Note: Descriptions are shown in the official language in which they were submitted.
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TELEMETRY NUMBERING FOR SMS AND USSD
BACKGROUND
The present invention relates to mobile telecommunication switching
networks. More specifically, the present invention relates to the
interrogation of
mobile stations that are statically employed (i.e., immobile), such as mobile
stations
employed in telemetry applications, and how a mobile telecommunications
switching
network can take advantage of this inunobility to conserve the limited supply
of
subscriber numbers and to reduce the ever increasing workload on network
components
such as the home location register (HLR).
Mobile telecommunications networks, such as the Personal Digital
Telephone System (PDC) in Japan, and the Groupe Sp6cial Mobile (GSM) System in
Europe, provide services other than cellular voice services. For example,
mobile
telecommunications networks now provide messaging services. Messaging
services, in
general, permit mobile stations to be interrogated using short message
packets, wherein
the message packets typically include requests, and responses to requests, for
non-voice
type data. In the PDC system, a well-known short message service (SMS) is
employed
as a bearer for short message packets. In GSM, a similar SMS is employed as
well as
a well-known signalling mechanism known as unstructured supplementary service
data
(USSD).
In one example, SMS may be employed as a bearer for short message
packets in a telemetry application. In accordance with this exemplary use of
SMS, it is
characteristic for a host computer to contact one or more telemetry sites over
a mobile
link, wherein each telemetry site is supported by mobile station. The host
computer
uses short message packets to interrogate each of the one or more telemetry
sites. The
interrogation generally involves a request that each of the sites transmit
certain
information back to the host computer. For example, a utility company, such as
an
electric power company, might employ a host billing computer to interrogate
electric
meters over a mobile link, wherein each of the electric meters are supported
by a
mobile station. In this example, the billing computer transmits to the one or
more
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electric meters a short message requesting that each meter transmit their
current meter
reading back to the billing computer. The request includes a unique subscriber
number
for each meter so that the short message containing the request is properly
delivered by
the telecommunications switching network. The host computer, upon receiving
the
requested information, can then automatically bill its customers.
In all mobile telecommunications networks, each subscriber is assigned a
unique numerical identity. In the PDC system, the unique numerical identity is
called
the mobile subscriber number (MSN). The MSN, in turn, includes an access code,
an
operator code and a subscriber number. In the GSM system, the unique numerical
identity is called the mobile subscriber ISDN (MSISDN) number. The purpose of
the
MSNs and the MSISDNs is to provide each subscriber with a unique address
within the
PDC and GSM networks respectively. As one skilled in the art will readily
appreciated, the MSNs and the MSISDNs are part of the E. 164 international
number
plan. Herein below, MSN and MSISDN are frequently referred to as subscriber
numbers, for the purpose of simplicity. In addition to assigning a unique
subscriber
number to each subscriber, the radio interface between each subscriber and the
network
is assigned an international mobile subscriber identity (IMSI), in accordance
with the
E.212 numbering plan. The IMSI is also used for distinguishing between mobile
stations operating within a given network.
When a calling party (i.e., the party placing a call) dials a subscriber
number (i.e., A MSN or a MSISDN) associated with a called party, the
teleconununications network uses the subscriber number to access a subscriber
record
corresponding to the called party in the network HLR. The subscriber record
contains,
among other things, the information and procedures necessary for routing
calls, short
messages, and other services to the mobile switching center (MSC) service area
in
which the called party is located, and eventually to the mobile station
corresponding to
the called party. This information may include, for example, a mobile
switching center
identification number (MSC-ID) or a routing number, and an IMSI. The MSC-ID or
routing number is used for routing the call or message to the appropriate MSC
which
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controls the MSC service area in which the called party is located. The IMSI
is then
used to send the call or message from the MSC to the mobile station.
In accordance with the present state of the art, every subscriber has a
unique subscriber number. This is true whether the subscriber subscribes to a
cellular
voice service or a non-voice service, such as telemetry. Unfortunately, as the
demand
for mobile services increases, the availability of subscriber numbers
decreases. In
addition, the increase in demand for mobile services has drastically increased
the
workload on telecommunications network components such as the HLR. This, in
turn,
decreases network performance as it takes a longer period of time to access
the HLR to
obtain the information and/or procedures necessary to locate and service
intended
subscribers within the switching network. Therefore, a need'exists wherein a
telecommunications switching network can limit the number of subscriber
numbers
assigned, thereby preventing the exhaustion of the E. 164 numbering plan, and
to
reduce the workload on network components, particularly the HLR, to prevent
network
performance degradation.
SUAlMARY
The present invention takes advantage of the fact that in some mobile
telecommunications network applications, for example, in most telemetry
applications,
the mobile stations are not truly mobile. In other words, the location of
mobile stations
employed for such purposes does not change. Since the location of these mobile
stations is already known, the present invention does not require that the
calling party
(e.g., a host computer) specify a subscriber number to locate such mobile
stations.
Accordingly, there is no need to assign unique subscriber numbers to these
mobile
stations. Therefore, the present invention reduces the number of required
subscriber
numbers by eliminating the need to assign such numbers to mobile stations
employed
for static applications. Moreover, the present invention reduces the traffic
into and out
of the network HLR, as there is no longer any need to access the HLR database
to
obtain location information.
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Accordingly, it is an objective of the present invention to reduce the
number of subscriber numbers for mobile stations operating within a mobile
telecommunications network.
It is another objective of the present invention to reduce and/or eliminate
the necessity of assigning subscriber numbers to mobile stations that are
specifically
employed in static and or non-mobile applications.
It is still another objective of the present invention to reduce the number
of IMSIs required for mobile stations being utilized in static or non-mobile
applications.
It is yet another objective of the present invention to improve network
performance by reducing the traffic and/or the workload on network components,
particularly the network HLR.
In accordance with one aspect of the present invention, the foregoing and
other objects are achieved by a method and/or an apparatus for routing a
message to a
called party in a telecommunications network. The method and/or apparatus
involves
generating a message, in a node that is external to the telecommunications
network, for
the called party. The message includes a subscriber identity code
corresponding to the
called party. The method and/or apparatus also involves transmitting the
message from
the external node to a network switching center associated with a service
area, in which
the called party is located, in accordance with an area identification code;
and
forwarding the message from the switching center to the called party as a
function of
the subscriber identity code, wherein the called party is statically located
in the service
area.
In accordance with another aspect of the present invention, the foregoing
and other objects are achieved by a method and/or an apparatus for controlling
the
routing of a message in a mobile telecommunications network. The method and/or
apparatus involves generating a message, in a node that is external to the
mobile
telecommunications network, to a mobile station statically located in an area
of the
mobile telecommunications network; appending a mobile station identification
code to
the message, wherein the mobile station identification code uniquely
identifies the
mobile station; and translating the mobile station identification code into an
area
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identification code and an international mobile subscriber identity code. Once
the
mobile station identification code has been translated, the method and/or
apparatus
forwards the message to the mobile telecommunications network. The message is
then
routed to a switching center associated with the network area in which the
mobile
station is located, in accordance with the area identification code, and sent
from the
switching center to the mobile station using the international mobile
subscriber identity
code.
BRIEF DESCRIPTION OF THE DRAWINGS
The objects and advantages of the invention will be understood by
reading the following detailed description in conjunction with the drawings in
which:
FIG. 1 is diagram depicting a host computer placing a short message to a
mobile station in the PDC system, in accordance with the prior art;
FIG. 2 is a diagram depicting a host computer transmitting a short
message to a mobile station in the GSM system, in accordance with the prior
art;
FIG. 3 is a diagram of a host computer transmitting a short message to a
mobile station in the PDC system, in accordance with the present invention;
and
FIG. 4 is a diagram of a host computer transmitting a short message to a
mobile station in the GSM system, in accordance with the present invention.
FIG. 5 is a diagram of an external node transmitting information to a
mobile station using USSD.
DETAILED DESCRIPTION
FIG. 1 illustrates how a host computer 105 interrogates a mobile station
110 in the PDC system, in accordance with the present state of the art. First,
the host
computer 105 submits (1) a request for a message to be delivered to one or
more
mobile stations (e.g., mobile station 110). In the PDC system, the message
request is
submitted to a short message service center (SMS-C) 115. Generally, the SMS-C
115
is a node external to the switching network. The function of the SMS-C 115 is
to take
the host computer's request and construct one or more appropriate messages in
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accordance with the short message service protocol. In order to ensure that
each
message reaches the intended mobile station, each message has appended to it a
MSN.
Next, the SMS-C 115 transmits (2) the message, along with the MSN, to
an inter-working/gateway mobile switching center (IW/G-MSC) 120. The IW/G-MSC
120 then forwards (3) the MSN to the home location register (HLR) 125. The HLR
125 is essentially a large database that contains a subscriber record for each
subscriber
in the network. The subscriber record includes, among other things,
information
identifying which of the many service areas the subscriber is currently
located in, as
one skilled in the art will readily appreciate. Accordingly, the HLR 125
forwards to
the IW/G-MSC 120, what is called a pursuit routing number (PRN) and an IMSI.
The
PRN is essentially an identification number or address for the mobile
switching center
(MSC), or visiting mobile switching center (VMSC) 130, controlling the service
area in
which the mobile station 110 is located.
The IW/G-MSC 120 packages the IMSI into an end-to-end information
field of a message packet, as is well-known in the art. The IW/G-MSC 120 then
forwards (4) the message packet to the appropriate VMSC 130, in accordance
with the
PRN, using an ISDN user part (ISUP) signalling protocol. The VMSC 130 then
unpacks the message packet, pages the mobile station 110 using the IMSI, and
delivers
the short message containing the host computer's request to the mobile station
110.
FIG. 2 illustrates how a host computer 205 similarly interrogates a
mobile station 210 in the GSM system using a short message service protocol,
in
accordance with the present state of the art. First, the host computer 205
generates a
short message request. Appended to the short message request is the address of
a
desired short message service center (SC), for example, SC-A 215. Also
appended to
the short message request is the MSISDN that corresponds to the intended
mobile
station 210. The host computer 205 then transmits (1) the short message
request to the
SC-A 215 over an SME interface (e.g., a GSM 03.49 interface), as is well
understood
by those skilled in the art.
The SC-A 215 then forwards (2) the short message to the GSM network.
The SC-A 215 transmits the short message, for example, in accordance with a
well-
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known SMS mobile application protocol 03.49 (e.g., SMS-MAP). The short message
enters
the network via a short message service, gateway mobile switching center (SMS-
GMSC) 220.
The SMS-GMSC 220 then uses the SMS-MAP to transmit (3) a send routing
information for
short message (SRIFSM) instruction to the HLR 225. The SRIFSM instruction also
contains
the MSISDN corresponding to the intended mobile station 210. The HLR 225 uses
the
MSISDN to access the subscriber record corresponding to mobile station 210. As
described
above, the subscriber record contains, among other things, information
relating to the location
of the mobile station 210. In response to the SRIFSM instruction, the HLR 225
sends (4) an
MSC-ID code and an IMSI to the SMS-GMSC 220, wherein the MSC-ID code is the
network
address for the VMSC 230 controlling the service area in which the mobile
station 210 is
Iocated. The SMS-MSC 220, in turn, sends (5) the short message to the VMSC
230, which
forwards the message to the mobile station 210 using the IMSI.
In GSM, the host computer 205 may alternatively employ a USSD signalling
protocol
to communicate with a desired mobile station, as described in U.S. Granted
Patent 5,752,188.
In accordance with the USSD signalling protocol, the host computer 205
typically interfaces
directly with the network HLR 225 or with the VMSC 230. Moreover, the request
generated
by the host computer 205 contains or includes the MSISDN corresponding to the
intended
mobile station 210. The MSISDN is then translated into a VMSC-ID and/or an
IMSI.
Therefore, the same inefficiencies that plague the network when the host
computer 205
transmits a message packet to the mobile station 210 in accordance with the
SMS as illustrated
in FIG. 2, also apply if the host computer employs USSD.
FIG. 3, however, illustrates how a host computer 305, in accordance with the
present
invention, interrogates one or more mobile stations in the PDC system, wherein
the mobile
stations are employed in a static application such as a telemetry application,
or a remote
programming application. This does not mean, however, that the mobile station
is completely
fixed or immobile. The mobile station may in fact be restricted in mobility
with respect to a
particular area or region within the network such as a mobile station service
area and/or a
paging area.
Amended Sheet
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First, the host computer 305 submits (1) a request to transmit a message,
using a SMS, to one or more mobile stations such as the mobile station 310
and/or the
mobile station 315. The mobile stations 310 and 315 are identified in the
message
request by a unique, though preferably descriptive alpha-numeric address,
rather than
an MSN. For example, if the host computer 305 is a billing computer for a
utility
company, such as an electric power company, and the mobile stations 310 and
315 are
electric company meters, the host computer 305 might employ descriptive alpha-
numeric addresses such as METER00310 and METER00315 to uniquely identify the
mobile stations 310 and 315. However, one skilled in the art will recognize
that any
unique sequence, such as a unique binary sequence, or a unique sequence of
recognizable characters and/or symbols may be used to compose a mobile station
address.
Next, the SMS-C 320 receives the message request, and with the aid of a
database 325 or a lookup table (not shown), the SMS-C 320 translates the one
or more
descriptive mobile station alpha-numeric addresses. In a preferred embodiment
of the
present invention, the SMS-C 320 and the database 325 translate each mobile
station
address into a PRN and an IMSI, wherein the PRN is a network address for the
VMSC
controlling the service area in which the intended mobile station is located.
In order
for a message to reach the intended mobile station, each mobile station has a
unique
combination of PRN and IMSI.
It is not necessary, however, that each mobile station in the network
have a unique IMSI. As is well-known in the art, a service area under the
control of a
single VMSC might include several paging areas. Accordingly, in an alternative
embodiment of the present invention, each paging area is assigned a unique
PRN, so
that two mobile stations located in different paging areas (i.e., different
paging areas
associated with one MSC/VMSC or different paging areas associated with
different
MSCs/VMSCs) could share the same IMSI, thereby conserving the number of
available
IMSI codes, as well as MSNs.
In yet another alternative embodiment, the SMS-C 320 and the database
325 may translate the descriptive address of a mobile station into a pursuit
routing
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address, an IMSI, and an MSN. As one of the primary purposes of the present
invention is to conserve the limited supply of MSNs, all of the mobile
stations in the
network being employed for a particular static application could share the
same MSN
value.
It is important to note, that in each of the embodiments of the present
invention described above, the MSN, by itself, is not relied upon to uniquely
identify
the intended mobile station. In addition, there is no need to interrogate the
network
HLR to obtain the intended mobile station's network location. As explained
above, this
information is more conveniently stored in the database 325 associated with
the SMS-C
320. Therefore, aside from conserving the number of MSNs and, if desired, the
number IMSIs assigned to the various subscribers and mobile stations, the
present
invention also reduces the workload on the network HLR, thereby increasing the
efficiency of the network and decreasing message delivery latency rates.
Once the SMS-C 320 and the database 325 have translated the
descriptive alpha-numeric address of each intended mobile station into a
unique
combination of PRN and IMSI, the SMS-C 320 submits (2) a short message packet
using the ISUP signalling protocol to the switching network through an IW/G-
MSC
330. The IW/G-MSC 330 routes (3) the short message packet to the appropriate
VMSC, for example, VMSC 335, in accordance with the PRN. The VMSC 335 then
locates the intended mobile station within its service area utilizing the
IMSI, for
example mobile station 315. The VMSC 335 then sends (4) the message packet to
the
mobile station 315 through a base station 345. The mobile station 315 then
unpacks the
message packet and extracts the short message sent by the host computer 305.
In an alternative embodiment, the host computer 305 contains the
database or lookup table to translate a descriptive mobile station alpha-
numeric address
into a PRN and an IMSI. The host computer 305 then submits (1) the message,
along
with the PRN and the IMSI, to the SMS 320. In this alternative embodiment, the
SMS
320 primarily handles the messaging protocols that are required for
interfacing with the
mobile network. The advantage of this embodiment is that the task of
translating the
descriptive mobile station alpha-numeric address into a PRN and an IMSI is
performed
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in a node that is less likely to be affected by a non-real time task. In
addition,
maintaining the database or lookup table in the host computer 305 provides
added
security and helps to preserve customer confidentiality
FIG. 4 illustrates how, in the GSM system, a host computer 405 may
interrogate a mobile station, for example mobile station 410, using a SMS as a
message
bearer, in accordance with the present invention, wherein the mobile station
410 is
employed in a static application such as a telemetry application or a remote
programming application. In accordance with FIG. 4, the host computer 405
submits
(1) a mobile terminated short message (MT-SM) to a short message SC 415. The
MT-
SM includes an identification code other than the MSISDN for the mobile
station 410.
As in the PDC system described above, the identification code may be
descriptive in
nature, and preferably alpha-numeric, although any unique sequence, such as a
binary
sequence or a sequence of recognizable characters and/or symbols may be
utilized.
Then, in a manner similar to the SMS-C 320 in FIG. 3, the SC 415 translates
the
identification code into an IMSI corresponding to the mobile station 410 and a
VMSC-
ID, wherein the VMSC-ID is an E. 164 address corresponding to the MSC service
area
in which the mobile station 410 is located. The SC 415 transmits (2) the MT-SM
into
the switching network via a gateway MSC (GMSC) 420. The GMSC 420 then routes
(3) the MT-SM to the VMSC 425 controlling the MSC service area in which the
mobile
station 410 is located. The VMSC 425 then transmits (4) the MT-SM to the
mobile
station 410 through the appropriate base station controller 430 and the base
station
transmitter 435.
In accordance with this embodiment of the present invention, a SRIFSM
instruction need not be sent to the HLR to locate the mobile station 410.
Hence, the
workload on the network HLR is again reduced. Moreover, the unique combination
of
a VMSC-ID and IMSI is used to identify the MSC service area and the mobile
station
410, respectively, not an MSISDN. Therefore, the utilization of an MSISDN can
be
avoided, thereby conserving the limited number of available MSISDNs. In
another
aspect of the present invention, the same MSISDN is assigned to each and every
mobile
station being employed for a particular static application, for use by various
network
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services and applications, wherein each mobile station is still identified by
a unique
combination of VMSC-ID and IMSI.
In still another aspect of the present invention, each paging area within a
single MSC
service area may be identified by a unique MSC-ID number. In accordance with
this aspect of
the present invention, two or more mobile station may share the same IMSI, as
long as they
are located in different paging areas. Likewise, two or more mobile stations
may share the
same IMSI if they are located in different MSC service areas. This aspect of
the present
invention reduces the number of required IMSIs, as well as the required number
of MSISDNs.
As one skilled in the art will readily appreciated, the mobile station 410 can
also
initiate a message, for example, in response to a message sent by the host
computer 405. In
accordance with present GSM standards, the mobile station 410 inserts its
MSISDN into the
mobile originated short message (MO-SM) as an originator address. However, as
stated above,
each mobile station being employed for the same application can be assigned
the same
MSISDN. The host computer 405 would then distinguish MO-SMs by the IMSI and or
the
unique combination of VMSC-ID and IMSI.
In an alternative embodiment, the host computer 405 translates the
identification code
into a VMSC-ID and an IMSL The host computer 405 then submits (1) the MT-SM to
the SC
415, wherein the MT-SM already includes the VMSC-ID and the IMSI. In this
alternative
embodiment, the SC 415 still handles the messaging protocols required for
interfacing with the
mobile network. The advantage of this embodiment is that the task of
translating the
identification code into a VMSC-ID and an IMSI is performed by a node (i.e.,
the host
computer 405) that is less likely to be affected by a non-real time task. As
stated above,
maintaining the database or lookup table in the host computer provides added
security and
helps to preserve customer confidentiality.
As stated above, U.S Granted Patent 5,752,188 describes how the GSM system
permits
an external node 505 to communicate with a mobile station 510 using an USSD
signalling
protocol. In view of
Amended Sheet
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this, FIG. 5 illustrates yet another alternative embodiment of the present
invention. In
accordance with this embodiment, the external node (e.g., a host computer)
generates a
message, or a text string, which already includes the VMSC-ID and the IMSI
needed to
uniquely identify the mobile station 510. It was also explained above that
USSD
typically interfaces directly with a network HLR 515 or a VMSC 520 which
controls
the service area in which the mobile station 510 is located. Even though the
external
node might interface with the HLR 515, there is no need to access the
subscriber record
in the HLR 515 to obtain the information needed to send the message to the
mobile
station 510, because the external node 505 already provides the VMSC-ID and
the
IMSI. In addition, the external node 505 may interface with the network
through a
gateway MSC 525. Accordingly, FIG. 5 depicts the gateway MSC 525 as a dashed
line. Alternatively, the host computer may be part of the network. In
accordance with
this alternative, the host computer would be able to transmit a message
directly without
having to interface with a GMSC or a HLR. Therefore, whether SMS or USSD is
used
as a message bearer, the number of MSISDNs assigned to mobile stations
employed for
static applications can be reduced and/or avoided all together by relying on
the IMSI or
unique combination of VMSC-ID and IMSI to identify each mobile station.
As mentioned throughout the preceding discussion, the various
embodiments of the present invention provide a number of advantages. First, by
relying on the IMSI or a unique combination of the PRN/MSC-ID and the IMSI for
each mobile station within the switching network, the number of MSNs, in the
PDC
system, and the number of MSISDNs, in the GSM system, allocated to mobile
stations
employed for static applications can be reduced. Second, the number of IMSIs
allocated to mobile stations can be reduced by ensuring that no two mobile
stations
sharing the same IMSI are located in the same paging area. Third, by avoiding
the
necessity to interrogate the network HLR to obtain location information, the
workload
of the network HLR is reduced, thereby increasing the efficiency of the
network and
reducing message delivery latency rates.
The present invention has been described with reference to several
exemplary embodiments. However, it will be readily apparent to those skilled
in the
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art that it is possible to embody the invention in specific forms other than
those of the
exemplary embodiments described above, without departing from the spirit of
the
invention. These exemplary embodiments are merely illustrative and should not
be
considered restrictive in any way. The scope of the invention is given by the
appended
claims, rather than the preceding description, and all variations and
equivalents which
fall within the range of the claims are intended to be embraced therein.
