Untitled record

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DESCRIPTION

Voice service provisioning in a multimedia network between mobiles

Field of the invention

The present invention relates to multimedia networks. More specifically, and not by way of limitation, the present invention relates to providing voice service in a mobile-to-mobile multimedia network.

Background of the invention

The UMTS (Universal Mobile Telecommunications System) Terrestrial Radio Access Network (UTRAN) is a 3G technology for the wireless provision of multimedia services. The development of the Evolved UTRAN (eUTRAN), also known as Long Term Evolution (LTE) and Evolved Core Packet (EL EPC), requires for telephony services to be migrated from a traditional circuit switched system (CS) to a packet switched system (PS), for example, provided by the Multimedia Telephony Service for IMS (MTSI). This requires that the Internet Protocol (IP) Multimedia Subsystem (IMS) be widely developed before the eUTRAN and the EPC.

It would be advantageous to provide an architecture that allows reuse of the deployed CS core network infrastructure to support voice service by introducing eUTRAN and EPC.

Reference is made to US 2005/245263 A1 (EJZAK RICHARD P). Ejzak refers to a method in which a packet call controller establishes a bearer route between the endpoint and the second network when a call transfer request associated with the mobile station is received from a network that provides circuit communication switched. The call transfer request is triggered by the origin of a circuit voice call from the mobile station that includes an identifier used by the packet call controller in recognition that the call transfer request requests the transfer of a call. packet switched call to a circuit switched call in the network. This is different from the present invention which is directed to either the mobile station or the network, which causes a change in the serving cells in the interest of establishing a flat user carrier in the CS domain for the voice in the new cell when there is no user flat bearer in the previously existing PS domain PS for ongoing voice service in the old cell.

Further reference is made to EP 1 753 260 A (HUAWEI TECH CO LTD). Huawei refers to a method for handover from the Packet Switching (PS) domain to the Circuit Switching (CS) domain. In the method, the Mobile Station (MS) obtains a handover number and initiates a CS domain session request, taking the handover number as a called number. The network side associates the CS domain session request with an original MS session and notifies the MS to terminate an air interface handover from the PS domain to the CS domain. The MS then notifies the network side to terminate a network side handover from the PS domain to the CS domain. This is different from the present invention, where there is no previously existing service in the PS domain of a serving cell that needs to be migrated to the CS domain of a target cell using handover or any other procedure.

Additional reference is made to WO 2007/007990 A (SAMSUNG ELECTRONICS CO). Samsung refers to a method and apparatus that performs handover from an E-UMTS system to a UMTS system. An E-UMTS system E-RAN determines to perform handover based on the measured strength of a UMTS system signal reported from a UE. Then, an E-CN of the E-UMTS system generates a PDP context and an MM context for the UE, and establishes a data tunnel from the UE to a GGSN of the UMTS system using the PDPlMM context. The E-CN then sends the UE a handover command message that includes information about an RB to be used by the UE to access the UMTS system. The UE accesses the UMTS system using the RB information, and sends user data to the UE through a data transmission path composed of the E-CN, the data tunnel, an SGSN and a RAN of the system. UMTS. This is different from the present invention, which is directed to the case where the network, realizing the need to establish a service that is better managed in the CS domain, performs operations for the mobile station to migrate (for example, using handover) to a new cell where CS domain services are supported (ie, transmission of the flat payload to the user takes place only within the new cell).

Brief summary of the invention

In one aspect, the present invention relates to a mobility management entity according to claim 1.

In another aspect, the present invention relates to a user equipment according to claim 7.

In still another aspect, the present invention relates to an eNodeB according to claim 11.

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In still another aspect, the present invention relates to a method for user equipment to establish a voice service according to claim 15.

In still another aspect, the present invention relates to a method for providing voice service to a User Equipment (UE) operating in a packet-switched domain of a cell of the System Radio Access Terrestrial Evolved Network. Universal Mobile Telecommunications (eUTRAN) according to claim 18.

In yet another aspect, the present invention relates to a network according to claim 25.

In still another aspect, the present invention relates to a method for an Evolved Packet Core to establish a voice service according to claim 31.

Brief description of various views of the drawing

In the following section, the invention will be described with reference to examples of embodiments illustrated in the figures, in which:

Figure 1 is a schematic representation of a network used in one embodiment of the present invention;

Figure 2 is a flow chart of a method for providing packet switched handover from a cell of the eUTRAN;

Figure 3 shows the interfaces of the network of Figure 1;

Figure 4 shows a procedure for joining the UE network; Y

Figure 5 shows a terminating voice call.

Detailed description of the invention

A network 10 is shown generally in Figure 1. A CS Core Network (CN) 11 includes a Media Gateway (MGW) 21 and a Mobile Switching Center (MSC) 22. Other aspects of the CS domain, such as the Home Location Register (HLR), etc., are assumed to be present as well, but have been omitted for clarity. The CS Core Network 11 provides voice service from a Public Switched Telephone Network (PSTN) 23 to user equipment (UE) 12 through 2G / 3G Radio Access Network (RAN) cells, by For example, GERAN (GSM / Edge Radio Access Network) or UTRAN 14. Network 10 also includes an Evolved Packet System (EPS) comprising an eUTRAN 16 that provides PS services, including voice, over of one or more cells of eUTRAN. PS services are provided from a Packet Data Network 17 through an Evolved Packet Core (EPC) network 18 that includes a service gateway 19 and a Mobility Management Entity (MME) 15. The MME 15 provides control aspects including tracking the location of the UE in idle mode, as well as search procedures, in accordance with the eUTRAN standards.

In the network 10 of Figure 1, voice service can be provided to the UE 12 in the PS domain through the eUTRAN cells or in the CS domain through the GERAN / UTRAN cells since The coverage areas provided by these cells are expected to carry a very significant degree of overlap. In the present example, the UE 12, also called a mobile station (MS), is considered to be operating in an eUTRAN cell controlled by eUTRAN 16 (also known as an LTE cell) with one or more active packet services that they do not include a voice component, ie there is no ongoing voice service in the eUTRAN cell. When a voice service is needed, it could be established in the PS domain as a VoIP service within the current eUTRAN cell. However, if eUTRAN service deployment, which is gradual in that IMS service, is not present in the initial LTE deployment, there may be eUTRAN coverage areas that are overlapped by GERAN / UTRAN coverage areas. . In these overlapping areas, the continuity of the voice service initiated within the cells of the eUTRAN may not be possible when the UE 12 approaches the edge of the coverage of the eUTRAN due to the lack of the domain transfer function (DTF associated with the deployment of the IMS service. Therefore, to allow voice calls to be established in a cell of the eUTRAN when the IMS is not supported, it would lead to those calls being dropped if the UE were to leave the LTE coverage area. If, on the other hand, at the time when voice service is desired, the UE 12 is made to leave the eUTRAN cell even though the eUTRAN coverage is still available and takes advantage of the overlapping coverage area of a 2G (GERAN) or 3G (UTRAN) cell, then voice service can be established in the CS domain using a 2G / 3G cell without worrying about it dropping prematurely, as it might happen if it was set to the eUTRAN cell, since 2G / 3G cell coverage is considered to go everywhere. Thus, in one embodiment, the requirement to establish a voice service while the UE 12 is within LTE coverage causes a handover of the UE 12 from the eUTRAN cell to a GERAN / UTRAN cell in which the desired voice service in the CS domain.

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A method for providing voice service to a UE operating in a packet switched domain of a cell of the eUTRAN will now be described with reference to Figure 1 and flow chart 100 of Figure

2. In step 101, a requirement to establish a voice service is identified. Then a CS cell that is capable of supporting the voice service is determined (step 102). In one embodiment, the voice service requirement may be a terminated voice call from the mobile (MT) resulting in the MSC sending a voice call page to the MME. The MME 15 forwards the search to the eNodeB which can then send a control plane message directly to the UE indicating that voice service is needed in the MT CS domain. In this case, the search that the MME sends to the eNodeB indicates that the establishment of voice calls is required in the CS domain. Alternatively, the eNodeB 33 may indirectly send this control plane message to the UE (i.e., after first sending the UE a page without an indication that the CS MT domain voice service needs to be established), receiving a UE search response, forwarding the paging response to the MME and then receiving a signaling message from the MME indicating that handover to a GERAN / UTRAN cell should be done for the purpose of establishing the MT voice service in the CS domain. Receipt of a control plane message as such by a UE 12 operating in an eUTRAN cell causes the UE 12 to generate a measurement report indicating a specific GERAN / UTRAN cell to which handover is preferred by PS. The measurement report may also indicate multiple GERAN / UTRAN cells to which handover is acceptable along with an indication of the preferred GERAN / UTRAN cell first, the second preferred GERAN / UTRAN cell, etc.

In one embodiment, the voice service requirement may be a voice call originated from a mobile (MO), in which case the eNodeB directly receives a request for the establishment of a MO voice service in the CS domain as a result the UE autonomously sends it a measurement report indicating that handover to a GERAN / UTRAN cell is desired. Alternatively, the eNodeB may indirectly receive a request for the establishment of a MO voice service in the CS domain when the UE sends a voice service request to the MME which then responds by sending the eNodeB a message. signaling indicating that handover to a GERAN / UTRAN cell should be done with the intention of establishing a MO voice service in the CS domain. In this indirect case, once the eNodeB receives a request for the establishment of a MO voice service in the CS domain, it sends a signaling message to the UE asking it to send a measurement report that includes only GERAN / cells. UTRAN. For both the direct and the indirect case, a measurement report is sent by the UE indicating a specific GERAN / UTRAN cell to which handover is preferred or multiple GERAN / UTRAN cells to which handover is acceptable together with a indication of the preferred GERAN / UTRAN cell first, the second preferred GERAN / UTRAN cell, etc. For direct case system broadcast information, it is necessary for a Ue to report that it can generate a voice service request in the CS domain by sending an unsolicited measurement report that includes only GERAN / UTRAN cells.

Once the PS handover has been triggered (i.e. the ongoing non-voice services in the LTE cell are allocated to radio resources for use in the 2G / 3G cell selected for handover), the UE 12 receives a PS handover command, leaves the eUTRAN cell, reaches the target GERAN / UTRAN cell and sends a page response to the MSC (for the MT voice call) or otherwise points out the need for CS domain resources to be allocated (for MO case). The voice service in the CS domain is then established, in step 103, between the UE 12 and the GeRaN / UTRAN 14 and the CN of CS 11 as by legacy procedures for the MT / MO call establishment.

If the UE 12 and the GERAN / UTRAN 14 do not both support dual transfer mode, then once the voice service has been established in the CS domain, the PS resources are released. If the UE and the GERAN / UTRAN 14 both support dual transfer mode, then the PS resources are kept in parallel with the resources required for the CS domain voice service. The case of PS handover to a UTRAN cell can be considered as the logical equivalent of the PS handover to a GERAN cell in which dual transfer mode is supported as UTRAN inherently allows domain services to PS and CS domain operating in parallel.

In either case (whether dual handover mode is supported or not), there is no need for a subsequent intracellular handover to be performed (i.e. allocating resources required by the voice service to the CS domain) that follows the PS handover from the eUTRAN cell because the CS domain resources are allocated in the target GERAN / UTRAN cells as part of the legacy MT and MO voice service establishment procedures. If dual transfer mode is not supported, then the PS resources allocated by the target GERAN cell as part of the handover procedure from eUTRAN to GERAN are maintained, only, until the CS service is established, and then released. explicitly or implicitly.

If the UE 12 and the GERAN / UTRAN 14 do not both support dual transfer mode or the set of active PS services in the eUTRAN cell they do not have a delay sensitive to the point of strictly needing a PS handover for the cell change, then the UE 12 or the eUTRAN 16 could still cause a PS handover to a GERAN / UTRAN cell to minimize the delay in establishing the desired voice service in the CS domain.

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A block diagram showing the network interfaces is shown in Figure 3. User equipment 12 has circuit-switched access through a GERAN / UTRAN 14 that communicates with the CS core network 11 through an A / lu interface 28. The UE 12 also communicates with an eNodeB 33 of the eUTRAN 16. The eUTRAN 16 interfaces with the Evolved Packet Core (EPC) 18 through an S1 interface 29, as it is known for 3GPP.

In a typical circuit-switched Generic Packet Radio Services (GPRS) network, the mobility management of the PS domain is performed by a Service GPRS Support Node (SGSN), on which an interface is provided Gs between the SGSN and the MSC to provide update information on the location of the CS domain to the MSC. In an EPS network, mobility management is performed by a mobility management entity (MME) 15 of the Evolved Packet Core (EPC) 18. Thus, in order to maintain the mobility management functions of the domain of the CS in the MSC server 22, a Gs-type interface 26 is provided between the MME 15 of the CPE 18 and the MSC server 22 of the CS Core Network 11. The Gs-type interface 26 can be used for the CS domain location update procedure (usually triggered in a GERAN cell during the PS handover procedure), so that CS search messages can be sent from the server from MSC 22 to MME 15.

The presence of the Gs-type interface can be used as a trigger for the MME to determine when to perform the handover from PS to the CS core network for both MT and MO voice service request scenarios. For the case of direct MO voice service request, the presence of the Gs-type interface causes the MME to send system broadcast information informing a UE that it can generate a voice service request in the CS domain. by sending an unsolicited measurement report that only includes GERAN / UTRAN cells. For the case of indirect MO voice service request, the MME will respond to a voice service request received from the UE (through the eNodeB) by ordering a PS handover between RAT to a GERAN / UTRAN cell ( that is, instead of performing call setup procedures in the packet-switched domain). For the case of direct MT voice service request, the MME may send the eNodeB a search indicating that a handover from Inter-RAT PS to a GERAN / UTRAN cell should be performed (i.e. instead of performing procedures of call establishment in the packet-switched domain) in which case the eNodeB sends a signaling message to the UE that serves, both as a search and as a request for measurement information. Upon receiving a response to this signaling message, the eNodeB uses the provided measurement history to instruct the UE to perform a PS handover from Inter-RAT to a GERAN / UTRAN cell. For the case of indirect MT voice service request, the MME causes the search of the UE using generic search procedures (i.e. it must verify that the UE is actually available in a cell of the eUTRAN) in which the search that sent to the eNodeB does not indicate that a PS handover from Inter-RAT to a GERAN / UTRAN cell should be performed. Upon receiving a service request from the UE (via the eNodeB) in response to the paging attempt and knowing that it supports a Gs-type interface to an MSC, the MME will again realize that a handover of PS from Inter-RAT to GERAN / UTRAN and can therefore respond to the service request by ordering the eNodeB to perform a PS handover from Inter-RAT to a GERAN / UTRAN cell for that UE.

In another embodiment related to the direct case, the eNodeB, after getting a Search Response from the UE (i.e. confirming that it is present in a specific cell of the E-UTRAN), will have the authority to trigger the PS handover procedure and, consequently, send the UE a PS Handover Command. This is possible when the MME uses the Search that it sends to the eNodeB to efficiently transmit its presence awareness of the Gs-type interface.

In the 3GPP CS domain, both Location Area (LA) and Service Area (SA) are fundamental concepts used for various purposes, for example to support CS service "control" based on geographic areas. The Location Area and Service Area concepts may be intrinsically supported by the EPS and / or with a matching relationship between the LTE Tracking Area and the 2G / 3G cellular structures (ie LA and SA).

As described above, the mobility management of the EPS is provided through a mobility management entity (MME) 15. An example of mobility management is shown in figure 4 with the specific example of the network connection of a UE. The UE is provided with identifiers necessary to establish the CS voice service. The UE sends a join request to the eNodeB which results in the UE being authenticated prior to registration with the MME. While operating within LTE coverage (i.e., as long as there is no need to establish a voice service), CS Location updates can be triggered by MME 15 to MSC Server 22 using a relationship of correspondence between the LTE tracking area (TA) and the location area (LA). It should be noted that the CS binding can be embedded and that the CS Location Update procedure can either be triggered by the UE (e.g. with the LA structure visible in the broadcast) or by the MME (based on the mapping of the LTE / SAE AT structure). Once basic IP bearers are established, the identifiers (eg LAs) can be sent to the EU. The same concepts can be used when the UE is roaming to other LTE coverage areas. That is, the LTE TA update procedure may include the CS Location Update procedure.

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Before initiating a source CS voice service, the UE roams to a 2G / 3G cell using PS handover. After reaching the 2G / 3G cell, all subsequent call setup signaling is identical to an originating 2G / 3G call and the eUTRAN and EPC are not involved.

The handling of termination calls when the eUTRAN is active is shown in figure 5. The search request 51, including the International Mobile Subscriber Identity (IMSI), originates from the mSc server 22 and is sent to the MME 15 The MME 15 sends the paging request to the eNodeB 33 through the S1 interface and then the Radio Resource Control (RRC) connection can be used to extend the paging notification to the UE 12. Receiving the search notification at the UE 12 can cause measurement report information to be sent to the eNodeB 33 which then causes the eNodeB to send the UE 12 a PS handover command using that measurement report information (i.e. , the direct case of voice service establishment in the MT CS domain). The UE is moved to a 2G / 3G cell (using PS handover) prior to call setup signaling. After reaching the 2G / 3G cell, all subsequent call setup signaling is identical to that used for legacy mode operation where the terminating call in 2G / 3G is triggered when a UE is being served by a 2G / 3G cell, for example using NodeB 52 and Radio Network Controllers 53.

As is apparent to one of ordinary skill in the art, the embodiments described in this document take advantage of existing 2G / 3G mechanisms. However, there is no impact on the 2G / 3G RAN and the level of impact on the 2G / 3G core network is less with no new protocol required.

The embodiments described in this document can be understood as a cost effective "gap filler" to provide CS voice services that gives the operator a bit more time to migrate to MTSI when eUTRAN is developed.

The terms and descriptors used in this document follow the standard terminology used in the 3GPP standards for Evolved Packet Systems and Long Term Evolution. Description of features, interfaces, and behaviors that are not part of the innovative concepts are omitted for the sake of clarity.

As will be recognized by those skilled in the art, the innovative concepts described in the present application can be modified and varied in a wide range of applications. Accordingly, the scope of the subject matter of the patent should not be limited to any of the specific illustrative teachings described above, but are defined by the following claims.