KR101269584B1 - FemtoCell Apparatus and Hard Handover Method thereof - Google Patents

Abstract

A femtocell base station and its hard handover method are disclosed. When the service femtocell presently providing the terminal is a service that cannot be provided by the target macro cell, the serving cell of the present invention provides the current terminal with a 'Relocation Required' message provided to the core network for hard handover. Instead of unilaterally including the service details provided by the service, the modified service details are changed to the service details that can be provided by the target macro cell, so that the resource allocation fails in the target cell and the handover is delayed or handed over. Make sure that you don't have a problem with the call breaking because of a problem.

Description

FemtoCell Apparatus and Hard Handover Method

The present invention is femtocell base station and the femtocell base station that does not occur when the handover from the femtoCell (FotoCell) to the macrocell (MacroCell), by handing out the service configuration not supported by the macro cell in advance to prevent the handover It relates to a hard handover method.

FemtoCell base station is a very small base station characterized by a very small service capacity (about 8ch ~ 32ch) and a narrow service area according to the output limitation. Due to the narrow service range, indoors may be installed alone and used for home use. However, femtozones may be formed by installing a large number of femtocells in open areas such as offices or public places.

A femtocell base station uses a hard handover method when performing a handover using a neighboring macro cell as a target cell. Hard handover refers to a method in which a terminal first cuts a serving cell resource and then acquires a target cell resource.

On the other hand, soft handover acquires the resources of the target cell while maintaining the connection of the serving cell, transmits and receives data using both paths, and releases the resources of the serving cell after completely entering the target cell area. That's the way it is. The soft handover method occupies both the resource of the serving cell and the target cell during handover, and thus is not suitable for femtocells in which handover occurs frequently due to small service capacity and small service area.

A method of performing a handover from a femtocell to a macro cell uses a 'UE Involved Serving Radio Network Subsystem (SRNS) Relocation' method, which will be described with reference to FIG. 1.

FIG. 1 is a flowchart provided to explain a handover procedure of a UE Involved SRNS Relocation 'method. For convenience of description, configurations such as a gateway included in a femtocell system are not essential to the description.

First, the serving femtocell 13 transmits a measurement control message to the terminal 11 in which call setup is completed, and instructs a neighbor list and a search method (S101), and the terminal 11. Monitors the base stations of the active set and the monitored set (or neighboring cell) according to the Measurement Control message and transmits a measurement report to the serving femtocell 13 when event conditions are met. (S103).

The serving femtocell 13 transmits a direct transfer message to the core network (CN) 17 when it is determined that handover by a specific event is necessary based on the measurement result. This message includes a 'Relocation Required' message, which is a RANAP (Radio Access Network Application Part) message, and the service femtocell 13 currently provides the terminal 11 to be handed over (hereinafter, simply 'current service'). Information, which is referred to as "the details", is included for resource setting in the target system 15 (S105).

The core network 17 transmits a Relocation Request message to the target system 15 (S107), and the target system 15 allocates resources according to the contents of the Relocation Request message, and then sends the Relocation Request Ack to the core network 17. Send a message to inform you that the bearer setup is complete. At this time, the target system 15 ensures the consistency of the service to the terminal by allocating resources by reflecting the details of the service being served by the serving femtocell 13 as much as possible (S109 and S111).

When the relocation command message is transmitted from the core network 17 to the serving femtocell 13, the serving femtocell 13 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 on the target side (S113, S115).

The terminal 11 completes Radio Bearer Reconfiguration and transmits Complete to the target. At this time, the connection between the terminal 11 and the serving femtocell 13 is disconnected (S117).

When the target system 15 transmits a Relocation Complete message to the core network 17 to inform the Acquisition of the terminal (S119), the core network 17 transmits an IU Release Command message to the serving femtocell 13 to serve the femtocell 13 Request release of the resource (S121).

The serving femtocell 13 transmits an IU Release Complete message to notify the release of resources to complete the handover (S123). Through the above process, a hard handover is performed between the femtocell and the macro cell, and the terminal 11 receives a service from the target system 15.

In the general SRNS Relocation Hard Handover procedure according to the 3rd Generation Partnership Project (3GPP) standard, the serving femtocell 13 transmits the current service history in a 'Relocation Required' message as in step S105. In step S109 of the procedure of Figure 1, the target system 15 receives the current service history, by allocating resources to reflect the current service history to ensure the consistency of services for the terminal to be handed over.

However, if the current service history is unacceptable in the target system 15, the target system 15 may configure the resource with other settings that ensure call continuity. If the resource configuration is not possible with other settings, the target system 15 rejects the handover inflow by sending a failure message for the request of the serving femtocell 13.

2 is a diagram illustrating a handover procedure when a target macro cell does not support the current service history. Of the steps of FIG. 2, the same procedure as that of the handover procedure of FIG. 1 has been given the same identification number, and may be described in the same manner except as specifically described below.

In step S107, the target system 15 receiving the Relocation Request message from the core network 17 determines whether the service according to the current service history included in the Relocation Request message is possible, if it is determined that the service cannot be provided ( S201), the message 'Relocation Failure' is transmitted to the core network 17 to inform that the resource allocation has failed because service cannot be accepted (S203).

The core network 17 transmits a 'Relocation Preparation Failure' message to the serving femtocell 13 to inform the fact that the resource allocation has failed due to the service unacceptability in the target system 15 (S205).

The serving femtocell 13 checks the reason for 'Relocation Preparation Failure' and transmits a radio bearer reconfiguration message to the terminal 11 to change to another service acceptable in the target system 15 (S207).

The terminal 11 performs service reconfiguration and transmits a Radio Bearer Reconfiguration Complete message to the serving femtocell 13 to inform the completion of the reconfiguration (S209).

The serving femtocell 13 transmits a 'Relocation Required' message to the core network 17 to perform the handover, and the core network 17 provides the relocation request message to the target system 15. Since the current service history included in the newly provided 'Relocation Required' message is that the target system 15 can accommodate, resource allocation does not fail (S211, S213).

Here, steps S211 and S213 are the same steps as S105 and S107 of FIG. 1. Thereafter, the procedure is performed in the same manner as in steps S109 to S123 of FIG. 1 to complete the handover.

As such, when the hard handover is performed from the femto base station to the macro cell, the target macro cell does not support the setting details of the femtocell and may be rejected. In this case, the femtocell may retry the handover by changing the service history of the terminal.

However, since the femtocell itself is a system having a relatively small service area and a low output, the service may be terminated due to signal quality problem while performing this repetitive procedure. In addition, since the procedure of steps S201 to S209 of FIG. 2 should be further performed, the time of handover is inevitably delayed, and this delay lowers the probability of success due to the nature of hard handover.

An object of the present invention, when handing over from a femtoCell system to a MacroCell system, it is possible to prevent the failure of the handover in advance by excluding the service configuration that is not supported by the macro cell in advance. There is provided a femtocell base station and a hard handover method thereof.

According to the present invention for achieving the above object, a hard handover method between a femtocell base station and a macro cell of a serving cell, a service being provided to the terminal before the femtocell base station provides a Relocation Required message for handover to the core network; Determining whether a detail is a service that can be provided by the macro cell; If it is determined that the service history is a service that cannot be provided by the macro cell, the femtocell base station generating service history information in which the service history is modified to a range in which the macro cell is serviceable; And the femtocell base station including information on the modified service history in the relocation required message. Accordingly, the macro cell allocates resources for handover according to the modified service details.

Since the modified service details are adjusted in the serviceable range of the macro cell, the resource allocation according to the modified service details does not occur in the macro cell, and the handover procedure is delayed because the resource allocation fails. Or the service itself is terminated during handover.

According to an embodiment, when it is determined that the service history provided by the femtocell base station to the terminal is a service that can be provided by the macro cell, the relocation required message is a service that the femtocell base station provides to the terminal. It will contain information about the details.

According to another embodiment, the step of including information on the modified service history may include changing the at least one of information elements related to the setting of the service history in the format of the Relocation Required message to the Relocation Required message. Information about the modified service history may be included.

According to an embodiment of the present disclosure, it is preferable that the modified service history satisfies a predefined protocol regarding the Relocation Required message format, satisfies a service range of the macro cell, and satisfies a service range acceptable to the terminal. .

According to another embodiment of the present invention, a femtocell base station operating as a serving cell and performing hard handover to a macro cell while providing a service to a terminal includes a memory, a service determination unit, an information correction unit, and a data processing unit.

Information on a service range supported by the macro cell is stored in a memory. Before providing the relocation required message for the handover to the core network, the service determination unit determines whether the service history being provided to the terminal is a service that can be provided by the macro cell based on the information stored in the memory. Provide the results to the information reviser.

When the information correcting unit receives a determination result from the service determining unit that the service description is a service that cannot be provided in the macro cell, the information correcting unit generates service history information in which the service history is modified to a serviceable range of the macro cell.

The data processor includes the information on the modified service history in the Relocation Required message and transmits the information to the core network to perform the handover procedure.

Handover in a mobile communication system is a very important function for the service guarantee of the terminal. In addition, in the case of a hard handover method, the success rate may vary greatly depending on the timing of the handover attempt.

To this end, when the service femtocell currently serving the terminal is a service that cannot be provided by the target macro cell, the femtocell of the present invention is present in the 'Relocation Required' message provided to the core network for hard handover. Instead of including the service history provided to the terminal unilaterally, the service history modified to the service history that can be provided by the target macro cell is included so that the resource allocation fails in the target cell and the handover is delayed or not. Make sure that you don't have a problem that breaks up the arc.

1 is a flowchart provided to explain a handover procedure of a UE Involved SRNS Relocation 'scheme;
2 is a diagram illustrating a handover procedure when a target macro cell does not support setting details of a femtocell serving cell;
3 schematically illustrates a femtocell system of the present invention, and
4 is a view provided to explain a handover method according to an embodiment of the present invention, and
5 is a block diagram schematically illustrating a femtocell base station 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 present invention proposes a method for controlling hard handover between a femtocell acting as a serving cell and a macro cell acting as a target cell. The overall progression method of hard handover between the serving femtocell and the target macro cell, which is the basis of the present invention, may be any method known in the art as well as the handover method of FIG. 1.

In addition, the hard handover method between the femtocell and the macro cell in the present invention is mainly applied to a data call, but is not necessarily limited thereto, and may be applied to a voice call or a video call.

Referring to FIG. 3, the entire coverage (or part thereof) of the femtocell S is included in the macro cell T of the macro base station 19. The femtocell system of the present invention includes a femtocell base station 301 and an access gateway (AGW) 303 that connects the femtocell base station 301 to a core network (CN) 17.

The femtocell base station 301 operates in the same manner as the femtocell base station 13 of FIG. 1 except for an algorithm or configuration related to the 'modified service history' specifically proposed in the present invention and described below, and operates a wireless network controller function. It is possible to interwork with the radio network controller 15 and the macro base station 19 separately through the access gateway 303. In the following description, when the 'femtocell (S)' is used interchangeably in a device sense, it may be understood to mean 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 17. Therefore, in the following description, when the femtocell S or the femtocell base station 301 transmits a message to the core network 17, it should be understood that it is transmitted via the gateway 303 even if not mentioned otherwise.

The mobile switching center (MSC) 17 is represented by representing the core network 17. In the present invention, unless otherwise indicated, the MSC 17 and the core network 17 are used interchangeably. The core network 17 connects information or calls between the femtocell S and the macro cell T.

The macro cell T is implemented by a radio network controller (RNC) 15 and a macro base station (Node B) 17. Since the target role of the hard handover is mostly performed by the radio network controller 15, the operation of the macro base station 19 and the control of the radio network controller 15 with respect to the macro base station 19 are not mentioned separately. Therefore, in the following description, when the 'macro cell T' is used interchangeably in an apparatus sense, it may be understood to mean the 'wireless network controller 15 of the macro cell T'.

The radio network controller 15 is also the same apparatus as the conventional radio network controller except that it further includes an algorithm or configuration relating to the 'modified service history' of the present invention.

In FIG. 3, the terminal 11 is moving from the femtocell S to the macro cell T, and thus a handover may occur between the femtocell S and the macro cell T. Information required for resource setting of the target macro cell T in a 'Relocation Required' message, which is a RANAP (Radio Access Network Application Part) message that the serving femtocell S of the present invention also provides to the core network 17 for hard handover. Includes.

However, the information necessary for the resource setting does not include the service history (hereinafter, simply referred to as 'current service history') currently provided by the terminal 11 in the serving femtocell S, but not included in the target macro cell. There is a feature of the present invention in that it includes a 'modified service history', which is a virtual service history that selectively changes all or part of the service history according to the service range.

'Modified service history' is a macro cell if the current service history that the terminal 11 is being provided in the actual serving femtocell (S) is a service that cannot be provided in the macro cell (T). Information on the service history changed to support (T). Therefore, the 'modified service history' is information on the service information different from the resource information that the terminal 11 was actually served by the serving femtocell S, and the current service history of the terminal 11 is supported by the macro cell T. Used when not. For example, when the terminal 11 is currently receiving data service at a 10 Mbps speed, but the macro cell T does not support the 10 Mbps speed, the serving femtocell S may set the support rate to the macro cell T. You will create a 'Modified Service History' that changes within this support.

Through this, the target macro cell T transmits a 'Relocation Failure' message to the core network 17 so that an event that fails to allocate resources does not occur because the current service history is unacceptable. It is possible to proceed with the handover procedure at once without performing step S209.

The 'modified service history' corresponds to a change in at least one of a plurality of elements included in the 'Relocation Required' message to a virtual value. This will be described again below.

Since femtocell base station 301 basically performs both a role of a base station and a role as a wireless network controller, the femtocell base station 301 should include various configurations for providing a corresponding function on a mobile communication service. In addition, the femtocell base station 301 of the present invention specifically includes a memory 501, a service determination unit 503, an information correction unit 505 and a data processing unit 507 as shown in FIG. To be able to perform actions related to the 'service history.' For reference, FIG. 5 illustrates only the components necessary for the description of the present invention, and omits the configuration necessary for the overall operation of the femtocell base station 301, and also the description thereof.

Hereinafter, with reference to FIGS. 4 and 5, the hard handover procedure and the operation of the detailed configuration of the femtocell base station 301 using the femtocell base station 301 of the present invention as the serving cell and the macro cell T as the target cell will be described. .

Since the handover procedure of FIG. 4 is based on the WCDMA protocol, the handover procedure of steps S101 to S123 of FIG. 1 is basically included as it is, and the corresponding procedure is naturally described in the same manner. Hereinafter, what is described as the operation of the serving femtocell S corresponds to the operation of the femtocell base station 301, and what is described as the operation of the target macro cell T corresponds to the operation of the radio network controller 15.

The serving femtocell S transmits a measurement control message to the terminal 11 in which call setup is completed, instructs a neighbor list and a measurement method (S401), and the terminal 11 responds to the measurement control message. Accordingly, when an event condition is satisfied while monitoring base stations of an active set and a monitored set (or a neighboring cell), a measurement report is transmitted to the serving femtocell S (S403).

If the serving femtocell S determines that handover by a specific event is necessary based on the measurement result, the serving femtocell S determines whether the 'current service history' provided to the terminal 11 can be serviced in the macro cell T. . For this determination, the memory 501 of the femtocell base station 301 should previously store information on the supportable service range of the target macro cell T. Since the current service history is known by the serving femtocell S, the service determination unit 503 of the femtocell base station 301 may receive the current service history from the macro cell T based on the information stored in the memory 501. It may be determined whether there is (S405).

In operation S405, the determination result of the service determination unit 503 is provided to the information correction unit 505. When the determination result that the current service history is not available to the macro cell T is provided, the information correction unit 505 is provided. ) Generates a 'modified service history' in which the current service history is changed to a service history supported by the macro cell T. For example, when the terminal 11 is currently receiving data service at 10 Mbps, but the macro cell T does not support the 10 Mbps speed, the data service rate is within a range that the macro cell T can support. The modified 'modified service history' is created (S407).

The serving femtocell S, that is, the data processing unit 507 of the femtocell base station 301 transmits a 'Relocation Required' message including the 'modified service details' to the core network 17 instead of the 'current service details'. (S409).

The core network 17 transmits a relocation request message to the target macro cell T (S411), and the target macro cell T allocates resources according to the contents of the relocation request message, and then relocations to the core network 17. Sends a Request Ack message to inform the completion of Bearer Setup. Since the target macro cell T determines that the 'modified service history' is within a serviceable range, the target macro cell T prepares a handover by allocating resources according to the 'modified service history' (S413 and S415).

When the relocation command message is transmitted from the core network 17 to the serving femtocell S, the serving femtocell S transmits a radio bearer reconfiguration message to the terminal 11 according to the contents of the relocation command. The RRC message includes resource allocation information of the target side according to the 'modified service details' (S417 and S419).

The terminal 11 completes the radio bearer reconfiguration and transmits a complete message to the target macro cell T. At this time, the connection between the terminal 11 and the serving femtocell (S) is disconnected (S421).

When the target macro cell (T) transmits a Relocation Complete message to the core network (17) to inform the Acquisition of the terminal (S423), the core network 17 transmits an IU Release Command message to the serving femtocell (S) to serve the femtocell ( A resource release of S) is requested (S425).

The serving femtocell (S) completes the handover by transmitting an IU Release Complete message to notify the release of resources (S427). Through the above process, the hard handover between the femtocell and the macro cell is performed immediately without performing the steps S201 to S209 of FIG. 2, and the terminal 11 is stably serviced by the target macro cell T.

If, as a result of the determination in step S405, the service history currently provided to the terminal 11 can be serviced in the macro cell T, the operation after the step S405 is the same as the operation after the step S105 of FIG. Become.

Hereinafter, the 'Relocation Required' message including the 'modified service details' will be described.

The 'Relocation Required' message includes many information elements for defining the service setting details shared by the terminal 11 and the system. The modified service details are set by changing at least one of these plurality of information elements. For example, by changing the 'Transport Channel Information' information item among the information items of the 'Relocation Required' message, the virtual 'modified service details' different from the 'current service details' actually being serviced may be set.

Therefore, in setting the modified service history, the serving femtocell (S) should (1) be in conformity with the protocol regarding the 'Relocation Required' message, and (2) the macro cell should be included in the serviceable range. (3) Of course, the terminal 11 should be able to be serviced. Naturally, it would be desirable to set the macro cell to have the best condition among those included in the serviceable range.

In general, it may be desirable to set several models of 'modified service details' in consideration of differences in service ranges of the femtocell S and the macro cell T, and select one of them.

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 (7)

In a hard handover method between a femtocell base station and a macro cell of a serving cell,
Storing, by the femtocell base station in advance, information on a service range supported by the macro cell targeted;
Before the femtocell base station provides the relocation required message for handover to the core network, determining whether the service history provided to the terminal is a service that can be provided by the macro cell based on the information of the storing step; ;
If it is determined that the service history is a service that cannot be provided by the macro cell, the femtocell base station generating service history information in which the service history is modified to a range in which the macro cell is serviceable; And
And the femtocell base station including information on the modified service history in the relocation required message to allow the macro cell to allocate resources according to the modified service history and to perform a handover procedure. Hard handover method of femtocell base station.
The method of claim 1,
As a result of the determination, when it is determined that the service history provided to the terminal by the femtocell base station is a service that can be provided by the macro cell, the relocation required message includes information on the service history provided by the femtocell base station to the terminal. Hard handover method of a femtocell base station characterized in that it comprises as it is.
The method of claim 1,
Including the information on the modified service history,
And performing at least one of information elements related to setting of service details in a format of the relocation required message.
4. The method according to any one of claims 1 to 3,
The modified service history satisfies the predefined Relocation Required message format, satisfies the service range of the macro cell, and satisfies the service range acceptable to the terminal. Handover method.
A femtocell base station which performs a hard handover to a macro cell while serving as a serving cell while providing a service to a terminal,
A memory having information on a service range supported by the macro cell;
A service determination unit determining whether a service history provided to the terminal is a service that can be provided by the macro cell based on the information stored in the memory before providing a Relocation Required message for handover to the core network; And
An information correction unit for generating service history information in which the service history is modified to a serviceable range of the macro cell when the service decision unit receives a determination result that the service history cannot be provided by the macro cell; And
Including the data processing unit for transmitting to the core network including the information on the modified service history in the Relocation Required message to allow the macro cell to allocate resources according to the modified service history and proceed with the handover procedure A femtocell base station characterized in.
The method of claim 5,
Wherein the data processing unit comprises:
The femtocell, characterized in that the information on the modified service history is included in the relocation required message by changing at least one of the information elements related to the setting of the service history in the format of the relocation required message according to the modified service history. Base station.
The method according to claim 5 or 6,
The modified service history, the femtocell base station, characterized in that it satisfies the previously defined protocol for the Relocation Required message format, and satisfies the service range of the macro cell, the terminal can accommodate the service range.

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