Note: Descriptions are shown in the official language in which they were submitted.
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HOME LOCATION REGISTER FOR MANUAL VISITORS
IN A TELECOMMUNICATION ~Y~-lLI
R~CK~OUND OF THE lNV~N-llON
Technic~l F;el~ of the Invent;on
This invention relates to cellular telephone networks,
and more particularly, to foreign network registration of
roaming cellular telephones.
Descr~pt;on of Related Art
In existing cellular telecommunication systems, when
a subscriber leaves a home network and enters a visited
network that does not have automatic roamer signaling with
the subscriber's home network, that subscriber cannot
originate calls until the subscriber is m~n~ ly registered.
With or without an operator's manual intervention, the
roaming subscriber must be connected as a manual visitor
with a validation against a clearinghouse or validation of
a credit card. In addition, within the visited network,
every time the subscriber roams from one mobile switching
center (MSC) to another visited MSC, the subscriber must go
through the same procedure to re-register as a manual
roamer.
In some networks, the manual registration procedure
must be repeated every time the subscriber originates a
call. Additionally, in order to minimize fraudulent calls,
no call delivery is provided to manual subscribers because
subscriber records are kept only for the duration of each
call.
SU~$~RY OF THE IhvhN-llON
In a cellular telecommunication system in which mobile
subscribers may roam from a home network to a visited
network having an automatic roaming agreement with the home
network, and to a visited network without an automatic
roaming agreement with the home network, the present
invention provides visiting subscribers to a visited network
without an automatic roaming agreement with the subscriber's
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home network with the same registration capabilities as
visiting subscribers to a visited network having an
automatic roaming agreement with the home network.
The system of the present invention includes means ~ _
S within each visited network for identifying the home network
of each visiting subscriber and means within each visited
network for determining whether or not the home network of
each visiting subscriber has an automatic roaming agreement
with the visited network. The system also includes means
within each visited network for classifying as an automatic
visitor each visiting subscriber whose home network has an
automatic roaming agreement with the visited network, and
means within each visited network for classifying as a
manual visitor each visiting subscriber whose home network
does not have an automatic roaming agreement with the
visited network. Further, the system includes means within
each visited network for maintaining a database of
information on manual visitors, and means for storing in the
database, registration information regarding each manual
visitor. The storing means stores the registration
information upon each manual visitor~s initial call attempt
in the visited network. Finally, the system includes means
for accessing from each of the visited network's mobile
switching centers, the database of registration information
upon each call to be delivered to the manual visitor or each
m~ntl~l visitor's subsequent call attempts within the visited
network.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be better understood and its
numerous objects and advantages will become more apparent
to those skilled in the art by reference to the following
drawing, in conjunction with the accompanying specification,
in which:
FIG. 1 (Prior Art) is an illustrative representation
of a conventional cellular radio communications network of
the type to which the present invention generally pertains;
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FIG. 2 (Prior Art) is an illustrative representation
of three cellular radio communications networks of the type
illustrated in FIG.l, with a first network being a
subscriber's home network, a second network being a visited
network having an automatic roaming agreement with the home
network, and a third network being a visited network that
does not have an automatic roaming agreement with the home
network;
FIG. 3 is a signaling diagram illustrating the flow of
messages between an old serving MSC, a HLR, and a new
serving MSC during the registration and validation process
as a mobile subscriber roams from the old serving MSC to the
new serving MSC;
FIG. 4 is an illustrative representation of a visited
cellular radio communications network that does not have an
automatic roaming agreement with the home network and has
been implemented with a manual home location register of the
present invention; and
FIG. 5 is a signaling diagram illustrating the flow of
messages between an originating MSC, a H~R, and a serving
MSC during call delivery to a mobile subscriber that is
outside the serving area of the MSC where the call
orlglnates .
2 5 DETATT.T~n DESCRIPTION OF EMBODIMENTS
Referring first to FIG. 1, there is illustrated a
conventional cellular radio communications system of the
type to which the present invention generally pertains. In
FIG. 1, an arbitrary geographic area may be divided into a
plurality of contiguous radio coverage areas, or cells Cl-
C10. While the system of FIG. 1 is illustratively shown to
include only 10 cells, it should be clearly understood that
in practice, the number of cells will be much larger.
Associated with and located within each of the cells
Cl-C10 is a base station designated as a corresponding one
of a plurality of base stations Bl-B10. Each one of the
base stations Bl-B10 includes a transmitter, a receiver, and
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base station controller as are well known in the art. In
FIG. 1, the base stations Bl-B10 are illustratively located ~ s
at the center of each of the cells Cl-C10, respectively, and
are e~uipped with omni-directional antennas. However, in
other configurations of a cellular radio system, the base
stations Bl-B10 may be located near the periphery, or
otherwise away from the centers of the cells Cl-C10 and may
illuminate the cells Cl-C10 with radio signals either omni- ;
directionally or directionally. Therefore, the
representation of the cellular radio system of FIG. 1 is for
purposes of illustration only and is not intended as a
limitation on the possible implementa-tions of the cellular
radio system within which the method and system of the
present invention may be implemented.
15With continuing reference to FIG. 1, a plurality of
mobile stations Ml-M10 may be found within the cells Cl-C10.
Again, only 10 mobile stations are shown in FIG. 1 but it
should be understood that the actual number of mobile
stations will be much larger in practice and will invariably
greatly exceed the number of base stations. Moreover, while
none of the mobile stations Ml-M10 may be found in some of
the cells Cl-C10, the presence or absence of the mobile
stations Ml-M10 in any particular one of the cells Cl-C10
should be understood to depend, in practice on the
individual desires of the subscribers associated with mobile
stations Ml-M10 who may roam from one location in the cell
to another or from one cell to an adjacent cell or
neighboring cell, and even from one cellular radio exchange
served by a mobile switching center to another such
exchange.
Each of the mobile stations Ml-M10 is capable of
initiating or receiving a telephone call through one or more
of the base stations Bl-B10 and an associated mobile
switching center (MSC). The MSC is connected by
communication links, e.g., cables, to each of the
illustrative base stations Bl-B10 and to a fixed public
switched telephone network (PSTN) (not shown) or a similar
-
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fixed network which may include an integrated system digital
network (ISDN) facility.
Within the geographic coverage area served by a
specific cellular communication network, there may be one
MSC, or there may be several MSCs which are interconnected
and connected to the PSTN or ISDN. The network may also
include a home location register (HLR) which maintains a
database of subscriber information. The relevant
connections between the MSCs, and between the MSCs and the
HLR, PSTN, or ISDN, are not completely shown in FIG. 1 but
are well known to those of ordinary skill in the art.
There are generally two types of mobile subscribers,
automatic subscribers and manual subscribers. An automatic
subscriber is one for which the network in which the
subscriber is located automatically updates the location and
registration of the subscriber as the subscriber moves from
one MSC to another within the network. This automatic
location and registration eliminates the requirement for the
subscriber to register with the network whenever the
subscriber moves from one MSC to another within the network.
Subscribers within their home network are automatic
subscribers. Additionally, operators of different networks
having signaling links between them may enter into automatic
roaming agreements that provide their respective subscribers
with automatic subscriber status when operating within each
other's networks, thereby providing subscribers with the
capability to roam between each other's networks without
loss of services.
Each network may include a home location register (HLR)
which stores subscriber information in a database and
enables automatic updating of location and registration
information for home subscribers and automatic visitors from
other networks having automatic roaming agreements with the
home network. When a subscriber enters a visited network
that has an agreement with the subscriber's home network,
and turns on his phone, the interface between the phone and
the network recognizes the subscriber as being from a
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network having an automatic roaming agreement. The visited
network makes a record of the subscriber in the MSC where
the visiting subscriber is located and notifies the home
network to update the location of the subscriber in the home
network's database (HLR). Thereafter, calls directed to the
subscriber in the home network are automatically forwarded
to the visited network.
FIG. 2 is an illustrative representation of three
cellular radio communications networks with a first network
11 being a subscriber's home network, a second network 12
being a visited network having an automatic roaming
agreement with the home network, and a third network 13
being a visited network that does not have an automatic
roaming agreement with the home network. While the networks
of FIG. 2 are illustratively shown to each include three
MSCs interconnected by signaling links 14, it should be
clearly understood that in practice, the number of MSCs may
vary and still fall within the scope and spirit of the
present invention.
The home network 11 provides automatic subscriber
status to all mobile subscribers subscribing to its service.
Thus, a home subscriber may roam freely from MSC1 to MSC2
and MSC3 within the home network 11 without having to re-
register with the home network. A signaling link 15 between
the home network 11 and the visited network 12 indicates
that there is an automatic roaming agreement between the
home network 11 and the visited network 12 for the visited
network to treat visiting subscribers from the home network
as automatic subscribers. Thus, roaming subscribers from
the home network 11 may roam freely between MSCs 1, 2, and
3 in the visited network 12 having the agreement.
A metropolitan network is any group of automatic
roaming cooperating MSCs sharing the cellular coverage of
a certain geographic area, typically a city. A function
identified as Local Access to Automatic Visitors allows
incoming calls through a roamer port to be delivered to
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automatic visitors within the roamer port area in the
metropolitan network.
Upon reception of an incoming call through a local
access roamer port, a second dial tone is generated toward
the calling subscriber. The calling subscriber then dials
the called mobile subscriber's 10-digit directory number
(including area code), and if the call is intended for an
automatic visitor, the home syqtem is interroyated to
provide the roaming routing number corresponding to the
subscriber's location. If the received roaming routing
number belongs to the corresponding roamer area in the
metropolitan network, the call is routed to the appropriate
MSC within the metropolitan network. Otherwise, the call
is rerouted according to the exchange data, e.g. the calling
party is informed that the mobile subscriber cannot be
reached.
A manual subscriber is one for which the network in
which the subscriber is operating does not automatically
update the location and registration of the subscriber as
the subscriber roams from one MSC to another within the
network. Such a situation arises when, as illustrated in
FIG. 2, a subscriber from the home network 11 travels to the
visited network 13 which does not have an automatic roaming
agreement with the home network to provide automatic
subscriber service. Manual subscribers must re-register
with the visited network 13 whenever they roam from one MSC
to another within the visited network. In addition, to help
prevent fraud, many visited networks re~uire such manual
visitors to re-register before making each call, even if
they have not roamed from a MSC in which they previously
registered. Such per-call registration may be handled by
a human operator or a mechanical operator with, for example,
recorded voice instructions. Registration may include
validation of credit card numbers or other means of making
payment for cellular telephone services by accessing a
database of bad credit card numbers.
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Clearinghouse roamer validation is an on-line service
used to prevent fraudulent m~nll~l visitors from being served
by telecommunication systems. Clearing-house roamer
validation is provided by interacting between the MSC and
an external database administered by the clearinghouse. The
access to the clearinghouse can be made at the first call
attempt to or from a manual roaming visitor and may be
repeated at each subsequent call attempt. The clearinghouse
validation check is performed in parallel with call setup.
At call access, a visiting mobile station transmits its
mobile identification number (MIN) and electronic serial
number (ESN). The MSC transmits the MIN and ESN to the
clearinghouse via an I/O device which may be, for example,
a V24 port. The clearing-house checks the mobile station's
MIN and ESN against a database of fraudulent MINs and ESNs.
If the clearinghouse validates the visitor, no information
is sent back to the MSC. If the clearinghouse determines
that the visitor is not to be allowed service, the visitor's
ESN is sent back to the MSC. The ESN is entered into the
MSC's serial number barring list, and the visitor~s service
is disconnected. If the visitor has a call in progress, the
call is immediately terminated.
It is possible for new visitors to arrive and initiate
calls at a greater rate than the clearing-house can accept
for a prolonged period of time. When such an overload
situation occurs, an alarm is issued when a buffer holding
visitor data waiting to be validated is full. The alarm is
cancelled when the number of available records in the buffer
falls below a predetermined alarm cease level. The alarm
levels are specified in terms of percent of the buffer by
means of application dependent parameters. Application
dependent parameters may include a parameter that indicates
whether the clearinghouse check is to be performed for
unidentified (home exchange unknown) subscribers. An
additional parameter indicates whether the clearinghouse
check is to be performed only for a subscriber's first call
access or for every call access.
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FIG. 3 is a signaling diagram illustrating the flow of
mes~ages between an old serving MSC 21, a H~R 22, and a new
serving MSC 23 during the registration and validation
process as a mobile subscriber roams from the old serving
MSC 21 to the new serving MSC 23. After determining at step
41 that a roaming mobile is now within its service area, the
new serving MSC 23 sends a REGNOT (Registration
Notification) INVOKE message 24 to the new serving VLR 25.
The new serving MSC 23 may detect the mobile subscriber~s
presence through autonomous registration, call origination,
or service order.
If the mobile subscriber had previously registered with
an MSC within the network served by the new serving VLR 25,
the VLR 25 may take no further action other than to record
the identity of the MSC 23 currently serving the mobile.~
If the mobile is unknown to the new serving VLR 25, or
if the information requested by the new serving MSC 23 is
not available at the VLR, the new serving VLR 25 sends a
REGNOT INVOKE message 26 at step 42 to the HLR 22 associated
with the mobile subscriber. This association is made
through the mobile identi~ication number (MIN) reported by
the subscriber's mobile station. A REGNOT response message
27 is sent from the HLR 22 to the new serving VLR 25. An
additional REGNOT response message 28 is sent from the new
serving VLR 25 to the new serving MSC 23, and may be
contingent upon the response 27 received from the HLR 22.
If the mobile subscriber was previously registered in
an old serving VLR 29 and MSC 21, the HLR 22 sends at step
43 a REGCANC (Registration Cancellation) INVOKE message 31
to the old serving VLR 29. The old serving VLR 29, upon
receipt of the cancellation message 31, removes all record
of the mobile subscriber from its memory, and a REGCANC
response message 32 is returned to the HLR 22. The REGCANC
INVOKE message 31 may be sent by the HLR 22 at any time
after it receives the REGNOT INVOKE message 26.
At step 44, the old serving VLR 29 sends a REGCANC
INVOKE message 33 to the old serving MSC 21. The old
_ _ _ ,, . _ _ . . . . ... . . . .
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serving MSC 21, upon receipt of the cancellation message 33,
removes all record of the mobile station from its memory,
and returns a REGCANC response message 34 to the old serving
VLR 29.
At step 45, the new serving VLR 25 creates an entry for
the mobile in its internal data structures and may send a
QUALREQ (Qualification Request) INVOKE message 35 to the HLR
22 in order to authenticate the mobile subscriber and
determine validation requirements as indicated in a QUALREQ
response message 36. If required, the new serving VLR 25
may then send a PROFREQ (Service Profile Request) INVOKE
message 37 to the HLR 22 at step 46 in order to obtain the
service profile for the roaming mobile subscriber, as
indicated in a PROFREQ response message 38.
In the example illustrated in FIG. 3, the Registration
Notification 26, Qualification Request 35, and Service
Profile Request 37 are shown as separate primitive
transactions for clarity. Options are provided in the IS-41
message set to group these primitives into a single
transaction if desired.
Delivery of calls to manual roamers also poses an
problem in existing telecommunications networks. If a
subscriber roams from the home network to the visited
network without agreement, the subscriber must register with
the visited network before he can initiate or receive
telephone calls. Otherwise, the subscriber will get a "no
service" message on his mobile station. Once the subscriber
has registered with the visited network, the operator of the
visited network informs the home network that the subscriber
is now located in the visited network and provides an access
telephone number for the visited network. The access number
is often referred to as a pilot number or, preferably, a
roamer port number (RPN).
Subsequently, if someone calls the subscriber at the
subscriber's telephone number in his home network, the
calling party will hear a message that the subscriber is now
in the visited network, and providing the RPN. If the
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cal].ing party dials the RPN, he obtains a dial tone for the
visited network. The calling party then dials the
subscriber's regular 10-digit directory number (including
the 3-digit area code) in order to complete the call.
An additional problem arises most often in metropolitan
areas when the visited network without agreement comprises
more than one MSC. There can be only one RPN for the
visited network because the RPN is connected through the
Public Switched Telephone Network (PSTN) to the home
network. The visited network is then a single roamer port
area which includes multiple MSCs. Thus, the RPN provides
a port into the visited network, but does not identify to
the home network a particular MSC within the visited network
in which the subscriber may be found.
Existing telecommunication systems have solved this
problem either by providing a separate RPN for each MSC in
the network, or with a technique called sequential paging
of manual visitors. In sequential paging, a calling party
dials the RPN, obtains a dial tone from the visited network,
and dials the subscriber's telephone number as usual.
Howe~er, the visited network does not know which MSC the
subscriber is in. Therefore, the call is initially routed
to an entry MSC which may be, for example MSCl. The network
pages for the subscriber in MSCl ~ and if there is a page
response, the call is completed. If the subscriber is not
found, the call is routed via a trunk to the next MSC along
a routing path which may be, for example, MSC2. The network
then pages for the subscriber in MSC2, and if there is a
page response, the call is completed. If the subscriber is
not found, the call is routed via a trunk to additional MSCS
until the last MSC in the network is paged. If there is
still no response, an action defined by the MSC data is
performed. For example, the calling party may be informed
that the mobile station cannot be reached. Sequential
paging ties up trunk resources and can take a considerable
period of time to complete the call, depending on the number
of MSCs which must be paged before the subscriber is found.
, .
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FIG. 4 is an illustrative representation of a visited
cellular radio communications network 51 that does not have
an automatic roaming agreement with the home network and has
been implemented with a manual home location register (M-
HLR) 52 of the present invention. The present inventionsolves many of the problems associated with registration of
manual visitors and call delivery to manual visitors by
providing a means for treating manual visitors as automatic
visitors. The M-HLR 52 includes a database for manual
visitors, and is implemented within the network 51 and
connected to MSC1, MSC2, and MSC3. The M-HLR 52 may be a
standalone node, may be co-located with any MSC in the
network, or may be co-located with a HLR, if applicable.
If implemented as a standalone node, the M-HLR 52 has its
own standalone processor to perform database and control
functions. If co-located with a MSC or HLR, the M-HLR 52
may share a processor while accessing its manual visitor
database.
Data on each manual visitor is maintained in the M-HLR
52 instead of the MSC where the manual visitor initiates an
access. This data is then shared between the multiple MSCs
by means of the network's automatic visitor signaling links
53 so that manual visitors do not need to re-register when
they roam from one MSC to another MSC within the visited
network 51.
The first time a manual visitor makes a call in the
visited network from, for example, MSC1, the
registration/validation procedures are unchanged from the
existing procedures as illustrated in FIG. 3. However, the
registration is recorded in the M-HLR 52, instead of MSC1
in which the manual visitor is located. The manual visitor
can then move freely around the visited network 51 without
having to re-register in each MSC. Cancellations of
subscriber records in the M-HLR 52 are based on activity
supervision, as is currently performed in existing systems.
Maintenance of manual visitor records in the M-HLR 52 has
the additional benefit of increasing the subscriber capacity
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of the MSC's in the visited network 51. All of the MSC's
available records may be reserved for automatic visitors
since there is no need to reserve any records for manual
visitors.
The present invention also improves the process of call
delivery to manual visitors. Instead of using sequential
paging, which can tie up valuable trunk resources for
extended periods of time, call delivery is handled with
Local Access funciton, as it is for an automatic visitor.
Calls to a m~nl7~l visitor from other networks are delivered
to a roamer port number (RPN) where a second dial tone is
generated toward the calling subscriber. The calling
subscriber then dials the called mobile subscriber's 10-
digit directory number, which includes the 3-digit area
code. Thereafter, the call delivery process follows the
message flow illustrated in FIG. 5.
FIG. 5 is a signaling diagram illustrating the flow of
messages between an originating MSC 61, a HLR 62, and a
serving MSC 63 during call delivery to a mobile subscriber
that is outside the serving area of the MSC 61 where the
call originates. MSCs in the functional model described in
IS-41.1 contain switching functions only and must interact
with their associated HLR and VLR in order to obtain
database information for a mobile station. In real
applications, the HLR and VLR functions may be integrated
within the MSC.
At step 81, a call to be routed to a roamer port access
is received from the public switched telephone number
(PSTN), and a second dial tone is generated toward the
calling subscriber. The calling subscriber then dials the
called subscriber's 10-digit directory number. At step 82,
the originating MSC 61 sends a LOCREQ (Location Request)
INVOKE message 66 to the HLR 62 associated with the mobile
station. This association is made through the dialed mobile
address digits.
At step 83, if the dialed mobile address digits are
assigned to a legitimate subscriber, and if call forward
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unconditional is not in effect (as defined by the service
profile) the HLR 62 sends a ROUTREQ (Routing Request) INVOKE
message 67 to the VLR 68 that last provided a registration
notification. This serving VLR 68 then forwards a ROUTREQ
INVOKE message 69 to the current serving MSC 63. The mobile
station may have roamed within the network served by the
serving VLR 68 and reported its new location to the serving
VLR 68 via the serving MSC 63. The serving VLR 68 may not
have reported this change in location to the HLR 62.
In response to the ROUTREQ INVOKE message 69, the
serving MSC 63 consults its internal data structures to
determine if the mobile station is already engaged in a call
on this MSC. In the example illustrated in FIG. 5, the
mobile station is idle, and it is assumed that the mobile
station is not known to the serving MSC 63. The serving MSC
63 may then obtain the service profile of the mobile
subscriber at step 84 by sending a PROFREQ INVOKE message
71 to the serving VLR 68. The service profile is returned
in a PROFREQ response message 72. Step 84 may be eliminated
if the service profile is obtained by the serving MSC 63
prior to the termination attempt (e.g. when the mobile
registers).
At step 85, if the mobile station is located in the
roamer port area, then the serving exchange MSC 63 allocates
a temporary local directory number (TLDN) and returns this
information to the HLR 62 in a ROUTREQ response message 73.
Otherwise, if the mobile station was located outside the
roamer port area, then the call is terminated according to
the ~x~h~nge data. When the ROUTREQ response message 73 is
received by the HLR 62, the HLR constructs a LOCREQ response
message 74 by adding the mobile identification number (MIN)
and electronic serial number (ESN) of the mobile to the
information provided by the serving MSC 63. The HLR 62 then
returns the LOCREQ response message 74 to the originating
MSC 61. At call setup at step 86, the originating MSC 61
establishes a voice path to the serving MSC 63 using
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existing interconnection protocols and the TLDN specified
in the LOCREQ response message 74.
It is thus believed that the operation and construction
of the present invention will be apparent from the foregoing
description. While the method, apparatus and system shown
and described has been characterized as being preferred, it
will be readily apparent that various changes and
modifications could be made therein without departing from
the spirit and scope of the invention as defined in the
following claims.
