WO2007105625A1

WO2007105625A1 - Base station and handover control method

Info

Publication number: WO2007105625A1
Application number: PCT/JP2007/054647
Authority: WO
Inventors: Masayuki Motegi; Yasuhiro Kato; Wuri Andarmawanti Hapsari; Takehiro Nakamura
Original assignee: Ntt Docomo, Inc.
Priority date: 2006-03-10
Filing date: 2007-03-09
Publication date: 2007-09-20
Also published as: JP4932826B2; TW200803562A; JPWO2007105625A1

Abstract

A base station is provided with a transmission destination determining means for selecting a base station of a plurality of transfer destinations to which user data to be transmitted to a mobile station is transferred; and a data transfer means for transferring the user data to the base station of the transfer destination determined by the transfer destination determining means. The data transfer means transfers the user data to the base stations of the transfer destinations at the same time.

Description

Specification

Base station and handover control method

Technical field

TECHNICAL FIELD [0001] The present invention relates to a handover control technique for transferring user data when a mobile station performs a handover, and more particularly to a base station and a handover control method for transferring user data in a point-to-multipoint manner.

Background art

[0002] In a system to which IMT-2000 (International Mobile Telecommunication—2000) is applied, a mobile station (UE: User Equipment) moves and is connected to the same service GPRS Support Node (SGSN). When a handover is performed across two radio network controllers (RNCs), a procedure called “SRNS Relocation” is activated.

[0003] In the "SRNS Relocation" procedure, a packet data convergence protocol protocol (PDCP) terminated between the UE and the RNC, and a higher layer (RRC) between the UE and the RNC. : The sequence number is exchanged via Radio Resource Control, and the protocol status is adjusted so that there is no duplicate transmission / reception at the destination. It also includes the ability to transfer PDCP PDUs from the source RNC to the target RNC.

Disclosure of the invention

Problems to be solved by the invention

However, the above-described background art has the following problems.

[0005] In a system to which IMT-2000 is applied, handover across RNCs is rarely caused by force, so user data should be transferred only to the target RNC. In ordinary Hanndover, such as Inter-NodeB, loss and duplication are avoided by radio layer 2 protocol (RLC: Radio Link Control), and data transfer is not performed like Relocation. [0006] However, '—UTRAN', which started discussion as an enhancement technology for systems to which IMT-2000 is applied, lists requirements for moving speed, and these requirements include 120kmZh-350kmZh (frequency band). In addition, the wireless layer 2 protocol power is likely to be terminated between the mobile station and the base station in terms of architecture. In order to be lossless, data transfer is essential.

[0007] In such a high-speed environment, for example, 350kmZh on the Shinkansen, data communication such as E

-mail, when the UE is performing handover, even if data is transferred from the source base station to the target base station, it is possible to hand over to the next base station before completing the transfer of all user data High-performance data that could not be transferred could result in data loss and problems such as lower throughput of the upper layer (TCP: transmission control protocol).

Therefore, the present invention has been made in view of the above-described problems, and it is an object of the present invention to provide a base station and a node over control method that can provide lossless handover even during high-speed movement. .

Means for solving the problem

[0009] In order to solve the above problems, a base station of the present invention includes:

Transfer destination determining means for selecting a plurality of transfer destination base stations for transferring user data to be transmitted to the mobile station;

Data transfer means for transferring the user data to the transfer destination base station determined by the transfer destination determination means;

With

The data transfer means transfers the user data to the transfer destination base station at the same time.

With this configuration, data loss can be prevented even when a handover is performed before data transfer is completed.

[0011] The handover control method of the present invention includes:

Transfer that selects a plurality of transfer destination base stations to which user data to be transmitted to the mobile station is transferred. A destination determination step;

A data transfer step of simultaneously transferring the user data to the transfer destination base station determined by the transfer destination determination step;

One of the features is to have

[0012] By doing so, data loss can be prevented even when a handover is performed before data transfer is completed.

The invention's effect

[0013] According to the embodiment of the present invention, it is possible to realize a base station and a node / over-over control method that can provide lossless handover even during high-speed movement.

Brief Description of Drawings

FIG. 1 is an explanatory diagram showing a radio access network according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a base station according to an embodiment of the present invention.

FIG. 3 is a flowchart showing the operation of the radio access network according to one embodiment of the present invention.

FIG. 4 is a flowchart showing the operation of the source base station according to one embodiment of the present invention.

FIG. 5 is a flowchart showing the operation of the target base station according to one embodiment of the present invention.

FIG. 6 is a flowchart showing the operation of the radio access network according to one embodiment of the present invention.

FIG. 7 is a flowchart showing the operation of the source base station according to one embodiment of the present invention.

FIG. 8 is a flowchart showing the operation of the radio access network according to one embodiment of the present invention.

FIG. 9 is a flowchart showing the operation of the source base station according to one embodiment of the present invention.

FIG. 10 is a flowchart showing the operation of the target base station according to one embodiment of the present invention.

FIG. 11 is a flowchart showing the operation of the radio access network according to one embodiment of the present invention.

FIG. 12 is a flowchart showing the operation of the source base station according to one embodiment of the present invention. Explanation of symbols

[0015] 100 wireless access network 200 core network

300, 300, 300, 300 Access gateway (aGW)

one two Three

400, 400, 400, 400 base station (eNB: eNode B)

one two Three

500 Mobile Station (UE: User Equipment)

BEST MODE FOR CARRYING OUT THE INVENTION

Next, embodiments of the present invention will be described with reference to the drawings.

In all the drawings for explaining the embodiments, the same reference numerals are used for those having the same function, and repeated explanation is omitted.

A radio access network according to an embodiment of the present invention will be described with reference to FIG.

[0018] In the present embodiment, as an example, the case of applying to E-UTRA (E voluved- UMT¾ Terrestrial Radio Access) ana E- UTRAN (Evoluve d-UMTS Terrestrial Radio Access Network), which is being standardized by 3GPP explain.

[0019] A radio access network (E—UTRAN) 100, which is useful in this embodiment, is an access gateway (aGW: 300) that functions as a gateway between the core network 200 and the core network 200 and the radio access network. 300, 300, 300

1 2

) And multiple base stations (eNode B) 400 (4

Three

00, 400, 400) and 500 mobile stations (UE).

one two Three

[0020] The core network 200 includes an IP backbone 250, for example.

[0021] The access gateway 300 aims to dramatically reduce connection time and latency, and aims to reduce gateway latency in IMT-2000. Gateway GPRS Support Node (GGSN), SGSN (Service GPRS Support No de) , And a node that integrates at least some of the functions of RNC. Therefore, the access gateway 300 is a node having both the function of the core network 200 and the function of the radio access network 100.

[0022] Base station 400 aims to dramatically reduce connection time and latency !, I

MT—A node that integrates at least some of the functions of RNC and NodeB in 2000 It is. Here, eNodeB implements MAC (Media Access Control) protocol, RLC (Radio Link Control) protocol, etc. as U-plane functions, and RRC (Radio Resource Control) protocol as C-plane functions. The

Here, as an example of the radio access network, 1S described for E-UTRAN may be another system architecture configuration that is not limited to this.

[0024] When the mobile station 500 performs handover, the user data buffered by the Outer ARQ function unit of the source NB, for example, an outer ARQ service data unit (O uter ARQ SDU (Service Data Unit)), that is, untransmitted data And undelivered data are implemented in the functional capability NB that can be forwarded to the target NB. At the same time, a transmission path for data forwarding is set.

Next, the base station 400 that is useful in the present embodiment will be described with reference to FIG.

[0026] The base station 400, which is useful in the present embodiment, includes a control unit 402, a data storage unit 404, a data transfer unit 406, a wired transmission unit 408, and a movement speed measurement as movement information collection means connected to the control unit 402. Unit 410, data transfer destination determination unit 412 as a transfer destination determination unit, and wireless transmission unit 414.

[0027] The control unit 402 controls each functional entity included in Node B, and

B Control overall operation. Detailed functions will be described later.

[0028] The wired transmission unit 408 receives the user data transferred from the access gateway 300, and transfers the user data to the data storage unit 404. Also, the wired transmission unit 408 exchanges control signals for handover via an interface between base stations. Also, the wired transmission unit 408 transfers user data stored in the data storage unit 404 to a plurality of transfer destinations via an interface between base stations.

[0029] Radio transmission section 414 obtains a measurement report (communication quality report) reported from the mobile station.

[0030] Data storage section 404 stores user data to be transmitted to the user transmitted from access gateway 300.

[0031] The data transfer unit 406 determines the data transfer destination when the handover procedure is started. The user data stored in the data storage unit 404 is transferred to the transfer destination base station determined by the fixed unit 412.

[0032] The data transfer destination determination unit 412 determines a transfer destination to which user data stored in the data storage unit 404 is transferred at the time of handover. For example, the data transfer destination determination unit ₄₁ 2 is arranged in the base station with the best communication quality among the base stations that can secure resources based on the measurement report reported for the mobile station power and around the base station. The base stations are grooved (grouped) to be the transfer destination base station. That is, the data transfer destination determination unit 412 always includes the base station (cell) having the best communication quality V, the base station (cell), and the resources that can be secured based on the measurement report reported from the mobile station, Group base stations around these base stations.

[0033] Also, the data transfer destination determination unit 412 estimates the moving direction of the mobile station from the past history of the mobile station in the base station, and groups and selects base stations in the moving direction. May be. Alternatively, in an environment where the direction of movement is limited to some extent, such as a train or a car on a highway, the base station in the direction of movement may be grooved. For example, in the case of a train, the mobile station may notify the NW that it is on the train. (At that time, in order to make the mobile station recognize that it is on the train, it may be notified by the broadcast information.) As a result, the data transfer destination determination unit 412 estimates the moving direction of the mobile station and moves the moving direction. Group and select base stations in

[0034] The grouping method assumed in the present embodiment may be grouped based on other norms that are not limited to these! /.

[0035] Further, the data transfer destination determination unit 412 performs the grouping of the number of base stations that transfer user data, that is, grouping, based on at least one of the transfer capability of user data and the transfer capability of the connected transmission path. Determine the number of base stations. For example, the data transfer destination determination unit 412 determines the number of base stations that transfer user data based on at least one of the CPU load, the amount of stored data, and the transmission path bandwidth.

[0036] The movement speed measurement unit 410 acquires the movement speed of another base station power mobile station via a wire, or estimates information related to movement of the mobile station such as the movement speed of the mobile station via radio. . The estimation of the moving speed is based on the frequency at which the mobile station hands over the base station, the Doppler Frequency (fd) force It can be configured to estimate! Other estimation methods other than this estimation method may be used. Further, the moving speed measuring unit 410 notifies the data transfer destination determining unit 412 of information relating to the movement of the mobile station, for example, information indicating the moving speed. In this case, the data transfer destination determining unit 412 determines whether or not the moving speed exceeds a threshold value preliminarily defined by the system, based on the moving speed notified by the moving speed measuring unit 410. If the moving speed does not exceed the threshold, the data transfer destination determination unit 412 determines the base station to transfer data as the handover destination base station.

[0037] Next, a handover sequence in the radio access network 100 according to the present embodiment will be described with reference to FIG.

In the present embodiment, a case where the mobile station 500 is handed over to the source base station 400 and the target base station 400 connected under the access gateway 300 will be described.

1 2

To do.

[0039] The mobile station 500 stores information indicating communication quality of a base station that is a candidate for a handover destination with respect to the source base station 400 so that the source base station 400 can select an appropriate handover destination base station. Report the measurement report (Step S302).

[0040] Based on the measurement report from the mobile station 500, the source base station 400 selects an appropriate target base station for checking the availability of resources (HO decision) (step S304). For example, base station 400 is selected as the target base station.

2

[0041] Next, the source base station 400 transfers context, for example, C plane related information to the base station 400 (HO request) (step S306).

2

[0042] Next, base station 400 includes source base station 400 Q included in the transferred context.

twenty one

Resources are allocated based on oS information (Resource allocation). Further, the target base station 400 reserves the allocated resource (step S308).

2

[0043] Next, the base station 400, when the necessary resource reservation is successful,

2

Context transfer response indicating that preparation for handover is complete (

HO response) is notified (step S310).

[0044] Here, the base station 400, when the necessary resources cannot be secured, 0 is notified that resources for the mobile station 500 cannot be secured.

[0045] Upon receiving the context transfer response, the source base station 400 ^ measures or estimates the moving speed of the mobile station 500 to be handed over, and if it is faster than the moving speed specified in advance by the system, that is, it is determined in advance. If the threshold is greater than or equal to the threshold value, the destination base station is dulled. The source base station 400 always includes the target base station selected as the handover destination as a grouping candidate, and in addition, at least the user data transfer capability of the base station and the transfer capability of the transmission path to which the base station is connected are included. Based on one, select multiple candidates from mobile station measurement report (User mobility a nalysis) ₀

[0046] Also, the source base station 400 makes the base station 400 a handover destination base station, that is,

1 2

It determines as a get base station (forwarding NBs decision) (step S312).

[0047] On the other hand, the source base station 400 can secure resources for the base station 400 and the mobile station 500.

1 2

If there is no notification, the mobile station 500 selects another appropriate target base station to check the resource availability based on the measurement report from the mobile station 500. That is, the same operation as in step S304 is performed.

[0048] Next, the source base station 400 includes a plurality of grouped groups including the target base station 400.

1 2

User data that should be transferred to the mobile station 500 to the base station group of the mobile station 500, and the user data and the access gateway 300 power that should have been received from the mobile station 500 are still received and transmitted to the mobile station 500 Then, transfer of user data is started (Start user data forwarding) (Step S314, Step S316, Step S318).

[0049] The source base station 400 re-establishes a radio link with the target base station 400 with respect to the mobile station 500.

1 2

The cell specific information necessary for setting, that is, cell-specific information is notified (HO Command) (step S320).

[0050] Next, the mobile station 500 also receives the synchronization channel from the target base station 400,

2

Establish radio synchronization with base station 400 and set radio channel (L1ZL2 HO Rx S

2

CH from tNB) (step S322).

[0051] After setting the radio channel with the target base station 400, the mobile station 500

2

Notify station 400 that handover is complete (HO complete) (step S324).

[0052] Next, the target base station 400 has completed handover to the source base station 400.

twenty one

A handover confirmation completion notification (HO confirm) is sent (step S326). Step S326 wants to be, but may or may not be!

[0053] Next, the target base station 400 sends a path update request (Pa

twenty one

th switch) (step S328). The access gateway 300 updates the path of the destination to the source base station 400 and the target base station 400.

1 2

[0054] Source base station 400 discards the data stored in data storage section 404 (step S330).

[0055] Next, access gateway 300 releases, that is, releases signaling between base station access gateways to source base station 400 (step S332).

[0056] Next, the operation of the base station 400 in the radio access network 100 according to the present embodiment will be described.

In the present embodiment, the operation will be described separately for a source base station and a target base station.

[0058] The operation of the source base station will be described with reference to FIG.

[0059] The source base station 400 determines whether or not the control unit 402 has received the measurement report from the mobile station 500 (step S402).

If control unit 402 receives the measurement report from mobile station 500 and determines that it is not (step S402: NO), it ends the process.

[0061] When the control unit 402 determines that the measurement report has been received from the mobile station 500 (step S402: YES), the control unit 402 determines the mobile station 500 power of the surrounding base station (cell) stored in the reported measurement report. Based on the information indicating the communication quality, the base station is selected as the candidate for the handover destination base station, and the mobile station context is transferred to the base station selected as the handover destination candidate. Then, resource reservation for the handover destination candidate base station is performed (step S404).

Next, control section 402 determines whether or not a resource reservation completion response, eg, a context transfer response, has been received from the base station selected as a handover destination candidate (step S40). 6).

[0063] If a resource reservation completion response is received (NO in step S406), the process returns to step S404.

[0064] On the other hand, when a resource reservation confirmation response is received (step S406: YES), the moving speed measurement unit 410 acquires the moving speed of the mobile station 500 via radio. The data transfer destination determination unit 412 analyzes the moving speed, and sets a plurality of target base stations when the moving speed exceeds a predetermined moving speed, that is, when the moving speed exceeds a threshold predetermined by the system. , Grouping. The data transfer unit 406 starts data transfer of user data to the target base station set by the data transfer destination determination unit 412 (step S408). Here, the moving speed measuring unit 410 may acquire the moving speed of the mobile station 500 via a wire.

After starting the transfer of user data to the target base station group, control unit 402 transmits a radio channel switching request to mobile station 500. For example, the control unit 402 sets the cell specific necessary for resetting the radio channel with the target base station 400 for the mobile station 500.

2

Information, that is, cell-specific information is notified (step S410).

Next, control section 402 determines whether or not a handover completion confirmation response has been received from the target base station (step S412).

[0067] If a handover completion confirmation response has not been received (step S412: NO), step

Return to S410.

[0068] On the other hand, when the handover completion confirmation response is received (step S412: YES), the user data stored in the local domain is discarded (step S414).

Next, control unit 402 determines whether or not a path release notification has been received from access gateway 300 (step S416).

[0070] If the path release notification has not been received (step S416: NO), the process returns to step S414.

[0071] On the other hand, when the path release notification is received (step S416: YES), the processing ends normally.

[0072] The operation of the target base station will be described with reference to FIG. [0073] The target base station determines whether or not the control unit 402 has received a resource securing request from the source base station 400 (step S502).

[0074] If the resource securing request has not been received (step S502: NO), the processing ends.

[0075] On the other hand, when the source base station 400 also receives the resource securing request (step S502: YES), the target base station performs resource reservation based on the QoS information in the context included in the resource securing request, A resource reservation completion response, for example, a context transfer response is transmitted to the source base station 400 to notify that resource reservation has been completed (step S504).

Next, control section 402 determines whether or not a radio channel switching completion notification, eg, HO composite, is received from mobile station 500 (step S506).

[0077] If a wireless channel switching completion notification is received from the mobile station 500! /, !! / (step S506: NO), the processing is terminated.

On the other hand, when a radio channel switching completion notification is received from mobile station 500 (step S506: YES), control unit 402 sends a path switching request, for example, a path update request (Path switch) to access gateway 300. Send. In addition, the control unit 402 transmits a handover confirmation completion notification to the source base station 400 (step S508). Next, the process ends normally.

[0079] Next, a radio access network according to another embodiment of the present invention will be described.

[0080] The configuration of the radio access network according to the present embodiment is the same as that of the radio access network described with reference to FIG.

[0081] The configuration of the base station according to the present embodiment is the same as that of the base station described with reference to FIG.

[0082] Next, a handover sequence in the radio access network 100 according to the present embodiment will be described with reference to FIG.

In this embodiment, the case where the mobile station 500 is handed over to the source base station 400 and the target base station 400 connected under the access gateway 300 will be described.

1 2

To do. [0084] The mobile station 500 stores information indicating the communication quality of the base station that is a candidate for the handover destination with respect to the source base station 400 so that the source base station 400 can select an appropriate handover destination base station. Report the measurement report (step S602).

[0085] Next, the source base station 400 measures or estimates the moving speed of the mobile station 500 that is scheduled to be handed over. If the moving speed is higher than the moving speed specified in advance by the system, that is, above a predetermined threshold value. In some cases, base stations that are candidates for handover are grouped. The source base station 400 has, as grouping candidates, a plurality of base stations that are candidate handover destinations based on at least one of the user data transfer capability of the base station and the transfer capability of the transmission path to which the base station is connected. Based on the measurement report of the mobile station (User mobility analysis & HO decision) (Step S604) o For example, base stations 400 to 400 are selected as base stations that are candidates for the handover destination.

2 m.

[0086] Next, the source base station 400 transfers context, for example, C-plane related information to the base stations 400 to 400 that are candidates for the handover destination (HO request) (step S60).

2 m

6, Step S608). For example, the source base station 400 transfers the context by multicast to the base stations 400 to 400 that are candidates for the handover destination.

2 m

[0087] Next, base stations 400 to 400 that are candidate handover destinations are transferred from the source base station 400.

2 m 1 Resources are allocated based on the QoS information contained in the transferred context (Resource allocation). In addition, 400 to 400 that are candidates for the handover destination are assigned.

2 m

Resource reservation is performed (step S610, step S612).

[0088] Next, the base stations 400 to 400, when the necessary resource reservation is successful,

2 m

The base station 400 is notified of a context transfer response indicating that preparation for handover has been completed (HO response) (steps S614 and S616).

[0089] Here, the base stations 400 to 400, when necessary resources cannot be secured,

2 m

Notifies the base station 400 that resources for the mobile station 500 cannot be secured.

[0090] The source base station 400 cannot secure resources for the base station 400 mobile station 500.

1 2

Is notified, based on the measurement report from the mobile station 500, a base station that is another suitable handover destination candidate for checking the availability of resources is selected. That is, the same operation as step S604 is performed.

[0091] Next, the source base station 400 includes a plurality of grouped base stations including the target base station 400.

1 2

User data that should be transferred to the mobile station 500 to the base station group of the mobile station 500, and the user data and the access gateway 300 power that should have been received from the mobile station 500 are still received and transmitted to the mobile station 500 Then, transfer of user data is started (Start user data forwarding) (Step S618, Step S620, Step S622). For example, the source base station 400 is a grouped group including the target base station 400.

1 2

The user data is transferred to the base station group by multicast.

[0092] The source base station 400 re-establishes a radio link with the target base station 400 with respect to the mobile station 500.

1 2

The cell specific information necessary for setting, that is, cell-specific information is notified (HO Command) (step S624).

[0093] Next, the mobile station 500 also receives the synchronization channel from the target base station 400,

2

CH from tNB) (step S626).

[0094] After setting the radio channel with the target base station 400, the mobile station 500

2

Notify station 400 that handover is complete (HO complete) (step

2

S628).

[0095] Next, the target base station 400 has completed handover to the source base station 400.

twenty one

A handover confirmation completion notification (HO confirm) is sent (step S630).

[0096] Next, the target base station 400 sends a path update request (Pa

twenty one

th switch) (step S632). The access gateway 300 updates the path of the destination to the source base station 400 and the target base station 400.

1 2

[0097] The source base station 400 discards the data stored in the data storage unit 404 (step S634).

[0098] Next, the access gateway 300 releases, that is, releases the signaling between the base station access gateways to the source base station 400 (step S636).

[0099] Next, the operation of the base station 400 in the radio access network 100 that is relevant to the present embodiment will be described. In this embodiment, the operation of the target base station is the same as the operation described with reference to FIG. 5, and therefore the operation of the source base station will be described with reference to FIG.

[0101] The source base station 400 determines whether or not the control unit 402 has received the measurement report from the mobile station 500 (step S702).

[0102] When a measurement report is received from mobile station 500 and it is determined that it is correct (step S70)

2: NO), the process ends.

[0103] If it is determined that a measurement report has been received from mobile station 500 (step S702: YES)

) The moving speed measuring unit 410 acquires the moving speed of the mobile station 500 via wireless (step S704). Further, the moving speed measuring unit 410 may acquire the moving speed of the mobile station 500 via a wire.

The data transfer destination determination unit 412 analyzes the moving speed and determines whether or not the moving speed exceeds a predetermined moving speed, that is, whether or not the power is greater than or equal to a threshold predetermined by the system (step S 706)

When the moving speed is equal to or higher than the threshold value determined in advance by the system (Step S706: YES)

The data transfer destination determination unit 412 sets multiple target base stations and performs grouping based on information indicating the communication quality of the neighboring base stations (cells) stored in the measurement report reported from the mobile station 500. (Step S708).

[0105] On the other hand, if the moving speed is not equal to or higher than a threshold value determined in advance by the system (step S706).

: NO), the data transfer destination determination unit 412 sets the target base station based on the information indicating the communication quality of the neighboring base station (cell) stored in the measurement report reported from the mobile station 500 (step S710). ).

Next, the control unit 420 transfers the mobile station context to the base station selected as a candidate for the handover destination, for example, via the wired transmission unit 408, and performs resource reservation for the handover destination candidate base station. (Step S712).

Next, control section 402 determines whether or not a resource reservation completion response has been received from the base station selected as a handover destination candidate (step S714).

[0108] If the resource reservation completion response has not been received (step S714: NO), the process returns to step S712. On the other hand, when a resource reservation confirmation response is received (step S714: YES), the data transfer unit 406 starts data transfer of user data to the target base station set by the data transfer destination determination unit 412 ( Step S716).

[0110] After transfer of user data to the target base station group is started, control unit 402 transmits a radio channel switching request to mobile station 500 (step S718).

Next, control section 402 determines whether or not a handover completion confirmation response has been received from the target base station (step S720).

[0112] If the handover completion confirmation response has not been received (step S720: NO), step

Return to S718.

On the other hand, when the handover completion confirmation response is received (step S 720: YES), the user data stored in the low level is discarded (step S 722).

Next, control unit 402 determines whether or not it has received a path release notification from access gateway 300 (step S724).

[0115] If the path release notification has not been received (step S724: NO), the process returns to step S722.

[0116] On the other hand, when the path release notification is received (step S724: YES), the processing ends normally.

A radio access network according to another embodiment of the present invention will be described.

[0118] The configuration of the radio access network according to the present embodiment is the same as the configuration described with reference to FIG.

[0119] Base station 400 is a node that integrates at least some of the functions of RNC and NodeB in IMT-2000 with the aim of dramatically reducing connection time and latency. Here, eNodeB implements MAC (Media Access Control) protocol, RLC (Radio Link Control) protocol, PDCP (Packet Data Convergence Protocol), etc. as U plane functions, and RRC (Radio) as C plane functions. Resource Control) protocol, SI—AP (SI-Application Part), X2—AP (X2-Application Part) are implemented.

[0120] When mobile station 500 is handed over, buffering is performed in PDCP function section of source NB. A function is provided in the NB that allows the user data, for example, service data unit (SDU), that is, untransmitted data and unacknowledged data to be forwarded to the target NB. At the same time, a transmission path for data forwarding is set. This transmission path may be wireless or wired.

[0121] The configuration of the base station 400 that is relevant to the present embodiment is the same as the configuration described with reference to FIG.

The control unit 402 recognizes the information indicating the completion of the node over transmitted from the mobile station 500, and based on the information, makes a request for changing the transfer route to the access gateway 300. A handover completion notification is sent to notify completion. In addition, the control unit 402 notifies the handover source base station that the handover is completed by a resource release message.

[0123] Next, a handover sequence in the radio access network 100 that is relevant to the present embodiment will be described with reference to FIG.

In this embodiment, the case where mobile station 500 is handed over to source base station 400 target base station 400 connected to access gateway 300 is described.

1 2

To do.

[0125] The mobile station 500 stores information indicating the communication quality of a base station that is a handover destination candidate for the source base station 400 so that the source base station 400 can select an appropriate handover destination base station. Report the measurement report (Step S802).

[0126] Based on the measurement report from mobile station 500, source base station 400 selects an appropriate target base station that confirms the availability of resources (HO decision) (step S804). For example, base station 400 is selected as the target base station.

2

[0127] Next, the source base station 400 transfers context, for example, C plane related information to the base station 400 (HO request) (step S806).

2

[0128] Next, the base station 400 transmits the Q included in the transferred context to the source base station 400.

twenty one

Allocate resources based on oS information (Admission Control). Further, the target base station 400 reserves the allocated resource (step S808).

2

[0129] Next, when the necessary resource reservation is successful, the base station 400 HO request Ack indicating that the preparation for handover is complete, including cell-specific information necessary to reconfigure the radio link, ie cell-specific information. Is notified (step S810).

[0130] Here, the base station 400 determines that if the necessary resources cannot be secured, the source base station 40

2

0 is notified that resources for the mobile station 500 cannot be secured.

[0131] Upon receiving the handono request acknowledgment, the source base station 400 measures or estimates the moving speed of the mobile station 500 to be handed over, and if it is faster than the moving speed specified in advance by the system, that is, it is determined in advance. If it is above the threshold, group the destination base stations. The source base station 400 always includes the target base station selected as the handover destination as a grouping candidate, and in addition to that, the user data transfer capability of the base station and the transfer capability of the transmission path to which the base station is connected Based on at least one of them, a plurality of candidates are selected from the measurement report of the mobile station (User mobility analysis) o The source base station 400 selects the base station 400 as the handover destination base station.

1 2

That is, it determines as a target base station (forwarding NBs decision) (step S812).

[0132] On the other hand, the source base station 400 can secure resources for the base station 400 mobile station 500.

1 2

If there is no notification, the mobile station 500 selects another appropriate target base station to check the resource availability based on the measurement report from the mobile station 500. That is, the same operation as in step S804 is performed.

[0133] Next, the source base station 400 includes a plurality of grouped base stations including the target base station 400.

1 2

User data that should be transferred to the mobile station 500 to the base station group of the mobile station 500, and the user data and the access gateway 300 power that should have been received from the mobile station 500 are still received and transmitted to the mobile station 500 Then, transfer of user data is started (Start user data forwarding) (Step S814, Step S816, Step S818).

[0134] The source base station 400 re-establishes a radio link with the target base station 400 for the mobile station 500.

1 2

Cell specific information necessary for setting, that is, cell-specific information is notified (HO Command) (step S820).

[0135] Next, the mobile station 500 receives the target base station 400 power synchronization channel, and Establish radio synchronization with base station 400 and set radio channel (L1ZL2 HO Rx S

2

CH from tNB) (Step S822).

[0136] After setting the radio channel with the target base station 400, the mobile station 500

2

Notify station 400 that handover is complete (HO complete) (step

2

S824).

[0137] Next, the target base station 400 accesses the access game set in the source base station 400.

twenty one

To change the 300-way path of Toei 300 to the target base station 400,

1 2

A handover completion notification (Handover Complete) for notifying completion is transmitted to the access gateway 300 (step S826).

[0138] Receiving the handover completion notification, the access gateway 300 receives the handover completion acknowledgment (Hando) to notify the target base station 400 of the completion of the path switch.

2

ver Complete ACK) is notified (step S828).

The target base station 400 that has received the handover completion acknowledgment is the source base station 40

2

A resource release message is transmitted to 0 (step S830).

[0140] The source base station 400 that has received the resource release message discards the duplicated context (Delete context) (step S832).

[0141] Next, the operation of the base station 400 in the radio access network 100 that is relevant to the present embodiment will be described with reference to FIG.

[0142] In the present embodiment, the operation will be described separately for the source base station and the target base station.

[0143] The operation of the source base station is different from that of step S412 in the operation of the source base station described with reference to FIG. In step S412, it is confirmed whether the target base station 400 also receives the resource release message (step S912).

2

. If the target base station 400 also receives a resource release message (step S912:

2

YES), the control unit 402 discards the replicated context and user data (step S914) and ends.

[0144] The operation of the target base station will be described with reference to FIG.

[0145] Regarding the operation of the target base station, the operation of the source base station described with reference to FIG. However, the processing after step S508 is different. In step S508, when it is determined that a channel setting completion notification, for example, HO complete is received from the mobile station 500 (step S506: YES), the control unit 402 transmits a handover completion notification to the access gateway 300 ( Step S 1008).

Next, control unit 402 determines whether or not a handover completion acknowledgment (HO Complete Ack) has been received from access gateway 300 (step S 1010). When receiving a handover completion acknowledgment (HO Complete Ack) from the access gateway 300 (step S1010), the control unit 402 transmits a resource release message to the source base station (step S1012).

[0147] Next, a handover sequence in the radio access network 100 that is relevant to the present embodiment will be described with reference to FIG.

In this embodiment, the case where the mobile station 500 is handed over to the source base station 400 and the target base station 400 connected under the access gateway 300 is described.

1 2

To do.

[0149] The mobile station 500 stores information indicating the communication quality of a base station that is a handover destination candidate for the source base station 400 so that the source base station 400 can select an appropriate handover destination base station. Report the measurement report (step S1102).

[0150] Next, the source base station 400 measures or estimates the moving speed of the mobile station 500 that is scheduled to be handed over. If the moving speed is higher than the moving speed specified in advance by the system, that is, above a predetermined threshold value. In some cases, base stations that are candidates for handover are grouped. The source base station 400 has, as grouping candidates, a plurality of base stations that are candidate handover destinations based on at least one of the user data transfer capability of the base station and the transfer capability of the transmission path to which the base station is connected. Is selected based on the measurement report of the mobile station (User mobility analysis & HO decision) (step SI 104). For example, base station 400 as a base station that is a candidate for the handover destination.

2 to 400 are selected.

[0151] Next, the source base station 400 transfers the context, for example, C-plane related information, to the base stations 400 to 400 that are candidates for the handover destination (HO request) (step S 11 06, step SI 108). For example, the source base station 400 transfers the context to the base stations 400 to 400 that are candidates for the handover destination by multicast.

2 m

[0152] Next, base stations 400 to 400 that are candidates for the handover destination are transmitted from the source base station 400.

2 m 1 Allocates resources based on the QoS information contained in the transferred context (Admission control). In addition, the 400 to 400 candidates for the handover destination are assigned to the assigned resources.

2 m

The source is reserved (step S1110, step S1112).

[0153] Next, the base stations 400 to 400, when the necessary resource reservation is successful,

2 m

The base station 400 is notified of a node over request acknowledge that the preparation for handover has been completed (HO request Ack) (step S 1114, step S 1116).

[0154] Here, the base stations 400 to 400, when necessary resources cannot be secured,

2 m

[0155] The source base station 400 cannot secure resources for the base station 400 mobile station 500.

1 2

Is notified, based on the measurement report from the mobile station 500, a base station that is another suitable handover destination candidate for checking the availability of resources is selected. That is, the same operation as in step S1104 is performed.

[0156] Next, the source base station 400 includes a plurality of grouped base stations including the target base station 400.

1 2

User data that should be transferred to the mobile station 500 to the base station group of the mobile station 500, and the user data and the access gateway 300 power that should have been received from the mobile station 500 are still received and transmitted to the mobile station 500 Then, transfer of user data is started (Start user data forwarding) (Step SI 118, Step SI 120, Step SI 122). For example, the source base station 400 is a grouped complex that includes the target base station 400.

1 2

User data is transferred to a number of base stations by multicast.

[0157] The source base station 400 re-establishes a radio link with the target base station 400 for the mobile station 500.

1 2

The cell specific information necessary for setting, that is, cell-specific information is notified (HO Command) (step S 1124).

[0158] Next, the mobile station 500 receives the target base station 400 power synchronization channel, and

2

Establish radio synchronization with base station 400 and set radio channel (L1ZL2 HO Rx S CH from tNB) (Step SI 126).

[0159] After setting the radio channel with the target base station 400, the mobile station 500

2

Notify station 400 that handover is complete (HO complete) (step

2

S 1128).

[0160] Next, the target base station 400 accesses the access game set in the source base station 400.

twenty one

To change the 300-way path of Toei 300 to the target base station 400,

1 2

A handover complete notification (Handover Complete) for notifying completion is transmitted to the access gateway 300 (step S 1130).

[0161] Upon receiving the handover completion notification, the access gateway 300 receives the handover completion acknowledgment (Hando) to notify the target base station 400 of the completion of the path switch.

2

ver Complete ACK) is notified (step S I 132).

[0162] The target base station 400 that has received the handover completion acknowledgment is the source base station 40

2

A resource release message is transmitted to 0 (step S1134).

[0163] Upon receiving the resource release message, the source base station 400 discards the copied context (Delete context) (step S1136).

[0164] Next, the operation of the base station 400 in the radio access network 100 that is relevant to the present embodiment will be described with reference to FIG.

In this embodiment, the operation of the target base station is the same as the operation described with reference to FIG. 10, and therefore the operation of the source base station will be described.

[0166] Regarding the operation of the source base station, the processing after step S720 differs in the operation of the source base station described with reference to FIG. In step S720, the target base station 400 also confirms whether or not a resource release message has been received (step S1220).

2

o When the target base station 400 also receives the resource release message (step S 122

2

0: YES), the control unit 402 discards the replicated context and user data (step S 1222) and ends.

[0167] According to the embodiment of the present invention, it is possible to simultaneously determine a handover destination base station and a mobile station to which user data is transferred based on the moving speed of the mobile station.

[0168] As described above, according to the embodiment of the present invention, a group that is highly likely to be handed over. By grouping ground stations (cells) and forcing the user data to the grouped base stations at the time of handover, data cannot be sent and data is lost even in an environment where the mobile station moves at high speed. It is possible to prevent this from happening and to ensure efficient transfer and secure communication quality.

[0169] This international application claims priority based on Japanese Patent Application No. 2006-66280 filed on March 10, 2006. The entire contents of 2006-66280 are incorporated herein by reference. To do.

Industrial applicability

[0170] The base station and the node over control method that are useful in the present invention can be applied to a radio communication system.

Claims

The scope of the claims

[1] Destination determining means for selecting a plurality of transfer destination base stations for transferring user data to be transmitted to the mobile station;

With

The base station characterized in that the data transfer means simultaneously transfers the user data to the transfer destination base station.

[2] In the base station according to claim 1:

Movement information collection means for collecting information on movement of the mobile station;

With

The base station characterized in that the transfer destination determination means selects a plurality of transfer destination base stations to which user data to be transmitted to the mobile station is transferred based on the information on the movement.

[3] In the base station according to claim 1:

The base station according to claim 1, wherein the transfer destination determining means selects a transfer destination base station based on communication quality of another base station notified from the mobile station.

[4] In the base station according to claim 1:

The transfer destination determining means estimates a moving direction of the mobile station based on a passage history of the mobile station or a report from the mobile station, and selects a base station in the moving direction. .

[5] In the base station according to claim 1:

The transfer destination determining means determines the number of base stations that transfer user data based on at least one of a CPU load, a stored data amount, and a transmission path band.

[6] Destination determination step for selecting a plurality of transfer destination base stations that transfer user data to be transmitted to the mobile station;

A data transfer step of simultaneously transferring the user data to a transfer destination base station determined by the transfer destination determination step; A handover control method comprising:

[7] In the handover control method according to claim 6,

A movement information collecting step for collecting information on movement of the mobile station;

Have

The transfer destination determining step selects a plurality of transfer destination base stations to which user data to be transmitted to a mobile station is transferred based on the information on the movement.

[8] In the handover control method according to claim 6,

The handover control method characterized in that the transfer destination determining step selects a transfer destination base station based on the communication quality of another base station notified from the mobile station.

[9] In the base station according to claim 6:

The handover control method characterized in that the transfer destination determining step estimates a moving direction of the mobile station based on a passage history of the mobile station or a report from the mobile station, and selects a base station in the moving direction.

[10] In the handover control method according to claim 6,

The transfer destination determining step determines the number of base stations to which user data is transferred based on at least one of CPU load, stored data amount, and transmission path bandwidth. .