KR101234190B1 - Redirection Method Using Handover and Mobile Communication System therefor - Google Patents

Abstract

A call resetting method by handover and a mobile communication system thereof are disclosed. Even if the RRC connection request service is a redirection target, the mobile communication system of the present invention finishes the call setup without immediately proceeding with the redirection procedure and then handles the redirection according to the handover method. Accordingly, the mobile communication system of the present invention eliminates the inevitable delay of the service incurred during the redirection operation by the conventional RRC Connection Reject method, and can also handle the redirection generated by the simultaneous call connection request.

Description

Redirection Method Using Handover and Mobile Communication System therefor}

According to the present invention, even if a call requested to be set up in a WCDMA mobile communication system is a redirection target, a handover is performed to finish call setup and then to reset a call in another system or frequency using a handover procedure. Call resetting method and a mobile communication system.

In the WCDMA specification, redirection refers to redirection to a different frequency (or system) for a call to be established. Redirection events that occur during a particular call setup process are an essential feature that enables a dedicated system to provide only specific services.

For example, the applicant of the present invention has applied for a 'mobile communication system having a femtocell for packet data service and its service method (Korean Patent Application No. 10-2010-0067241) using the function. According to this method, apart from processing a high speed data service for a wireless terminal existing in a femtocell in a femtocell, other services can be processed through a macro cell using a redirection method to reduce the paging load of the femtocell. High-speed packet data service can be provided without increasing the registration load in the core network.

The conventional call redirection scheme begins with the terminal transmitting a Radio Resource Control (RRC) Connection Request message (RRC Connection Request) to the system to initiate a service. If the system does not have enough resources available or does not accept a particular service, the system includes the redirect Info information in the RRC Connection Reject message to the terminal, thereby allowing the terminal to redirect from the idle mode to another system or frequency. Can be instructed. This approach is described in RRC Connection Reject (10.2.35) and RRC Connection Release (10.2.36) as Redirect Info (10.3.3.29) specified in 3GPP TS 25.331.

1 illustrates a configuration environment between a femtocell and a macro cell. The macro cell 50 is assigned a primary scrambling code (PSC) A and operates four frequency assignments (FAs), and the femtocell 30 is a PSC. It shows that N is assigned and using only one 4FA frequency. The terminal 11 requests the call setup to the femtocell 30, but the call setup is not possible and thus the situation in which the user needs to redirect to another frequency of the macro cell 50 is illustrated.

2 is a diagram illustrating a conventional call setup process by redirection, and the femtocell does not respond to the call setup of the terminal and processes the terminal to redirect to the macro cell.

Referring to FIG. 2, when the terminal 11 receives a call connection request from a subscriber, the terminal 11 transmits an RRC connection request message to the femtocell 30 in order to establish a call through the femtocell 30 in the idle state. The RRC connection request message includes an initial UE identity of the terminal 11 and an RRC establishment cause. There are various reasons for the RRC connection, and includes a call attempt or paging response (S201).

When the femtocell 30 receives the RRC connection request message from the terminal 11, the femtocell 30 determines whether the corresponding service is possible or should be redirected based on the RRC connection reason included in the RRC connection request message (S203).

As a result of the determination in step S203, if the call is not redirected and available for service, the femtocell 30 performs a normal call setup process. In other words, the femtocell 30 responds by transmitting an RRC Connection Setup message to the terminal 11 and then performs a normal call setup procedure (S205).

As a result of the determination in step S203, when the originating call is a redirection target, the femtocell 30 releases the connection by transmitting an RRC connection reject message including the redirection information to the terminal 11. Redirection information includes information on the macro cell to provide the requested service (S207).

The terminal 11 receiving the RRC connection rejection message from the femtocell 30 releases the connection with the femtocell 30 and transitions to a frequency (FA) included in the redirection information (S209).

Thereafter, the terminal 11 transmits an RRC connection request message to the macro cell 50 through the transitioned frequency to request network access again, and the macro cell 50 corresponds to the RRC connection request message of the terminal 11. It responds by sending an RRC Connection Setup message to the terminal 11. When the RRC Connection Setup is completed, the macro cell 50 and the terminal 11 complete the call setup procedure by performing a procedure for setting (S211 to S217).

In the above manner, the conventional redirection procedure is performed.

However, in case of the redirection scheme by the RRC Connection Reject described above, the terminal needs to enter the idle mode, detect another frequency, and then connect to the target cell (Camp On) to request a service in order to perform step S207.

For this reason, a significant delay inevitably occurs from the time of sending the first RRC Connection Request to sending the RRC Connection Request back to the frequency included in the redirection information and receiving the service. This may make the user feel that the call connection or service does not start immediately when the call is set up, so it is not a good way in terms of quality of service.

Another problem of the conventional redirection method is that redirection control cannot be performed when a concurrent call service is requested in which a CS (Circuit Switched) domain and a PS (Packet Switched) domain are combined. In the case of the simultaneous call service, the service is started without an RRC connection procedure for a domain that is set later, because the conventional redirection can be performed only by the RRC connection procedure. Therefore, in case of simultaneous call setup, redirection processing by RRC Connection Reject message is impossible.

On the other hand, femtocell (Femto Cell) is a small base station that provides a mobile communication service to an area of about 10m radius. Hot spots are installed in areas where shadows of the macro cell are deteriorated, such as homes or buildings, and for the purpose of supplementing the quality of mobile communication services. ) To increase service capacity and quality. Since femtocells use a general-purpose Internet circuit for communication with a core network, which is a core control station of a mobile communication network, there is an advantage that the installation cost and maintenance cost are low and can be installed wherever an internet circuit is installed.

An object of the present invention is to complete the call setup and then to reset the call in another system or frequency by using a handover procedure even if the call requested for setup in the WCDMA mobile communication system is a redirection target. A call resetting method by handover and a mobile communication system thereof are provided.

According to an aspect of the present invention, there is provided a method for resetting a call by handover, the method comprising: receiving, by a radio network controller (RNC), a message for call establishment from a terminal; Even when the call setup requested service is a redirection target, starting the call service by finishing the call setup procedure without performing the redirection procedure; Determining, by the radio network controller, whether the call service is a redirection target; And when the call service is determined to be a redirection object, initiating a handover procedure by the radio network controller that initiated the call service to a cell capable of performing the call service to process the redirection.

The method of the present invention is initiated when a Radio Resource Control (RRC) connection request message for call setup is received from a terminal or an Initial Direct Transfer message is received for simultaneous call setup from a terminal that is already receiving a call service. .

According to an embodiment, the radio network controller is preferably a femtocell base station having a base station function.

According to another embodiment, the determining of the redirection target may be performed after receiving the RAB Assignment Request message from the core network during the step of initiating the call service and determining the call service history based on the RAB information. It is particularly desirable that the call service be performed immediately after initiation.

The method of the present invention may be determined based on the redirection target setting that is variously and finely divided by the operator, not based on the connection reason () included in the RRC connection request.

According to another embodiment of the present invention, the call resetting method as described above may be implemented in various types of mobile communication systems, and a wireless network controller or a femtocell base station is just one example.

In the mobile communication system of the present invention, even if a call for which call setup is requested is a redirection target, the call setup is completed and then immediately redirected to another frequency or system using a handover procedure. There is no delay in services that inevitably occur during operation.

In addition, even when the requested service cannot be supported by the Concurrent Call service, the redirect call can be handled by redirecting to another frequency or system through the handover procedure after completing the simultaneous call setup. Can be. This feature is particularly useful when the service requested cell is a femtocell with limited resources.

Furthermore, the method of the present invention can freely configure a dedicated system suitable for the purpose because the method can be redirected by more granular services than the redirection method determined only by the RRC establishment cause.

Accordingly, the user can be provided with the service without feeling the delay, and the operator can construct a system for a specific purpose more freely than the existing method from the operator's point of view.

1 is a diagram illustrating a configuration environment between a femtocell and a macro cell;
2 is a diagram illustrating a call setup process by a conventional redirection;
3 is a view provided to explain a redirection method according to an embodiment of the present invention;
4 is a diagram provided to explain a redirection method in simultaneous call setup; and
5 is a diagram illustrating a femtocell system of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to the drawings.

The Rdeirction method according to the present invention does not process immediately in a call setup process initiated by a radio resource control (RRC) connection request message (RRC Connection Request) or the like, and uses a handover procedure after the call setup. This allows a call to be reset, such as a redirect. Therefore, even if the terminal cannot accept the requested call setup request by providing an RRC connection request message, the call setup procedure is still performed. have.

The method of the present invention can perform a call setup procedure by an RRC connection request message according to a wideband code division multiple access (WCDMA) mobile communication protocol regardless of a macro cell or femtocell, or is already providing a call service. It may be performed by any mobile communication device / system that performs simultaneous call setup procedures that the terminal provides by requesting an Initial Direct Transfer message.

In the case of a femtocell, even if the femtocell does not provide the simultaneous call access service itself, any device capable of performing the simultaneous call access procedure shown in FIG. 4 below is possible. In the following description, a femtocell capable of performing a call setup procedure and a simultaneous call connection procedure will be described.

For reference, the femtocell system 300 of the present invention includes an access gateway (AGW) for connecting a femtocell base station 301 and a femtocell base station 301 to a core network (CN) 17 as shown in FIG. 5. 303). The entire coverage (or a portion thereof) of the femtocell system 300 is included in the macro cell 50 like the femtocell 30 of FIG. 1.

The femtocell base station 301 of the present invention basically has a radio network controller function to operate in the same manner as the femtocell 30 of FIG. In addition, it should include an algorithm or configuration relating to a 'call resetting method' specifically proposed in the present invention and described below. As described above, for example, even when the femtocell base station 301 ultimately serves only a data call, it should be able to perform a call connection procedure or a simultaneous call connection procedure for voice call service. In the following description, when the 'femtocell 300' is used interchangeably in an apparatus sense, it may be understood to mean the 'femtocell system 300 or the femtocell base station 301'.

The access gateway 303 connects at least one femtocell base station (or its femtocell) including the femtocell base station 301 to the core network 70. Therefore, in the following description, when the femtocell 300 or the femtocell base station 301 transmits a message to the core network 70, it should be understood that the transmission is via the gateway 303 even if not mentioned otherwise.

Hereinafter, a redirection method according to an embodiment of the present invention will be described with reference to FIG. 3. For convenience of description, it is assumed that the femtocell 300 of the present invention is assigned the same radio configuration as that of FIG. 1, that is, PSC N and uses only one 4 FA frequency. Furthermore, it is assumed that the femtocell 300 should also perform redirection to another frequency of the macro cell 50 in response to a call establishment request of the terminal 11.

First, the terminal 11 operating the 4FA in the idle state transmits an RRC connection request message to the femtocell 300 and attempts to call setup. The RRC connection request message includes an initial UE identity of the terminal 150 and an RRC establishment cause (S301).

Even if the femtocell 300 receives the RRC connection request message, the femtocell 300 does not determine whether the corresponding call establishment request is a redirection target based on the RRC connection reason. Instead, the femtocell 300 performs an access procedure in response to the terminal 11 in an RRC Connection Setup message (S303).

After receiving the RRC Connection Setup message, the terminal 11 also responds with an RRC Connection Setup Complete message (S305), and then initial direct transmission to be sent to the Core Network (CN) 70 for voice call service (Initial Direct Transfer). ) Message to the femtocell 300 and the femtocell 300 transmits the message to the core network 70. The initial direct transfer message includes a connection management (CM) service request message (S307).

After that, the call setup procedure is completed and the call service is started (S309). Specifically, the security procedure is initiated and completed by the core network 70, and the terminal 11 transmits a setup message to the core network 70 by using direct transfer signaling. The core network 70 responds with a Call Proceeding message. Thereafter, a RAB (Radio Access Bearer) setting procedure is performed. The core network 70 provides the femtocell 300 a RAB Assignment Request message to be provided to the terminal 11, and the femtocell 300 transmits the response of the terminal 11 to the core network 70 as a RAB Assignment Response message. do. After that, an alerting message, a Connect message, and a Connect Ack message are transmitted to complete the call setup and start the call service.

As soon as the call service is started, the femtocell 300 determines whether the set service is a redirection target. The femtocell 300 may be performed by determining whether a specific service is set by the operator as a redirection target or by determining whether the service is unavailable due to an overload condition. In this determination, the service details to be provided to the terminal 11 are required, and these service details use the RAB Type information included in the RAB Assignment Request message received by the femtocell 300 from the core network 70 (S311).

As a result of the determination in step S311, if it is not the target of redirection, the service is maintained in the femtocell 300 (S313).

If, as a result of the determination in step S311, if the corresponding call service is a redirection target, the femtocell 300 determines a target cell to be redirected, and sends a Relocation Required message to the core network 70 to serve a radio radio (SRNS) Network Subsystem) A handover procedure is initiated by a relocation procedure (S315).

The following procedure is the same as the handover procedure by the normal SRNS relocation procedure. Referring to the example of FIG. 3, the core network 70 transmits a relocation request message to the target system 50 (S317), and the macro cell 50 serving as the target system allocates resources according to the contents of the relocation request message. After the allocation, the core network 70 transmits a Relocation Request Ack message to inform that the bearer setup is completed. At this time, the target system 50 ensures the consistency of the service to the terminal by allocating resources by reflecting the details of the service being serviced in the femtocell 300 as possible (S319 and S321).

When the relocation command message is transmitted from the core network 70 to the femtocell 300, the femtocell 300 transmits a radio bearer reconfiguration message to the terminal 11 according to the contents of the relocation command. This RRC message includes resource allocation information of the target side (S323, S325).

The terminal 11 completes Radio Bearer Reconfiguration and transmits Complete to the target. At this time, the connection between the terminal 11 and the femtocell 300 is cut off (S327).

When the target system 50 transmits a Relocation Complete message to the core network 70 to notify the Acquisition of the terminal 11 (S329), the core network 70 transmits an IU Release Command message to the femtocell 300 to femtocell ( A resource release of 300 is requested (S331).

The femtocell 300 sends an IU Release Complete message to notify the release of resources to complete the redirection procedure (S333). Through the above process, the call resetting procedure of the femtocell is performed, and the terminal 11 receives the service from the target system 50.

In FIG. 3, the determination of whether the service requested from the terminal 11 is a redirection target is made in step S311 in which call setup is completed. However, as described above, when the femtocell 300 receives the RAB Assignment Request message from the core network 70, the femtocell 300 acquires information necessary for determining whether to redirect, and according to another embodiment of the present invention, the RAB Assignment Request message At any point after receiving, it can be determined whether to redirect. However, even when it is determined that the call service should be redirected, the actual redirection is performed by handover procedure after call setup is completed.

Hereinafter, referring to FIG. 4, a redirection method in a simultaneous call will be described. It is assumed that the femtocell 300 of FIG. 4 is a femtocell dedicated to data communication. Therefore, when a voice call service request comes in the form of a simultaneous call from the terminal 11, it should be redirected.

The terminal 11, which is already connected to the PS (Packet Switched) domain and receives data service, transmits an Initial Direct Transfer message to the femtocell 300 to the core network 70 to initiate a voice call service, and the femtocell 300 The message is transmitted to the core network 70. The Initial Direct Transfer message includes a Connection Management (CM) Service Request message (S401, S403).

The following procedure is the same as the known simultaneous call setup method. Security procedures, setup, call proceedings, RAB setup procedures are performed, and ALerting messages, Connect messages, and Connect Ack messages are transmitted to each other to finish simultaneous call setup by the PS domain and the Circuit Switched (CS) domain. Is started (S405).

As soon as the simultaneous call service is started, the femtocell 300 determines whether the newly set service is a redirection target. The determination method here is the same as in step S311 (S407).

As a result of the determination in step S407, the service is maintained in the femtocell 300 if it is not the target of redirection (S431).

If, as a result of the determination in step S407, if the call service is the target of redirection, the femtocell 300 determines a destination cell to be redirected, and sends a Relocation Required message to the core network 70 to serve a radio radio (SRNS). Network Subsystem) Initiates a handover procedure for a simultaneous call by a relocation procedure. In order to simultaneously establish a call, a Relocation Required message should be transmitted to both the Mobile Switching Center (MSC) and the Serving GPRS Support Node (SGSN) of the core network 70 (S409).

The following procedure is the same as the handover procedure by the conventional SRNS relocation procedure, and is the same as the steps S315 to S333 of FIG. 3. Finally, the terminal 11 receives data and voice call service in the macro cell 50.

By the above method, the simultaneous call can be redirected to another cell without interruption of service. This is because the redirection is determined when the service is reconfigured regardless of the RRC connection procedure.

As described above, the redirection method of the present invention is not only determined by the establishment cause included in the RRC connection request message, but is further subdivided by the operator's setting, and various redirection target settings are possible. A dedicated system can be freely configured to meet the purpose.

3 and 4 illustrate the femtocell 300, that is, the operation of the femtocell base station 301, the present invention is not limited to the femtocell as described above. If the present invention is applied to the macro system instead of the femtocell system 300, the operation of the femtocell of FIGS. 3 and 4 will be performed by a radio network controller (RNC).

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limiting the scope of the invention as defined by the appended claims. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention.

Claims (9)

Receiving, by a radio network controller (RNC), a message for call establishment from a terminal;
Even when the call setup requested service is a redirection target, starting the call service by finishing the call setup procedure without performing the redirection procedure;
Determining, by the radio network controller, whether the call service is a redirection target;
If it is determined that the call service is to be redirected, the wireless network controller that initiates the call service initiates a handover procedure to a cell capable of the call service and processes the redirection. How to reset a call.
The method of claim 1,
In the step of receiving the message, the message received from the terminal by the radio network controller is a Radio Resource Control (RRC) connection request message for call setup, or Initial provided for simultaneous call setup from the terminal already receiving a call service. Call reset method by handover, characterized in that the Direct Transfer message.
The method according to claim 1 or 2,
The radio network controller is a femtocell base station having a base station function together, characterized in that the call reset by the handover.
The method of claim 1,
Determining whether the redirect target is,
And performing a call after receiving the RAB Assignment Request message from the core network during the step of initiating the call service and determining the call service details based on the RAB information.
5. The method of claim 4,
The method of claim 1, wherein the determining of whether the redirection is performed is performed immediately after the call service is started.
5. The method of claim 4,
Determining whether the redirect target is,
When the call service details received based on the RAB information by receiving the RAB Assignment Request message from the core network during the step of initiating the call service is determined to be a redirect target set by the handover characterized in that How to reset a call.
A system connected to a core network and receiving a message for call establishment from a terminal to provide a call service.
Even when the call setup requested service is a redirection target, after completing the call setup procedure without performing the redirection procedure, after the call service is started, a handover procedure is initiated to a cell capable of performing the call service to process the redirection. Mobile communication system.
The method of claim 7, wherein
The call setup message is a RRC (Radio Resource Control) connection request message for call setup, or a mobile communication system characterized in that an Initial Direct Transfer message provided for simultaneous call setup from the terminal receiving a call service.
The method of claim 7, wherein
And the system is a femtocell base station connected to the core network via an access gateway and having both a base station function and a radio network controller function.

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