KR20150028779A - Internetworking for circuit switched fallback-network initiated ussd request/notification procedure mobile-terminated location request procedure provide subscriber information procedure - Google Patents

Abstract

A method for switching a user equipment from a long term evolution system to a circuit switching system when receiving a voice call is disclosed. The method includes receiving at the IWF (Internetworking Function) network node a MAP (Mobility Application Part) USSD message identifying a user equipment (UE) originating from a USSD (Unstructured Supplementary Service Data) application, A mobile switching center (MSC); Initiating a circuit switched fallback (CSFB) by sending a paging request to the UE; Receiving a Cancel Location message associated with the UE from a Home Location Register (HLR) indicating that the UE is associated with a second MSC; Forwarding a MAP USSD message to the UE via the HLR and the second MSC; Receiving a MAP USSD response message from the UE via the HLR; And forwarding the MAP USSD response message to the USSD application.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for providing a subscriber information service in a mobile communication network, PROCEDURE}

This disclosure relates to the field of telecommunications, and more particularly to internetworking for circuit switched fallback.

Currently, Long Term Evolution (LTE) systems do not support voice calls, and thus Circuit Switched Fallback (CSFB) specified by 3GPP standards TS 23.272 is implemented for these calls do. The CS fallback function and short message system (SMS) message delivery over the CS core network are performed as described in 3GPP TS 29.018 for the interface between the Mobility Management Entity (MME) of the Evolved Packet System (EPS) and the Visitor Location Register (VLR) It is realized by reusing Gs interface mechanisms. This interface is called the SGs interface.

For example, if the network is enhanced to page the mobile via LTE radio and the mobile camped on the LTE radio receives a voice call page request over the LTE system, It will fall back to the CS radio to receive the voice call. With respect to CSFB, any active data session is either suspended or handed over to 2g / 3G packet switched (PS) access. For Mobile Originating (MO) calls, mobile devices or user equipment (UE) camped on LTE radios initiate their own fallback to originate a voice call in the CS domain. Mobiles camped on LTE radios can send or receive SMS messages without being backed out. The basic idea is to have the UE fall back to CS radio for voice calls, not VoLTE (Voice Over LTE). A new interface (called SGs) between the MME (Mobility Management Entity) and the MSC / VLR (Mobile Switching Center / Visitor Location Register) is used by the MSC to determine when the UE is connected to the Evolved Packet Core (EPC) you need to know the. The MSC / VLR is registered as normal in the Home Location Register (HLR), so that Mobile Terminating (MT) voice calls and SMS messages are routed thereto. In this case, the MO / MT SMS message is delivered via the MSC via LTE access and EPC. For the MO call, the UE is dropped back to the CS radio before making the call so that no core network changes are needed. For the MT call, the call is delivered as normal to the MSC, and the MSC pages the UE through the new SGs interface between the MME and the MSC. The UE is dropped back to the CS radio and issues a Location Update or a Page Response. The MSC completes the call. If the UE is dropped back to a different MSC than the one that issued the SGs paging, complex "roaming retry" procedures are needed to complete the call. That is, this process requires new interfaces and changes to existing nodes in each of the LTE and CS systems. A new SGs interface between the MSC in the CS core network and the MME in the EPC is needed. SGs allows the MSC to know the EPC attachment and the MO / MT SMS during the EPC connection, and also allows the MSC to page the subscriber through EPC and LTE access to the voice call. For modified nodes, the MSC requires an SGs interface and an associated state machine. The MME requires a change of the SGs interface and the associated state machine, and also requires an S3 interface to the SGSN if idle mode signaling reduction (ISR) is possible. The MSC / HLR / GMSC all need to be modified to support roaming retry, which is more likely by the CSFB.

1 is a simplified block diagram of an embodiment of a communication system for circuit switched fallback;
Figures 2A-2I are simplified block diagrams of embodiments of communication systems illustrating signaling during circuit switched fallback;
Figures 3a-3d are flow charts illustrating an embodiment of a circuit switched fallback procedure.
4 is a flow chart illustrating an exemplary method of performing circuit switched fallback.
5 is a call flow diagram illustrating one embodiment of a new network initiated USSD request procedure.
6 is a simplified block diagram of an exemplary embodiment of a communication system.
7 is a call flow diagram illustrating an embodiment of a new mobile terminated location reporting procedure (MT-LR).
Figure 8 is a call flow diagram illustrating an embodiment of providing new subscriber information for fallback to the CS procedure.

 1 illustrates an exemplary communication for exchanging user equipment (UE) in a Long Term Evolution (LTE) system with a Circuit Switched (CS) system upon receipt of a voice call; System 100 shown in FIG. For example, if the UE is camped on an LTE system and receives an indication of a mobile terminating voice call from the CS domain, the UE may initiate a call to the CS network 2G or 3G). In general, switching from an LTE network to a CS network for voice calls is referred to as Circuit Switched Fall Back (CSFB). In some implementations, the system 100 may execute the CSFB independently or without including an SGs interface on a Mobile Switching Center (MSC). In addition, the system 100 can execute the CSFB independently or without changing the existing MSC. For example, the system 100 includes a CSFB Internetworking Function (IWF) 102 (described in more detail below) that is connected to the CS network via MAP interfaces and is connected to the LTE network via the SGs interface . In doing so, the system 100 may be configured to: change at the MSC (e.g., no SGs interface at the MSC, no configuration change); Roaming retries (eg, savings in complex MSC / HLR functionality, reduced call setup delay); TA to LA mapping (e.g., all TAs can be mapped to a single LA, which may belong to the CSFB IWF); MT call bearer processing (eg no bearer trunks, cost savings); And / or the like.

At a high level, the system 100 includes, in some implementations, the CS system 104, the LTE system 106 via the networks 104 and 106, and the CSFB IWF communicatively coupled to the UE 108 102). CS system 104 includes a radio access network (RAN) 110 and a cellular core network 112, and the LTE system 106 includes an evolved UTRAN (E-UTRAN) 114 and an enhanced packet And an LTE radio access network 114, such as a core network 116, referred to as a core (Evolved Packet Core, EPC, 116). Cellular core network 112 includes GSMC 118, HLR 120, MSC / VLR 122, and SGSN 124. The EPC 116 includes an MME 126 and a Home Subscriber Server (HSS) 128. At a high level, the CSFB IWF 102 registers with the serving MSC / VLR when the UE performs an IMSI attach via the EPC 116. After registration, the GSMC 118 may receive incoming requests to end the voice call with the UE, and may also send a request for routing information to the HLR 120. [ After determining that the CSFB IWF 102 is provided as a serving MSC to the cellular core network 112, the HLR 120 may send a request for the MSRN to the CSFB IWF 102. The CSFB IWF 102 sends a request to the UE 108 via the MME 126 of the EPC 116 to fall back to the cellular system 104. In response to the request, The UE 108 may send a request to the MSC / VLR 122 via the RAN 110 to update its location, which is relayed to the HLR 120. The HLR 120 reassigns the MSC / VLR 122 to the Serving MSC and also sends a Cancel Location request to the CSFB IWF 102. The CSFB IWF 102 sends a new request for routing information to the HLR 120 and also sends the MSRN received at the PRN Ack to the GMSC 118 which uses the MSRN to forward the call to the MSC / VLR 122, where the call is complete.

Returning to a more detailed description of system 110, CSFB IWF 102 sends UE 108 to LTE system 106 in connection with receiving a mobile termination request for a voice call from cellular core network 112. [ Hardware, and / or firmware that can operate to switch from the CS system 104 to the CS system 104. [ For example, the CSFB IWF 102 may page the UE 108 to request an update location request using the HLR 120 of the cellular core network 112. By updating the location in the cellular system 104, the CSFB IWF 102 can respond to the PRN request using the MSRN assigned by the cellular system 104 during location update. In initiating the updated location, the CSFB IWF 102 may initiate the UE 108 to fall back to the CS radio for voice calls that are not voice over LTE (VoLTE). In some embodiments, CSFB IWF 102 includes an MME 126 (e. G., A base station) that, when operating as an MSC / VLR, allows CSFB IWF 102 to determine when UE 108 is connected to an EPC 116 Lt; RTI ID = 0.0 > (SGs) < / RTI > CSFB IWF 102 may include interfaces such as SGs for MME 126, MAP for HLR 120, MAP for SMSC, and / or the like. For SGs to MME 126, CSFB IWF 102 may perform standard SGs functions and / or MME 126 may identify CSFB IWF 102 as a Visitor Location Register (VLR) can do. In other words, the CSFB IWF 102 may support the SGs interface from the MME 126 in the EPC domain. In these examples, the CSFB IWF 102 may be viewed as a VLR to the MME 126. The CSFB IWF 102 operating as a VLR / MSC for subscribers in the EPC domain can interact with the SMSC in the HLR 120 via the MAP interface and also in the network 112 for SMS related procedures. CSFB IWF 102 may include "VLRs" that maintain SGs states and state machines defined in 3GPP TS 29.118. Having described the MAP for the HLR 120, the CSFB 102 may use this interface to perform location update procedures and / or call routing procedures. The MAP interface between the CSFB IWF 102 and the HLR 120 may be used for location management, subscriber management and / or call handling procedures. Describing the MAP for the SMSC, the CSFB IWF 102 may execute the MO / MT SMS procedures using a MAP Short Message (MO Short Message) and / or a MAP MT Short Message delivery. For example, the MAP interface between the CSFB IWF 102 and the SMSC may be used for mobile originated and / or mobile terminated SMS. In some implementations, the CSFB IWF 102 may operate independently or without bearer facilities (e.g., TDM trunks). The CSFB IWF 102 receives MT signaling call signaling from the HLR 120 when the CSFB IWF 102 appears as a serving MSC / VLR; Send a SGs paging request to trigger CSFB; Initiating an MT call signal to redirect the call to the new (and actual) serving MSC / VLR; And / or other functions. In connection with these processes, the UE 108 may be dropped back to the CS domain and may also perform the location update MSC / VLR 122. UE 108 may also accept the call once the CSFB IWF 102 resends the call. As mentioned above, the CSFB IWF 102, in some implementations, may itself emulate or otherwise represent itself as an element of the core network 112. For example, the CSFB IWF 102 may itself represent or otherwise represent the MSC, VLR, or other element of the cellular core network 112. The CSFB IWF 102 may be queried by the HLR 120 in the cellular core network 112 like all other MSCs if the communication node 108 acts on the MSC.

Returning to the detailed description of the other elements in system 100, LTE system 106 may include EPC 116 and E-UTRAN 114. The EPC 116 provides a connection to an external network, such as the cellular core network 112. E-UTRAN 114 includes one or more base stations, such as eNode-B (eNB) base stations, that provide wireless service (s) to UE 108. The EPC-based core network may include a Serving Gateway (SGW), an MME 126, and a Packet Gateway (PGW). The SGW may route traffic within the EPC 116. MME 155 is responsible for core network mobility control, connection to UE 108's core network, and contact maintenance with idle mode UEs. The PGW is responsible for enabling traffic to / from the Internet. The PGW may assign IP addresses to the UEs 108. [

An LTE based wireless communication system has network interfaces defined between system elements. The network interfaces include a Uu interface defined between the UE and the eNB, an S1U user-plane interface defined between the eNB and the SGW, an S1C control plane defined between the eNB and the MME (also known as S1-MME) Interface, and S5 / S8 interface defined between SGW and PGW. It should be noted that the combination of S1U and S1C is often simplified to "S1".

The MME 126 is a control-node for the LTE access network. MME 126 is responsible for UE 108 tracking and paging procedures, including retransmissions. The MME 126 handles the bearer activation / deactivation process and is also responsible for the selection of the SGW for the UE 108 upon initial connection and intra-LTE handover. The MME 126 also authenticates the user by interacting with the HSS 124. The MME 126 also generates temporary identities to the UEs or allocates them, and terminates the Non-Access Stratum (NAS) signal. The MME 126 checks the authentication of the UE 108 to camp on the service provider's Public Land Mobile Network (PLMN) and also enforces UE roaming restrictions. The MME 126 is a termination point in the network for ciphering / integrity protection for NAS signals and handles security key management. A lawful interception of the signal is also supported by the MME 126. The MME also provides LTE and control plane functionality for mobility between 2G / 3G access networks with an S3 interface terminating at the MME 126 from the SGSN 130. The MME 126 also terminates the S6a interface towards the home HSS 128 for roaming UEs.

The SGW routes and also delivers user data packets and simultaneously acts as a mobility anchor for the user plane during inter-eNB handover and anchor for mobility between LTE and other 3GPP technologies (S4 Terminating the interface and relaying traffic between the 2G / 3G systems and the PDN GW). For idle UEs, the SGW terminates the downlink data path and triggers paging when downlink data arrives at the UE 108. [ The SGW manages and stores parameters of UE contexts, e.g., IP bearer service and network internal routing information. The SGW also performs replication of user traffic in the case of legitimate interception. The PGW provides a connection to the UE 108 to external packet data networks by becoming an entry point for traffic to the UE 108. [ UE 108 may concurrently access more than one PGW for accessing multiple packet data networks. The P-GW performs policy enforcement, packet filtering for each user, support coordinator, legitimate eavesdropping, and packet screening. PGW also provides an anchor for mobility between 3GPP and non-3GPP technologies, such as WiMAX and 3GPP2 (CDMA 1X and EvDO). The SGW or PGW according to an embodiment provides deep packet inspection and may be used to provide advertisements to users on a per subscriber basis as described above for a chassis implementing SGW or PGW .

The cellular core system 104 typically includes various switching elements, gateways, and service control functions to provide cellular services. The cellular core system 104 often provides these services through a number of cellular access networks (e.g., RAN), and also interfaces the cellular system with other communication systems, such as EPC 116. In accordance with cellular standards, the cellular core system 104 includes a circuit-switched (or voice-switched) unit for processing voice calls and a packet-switched (or voice-switched) circuit for supporting data transmission such as e-mail messages and web browsing Data exchange) section. The circuit switching unit is connected to the MSC / VLR 122 that exchanges or connects telephone calls between the cellular access system 106 and the PSTN 104 or other network, between cellular core networks, or otherwise. . The MSC / VLR 122 may support only a single media stream (e.g., a single TDM channel for a standard A-interface, a single RTP stream for AoIP) towards the RAN 110. This single media stream may be used for supplementary services, including multiple calls to / from the mobile, such as call waiting. In other words, multiple calls from / to GSM mobile share a single media connection on the access interface of the MSC.

Cellular core system 104a also includes subscriber data received from HLR 120 using HLR 120 and a wireless communication method for maintaining "permanent" subscriber data and up-to-date information about the location of UE 108 (And / or SGSN) for "temporarily" The cellular core system 104 also includes an authentication, authorization, and accounting (AAA) 108 that performs authentication, authorization, and accounting functions for the UE 108 that is operable to access the cellular core system 104. ). Although the description of core system 104 is described with respect to a GSM network, core system 104 may include other cellular radio technologies such as UMTS, CDMA, and other technologies without departing from the scope of this disclosure.

The RAN 110 provides a radio interface between the cellular core system 104a and the mobile device 102a that provides real-time voice, data, and multimedia services (e.g., calls) to the UE 108. [ In general, the RAN 110 conveys air frames over radio frequency (RF) links. In particular, RAN 110 is translated into physical link based messages between air frames for transmission over cellular core system 104a. The RAN 110 may comprise one or more of the following radio interface standards, such as GSM access, UMTS access, Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA) , General Packet Radio Service (GPRS), Enhanced Data Rates for GSM Evolution (EDGE), or proprietary air interfaces. Users may subscribe to the RAN 110 to receive, for example, cellular telephone services, Global Positioning System (GPS) services, XM radio services, and the like.

The RAN 110 may include a base station (BS) connected to a base station controller (BSC) 132. The BS receives and transmits air frames within the geographic area of the RAN 110 (i.e., transmitted by the UE 108) and also communicates with other UEs connected to the cellular core system 104. Each BSC 132 is associated with one or more BSs 114 and controls the associated BSs 114. For example, the BSC 132 may perform functions such as handover, cell configuration data, control of RF power levels, or other suitable functions for managing radio resources and for routing signals to and from the BS Lt; / RTI > The MSC / VLR 122 may be coupled to the BSC 132 via a standard interface, such as an A-interface. While the elements of RAN 110 are described for GSM networks, RAN 110 may include other cellular technologies such as UMTS, CDMA, and / or others. For UMTS, the RAN 110 may include a Node B and a Radio Network Controller (RNC).

Turning to a more detailed description of the elements, the UE 108 includes an electronic device that is operable to receive and transmit wireless communications with the system 100. Herein, the UE 108 may be a cellular telephone, data telephones, pagers, portable computers, SIP phones, smart phones, personal data assistants (PDAs) One or more processors in other devices, or any other suitable processing device capable of communicating information using cellular radio technology. In the illustrated implementation, UE 108 may transmit in one or more cellular bands. In this case, the messages sent and / or received by the UE 108 may be based on cellular radio technology. There may be any number of UEs 108 communicatively coupled to the cellular access network 110. In general, the UE 108 may transmit voice, video, multimedia, text, web content, or other user / customer-specific content. In short, the UE 108 communicates with the mobile core system 104a via EPC 116 via RAN 110 or E-UTRAN 114 to generate, respond to, or otherwise make a request.

In some aspects of operation, the system 100 may be configured to perform the following operations: from a Home Location Register (HLR) in the CS network for a Mobile Station Roaming Number (MSRN) Receiving a Provide Roaming Number (PRN) request; Send a request to the UE via the Mobility Management Entity (MME) in the LTE system to fall back to the CS system; Receiving a Cancel Location (CL) request from the HLR in connection with the location of the UE being reassigned to another MSC; Sending a Send Routing Information (SRI) request to the HLR, at least in response to the CL request; Receive the MSRN from the MSC via the HLR; Using the received MSRN, a PRN acknowledgment (PRN Ack) is sent to the HLR such that the call is terminated to the UE using the MSRN; And / or the like.

2A-2I are systems 200-280 illustrating signals for implementing a CSFB in accordance with some embodiments of the present disclosure. Referring to FIG. 2A, the GMSC 118 receives a signal 202 indicating a request to terminate a voice call to the UE 108. As shown in FIG. Referring to FIG. 2B, system 210 shows signal 212 requesting an MSRN for UE 108. In particular, the GMSC 118 sends a Provide Roaming Number (PRN) request to the HLR 120, and the HLR 120 also sends a PRN request to the CSFB IWF 102 (as the MSC / VLR for the UE 108) . Referring to FIG. 2C, system 220 illustrates a signal 222 illustrating paging requesting UE 108 to update its location with HLR 120. In FIG. In particular, the CSFB IWF 102 sends the paging to the MME 126 and, in turn, the MME 126 sends the paging to the UE 108 via the E-UTRAN 114. Referring to FIG. 2d, a system 230 depicts a UE 108 that returns communications from an E-UTRAN 114 to a RAN 110. In FIG. Referring to FIG. 2E, the system 240 shows a signal 242 requesting a location update from the cellular core network 112. In particular, the UE 108 sends an update request to the HLR 120 via the BSC 132 and the MSC / VLR 122. Referring to FIG. 2F, system 250 shows signal 252 indicating that UE 108 is registered with another MSC. In particular, the HLR 120 updates the registration of the UE 108 with the MSC / VLR 122 and also sends a Cancel Location (CL) request to the CSFB IWF 102. Referring to FIG. 2G, system 260 shows a signal 262 requesting a current MSRN from HLR 120. In particular, the CSFB IWF 102 sends an SRI request to the HLR 120 using the MSISDN identified in the PRN request previously received from the GMSC 118 via the HLR 120. 2H, system 270 illustrates signal 272 for retrieving the MSRN and sending the MSRN to the CSFB IWF 102. As shown in FIG. In particular, the HLR 120 identifies the MSC / VLR 122 as a VMSC and retrieves the current MSRN from the MSC / VLR 122. 2i, system 280 shows signal 282 that sends a current MSRN to GMSC 118 via HLR 120 to complete a mobile inbound call to UE 108. As shown in FIG.

3A-3D illustrate a call flow 300 for executing a CSFB in accordance with some implementations of the present disclosure. In the call flow 300, the UE 108 performs a Combined RA / LA Update procedure if the Location Area Update or the LA of the new cell is different from that stored in the UE 108 . CSFB IWFs are assigned to LAIs that are mutually exclusive with those used in 2G / 3G space, which forces the UE 108 to always initiate a Location Area Update. In the idle mode, the MME 126 sends a paging request to the eNodeB 114, which in turn sends the request to the UE 108. The MME 126 receives an extended service request from the UE 108 and transmits a service request to the CSFB IWF 102. In an active mode, the MME 126 sends a CS Paging request directly to the UE 108 when it has a configured S1 connection. The MME 126 immediately sends a Service Request to the CSFB IWF 102 after sending a Paging Request to the UE 108. [ In some implementations, the CSFB IWF 102 may set the Service Indicator to a "CS Call Indicator" in an SGAP-PAGING-REQUEST message. The CSFB IWF 102 may identify this when receiving a MAP PRN message from the HLR 120. The CSFB IWF 102 may not include the following attributes in the SGAP-PAGING-REQUEST because the following attributes may not be available (e.g., an LCS Customer Identity ), LCS indicator (Indicator)). The MSC / VLR 122 may not receive a Service Request message from the CSFB IWF 102. 3GPP TS 23.272 states that a Service Request message can be used as a trigger to notify a calling party that a call is in progress and to start a CFNRy timer. CSFB IWF 102 may follow standard procedures to inform call progress. The call progress may be triggered for each normal procedure once the UE is fallback to the GERAN / U-TRAN and the call is set there. Once the CSFB IWF 102 has received an SGsAP-SERVICE-REQUEST from the MME 122, the CSFB IWF 102 may send subsequent paging retries. The 2G / 3G BSC / MSC may not receive a paging response from the UE 108 because it always performs a Location Area Update after it has moved from the E-UTRAN 114. [ The HLR 120 processes the MAP UPDATE LOCATION from the new MSC / VLR 122 and sends a MAP CANCEL LOCATION to the previous MSC (CSFB IWF 102 in this case) Lt; / RTI > The CSFB IWF 102 sends a MAP UPDATE LOCATION procedure (including one or more MAP INSERT SUBSCRIBER DATA messages) procedures before completing the MAP CANCEL LOCATION I can not wait. The MAP UPDATE LOCATION procedures from the new MSC / VLR 122 at the HLR 120 and the SRI mapping (MAP SRI) procedures from the CSFB IWF 102 may occur simultaneously or at least in association with each other. The CSFB IWF 102 may not know when the UPDATE LOCATION is completed and may not wait to send an SRI mapping (MAP SRI) to the HLR 120. The trigger that causes the CSFB IWF 102 to send an SRI mapping (MAP SRI) may be the receipt of a MAP CANCEL LOCATION. The HLR 120 may wait until the MAP UPDATE LOCATION from the new MSC / VLR 122 is completed before processing the SRI mapping (MAP SRI) message from the CSFB IWF 102. Basically, the CSFB IWF 102 may wait for the MAP UPDATE LOCATION to complete before sending a PRN mapping (MAP PRN) message to the new MSC / VLR 122. The CSMT flag may not be supported by the 2G / 3G MSC / VLR and therefore the CSMT flag may ignore the parameter if received from the UE 108 in a LOCATION UPDATE message. For this reason, the MSC / VLR 122 can release the SCCP connection to the user after completion of the location area update procedures. The HLR may send both the IMSI and the MSISDN to the CSFB IWF 102 in the PRN mapping (MAP PRN) message. Upon receiving an erroneous response to an SRI mapping (MAP SRI) request, the CSFB IWF 102 may relay the same to the HLR 120 in the PRN response for an initial call. CSFB IWF 102 may include a T-CSI Suppression (S-CSI) parameter in an SRI mapping (MAP SRI) request sent towards HLR 120. CSFB IWF 102 may substantially ignore all service indications from HLR 120 in an SRI mapping (MAP SRI) response. When an inter-RAT handover from the E-UTRAN 114 to UMTS / GSM can be supported (i.e., handover of an active packet session), the MME 126 transmits It can interact directly with the SGSN. The CSFB IWF 102 may not be included in these procedures. The CSFB architecture provides additional automatic access delays (" uplink ") over standard CSFB attempts by invoking a Location Area Update procedure each time a subscriber moves from the E-UTRAN 114 to the UTRAN / post dial delay can be introduced. The LI for the MT call can be processed in the 2G / 3G MSC / VLR 122. For example, roaming retry procedures may not be needed in this CSFB IWF architecture.

In some implementations, the MME 126 may send an SGsAP-PAGING-REJECT message to the CSFB IWF 102 and may also send the corresponding action in the CSFB IWF. If the UE 108 is known and is considered to be an IMSI connected for the EPS service and "SMS only ", then the MME 126 sends a" cause- SGSAP-PAGING-REJECT " message indicating " the call is rejected by the user ". The CSFB IWF 102 may send a PRN response mapping (MAP PRN RESPONSE) to the HLR 120 with a User Error set to "Facility Not Supported". If the UE 108 is known and is marked as an IMSI connected (implicitly or explicitly) for the IMSI or non-EPS service connected for the EPS service, i.e. if the SGs association status is SGs-NULL, the MME 126 ) Is defined as a detach circumstance ("disconnected IMSI for EPS service", "disconnected IMSI for non-EPS service" or "non-EPS service") in the cause information element of SGs SGSAP-PAGING-REJECT) message indicating an " implicitly disconnected IMSI "). The CSFB IWF 102 may send a PRN response mapping (MAP PRN RESPONSE) to the HLR 120 with a User Error set to an "Unidentified Subscriber ". If the UE 108 is not known and the "MME Reset" is set to "false ", then the MME 126 sends an" IMSI Unknown SGSAP-PAGING-REJECT " message indicating " unknown ". The CSFB IWF 102 may send a PRN Response Mapping (MAP PRN RESPONSE) to the HLR 120 with a User Error set to "Unknown Subscriber ". If the UE 108 is not known and is considered to be an IMSI connected for EPS service and "SMS only" with "MME Reset" set to " The UE 126 may return an SGsAP-PAGING-REJECT message indicating a "mobile incoming CS fallback call rejected by the user" in the SGs cause information element. The CSFB IWF 102 may send a PRN response mapping (MAP PRN RESPONSE) to the HLR 120 with a User Error set to "Facility Not Supported". If the UE 108 is marked as unreachable, as indicated by a Paging Proceed Flag set to "false, " the MME 126 sends an SGs cause information element (SGsAP-UE-UNREACHABLE) message indicating "unreachable" in the SGSAP-element. When the CSFB IWF 102 receives the SGsAP-UE-UNREACHABLE message from the MME 126, the CSFB IWF 102 receives a user error (User (User) set to "no subscriber reply" Error) and a PRN Response Mapping (MAP PRN RESPONSE) message. The CSFB IWF 102 may transition to the appropriate SGs state based on the rejection cause in the Paging Reject message. If the UE 108 fails to find the GERAN / UTRAN radio at the CS fallback attempt, the call attempt may fail. In this scenario, the HLR 120 may time out waiting for a PRN response from the CSFB IWF 102.

4 is a flow diagram 400 illustrating an exemplary method of implementing a CSFB in accordance with some implementations of the present disclosure.

The method 400 begins at step 402 where a PRN request is received from the HLR. For example, in FIG. 1, the CSFB IWF 102 may receive a PRN request identifying the MSISDN of the UE 108 from the HLR 120. In step 404, the IMSI and MSISDN identified by the PRN request are stored. In the example, the CSFB IWF 102 may store the IMSI and MSISDN identified by the PRN request. Next, at step 406, the UE is paged through the MME in the LTE system to update the location via the CS network. As an example, the CSFB IWF 102 may send the page to the MME 126 for the UE 108. In connection with updating the location, a cancel location (CL) request is received from the HLR based on assigning a new MSC to the UE in step 408. [ The HLR 120 may send a CL request to the CSFB IWF 102 based on the HLR 120 that assigns the MSC / VLR 122 to the UE 108. [ In step 410, the stored MSISDN may be retrieved from memory. Returning to the example, the CSFB IWF 102 may retrieve the MSISDN from the memory that was identified in the PRN request. Next, at step 412, an SRI mapping (MAP SRI) request is sent to the HLR containing the previously received MSISDN. In the example, the CSFB IWF 102 sends an HLR 120 an SRI mapping (MAP SRI) request containing the MSISDN identified in the PRN request. At step 414, a MAP SRI Ack is received identifying the UE ' s current MSRN. Next, at step 416, a PRN acknowledgment (PRN Ack) identifying the current MSRN is sent to the HLR. Returning again to the example, the CSFB IWF 102 may send a PRN acknowledgment (PRN Ack) containing the current MSRN of the UE 108 to the HLR 120 to terminate the call to the UE 108 have.

5 is a call flow diagram illustrating an embodiment of a new network initiated mobile inbound USSD request / notification procedure. The USSD is a protocol used by GSM cellular phones to communicate with the service provider's USSD server. In this scenario, the MSC / VLR performing the fallback is different from the MSC / VLR when the UE first falls back to the CS. That is, the MSC is changed at the time of fallback during the MT / USSD (Unstructured Supplementary Service Data) request / notification procedure. The IWF initiates a fallback as in the case of the MT call and then acts as a USSD server and forwards the USSD request / notification to the UE via the HLR and the new MSC. The call flow shown in Figure 5 is equally applicable to network initiated MT USSD notifications as well.

Focusing on the call flow inside the box, the IWF acts as a USSD server and sends a MAP (Mobile Applications Part) USSD request to the HLR. In response, the HLR sends a USSD request to the new MSC / VLR. The new MSC / VLR conveys the USSD request to the UE as per standard CS procedures and sends the response received from the UE to the HLR. The USSD Ack is sent to the HLR by the MSC / VLR in response to receiving the UE's response. The HLR relays the response to the IWF, which in turn relays the USSD response to the HLR. The USSD Ack is sent to the HLR by the MSC / VLR in response to receiving the UE's response. The HLR relays the response to the IWF and this IWF further relays the USSD response to the HLR. The HLR then sends the USSD response to the USSD server or, optionally, to the USB application.

6 is a simplified block diagram of an exemplary embodiment of a communication system for the new Mobile Incoming Location Report (MT-LR) procedure shown in FIG. 7 and described below. Figure 6 is similar to Figure 1, described in detail below. As further shown in FIG. 6, the GMLC 119 communicates with the IWF 102 via a 3GPP specific MAP-based Lg interface.

7 is a call flow diagram illustrating an embodiment of a new Mobile Incoming Location Report (MT-LR) procedure. As before, in this scenario, the MSC / VLR performing the fallback is different from the MSC / VLR when the UE first falls back to the CS. That is, the MSC changes at the time of fallback during the MT-LR procedure. The IWF initiates a fallback to the CS as in the case of the MT call. Once the fallback is complete, the IWF acts as a GMLC and routes the location query to the new MSC by obtaining a new MSC address from the HLR.

Focusing on the call flow portion within the box, the IWF sends a MAP SRI-LCS (Request Routing Information-Location Services) request to the HLR. The request may be based on an International Mobile Subscriber Identity (IMSI) or a Mobile Station International Subscriber Directory Number (MSISDN), depending on what was received in the Provide Subscriber Location (PSL) request from the Gateway Mobile Location Center (GMLC) The subscriber can be identified. In response, the HLR sends a response to the IWF that includes the network node number (identifying the new MSC). The IWF relays the MAP PSL received from the GMLC to the NW node number returned by the HLR. UE location procedures as specified in 3GPP TS 23.271 are performed. The MSC / VLR returns a MAP PSL response to FvVF. The IWF then relays the PSL response to the GMLC.

8 is a call flow diagram illustrating an embodiment of providing new subscriber information for fallback to a CS procedure. The MAP is a procedure commonly used in the CS network in which the Provide Subscriber Information (PSI) is queried so that the VLR provides the subscriber location. As before, in this scenario, the MSC / VLR performing the fallback is different from the MSC / VLR when the UE first falls back to the CS.

Focusing on the call flow portion within the box, the IWF initiates a CS fallback as in the case of an MT call, then assumes the role of a GSM Service Control Function (gsmSCF) upon receipt of a Cancel Location from the HLR, MAP Anytime Interrogation (ATI) message to the HLR requesting the same set of information mentioned in the MAP PSI Request message. The information in the response of the MAP Anytime Interrogation message is then copied into the response of the MAP PSI Request message and then sent to the HLR to complete the procedure.

The features of the invention which are believed to be novel are set forth with particularity in the appended claims. Variations, variations, and modifications to the above-described exemplary embodiments will, however, become apparent to those skilled in the art. The drain assembly described herein thus covers such variations, variations and modifications, and is not limited to the specific embodiments described herein.

Claims (3)

In the method,
The method comprising the steps of: receiving, at an IWF (Internetworking Function) network node, a MAP (Mobility Application Part) USSD message identifying a user equipment (UE) originating from a USSD (Unstructured Supplementary Service Data) application, Associated with a Mobile Switching Center (MSC);
Initiating a Circuit Switched Fallback (CSFB) by sending a paging request to the UE;
Receiving a Cancel Location message associated with the UE from a Home Location Register (HLR) indicating that the UE is associated with a second MSC;
Forwarding the MAP USSD message to the UE via the HLR and the second MSC;
Receiving a MAP USSD response message from the UE via the HLR; And
Forwarding the MAP USSD response message to the USSD application
≪ / RTI > In the method,
At an IWF (Internetworking Function) network node, a Mobility Application Part transport routing information-location service (hereinafter referred to as " Mobility Application Part ") that identifies a user equipment (UE) originating from a Gateway Mobile Location Center (SRI-LCS) message, wherein the UE is associated with a first mobile switching center (MSC);
Initiating a Circuit Switched Fallback (CSFB) by sending a paging request to the UE;
Receiving a Cancel Location message associated with the UE from a Home Location Register (HLR) indicating that the UE is associated with a second MSC;
Forwarding the SRI-LCS message to the UE via the HLR and the second MSC;
Receiving an SRI-LCS response message from the HLR;
Transmitting a Provide Subscriber Location (PSL) message to the second MSC;
Receiving a MAP PSL response message from the second MSC; And
And transmitting the MAP PSL response message to the GMLC
≪ / RTI > In the method,
In an IWF (Internetworking Function) network node, a Mobility Application Part Provide Subscriber Information (MAP PSI) that identifies a user equipment (UE) originating from a Home Location Register (HLR) Receiving a message, the UE being associated with a first mobile switching center (MSC);
Initiating a Circuit Switched Fallback (CSFB) by sending a paging request to the UE;
Receiving from the HLR a Cancel Location message associated with the UE indicating that the UE is associated with a second MSC;
Transmitting a MAP Anytime Interrogation (ATI) message to the UE via the HLR and the second MSC;
Receiving a MAP ATI response message from the HLR; And
Transmitting the MAP ATI response information to the HLR in the MAP PSI response message
≪ / RTI >

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