Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02353626 2001-06-04
c . ,
-1-
SYSTEM AND METHOD FOR MOBILE TERMINAL REGISTRATION IN
AN INTEGRATED WIRELESS PACKET-SWITCHED NETWORK
PRIORITY STATEMENT UNDER 35 U.S.C ~119(e) & 37 C.F.R. ~1.7$
This nonprovisional application claims prioritybased upon the following prior
U.S. provisional patent application entitled: "System and Method for Providing
Mobile Stations in a Radio Telecommunications Network with Multimedia Services
over Packet-Based Networks," Ser. No. 601110,811 (Attorney Docket Number 1000-
0136), filed December 3, 1998, in the names of Hung Tran, Kim Vo, Bartosz
Balazinski, Jean-Francois Bertrand, Laura Hernandez, and Suhail Hasan.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application discloses subject matterrelated to the subject
matterdisclosed
in the following co-assigned patent applications: (1) "System and Method for
Providing Wireless Telephony over a Packet-Switched Network," filed October
26,
1999, Ser. No. 091427,508 (Attorney Docket Number 1000-0144), in the names of
Kim Vo, George Foti, Hung Tran, Jean-Francois Bertrand, Bartosz Balazinski,
Francis
Lupien, Zeng-Jun Xiang, and Yang Lu; (2) "System and Method for Providing
Mobile
Switching and Multi-Party Services over a Packet-Switched Network," filed
October
26,1999, Ser. No.09/426,513 (Attorney Docket Number 1000-0155), in the names
of
Hung Tran, Bartosz Balazinski, Jean-Francois Bertrand, and Laura Hernandez;
(3)
"System and Method for Improved Resource Management in an Integrated
Telecommunications Network Having a Packet-Switched Network Portion and a
Circuit-Switched Network Portion," filed October 26, 1999, Ser. No. 09/427,347
(Attorney Docket Number 1000-0156), in the names of Akilan Tiburtius and Roch
Glitho.
BACKGROUND OF THE INVENTION
Technical Field of the Invention
The present invention relates to telecommunication systems and, more
AMENDED SHEET
CA 02353626 2001-06-04
WO 00!33523 PCT/SE99I02165
-2-
particularly, to a system and method for registering mobile terminals, or
stations, in
an integrated wireless packet-switched network such as, for example, a network
using
the Internet Protocol (IP).
Description of Related Art
Coupled with the phenomenal growth in popularity of the Internet, there has
been a tremendous interest in using packet-switched network (PSN)
infrastructures
(e.g., those based on IP addressing) as a replacement for the existing circuit-
switched
network (CSN) infrastructures used in today's telephony. From the network
operators'
perspective, the inherent traffic aggregation in packet-switched
infrastructures allows
for a reduction in the cost of transmission and the infrastructure cost per
end-user.
Ultimately, such cost reductions enable the network operators to pass on the
concomitant cost savings to the end-users. Further, because the need for
establishing
long distance trunks is eliminated in a PSN, one of the most attractive
features of IP-
based telephony networks is that charges or tolls for long distance calls,
which may be
I S quite expensive in a CSN, may be advantageously avoided.
TP-based networks designed for providing audio, video, and data
communications on a unified foundation are commonly referred to as "Voice-over-
IP"
(VoIP) networks. Several competing standards or protocols exist today that
govern
the overall operation, control and service management relating to such V oIP
networks.
Someofthesestandardsare:theH.323RecommendationprovidedbytheInternational
Telecommunications Union (ITU), Session Initiation Protocol (SIP) or Internet
Protocol Device Control (IPDC) by the Internet Engineering Task Force (IETF),
or the
Simple Gateway Control Protocol (SGCP).
in order to be interoperable with the extant Public Switched Telephone
Network (PSTN), current VoIP networks implement communications infrastructures
that are primarily oriented to operating with fixed-network-based
telecommunications
protocols. Consequently, the VoIP protocols designed to accommodate such
services
as call control, et cetera, for wireline subscribers cannot be used
advantageously in
wireless environments.
Although some VoIP infrastructures may support rudimentary location
management services, one ofthe more nettlesome problems with respect to
integrating
CA 02353626 2001-06-04
WO 00133523 PCT/SE99/02165
-3-
current VoIP networks and harnessing their full potential within the context
of a
wireless telecommunications network stems from the mobility of cellular
subscribers.
For example, one of the critical entities defined by the well-known H.323
standard,
called a gatekeeper, which provides, among other things, for call routing
services and
S the registration of other H.323-compatible entities within a network, is
typically
unaware of conventional telecommunications terminals. While this condition is
not
a problem for fixed wireline telephones in terms ofproviding savings in long
distance
charges, calls involving mobile subscribers may still require establishing
long distance
trunks from one Mobile Switching Center (MSC) to another. Clearly, those of
ordinary skill in the art should readily appreciate that such a result
eradicates one of
the primary motivations behind an IP-based telephony network in the first
place.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a system and method for
1 S - providing a dual registration scheme for a mobile terminal using an
H.323-compatible
entity, hereinafter denoted as an H.323 mobility server, provided within a
wireless
VoIP network. The H.323 mobility server, which in some respects operates as a
gatekeeper in accordance with the teachings of the present invention, obviates
the need
for establishing inter-MSC trunks.
In one aspect, the present invention is directed to a method of registering
and
unregistering a mobile terminal in an integrated wireless packet-switched
network
system. The integrated wireless packet-switched network system includes a
cellular
network portion and a packet-switched network portion, wherein the cellular
network
portion comprises a serving Mobile Switching Center (MSC), a Visitor Location
2S Register (VLR), and a Home Location Register (HLR). The VLR and the MSC
form
a serving system for the mobile terminal. The packet-switched network portion
preferably comprises a mobility server and a gateway. The method starts by
detecting,
in the serving system, the mobile terminal located in a service area
associated with the
serving system. The mobile terminal is then registered in the cellular network
portion:
.~
Subsequently, the mobile terminal is also registered in the mobility server of
the
packet-switched network portion. If the serving system detects that the mobile
CA 02353626 2001-06-04
J
WO 00133523 PCT/SE99/02165
-4-
terminal is either being powered down or no longer located in the serving
area, the
process of unregistering the mobile terminal in the cellular network portion
and in the
mobility server of the packet-switched network portion is commenced.
In another aspect, the present invention is directed to an integrated wireless
telecommunications network having a cellular network portion and a packet-
switched
network portion. A gateway is disposed between the cellular and packet-
switched
network portions for providing a communication pathway therebetween. The
cellular
network portion includes means for registering a mobile terminal in a serving
system.
Tin addition, the packet-switched network portion includes means for
registering the
mobile terniinal, responsive to an indication provided by the serving system
via the
gateway.
In yet another aspect, the present invention's integrated wireless
telecommunications network comprises a serving system serving a mobile
terminal
located in its serving area. A gateway is coupled to the serving system, the
gateway
providing a communications pathway between the cellular and packet-switched
network (PSN) portions. A mobility server is disposed in the PSN for
registering the
mobile terminal, the mobility server having means for maintaining location
information with respect to a registered mobile terminal. The serving system
includes
means for sending a private registration message to the gateway to indicate a
registration update with respect to the mobile terminal. The gateway includes
means
for translating the private registration message into a message compatible
with the
mobility server and for forwarding the translated message thereto. In mother
exemplary embodiment, the mobility server may be provided with an interface
for
interpreting or supporting the private registration message provided by the
serving
system. In that case, the gateway does not have to translate the private
registration
message on behalf ofthe mobility server, and simply forwards the message
thereto.
In a further aspect, the present invention is directed to a method of keeping
track of a mobile terminal in an integrated telecommunications network which
includes a cellular network portion and an H.323-based PSN portion. The
cellular
network portion comprises a serving system for the mobile terminal, which
includes
a serving MSC and a VLR. The PSN portion includes a gateway that is coupled to
the
CA 02353626 2001-06-04
j
WO 00/33523 PC'T/SE991021b5
-5-
serving MSC. The method provides a mobility server in the H.323-based PSN
portion,
wherein the mobility server contains a registration database. Upan detecting,
in the
serving system, that the mobile terminal is located in a serving area
associated with the
serving system, the claimed method registers the mobile terminal in the
mobility server
~ of the PSN portion.
In a still further aspect, the present invention is directed to a call routing
method for routing an in-coming call towards a mobile terminal disposed in an
integrated telecommunications network such as the network set forth above.
After
providing a mobility server for registering the mobile terminal in the PSN
portion of
the network, the in-coming call is received in a receiving system. The
receiving
system then queries the mobility server for locating the mobile terminal.
Responsive
to the querying step, the mobility server returns an address (e.g., an IP
address) of the
gateway that is associated with the serving system of the mobile terminal, to
the
receiving system. Thereafter, the in-coming call is routed by the network to
the mobile
15' terminal based on the address of the gateway.
BRIEF DESCRIPTION OF TAE DRAWINGS
A more complete understanding of the present invention may be had by
reference to the following Detailed Description when taken in conjunction with
the
accompanying drawings wherein:
FIGS. lA and 1B depict functional block diagrams of an exemplary
embodiment of a registration method for a mobile terminal disposed in an
integrated
wireless IP (WLIP) network provided in accordance with the teachings of the
present
invention;
FIGS. 2A and 2B depict functional block diagrams of an exemplary
embodiment of an unregistration method for a mobile terminal in accordance
with the
teachings of the present invention; and
FIGS. 3 and 4 illustrate control messagepathways for implementing apresently
preferred exemplary embodiment of a call setup method usable in the WLIP
network
of the present invention.
CA 02353626 2001-06-04
WO 00/33523 PCT/SE99/02165
-6-
DETAILED DESCRIPTION OF EMBODIMENTS
Since the process of mobile terminal registration is discussed within the
context of a H.323-based network, a brief description of the H.323 call
routing process
is provided below.
The H.323 protocol, developed originally to provide multimedia
communications services over a packet-based network, presently allows PSTN
subscribers to communicate with packet-based network users and vice versa.
Three
entities are of particular relevance in this context: (a) a gateway which
permits the
interconnection between the packet-based network and the PSTN; (b) a
gatekeeper
used for the routing of the H.323-based calls; and (c) a terminal which
provides the
users of a packet-based network (e.g., Internet) a device similar to a regular
telephone.
The H.323 protocol allows multiple types of addresses for each user. For
example, the following address types are common: (a) an H.323 Alias,
corresponding
to a symbolic name given to a particular H.323 terminal; (b) a transport
address,
15- corresponding to the IP address of the host where the H.323 terminal is
located; and
(c) an E.164 number, which is simply a phone number associated with the H.323
terminal. In accordance with the H.323 standard, the gatekeeper supervises all
the
calls delivered through the IP network, and as part of its functionality, it
facilitates the
matching of the terminal's E.164 number with the IP address of the host where
the
terminal is located. Because the IP addresses are necessary for establishing
communication between different hosts on the IP network, all H.323 terminals
are
required to register with the gatekeeper in order to place and receive calls
using their
E.ld4 numbers.
The H.323 gateway connects a telephone switching center (for example, the
PSTN switching center or a cellular switching center) to the IP network. From
the
perspective of the H.323 IP network, the H.323 GW preferably covers all the
telephone
numbers which start with a particular E.164 prefix, and accordingly, when the
H.323
GW is registered at the H.323 gatekeeper with its E.164 prefix, the gatekeeper
routes
calls with that E.164 prefix towards the appropriate telephone switching
center. It
should be noted that, typically, both an H.323 terminal and the H.323 GW
register or
unregister at the gatekeeper when they are powered up or down, respectively.
CA 02353626 2001-06-04
!?VO 00/33523 PCT/SE99/02165
_'7_
In the state-of the-art VoIP implementations provided for landline telephone
connectivity, individual PSTN subscribers cannot, and are not, required to
register
their terminals at the H.323 gatekeeper. That this is not a problem in the
context of
a fixed landline telephone network should be readily apparent, because as is
well-
s known, the PSTN terminals are typically always accessed through a unique
switching
center. However, in the context of a cellular telecommunications network, the
subj ect
matter of the present invention, it can be appreciated that the mobility of
mobile
subscribers from one Mobile Switching Center (MSC) to another poses a
significant
problem. With the current E.164 prefix routing scheme, when a mobile
subscriber
roams to another MSC, the calls have to go through the mobile subscriber's
home
H.323 gateway and then through the home MS C associated with the mobile
subscriber.
From there, trunks have to be seized to the serving MSC where the mobile
subscriber
is visiting. Accordingly, as set forth in the Background section of the
present patent
application, the requirement of establishing inter-MSC trunks defeats the
fundamental
1 S purpose of using and integrating the IP network in cellular environments.
Referring now to FIGS. lA and 1B, shown therein is a presently preferred
exemplary embodiment of an integrated wireless telecommunications network 102,
preferably using IP ("wireless IP" or WLIP), for facilitating the dual
registration
scheme provided in accordance with the teachings of the present invention. It
should
be understood by those of ordinary skill in the art that only relevant
components of a
cellular network portion and a VoiP network portion are depicted herein for
illustrative
clarity. Accordingly, the WLIP network 102 may include other entities such as,
for
example, H.323 terminals, a Multipoint Controller Unit (MCU), and additional
gateways and gatekeepers.
When a mobile terminal, e.g., MT 112, is powered up and detected (as
illustrated by path 312) in the serving area of a serving MSC 302, the serving
MSC
302 proceeds with the MT's registration in a Home Location Register (HLR) 298
in
a conventional manner via standard ANSI-41 signaling mechanisms (via path
314).
Also, the MT 112 is registered at a Visitor Location Register (VI,R) 304
associated
with the serving MSC 302. As is well-known, the serving MSC 302 and its
associated
VLR 304 together form the MT's serving system.
CA 02353626 2001-06-04
J
WO 00/33523 PCT/SE99/02165
_g_
Once the registration process with the cellular network infrastructure is
completed, the serving MSC then initiates the registration of the MT with
respect to
the VoIP network 108. An ANSI-41 private message is provided in accordance
herewith for the purpose of IP-network registration. The ANSI-41 private
message for
IP-network registration, including a parameter called RegUpdate, is
transmitted by the
serving MSC 302 via path 310 to an H.323 GW 116 associated therewith. The
RegUpdate parameter preferably contains the MT's registration information.
Upon receiving the ANSI-41 private message, the GW 1 i6 translates the
information therein into an H.323 Registration Access and Status (RAS) message
called Registration Request (RRQ), which is transmitted via path 308 to a
H.323
mobility server 306. The RegUpdate parameter contained in the RAS RRQ message
is used by the mobility server 306 for the purpose of the MT's registration in
a
database associated therewith. Upon successful registration at the mobility
server 306,
a Registration Confirm {RAS RCF) message is returned to the GW 116. On the
other
i 5 hand, if the registration at the mobility server 306 was unsuccessful, a
Registration
Reject (RAS RR,~ message is returned. The return message path from the
mobility
server 306 is labeled with reference numeral 318 in FIG. 1B. Consequently,
upon
receiving the return message from the mobility server 306, the GW l I6 sends
an
ANSI-41 return message via path 316, which includes a RegUpdate Return Result,
to
the serving MSC 302. It should be understood that the RegUpdate Return Result
contains an appropriate parameter corresponding to the H.323 answer (i:e., the
RCF
or RRJ message).
FIGS. 2A and 2B depict a presently preferred exemplary embodiment of an
unregistration process for a mobile terminal that is registered at the
mobility server 306
in accordance herewith. When the MT 112 is powered down or detected to be
moving
out of the serving area of the serving MSC 302, standard ANSI-41 signaling is
used
via path 404 for informing the HLR 298 about the MT's unregistration at the
cellular
infrastructures. Similarly, the VLR 304 may be conventionally notified of the
MT's
location update information. Once again, the unregistration process at the IP-
network
. .~
108 is facilitated by sending an ANSI-41 private message containing the
RegUpdate
parameter from the MSC 302 to the GW 116. The message path 406 in FIG. 2A
CA 02353626 2001-06-04
CVO 00133523 PCT/SE99/02165
-9-
illustrates this ANSI-4I private message for unregistration.
Upon receiving the ANSI-41 private message for unregistration, the GW 116
may translate the information therein into a suitable H.323 RAS Unregistration
Request (RAS URQ) message which is sent via path 408 to the mobility server
306.
In a manner similar to the registration process described above, the mobility
server 306
processes the parametric information appropriately and updates its location
database/directory, if necessary (i.e., the entry relating to the departing MT
is deleted).
Thereafter, it sends an appropriate return message, either a RAS
Unregistration
Confirm (RAS UCF) or a RAS Unregistration Reject (RAS UR.J~, to the GW I 16. A
suitable ANSI-41 response message is then forwarded from the GW 116 to the
serving
MSC 302. In FIG. 1B, these return/response messages are labeled as paths 410
and
412, respectively.
In the presently preferred exemplary embodiment, the RegUpdate parameter
in the ANSI-4I private message for dual registration comprises a 50-octet
structure.
1 S ~ The encoding of some of the relevant octets is provided as follows.
Octets I and 2 are
used for the sending individual's information. Octets 9-14 encode the MT's
E.164
number. Electronic Serial Number (ESN) of the MT is encoded in octets 15-18.
The
Location Area Code values are provided in octets 19-20. Registration Type and
Capability Report Indicator values are encoded in octets 43-44.
The RegUpdate Return Result parameter is presently provided as a 10-octet
structure. Octets 7-8 are encoded with the registration result, and octets 9
and 10 are
encoded with Capability Report Status information.
It is contemplated herein that the translation of the ANSI-41 private messages
into RASmessages maybe provided as optional, ifthe mobility server 306 is
supported
with an ANSI-41 interface. In that case, there is no need for the translated
RRQlRCFlRRJand URQ/UCF/URJmessages between the GW 116 and the mobility
server 306. Instead, the GW 116 may simply forward the ANSI-41 private
messages
to the mobility server 306 for registration/unregistration.
As explained in the foregoing, in accordance v~ith teachings herein, the
mobility server 306 preferably acts as a H.323 gatekeeper or as a location
server within
the IP network 108. Accordingly, when a particular gatekeeper in the IP
network 108
CA 02353626 2001-06-04
WO 00/33523 PCT/SE99/02165
-10-
does not know the called party's location (that is, its database does not have
a E.164
transport address translation for the called number), it inquires through
suitable
H.225 messages (namely, theLocation Request, Location Confirm andLocation
Reject
(LRQlLCFlLRJ} messages) sent to its neighborhood gatekeepers and the mobility
S server 306 about the location of the called party. The mobility server 306
then
responds with the transport address of the GW in its LCF return message.
Preferably,
the database of the mobility server may keep track of multiple registrations
of mobile
terminals in a manner similar to the location registration process of a VLR.
In
addition, the mobility server's database preferably uses the E.164 number as a
key for
its internal database or location directory purposes.
Based on the foregoing, it can be realized that by registering at the mobility
server in accordance herewith, the need for establishing inter-MSC trunks when
the
MT is roaming outside its home location is obviated because the mobility
server
updates its location directory with the corresponding gateway's address when
the MT
moves into a new serving area. Accordingly; no long distance toll charges may
be
necessary by ensuring that the call is transported over the IP network
portion.
Referring now to FIGS. 3 and 4, depicted therein are control message pathways
for implementing a call setup method for an MT that is registered at the
mobility
server 306 in accordance herewith. More particularly, FIG. 3 depicts a control
message pathway for a call scenario wherein the call is originated by an MT
112.
When a call intended for an H.323 terminal 284 is initiated by the MT 1 I2
(path 508),
the serving MSC 302 sends an appropriate ANSI-41 or a Primary Rate Interface
(PRI)
setup message 510 to the GW 116. In response thereto, the GW 116 sends an
Admission Request (ARQ) message 512 to the H.323 gatekeeper 278. An LRQ
message 514 is generated by the gatekeeper in order to query the mobility
server 306
for the address of the H.323 terminal 284. Subsequently, an LCF message 516,
is
returned from the mobility server 306 with the appropriate location
information to the
gatekeeper 278, which then sends its own Admission Conf rm (ACF) message S 18
to
the GW 116. A Q.931 interface 520 is then set up between the GW 116 and the
H.323
terminal 284 which in turn negotiates for Admission Request with the
gatekeeper 278
via path 522. After a location inquiry process (also referred to as "Endpoint
CA 02353626 2001-06-04
WO 00/33523 PCT/SE99/02165
-11-
Location's similar to the process described above, the H.323 terminal 284
receives an
ACF return message 528 from the gatekeeper 278. Thereafter, a call path 530
from
the MT 112 to the terminal 284 is established such that the call can proceed
therefrom.
FIG. 4 illustrates the call scenario wherein the MT 112 is the called party
and
the H.323 terminal 284 is the caller. It should be apparent that the control
messages
shown herein are similar to those illustrated in the description set forth
above.
Analogous to the situation where the MT is the caller, the mobility -server
306 is
engaged in a two-stage inquiry process, first with the gatekeeper 278 (upon
call
origination) and then with the GW 116 (for cellular connectivity). Once the
ANSI-41
or PRI setup is effectuated between the GW 116 and the MT 112 via the serving
MSC
302, the call path 624 is established between the parties.
Although the system and method ofthe present invention have been described
in particular reference to the H.323 protocol and ANSI-41 standards, it should
be
realized upon reference hereto that the innovative teachings contained herein
are not
necessarily limited thereto and may be implemented advantageously with any
applicable packet-switching protocols and radio telecommunications standards.
Further, it is believed that the operation and construction of the various
aspects
of the present invention will be apparent from the foregoing description.
While the
methods and systems shown and described~have been characterized as being
preferred,
it will be readily apparent that various changes and modifications could be
made
therein without departing from the scope of the present invention as set forth
in the
following claims.
