KR101444433B1 - Methdo for providing cs fallback service and base station for perform the same - Google Patents

Abstract

A method of providing a CS switch fallback service and a base station apparatus performing the same.
In this method, a first network provides packet service, a second network provides a CS service using a plurality of FAs, and a plurality of FAs of the second network each match a cell area of the first network And a second FA assigned to cells having a first FA assigned to cells having a cell region of the second network and a cell region having a region including a boundary of cells using the first FA. When the base station apparatus of the first network receives a CS fallback target call from the mobile terminal connected to the first network, the mobile terminal transmits a CS service according to the CS fallback target call to a second Determining whether the mobile terminal is located in a border area of a cell using the first FA, determining whether the mobile terminal is located in a border area of a cell using the first FA in the second network, Or the second FA, and provides cell information using the selected FA to the mobile terminal.

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, the UTRAN (UMTS Radio Access Network) supports both Circuit Switch (CS) and Packet Switch (PS) methods. However, LTE (Long Term Evolution) supports voice calls based on IMS (IP Multimedia Subsystem), but most operators do not use IMS at present.

Accordingly, the LTE standard proposes a CS Switched Fallback service to support voice calls.

The CS fallback service is a method of providing a mobile terminal with a non-LTE (Mobile Terminals) call when a Mobile Originate (MO) call or MT (Mobile Terminate) call occurs while the mobile terminal is camping in the LTE network UTRAN and handles the voice call. 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:

CLAIMS 1. A method of providing a CS (Circuit Switch) fallback service to a mobile terminal, the method comprising: providing a packet service to a first network; providing a CS service using a plurality of FAs (Frequency Assignment) Wherein the plurality of FAs of the second network include a first FA assigned to cells having a cell region of the second network matching each cell region of the first network and a boundary of cells using the first FA And a second FA assigned to cells having an area as a cell area, and when the base station apparatus of the first network receives a CS fallback target call from the mobile terminal connected to the first network, Determining whether a CS service according to the CS fallback target call is located in a boundary area of a cell using the first FA in a second network to provide the CS service to the mobile terminal; Selecting the first FA or the second FA according to whether the mobile terminal is located in a boundary area of a cell using the first FA in the second network; And providing cell information using the selected FA to the mobile terminal.

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Here, the step of selecting the first FA or the second FA may include selecting the first FA when the mobile terminal is not located in a boundary area of a cell using the first FA in the second network ; And selecting the second FA when the mobile terminal is located in a boundary area of a cell using the first FA 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 .

According to another aspect of the present invention,

A base station apparatus of a first network capable of providing only a packet service, wherein a second network provides a CS service using a plurality of FAs, and a plurality of FAs of the second network are respectively matched to cell areas of the first network And a second FA allocated to cells having a cell area including a first FA allocated to cells having a cell region of the second network and a boundary between cells using the first FA, A CS fallback processing unit for providing a CS (Circuit Switch) Fallback service to a mobile terminal connected to the first network; An area determination unit for determining whether the mobile station is located in a boundary area of a cell using the first FA in a second network to provide a CS service to the mobile station; And a frequency selection unit for selecting the first FA or the second FA according to the determination result of the area determination unit and providing cell information using the selected FA to the mobile station.

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.

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The frequency selector may select the first FA when the mobile terminal is not located in the cell boundary region in the second network and may select the first FA when the mobile terminal is located in the cell boundary region in the second network. 2 FA is selected.

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.

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.
Figure 2 shows a generic 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.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out 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 order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters 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, when a user equipment (UE) 100 uses a data service, the user equipment 100 accesses an LTE (Long Term Evolution) network 200 and uses a CS service (for example, (UTRAN) Terrestrial Radio Access Network (CS) circuit switched network when using a Short Message Service (SMS), LoCation Services (LCS), and USSD (Unstructured Supplementary Service Data)

As described above, the mobile communication system is mixed with the LTE network 200 incapable of circuit-switched communication and the UTRAN network 300 such as WCDMA / GSM capable of coping with circuit-switched communication.

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

The CS fallback service is a service in which when an MO (Mobile Originate) call occurs or a MT (Mobile Terminate) call occurs while the mobile terminal 100 in service is camping in the LTE cell in the LTE cell area And hand over the mobile terminal 100 to the UTRAN network 300 to process the CS service call.

The LTE network 200 supports only the packet switching (PS) method and includes an eNodeB 210, an MME (Mobility Management Entity) 230, a Serving Gateway (S-GW) (PDSN) 250, a P-GW (Packet Data Network Gateway) 270, and an Internet network 290.

Here, the eNodeB 210 is a base station apparatus of the LTE radio access network. The eNodeB 210 includes a paging request for CS fallback, a function of delivering an SMS message to the mobile terminal 100, a target cell Direct connection is supported.

The MME 230 supports 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 as well as CS fallback.

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

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

The UTRAN CS network 300 supports both circuit switching (CS) and packet switching. The UTRAN CS network 300 includes a Node B 310, an RNC (Radio Network Controller) 330, an MSC A mobile switching center) 350, a Short Message Service Center (SMSC) 370, and a Public Switched Telephone Network (PSTN) 390.

The NodeB 310 and the RNC 330 are radio access networks in the UTRAN CS network 300 and are located in an asynchronous transfer mode (ATM), between the mobile terminal 100 and a wireless communication core network Data and control information.

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

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

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

Figure 2 shows a generic CS fallback procedure.

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

Then, the MME (230 in FIG. 1) receives the paging response 4 from the mobile terminal (100 in FIG. 1) by sending a paging request 3 to the mobile terminal (100 in FIG. 1) connected to the LTE cell, And transmits the handover command 5 to the LTE cell.

Here, although not shown in FIG. 2, a process of providing information (SIB) of the UTRAN target cell to the mobile terminal 100 connected to the LTE cell is performed prior to the paging request (2).

The LTE cell performs a handover and a switch 6 process with the UTRAN cell, and when completed, the MSC (350 in FIG. 1) receives the paging response through the UTRAN cell and performs a call setup process. After that, the mobile terminal 100 uses the 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,
The first network provides a packet service, the second network provides a CS service using a plurality of FAs (Frequency Assignment)
Wherein a plurality of FAs of the second network include a first FA assigned to cells having cell regions of the second network matching the cell regions of the first network and a boundary of cells using the first FA And a second FA assigned to cells having a cell region as an area to be processed,
When the base station apparatus of the first network receives a CS fallback target call from the mobile terminal connected to the first network, the mobile terminal transmits a CS service according to the CS fallback target call to a second Determining whether the first FA is located in a boundary area of a cell using the first FA;
Selecting the first FA or the second FA according to whether the mobile terminal is located in a boundary area of a cell using the first FA in the second network; And
Providing cell information using the selected FA to the mobile terminal
/ RTI > delete The method according to claim 1,
The step of selecting the first FA or the second FA includes:
Selecting the first FA when the mobile terminal is not located in a border area of a cell using the first FA in the second network; And
Selecting the second FA when the mobile terminal is located in a border area of a cell using the first FA in the second network
/ RTI > The method of claim 3,
The method comprising the steps of: determining whether a cell boundary region of the mobile station is located in the boundary region of the mobile station by receiving cell measurement information of the second network measured by the mobile station from the mobile terminal; A method for providing a CS fallback service. 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 a packet service,
The second network provides a CS service using a plurality of FA (Frequency Assignment)
Wherein a plurality of FAs of the second network include a first FA assigned to cells having a cell region of the second network matching each cell region of the first network and a boundary of cells using the first FA And a second FA allocated to cells having a cell region as a cell region,
A CS fallback processing unit for providing a CS (Circuit Switch) Fallback service to a mobile terminal connected to the first network;
An area determination unit for determining whether the mobile station is located in a boundary area of a cell using the first FA in a second network to provide a CS service to the mobile station; And
A frequency selection unit for selecting the first FA or the second FA according to the determination result of the area determination unit and providing cell information using the selected FA to the mobile terminal,
. 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,
Further comprising:
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. delete 8. The method of claim 7,
Wherein the frequency selecting unit selects the first FA when the mobile terminal is not located in a cell boundary region in the second network and if the mobile terminal is located in a cell boundary region in the second network, The base station apparatus comprising:

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