KR20130067143A - Methdo for providing cs fallback service and base station for perform the same - Google Patents

Abstract

PURPOSE: A method for providing a CS(Circuit Switch) fallback service and a base station device thereof are provided to prevent position registration delays caused by inconsistency between a TA(Tracking Area) and an LA(Location Area). CONSTITUTION: When a CS fallback processing unit receives a CS fallback object call, a receiving unit receives UTRAN(UMTS Terrestrial Radio Access Network) cell measurement information measured by a mobile terminal(S100,S110). An area determination unit determines whether or not a position of the mobile terminal is located in a boundary area of an MSC(Mobile Switching Center) and a boundary area of an LA based on the UTRAN cell measurement information(S120). A frequency selection unit determines whether or not the mobile terminal is located in the boundary area of the LA(S130). When the mobile terminal is located in the boundary area of the LA, frequency information of a target cell is selected in order that the LA, which is mapped to a TA in an LTE(Long Term Evolution) cell, is set as a WCDMA(Wideband Code Division Multiple Access) frequency 2 is set(S140). When the mobile terminal is not located in the boundary area of the LA, frequency information of a target cell is selected in order that the LA, which is mapped to the TA in the LTE cell, is set as the WCDMA frequency 1(S150). A transmission unit provides information of the target cell, which corresponds to a frequency selected by the frequency selection unit, to the mobile terminal(S160). [Reference numerals] (AA) Start; (BB) No; (CC) Yes; (DD) End; (S100,S160) Receive a CS fallback object call; (S110) Receive UTRAN cell measurement information; (S120) Determine whether or not a position of a mobile terminal is located; (S130) Boundary area?; (S140) Select a WCDMA frequency 2; (S150) Select a WCDMA frequency 1

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of providing a CS fallback service,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of providing a CS Fallback service and a base station apparatus performing the same.

Currently, UTRAN (UMTS Radio Access Network) supports both circuit switched (CS) and packet switched (PS) methods. However, although LTE (Long Term Evolution) supports voice calls based on IP Multimedia Subsystem (IMS), most operators do not adopt IMS.

Accordingly, in order to support voice calls, the LTE standard proposes a CS fallback (Circuit Switched Fallback) service.

CS fallback service is a mobile terminal when a mobile originate (MO) call (MO) call (MT) or Mobile Terminate (MT) call is generated when the camping (Camping) to the LTE network, the mobile terminal is a non-LTE Handover to UTRAN to handle voice calls. In other words, LTE is a temporary method of providing voice service through UTRAN before mVoIP becomes full-scale.

At this time, the LTE cell and the UTRAN cell have a 1: 1 mapping between the TA (Tracking Area) and the UTRAN cell area (Location Area) in the LTE cell region, CS fallback call is transmitted to LA of the cell.

However, due to the uncertainty of the cell size and the mobility of the mobile terminal due to the characteristics of the radio signal in the boundary region of the LTE cell, inconsistency may occur between the TA and the LA, so that the call is raised in another cell not corresponding to the TA / LA mapping Mobile Origination) or a paging response (Mobile Termination). This causes a delay in call setup because a new location registration must be performed in the border area.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a method of providing a CS fallback service in which location registration delay is prevented due to mismatch between TA / LA during CS fallback.

A method of providing a CS fallback service according to one aspect of the present invention includes:

A method for providing a circuit switch (CS) fallback service to a mobile terminal, wherein a base station apparatus of a first network capable of providing only packet service receives a CS fallback target call from the mobile terminal connected to the first network Determining, by the mobile terminal, whether the mobile station is located in a cell boundary region in a second network to provide a CS service according to the CS fallback target call to the mobile terminal; Selecting a different frequency from among a plurality of frequencies of a cell area of the second network that matches a cell area of the first network, depending on whether the mobile terminal is located in a cell boundary area of the second network; And providing cell information supporting the selected frequency to the mobile terminal.

Here, the plurality of frequencies of the cell region of the second network are bounded by the first frequency of the cell region of the second network matched to the cell region of the first network and the cell regions formed by the first frequency. It is characterized by including the 2nd frequency which forms the area | region containing as a cell area | region.

The selecting of the different frequencies may include: selecting the first frequency when the mobile terminal is not located in a cell boundary region in the second network; Selecting the second frequency when the mobile terminal is located in a cell boundary region in the second network.

In addition, in the step of determining whether the mobile terminal is located in the cell boundary area, the mobile terminal receives the cell measurement information of the second network measured by the mobile terminal and determines whether or not the cell boundary region of the mobile terminal is located. do.

Also, the first network is an LTE (Long Term Evolution) network, the second network is a UTRAN (UMTS Radio Access Network), and the cell boundary region is a boundary region of an LA (Location Area) of the second network .

A base station apparatus according to another aspect of the present invention,

A base station apparatus of a first network capable of providing only a packet service, the base station apparatus comprising: a CS fallback processing unit providing a circuit switch (CS) fallback service to a mobile terminal connected to the first network; And an area determining unit determining whether the mobile terminal is located in a cell boundary area in a second network to provide a CS service to the mobile terminal. And a frequency selector configured to select different frequencies from among a plurality of frequencies of the cell region of the second network that matches the cell region of the first network, according to a determination result of the region determiner.

Here, the base station device may include: a receiving unit for receiving measurement information of a cell of the second network measured by the mobile terminal from the mobile terminal and providing the measurement information to the area determination unit; And a transmitting unit for providing the mobile station with cell information of the second network corresponding to the frequency selected by the frequency selecting unit, wherein the area determining unit is configured to determine, based on the measurement information of the cell of the second network, And determining whether or not the cell boundary region is located in the second network of the mobile terminal.

In addition, the plurality of frequencies of the cell region of the second network correspond to boundaries of cell regions formed by the first frequency and the first frequency of the cell region of the second network matched to the cell region of the first network. It is characterized by including the 2nd frequency which forms the area | region containing as a cell area | region.

The frequency selector may be configured to select the first frequency when the mobile terminal is not located in a cell boundary region in the second network, and to select the first frequency when the mobile terminal is located in a cell boundary region in the second network. It is characterized by selecting 2 frequencies.

According to the embodiment of the present invention, since the configuration of the inter-carrier LA is changed in the UTRAN, the location registration procedure is omitted in the CS fallback by shifting to the WCDMA frequency instead of the TA / LA boundary region, so that call setup delay is not generated.

1 is a diagram schematically illustrating a mobile communication system to which a method for providing a CS fallback service according to an exemplary embodiment of the present invention is applied.
2 shows a general CS fallback procedure.
3 shows an example of mapping between a general LTE cell and a UTRAN cell.
4 is a diagram for explaining a frequency shift from a general LTE cell to a UTRAN cell.
5 is a diagram for explaining fallback in a general LA boundary region.
6 is a diagram for explaining frequency shift from an LTE cell to a WCDMA cell according to an embodiment of the present invention.
7 is a block diagram illustrating an internal configuration of an eNodeB according to an embodiment of the present invention.
8 is a flowchart of a CS fallback service method according to an embodiment of the present invention.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when an element is referred to as "comprising ", it means that it can include other elements as well, without excluding other elements unless specifically stated otherwise.

Hereinafter, a method of providing a CS fallback service according to an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram schematically illustrating a mobile communication system to which a CS fallback service providing method according to an embodiment of the present invention is applied.

Referring to FIG. 1, a user equipment (UE) 100 accesses a Long Term Evolution (LTE) network 200 when using a data service, and receives a CS service (eg, a voice service as well as an image). When using a service, a Short Message Service (SMS), LoCation Services (LCS), and Unstructured Supplementary Service Data (USSD), the UTS Terrestrial Radio Access Network (UTRAN) is connected to a CS (Circuit Switched) CS network.

As described above, in the mobile communication system, the LTE network 200 which cannot cope with circuit switched communication and the UTRAN network 300 such as WCDMA / GSM which can cope with circuit switched communication are mixed.

Here, the mobile terminal (UE) 100 is a terminal that supports a CS Fallback (Circuit Switched Fallback) service.

The CS fallback service is when a mobile originate (MO) call is generated or a mobile terminate (MT) call is generated while the mobile terminal 100 serving in the LTE cell area is camping in the LTE cell. The mobile terminal 100 is handed over to the UTRAN network 300 to process the CS service call.

The LTE network 200 is a network supporting only a packet switch (PS) scheme, and includes an eNodeB 210, a mobility management entity (MME) 230, and a serving gateway (S-GW). 250, a packet data network gateway (P-GW) 270, and an internet network 290.

Here, the eNodeB 210 is a base station apparatus of a wireless access network of LTE, and provides a paging request for CS fallback, a function of delivering an SMS message to the mobile terminal 100, and a target cell capable of CS service. It supports direct connection.

The MME 230 supports CS fallback as well as Combined EPS / IMSI Attach, Combined TA / LA Update, Detach, SMS message processing from the mobile terminal 100, and SGs interface connection management to the MSC 350.

The S-GW 250 serves as a mobility anchor when the mobile terminal 100 moves between handovers between the eNodeBs 210 or between 3GPP wireless networks.

The P-GW 270 assigns an IP (Internet Protocol) address of the mobile terminal 100, performs packet data related functions of the core network, and performs a mobility anchor role when moving between the 3GPP wireless network and the non-3GPP wireless network. do.

In addition, the UTRAN CS network 300 is a network supporting both a circuit switch (CS) scheme and a packet switched scheme, and includes a NodeB 310, a Radio Network Controller (RNC) 330, and an MSC ( A Mobile Switching Center (350), a Short Message Service Center (SMS) 370, and a Public Switched Telephone Network (PSTN) 390.

Here, the NodeB 310 and the RNC 330 are wireless access networks in the UTRAN CS network 300 and are based on Asynchronous Transfer Mode (ATM), and are located between the mobile terminal 100 and a wireless communication core network. Pass data and control information.

The MSC 350 supports the CS fallback service, as well as the Combined EPS / IMSI Attach, Combined TA / LA Update, Detach, SMS message processing from the MME 230 and SGs interface connection management to the MME.

In this case, for the CS fallback service, a mobility management process such as a combined EPS / IMSI Attach process, a Combined TA / LA Update process, and a Detach process is performed first. Hereinafter, the process is referred to as a location registration process.

On the other hand, the CS fallback procedure according to the incoming call is shown in FIG.

2 shows a general CS fallback procedure.

Referring to FIG. 2, when an outgoing call 1 is received from an O-MSC, the MSC (350 of FIG. 1) transmits a paging request 2 to the MME (230 of FIG. 1) using the SGsAP protocol.

Then, the MME (230 of FIG. 1) transmits a paging request (3) to the mobile terminal (100 of FIG. 1) connected to the LTE cell to receive a paging response (4) from the mobile terminal (100 of FIG. 1), Send a handover command 5 to the LTE cell.

Although not shown in FIG. 2, the process of providing information (SIB) of the UTRAN target cell to the mobile terminal 100 connected to the LTE cell is preceded by the paging request 2.

The LTE cell performs a handover and switch 6 process with the UTRAN cell, and upon completion, the MSC (350 of FIG. 1) receives a paging response through the UTRAN cell and performs a call setup 7 process. Since then, the mobile terminal 100 uses a voice call service through the UTRAN cell.

At this time, the location is managed through a 1: 1 mapping relationship between the MME (230 in FIG. 1) of the LTE cell and the MSC (350 in FIG. 1) of the UTRAN cell.

3 shows an example of mapping between a general LTE cell and a UTRAN cell.

Here, the area of the LTE cell is referred to as a TA (Tracking Area), and the area of the UTRAN cell is referred to as a LA (Location Area).

Referring to FIG. 3, the MME (230 in FIG. 1) manages each cell of TA1, TA2, and TA3, the MSC1 351 manages LA1, and the MSC2 353 manages LA2.

The MME 230 manages the mapping table. According to this mapping table, TA1 and TA2 are mapped to LA1 managed by the MSC1 351, and TA3 is mapped to LA2 managed by the MSC2 353.

Therefore, the MME (230 in FIG. 1) allows the CS fallback call of the mobile terminal 100 located in TA1 or TA2 to be processed through the MSC1 351, and the CS fallback call of the mobile terminal 100 located in TA3 MSC2 353, respectively.

Accordingly, the MME 230 provides the information of the LA1 to the mobile terminal 100 located in TA1 or TA2 before the CS fallback, and the information of the LA2 to the mobile terminal 100 located in the TA3.

Here, LA1 and LA2 include a plurality of UTRAN cells, and the transition from the LTE cell to the UTRAN cell will be described in detail with reference to FIG.

4 is a diagram for explaining a frequency shift from a general LTE cell to a UTRAN cell.

Referring to FIG. 4, the UTRAN or the WCDMA network uses a plurality of different FA (Frequency Assignment), for example, four different FAs.

That is, in FIG. 3, each cell using a plurality of different FAs exists in each of LA1 and LA2. The number of cells that vertically overlay the LTE network at the same frequency is plural. Generally, a WCDMA network uses a plurality of carriers overlaid.

Therefore, the base station 210 has to perform cell transition appropriately according to each FA. However, since it is difficult to provide the SIB information of the target cell to be transited for all the cells of all frequencies, it provides the SIB of the target cell for any one frequency. That is, when providing the information of LA1 to the mobile terminal 100 located in TA1 or TA2 of FIG. 3, cell information using a plurality of different FAs used in LA1 is provided. However, since it is not easy to provide cell information for all FAs, it is possible to provide SIBs of three cells (WCDMA cell 1, WCDMA cell 2, and WCDMA cell 3) for a specific FA, for example, FA1, to the mobile terminal 100 .

5 is a diagram for explaining fallback in the LA boundary region.

Referring to FIG. 5, the service area is mainly composed of an MSC area 1 managed by the MSC 1 351 and an MSC area 2 managed by the MSC2 353. In the MSC area 1, LA1 and LA2 are included, TA1 and TA2 are included, and MSC area 2 includes LA3 and TA3.

At this time, since LA2 is set in the MSC boundary zone, that is, the zone where the MSC zone 1 and the MSC zone 2 are overlapped, LA2 is set. When CS fallback is performed and the paging request is received from the MSC1 351 via the MME 230, But the mobile terminal 100 is located in the LA3 area and is therefore transmitted to the MSC2 353 via the LA3 instead of the LA2. Accordingly, the mobile terminal 100 has to perform a new location registration with respect to the LA3, and a call setup delay occurs due to the location registration.

Therefore, in order to solve such a problem, in an embodiment of the present invention, as shown in FIG. 6, frequency mapping is performed so that a transition from an LTE cell to a WCDMA cell is performed.

6 is a diagram for explaining frequency shift from an LTE cell to a WCDMA cell according to an embodiment of the present invention.

Referring to FIG. 6, a WCDMA network uses a plurality of different FAs, and at least one FA among a plurality of FAs is set to include an LA boundary region of a WCDMA frequency of an FA having a different WCDMA frequency.

That is, in FIG. 6, the WCDMA frequency 1 is set such that LA A is matched to TA α and β of the LTE cell, LA B is matched to TA γ and δ, and LA C is matched to TA ε and φ , LA D is set so that the WCDMA frequency 2 includes the boundary area between LA A and LA B of WCDMA frequency 1, and LA E is set so that the boundary area between LA B and LA C of WCDMA frequency 1 is included. That is, in LA A of WCDMA frequency 2, β and γ of LTE cell are matched with LA A of WCDMA frequency 1, and in LA B of WCDMA frequency 2, δ and ε of LTE cell are matched unlike LA B of WCDMA frequency 1 do.

As described above, in the conventional WCDMA frequency domain in which the FAs of the WCDMA cells matched to the LET cells are vertically overlapped and overlaid, the frequency of the FAs of the WCDMA cells matched to the LTE cells are all vertically And the frequency of at least one of the FAs is set so as to include the boundary region of the frequencies of the other FAs.

In this case, location registration may be omitted in case of CS fallback because there is no inconsistency between TA and LA as in the conventional case in Case 1. In Case 2 and Case 3, By mapping LA of WCDMA frequency 2 to LA that is mapped to TA, transition is made to the corresponding frequency in CS fallback, so that there is no discrepancy between TA and LA, and voice call can be performed without registering the location.

In the case where the WCDMA frequency region is set for the LTE cell, the base station apparatus of the LTE network, that is, the eNodeB 210, when the CS is dropped, Will be described.

FIG. 7 is a block diagram showing an internal configuration of an eNodeB 210 according to an embodiment of the present invention, and FIG. 7 schematically shows only a configuration related to an embodiment of the present invention.

7, the eNodeB 210 includes a CS fallback processing unit 211, a reception unit 213, an area determination unit 215, a frequency selection unit 217, and a transmission unit 219.

The CS fallback processing unit 211 performs a series of processes for the CS fallback service as described above with reference to FIG. At this time, the CS fallback processing unit 211 receives the CS fallback target call from the mobile terminal 100 camped on the LTE cell.

The receiving unit 213 receives the measurement information of the UTRAN cell LA measured by the mobile terminal 100 from the mobile terminal 100. At this time, the mobile terminal 100 may measure the quality of the UTRAN cell and transmit it to the eNodeB 210 periodically or at a specific point in time. Also, the measurement information of the cell may include the received signal strength of the cell.

The area determining unit 215 determines whether or not the position of the mobile terminal 100 is located in the boundary area of the MSC, particularly in the boundary area of the LA, based on the measurement information of the UTRAN cell LA received from the receiving unit 213 do. 6, it is determined whether the mobile terminal 100 is located in the boundary area between LA A and B of WCDMA frequency 1 or in the boundary area between LA B and C of WCDMA frequency 1. Here, the criterion of the boundary region of the LA is a region where mappings between the TA and the LA are likely to occur, and can be individually set through statistical or experimental values for each mobile communication system. For the criteria of such a region, It is obvious to those skilled in the art that a detailed description thereof will be omitted.

The frequency selection unit 217 selects the frequency of the target cell LA to which the CS dropback service is to be provided, that is, the frequency allocation (FA), to the mobile terminal 100. At this time, when the CS fallback target call is received through the CS fallback processing unit 211, the frequency selection unit 217 determines that the mobile terminal 100 is located in the boundary area of the LA according to the determination result of the area determination unit 215 The mobile station 100 selects the frequency information of the target cell LA to which the CS is to be dropped back so that the WCDMA frequency 2 as shown in FIG. 6 is set to the LA mapped to the TA of the LTE cell. Here, it is a matter of course that the WCDMA frequency 2 is set to LA so that the WCDMA frequency 2 includes the boundary line of the LAs of the WCDMA frequency 1 as described in FIG.

When it is determined in the area determination unit 215 that the mobile terminal 100 is not located in the boundary area of the LA, the LA mapped to the TA of the LTE cell is set to the WCDMA frequency 1 as shown in FIG. 6 And selects the frequency information of the target cell (LA) to which the CS will fall back to the mobile terminal (100).

The transmission unit 219 provides the mobile terminal 100 with information on the target cell LA corresponding to the frequency selected by the frequency selection unit 217, that is, the SIB.

FIG. 8 is a flowchart of a CS fallback service method according to an embodiment of the present invention, and is described in connection with the configuration of FIG.

Prior to the description, it is assumed that the mobile communication system has set the LA area of the WCDMA frequency 2 to include the boundary of the LA areas set at the WCDMA frequency 1, as shown in Fig. 6 for the frequency 1 and the frequency 2 of the WCDMA cell do.

Referring to FIG. 8, when the CS fallback processing unit 211 receives the CS fallback target call (S100), the receiving unit 213 receives the UTRAN cell measurement information measured by the mobile terminal 100 (S110).

The area determining unit 215 then determines whether the position of the mobile terminal 100 is located in the boundary area of the MSC, particularly in the boundary area of the LA, based on the measurement information of the UTRAN cell LA received from the receiving unit 213 (S120).

Next, the frequency selection unit 217 determines whether the mobile terminal 100 is located in the boundary area of the LA according to the determination result of the area determination unit 215 (S130) When it is determined to be located in the boundary area of the LA, the LA mapped to the TA of the LTE cell is set to the frequency of the target cell (LA) to which the mobile terminal (100) Information is selected (S140).

However, when it is determined that the mobile terminal 100 is located in a boundary area of the LA, the LA mapped to the TA of the LTE cell is set to the WCDMA frequency 1 as shown in FIG. 6 to the mobile terminal 100 The frequency information of the target cell LA to which the CS is to be dropped is selected (S150).

Thereafter, the transmitter 219 provides information of the target cell LA corresponding to the frequency selected by the frequency selector 217 to the mobile terminal 100 (S160).

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

Claims (9)

A method of providing a circuit switch (CS) fallback service to a mobile terminal,
When the base station apparatus of the first network capable of providing only packet service receives a CS fallback target call from the mobile terminal connected to the first network, the mobile terminal moves the CS service according to the CS fallback target call. Determining whether a cell is located in a cell boundary region in a second network to be provided to a terminal;
Selecting a different frequency from among a plurality of frequencies of a cell area of the second network that matches a cell area of the first network, depending on whether the mobile terminal is located in a cell boundary area of the second network; And
Providing cell information supporting the selected frequency to the mobile terminal
/ RTI > The method of claim 1,
The plurality of frequencies of the cell region of the second network includes a boundary of cell regions formed by the first frequency and the first frequency of the cell region of the second network matched to the cell region of the first network. And a second frequency forming the region as the cell region. The method of claim 2,
The step of selecting different frequencies,
Selecting the first frequency when the mobile terminal is not located in a cell boundary region in the second network;
Selecting the second frequency when the mobile terminal is located in a cell boundary region in the second network
/ RTI > The method of claim 3,
Determining whether the cell boundary region of the mobile terminal is located by receiving cell measurement information of the second network measured by the mobile terminal from the mobile terminal in determining whether the cell boundary region is located in the cell boundary region; How to Provide Fallback Services. 5. The method of claim 4,
Wherein the first network is an LTE (Long Term Evolution) network, the second network is a UMTS Radio Access Network (UTRAN), and the cell boundary region is a boundary region of a Location Area (LA) of the second network To provide a CS fallback service. A base station apparatus of a first network capable of providing only packet service,
A CS fallback processing unit for providing a CS (Circuit Switch) Fallback service to a mobile terminal connected to the first network; And
An area determining unit determining whether the mobile terminal is located in a cell boundary area in a second network to provide a CS service to the mobile terminal;
A frequency selector for selecting different frequencies from among a plurality of frequencies of the cell region of the second network matching the cell region of the first network according to a determination result of the region determiner
Base station device comprising a. The method according to claim 6,
A reception unit for receiving measurement information of a cell of the second network measured by the mobile terminal from the mobile terminal and providing the measurement information to the area determination unit; And
And a frequency selection unit for selecting a frequency of the second network,
More,
Wherein the area determining unit determines whether a cell boundary region is located in the second network of the mobile station based on measurement information of a cell of the second network received through the receiver. The method of claim 7, wherein
The plurality of frequencies of the cell region of the second network includes a boundary of cell regions formed by the first frequency and the first frequency of the cell region of the second network matched to the cell region of the first network. A base station apparatus comprising a second frequency forming an area as a cell area. 9. The method of claim 8,
The frequency selector selects the first frequency when the mobile terminal is not located in a cell boundary region in the second network and the second frequency when the mobile terminal is located in a cell boundary region in the second network. Base station apparatus, characterized in that for selecting.

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