Patent Application
20090156212
The present invention relates to techniques for transferring data between base stations. In particular, the present invention relates to a data transfer method and a base station, which transfers the data between base stations when a mobile station performs a handover.
In an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) system of a next generation radio access network, which has been discussed in the third Generation Partnership Project (3GPP), it is assumed to apply a hard handover as a handover between base stations.
In the hard handover, a mobile station switches a radio link from a hard handover source base station to a hard handover target base station.
In such hard handover, a complexity of a system can be eliminated. Thus, the hard handover is particularly effective in the E-UTRAN system in which the handover between base stations is performed through an IP-based core network.
In such handover, however, the mobile station cannot receive, from the handover target base station, user data stored in a buffer for the mobile station in the handover source base station (for example, downlink user data yet to be sent to the mobile station, downlink user data being retransmitted, and the like).
Accordingly, in such hard handover, the hard handover source base station is required to transfer the user data, which is stored in the buffer for the mobile station, to the hard handover target base station.
For example, “Fast Handover for MIPv6 (FMIP)” is defined in RFC4068 of IETF (see, for example, Non-patent Document 1), as a method for transferring the user data in the hard handover.
However, when a plurality of the mobile stations perform a process of the hard handover, a large volume of the user data, which is transferred from the hard handover source base station to the hard handover target base station, is communicated on a transmission path, in addition to the user data between the base station and the plurality of the mobile stations. Thus, a congestion of the transmission path may occur.
In such a case, due to the congestion of the transmission path, the user data transferred from the hard handover source base station to the hard handover target base station could be lost.
The lost user data is retransmitted by a retransmission control between the base stations. However, retransmitting the lost user data takes longer time since the lost user data is retransmitted in an upper layer.
As a result, transmitting the user data from the hard handover source base station to the hard handover target base station takes longer time. Accordingly, a user throughput could largely deteriorate.
Non-patent Document 1: IETF RFC4068
In view of the above problem, the present invention has an object of providing a data transfer method and a base station, which can effectively transfer user data of the mobile station to a handover target base station without losing any data, when the mobile station performs a handover.
A first aspect of the present invention is summarized as a data transfer method which transfers user data of a mobile station from a handover source base station to a handover target base station through a transmission path, when the mobile station performs a handover, including: determining, at the handover source base station, a priority order of the user data; determining, at the handover source base station, a transfer speed of the user data based on the priority order; and transferring, at the handover source base station, the user data to the handover target base station based on the determined transfer speed.
In the first aspect of the present invention, in the determination of the transfer speed, the handover source base station may determine a transfer speed of user data having a high priority order to be higher, in comparison with a transfer speed of user data having a low priority order.
In the first aspect of the present invention, the data transfer method may further include: calculating, at the handover source base station, a user data speed between the handover source base station and the mobile station, based on communication quality information from the mobile station, and in the determination of the transfer speed, the handover source base station may determine the transfer speed based on the user data speed.
In the first aspect of the present invention, the data transfer method may further include: monitoring, at the handover source base station, a resource of the transmission path, and in the determination of the transfer speed, the handover source base station may determine the transfer speed based on the resource of the transmission path.
In the first aspect of the present invention, the data transfer method may further include: measuring, at the handover source base station, a moving speed of the mobile station, and in the determination of the transfer speed, the handover source base station may determine the transfer speed based on the measured moving speed of the mobile station.
A second aspect of the present invention is summarized as a base station which transfers user data of a mobile station to a handover target base station of the mobile station through a transmission path, including: a priority order determination unit configured to determine a priority order of the user data; a transfer speed determination unit configured to determine a transfer speed of the user data according to the determined priority order; and a transfer unit configured to transfer the user data to the handover target base station based on the determined transfer speed.
In the second aspect of the present invention, the transfer speed determination unit may be configured to determine a transfer speed of user data having a high priority order to be higher, in comparison with a transfer speed of user data having a low priority order.
In the second aspect of the present invention, the base station may further include: a calculation unit configured to calculate a user data speed between the base station and the mobile station, based on communication quality information from the mobile station, and the transfer speed determination unit may be configured to determine the transfer speed based on the user data speed.
In the second aspect of the present invention, the base station may further include: a monitoring unit configured to monitor a resource of the transmission path, and the transfer speed determination unit may be configured to determine the transfer speed based on the resource of the transmission path.
In the second aspect of the present invention, the base station may further include: a measuring unit configured to measure a moving speed of the mobile station, and the transfer speed determination unit may be configured to determine the transfer speed based on the measured moving speed of the mobile station.
By referring to
As shown in
In the following description, an example is described in which the mobile station 1 moves from a cell C1 side of the base station 2 to a cell C2 side of the base station 3, and the base station 2 is to be a handover source base station and the base station 3 is to be a handover target base station.
In the present description, “handover” refers to “hard handover”. In such a hard handover, when the mobile station 1 moves from the cell C1 to the cell C2, the mobile station 1 switches a radio link from the handover source base station 2 to the handover target base station 3. In such a hard handover, the mobile station 1 transmits and receives the user data constantly with only one base station.
A transmission path on which the user data can be transferred is provided between the handover source base station 2 and the handover target base station 3. Such a transmission path may be wired or wireless. In addition, the transmission path may be formed so that the access gateway 4, a router, a switch, and the like would be connected therewith.
As shown in
The outer ARQ function is a retransmission control function which compensates a loss of the user data, the loss which cannot compensated by the Hybrid Automatic Repeat reQuest (HARQ) retransmission control of the sub-layer of the layer 2.
Note that a buffer which is provided with a user data storage unit 22 (to be described later) of the handover source base station 2 may be a Service Data Unit (SDU) buffer in the Outer ARQ function.
Here, the SDU is referred to be a unit of the user data in the Outer ARQ function.
Furthermore, when the mobile station 1 performs the handover, the SDU stored in the SDU buffer may be transferred to the handover target base station 3 by the Lossless Relocation function of the handover source base station 2.
Note that such a configuration is applicable to all of the handover source base stations, and it should be noted that when the base station 3 is the handover source base station, the base station 3 may have a similar configuration.
The handover source base station 2 is provided with a wired transmission unit 21, a user data storage unit 22, a radio transmission unit 23, a user data priority order analyzing unit 24, a user data speed analyzing unit 25, a resource analyzing unit 26, a moving speed analyzing unit 27, a transfer speed determination unit 28, and a control unit 29.
Note that the base station 2 is described here as the configuration in which all of the user data priority order analyzing unit 24, the user data speed analyzing unit 25, the resource analyzing unit 26, and the moving speed analyzing unit 27 are provided. However, the base station 2 may take any configuration as long as it includes at least one of such components.
The wired transmission unit 21 is configured to transmit and receive the user data to and from the access gateway 4 or the handover target base station 3 through a network.
Specifically, the wired transmission unit 21 is configured to receive downlink user data through the access gateway 4, and to store the received data in the user data storage unit 22.
In addition, when the mobile state 1 performs the handover, the wired transmission unit 21 is configured to transfer the user data of the mobile station 1, which is stored in the buffer of the user data storage unit 22 (to be described later), to the handover target base station 3, based on a transfer speed determined by the transfer speed determination unit 28.
In addition, the wired transmission unit 21 may be configured to receive information for measuring a moving speed of the mobile station 1.
The user data storage unit 22 is provided with a buffer which stores the user data of the mobile station 1.
Specifically, the user data storage unit 22 is configured to store in the buffer, such as user data for which a transmission acknowledged from the mobile station has not received, user data which is being acknowledged, user data yet to be transmitted to the mobile station 1 after received from the access gateway 4, or the like.
Further, the user data storage unit 22 may be provided with a buffer for each of the mobile station 1, respectively, so as to store the user data in the buffer for each of the mobile station 1, respectively.
In addition, the user data storage unit 22 may be provided with a buffer for each of a priority identifier added to the user data such as a DiffServ, so as to store the user data for each of the priority identifier.
Furthermore, the user data storage unit 22 may be configured to delete, from the buffer, the user data which is acknowledged by the retransmission control between the base station 2 and the mobile station 1.
The radio transmission unit 23 is configured to transmit and receive the user data to and from the mobile station 1 through a radio network.
Specifically, the radio transmission unit 23 is configured to transmit the downlink user data stored in the user data storage unit 22, to the mobile station 1.
Moreover, the radio transmission unit 23 may be configured to periodically receive communication quality information from the mobile station 1.
Here, the communication quality information is referred to be, for example, Channel Quality Indicator (CQI) and the like.
Additionally, the radio transmission unit 23 may be configured to receive the information for measuring a moving speed of the mobile station 1.
The user data priority order analyzing unit 24 is configured to analyze a priority order of the user data, which is stored in the user data storage unit 22.
Here, the type of the user data is referred to as, for example, a type based on a content of the user data (conversation data, streaming data, interactive data, background data, and the like), a type based on a priority identifier added to the user data such as DiffServ, a type based on a direction (uplink or downlink) of the user data, a type based on a user (such as a user of the mobile station 1a, a user of the mobile station 1b, . . . ), and the like.
In addition, the user data priority order analyzing unit 24 is configured to notify, to the transfer speed determination unit 28, the priority order of the user data.
For example, when the user data priority order analyzing unit 24 analyzes the priority order of the user data based on the content of the user data, the user data priority order analyzing unit 24 may notify, to the transfer speed determination unit 28, the priority order; the conversation data>the streaming data>the interactive data>the background data.
Further, when the user data priority order analyzing unit 24 analyzes the priority order of the user data based on the priority identifier added to the user data such as DiffServ, the user data priority order analyzing unit 24 may analyze the priority identifier so as to notify, to the transfer speed determination unit 28, the priority order of the user data.
The user data speed analyzing unit 25 is configured to analyze a user data speed between the handover source base station 2 and the mobile station 1, based on the communication quality information from the mobile station 1, which is notified from the radio transmission unit.
Here, the user data speed is referred to as, for example, the transmission speed of the downlink user data, a size of the downlink user data, and the like.
In addition, the user data speed analyzing unit 25 is configured to notify, to the transfer speed determination unit 28, the analyzed user data speed of each of the mobile station 1.
The resource analyzing unit 26 is configured to analyze a resource of the transmission path.
Here, the resource of the transmission path is referred to as, for example, a volume of the user data transferred from the handover source base station 2 to the handover target base station 3 on the transmission path, a volume of uplink user data from the handover source base station 2, and the like.
In addition, the resource analyzing unit 26 is configured to notify, to the transfer speed determination unit 28, the resource of the transmission path, which is analyzed at the resource analyzing unit 26.
The moving speed analyzing unit 27 is configured to analyze the moving speed of each of the mobile station 1.
Specifically, the moving speed analyzing unit 27 analyzes the moving speed of each of the mobile station 1, based on the information for measuring the moving speed, which is notified from the wired transmission unit 21 and the radio transmission unit 23.
Here, the information for measuring the moving speed is referred to as, for example, the number of the handover per unit time of each of the mobile station 1, a handover history (such as a time) of each of the mobile station 1, the handover history recorded in each of the mobile station 1, a handover history (such as a time) of each of the mobile station, the handover history notified from an other base station through the network, a radio signal from each of the mobile station 1, and the like.
Furthermore, the moving speed analyzing unit 27 is configured to notify, to the transfer speed determination unit 28, the moving speed of each of the mobile station 1, which is analyzed at the moving speed analyzing unit 27.
The transfer speed determination unit 28 is configured to determine a transfer speed of the user data.
Specifically, transfer speed determination unit 28 is configured to determine the transfer speed of the user data, based on the priority order of the user data, which is notified from the user data priority order analyzing unit 24, the user data speed of each of the mobile station 1, which is notified from the user data speed analyzing unit 25, the resource of the transmission path, which is notified from the resource analyzing unit 26, or the moving speed of each of the mobile station 1, which is notified from the moving speed analyzing unit 27.
Specifically, when the transfer speed determination unit 28 determines the transfer speed of the user data based on the priority order of the user data, the transfer speed determination unit 28 is configured to determine a transfer speed of user data having a high priority order to be higher, in comparison with a transfer speed of user data having a low priority order.
Here, it is preferable that the transfer speed of the user data having the higher priority order is determined to be fast to an extent that the buffer which stores the transferred user data does not overflow in the handover target base station 3 (to the extent that the handover target base station 3 can process the transferred user data). The transfer speed determination unit 28 may estimate the transfer speed based on the CQI, for example. Alternatively, the transfer speed determination unit 28 may determine the transfer speed based on a storage state of the user data, by periodically receiving, from the handover target base station 3, a report of the storage state of the buffer. Further, the transfer speed determination unit 28 may also estimate the transfer speed based on the moving speed.
Furthermore, the transfer speed determination unit 28 may fixedly create a corresponding table and may determine the transfer speed of the user data in accordance with the corresponding table. For example, such corresponding table may include the high priority order and the low priority order as the priority order based on a priority of the user data, and the transfer speed for the high priority is determined to be 10 Mbps, and the transfer speed for the low priority is determined to be 2 Mbps.
Moreover, the transfer speed determination unit 28 may be configured to determine an upper limit of the transfer speed of the user data, based on the user data speed, which is notified from the user data speed analyzing unit 25.
For example, when a communication quality between the mobile station 1 and the handover source base station 2 is poor and the user data speed notified from the user data speed analyzing unit 25 is slow, the transfer speed determination unit 28 sets the upper limit of the transfer speed of the user data to be low. In contrast, when the communication quality between the mobile station 1 and the handover source base station 2 is good and the user data speed notified from the user data speed analyzing unit 25 is fast, the transfer speed determination unit 28 sets the upper limit of the transfer data of the user data to be high.
Further, the transfer speed determination unit 28 may be configured to determine the upper limit of the transfer speed of the user data, based on the resource of the transmission path, which is notified from the resource analyzing unit 26.
For example, when the resource of the transmission path is high (i.e., the communication quality is poor), the transfer speed determination unit 28 sets the upper limit of the transfer speed of the user data to be low. In contrast, when the resource of the transmission path is low (i.e., the communication quality is good), the transfer speed determination unit 28 sets the upper limit of the transfer speed of the user data to be high.
In addition, the transfer speed determination unit 28 may be configured to determine the transfer speed of the user data based on the moving speed of each of the mobile station, which is notified from the moving speed analyzing unit 27.
For example, when the mobile station 1 moves at a high speed (for example, the mobile station 1 moves by a Shinkansen super-express train, or the like), the transfer speed determination unit 28 determines the transfer speed of the user data so that the transfer speed of the user data is higher than the moving speed of the mobile station 1. It is due to prevent the mobile station 1, which is moving at the high speed, from moving to an other cell before the transfer of the user data is completed.
Note that the transfer speed determination unit 28 may be configured to determine the transfer speed, based on an index other than the foregoing descriptions.
As will be described later, the control unit 29 is configured to perform a control with regards to the handover of each of the mobile station 1, based on a measurement report from each of the mobile station 1.
By referring to
Firstly, by referring to
As shown in
In step S102, based on the measurement report from the mobile station 1, the handover source base station 2 determines whether the handover of the mobile station 1 is required. When the handover of the mobile station 1 is required, the handover source base station 2 selects a handover candidate base station 3 as the handover candidate base station which is appropriate to transmit a resource allocation request from the handover source base station 2, based on the measurement report received in step S101.
In step S103, the handover source base station 2 transmits the resource allocation request to the handover candidate base station 3 selected in step S102.
The above-described resource allocation request may include QoS information with regards to the mobile station 1. Note that such resource allocation request may be “UE context” of a control plane (C plane), or the like.
In step S104, the handover candidate base station 3 performs a resource allocation and a resource reservation for the mobile station 1, based on the QoS information with regards to the mobile station 1.
In step S105, the handover candidate base station 3 transmits a resource allocation response to the handover source base station 2.
Specifically, when the resource reservation for the mobile station 1 is successfully made, the handover candidate base station 3 notifies that a preparation for the handover of the mobile station 1 has been completed, to the handover source base station 2 by the resource allocation response. In such a case, the handover source base station 2 determines the handover candidate base station 3, as the handover target base station.
On the other hand, when the handover candidate bass station 3 falls to reserve a resource for the mobile station 1, the handover candidate base station 3 notifies that the resource for the mobile station 1 cannot be reserved, to the handover source base station 2 by the resource allocation response. In such a case, the present operation returns to step S102 and the handover source base station 2 selects an other handover candidate base station based on the measurement report, and performs the above-described processing.
In step S106, the handover source base station 2 transfers user data of the mobile station 1, which is stored in the buffer of the handover source base station 2, based on the transfer speed determined in a user data transfer speed determination processing (to be described later).
In step S107, the handover source base station 2 transmits, to the mobile station 1, a request of resetting a radio link.
The request of resetting the radio link includes information necessary for establishing a radio link between the mobile station 1 and the handover target base station 3 (for example, a spread cord or the like).
In step 108, the mobile station 1 performs the handover by resetting the radio link.
Specifically, the mobile station 1 switches the radio link from the handover source base station 2 to the handover target base station 3.
In step S109, the mobile station 1 transmits a radio link resetting completion report to the handover target base station 3 with which the radio link is established.
In step S110, the handover target base station 3 transmits a path update request to the access gateway 4. The access gateway 4 performs a path update, and updates a path of a destination address from the handover source base station 2 to the handover target base station 3.
In step S111, the access gateway 4 releases a signaling between the access gateway and the handover source base station 2.
Secondly, by referring to
As shown in
Thirdly, by referring to
As shown in
In step S302, the handover source base station 2 determines the transfer speed of the user data, based on the priority order analyzed in step S301. Specifically, this processing is performed by the transfer speed determination unit 28, which is shown in
In step S303, the handover source base station 2 transfers the user data, based on the transfer speed determined in step S302. Specifically, this processing is performed by the wired transmission unit 21, which is shown in
For example, as shown in
With the mobile communication system according to the present embodiment, it is possible to determine the transfer order of the user data so that the user data is transferred at an appropriate transfer speed, when the mobile station performs the handover. Accordingly, the user data of the mobile station can be effectively transferred to the handover target base station without losing any data.
In addition, with the mobile communication system according to the present embodiment, the handover source base station can determine the transfer speed of the user data having the high priority order to transfer at the high transfer speed. Accordingly, a communication of the user data having the high priority order can be performed without an interruption, at the handover target base station.
By referring to
As shown in
In step S402, the handover source base station 2 analyzes the priority order of the user data. Specifically, this processing is performed by the user data priority order analyzing unit 24, which is shown in
In step S403, the handover source base station 2 determines the transfer speed of the user data, based on the upper limit of the transfer speed analyzed in step S401 and the priority order analyzed in step S402. Specifically, this processing is performed by the transfer speed determination unit 28, which is shown in
In step S404, the handover source base station 2 transfers the user data, based on the transfer speed determined in step S403. Specifically, this processing is performed by the wired transmission unit 21, which is shown in
With the mobile communication system according to the first modified embodiment, it is possible to determine the transfer order of the user data by considering the upper limit of the transfer speed in the system, in addition to the priority order of the user data, when the mobile station performs the handover. Accordingly, the resource in the handover target base station and the resource of the transmission path can be effectively used.
As described above, the present invention is described by referring to the first embodiment. However, it should be understood that the description and drawings, which constitute one part of this disclosure, are not intended to limit the present invention. Various alternative embodiments, modifications, and operational techniques will be clear for those in the art from the present disclosure.
As described above, the present invention obviously includes various embodiments that are not described here. Accordingly, the technical scope of the present invention is only defined by the specific matters of the invention according to the scope of claims which are appropriate based on the above description.
The present invention can provide a data transfer method and a base station, which can effectively transfer user data of the mobile station to a handover target base station without losing any data, when the mobile station performs a handover.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-321640 | Nov 2005 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2006/321977 | 11/2/2006 | WO | 00 | 10/8/2008 |
