Title: Methods and apparatus for supporting optimum call routing in a cellular telecommunications system
Abstract: Disclosed are methods for operating a wireless terminal or mobile station in a wireless telecommunications system. A first method includes steps of (a) transmitting a telephone number that includes an identifier for specifying that a user of the mobile station is calling a second mobile station that is believed to be roaming in a current serving system; (b) receiving the telephone number in the current serving system, typically at a mobile switching center (MSC); (c) detecting the presence of the identifier and, in response, determining if the telephone number is one that is stored in a Visitor Location Register (VLR) of the current serving system. If yes, the method includes a step (d) of paging the second mobile station in the current serving system. In one embodiment the step of transmitting includes an initial step of entering an identifier character into a memory of the mobile station, followed by the telephone number of the second mobile station. In a second embodiment the step of transmitting includes an initial step of entering the telephone number of the second mobile station into the memory of the mobile station, followed by the identifier character. In a second method the MSC automatically determines if a received telephone number is one that is associated with a potential roamer. If yes, the MSC checks to see if the telephone number is present in the MSC's VLR. If yes, the mobile station associated with the telephone number is paged.
Patent Number: 6,871,072 Issued on 03/22/2005 to Meche
| Inventors:
|
Meche; Paul S (Richardson, TX)
|
| Assignee:
|
Nokia Corporation (Espoo, FI)
|
| Appl. No.:
|
933911 |
| Filed:
|
September 23, 1997 |
| Current U.S. Class: |
455/445; 455/432.1; 455/433; 455/435.1 |
| Intern'l Class: |
H04Q 007//20 |
| Field of Search: |
455/445,432.1-432.3,433,435.1,458,459,460,461
|
References Cited [Referenced By]
U.S. Patent Documents
| 5175758 | Dec., 1992 | Levanto et al. | 379/57.
|
| 5394391 | Feb., 1995 | Chen et al. | 370/18.
|
| 5898922 | Apr., 1999 | Reininghaus | 455/433.
|
| Foreign Patent Documents |
| 96/20574 | Apr., 1996 | WO | .
|
Primary Examiner: Nguyen; Lee
Attorney, Agent or Firm: Harrington & Smith, LLP
Claims
What is claimed is:
1. A method for operating a wireless telecommunications system, comprising
the steps of:
providing a telephone number and an identifier for specifying that a caller
is calling a mobile station that is believed to be roaming in a particular
serving system, where providing the telephone number includes an initial
step of entering the telephone number of the called mobile station into a
memory of a calling mobile station, followed by an identifier character;
receiving said telephone number and said identifier in the serving system;
detecting the presence of said identifier and, in response, without
interrogating another serving system, determining if said telephone number
is one that is stored in a Visitor Location Register of said serving
system; and
if yes, paging said mobile station in said serving system.
2. A cellular telecommunications system, comprising:
a first mobile station for transmitting a telephone number that includes an
identifier specifying that a user of the first mobile station is calling a
second mobile station which is believed to be roaming in a current serving
system; and
a first base station and mobile switching center (MSC) for receiving the
telephone number in the current serving system, said MSC including a
controller that detects a presence of the identifier and, in response,
determines without interrogating another mobile switching center if the
telephone number is one that is stored in a Visitor Location Register of
the MSC and, if yes, pages the second mobile station using the first or a
second base station, wherein said first mobile station includes a keypad
for entering the telephone number of the second mobile station into a
memory of the mobile station, followed by an identifier character.
3. A method for operating a wireless telecommunications system, comprising
the steps of:
transmitting a telephone number that includes an appended identifier for
specifying that a first mobile station is calling a second mobile station
that may be roaming in a particular serving system;
receiving the telephone number in the serving system;
detecting the presence of the appended identifier and, in response, without
interrogating another serving system, examining a Visitor Location
Register of the serving system to determine if the telephone number is one
that is associated with a valid roaming mobile station; and
if the telephone number is determined to be one that is associated with a
valid roaming mobile station, paging the second mobile station in the
serving system, else, performing one of completing the call using a
conventional call completion technique or sending a message to the first
mobile station for indicating that the telephone number is not one that is
associated with a valid roaming mobile station.
4. A method as in claim 3, wherein the step of sending a message includes a
further step of terminating the call.
5. A method for operating a wireless telecommunications system, comprising
the steps of:
providing a telephone number of a called party;
receiving said telephone number in a serving system, the received telephone
number having an appended identifier;
in response to detecting the presence of the appended identifier,
determining if said telephone number is for a mobile station potentially
roaming in the serving system, without interrogating another serving
system;
if yes, determining if said telephone number is stored in a Visitor
Location Register of the serving system; and
if yes, paging the mobile station in the serving system.
6. A cellular telecommunications system, comprising:
a first mobile station for transmitting a telephone number that comprises
an appended identifier; and
a first base station and mobile switching center (MSC) which receives said
telephone number in a serving system, said MSC including a controller
which determines based on said appended identifier if said telephone
number is associated with a mobile station potentially roaming in said
serving system and, without interrogating another mobile switching center,
determines if the telephone number is one that is stored in a Visitor
Location Register of the MSC and, if yes, pages the roaming mobile station
using said first or a second base station.
7. A method for operating a wireless telecommunications system, comprising
the steps of:
at a first mobile switching center, receiving a telephone number having an
appended identifier, wherein said telephone number is registered in a home
location register of a second mobile switching center;
in response to the presence of said appended identifier, checking a visitor
location register of said first mobile switching center to determine if
said telephone number is a valid roaming number under said first mobile
switching center; and
paging a roaming mobile station identified with said telephone number;
wherein said home location register of said second mobile switching center
is not accessed.
8. A switching center for mobile cellular telecommunications, comprising:
a visitor location register;
a home location register; and
a controller that controls message switching to at least one base station;
wherein when a received telephone number having an appended pre-translation
identifier is received, said controller looks for said telephone number in
said visitor location register without communicating with another mobile
switching center, and if said telephone number is found in said visitor
location register said controller pages a roaming mobile station
associated with said telephone number using said base station.
Description
FIELD OF THE INVENTION
This invention relates generally to radiotelephones and, in particular, to
radiotelephones or mobile stations such as those capable of operation with
a cellular network.
BACKGROUND OF THE INVENTION
Occasions arise wherein a user of a first radiotelephone, such as a
cellular telephone, desires to contact a user of a second radiotelephone
who is known to be or believed to be roaming within a service area of the
first user. For example, the first user can be in a service area within
the Los Angeles area, while the second user may be an acquaintance or
business associate from Miami who is known to be or believed to be in the
Los Angeles area. Under conventional practice the first user can dial the
number of the second user. A mobile switching center (MSC) that handles
the call will recognize the area code for Miami and will route the call to
a MSC in the Miami area. The Miami MSC will find from its Home Location
Register (HLR) that the second user is actually roaming in the Los Angeles
area, and will route the call back to the Los Angeles MSC. It can be
appreciated that this technique is not efficient, and furthermore can
result in the users incurring significant long distance charges for a call
that may be required to go only a few blocks.
It is also known in the art to provide a two-stage dialing approach using
local roamer access ports. These telephone numbers were known to be
published (and may still be published) on a system by system basis
throughout the United States. The result was a small book that was
typically out of date due to area code changes, etc. In this system, one
looked up the system and the area (there were only two systems in this
method, not the seven that resulted from the PCS spectrum auction), then
dialed that local number, then waited for a second dial tone, and then
dialed the called party number. As can be appreciated, this technique also
does not provide an optimum solution for contacting roaming users.
OBJECTS OF THE INVENTION
It is thus a first object and advantage of this invention to provide an
improved method for contacting a roaming user that is simpler, more
user-friendly, and that does not require one to have knowledge of local
access numbers.
It is a further object and advantage of this invention to provide a method
for contacting a roaming user, wherein an identifying code is prepended or
appended to a dialed telephone number and transmitted from a
radiotelephone, wherein a MSC that detects the code examines its Visitor
Location Register (VLR) to determine if the called number is a number that
is valid for an active roaming user, and wherein the MSC then connects the
call to the roaming user without requiring that a long distance call be
made.
It is another object and advantage of this invention to provide a method
for contacting a roaming user, wherein a MSC that detects that a dialed
telephone number may be associated with a roaming user automatically
examines its Visitor Location Register (VLR) to determine if the called
number is a number that is valid for an active roaming user, and wherein
the MSC then connects the call to the roaming user without requiring that
a long distance call be made.
SUMMARY OF THE INVENTION
The foregoing and other problems are overcome and the objects of the
invention are realized by methods and apparatus in accordance with
embodiments of this invention. Methods of this invention are disclosed for
operating a wireless terminal or mobile station in a wireless
telecommunications system, such as a cellular telecommunications system.
A first method includes steps of (a) transmitting a telephone number that
includes an identifier for specifying that a calling party is calling a
mobile station that is believed to be roaming in a current serving system;
(b) receiving the telephone number in the current serving system,
typically at a mobile switching center (MSC); (c) detecting the presence
of the identifier and, in response, determining if the called party has a
number that is available in a Visitor Location Register (VLR) of the
current serving system; and, if yes, (d) paging the called mobile station
in the current serving system.
In one embodiment the step of transmitting includes an initial step of
entering an identifier character, followed by the telephone number of the
called mobile station. In a second embodiment the step of transmitting
includes an initial step of entering the telephone number of the called
mobile station, followed by the identifier character.
A second method includes steps of (a) transmitting a telephone number from
a calling party that is calling a mobile station that is believed to be
roaming in a current serving system; (b) receiving the telephone number in
the current serving system, typically at the mobile switching center; (c)
determining if the telephone number may be associated with a roaming user
and, if yes, determining if the called party has a number that is
available in a Visitor Location Register (VLR) of the current serving
system; and, if yes, (d) paging the called mobile station in the current
serving system.
BRIEF DESCRIPTION OF THE DRAWINGS
The above set forth and other features of the invention are made more
apparent in the ensuing Detailed Description of the Invention when read in
conjunction with the attached Drawings, wherein:
FIG. 1 is a block diagram of a mobile station that is constructed and
operated in accordance with this invention;
FIG. 2 is an elevational view of the mobile station shown in FIG. 1, and
which further illustrates a cellular communication system to which the
mobile station is bidirectionally coupled through wireless RF links;
FIG. 3 is a logic flow diagram that is descriptive of a first method in
accordance with this invention; and
FIG. 4 is a logic flow diagram that is descriptive of a second method in
accordance with this invention.
DETAILED DESCRIPTION OF THE INVENTION
Reference is made to FIGS. 1 and 2 for illustrating a wireless user
terminal or mobile station 10, such as but not limited to a cellular
radiotelephone or a personal communicator, that is suitable for practicing
this invention. The mobile station 10 includes an antenna 12 for
transmitting signals to and for receiving signals from a base site or base
station 30. The base station 30 is a part of a cellular network that may
comprise a Base Station/Mobile Switching Center/Interworking function
(BMI) 32 that includes a mobile switching center (MSC) 34.
The MSC 34 provides a connection to landline trunks, such as the Public
Switched Telephone Network (PSTN) 36, when the mobile station 10 is
involved in a call. Typically the MSC 34 will be bidirectionally coupled
to a plurality of base stations 30 in a service area, each of the base
stations 30 serving an associated cell. The MSC 34 includes a Visitor
Location Register (VLR) 34A, wherein the identities (typically the
telephone numbers) of authorized roaming mobile stations are recorded
after registering with the MSC 34, a Home Location Register (HLR) 34B,
wherein are recorded the identities of those mobile stations that are
associated with the MSC 34 in a "home" or normal serving system mode of
operation, and a data processor or controller 34C that implements a MSC
method in accordance with this invention.
The mobile station includes a modulator (MOD) 14A, a transmitter 14, a
receiver 16, a demodulator (DEMOD) 16A, and a controller 18 that provides
signals to and receives signals from the transmitter 14 and receiver 16,
respectively. These signals include signalling information in accordance
with the air interface standard of the applicable cellular system, and
also user speech and/or user generated data. The air interface standard is
assumed for the purposes of this invention to include any suitable
physical and logical structure, and may be a conventional analog AMPS air
interface or a digital air interface, such as a TDMA interface (e.g.,
IS-136 compatible) or a CDMA air interface (e.g., IS-95 compatible). Dual
mode (e.g., AMPS/TDMA or AMPS/PCS) mobile stations may also take advantage
of the teachings of this invention. The mobile station 10 can be a vehicle
mounted or a handheld device. It should further be appreciated that the
mobile station 10, as was described above, can be capable of operating
with one or more air interface standards, modulation types, and access
types.
The controller 18 also includes the circuitry required for implementing the
audio and logic functions of the mobile station. By example, the
controller 18 may be comprised of a digital signal processor device, a
microprocessor device, and various analog to digital converters, digital
to analog converters, and other support circuits. The control and signal
processing functions of the mobile station are allocated between these
devices according to their respective capabilities.
A user interface includes a conventional earphone or speaker 17, a
conventional microphone 19, a display 20, and a user input device,
typically a keypad 22, all of which are coupled to the controller 18. The
keypad 22 includes the conventional numeric (0-9) and related keys (#,*)
22a, and other keys 22b used for operating the mobile station 10. These
other keys 22b may include, by example, a SEND key, various menu scrolling
and soft keys, and a PWR key. The mobile station 10 also includes a
battery 26 for powering the various circuits that are required to operate
the mobile station.
The mobile station 10 also includes various memories, shown collectively as
the memory 24, wherein are stored a plurality of constants and variables
that are used by the controller 18 during the operation of the mobile
station. For example, the memory 24 stores dialed telephone numbers prior
to their transmission to the base station 30, as well as the values of
various cellular system parameters and the number assignment module (NAM).
An operating program for controlling the operation of controller 18 is
also stored in the memory 24 (typically in a ROM device). The memory 24
may also store data, including user messages, that is received from the
BMI 32 prior to the display of the messages to the user. The memory 24
also includes software routines for implementing the methods described
below in relation to FIGS. 3 and 4.
Reference is now made to FIG. 3 for illustrating a first method in
accordance with this invention.
At Block A the user dials a number using the keypad 22. It is assumed that
the mobile station 10 has already registered with the MSC 34. It is
further assumed that the user is calling the mobile station 10', which is
known to be or is believed may be roaming in the system served by MSC 34.
As such, the dialed telephone number is a number outside of the range of
telephone numbers served by the MSC 34. In accordance with this embodiment
of the invention the user either adds as a prefix (prepends) or as a
suffix (appends) a `pre-translation` identifier, such as the character
`#`, to the dialed telephone number. For example, the user dials `#1 203
555 1212`, where `1` is the country code and `555` is the exchange, where
the `203` area code is not one that is associated with the MSC 34, and
where the `#` character is the defined pre-translation identifier
character. The entered identifier character and the telephone number are
stored temporarily in the memory 24 of the mobile station 10, in a
conventional manner.
At Block B the user depresses the SEND key on the keypad 22, or performs
some other action, for causing the mobile station 10 to transmit the
stored telephone number and pre-translation identifier character to the
MSC 34, via the base station 30 having a cell within which the mobile
station 10 is currently located. The telephone number and identifier is
then received at the MSC 34.
At Block C the controller 34C of the MSC 34 parses or otherwise examines
the received telephone number. For the case where the pre-translation
identifier is not present, control passes to Block D to handle the call in
a normal fashion. However, if the controller 34C detects the presence of
the pre-translation identifier, control passes instead to Block E where
the controller 34C examines the VLR 34A to determine if the telephone
number of the called party is present. More particularly, the MSC
controller 34C determines if the called party is active and valid
(authorized to receive service in the serving system of the MSC 34). If
no, control passes, in one embodiment, to Block D where the call is
completed in a normal fashion. For example, the MSC 34 signals the MSC of
the serving system of the called telephone number, and an attempt is made
to complete the call through the PSTN 36. In this case a long distance and
possibly other charges may be incurred. In a second embodiment a digital
or audio message is sent to the mobile station 10 (Block F) to indicate
that the called party is not available. For example, the called party may
not have yet turned on his or her mobile station 10' and registered with
the MSC 34, or the called party attempted to register as a roamer with the
MSC 34 but was denied service, or the called party is not actually roaming
as the calling party expected.
During the execution of Block F the call can be automatically terminated by
the MSC 34 or, instead, the user may be given an option to (a) simply
terminate the call (such as by hanging up) or (b) to instead complete the
call using conventional call completion techniques. In the former case the
user of the mobile station 10 may simply elect to wait and try the call
later, or may use some other means to contact the called party, such as
through a conventional landline call. In the latter case an attempt to
reach the called party can be made by using conventional cellular long
distance calling techniques (e.g., control passes back to Block D after
the user enters an appropriate code using the keypad 22).
Returning to Block E, and for the case where the called number is found in
the VLR 34A, control passes to Block G where the controller 34C causes one
or more of the base stations 30 to transmit a page message indicating that
the mobile station 10' has an incoming call. Assuming that the user of the
mobile station 10' answers the call (e.g., the mobile station 10'
generates an alerting or ringing tone and the user depresses the SEND or
some other key to answer the call), then control passes to Block H to
connect the call as an intra-system call from the mobile station 10 to the
mobile station 10' using the same or a different base station 30,
depending on the location of the mobile station 10'.
Reference is now made to FIG. 4 for illustrating a second method in
accordance with this invention. At Block A the user dials a number using
the keypad 22. As before, it is assumed that the mobile station 10 has
already registered with the MSC 34 and that the user is calling the mobile
station 10'. In accordance with this second embodiment of the invention
the user is not required to either prepend or append one or more
pre-translation identifiers.
At Block B the user depresses the SEND key on the keypad 22, or performs
some other action, for causing the mobile station 10 to transmit the
telephone number to the MSC 34, via the base station 30 having the cell
within which the mobile station 10 is currently located. The telephone
number is then received at the MSC 34.
At Block C the controller 34C of the MSC 34 parses or otherwise examines
the received telephone number. Based on the content of the called number,
such as the area code, the controller 34C makes a determination as to
whether the called party is a potential roamer. For example, and for the
case where area code does not match an area code served by the MSC 34, the
called party can be considered a potential roamer in the system served by
the MSC 34. For the case where the called party is determined not to be a
potential roamer, control passes to Block D to handle the call in a normal
fashion. In this case the telephone number of the called party may be
present in the HLR 34B of the MSC 34. That is, the called party may be one
served by the MSC 34. However, if the controller 34C instead detects at
Block C that the called party is a potential roamer, control passes to
Block E where the controller 34C examines the VLR 34A to determine if the
telephone number of the called party is present. As in the first
embodiment, the MSC controller 34C determines if the called party is
active and valid (authorized to receive service in the serving system of
the MSC 34). If the called number is not present in the VLR 34A, control
passes to Block D where the call is completed in a normal fashion.
Returning to Block E, and for the case where the called number is present
in the VLR 34A, control passes to Block F where the controller 34C causes
one or more of the base stations 30 to transmit a page message indicating
that the mobile station 10' has an incoming call. Assuming that the user
of the mobile station 10' answers the call then control passes to Block G
to connect the call as an intra-system call from the mobile station 10 to
the mobile station 10' using the same or a different base station 30,
depending on the location of the mobile station 10'.
As should be apparent, one advantage of the use of the teaching of this
invention is that it is possible to eliminate long distance charges for
the calling and called parties. The use of the this invention also
eliminates a need, at least in North American systems, to know the local
port for the serving system, and the need to use two stage dialing. As
such, the `user-friendliness` of the cellular system is enhanced, without
incurring undue complexity and while reducing unnecessary costs.
Although described in the context of preferred embodiments, it should be
realized that a number of modifications to these teachings may occur to
one skilled in the art. By example, any suitable character can be used as
the pre-translation identifier, such as the `*` character instead of the
`#` character, or by the definition of a new character. In other
embodiments more than one pre-translation identifier character can be
used, such as by prepending or appending both of the `#` and `*`
characters to the telephone number of the mobile station 10', or by
prepending the `#` character and then appending the `*` character to the
telephone number of the mobile station 10'. Of course, care must be taken
to minimize conflicts with any previously defined translation characters
that may be used for other purposes. As such, it may be desirable in some
cases to define a new character for use as the pre-translation identifier.
For the embodiment of FIG. 4, the test in Block C can be refined so as to
first determine if the called number is a number associated with a mobile
station or with a landline phone. In this embodiment, and only when it is
first determined that the called number is associated with a mobile
station, is the VLR 34A examined. This embodiment may be more practical to
implement in those systems, such as GSM, wherein the numbering plan
enables a ready association of a given telephone number with one of a
mobile station or a landline phone, and may be less readily implemented
under the North American numbering plan.
Also, the teaching of this invention is not limited to making voice calls,
in that data calls, messaging, and facsimile transmissions can also be
made using the teachings of this invention.
Thus, while the invention has been particularly shown and described with
respect to preferred embodiments thereof, it will be understood by those
skilled in the art that changes in form and details may be made therein
without departing from the scope and spirit of the invention.
*
