite 22 through antenna 205. The
satellite 22 relays the message to the user 30. If no response,
the AG 12, 14, 16, 18 checks all satellites 22 in view. If user
30 is not found after a prescribed length of time, the gateway
controller 260 formats a message for the caller 107, 108, 50
that the user 30 is not available, and sends the message to the
CTS 221. The cellular telephone system 221 at the AG 12, 14,
16, 18 signals the caller 107, 108, 50 that the user 30 is not
available at this time. If the user 30 receives the hailing
message, referring to Fig. 5, the user 30 receives
communications in the following manner: The signals are
received by the antenna 522 and sent to the Satellite RF
converter 527, then passed to modem 526 for demodulation. The
demodulated baseband signals are then decoded by 525. The
resulting signal is sent to request/ACK generator 533, which
formats an ACK message and sends the ACK to encoder 524. After
encoding, the ACK is passed to modem 526. Modem 526 modulates
the signal and passes it to the Satellite RF Converter 527 for
transmission to the satellite 22 by the antenna 522.
Referring to Fig. 9, the uplink signal is transmitted
to the satellite 22 from the user 30 over link 34A and
relayed to the AG 12, 14, 16, 18. The signals are downlinked
via link 36D or 36B depending upon whether the AG 12, 14,
16, 18 is the user's home gateway or the user 30 is roaming.
Referring to Fig. 6, the signals are received by the
gateway equipment 101 by antenna 203 and applied to the
satellite RF unit(s) 238. After processing, the signal is
applied to modem 237 and thence to decoder 234 if necessary.
(If the user equipment generates data that conforms to industry
standards, the decoding step may be bypassed.) After decoding,
the signal is applied to the CTIU 230, which recognizes the ACK
and sends the ACK to the gateway controller 260.
OUTBOUND CAL~ S~TUP, AG 16 ACCEPTA~CE:
If the current AG 16 is available or a new AG 12, 14,
18 was selected, the gateway controller 260 sends the identity
of the current satellite 22 being used, transmit and receive
frequencies, and transmit and receive codes if CDMA is being
used to the user 30 by the same method as call setup as
described in the request for SSA 24 roaming. The user 30
receives call information, sets transmit and receive
frequencies, sets transmit and receive codes if CDMA is being
used, and goes to stand-by.
The AG 12, 14, 16, 18 signals the user 30 on assigned
frequency and codes if required. The CTIU 230 at the AG 12, 14,
16, 18 generates ACK codes for the call request processor 235.
The call request processor 235 signals the ACK generator 236 to
signal the user 30 that the user 30 is being called. This ACK
signal is applied to the encoder 232 and the modem 237 and
passed to the satellite RF unit(s) 238, and after processing,
applied to the antenna 203 for transmitting to the satellite 22.
Referring to Fig. 9, the ACK signal is transmitted over link
34D or link 36B~ depending on whether the gateway is the
home gateway 12 or a remote gateway 14,16,18. The satellite 22
receives the signal and relays the signal over link 36A to
the user 30.
Referring to Fig. 5, for reception and processing of
outbound calls at the user 30, the user~s antenna 522 receives
the signal and routes it to the Satellite RF converter 527,
which routes the signal to modem 526. The resulting datastream
is applied to decoder 525. After decoding, the data are sent to
the request/ACK generator 533. Codes are generated and sent to
the Cellular Telephone 503 to ring the user 30. The Cellular
Telephone 503 signals the ACK generator 533 to send signaling
codes to the AG 12, 14, 16, 18 via the encoder 524. The ACK
signal is passed from the encoder 524 to the modem 526 and
thence to the Satellite RF converter 527. The resulting ACK
signal is transmitted to the Satellite 301, 302, 22 via the
38
~ .
'~ 210~738
antenna 522. The user wireless satellite telephone 501 then
shifts frequency to the channel selected by the AG 12, 14, 16,
18, and loads, if necessary, the CDMA code for the call into the
modem 526. The user then waits for duplex operation to begin.
The ACK signal is received by satellite 301, 302, 22
and transmitted to the earth. The signal is received at the
gateway equipment 101, 102 by antenna 203, 204 and applied to
the satellite RF unit(s) 238. After down conversion to
baseband, the signals are demodulated by the modem 237 and
routed to the decoder 234. The decoded baseband signals are
then applied to the cellular telephone interface unit 230. The
cellular telephone interface unit 230 processes the information.
The cellular telephone interface unit 230 then applies
the voice and data signal stream to the encoder 232 or directly
to the modem 237, depending on the incoming signal structure,
and thence to the assigned channel of the satellite RF unit(s)
238, thence to the antenna 203, 204. Duplex operation can now
begin. The CTIU 230 at the AG 12, 14, 16, 18 sends a message to
the NCG 28 to update database 20 to show call in progress, by
formatting a message and sending it to the CTS 221, which sends
the message to the NCG 28. The data are received by the NCG 28
by the cellular telephone system 223 through landlines 132,
which send the data to the CTIU 230. The CTIU routes the
message to the network computer 612, which updates the network
database 20 to show that the user 30 has a call in progress.
The cellular telephone system 221 updates the home user database
31 to show the user as roaming, the user's location, and the AG
12, 14, 16, 18. The AG 12, 14, 16, 18 sends the user ID along
with call in progress to the user's HG 101, 102,12, 14, 16, 18
via the packet network 32 through landlines 132. The data are
received by the HG 101, 102,12, 14, 16, 18 by the cellular
telephone system 221 through landlines 130. The cellular
telephone system 221 updates the home user database 31 to show
the user 30 as having a call in progress. The Handoff Processor
33 at the AG 12, 14, 16, 18 is updated with the information
regarding this duplex call.
39
.
~ 21US738
OUTBOUND CA~L DUPLEX PROCESS:
The outbound call duplex process is identical to that
of a user 30 initiated call described above.
~IANDOFF OF OUTBOUND CAI,I.S:
The handoff processes are identical to that of a user
30 initiated call described above.
1 0 CALL TERMINATION ( OUTBOUND CAI~L ):
The call termination processes are identical to that of
a user 30 initiated call described above.
NO.lrlCATION TO DIS~'OI.. lNU~ ROAMING BY USER 3 0:
As in the notification to the system 10 of the intent
to commence roaming, there are two methods by which the user 30
can notify his intent to discontinue roaming. The user 30 has
two options: he may notify Network Control (NC) 25 of his
intention while in the SSA 24 and out of range of a TCTSA 12,
14, 16, 18 and have his request processed via a satellite 22
relay to the AG 16, or he may make his request via a
participating TCTSA 12, 14, 16, 18. These two cases are now
explained (See Figs. lOA, lOK, lOL.)
Rl~QU13ST TO DI8C;GI.,lNUI5 ROA~ING BY USER 30 IN 8SA 24:
The user 30 notifies the system 10 by way of the
satellite 22 that he desires to be deleted from the Database of
Roamers 27 in the SSA 24. Referring to Fig. 5, the user 30
initiates a termination request by manually or automatically
activating the User Request Unit 535. A signal is passed to the
Request/ACK Generator 533. This generates a termination
request, which is passed to the encoder 524 and modulated by
modem 526. The resulting signal is routed to the Satellite RF
Converter 527 and then to the antenna 522 for transmission to
the satellite 22. The signal is transmitted to the satellite(s)
'' - -
21~S738
' . .
22 in view via link "A" and the satellite~s) 22 transmit the
signal to the AG 16 via link ~'B~.
Referring to Fig. 6, the downlink signal is received at
the AG 16 satellite antenna 203 and applied to the Satellite RF
Unit(s) 238. The resulting baseband signal is demodulated in
modem 237, sent to decoder 234, and thence to the CTIU 230. The
resulting data are sent to the gateway controller 260, which
instructs the database 20 to delete the user 30 from the list of
SSA Roaming Users 27. The gateway controller 260 sends the
termination request to the NCG 28 by formatting a message which
contains the request and user ID and routes the data to the
packet switch network 32 through landlines 132. The data are
received by the NCG 28 through landlines 132. The NCG 28 then
deletes the user 30 from the roamer database 27.
The gateway controller 260 at the AG 16 sends the user
ID and termination request to the user's HG (e.g. 101) via the
packet network 32 through landlines 132. The data are received
by the HG 101 by the cellular telephone system 221 through
landlines 130. The cellular telephone system 221 updates the
home user database 31 to show the user 30 as not roaming in the
SSA 24.
REQUEST TO DISCO... 'NU~ ROAMING BY ~SER 30 IN A TCTSA 12, 14, 16,
18: Referring to Fig. 1 and Fig. lOL, the user 30 re-enters
a remote TCTSA (e.g. 12) or his home TCTSA (e.g. 14) and either
automatically or manually notifies the system 10 by way of the
TCTSA 12,14 that he desires tQ be deleted from the network
database 20 of active users in the SSA 24. Referring to Fig. 5,
the user equipment 501 initiates a termination request by
manually or automatically activating the User Request Unit 535.
A signal is passed to the Request/ACK Generator 533. This
generates a termination request, which is passed to the Cellular
Telephone 503. The resulting signal is routed to the antenna
505 for transmission to the TCTSA 12,14. The signal is received
by the TCTSA 12,14 and relayed to the NCG 28 via the packet
network 32 through landlines 130, 131.
41
~ 210~738
Referring to Fig. 7, the signal is received via
landline 132 at the NCG 28, which instructs the network database
20 to delete the user 30 from the list of SSA Roaming Users.
The network computer 612 sends the termination request to the AG
16 by formatting a message which contains the request and user
ID, and sending it to the cellular telephone interface unit
(CTIU) 230, which routes the data to the cellular telephone
system 223 and to the packet switch network 32 through landlines
132. The data are received by the AG 16 by the cellular
telephone system 222 through landlines 131. The cellular
telephone system 222 then deletes the user 30 from the roamer
database 27.
The network computer 612 sends the user ID and
termination request to the user's HG (e.g. 101) via the packet
network 32 through landlines 132. The data are received by the
HG 101 by the cellular telephone system 221 through landlines
130. The cellular telephone system 221 updates the home user
database 31 to show the user 30 as not roaming in the SSA 24.
The invention has now been explained with reference to
specific embodiments. Other embodiments will be apparent to
those of ordinary skill in this art in light of this disclosure.
It is therefore not intended that this invention be limited,
except as indicated by the appended claims.
What is claimed is:
42
