Like reference symbols in the various drawings indicate like elements.
At a high level, system 100 includes mobile devices 102, core networks 104, access networks 106, and communication node 108. Each mobile device 102 comprises an electronic device operable to receive and transmit wireless communication with system 100. As used in this disclosure, mobile devices 110 are intended to encompass cellular phones, data phones, pagers, portable computers, smart phones, personal data assistants (PDAs), one or more processors within these or other devices, or any other suitable processing devices capable of communicating information over a wireless link to access networks 106. In the illustrated embodiment, mobile devices 102 is able to transmit in multiple bands such as in the cellular band and WiFi band. In these cases, messages transmitted and/or received by mobile device 102 may be based on a cellular radio technology and/or a broadband technology. Conventionally, special handsets are required for operating in a dual-mode using a cellular radio technology and UMA. In this case, conventional 2G and 3G systems, while some are operable to transmit in the WiFi band, need additional hardware and updates to call processing software to fully operate using UMA. As a result, substantial expense and effort would be needed to fully convert such 2G and 3G systems to fully operational dual-mode systems. In contrast, a software client (discussed in
In the illustrated embodiment, core networks 104 include cellular core network 104a, PSTN 104b, and IMS network 104c. Cellular core network 104a typically includes various switching elements and gateways for providing cellular services. Cellular core network 104 often provides these services via a number of RANs, such as RAN 106a, and also interfaces the cellular system with other communication systems such as PSTN 104b via mobile switching center (MSC) 110. In accordance with the GSM standard, cellular core network 104a includes a circuit switched (or voice switching) portion for processing voice calls and a packet switched (or data switching) portion for supporting data transfers such as, for example, e-mail messages and web browsing. The circuit switched portion includes MSC 110 that switches or connects telephone calls between RAN 106a and PSTN 104b or other network. The packet-switched portion, also known as General Packet Radio Service (GPRS), includes a Serving GPRS Support Node (SGSN) (not illustrated), similar to MSC 110, for serving and tracking mobile devices 102, and a Gateway GPRS Support Node (GGSN) (not illustrated) for establishing connections between packet-switched networks and mobile devices 102. The SGSN may also contain subscriber data useful for establishing and handing over call connections. Cellular core network 104a may also include a home location register (HLR) for maintaining “permanent” subscriber data and a visitor location register (VLR) (and/or a SGSN) for “temporarily” maintaining subscriber data retrieved from the HLR and up-to-date information on the location of mobile devices 102. In addition, cellular core network 104a may include Authentication, Authorization, and Accounting (AAA) that performs the role of authenticating, authorizing, and accounting for devices 102 operable to access cellular core network 104a.
PSTN 104b comprises a circuit-switched network that provides fixed telephone services. A circuit-switched network provides a dedicated, fixed amount of capacity (a “circuit”) between the two devices for the duration of a transmission session. In general, PSTN 104b may transmit voice, other audio, video, and data signals. In transmitting signals, PSTN 104b may use one or more of the following: telephones, key telephone systems, private branch exchange trunks, and certain data arrangements. Since PSTN 104b may be a collection of different telephone networks, portions of PSTN 104b may use different transmission media and/or compression techniques. Completion of a circuit in PSTN 104b between a call originator and a call receiver may require network signaling in the form of either dial pulses or multi-frequency tones.
IMS network 104c is a network that enables mobile communication technology to access IP based services. The IMS standard was introduced by the 3rd generation partnership project (3GPP) which is the European 3rd generation mobile communication standard. In general, the IMS standard discloses a method of receiving an IP based service through a wireless communication terminal such as mobile devices 102. To achieve these goals, IMS network 104c uses SIP and, in some embodiments, mobile device 102 is operable to use the same protocol when accessing services through broadband network 106b. Although not illustrated, IMS network 104c may include call session control function (CSCF), home subscriber server (HSS), application server (AS), and other elements. CSCF acts as a proxy and routes SIP messages to IMS network components such as AS. HSS typically functions as a data repository for subscriber profile information, such as type of services allowed for a subscriber. AS provides various services for users of IMS network 104c, such as, for example, video conferencing, in which case AS handles the audio and video synchronization and distribution to mobile devices 102.
Turning to access networks 106, access networks 106 include RAN 106a and broadband network 106b. RAN 106a provides a radio interface between mobile devices 102 and cellular core network 104a that may provide real-time voice, data, and multimedia services (e.g., a call) to mobile devices 102. In general, RAN 106a communicates air frames 112 via radio frequency (RF) links. In particular, RAN 106a converts between air frames 112 to physical link based messages for transmission through cellular core network 104a. RAN 106a may implement, for example, one of the following wireless interface standards during transmission: IS-54 (TDMA), Advanced Mobile Phone Service (AMPS), GSM standards, CDMA, Time Division Multiple Access (TDMA), General Packet Radio Service (GPRS), ENHANCED DATA rates for Global EVOLUTION (EDGE), or proprietary radio interfaces.
RAN 106a may include Base Stations (BS) 114 connected to Base Station Controllers (BSC) 116. BS 114 receives and transmits air frames 112 within a geographic region of RAN 106a called a cell and communicates with mobile devices 102 in the cell. Each BSC 116 is associated with one or more BS 114 and controls the associated BS 114. For example, BSC 116 may provide functions such as handover, cell configuration data, control of RF power levels or any other suitable functions for managing radio resource and routing signals to and from BS 114. MSC 110 handles access to BSC 116 and communication node 108, which may appear as a BSC 116 to MSC 110. MSC 110 may be connected to BSC 116 through a standard interface such as the A-interface.
Broadband network 106b facilitates communication between mobile devices 102 and communication node 108. In general, network 106b communicates IP packets to transfer voice, video, data, and other suitable information between network addresses. In the case of multimedia sessions, network 106b uses Voice over IP (VoIP) protocols to set up, route, and tear down calls. Network 106b may include one or more local area networks (LANs), metropolitan area networks (MANs), wide area networks (WANs), all or a portion of the global computer network known as the Internet, and/or any other communication system or systems at one or more locations. In the illustrated embodiment, IP network 106b includes SIP proxy servers 134 for routing SIP messages. Each SIP proxy server can be any software, hardware, and/or firmware operable to route SIP messages to other SIP proxies, gateways, SIP phones, communication node 108, and others.
In general, communication node 108 can include any software, hardware, and/or firmware operable to provide voice call continuity during handovers between legs using cellular radio technology and legs using broadband technology. For example, mobile device 102 may access core networks 104 either through RAN 106a or broadband network 106b. In this case, when mobile device 102 switches between these two access networks 106 during a call session, communication node 108 may provide continuity of a call session between mobile device 102 and core network 104 transparent to the participating core network 104. In other words, communication node 108 may switch between a call leg using a cellular radio technology (e.g., GSM) and a call leg using broadband technology (e.g., SIP). In general, a node may integrated and/or stand alone unit and, in addition, may be part of a rack or system. In some embodiments, communication node comprises a system. A system may be a single node, a plurality of nodes, a portion of one or more nodes. A system may be distributed and may cross network boundaries.
In some embodiments, communication node 108 locally manages handovers between access networks 106. Communication node 108 may be operable to receive a request from device 102 to generate a call session through an access network 106 and identify that device 102 as currently having a call session through the other access network 106. For example, communication node 102 may receive a request to establish a call session through cellular core network 106a and identify that mobile device 102 has an existing call session established through broadband network 106b. In this case, communication node 108 may manage authentication and resource assignment for establishing the call session through cellular core network 106a. After performing these steps, communication node 108 may terminate the call leg through broadband network 106b and connect the call leg through RAN 106a to the remaining portion of the existing call session. In doing so, communication node 108 may provide voice call continuity transparent to the core network 104 participating in the call session. In other words, communication node 108 may serve as an anchor such that call controls maintained by the core network 104 remain constant.
In managing different communication technologies, communication node 108 may convert between cellular and/or broadband technologies. For example, communication node 108 may receive a GSM request from mobile device 102 to access services from IMS network 104c. In this case, communication node 108 may convert the GSM request to a SIP request prior to transmitting the request to IMS network 104c. The conversion may include conversion between parameters of different communication technologies and/or bit conversion. In addition, communication node 108 may also be operable to convert other broadband messages such as SIP messages to cellular radio technology messages such as GSM messages. For example, communication node 108 may be receive a SIP request from mobile device 102 to access services from cellular core network 104a, and prior to transmitting the message to cellular core network 104a, communication node 108 may convert the SIP request to a GSM request.
Communication node 108 may, in one embodiment, emulate or otherwise represent itself as an element of core network 104. For example, communication node 108 may emulate or otherwise represent itself as a BSC, MSC, PCSCF (not illustrated) or other element of a core network 104. In the case that communication node 108 emulates a BSC, communication node 108 may be queried by MSC 110 in cellular core network 104a like any other BSC 116. In the case of communication node 108 emulating a MSC, communication node 108 may query BSC 116 and perform call management functions associated with MSCs (e.g., Mobility Management, Call Control, Services). In the case that communication node 108 emulates a PCSCF, communication node 108 may be queried by CSCF in IMS network 104c like any other PCSCF.
In one aspect of operation, mobile device 102b transmits a request for services from IMS network 104c. In response to at least the request, communication node 108 checks an associated VLR (not illustrated) to determine if mobile device 102 is registered. In the event that mobile device 102 is not registered, communication node 108 registers, authenticates, and provisions resources to establish a call leg through broadband network 104c. Communication node 108 may use SIP/RTP to establish the call leg. During the call section, mobile device 102 may periodically and/or in response to an event determine if mobile device 102 is within operating range of RAN 106a. In response to at least detecting RAN 106a, mobile device 102 may transmit a request to establish a call leg through RAN 116, which is transmitted to communication node 108 via cellular core network 104a. After determining that mobile device 102 is registered and authenticated, communication node 108 identifies that mobile device 102 has an existing call leg through broadband network 106b. Prior to terminating the call leg through broadband network 106b, communication node 108 provisions resources in cellular core network 104a and RAN 106a using, for example, GSM. After establishing the cellular call leg, communication node 108 terminates the broadband call leg and connects the cellular call leg to the remaining call session. In some embodiments, the handover between the broadband technology and the cellular communication technology is transparent to IMS network 104c.
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In the event that mobile device 102 identifies broadband network 106b, mobile device 102 may transmit a request to establish a call leg through broadband network 106b. In some embodiments, communication node 108 forwards the request to MSC 110 to perform initial management functions such as authentication. In response to at least the request, communication node 108 may establish broadband call leg 216. After establishing broadband call leg 216, communication node 108 may terminate cellular call leg 214 and connect broadband call leg 216 with the call leg 212 to maintain the call session. In some embodiments, communication node 108 performs this handover between the different technologies independent of MSC 110.
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In one aspect of operation, a call session between mobile device 102 and IMS network 104c may include call leg 228 and broadband call leg 230. In embodiments that mobile device 102 is a SIP-based phone, SIP messages are merely routed through communication node 108 without any modification or translation because IMS network 104c is a SIP based network. In the event that mobile phone detects RAN 106a, mobile device 102 may transmit a request to establish cellular call leg 232 to communication node 108. In this case, the request is forward to MSC 110 to authenticate mobile device 102 and provisions resources in cellular core network 104a and RAN 106a. After cellular call leg 232 is established, communication node 108 terminates broadband call leg 230 and connects cellular call leg 232 to call leg 228. In this case, communication node 108 may translate messages between the cellular radio technology associated with MSC 110 and SIP.
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As discussed above, mobile device 102 is operable to access core networks 104 through RAN 106a and broadband network 106b. Mobile device 102 may switch between these access networks 106 during a call session providing continuity to the call session. In addition, the handover between access networks 106 may be transparent to the user of mobile device 102. In some embodiments, VCC module 302 can include any software, hardware, and/or firmware operable to implement methods for providing GSM service (e.g., voice calls) over I-WLAN when mobile device 102 detects sufficient coverage. In some embodiments, VCC module 302 includes a 3GPP standard to support the GSM service over I-WLAN. In providing voice call continuity between a CS Domain and an I-WLAN, or other IP-CANs, mobile device 102 may reduce, eleiminate, or minimize the use GSM/UMTS radio resources. SIP client 304 can include any software, hardware, and/or firmware operable to implement SIP protocols. In some embodiment, SIP client 304 is solely a software module enabling easy distribution to 2G and 3G wireless devices. SIP client 304 may facilitate formation, modification and execution of communication sessions between mobile device 102 and elements in system 100. In addition, SIP client 304 may enable peer-to-peer communication and/or multipoint communication. In the event that a SIP session is being established with mobile device 102, SIP client 304 may determine information in accordance with the SIP protocol, a port and/or an IP address of the element in system 100 that mobile device 102 is establishing a call session with. GSM module 306 can include any software, hardware, and/or firmware operable to communication with a GSM network in accordance with GSM standards. WiFi module 308 can include any software, hardware, and/or firmware operable to communication with a WLAN network in accordance with Internet Engineering Task Force (IETF) standards.
As discussed above, communication node 108 may provide call session continuity during handovers between different communication technologies such as GSM and SIP. In doing so, communication node 108 may enable mobile device 102 to maintain services from core networks 104 (e.g., PSTN 104b) while switching between different access networks 106. SI 402 can include any software, hardware, and/or firmware operable to provide an interface for connecting to an external SS7 network such as PSTN 104b. In this case, SI 402 processes messages between communication node 108 and PSTN 104b. After an SS7 message is received, PE 404 includes any software, ahrdware, and/or firmware operable to provide routing routing functionality of SS7 messages to other subsystems internal to communication node 108 such as CE 408. In routing to a CE 408, PE 404 may perform resource management functions to determine the various loads of the plurality of CE 408a through 408n. In addition, PE 404 may also perform interface functionality of SIP messaging as well as overall resource management. SE 406 may provide a switching fabric for intra-shelf (card-to-card) communications. Once a message has been routed to an appropriate CE 408, CE 408 includes any software, hardware, and/or firware operable to provide call processing functionality (e.g., CC, MM, signaling gateway, translation, services, VCC, Megaco, Interaccess HO).
CC module 502 maintains a state of a call session in system 100. As discussed above, mobile device 102 may roam in system 100, so MM module 504 may provide mobility functionality for mobile device 102 such as location updates. SG 506 may provide processing, translation and interworking within signaling nodes of system 100. Translation module 508 may perform digit translation for a call session. Services module may 510 provide services requested for a call session including supplementary services. VCC module 510 may provide server functionality for voice call continuity function. Megaco module 512 may provide an interface with a media gateway. Interaccess HO module 514 may provide functionality for handovers between RAN 106a (e.g., GSM, UMTS) and broadband network 106b (e.g., SIP/WIFI).
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Although this disclosure has been described in terms of certain embodiments and generally associated methods, alterations and permutations of these embodiments and methods will be apparent to those skilled in the art. Accordingly, the above description of example embodiments does not define or constrain this disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of this disclosure.