KR101231778B1 - Femto System and Handover Method thereof - Google Patents

Abstract

A femtocell handover method and a femtocell system thereof are disclosed. The handover method of the present invention enables a target femtocell to receive handover related information of a serving femtocell through femtocell interfemtra handover in a femtozone including a plurality of femtocells. Accordingly, the call handed in to the target femtocell can be restrained from being returned to the serving femtocell before, to improve the overall call quality in the femtozone. In addition, when the target femtocell becomes a serving femtocell, it may apply various call quality improvement algorithms using various information provided from the serving femtocell in the previous handover process.

Description

Femto System and Handover Method Technical Field

The present invention relates to a femtocell handover method and a femtocell system for improving handover success rate between femtocells in a femtozone having a plurality of femtocells by improving call processing of a target base station that has performed a handover. will be.

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.

Handover of a femtocell installed alone is performed with a macro cell. Since the macro base station has a much wider range of service and a more stable signal quality than the femtocell, it is necessary to block handover attempts to return to the femtocell once the terminal is handed over to the macro base station. To do this, by handing over from the femtocell to another frequency of the macro base station, it is possible to prevent an attempt to return from the macro base station side again. A blind handover or an inter frequency handover is used as a method for handing over to a macro base station.

A femtozone is a case in which a plurality of femtocells are overlapped with each other for the purpose of extending a service range, and handover may occur between femtocells in a femtozone. In this case, the femtocell-to-femtocell handover supports hard handover rather than soft handover due to its limited resources.

Hereinafter, a conventional hard handover process between femtocells will be described with reference to FIG. 1.

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. do. Since femtocells do not support soft handover, there is one active set, and event conditions 1a, 1c, 1d, 1e, and 1f may be used. For example, the event condition 1f is completed when the reference value of the active set becomes lower than the reference value 1f (S103).

The serving femtocell 13 transmits a direct transfer message to an access gateway (AGW) 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 includes information necessary for resource setting of a target Radio Network Controller (RNC) (S105).

The access gateway 17 transmits a relocation request message to the target femtocell 15 (S107), and the target femtocell 15 allocates a resource according to the content of the relocation request message, and then sends it to the access gateway 17. By sending a Relocation Request Ack message to inform that the bearer setup is complete (S109, S111).

When the access gateway 17 transmits a relocation command message 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 target femtocell 15 prepares internal resources and transmits a Relocation Detect message to the access gateway 17 (S117, S119).

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 (S121).

When the target femtocell 15 transmits a Relocation Complete message to the access gateway 17 to inform the Acquisition of the terminal (S123), the access gateway 17 transmits an IU Release Command message to the serving femtocell 13 to serve the femtocell 13. Request to release the resource (S125).

The serving femtocell 13 transmits an IU Release Complete message to notify the release of resources to complete the handover (S127). Through the above process, a hard handover is performed between femtocells, and the terminal 11 receives a service from the target femtocell 15.

In femtozones made for the purpose of expanding the service range, handover between femtocells can occur frequently, and handover between femtocells is hard handover, so frequent handovers are inevitably degrading call quality.

Frequent handovers between such femtocells include significant handovers back to the original serving femtocell. However, due to the narrow reception radius of the femtocell base station, radio interference is more severe than the macro cell, and especially when the femtocell base station is installed in a building, signal fluctuation frequently occurs due to the movement of a person or the opening and closing of a door. This is a problem because the handover to which the (Hand-In) call immediately returns to the original serving femtocell 13 may occur frequently not because of the movement of the terminal 11 but because of such signal interference.

 Referring to FIG. 2, a handover between the serving femtocell 13 and the target femtocell 15 using two FAs (Frequency Assignment) may be made between the same FAs (case 1) or between different FAs. There is also a number (case 2). In either case, handovers (①, ②) may be returned to the original serving femtocell 13.

For this reason, stable call quality can be achieved only by appropriately blocking handover between femtocells in the femtozone, in particular, handover back to the serving femtocell.

To this end, the target femtocell needs to control the handover using the related information of the serving femtocell. However, to date, the SRNS Relocation Handover procedure regarding handover of a serving system in the Wideband Code Division Multiple Access (WCDMA) protocol, such as 3GPP TS 25.413, does not provide a way for a target femtocell to receive this information of a serving femtocell. .

After the femtocell inter- handover is completed, the target femtocell needs information about the serving femtocell even when the target femtocell intends to perform a blind handover to the macro cell.

The blind handover is one of the handovers performed mechanically according to the network feasible of the target femtocell 15 without the measurement result of the terminal 11 at the time when call setup is completed. Since some core networks do not support handover that occurs during call setup, blind handover is performed at the completion of call setup.

However, in the case of inter-femtocell handover that does not go through the core network, handover is supported even during call setup. Therefore, the target femtocell 15 needs to determine whether handover is performed while the call setup is performed in the serving femtocell 13. There is. However, conventional femtocells have no way of verifying this information.

It is an object of the present invention to provide a femtocell handover method and a femtocell system for providing femtocell information to a serving femtocell in a femtocell inter-over handover to increase the handover success rate between femtocells.

Another object of the present invention is to provide a femtocell handover method and a femtocell system for improving call quality in a femtocell by improving the processing of a call received by a target femtocell using handover information received from a serving femtocell through handover. In providing.

The femtocell handover method of the present invention for achieving the above object comprises the steps of: a serving femtocell base station that determines the handover whether the target side to perform the handover is a femtocell; If a target side is a femtocell, recording a cell ID and preset handover information in a relocation required message transmitted from the serving femtocell base station to an access gateway; A target femtocell base station receiving a relocation request message including the cell identifier and handover information from the access gateway and checking the cell identifier to determine whether a serving side is a femtocell; And when the serving side is a femtocell, the target femtocell base station storing the cell identifier and the handover information while completing the handover.

Here, in the determining whether the serving side is a femtocell, the target femtocell base station determines a femtocell for the serving side when a radio network controller identifier (RNC ID) included in the cell identifier is the same as its radio network controller identifier. Judging by

According to an embodiment, the femtocell system of the present invention can maintain improved call quality by using the information stored in the storing step.

<Use of Stored Information 1>

The method includes providing a service for the handed over call while operating a blocking timer when the target femtocell base station completes the handover according to the storing step; When the new handover event for the call occurs, determining, by the target femtocell base station, whether the target side of the new handover is the serving femtocell base station; And when the target femtocell base station is the serving femtocell base station and the blocking timer has not exceeded the reference time, the target femtocell base station ignores the new handover event. The call may limit the attempt to return to the serving femtocell immediately before. This is because these attempts are often caused by irregular radio environment changes due to poor radio environment of femtocells.

<Use of Saved Information 2>

In another example, the cell identifier and the handover information may be recorded in a 'Last known UE Position' parameter in a relocation request or relocation request message. For example, the cell identifier is recorded in a 'Cell ID' item of the 'Last known UE Position' parameter, and the handover related information is recorded in a 'System Frame Number (SFN)' item of the 'Last known UE Position' parameter. The call type information and the NAS signal information recorded in the 'Position Information' item.

Based on this information, the method may further comprise: after the storing, determining, by the target femtocell base station, whether the handed over call is a blind handover to a macro base station; And if the call is a blind handover target, proceeding with the blind handover at the time when call setup is completed. At this time, the target femtocell base station determines whether the call is handed over during call setup or handover after call setup is completed, based on the NAS signal information.

Further, in the blind handover, the target femtocell determines whether the call is an outgoing call or an incoming call based on the call type information, and when the call is a preset call type when the call setup is completed. After waiting a preset time, the blind handover may proceed.

According to another embodiment of the present invention, a femtocell system for forming a femtozone located in a macro cell including a serving femtocell base station and a target femtocell base station performing the above handover method, and an access gateway connecting the femtocell base station to a core network. Is to suggest.

In the present invention, a handover between femtocells that can occur while configuring a femtozone with a plurality of femtocell base stations complying with Wideband Code Division Multiple Access (WCDMA) protocol can be effectively controlled.

To this end, the target femtocell of the present invention can receive the handover related information from the serving femtocell using the Relocation Required message and the Relocation Request message of the RANAP message, and the call hand-ined using the information. By suppressing the return to the serving femtocell to the maximum, it is possible to prevent the meaningless handover between the femtocell is repeated.

In addition, the target femtocell uses the information provided by the serving femtocell to control the blind handover attempt to the macro base station to increase the handover success rate in the femtozone. Can be.

1 is a flowchart provided to explain a hard handover method of a conventional femtocell base station;
2 is a diagram provided to explain handover between femtocells,
3 illustrates a femtozone including a femtocell base station of the present invention;
4 is a flowchart provided to explain a handover method in a femtocell base station of the present invention, and
5 is a diagram illustrating a message format including a 'Last known UE Position' parameter according to 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 handover between femtocells in a femtozone consisting of a plurality of femtocells. In particular, by providing a method of delivering some information of a serving femtocell to a target femtocell in a femtozone, the target femtocell can use the serving femtocell information to process a hand-in call. Allow handover in the femtozone to be performed effectively.

In addition, the overall progression method of the hard handover between the serving femtocell and the target femtocell may be any method known in the art as well as the handover method of FIG. 1.

Referring to FIG. 3, the entire coverage (or part thereof) of the femtozone C is included in the macro cell M of the macro base station 23. The femtozone C includes a plurality of femtocell base stations 101 to 105, and an access gateway (AGW) 110 connecting the femtocell base stations 101 to 105 to a core network.

Each femtocell base station 101 to 105 in the femtozone C operates in the same manner as the femtocell base stations 13 and 15 of FIG. 1 except for the specially proposed in the present invention, and has an access control gateway having a radio network controller function. It is possible to interwork with the macro base station 23 separately through 110.

However, each of the femtocell base stations 101 to 105 individually forms one femtocell, but the femtocell coverage overlaps each other to form a femtozone (C). In addition, the femtocell base stations 101 to 105 in the femtozone C have the same Radio Network Controller Identifier (RNC ID). In the following description, a "femtocell" and a "femtocell base station" may be used interchangeably, but it is basically meant the same system or configuration.

The access gateway 110 connects the plurality of femtocell base stations 101 to 105 to the core network, and may be described in the same manner as the access gateway 17 of FIG. 1 except for the portions described below.

The access gateway 110 groups and manages a plurality of femtocell base stations 101 to 105 in the femtozone C by the same radio network controller identifier (RNC ID). Since femtocells adjacent to each other are managed with the same RNC ID, two femtocells performing handover use the same RNC ID.

The present invention relates to a specific parameter of a relocation required message and a relocation request message, which is a Radio Access Network Application Part (RANAP) message transmitted and received between the femtocell base stations 101 to 105 and the access gateway 110. By redefining, information of the serving femtocell is transmitted to the target femtocell. The Relocation Request message is a message received by the target system from the core network in a handover situation. The SRNS Relocation Info is generated by the Radio Network Controller (RNC) of the serving system and displayed in the Relocation Required message and the Relocation Request message. Is sent.

Hereinafter, a handover procedure between femtocell base stations 101 to 105 of the present invention will be described with reference to FIG. 4. For convenience of explanation, the following description will focus on a handover in which the first femtocell base station 101 is used as a serving system and the second femtocell base station 103 is used as a target system. Since the handover procedure of FIG. 4 is based on the WCDMA protocol, the handover procedure of steps S101 to S127 of FIG. 1 is basically included as it is, and the corresponding procedure is naturally described in the same manner.

The serving femtocell 101 transmits a measurement control message to the terminal 11 in which call setup is completed as in step S101 (S401), and the terminal 11 sends a measurement report according to the measurement control message (S103). It transmits to the serving femtocell 101 as in step (S403).

<The serving femtocell transmits handover related information to the target femtocell: steps S405 and S407.

When the serving femtocell 101 determines that a handover by a specific event is necessary based on the measurement result of the terminal 11, the serving femtocell 101 determines whether the target system is a femtocell based on the RNC ID of the target system to which the call is to be handed over ( S407), when the target system is a femtocell, the handover related information of the present invention is recorded in the 'Last known UE Position' parameter proposed below (S409).

As described above, since the plurality of femtocell base stations 101 to 105 in the femtozone (C) are grouped with the same radio network controller identifier (RNC ID), the serving femtocell 101 is a system in which the target system has the same RNC ID. If it is a system using the same RNC ID, handover-related information is set in the 'Last known UE Position' parameter below.

The 'Last known UE Position' parameter in which the serving femtocell 101 records its handover related information is included in the relocation required message of the RANAP message. 5 is a relocation request message (or 'Relocation Request' message) which is a RANAP message.

Referring to FIG. 5, Last known UE Position information is included in UE Information elements in RRC Container information among Source RNC To Target RNC Transparent Container items in a RANAP Relocation Required message.

The reason for using the 'Last known UE Position' parameter to transmit the handover related information to the target femtocell is that the source RNC To Target RNC Transparent Container information is directly transmitted from the serving system to the target system. This is because (Node) does not modify this part. In addition, the 'Last known UE Position' parameter in the RRC Container is information for informing the target system of the final position of the terminal 11 when handover between macro systems complying with the WCDMA protocol. This is because the femtocell having the terminal 11 may be used for other purposes because the final position of the terminal 11 becomes the serving femtocell itself.

Handover related information included in the 'Last known UE Position' parameter is shown in Table 1 below.

SFN  Set call type information set in serving femtocell Cell ID  Set cell ID of serving femtocell (including RNC ID) Position Information Set handover related information of serving femtocell
(Variable Data Length)

In the SFN (System Frame Number), call type information of a call that the serving femtocell attempts to handover is recorded. Call type information is information on whether the corresponding call is an outgoing call or an incoming call.

Cell ID sets a Cell ID (cell identifier) of the serving femtocell, and the Cell ID includes the RNC ID.

'Position Information' configures handover related information of the serving femtocell. The handover related information may include various information for the handover operation of the target femtocell 103. For example, 'NAS (Non Access Spectrum) Signal Information' for a blade handover to be described below may be included.

After step S405, the serving femtocell 101 transmits a direct transfer message to the access gateway 110. This message includes a 'Relocation Required' message, which is a RANAP message, and when the target system is a femtocell, handover related information to be provided to the target femtocell 103 is included in the 'Last known UE Position' parameter (S409).

<Provide RANAP Relocation Request message from access gateway: step S411>

Upon receiving the 'Relocation Required' message, the access gateway 110 transmits a RANAP Relocation Request message to the target femtocell 103. The 'Last known UE Position' parameter of the RANAP Relocation Request message of the present invention includes information provided by the serving femtocell 101 as it is. In other words, when the serving system is a femtocell, the RANAP relocation request message transmitted to the target femtocell 103 has the same form as that of FIG. 5.

<Extract and store information related to handover of target femtocell: S413, S415>

The target femtocell 103 that receives the RANAP Relocation Request message from the access gateway 110 in step S411 checks the cell ID of the parameter to determine whether the femtocell inter-femble is handover.

The target femtocell 103 recognizes handover between femtocells when the RNC ID extracted from the cell ID of the parameter is the same as its own RNC ID, and stores the handover information transmitted by the serving femtocell 101 in its own storage medium (not shown). Store in If the serving system is a femtocell, since the target femtocell 103 receives the RANAP Relocation Request message of the same type as in FIG. 5, the target femtocell 103 checks the same RNC ID as its own.

If the RNC ID included in the Cell ID is different from its own RNC ID or the corresponding 'Last known UE Position' parameter part is missing, it is determined as a handover request from the macro base station 23 and according to the conventional WCDMA protocol. Perform the corresponding action.

Although the Cell ID is defined in the 'Last known UE Position' parameter (in the conventional case) transmitted by the macro base station 23, it is not the Cell ID information of the serving system but the cell information where the terminal 11 is finally located. In addition, the Last known UE Position parameter is not mandatory but is not necessarily included because it is an optional field.

After the step S415, the handover process between the serving femtocell 101 and the target femtocell 103 is the same as the steps S109 to S127 of FIG. 1.

In this manner, handover information is provided by the serving femtocell 101 according to the present invention.

<Handover Control Operation of Target Femtocell: S430>

The handover related information of 'Position Information' received and stored by the target femtocell 103 from the serving femtocell 101 is applied when the target femtocell 103 becomes a serving system again, and the target femtocell 103 is a serving femtocell. The subsequent handover is controlled based on the handover related information received from 101 as follows.

Suppressing attempts to return to a previous serving femtocell

As is clear from the background art, a radio interference phenomenon is more severe than a macro cell due to a narrow reception radius. In particular, when a femtocell base station is installed in a building, signal fluctuation may occur frequently due to human movement or opening and closing of a door. In this case, an attempt may be made to directly hand-out a call handed into the target femtocell 103 to the original serving femtocell 101.

However, the target femtocell 103 of the present invention can appropriately suppress a handover attempt to return to the serving femtocell 101 by using the Cell ID of the received handover related information.

Regarding the handover control method based on such information, the applicant has already filed Korean Patent Application No. 10-2010-0127440. The handover information of the present invention can be applied to such a control method.

According to this, when the target femtocell 103 receives a hand in call from another cell (the previous serving femtocell), the blocking timer can be operated at the time when the target femtocell 103 is handed over. .

In this case, when the target femtocell 103 determines that it is time to proceed with a new handover based on the measurement result of the terminal 11, the target femtocell 103 determines whether the target femtocell 101 is involved in the previous handover. If the target system is found to be the serving femtocell 101 involved in the previous handover, the target femtocell 103 determines whether the time counted to the blocking timer so far exceeds the reference time and does not exceed the reference time. Ignore the measurement result and do not proceed with handover.

Through this operation, the target femtocell 103 can suppress the handover of returning the handed-in call back to the serving femtocell 101 due to an irregular change in the signal environment. Only when the hand-in and the predetermined reference time is exceeded, it is determined that the handover by the movement of the terminal (11). Of course, as soon as the hand is actually handed in, the handover sent back to the serving femtocell 101 may occur due to the movement of the terminal 11, but the handover delay of about a reference time is not a problem and unnecessary handover as described above is performed. There is a big effect of limiting.

Determination of blind handover to macro base station

As described in the background art, blind handover is performed according to the determination of the target femtocell 103 itself (Network Initiated, user setting) without the measurement result of the terminal at the time of call setup. One of the handovers. For example, a blind handover may be performed when a voice call flows into a data dedicated femtocell or a call of a subscriber not registered in a registered subscriber femtocell flows. The target femtocell 103 determines the blind handover immediately upon completion of the handover.

However, since some core networks do not support handover that occurs during call setup, blind handover should be performed at the completion of call setup (condition 1). In addition, according to the network design, in order to maintain a time interval between handovers occurring at almost the same time in both the calling terminal and the called terminal, a specific call (called call or incoming call) is first set to blind handover (condition 2).

In relation to condition 1, since handover is supported even during call setup in the case of inter-femtocell handover that does not go through the core network, the target femtocell 103 performs handover while the call setup is performed in the serving femtocell 101. It is necessary to determine whether or not. If handover between femtocells occurs during call setup, the target femtocell 103 must wait for the completion of the call setup procedure to attempt blind handover to the macro cell (M).

In addition, even when the call setup is completed in the serving femtocell 101 but the inter-femtocell handover is performed while the blind handover is not started, the target femtocell 103 determines this and performs the blind hand to the macro cell M. FIG. Over must be initiated.

To this end, the target femtocell 103 can extract information on the call setup progress state from the 'NAS Signal Information' received from the serving femtocell 101 through the 'Position Information' parameter of 'Last known UE Position'. In other words, the target femtocell 103 checks whether the serving femtocell 101 has received the 'Connetion Ack' in the 'NAS Signal Information' and confirms that the call setup is completed.

If the 'Connetion Ack' is not received, the target femtocell 103 completes the handover of FIG. 4 and waits for the 'Connetion Ack' before proceeding with the blind handover. If the 'Connetion Ack' is received, the target femtocell 103 proceeds with the blind handover at the moment when the handover of FIG. 4 is completed.

For condition 2, the target femtocell 103 determines whether a call introduced from call type information (Call Type) received from the serving femtocell 101 through the SFN parameter of 'Last known UE Position' is an originating call or an incoming call, As described above, the blind handover time may be controlled. For example, if the incoming call is set to proceed with a blind handover first and the call introduced through the handover of FIG. 4 is an outgoing call, the target femtocell 103 waits for a preset time and then blinds the incoming call. Proceed to over.

Through this, it is possible to solve the problem that the start of the blind handover could not be determined because it is not possible to determine whether the call setup is completed in the serving femtocell in the conventional target system, and the call in the femtozone (C) through the blind handover You can improve the quality.

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 (14)

In the femtocell handover method,
Determining, by the serving femtocell base station having determined the handover, whether the target side to proceed with the handover is a femtocell;
If a target side is a femtocell, recording a cell ID and preset handover information in a relocation required message transmitted from the serving femtocell base station to an access gateway;
A target femtocell base station receiving a relocation request message including the cell identifier and handover information from the access gateway and checking the cell identifier to determine whether a serving side is a femtocell;
If the serving side is a femtocell, the target femtocell base station storing the cell identifier and handover information while completing the handover;
Providing, by the target femtocell base station, a service for the handed over call while operating a blocking timer;
When the new handover event for the call occurs, determining, by the target femtocell base station, whether the target side of the new handover is the serving femtocell base station; And
When the target femtocell base station is the serving femtocell base station and the blocking timer has not exceeded the reference time, the target femtocell base station includes disregarding the new handover event. Way.
The method of claim 1,
In determining whether the serving side is a femtocell,
And the target femtocell base station determines the serving side as a femtocell when a radio network controller identifier (RNC ID) included in the cell identifier is the same as its radio network controller identifier.
delete The method of claim 1,
The cell identifier and the handover information are recorded in a 'Last known UE Position' parameter in a relocation request or relocation request message.
5. The method of claim 4,
The cell identifier is recorded in a 'Cell ID' item of the 'Last known UE Position' parameter.
The handover related information may include call type information recorded in a 'SFN (System Frame Number)' item of the 'Last known UE Position' parameter, and NAS (Non Access Spectrum) Signal Information recorded in a 'Position Information' item. A femtocell handover method.
The method of claim 5,
After the storing, determining, by the target femtocell base station, whether the handed over call is a target of a blind handover to a macro base station; And
If the call is a blind handover target, the target femtocell base station determines whether the call is handed over during call setup or handover after call setup is completed based on the NAS signal information, and call setup is completed. Femtocell handover method comprising the step of proceeding to the blind handover.
The method according to claim 6,
In the blind handover step,
The target femtocell determines whether the call is an outgoing call or an incoming call based on the call type information, and when the call is a preset call type when the call setup is completed, waits a preset time and then performs the blind handover. The femtocell handover method, characterized in that to proceed.
A plurality of femtocell base stations including a serving femtocell base station and a target femtocell base station; And
Forming a femtozone located in the macro cell including an access gateway for connecting the plurality of femtocell base station to the core network,
When the serving femtocell base station determines that the target side to proceed with the handover is one of the plurality of femtocells, the serving femtocell base station sets its own cell identifier (Cell ID) and a preset handover in a relocation required message transmitted to the access gateway. Record the information and proceed with the handover,
The target femtocell base station receives a relocation request message including the cell identifier and handover information from the access gateway, and when the serving side identified through the cell identifier is one of the plurality of femtocells, the hand Storing the cell identifier and the handover information while completing the over,
If the target femtocell base station determines that the target side of the new handover is the serving femtocell base station, even if a new handover event occurs for the handovered call before the reference time elapses after the completion of the handover. Femtocell system, characterized in that to ignore the over event.
9. The method of claim 8,
And the target femtocell base station determines the serving side as one of the plurality of femtocells when a radio network controller identifier (RNC ID) included in the cell identifier is the same as its radio network controller identifier.
delete 9. The method of claim 8,
The cell identifier and the handover information are recorded in a 'Last known UE Position' parameter in a relocation request or relocation request message.
The method of claim 11,
The cell identifier is recorded in a 'Cell ID' item of the 'Last known UE Position' parameter.
The handover related information may include call type information recorded in a 'SFN (System Frame Number)' item of the 'Last known UE Position' parameter, and NAS (Non Access Spectrum) Signal Information recorded in a 'Position Information' item. Femtocell system characterized by.
The method of claim 12,
If the target femtocell base station determines that the handovered call is a blind handover to the macro base station, whether the call is handed over during call setup or handover after call setup is completed based on the NAS signal information. Femtocell system, characterized in that the blind handover proceeds when the call setup is completed.
The method of claim 13,
If it is determined that the call is a preset call type based on the call type information, the target femtocell base station further waits for a preset time when the call setup is completed, and then proceeds with the blind handover. Femtocell System.

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