Virtual visitor location register for a wireless local area network

A multi-mode mobile station is able to wirelessly communicate with a wireless wide area network (WWAN) and with a wireless local area network (WLAN). The WLAN includes a “virtual” visitor location register (VVLR) for storing information about multi-mode mobile stations being served by the WLAN. The VVLR communicates with a home location register (HLR) in the WWAN in order to facilitate roaming between the WWAN and WLAN by the multi-mode mobile station.

BACKGROUND

1. Field of the Invention

The present invention relates to telecommunications and, more particularly, to a “virtual” visitor location register for a wireless local area network.

2. Description of Related Art

A traditional enterprise telephone network includes a number of landline extension telephones (either analog or digital) connected to a private branch exchange (PBX). The PBX, in turn, is connected to the public switched telephone network (PSTN), e.g., via a primary rate interface or a basic rate interface. Increasingly, however, more diverse types of communication devices are being used in enterprise networks. For example, the PBX may be connected via a local area network (LAN) to packet-based communication devices, such as voice-over-packet (VoP) telephones or audio-equipped personal computers. In addition, the PBX may be an “IP-PBX” communicatively coupled to a packet-switched network, such as the Internet, instead of or in addition to the PSTN.

The PBX may also be part of a wireless local area network (WLAN) that includes one or more wireless access points for communicating with mobile stations over air interfaces. Such mobile stations may include wireless telephones, wirelessly-equipped personal digital assistants (PDAs), wirelessly-equipped laptop computers, and/or other wireless communication devices. The air interface communications may conform to a WLAN specification, such as IEEE 802.11b, Bluetooth, HomeRF, or HiperLAN. Alternatively, or additionally, the air interface communication may occur in a cordless telephone format, in a Multichannel Multipoint Distribution Service (MMDS) format, or in some other format. Some of these mobile stations may also be able to communicate with a wireless wide area network (WWAN), using an air interface format such as CDMA or GSM. Thus, when a multi-mode mobile station is within the wireless coverage area of the WLAN, it may use the WLAN for communication, and when the multi-mode mobile station is within the wireless coverage of the WWAN, it may use the WWAN for communication.

WWAN signaling protocols, such as IS-41, typically support roaming between areas served by different serving systems. For example, each serving system in a WWAN may include a visitor location register (VLR) that communicates with a home location register (HLR) for mobility management and other purposes. Now, with the interest in multi-mode mobile stations that may be in communication with either a WWAN or a WLAN at any given time, there is a need to provide additional systems and methods for mobility management in order to facilitate roaming between the WWAN and WLAN. For example, it is desirable to be able to reach a multi-mode mobile station by dialing the same directory number, regardless of whether the multi-mode mobile station is in communication with the WWAN or with the WLAN.

SUMMARY

In a first principal aspect, an exemplary embodiment of the present invention provides a wireless local area network (WLAN) for providing wireless telecommunications services to a multi-mode mobile station. The multi-mode mobile station is able to wirelessly communicate with a wireless wide area network (WWAN) when operating in a first wireless coverage area. The WWAN includes a first data register that contains a first data record for the multi-mode mobile station. The WLAN comprises at least one wireless access point, a private branch exchange (PBX) communicatively coupled to the at least one wireless access point, and a second data register communicatively coupled to the PBX and to the first data register. The at least one wireless access point provides a second wireless coverage area, within which the multi-mode mobile station is able to wirelessly communicate with the at least one wireless access point. The second data register is able to transmit at least one mobility management message to the first data register. The at least one mobility management message facilitates roaming between the first and second wireless coverage areas by the multi-mode mobile station.

In a second principal aspect, an exemplary embodiment of the present invention provides a method of mobility management of a multi-mode mobile station that is able to wirelessly communicate with a wireless wide area network (WWAN) and with a wireless local area network (WLAN). In accordance with the method, the multi-mode mobile station associates with a wireless access point of the WLAN. The WLAN includes a private branch exchange (PBX). The PBX stores information regarding the multi-mode mobile station in a WLAN data register. The WLAN data register sends a registration message to a WWAN data register in a WWAN. The registration message identifies the multi-mode mobile station.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present invention, in exemplary embodiments, facilitates the roaming of multi-mode mobile stations between a wireless wide area network (WWAN) and a wireless local area network (WLAN). In an exemplary embodiment, a multi-mode mobile station may be reached by dialing the same directory number, regardless of whether the multi-mode mobile station is in communication with the WWAN or with the WLAN. A PBX of the WLAN is provided with a data register that keeps track of which multi-mode mobile stations are registered for services with the PBX. For convenience, this data register is referred to herein as a “virtual” visitor location register (VVLR), though it is to be understood that a VVLR need not perform all of the same functions or engage in the same signaling as a VLR would in a WWAN.

As used herein, a “WLAN” refers to a local area network that includes at least one wireless access point. Thus, in a WLAN, some devices may communicate wirelessly, but other devices may communicate over wired communications. As used herein, a “PBX” refers to a system that controls telephony services in the WLAN. Preferably, the PBX is an “IP-PBX” communicatively coupled to a packet-switched network. Alternatively or additionally, the PBX may be connected to the PSTN, e.g., via a primary rate interface or a basic rate interface. The PBX may be directly connected to the WLAN. Alternatively, the PBX could be communicatively coupled to the WLAN so as to control telephony services in the WLAN remotely. In addition, the PBX could be provided as a single device or as a distributed system. Thus, the PBX could be a hosted PBX or an IP-Centrex system, for example. The VVLR may be integrated with or otherwise accessible by the PBX.

The VVLR for the WLAN communicates with a home location register (HLR) for the WWAN in order to help manage the mobility of multi-mode mobile stations. In an exemplary embodiment, the communications between the VVLR and the HLR may conform to a WWAN signaling protocol, such as IS-41. However, other signaling protocols, such as SIP, SIP-T, or H.323 could be used. In addition, the VVLR may communicate using one protocol, such as SIP, and the HLR may communicate in another protocol, such as IS-41, with a signaling gateway converting between the two protocols. Such conversion may involve encapsulation/de-encapsulation, e.g., of IS-41 messages in SIP or SIP-T messages. Alternatively or additionally, the conversion may involve translation, i.e., mapping between message types and/or parameters.

In the example where the VVLR and HLR both communicate using IS-41, the VVLR may send an IS-41 Registration Notification (REGNOT) message to the HLR when a multi-mode mobile station registers for services in the WLAN. In this way, the HLR is notified that the multi-mode mobile station is an area being served by the VVLR. Then, when a call is placed to a directory number associated with the multi-mode mobile station, the HLR may send an IS-41 Routing Request (ROUTEREQ) message to the VVLR to obtain routing information that can be used to route the call to the multi-mode mobile station. The routing information could be a directory number assigned to the PBX, in which case the call may be routed to the PBX via the PSTN. Alternatively, the routing information could result in the call being routed to the PBX via a packet-switched network. In particular, the routing information could be a directory number assigned to a media gateway communicatively coupled to the PBX via a packet-switched network, or the routing information could be an Internet Protocol (IP) address of the PBX or of the multi-mode mobile station. Other types of routing information could also be used.

In addition to REGNOT and ROUTEREQ messages, the VVLR and HLR could exchange other messages, for mobility management purposes or for other purposes. The VVLR may also store a data record for each multi-mode mobile station being served by the WLAN. The data record may include a service profile that the VVLR obtained from the HLR, e.g., in response to a REGNOT message. In this way, the services available to the multi-mode mobile station when served by the WWAN may also be available to the multi-mode mobile station when served by the WLAN.

1. EXEMPLARY NETWORK ARCHITECTURE

FIG. 1is a simplified block diagram of an exemplary wireless telecommunications system10. InFIG. 1, connections that carry voice or other media are shown as solid lines and connections that carry primarily signaling are shown as dashed lines.

Wireless telecommunications system10includes network elements that function together as a wireless wide area network (WWAN)12and network elements that function together as a wireless local area network (WLAN)14. WWAN12may provide wireless coverage in a relatively large geographic area, such as an entire city, often by using a plurality of contiguous wireless coverage areas, such as cells or sectors. The wireless communication in WWAN12may occur in an analog format, such as the Advanced Mobile Phone Service (AMPS), or in a digital format, such as code division multiple access (CDMA), time division multiple access (TDMA), or Global System for Mobile communication (GSM). The wireless communication may occur in licensed frequency bands, such as the 1.9 GHz PCS bands. WLAN14may provide wireless coverage in a relatively limited area, as compared to WWAN12, such as in a building or part of a building. In addition, WLAN may use one or more unlicensed frequency bands, such as the unlicensed frequency band in the 2.4 GHz range.

A multi-mode mobile station16is able to wirelessly communicate with WWAN12and with WLAN14. More particularly, multi-mode mobile station16is able to communicate with WWAN12when operating in an area served by WWAN12and is able to communicate with WLAN14when operating in an area served by WLAN14. In some areas, the wireless coverage of WWAN12and WLAN14may be overlapping, and multi-mode mobile station16may decide whether to communicate with WWAN12, with WWAN14, or with both. Multi-mode mobile station16may be a wireless telephone, wirelessly-equipped personal digital assistants (PDA), wirelessly-equipped laptop computer, or other type of wireless communication device.

WWAN12may include a base transceiver station (BTS)18that provides a wireless coverage area within which BTS18may communicate with one or more mobile stations, such as multi-mode mobile station16, over an air interface20. AlthoughFIG. 1shows only BTS18, WWAN12may include a plurality of BTSs that may provide a plurality of wireless coverage areas. The communications between BTS18and multi-mode mobile station16may occur in a digital format, such as CDMA, TDMA, GSM, or they may occur in an analog format, such as AMPS. A preferred wireless communications format is cdma2000 such as described in EIA/TIA/IS-2000 Series, Rev. A (published March 2000), which is incorporated herein by reference.

BTS18may be controlled by a base station controller (BSC)22, which, in turn, may be controlled by a mobile switching center (MSC)24. AlthoughFIG. 1shows only one MSC and only one BSC, WWAN12may include a plurality of MSCs, which may, in turn, control a plurality of BTSs, via a plurality of BSCs. MSC24also has access to a visitor location register (VLR)26. VLR26stores data records for mobile stations, such as multi-mode mobile station16, that are being served by MSC24. A data record stored in VLR26for a mobile station typically identifies the mobile station, e.g., by mobile identification number (MIN), mobile directory number (MDN), mobile station identification (MSID), and/or electronic serial number (ESN). The data record may also include status information for the mobile station, such as whether the mobile station is busy, and may also include a service profile that identifies the services to which the mobile station subscribes. The data record may also include other information relating to the mobile station. VLR26may obtain some of the information in the data record for the mobile station from a home location register (HLR)28associated with the mobile station, e.g., using IS-41 signaling. AlthoughFIG. 1shows VLR26as a network element separate from MSC24, VLR26may be integrated or co-located with MSC24.

In the example shown inFIG. 1, WWAN12is the “home” network of multi-mode mobile station16, in that WWAN12includes a home location register (HLR)28associated with multi-mode mobile station16. HLR28stores a data record for multi-mode mobile station16. The data record stored in HLR28for multi-mode mobile station16identifies multi-mode mobile station16, such as by MDN, MIN, MSID, and/or ESN and includes a last known location of multi-mode mobile station16, e.g., identifies the VLR that most recently registered multi-mode mobile station16with HLR28. The data record may also include status information for multi-mode mobile station16, a service profile for multi-mode mobile station16, and other information relating to multi-mode mobile station16. WWAN12may also include a service control point (SCP)29. SCP29may include service logic that specifies how to provide telecommunications services to mobile stations such as multi-mode mobile station16.

MSC24is connected to the public switched telephone network (PSTN)30. PSTN30may use an out-of-band signaling system, such as Signaling System 7 (SS7) to route calls. Thus, PSTN30may include a circuit-switched network32that carries bearer traffic, i.e., the voice or other media in calls, and a signaling network34that carries signaling traffic used to set up, tear down, monitor, and control calls. Circuit-switched network32may include a plurality of trunks, with each trunk carrying media in a pulse code modulation (PCM) format in a plurality of time-domain multiplexed channels. Signaling system34may include a plurality of networked signal transfer points (STPs).

MSC24may communicate with signaling network34, e.g., using SS7, to route calls via circuit-switched network32to and from mobile stations being served by WWAN12, such as multi-mode mobile station16. To provide telecommunications services to mobile stations being served by WWAN12, such as multi-mode mobile station16, MSC24may also communicate with HLR28and SCP29via signaling network34. The communications between MSC24and HLR28may conform to IS-41 specifications. A recent revision of the IS-41 specifications, ANSI/TIA/EIA-41-D-97, published in December 1997, is incorporated herein by reference. The communications between MSC24and SCP29may conform to the specification “Wireless Intelligent Network,” TIA/EIA/IS-771, published in July 1999, which is incorporated herein by reference. The IS-41 and IS-771 signaling may be carried in an SS7 application layer in signaling network34.

Using SS7, IS-41, IS-771, and/or other signaling carried in signaling network34, MSC24may connect incoming calls from PSTN30to multi-mode mobile station16, which calls may originate from calling parties using landline telephones, mobile stations, or other communication devices. Similarly, MSC24may use SS7, IS-41, IS-771, and/or other signaling carried in signaling network34to route calls originating from multi-mode mobile station16through PSTN30. In addition, MSC24may be a “home” MSC of multi-mode mobile station16, in that multi-mode mobile station16may have a mobile directory number (MDN) that is assigned to MSC24. Thus, calls placed to this MDN may be routed to MSC24by PSTN30.

WLAN14includes a private branch exchange (PBX)36that may be communicatively coupled to a variety of wireline and/or wireless communication devices. For example, PBX36may be connected to analog telephony devices, such as analog telephone38, facsimile machines, and/or modems. PBX36may also be connected to digital telephony devices, such as digital telephone40. PBX36may also be communicatively coupled, e.g., via a local area network (LAN)42, to communication devices that exchange media in a packet-based format. For example, LAN42may be connected to a voice-over-packet (VoP) telephone44and to a personal computer46, equipped for audio communication, e.g., equipped with a microphone and speaker. LAN42may also connected to one or more wireless access points, such as wireless access point48. LAN42may also be connected to other devices.

Wireless access point48provides a wireless coverage area within which wireless access point48is able to communicate with wireless communication devices, such as multi-mode mobile station16, over an air interface50. More particularly, wireless access point48may communicate with multi-mode wireless communications devices, e.g., that are able to communicate with both a WWAN, such as WWAN12, and a WLAN, such as WLAN14. Wireless access point48may also communicate with wireless communication devices that may only be able to communicate with WLANs such as WLAN14. The wireless communication between wireless access point48and multi-mode mobile station16may conform to or make use of IEEE 802.11a, IEEE 802.11b, IEEE 802.11e, IEEE 802.11g, or IEEE 802.11h standards (referred to generally herein as “802.11x”), or variations thereof. These 802.11x standards are incorporated herein by reference. Alternatively or additionally, the wireless communication may conform to or make use of Bluetooth specifications, HomeRF specifications, of HiperLAN standards, or may occur in a cordless communication format or a Multichannel Multipoint Distribution Service (MMDS) format, or may involve some other protocol or format.

PBX36may be connected to PSTN30, e.g., to both circuit-switched network32and signaling network34. Thus, PBX36may be able to terminate calls to and originate calls from communication devices coupled to PBX36, via PSTN30. Alternatively, or additionally, PBX36may be an “IP-PBX” connected to a packet-switched network52, e.g., via LAN42and a router54. Thus, PBX36may be able to terminate calls to and originate calls from communication devices coupled to PBX36, via packet-switched network52. If PBX36is connected to both PSTN30and packet-switched network52, then PBX36may use PSTN30for some calls and may use packet-switched network52for other calls. For example, PBX36may preferentially use PSTN30to originate calls from certain communication devices, e.g., analog telephone38and digital telephone40, but PBX36may preferentially use packet-switched network52to originate calls from certain other communication devices, e.g., VoP telephone44, audio-equipped computer46, and wireless devices in communication with wireless access point48, such as multi-mode mobile station16. As another example, PBX36may preferentially use packet-switched network52for certain types of calls, such as long-distance calls.

Packet-switched network52may include one or more local area networks (LANs) and/or one or more wide area network (WANs), such as the Internet. Packet-switched network52may route packets using a network protocol, such as the Internet Protocol (IP), in combination with the User Datagram Protocol (UDP) or Transmission Control Protocol (TCP). The IP packets may be carried over lower level protocols, such as asynchronous transfer mode (ATM) protocols. Protocols, such as the Real-Time Transport Protocol (RTP), may be used to carry voice or other media through packet-switched network52in a real-time format. Relevant aspects of RTP are described in Schulzrinne, et al., “RTP: A Transport Protocol for Real-Time Applications,” Request for Comments 1889 (January 1996), which is incorporated herein by reference.

Other protocols, such as the Session Initiation Protocol (SIP) or the Session Initiation Protocol for Telephones (SIP-T), may be used to set up and/or manage communication sessions through packet-switched network52. Relevant aspects of SIP are described in Rosenberg, et al., “SIP: Session Initiation Protocol,” Request for Comments 3261 (June 2002), which is incorporated herein by reference. Relevant aspects of SIP-T are described in Vemuri, et al., “Session Initiation Protocol for Telephones (SIP-T): Context and Architectures,” Request for Comments 3372 (September 2002), which is incorporated herein by reference. SIP and/or other protocols may, in turn, use the Session Description Protocol (SDP) to describe the communication sessions that are being set up or managed. Relevant aspects of SDP are described in M. Handley, et al., “SDP: Session Description Protocol,” Request for Comments 2327 (April 1998), which is incorporated herein by reference.

In an exemplary embodiment, SIP is used to set up calls through packet-switched network52that involve WLAN14. WLAN14may include one or more SIP user agents for this SIP signaling. For example, PBX36may include a SIP user agent to engage in SIP signaling on behalf of communication devices coupled to PBX36. Alternatively or additionally, one or more communication devices coupled to PBX36may have SIP user agents of their own. For example, multi-mode mobile station16may have its own SIP user agent.

WLAN14also includes a virtual visitor location register (VVLR)56that helps to manage the mobility of multi-mode mobile stations, such as multi-mode mobile station16. VVLR56may be integrated or co-located with PBX36, as shown inFIG. 1. Alternatively, VVLR56may be provided in a separate network element that is accessible by PBX36, e.g., via LAN42. As described in more detail below, VVLR56communicates with HLR28for mobility management purposes. More particularly, VVLR56may communicate with HLR28using IS-41 or some other protocol, such as SIP, SIP-T, or H.323, and one or more other network elements may convert between the protocols used by VVLR56and the protocols used by HLR28. VVLR56may also store data records for the multi-mode mobile stations being served by WLAN14. For example, a data record stored in VVLR56for multi-mode mobile station16may include one or more of the following: the MAC and/or IP address of multi-mode mobile station16, the user name and/or SIP address of the user of multi-mode mobile station16, and the MIN, MDN, MSID, and/or ESN of multi-mode mobile station16. Thus, VVLR56may play a role that is analogous to that of an IS-41 VLR. However, VVLR56does not necessarily perform all of the functions of an IS-41 VLR and does not necessarily operate in accordance with IS-41 specifications.

A call management service58may control calls and other communication sessions in packet-switched network52that involve WLAN14. For example, if SIP is used to establish, tear down, or otherwise manage calls through packet-switched network52, call management service58may function as a SIP proxy server and SIP registrar for WLAN14. Thus, SIP user agents in WLAN14may engage in SIP signaling with call management service58to register communication devices communicatively coupled to WLAN14and to originate and terminate calls through packet-switched network52for such registered communication devices. Call management service58may also perform other functions. AlthoughFIG. 1shows call management service58as a separate network element, call management service58may be integrated with another network element, such as a media gateway controller.

Packet-switched network52may be communicatively coupled to circuit-switched network32via a media gateway60. Media gateway60may convert between media formats used in circuit-switched network30and packet-switched network52. For example, media gateway60may receive media from circuit-switched network32in a PCM format and convert the media into an RTP format for transmission over packet-switched network52, and vice-versa.

A media gateway controller62may control media gateway60, e.g., using the Media Gateway Control Protocol (MGCP). Relevant aspects of MGCP are described in F. Andreason, et al., “Media Gateway Control Protocol (MGCP) Version 1.0,” Request for Comments 3435 (January 2003), which is incorporated herein by reference. Media gateway controller62may be connected to signaling network34and to packet-switched network52. Media gateway controller62may engage in SS7 or other signaling to route calls to and from media gateway60through PSTN30, and media gateway controller may use SIP and/or other protocols to route calls to and from media gateway60through packet-switched network52.

Thus, media gateway controller62may function as a signaling gateway, converting between legacy signaling protocols, such as SS7, IS-41, and/or IS-771, and voice-over-packet signaling protocols, such as SIP, SIP-T, and/or H.323. For example, PBX36and/or VVLR56may communicate with HLR28and/or SCP29via media gateway controller62, with media gateway controller62converting between the SIP, SIP-T, H.323, or other protocols used by PBX36and/or VVLR56and the SS7, IS-41, IS-771, or other protocols used by HLR28and/or SCP29. The conversions performed by media gateway controller62may involve encapsulation/de-encapsulation of messages and/or translation of messages, i.e., mapping between message types and message parameters. Media gateway controller62may also perform other functions. For example, call management service58may be a part of media gateway controller62.

Calls may reach media gateway60via PSTN30by routing to a directory number assigned to media gateway60. If the directory number is also associated with a network element accessible via packet-switched network52, such as a communication device in WLAN14, then the call may also be routed from media gateway60through packet-switched network52. However, calls may also reach media gateway60in other ways. For example, media gateway60may be integrated with other network elements, such as MSC24. As a result, if a call is routed through PSTN30to MSC24, e.g., based on a directory number assigned to MSC24, then MSC24may not need to send the call again through PSTN30in order to have the call reach packet-switched network52. Instead, MSC24may use media gateway60integrated with it to send the call directly to packet-switched network52. As another example, media gateway60may be connected to MSC24via an intermachine trunk (IMT)64. In that case, MSC24may use a trunk and port number of IMT64, instead of a directory number, to send a call to media gateway60.

FIG. 2illustrates an exemplary call flow that may be used to register multi-mode mobile station16. The process may begin when multi-mode mobile station16transmits an association request, e.g., in accordance with 802.11x protocols, to associate with wireless access point48, as indicated by step100. Step100may occur, for example, when multi-mode mobile station16is being served by another wireless network, such as WWAN12, or is not being served by any wireless network, but detects radio frequency (RF) emissions from WLAN14. Multi-mode mobile station16may use a number of different methods to determine when to try to detect RF that may emanate from a WLAN. For example, multi-mode mobile station16may periodically check for RF emissions in frequency bands that may be used by WLANs, e.g., frequency bands in the 2.4 GHz range. Alternatively, multi-mode mobile station16may use information about its current location to determine when to check for RF from WLANs. Examples of such approaches are described in a U.S. patent application Ser. No. 10/391,158, titled “Method for Determining Availability of a Radio Network,” filed on Mar. 18, 2003, which is incorporated herein by reference. Step100may also occur when multi-mode mobile station16is being served by another wireless access point in WLAN14and moves into an area in which wireless access point48provides better coverage.

It is to be understood thatFIG. 2shows step100in a simplified form. In particular, the signaling involved in associating with WLAN14may depend on the particular air interface protocol that is used and may involve the exchange of several messages between multi-mode mobile station16and wireless access point48. For example, the signaling may involve procedures to authenticate multi-mode mobile station16for access to WLAN14. For example, WLAN14may require multi-mode mobile station16to transmit a valid username, password, PIN number, digital certificate, MAC address, or other code or identifier before granting access. If the association request of step100is accepted, then wireless access point48may transmit an association response indicating that multi-mode mobile station16is now associated with wireless access point48, as indicated by step102. Multi-mobile station16may then transmit a service registration message in order to register for services with PBX36, as indicated by step104. The service registration message may identify multi-mode mobile station16, such as by IP address and/or MAC address. The service registration message may conform to a protocol such as H.323 or Cisco's Skinny Client Control Protocol. Other protocols could be used, however. A recent version of the H.323 protocol is described in International Telecommunication Union, Recommendation H.323, “Packet-based Multimedia System” (November 2000), which is incorporated herein by reference.

As indicated by step106, PBX36may then send VVLR56a registration notification message to notify VVLR56that multi-mode mobile station16has registered for services. The registration notification message may also identify multi-mode mobile station16, such as by IP address and/or MAC address. In response to the registration notification of step106, VVLR56may create or update a data record for multi-mode mobile station16. The data record may identify multi-mode mobile station16, such as by IP address or MAC address. The data record may also include other information relating to multi-mode mobile station16. In some cases, VVLR56may update an existing data record for multi-mode mobile station16when VVLR56receives the association notification of step104. In other cases, VVLR56may create a new data record for multi-mode mobile station16in response to the association notification of step106.

As noted above, VVLR56may communicate with HLR28for purposes of managing the mobility of multi-mode mobile stations, such as multi-mode mobile station16. However, HLR28and WWAN12may identify multi-mode mobile station16differently than WLAN14. For example, HLR28and WWAN12may identify multi-mode mobile station16by MIN, MDN, MSID, and/or ESN, and may also require other information regarding multi-mode mobile station16. In some cases, VVLR56may have access to such WWAN parameters of multi-mode mobile station16because the WWAN parameters may have already been provisioned in PBX36and/or VVLR56. In other cases, multi-mode mobile station16may transmit the WWAN parameters automatically, e.g., in the service registration message of step104. In still other cases, VVLR56may request WWAN parameters from multi-mode mobile station16, such as MIN, MDN, MSCID, and/or ESN, as indicated by step108. Multi-mode mobile station16may then respond with the requested WWAN parameters, as indicated by step110.

VVLR56may then send HLR28an IS-41 Registration Notification (REGNOT) message, as indicated by step112. The REGNOT message indicates that multi-mode mobile station16is now operating in an area served by VVLR56, e.g., by identifying VVLR56as currently serving multi-mode mobile station16. The REGNOT message may identify multi-mode mobile station16, such as by MIN, MDN, MSID, and/or ESN, and may also identify VVLR56. For example, even though it is not an MSC, VVLR56may identify itself by a “MSCID” for purposes of IS-41 signaling. The REGNOT message may also include other information.

In response to the REGNOT message of step112, HLR28may update the data record it maintains for multi-mode mobile station16to indicate that multi-mode mobile station16is currently being served by VVLR56. HLR28also sends VVLR56an IS-41 regnot response, as indicated by step114. The regnot response may include a service profile for multi-mode mobile station16, and VVLR56may store the service profile as part of its data record for multi-mode mobile station16. HLR28may also cancel any previous registrations. For example, if multi-mode mobile station16had been previously been served by WWAN12and registered in VLR26, then HLR28may send VLR26an IS-41 Registration Cancellation (REGCANC) message to cancel the registration of multi-mode mobile station16in VLR26.

Although steps112and114have been described with respect to the IS-41 protocols, it is to be understood that VVLR56may use other protocols, such as SIP, SIP-T, or H.323, for communicating with HLR28. For example, VVLR56may use a SIP user agent, which may be located in PBX36, to communicate with media gateway controller62, via packet switched network52, using the SIP protocol. Media gateway controller62may, in turn, communicate with HLR28using IS-41, converting between the SIP messages used by VVLR56and the IS-41 messages used by HLR28. This conversion may involve encapsulation/de-encapsulation of IS-41 messages in SIP message and/or mapping between message types and message parameters.

The service profile provided to VVLR56in step114may identify any call origination services, call termination services, or other services that multi-mode mobile station16subscribes to in WWAN12. In some embodiments, PBX36may use this service profile information to provide multi-mode mobile station16with the same or similar services that multi-mode mobile station16would have when served by WWAN12. In other embodiments, PBX36may provide multi-mode mobile station16with services that are different from the services that multi-mode mobile station16would have when served by WWAN12.

After multi-mode mobile station16associates with wireless access point48, multi-mode mobile station16may also become registered with call management service58. For example, if SIP is used to set up calls through packet-switched network52, then a SIP user agent may send a SIP REGISTER message to call management service58, as indicated by step116.FIG. 2assumes that the SIP user agent is in PBX36. Alternatively, however, multi-mode mobile station16may have its own SIP user agent, in which case the SIP REGISTER message may originate from multi-mode mobile station16. In response to the SIP REGISTER message, call management service58may store an indication that multi-mode mobile station16is reachable at WLAN14. Call management service58may also associate multi-mode mobile station16with a directory number that can be used to reach multi-mode mobile station16, e.g., a directory number assigned to media gateway60.

FIG. 3is an exemplary call flow diagram illustrating an exemplary process that may be used to route a call to multi-mode mobile station16when multi-mode mobile station16is being served by WLAN14. It is to be understood that multi-mode mobile station16will at this point already be registered with VVLR56, HLR28, and call management service58, e.g., using signaling like that shown inFIG. 2and described above.

The process may begin when a caller places a call to a directory number associated with multi-mode mobile station16, for example, its MDN. The caller may place the call using a landline telephone, wireless telephone, or other communication device. In this case, the directory number is assigned to MSC24, and MSC24receives the call. For example, PSTN30may route the call to MSC24, or the call may originate from a mobile station operating in an area served by MSC24. Although the directory number of multi-mode mobile station16is assigned to MSC24in this example, it is to be understood that the directory number could be assigned to other network elements instead, such as media gateway60.

To locate multi-mode mobile station16, MSC24may send HLR28an IS-41 Location Request (LOCREQ) message, as indicated by step200. The LOCREQ message may identify multi-mode mobile station16, e.g., by its MDN. In response, HLR28refers to its data record for multi-mode mobile station16and determines that multi-mode mobile station16was last known to be operating in an area served by VVLR56. Thus, HLR28sends VVLR56an IS-41 Route Request (ROUTEQ) message to obtain routing information that can be used to route the call to multi-mode mobile station16, as indicated by step202. The ROUTEREQ message may identify multi-mode mobile station16, such as by MIN, MDN, MSID, and/or ESN. In response, VVLR56sends HLR28an IS-41 routereq response that includes routing information that can be used to route the call to multi-mode mobile station16, as indicated by step204.

The routing information can be in a variety of different forms. For example, the routing information could be a directory number. The directory number may be assigned to a network element, such as PBX36or media gateway60. The directory number may be used for multi-mode mobile station16on only a temporary basis. For example, the directory number may be associated with multi-mode mobile station16for only during the time when multi-mode mobile station16is being served by WLAN14or only for purposes of this particular call to multi-mode mobile station16. Alternatively, the routing information could be an IP address, e.g., an IP address of PBX36, VVLR56, or multi-mode mobile station16. Other types of routing information could also be used, such as the host name of PBX36or VVLR56, or a SIP user name or address.

In the example shown inFIG. 3, the routing information in the routereq response of step204is a directory number (DN). HLR28forwards the DN to MSC24in an IS-41 locreq response message, as indicated by step206. MSC24then routes the call to the DN, e.g., using an SS7 ISUP-IAM message. For example, if the DN is assigned to PBX36, then MSC24may use an ISUP-IAM message to route the call to PBX36, via PSTN30. PBX36may then alert multi-mode mobile station16of the incoming call.

However, in the example shown inFIG. 3, the DN is assigned to media gateway60. Thus, MSC24may use an ISUP-IAM message to route the call to media gateway60via PSTN30, as indicated by step208. The ISUP-IAM identifies the DN as the called number. Media gateway controller62receives the ISUP-IAM message and engages in signaling to set up a call leg through packet-switched network52to a network element associated with the DN. For example, media gateway controller62may send call management service58a SIP INVITE message with the DN, as indicated by step210. In this case, PBX36has previously registered multi-mode mobile station16with call management service58(step116shown inFIG. 2and described above). Thus, call management service58may then send PBX36a SIP INVITE message that identifies multi-mode mobile station16, as indicated by step212. In response, PBX36may alert multi-mode mobile station16, as indicated by step214. In this case, multi-mode mobile station16answers, as indicated by step216.

As indicated by step218, PBX36then sends call management service58a 200 OK message to respond to the SIP INVITE message of step212. The 200 OK message may use SDP to describe various aspects of the session to be used for carrying the media exchanged in the call through packet-switched network52. For example, the 200 OK message confirm that RTP is to be used for the session and may specify that the RTP packets are to be sent to a particular IP address. Call management service58then sends media gateway controller62a 200 OK message, as indicated by step220. The 200 OK message of step220may include the session description from the 200 OK message of step218.

When media gateway controller62receives the 200 OK message of step218, media gateway controller62may instruct media gateway60to create a connection between the call media gateway60received from MSC24(on the circuit-switched side) and the RTP session described in the 200 OK message of step220(on the packet-switched side). For example, media gateway controller62may send media gateway60an MGCP CreateConnection message, as indicated by step222. In response, media gateway60creates the requested connection and sends media gateway controller62an acknowledgement, as indicated by step224. Then, media gateway controller62then sends call management service58an acknowledgement, as indicated by step226, and call management service58sends PBX36an acknowledgement, as indicated by step228.

At this point, the call is established between the caller and multi-mode mobile station16. The voice or other media exchanged between the caller and multi-mode mobile station16may be carried between MSC24and media gateway, via circuit-switched network32, in a PCM format, as indicated by step230, and may be carried between media gateway60and multi-mode mobile station16, via packet-switched network52, in an RTP format, as indicated by step232.

FIG. 4shows an exemplary call flow for the case that VVLR56returns an IP address as the routing information to route a call to multi-mode mobile station16. The IP address may be associated with PBX36or with multi-mode mobile station16, for example. In addition,FIG. 4assumes that MSC24and media gateway60are connected by an intermachine trunk (IMT), e.g., IMT64. The process may begin when MSC24receives a call to a directory number associated with multi-mode mobile station16. Thus, MSC24may send HLR28a LOCREQ message, as indicated by step300, and HLR28may send a ROUTEREQ message to VVLR56, as indicated by step302, e.g., in a manner similar to the example ofFIG. 3. In this example, however, VVLR56sends HLR28a locreq response that includes an IP address as the routing information to route the call to multi-mode mobile station16, as indicated by step304.

Although steps302and304have been described with respect to the IS-41 protocols, it is to be understood that VVLR56may use other protocols, such as SIP, SIP-T, or H.323, for communicating with HLR28. For example, the communications between VVLR56and HLR28may occur via media gateway controller62, which may convert between the IS-41 protocol used by HLR28and the SIP or other protocol used by VVLR56.

Once HLR28receives the routing information provided in step304, HLR28may communicate with media gateway controller62to set up a media gateway, such as media gateway60, that is able to route the call to the IP address obtained from VVLR56. For example, HLR28may communicate with media gateway controller62, using IS-41 signaling, as if media gateway controller62were an MSC. In particular, to set up the call HLR28may send media gateway controller62a message that includes the IP address from VVLR56, as indicated by step306. HLR28may also send media gateway controller62information regarding what vocoder formats are supported by multi-mode mobile station16.

In response, media gateway controller62acts to set up the call through media gateway60to this IP address. Media gateway controller62may also identify an IMT trunk and port number that can be used for the call on the circuit-switched side of media gateway60. Media gateway controller62may send the trunk and port number to HLR28, as indicated by step308. HLR28then sends the trunk and port number to MSC24in a locreq response message, as indicated by step310. In response, MSC24forwards the call to media gateway60using the specified trunk and port number, as indicated by step312.

To set up the call through packet-switched network52from media gateway60, media gateway controller62may send call management service58a SIP INVITE message that invites a session with the IP address supplied by VVLR56, as indicated by step314. Acting as a SIP proxy server, call management service58forwards the SIP INVITE message to PBX36, as indicated by step316. In response, PBX36may alert multi-mode mobile station16, as indicated by step318. Multi-mode mobile station16then answers, as indicated by step320.

PBX36then sends a 200 OK message to call management service58, as indicated by step322, and call management service58sends a 200 OK message to media gateway controller62, as indicated by step324. Media gateway controller62may then send media gateway60a MGCP CreateConnection message, as indicated by step326. The CreateConnection message instructs media gateway60to create a connection between the trunk and port number used by MSC24and an RTP session with the IP address. Once media gateway60has created this connection, it responds with an acknowledgement, as indicated by step328. Media gateway controller62then sends an acknowledgement to call management service58, as indicated by step330, and call management service58sends an acknowledgement to PBX36, as indicated by step332.

At this point, the call is established between the caller and multi-mode mobile station16. The voice or other media exchanged between the caller and multi-mode mobile station16may be carried between MSC24and media gateway60, via the intermachine trunk, in a PCM format, as indicated by step334, and may be carried between media gateway60and mobile station16, via packet-switched network52, in an RTP format, as indicated by step336.

Thus, the communication between VVLR56and HLR28help manage the mobility of multi-mobile station16between WWAN12and WLAN14. As illustrated inFIGS. 3 and 4, when multi-mode mobile station16is being served by WLAN14, multi-mode mobile station16can still be reached by dialing the same directory number (e.g., its MDN) that can be used to reach multi-mode mobile station16when it is being served by WWAN12.