KR102129901B1 - Mobile communication system and method for circuit switched fallback - Google Patents

Abstract

A mobile communication system including a Long Term Evolution (LTE) network connected to a plurality of Circuit Switched (CS) domain operator networks and providing a Circuit Switched FallBack (CSFB) network includes an eNodeB that receives a connection request from a terminal; And carrier identification information for a terminal, a table matching a tracking area (TA) and a location area (LA), receiving a connection request from an eNodeB, and referring to the table, the operator identification information of the operator to which the terminal is subscribed and the terminal The MSC in charge of the LA corresponding to the currently located TA includes a MME (Mobility Management Entity) that requests a location update for the terminal.

Description

Mobile communication system and method supporting circuit-switched fallback {MOBILE COMMUNICATION SYSTEM AND METHOD FOR CIRCUIT SWITCHED FALLBACK}

The present invention relates to a circuit switched fallback (CSFB), and more particularly, the present invention relates to a system and method for supporting circuit switched fallback in an LTE network connected to each circuit network operated by a plurality of operators.

Voice service of LTE (Long Term Evolution) network, which provides conventional data service, generally used a self-network to perform circuit switching fallback within a single operator, and the 3GPP standard only considers CSFB as a network operated by a single operator. have. Accordingly, when a single LTE network is used by multiple operators, the base station and the MME do not know which circuit network to use for the CSFB even if the CSFB is attempted by the network operated by each operator.

Korean Patent Publication No. 10-2013-0035143

The present invention is to provide a mobile communication system providing a CSFB in a situation where a plurality of CS domain operator networks and a single LTE network are connected.

According to an aspect of the present invention, in a mobile communication system including a Long Term Evolution (LTE) network connected to a plurality of Circuit Switched (CS) domain operator networks and providing a Circuit Switched FallBack (CSFB) network, a connection request from a terminal ENodeB for receiving; And a table matching carrier identification information, a tracking area (TA), and a location area (LA) for the terminal, receiving the connection request from the eNodeB, referring to the table, and referring to the table. A mobile communication system is provided that includes identification information and an MME that requests a location update to the MS to the MSC in charge of the LA corresponding to the TA where the terminal is currently located.

The MME transmits a paging request to the eNodeB when a paging request according to an outgoing call request from another terminal is received from the MSC, and the eNodeB includes nodeB frequency information corresponding to the MSC according to the paging request. By sending an access message to the terminal, the terminal can be handed over from the eNodeB to the NodeB.

When the MME transmits the paging request to the eNodeB and receives a message requesting the CSFB from the terminal, the MME transmits the SPID in which the operator identification flag is inserted in a predetermined unused bit to the eNodeB, and the eNodeB is the An access message including frequency information corresponding to the operator identification flag included in the SPID may be transmitted to the terminal.

The MME performs an authentication process according to the connection request, and extracts the SPID from a message received from a Home Subscriber Server (HSS) during the authentication process.

According to another aspect of the present invention, a mobile communication system including a Long Term Evolution (LTE) network connected to a plurality of Circuit Switched (CS) domain operator networks and providing a Circuit Switched FallBack (CSFB) network supports CSFB. In step, the eNodeB receives a connection request from the terminal and transmits it to the Mobility Management Entity (MME); Generating, by the MME, a table in which operator identification information for the terminal, a tracking area (TA), and a location area (LA) are matched; And the MME requesting a location update for the terminal to the MSC in charge of the LA corresponding to the TA where the terminal is currently located and the operator identification information of the operator to which the terminal is subscribed, referring to the table. Methods of support are provided.

The CSFB support method includes: the MME receiving a paging request according to an outgoing call request from another terminal from the MSC; Transmitting, by the MME, a paging request to the eNodeB; And transmitting, by the eNodeB to the terminal, an access message including frequency information of the NodeB corresponding to the MSC according to the paging request, so that the terminal is handed over from the eNodeB to the NodeB.

After the MME sends a paging request to the eNodeB, when the MME receives a message requesting a CSFB from the terminal, transmitting the SPID in which the operator identification flag is inserted into a predetermined unused bit to the eNodeB. The method further includes, wherein the eNodeB transmits an access message including frequency information of the NodeB corresponding to the MSC to the terminal according to the paging request, so that the terminal is handed over from the eNodeB to the NodeB. The eNodeB may be a step of transmitting an access message including frequency information corresponding to the operator identification flag included in the SPID to the terminal.

In the CSFB support method, after the eNodeB receives the connection request from the terminal and transmits it to the MME, the MME performs an authentication process according to the connection request, and a message received from the home subscriber server (HSS) during the authentication process It may further include the step of extracting the SPID from.

As described above, according to the present invention, it is possible to provide circuit switched fallback for each circuit network operated by a plurality of operators connected to a single LTE network.

1 is a block diagram illustrating a mobile communication system according to an embodiment of the present invention.
2 is a flowchart illustrating a terminal access (Attach) process for providing circuit switched fallback in a mobile communication system according to an embodiment of the present invention.
3 is a call processing flow diagram illustrating a process before a terminal is handed over when a mobile communication system according to an embodiment of the present invention is called by an originating terminal to a terminal in an idle state.

The present invention can be applied to various changes and can have various embodiments, and specific embodiments will be illustrated in the drawings and described in detail through detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

In addition, in this specification, when one component is referred to as “transmitting” a signal to another component, the one component may be directly connected to the other component to transmit a signal, but there is a particularly opposite description. It should be understood that unless otherwise, it may be possible to transmit a signal through another component in the middle.

1 is a block diagram illustrating a mobile communication system according to an embodiment of the present invention.

Referring to FIG. 1, when a user equipment (UE) 100 uses a data service, it connects to a Long Term Evolution (LTE) network 200 and provides a CS service (eg, voice service, video, of course). Service, Short Message Service (SMS), LoCation Services (LCS), Unstructured Supplementary Service Data (USSD), first operator network 110 and UTS (Circuit Switched) network of UTRAN (UMTS Terrestrial Radio Access Network) 2 Connect to the operator network 120. In this way, the mobile communication system includes an LTE network 130 that cannot cope with circuit switched communication and a UTRAN network such as WCDMA/GSM that can cope with circuit switched communication.

Here, the terminal 100 is a terminal that supports CSFB (Circuit Switched Fallback).

CSFB is a first operator network 110 when a mobile originate (MO) call or a mobile termination (MT) call occurs while the terminal 100 in service in the LTE cell region is in the LTE cell. Or it is a service that provides a CS service by handing over the terminal 100 to the second operator network 120.

The LTE network 130 is a network that supports only the packet switch (PS) method, and is connected to the first operator network 110 and the second operator network 120 to the terminal 100 joined to each operator network. Provide mobile communication services.

The LTE network 130 includes an eNodeB 132, a Mobility Management Entity (MME) 134, and a Home Subscriber Server (HSS) 136.

The eNodeB 132 is a base station device of the LTE wireless access network, and provides a paging request for CSFB and a direct connection function to a target cell capable of CS service.

The HSS 136 stores subscriber information including a subscriber profile ID (SPID). In addition, the HSS 136 may perform an authentication process by receiving a subscriber authentication request message in association with the MME 134 and transmit an authentication information response message including an SPID to the MME 134.

The MME 134 stores a mapping table in which a tracking area (TA) and a location area (LA) are mapped. At this time, the general mapping table shown in Table 1 maps only TA and LA, and the conventional MME determines the LA corresponding to a specific TA by referring to the mapping table, and the terminal 100 connects to the CS network corresponding to the LA. CSFB can be performed as much as possible.

TA LA TA1 LA1 LA2

However, when a plurality of carrier networks 110 and 120 are connected to the LTE network 130, there may be a plurality of LAs mapped to a specific TA, and which of the plurality of LAs should CSFB be made through the MSC corresponding to the LA? Cannot be judged by the conventional MME.

The MME 134 according to an embodiment of the present invention stores a mapping table mapping carrier network identification information, TA and LA. That is, the MME 134 may store a mapping table according to Table 2 below.

Business network identification information TA LA 1st company identification flag TA1 LA1 Second carrier identification flag TA1 LA2

At this time, the business network identification information is preset identification information capable of identifying each business network.

The MME 134 may proceed with the CSFB according to the TA in which the terminal 100 is located and the LA mapped with the operator identification flag of the operator network to which the terminal 100 is located by referring to the mapping table as shown in Table 1.

In addition, the MME 134 may insert a carrier identification flag into a predetermined bit among bits set as an unused bit of the SPID and transmit it to the eNodeB 132. For example, the MME 134 may transmit the Initial Context Modification Request including the SPID with the operator identification flag inserted to the eNodeB 132.

In addition, the eNodeB 132 receives and stores the SPID from the MME 134, and when CSFB is triggered later, inserts frequency information corresponding to the operator identification flag included in the SPID into the RRCConnection Release Message, and sends it to the terminal 100 RRCConnection Release Message can be transmitted. Accordingly, the terminal 100 attempts handover to the NodeB of the carrier network to which the terminal 100 is subscribed according to the frequency information included in the RRCConnection Release Message. If the eNodeB 132 does not have the SPID with the operator identification flag inserted, the eNodeB 132 should include the frequency information of all operator network NodeBs corresponding to the location of the terminal 100 in the RRCConnection Release Message. Accordingly, a delay occurs as the terminal 100 attempts handover according to each frequency information. Therefore, the mobile communication system according to an embodiment of the present invention can prevent additional delays by allowing the terminal 100 to attempt handover only to the NodeB of the carrier network to which it is subscribed.

The first operator network 110 and the second operator network 120 are networks that support both circuit switching (CS) and packet switching methods, including NodeB (112, 122), SGSN (114, 124), and MSC (Mobile Switching Center, Exchange) (116, 126).

Here, NodeB (112, 122) is a wireless access network in the first operator network 110 and the second operator network 120, is based on ATM (Asynchronous Transfer Mode), the terminal 100 and the mobile communication core network (Core Network) ) To transfer data and control information.

The MSCs 116 and 126 are connected to the MME 134 to provide a location update function of the terminal 100 to support CSFB.

The communication interfaces used in each path from the terminal 100 via the NodeB 112, SGSN 114, and MSC 116 are described in detail in the known 3GPP standard, and thus, in this specification, general communication interfaces are used. Detailed description will be omitted.

2 is a flowchart illustrating a terminal attach (Attach) process for providing circuit switched fallback in a mobile communication system according to an embodiment of the present invention.

Referring to FIG. 2, in step 210, the terminal 100 transmits an Attach Request to the MME to the MME 134.

In step 220, the attach procedure including the authentication and location update process of the terminal 100 is performed. At this time, according to the LTE standard of 3GPP, the Attach Procedure is known to include authentication, location update, Context Setup, and Modify Bearer procedures corresponding to the LTE network, and step 220 corresponds to the location update procedure of the LTE standard This can be done. Therefore, the details of the LTE standard authentication and location update process are well known, and thus detailed description will be omitted. At this time, the MME 134 may receive an Authentication Information Answer message including subscriber information from the HSS 136 during the authentication process defined in the standard, and extract the SPID included in the subscriber information.

In step 230, the MME 134 requests a location update to the MSC corresponding to the LA corresponding to the TA in which the terminal 100 is located among the LAs of the carrier network to which the terminal 100 has joined by referring to the table according to Table 2 (Location Update) Request). For example, when the terminal 100 is located in TA1 and is a terminal receiving the service of the first operator network, the MME 134 is an operator identification flag corresponding to the first operator and an MSC corresponding to LA1 matching TA1. A location update request can be sent to (116).

In step 240, the MSC 116 performs a location update process of the operator network to which the terminal 100 has subscribed. At this time, the location update process of the operator network, which is the CS domain, is designated as a standard and is known, so detailed description will be omitted.

In step 250, the MSC 116 transmits the Location Update Accept to the MME 134 upon completion of the location update.

In step 260, a context setup and modify bearer process according to the LTE standard is performed.

Therefore, in the mobile communication system according to an embodiment of the present invention, the terminal 100 is joined in a situation where a plurality of CS domain operator networks and a single LTE network are linked by using a table in which the operator identification flags, TAs, and LAs are matched A connection process may be performed to the CS domain provider network.

3 is a call processing flow diagram illustrating a process before the terminal 100 is handed over when the originating terminal originates from the idle terminal 100 in the mobile communication system according to an embodiment of the present invention.

Referring to FIG. 3, in step 310, a paging signal is received according to a call connection request from an originating terminal, and the MME 134 transmits a paging signal to the eNodeB 132.

In step 320, the eNodeB 132 transmits a paging signal to the terminal 100, receives a paging response from the terminal 100, and sends an Initial UE Message (Extended Service Request) to the MME 134.

In step 330, the MME 134 inserts an operator identification flag into a bit previously specified in the SPID.

In step 340, the MME 134 sends an Initial Context Modification Request to the eNodeB 132 indicating that the CSFB for the terminal 100 is required. At this time, the Initial Context Modification Request may include an SPID including a business identification flag.

In step 350, the eNodeB 132 extracts and stores the SPID included in the Initial Context Modification Request.

In step 360, the eNodeB 132 transmits an Initial Context Modification Response to the MME 134.

In step 370, the eNodeB 132 performs a bearer modification (Modify Bearer) process, and then transmits a UE Context release request to the MME 134 indicating that the CSFB is triggered.

In step 380, the MME 134 transmits a UE Context release Command requesting the CSFB to proceed to the MME 134.

In step 390, the eNodeB 132 transmits an RRCConnection Message including frequency information corresponding to the operator identification flag included in the SPID to the terminal 100. At this time, the eNodeB 132 may store frequency information corresponding to each operator identification flag in advance.

In step 395, the eNodeB 132 transmits the UE Context release Complete to the MME 134.

Thereafter, the terminal 100 may be handed over to the NodeB 112 of the first operator network 110 or the second operator network 120 according to a known standard with reference to frequency information included in the RRCConnection Release Message. After handover, the terminal 100 transmits a paging response signal to the MSC 116 of the calling terminal through the NodeB 112, and a call setup process between the calling terminal and the terminal 100 is performed.

Therefore, the terminal 100 may receive only the frequency information of a single operator through the RRCConnection Release Message, and may be connected to the NodeB 112 according to the frequency information. If the eNodeB 132 does not perform the process of storing the SPID, the eNodeB 132 cannot identify the CS domain operator of the terminal 100. Accordingly, the eNodeB 132 transmits the RRCConnection Release Message to the terminal 100 by including frequency information for all operators, and the terminal 100 attempts to sequentially connect to the NodeB 112 according to each frequency information. You have to, and there is a delay. Therefore, in the mobile communication system according to an embodiment of the present invention, when a plurality of carrier networks and a single LTE network are interlocked, a delay occurring in the process of connecting to the NodeB 112 of the terminal 100 in the CSFB process can be reduced. have.

So far, the present invention has been focused on the embodiments. Many embodiments other than the above-described embodiments exist within the claims of the present invention. Those skilled in the art to which the present invention pertains will understand that the present invention may be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments should be considered in terms of explanation, not limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the equivalent range should be interpreted as being included in the present invention.

Claims (8)

In the mobile communication system including a Long Term Evolution (LTE) network connected to a plurality of CS (Circuit Switched) domain operator network to provide a CSFB (Circuit Switched FallBack) network,
An eNodeB receiving a connection request from the terminal; And
When a table mapping a location area (LA) in charge of a mobile switching center (MSC) related to each operator identification flag for each tracking area (TA) is stored, and receiving the connection request from the eNodeB, the terminal is a subscribed operator Check the operator identification flag of the carrier and the current TA where the terminal is located, and refer to the table to find the operator identification flag identified from the connection request and the LA mapped to the current TA, and the MSC in charge of the LA to the MS A Mobility Management Entity (MME) that requests a location update;
Mobile communication system comprising a.
According to claim 1,
When the MME receives a paging request according to an outgoing call request from another terminal from the MSC, the MME transmits a paging request to the eNodeB,
The eNodeB transmits an access message including frequency information of a NodeB controlled by the MSC to the terminal according to the paging request, so that the terminal is handed over from the eNodeB to the NodeB.
According to claim 2,
When the MME transmits the paging request to the eNodeB and receives a message requesting the CSFB from the terminal, the MME transmits the SPID in which the operator identification flag is inserted into a predetermined unused bit to the eNodeB,
The eNodeB transmits an access message including frequency information of a NodeB corresponding to the operator identification flag included in the SPID to the terminal.
According to claim 3,
The MME performs an authentication process according to the connection request, and extracts the SPID from a message received from a HSS (HOME SUBSCRIBER SERVER) during the authentication process.
A method for supporting a CSFB in a mobile communication system including a Long Term Evolution (LTE) network that is connected to a plurality of Circuit Switched (CS) domain operator networks and provides a Circuit Switched FallBack (CSFB) network,
Mobility Management Entity (MME) stores a table mapping a location area (LA) of a mobile switching center (MSC) related to each operator identification flag for each tracking area (TA),
The MME receiving a connection request of the terminal from the eNodeB;
Checking, by the MME, a carrier identification flag for the terminal and a current TA in which the terminal is located;
The MME referring to the table to find the operator identification flag identified from the connection request and the LA mapped to the current TA, and requesting a location update for the terminal with the MSC responsible for the LA;
CSFB support method comprising a.
The method of claim 5,
The MME receiving a paging request according to an outgoing call request from another terminal from the MSC;
Transmitting, by the MME, a paging request to the eNodeB; And
Transmitting, by the eNodeB to the terminal, an access message including frequency information of the NodeB controlled by the MSC according to the paging request, so that the terminal is handed over from the eNodeB to the NodeB.
CSFB support method further comprising.
The method of claim 6,
After the MME transmits a paging request to the eNodeB, when the MME receives a message requesting a CSFB from the UE, transmitting the SPID in which the operator identification flag is inserted into a predetermined unused bit to the eNodeB.
Including more,
The eNodeB transmits an access message including the frequency information of the NodeB controlled by the MSC to the terminal according to the paging request so that the terminal is handed over from the eNodeB to the NodeB, the eNodeB is assigned to the SPID. CSFB support method, characterized in that the step of transmitting the access message containing the frequency information of the NodeB corresponding to the included operator identification flag to the terminal.
The method of claim 7,
After the eNodeB receives the connection request from the terminal and transmits it to the MME,
And the MME performing an authentication process according to the connection request, and extracting the SPID from a message received from a HSS (HOME SUBSCRIBER SERVER) during the authentication process.

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