WO2015065062A1

WO2015065062A1 - Handover method and system

Info

Publication number: WO2015065062A1
Application number: PCT/KR2014/010294
Authority: WO
Inventors: Lixiang Xu; Xiaowan KE; Hong Wang
Original assignee: Samsung Electronics Co., Ltd.
Priority date: 2013-10-30
Filing date: 2014-10-30
Publication date: 2015-05-07
Also published as: CN104602307A

Abstract

The present invention discloses a handover method and system. The method includes: transmitting, by a first base station, a request message to a second base station, wherein the request message carries information of a source signaling gateway, the second base station comprises a target master base station or a new slave base station; transmitting, by the second base station, a response message to the first base station, wherein the response message indicates whether there is a direct connection between the second base station and the source signaling gateway, or indicates whether the second base station selects a target signaling gateway; after receiving a Radio Resource Control (RRC) reconfiguration complete message or a bearer establishment complete message, transmitting, by the second base station, a user plane handover message to the source signaling gateway when there is the direct connection between the second base station and the source signaling gateway; transmitting, by the second base station, the user plane handover message through at least one way at follows when there is not the direct connection between the second base station and the source signaling gateway: transmitting the user plane handover message to a mobility management entity (MME) corresponding to the second base station or a target signaling gateway, or forwarding the user plane handover message to the source signaling gateway through the first base station; and receiving, by the second base station, a user plane handover acknowledge message, wherein the user plane handover acknowledge message is transmitted from one of the first base station, the source signaling gateway, the target signaling gateway and the MME.

Description

HANDOVER METHOD AND SYSTEM

The present invention relates to a mobile communication technology field, and more particularly, to a handover method and system.

Modern mobile communication technology tends to provide a media traffic with a high rate transmission for users. FIG. 1 is a schematic diagram illustrating architecture of a SAE system.

A user equipment (UE) 101 is a terminal device to receive data. An Evolved Universal terrestrial radio access network (E-UTRAN) 102 is a wireless access network including macro base station (eNodeB (abbreviated as eNB)/NodeB) providing a wireless network access for the UE. A Mobility Management Entity (MME) 103 takes charge of managing UE mobile context, conversation context and security information. A serving gateway (SGW) 104 mainly provides a user plane function. The MME 103 and SGW 104 may be located in a same physical entity. A Packet Data Network Gateway (PGW) 105 takes charge of functions, e.g., billing and lawful interception, and may be located in a same physical entity with the SGW 104. A Policy Control and Charging Rules Function (PCRF) 106 provides policies of Quality of Service (QoS) and charging rules. A serving GPRS Support Node (SGSN) 108 is a network node device providing routing for data transmission in a Universal Mobile Telecommunications System (UMTS). A Home Subscriber Server (HSS) 109 is a home belonging sub-system, takes charge of user information, wherein the user information includes a user current location, an address of a serving node, user security information and a user packet data context.

At present, in a Long Term Evolution (LTE) system, a maximum bandwidth supported by each cell is 20MHz. In order to increase a peak rate of a UE and a transmission bandwidth, a LTE-Advanced system introduces a carrier aggregation technology. The UE can communicate with multiple cells working under different carrier frequencies at the same time through the carrier aggregation technology. In particular, the multiple cells provide service for a same user. These cells may belong to a same base station, or may belong to different base stations. Thus, the transmission bandwidth can reach 100MHz at most so as to multiply an uplink peak rate and an downlink peak rate of the UE.

FIG. 2 is a schematic diagram illustrating a carrier aggregation among eNBs. For a UE working in carrier aggregation, an aggregated cell includes a Primary Cell (PCell) and a Secondary Cell (Scell). The PCell is also referred as to a serving cell of the UE. There is one PCell for one UE. And the PCell is in an active status at all the time. The PCell can be changed through a handover process. Non-Access Stratum (NAS) information, a Physical Uplink Control Channel (PUCCH) can be transmitted and received only in the PCell by the UE.

A base station to which the PCell belongs is referred as to a Master eNB (MeNB). A base station to which the SCell belongs is referred as to a Slave eNB (SeNB).

When a coverage range of the MeNB is small, the UE may quickly leave the coverage range of the MeNB in a short time. The UE will be handed over to a new MeNB (referred as to a target MeNB). The target MeNB can transmit signaling to a core network in each handover process. In particular, after handing the UE to the target MeNB, the target MeNB can transmit a path handover request message to the core network. The core network transmits a path handover response message to the target MeNB. When handover of the MeNB is frequent, load of the core network is increased.

When a coverage range of the SeNB is small, the UE may quickly leave the coverage range of the SeNB in a short time. The MeNB is not handed over. The MeNB will configure a new SeNB for the UE. In this condition, the MeNB transmits signalings to the core network to indicate the core network to transmit data to the new SeNB (referred as to a new SeNB). In particular, the MeNB configures the new SeNB for the UE. When user plane data is directly transmitted from the core network to the SeNB and is not forwarded through the MeNB, the MeNB will transmit a user plane handover request message to the core network to indicate the core network to hand over a user plane to the new SeNB. After receiving the user plane handover message, the core network can transmit or not transmit a response message to the MeNB. The user plane handover message can be a newly-defined message, or can be an existing message, e.g., a path handover message. When the SeNB is handed over frequently, the load of the core network is increased.

In order to alleviate signal load of the core network and decrease interactive signalings between an access network and the core network, a function node between a base station and a core network can be added. The function node terminates signalings from a base station to the core network. In particular, the signalings transmitted to the core network is transmitted to the function node. The function node cannot forward the signalings to the core network, can directly resolute the signalings, and can transmit the response signaling. The function node can also have a user plane forwarding function. In particular, data transmitted by the core network can be transmitted to the function node, and can be transmitted to the MeNB and/or the SeNB by the function node. The function node can be an independent physical node, can be configured in a base station, i.e., the function node is implemented by the base station.

When the function node is configured in the base station, a suitable location of the function node is the MeNB of the UE. In order to make description clear, in the condition, the function node is referred as to a mobility anchor. When the UE moves, the mobility anchor is not changed as far as possible, i.e., not changing the MeNB. Thus, path handover processes caused because of MeNB handover is decreased, and interactive signalings between the access network and the core network is decreased. However, there is problems as follows: (1) when the UE moves, the MeNB may be far away from the UE, the UE cannot receive a signal from the MeNB, UE can release a Radio Resource Control (RRC) connection and enter an idle mode, data reception interrupts; (2) the MeNB of the UE may be far away from the new SeNB of the UE, when there is not a X2 interface between the MeNB and the new SeNB of the UE, the MeNB cannot set up a data bearer on the MeNB, thus, an intention of decreasing signaling load of the core network cannot be achieved.

When the function node is an independent physical entity, in order to make description clear, the function node is referred as to a S1 gateway. Messages transmitted from a base station to the core network ends in the S1 gateway so as to decrease signaling load of the core network. However, two problems above still exist in the condition, moreover, there is another problem how a suitable S1 gateway is selected for a target base station. When the MeNB is handed over, the S1 gateway of the target MeNB and the S1 gateway of the source MeNB may be two different physical entities. When the target MeNB cannot transmit to the corresponding S1 gateway signalings to be transmitted to the core network, the intention of decreasing the signaling load of the core network can be not achieved.

A handover method and system are provided according to embodiments of the present invention, so as to alleviate signaling load of a core network.

The technical solution according to the present invention is as follows.

A handover method is provided, which includes:

transmitting, by a first base station, a request message to a second base station, wherein the request message carries information of a source signaling gateway, the second base station comprises a target master base station or a new slave base station;

transmitting, by the second base station, a response message to the first base station, wherein the response message indicates whether there is a direct connection between the second base station and the source signaling gateway, or indicates whether the second base station selects a target signaling gateway;

After receiving a Radio Resource Control (RRC) reconfiguration complete message or a bearer establishment complete message, transmitting, by the second base station, a user plane handover message to the source signaling gateway when there is the direct connection between the second base station and the source signaling gateway; transmitting, by the second base station, the user plane handover message through at least one way at follows when there is not the direct connection between the second base station and the source signaling gateway: transmitting the user plane handover message to a mobility management entity (MME) corresponding to the second base station or a target signaling gateway, or forwarding the user plane handover message to the source signaling gateway through the first base station; and

receiving, by the second base station, a user plane handover acknowledge message, wherein the user plane handover acknowledge message is transmitted from one of the first base station, the source signaling gateway, the target signaling gateway and the MME.

A handover system is provided, which includes:

a first base station, to transmit a request message to a second base station, wherein the request message carries information of a source signaling gateway, the second base station comprises a target master base station or a new slave base station;

a second base station, to transmit a response message to the first base station, wherein the response message indicates whether there is a direct connection between the second base station and the source signaling gateway, or indicates whether the second base station selects a target signaling gateway; after receiving a Radio Resource Control (RRC) reconfiguration complete message or a bearer establishment complete message, transmit a user plane handover message to the source signaling gateway when there is the direct connection between the second base station and the source signaling gateway, transmit the user plane handover message through at least one way at follows when there is not the direct connection between the second base station and the source signaling gateway: transmitting the user plane handover message to a mobility management entity (MME) corresponding to the second base station or a target signaling gateway, or forwarding the user plane handover message to the source signaling gateway through the first base station; and receive a user plane handover acknowledge message, wherein the user plane handover acknowledge message is transmitted from one of the first base station, the source signaling gateway, the target signaling gateway and the MME.

A method for decreasing interactive signalings between an access network and a core network in a process of hand over a MeNB of the UE or a process of establishing a bearer in a new SeNB is provided according to an embodiment of the present invention. Thus, when the UE is moved to the new SeNB, signalings ends in a signaling gateway. Signaling load of the core network is decreased. When there is not a direct connection between the MeNB and the SeNB, the MeNB may be communicated with the new SeNB so that signalings to the core network is further decreased when a bearer is established in the new SeNB. When the MeNB is changed and/or the SeNB is changed, the target MeNB and/or the new SeNB can transmit a signaling to a correct signaling gateway so that the MeNB is ensured not to be handed over as far as possible. Thus, signalings of the core network can be decreased in various conditions, the signaling load of the core network is decreased, and network block caused because of heavy signaling load of the core network is avoided.

FIG. 1 is a schematic diagram illustrating existing architecture of a SAE system;

FIG. 2 is a schematic diagram illustrating a carrier aggregation among eNBs;

FIG. 3 is a schematic diagram illustrating a signal interaction of a handover method according to an embodiment of the present invention;

FIG. 4 is a schematic diagram illustrating a handover method when a new SeNB is configured according to embodiment 1 of the present invention;

FIG. 5 is a schematic diagram illustrating a handover method when a new SeNB is configured according to embodiment 2 of the present invention;

FIG. 6 is a schematic diagram illustrating a handover method when a new SeNB is configured according to embodiment 3 of the present invention;

FIG. 7 is a schematic diagram illustrating a handover method when a new SeNB is configured according to embodiment 4 of the present invention;

FIG. 8 is a schematic diagram illustrating a handover method when a new MeNB is configured according to embodiment 5 of the present invention;

FIG. 9 is a schematic diagram illustrating a structure of a handover system according to an embodiment of the present invention.

In order to a technical problem in prior art that signaling load is not decreased, a handover method and system is provided according to the following embodiments of the present invention, wherein the method may apply to the system.

In order to make description clear, function nodes added between a base station and a core network to alleviate signaling load of the core network and to decrease interactive signalings between an access network and the core network, i.e., a mobility anchor and a S1 gateway, are collectively referred to as signaling gateways.

A method for decreasing signalings transmitted to a core network in a process of changing a MeNB or SeNB of a UE is provided according to an embodiment of the present invention. As shown in FIG. 3, the method includes procedures as follows.

At block S301, a first base station transmits a request message to a second base station, wherein the request message carries information of a source signaling gateway, the request message may be a handover request message or a bearer establishment request message.

The first base station may be a (source) MeNB or a source SeNB of the UE. The second base station may be a target MeNB or a new SeNB of the UE.

When the first base station is the source MeNB of the UE and the second base station is the target MeNB, the process is a handover process of the MeNB of the UE. The first base station takes charge of Radio Resource Management (RRM) and Radio Resource Control (RRC), and transmits the handover request message to the second base station according to a measurement report of the UE.

When the first base station is the MeNB of the UE and the SeNB is the new SeNB, the process is a process of establishing a bearer. The first base station takes charge of RRM, and transmits the bearer establishment request message to the second base station according to a measurement report of the UE.

When the first base station is the source SeNB of the UE and the second base station is the new SeNB, the process is a process of establishing a bearer in the new SeNB. The first base station takes charge of mobility management of the UE (i.e., making a handover decision or a decision of establishing/releasing a bearer) and/or a radio message management function (i.e., transmitting a RRC message to the UE and receiving a RRC message from the UE). Except the first base station and second base station, the UE has another eNB as the MeNB. The MeNB and SeNB herein are respectively different from these defined in prior art. Thus, another name may be adopted. However, in order to make description convenient, the previous name is still adopted. The MeNB of the UE is a mobility anchor, and stores information of UE context, transmits a S1 signaling to the core network. Alternatively, the MeNB of the UE takes charge of making a handover decision or a bearer establishment decision, and takes charge of a radio message management function. The first base station takes charge of transmitting a RRC message to the UE and receiving a RRC message from the UE. In this condition, the first base station forwards the received RRC message to the MeNB, receives the RRC message from the MeNB and forwards the RRC message to the UE. For example, the first base station receives the measurement report from the UE, and forwards the measurement report to the MeNB. Thus, the MeNB may determine whether handover is performed. In the embodiment, a forwarding process between the MeNB and the first base station is omitted.

At block S301, an intention of the handover request message or the bearer establishment message is to configure the new MeNB or to configure the new SeNB and establish a bearer in the new SeNB. The message carries information of a source signaling gateway. The information of the source signaling gateway may be an identifier (ID) of the source signaling gateway or indication information of the signaling gateway. The source signaling gateway is a signaling gateway used by the first base station. The source signaling gateway may be in a same entity with the MeNB (i.e., the source signaling gateway is located in the MeNB of the UE), or may be an independent physical entity. When the source signaling gateway and the MeNB are in the same entity, the identifier of the source signaling gateway may be an identifier of the MeNB. The identifier of the signaling gateway identifies the entity where the signaling gateway locates. Through the identifier, the physical entity where the signaling entity is located may be searched out. When the source signaling gateway and the MeNB is in the same entity, the indication information of the signaling gateway indicates that the first base station has a function of a signaling gateway.

The handover request message may further carry a RRC container and encryption related information. In an example, the encryption related information may be KeNB and NCC.

At block S302, the second base station transmits a response message to the first base station, wherein the response message may indicate whether there is a direct connection between the second base station and the source signaling gateway, or may indicate whether the second base station selects a new signaling gateway, wherein the new signaling gateway selected by the second base station is referred as to a target signaling gateway.

When the request message at block S301 is the handover request message, the response message at block S302 is a handover response message. When the request message at block S301 is the bearer establishment request message, the response message at block S302 is a bearer establishment response message.

The second base station determines whether there is the direct connection between the second base station and a node indicated through the information of the source signaling gateway according to the information of the source signaling gateway carried in the received handover request message or the bearer establishment request message, wherein the direct connection may include a X2 interface or a newly-defined interface.

The response message may be used to indicate whether there is the direct connection between the second base station and the source signaling gateway. In particular, the indication information may be carried in the handover response message or bearer establishment response message, wherein the indication message may indicate whether there is the direct connection between the second base station and the source signaling gateway. Alternatively, when there is not the direct connection between the second base station and the source signaling gateway, the indication information is carried in the handover response message or bearer establishment response message, wherein the indication message may indicate that there is not the direct connection between the second base station and the source signaling gateway.

In addition, the handover response message may further carry a RRC container, wherein the RRC container carries a handover command message configured for the UE by the second base station.

At block S303, the second base station transmits a RRC reconfiguration request message to the UE.

The first base station transmits the RRC reconfiguration request message to the UE to indicate bearer configuration information of the target MeNB or the new SeNB, e.g., to indicate the identifier and configuration of the target MeNB or the new MeNB.

At block S304, the UE transmits a RRC reconfiguration complete message to the first base station or the second base station.

When a process of handing over the MeNB is performed, the UE transmits a RRC reconfiguration complete message to the target MeNB, i.e., the second base station. When the new SeNB is configured, the UE transmits the RRC reconfiguration complete message to the first base station, and the first base station transmits a bearer establishment complete message to the second base station.

At block S305, when there is the direct connection between the second base station and the source signaling gateway, the second base station transmits a user plane handover message to the source signaling gateway. When there is not the direct connection between the second base station and the source signaling gateway, the second base station may not transmit the user plane handover message to the source signaling gateway. The second base station transmits the user plane handover message through at least one way as follows: transmitting the user plane handover message to a Mobility Management Entity (MME) corresponding to the second base station or the target signaling gateway, or forwarding the user plane handover message to the source signaling gateway through the first base station.

The user plane handover message may include a transport layer address assigned by the second base station for receiving data, e.g., an Internet Protocol (IP) address and a tunnel number.

When there is not the direct connection between the second base station and the source signaling gateway, the second base station transmits the user plane handover message to the MME or the target signaling gateway. The first base station deletes the information related with the UE in the source signaling gateway and/or the first base station according to the indication information at block S302. Alternatively, the base station forwards the indication information to the source signaling gateway, and then the source signaling gateway and the first base station respectively delete the information related with the UE stored in local.

When the user plane handover message is transmitted to the source signaling gateway, the source signaling gateway initiates a gateway reconfiguration process, which includes blocks 11-13.

At block 11, the source signaling gateway transmits a signaling gateway reconfiguration request message to the second base station, wherein the message may be forwarded through the first base station, and may include UE context information.

At block 12, the second base station transmits a signaling gateway reconfiguration response message to the source signaling gateway, wherein the message may be forwarded through the first base station.

At block 13, the second base station transmits a message of indicating information of receiving new data to the MME, wherein the information of receiving the data may include transport layer address information. Afterwards, the MME transmits a user plane handover acknowledge message to the second base station.

Some ways of transmitting the user plane handover message when there is not the direct connection between the second base station and the source signaling gateway. In a practical application, there is another implementation way, which is not limited in the present invention.

At block S306, the second base station receives the user plane handover acknowledge message, wherein the user plane handover acknowledge message is transmitted from one of the first base station, the source signaling gateway, the target signaling gateway and the MME.

When there is not the direct connection between the second base station and the source signaling gateway, the user plane handover acknowledge message is transmitted from one of the MME, the first base station and the target signaling gateway to the second base station. When there is the direct connection between the second base station and the source signaling gateway, the user plane handover acknowledge message is transmitted from the source signaling gateway to the second base station.

The user plane handover acknowledge message may carry new encryption information.

The method according to the above embodiment is illustrated in detail through some embodiments as follows.

Embodiment 1

In embodiment 1, a first base station is a MeNB, and a second base station is a new SeNB.

The signaling gateway is implemented in the MeNB. The MeNB configures the new SeNB for the UE. A data bearer is handed over from the source SeNB to the new SeNB. The new SeNB provides the data bearer for a user. User data is transmitted from the core network to the MeNB, and then forwarded to the SeNB. There is a direct connection between the MeNB and the source SeNB, e.g., a X2 interface. There is a direct connection between the MeNB and the new SeNB, e.g., a X2 interface. As shown in FIG. 4, the handover method according to the embodiment 1 includes procedures as follows.

At block S401, a MeNB of a UE receives a measurement report of the UE.

The UE transmits the measurement report to a source SeNB. The source SeNB forwards the measurement report to the MeNB. Alternatively, the UE directly transmits the measurement report to the MeNB.

At block S402, the MeNB transmits a bearer establishment request message to the new SeNB, wherein the bearer establishment request message carries indication information of a source signaling gateway.

According to the measurement report, the MeNB determines that the data bearer is handed over from the source SeNB to the new SeNB.

The indication information of the signaling gateway carried in the bearer establishment request message indicates that a function of a signaling gateway is implemented in the MeNB. The information is indicated through an identifier of the signaling gateway.

The bearer establishment request message may further include a RRC container, wherein the RRC container includes bearer configuration information, wherein the bearer configuration information may further carry encryption related information, e.g., a key KeNB and NCC.

At block S403, the new SeNB transmits a bearer establishment response message to the MeNB.

The bearer establishment response message may carry a RRC container, wherein the RRC container may carry a handover command message configured to the UE by the second base station.

At block S404, the MeNB forwards the RRC container in the bearer establishment response message to the source SeNB. The source SeNB transmits the RRC reconfiguration request message to the UE. Alternatively, the MeNB transmits the RRC reconfiguration request message to the UE.

At block S405, the UE transmits the RRC reconfiguration complete message to the MeNB, the MeNB transmits a bearer establishment complete message to the new SeNB.

At block S406, the new SeNB transmits a user plane handover message to the MeNB.

At block S407, the MeNB transmits a user plane handover acknowledge message to the new SeNB.

At block S408, the MeNB transmits a bearer release request to the source SeNB.

At block S409, the source SeNB transmits a bearer release response message to the MeNB.

So far, the process of embodiment 1 ends.

Embodiment 2

In embodiment 2, a first base station is a source SeNB, and a second base station is a new SeNB.

The signaling gateway is in a MeNB of the UE. A RRC of the UE is in a source SeNB. A Mobility Management Entity is in a source SeNB. The source SeNB configures a new SeNB for the UE. A data bearer is handed over from the source SeNB to a new SeNB. The new SeNB provides the data bearer for a user. User data is transmitted from the core network to the MeNB, and then forwarded to the SeNB by the MeNB. There is a direct connection between the MeNB and the source SeNB, e.g., a X2 interface. There is a direct connection between the MeNB and the new SeNB, e.g., a X2 interface. As shown in FIG. 5, the handover method according to embodiment 2 includes procedures as follows.

At block S501, the source SeNB transmits a bearer establishment request message to the new SeNB, wherein the bearer establishment request message carries an identifier of a source signaling gateway.

According to a measurement report, the source SeNB determines that the data bearer is handed over from the source SeNB to the new SeNB.

The identifier of the source signaling gateway carried in the bearer establishment request message identifies a physical entity where the source signaling gateway locates in a network. The physical entity where the source signaling gateway locates may be searched out according to the identifier.

The bearer establishment request message may further include a RRC container, wherein the RRC container includes bearer configuration information, and the bearer configuration information may further carry encryption related information, e.g., a key KeNB and NCC.

At block S502, the new SeNB transmits a bearer establishment response message to the source SeNB.

The bearer establishment response message may further carry a RRC container, wherein the RRC container may carry a handover command message configured to the UE by the new SeNB.

At block S503, the source SeNB transmits a RRC reconfiguration request message to the UE.

The RRC reconfiguration request message may include the RRC container in the bearer establishment response message.

At block S504, the UE transmits the RRC reconfiguration complete message to the source SeNB, the source SeNB transmits a bearer establishment complete message to the new SeNB.

At block S505, the new SeNB transmits a user plane handover message to the source signaling gateway, i.e., a node indicated through the identifier of the source signaling gateway. For example, in the embodiment, the node may be the MeNB. Alternatively, the node may be an independent network entity, e.g., a S1 gateway.

At block S506, the MeNB transmits a user plane handover acknowledge message to the new SeNB.

At block S507, the MeNB transmits a bearer release request to the source SeNB.

At block S508, the source SeNB transmits a bearer release response message to the MeNB.

So far, the process in embodiment 2 ends.

Embodiment 3

In embodiment 3, a first base station is a source SeNB, and a second base station is a new SeNB.

The signaling gateway is in a MeNB. A RRC of the UE is in the source SeNB. A Mobility Management Entity is in the source SeNB. The source SeNB configures the new SeNB for the UE. A data bearer is handed over from the source SeNB to the new SeNB. The new SeNB provides the data bearer for a user. User data is transmitted from the core network to the MeNB, and then forwarded to the SeNB. There is a direct connection between the MeNB and the source SeNB, e.g., a X2 interface. There is not a direct connection between the MeNB and the new SeNB, e.g., a X2 interface. As shown in FIG. 6, the handover method according to embodiment 3 includes procedures as follows.

At block S601, the source SeNB transmits a bearer establishment request message to the new SeNB, wherein the bearer establishment request message carries an identifier of a source signaling gateway.

The identifier of the source signaling gateway carried in the bearer establishment request message identifies an entity where the source signaling gateway locates in a network. The physical entity where the source signaling gateway locates may be searched out according to the identifier.

The bearer establishment request message may further include a RRC container, wherein the RRC container includes bearer configuration information, and the bearer configuration information may carry encryption related information, e.g., a key KeNB and NCC. The bearer configuration information may further carry an identifier of the MME of the source core network.

At block S602, the new SeNB transmits a bearer establishment response message to the source SeNB.

The bearer establishment response message carries indication information, wherein the indication information indicates that there is not a direct connection between the new SeNB and the source signaling gateway.

The bearer establishment response message may carry a RRC container, wherein the RRC container may carry a handover command message configured for the UE by the new SeNB.

At block S603, the source SeNB transmits a RRC reconfiguration request message to the UE.

At block S604, the UE transmits the RRC reconfiguration complete message to the source SeNB, the source SeNB transmits a bearer establishment complete message to the new SeNB.

At block S605, the new SeNB transmits a path handover request message to a corresponding MME.

When there is a connection between the new SeNB and the MME identified through a MME identifier carried in the bearer establishment request message, the new SeNB transmits the path handover request message to the MME. When there is not a connection between the new SeNB and the MME identified through the MME identifier carried in the bearer establishment request message, the new SeNB transmits the path handover request message to a target MME with which the new SeNB has a connection. The path handover request message carries an identifier of a source MME. Afterwards, the target MME searches out the source MME according to the identifier, and obtains the UE context information from the source MME.

At block S606, the MME transmits a path handover response message to the new SeNB, wherein the path handover response message carries new encryption information.

Afterwards, the new SeNB becomes the MeNB of the UE.

At block 607, the new SeNB transmits a handover complete message to the source SeNB, indication information may further be carried in the handover complete message to indicate whether there is the direct connection between the new SeNB and the source signaling gateway.

Alternatively, block S607 may be omitted, and may be not performed.

At block S608, the source SeNB transmits a UE context deletion request to the MeNB.

At block S609, the MeNB transmits a UE context deletion response message to the source SeNB. The MeNB may also release the UE context

So far, the process of embodiment 3 ends.

Embodiment 4

The signaling gateway is in a MeNB. A RRC of the UE is in the source SeNB. A Mobility Management Entity is in a source SeNB. The source SeNB configures the new SeNB for the UE. A data bearer is handed over from the source SeNB to the new SeNB. The new SeNB provides the data bearer for a user. User data is transmitted from the core network to the MeNB, and then forwarded to the SeNB. There is a direct connection between the MeNB and the source SeNB, e.g., a X2 interface. There is not a direct connection between the MeNB and the new SeNB, e.g., a X2 interface. As shown in FIG. 7, the handover method according to Embodiment 4 includes procedures as follows.

At block S701, the source SeNB transmits a bearer establishment request message to the new SeNB, wherein the bearer establishment request message carries an identifier of the source signaling gateway.

At block S702, the new SeNB transmits a bearer establishment response message to the source SeNB.

At block S703, the source SeNB transmits a RRC reconfiguration request message to the UE.

At block S704, the UE transmits a RRC reconfiguration complete message to the source SeNB, the source SeNB transmits a bearer establishment complete message to the new SeNB.

At block S705, the new SeNB transmits a user plane handover message to the source SeNB. Indication information may be carried in the user plane handover message to indicate that there is not the direct connection between the new SeNB and the source signaling gateway.

At block S706, the source SeNB forwards the user plane handover message to a node identified through an identifier of the source signaling gateway. In the embodiment, the source signaling gateway is located together with the MeNB.

At block S707, the MeNB initiates a signaling gateway reconfiguration process, transmits a signaling gateway reconfiguration request message to the source SeNB.

At block S708, the source SeNB forwards the signaling gateway reconfiguration request message to the new SeNB.

At block S709, the new SeNB transmits a signaling gateway reconfiguration response message to the source SeNB.

At block S710, the source SeNB forwards the signaling gateway reconfiguration response message to the MeNB.

At block S711, the new SeNB transmits a path handover request message to a corresponding MME.

The path handover request indicates information of receiving new data.

At block S712, the MME transmits a path handover response message to the new SeNB, wherein the path handover response message carries new encryption information.

Afterwards, the new SeNB becomes the MeNB of the UE.

So far, the process in embodiment 4 ends.

Embodiment 5

In embodiment 5 of the present invention, there is a process of handing over the MeNB. The first base station is a source MeNB. The second base station is a target MeNB.

A source signaling gateway is an independent physical entity. The source MeNB configures a new MeNB (called as the target MeNB) for the UE.

As shown in FIG. 8, a handover method according to embodiment 5 of the present invention may include procedures as follows.

At block S801, the source MeNB transmits a handover request message to the target MeNB, wherein the handover request message carries an identifier of a source signaling gateway.

According to a measurement report, a source MeNB determines to hand over the UE to the target MeNB.

The handover request message may further include a RRC container, wherein the RRC container includes handover preparation information, and the handover request message may further carry encryption related information, e.g., a key KeNB and NCC.

At block S802, the target MeNB transmits a handover response message to the source MeNB.

The handover response message carries indication information to indicate whether there is the direct connection between the target MeNB and the source signaling base station and whether the target MeNB selects a new signaling gateway (referred as to a target signaling gateway). The indication information is used to make the source MeNB release UE related information in the source signaling gateway. The indication information may be omitted, and may be indicated in steps as follows.

The handover response message may further carry a RRC container. The RRC container may carry a handover command message configured by the target MeNB to the UE.

At block S803, the source base station forwards the RRC container carried in the handover response message to the UE, wherein the RRC container is carried in a RRC reconfiguration request message.

At block S804, the UE transmits a RRC reconfiguration complete message to the target MeNB.

At block S805, the target MeNB transmits a path handover request message to a corresponding MME or a corresponding signaling gateway.

When there is the direct connection between the target MeNB and the source signaling gateway, the target MeNB transmits a path handover request message to the source signaling gateway.

When there is not the direct connection between the target MeNB and the source signaling gateway and the target MeNB configures a corresponding signaling gateway (referred as to the target signaling gateway), the target MeNB transmits the path handover request message to the target signaling gateway. When the target MeNB may not configure a corresponding signaling gateway (referred as to the target signaling gateway), the target MeNB transmits the path handover request message to a core network node MME.

The path handover request message may carry an identifier of the source signaling gateway, and may further carry a source MME identifier.

At block S806, the target signaling gateway transmits a path handover request message to a corresponding target MME, wherein the path handover request message carries an identifier of the source signaling gateway and an identifier of a source MME.

When the target signaling gateway and the source signaling network are located in an entity (i.e., the target MeNB has the direct connection with the source signaling network), procedures at blocks S806-S812 may be omitted and may not be performed.

When the target signaling gateway and the source signaling network are not located in an entity (i.e., the target MeNB does not have the direct connection with the source signaling network), procedures at blocks S806-S812 may be performed. When a corresponding target signaling gateway may not be configured for a target serving base station, a procedure at block S806 may be not performed.

After receiving the path handover request message, the target MME searches out a corresponding source MME through a MME identifier carried in the path handover request message, and obtains UE context information from the source MME.

At block S807, the MME transmits a path handover response message to the target signaling gateway, wherein the path handover response message carries new encryption information.

At block S808, the target signaling gateway transmits a path handover response message to the target MeNB, wherein the path handover response message carries the new encryption information.

Afterwards, the target MeNB becomes the MeNB of the UE.

When there is not the direct connection between the target MeNB and the source signal gateway and the corresponding target signaling gateway may not be configured for the target MeNB, at blocks S807-S808, the MME directly transmits the path handover response message to the target MeNB.

At block S809, the target MeNB transmits a UE context deletion request to the source MeNB.

At block S810, the source MeNB transmits a UE context deletion response message to the target MeNB.

At block S811, the MME transmits a UE information deletion request message to the source signaling gateway.

At this block, the source MeNB transmits the UE information deletion request message to the source signaling gateway. The source MeNB needs to obtain that the target MeNB selects a new signaling gateway, indication information at block S802 or indication information in the message at block S809 indicates there is not the direct connection between the target MeNB and the source signaling gateway and the target MeNB selects the new signaling gateway.

At block S812, the source signaling gateway transmits the UE information deletion response message to the MME.

At this block, the UE information deletion response message may be transmitted from the source MeNB to the source signaling gateway.

So far, the process in embodiment 5 ends.

According to a method in above embodiments, a system to which the method applies is provided according to an embodiment of the present invention. As shown in FIG. 9, the system includes a first base station 10 and a second base station 20.

The first base station 10 is a MeNB of the UE, may be as a mobility anchor. The MeNB takes charge of transmitting a message to a MME and managing a RRC connection and mobility of the UE. The RRC message generated by the MeNB is transmitted to the UE through a SeNB. The SeNB receives a RRC message transmitted from the UE, and forwards the RRC message to the MeNB.

The second base station 20 is a SeNB, and takes charge of transmitting the RRC message generated by the base station 10 to the UE, establishing a new SeNB and establishing a bearer in the new SeNB. The bearer is established when the MeNB makes a decision and and a command from the MeNB is received.

In order to decrease signaling load when the MeNB of the UE is handed over or a bearer is established in the new SeNB, the process of interacting signalings between the first base station 10, the second base station 20 and another node refers to that in the method according to embodiments above, which is not described repeatedly herein.

A benefit as follows can be achieved according to embodiments above.

The foregoing is only preferred examples of the present invention and is not used to limit the protection scope of the present invention. Any modification, equivalent substitution and improvement without departing from the spirit and principle of the present invention are within the protection scope of the present invention.

Claims

A handover method, comprising:transmitting, by a first base station, a request message to a second base station, wherein the request message carries information of a source signaling gateway, the second base station comprises a target master base station or a new slave base station;transmitting, by the second base station, a response message to the first base station, wherein the response message indicates whether there is a direct connection between the second base station and the source signaling gateway, or indicates whether the second base station selects a target signaling gateway;after receiving a Radio Resource Control (RRC) reconfiguration complete message or a bearer establishment complete message, transmitting, by the second base station, a user plane handover message to the source signaling gateway when there is the direct connection between the second base station and the source signaling gateway; transmitting, by the second base station, the user plane handover message through at least one way at follows when there is not the direct connection between the second base station and the source signaling gateway: transmitting the user plane handover message to a mobility management entity (MME) corresponding to the second base station or a target signaling gateway, or forwarding the user plane handover message to the source signaling gateway through the first base station; andreceiving, by the second base station, a user plane handover acknowledge message, wherein the user plane handover acknowledge message is transmitted from one of the first base station, the source signaling gateway, the target signaling gateway and the MME.
The method of claim 1, wherein the response message is a handover response message when the request message is a handover request message; the response message is a bearer establishment response message when the request message is a bearer establishment request message.
The method of claim 1, wherein the information of the source signaling gateway comprises an identifier (ID) of the source signaling gateway or indication information of the source signaling gateway, wherein the indication information of the source signaling gateway indicates that the first base station comprises a function of a signaling gateway.
The method of claim 1, wherein the response message carries indication information, wherein the indication information indicates whether there is the direct connection between the second base station and the source signaling gateway, or the indication information indicates that there is not the direct connection between the second base station and the source signaling gateway.
The method of claim 1, wherein the direct connection comprises a X2 interface or a newly-defined interface.
The method of claim 1, further comprising:transmitting, by the first base station, a RRC reconfiguration request message to a UE after the second base station transmits the response message to the first base station and before the second base station receives the RRC reconfiguration complete message or the bearer establishment complete message;the process of the second base station receiving the RRC reconfiguration complete message or the bearer establishment complete message comprises:receiving, by the second base station, the RRC reconfiguration complete message from the UE; or receiving, by the second base station, the bearer establishment complete message after the second base station receives the RRC reconfiguration complete message from the UE.
The method of claim 1, wherein the first base station comprises a source master base station, the second base station comprises the target master base station; or the first base station comprises the master base station, the second base station comprises the new slave base station; or the first base station comprises a source slave base station, the second base station comprises the new slave base station.
The method of any of claims 1-7, after the second base station forwards the user plane handover message to the source signaling gateway through the first base station, further comprising:receiving, by the second base station, a signaling gateway reconfiguration request message from the source signaling gateway;transmitting, by the second base station, a signaling gateway reconfiguration response message to the source signaling gateway;transmitting, by the second base station, a message of indicating information of receiving new data to the MME.
The method of claim 8, wherein the signaling gateway reconfiguration request message is forwarded to the second base station through the first base station; the signaling gateway reconfiguration response message is forwarded to the source signaling gateway through the first base station.
The method of any of claims 1-7, wherein the first base station comprises the source slave base station, the second base station comprises the new slave base station, there is not the direct connection between the second base station and the source signaling base station, there is the direct connection between the first base station and the source signaling gateway;the process of the second base station transmitting the user plane handover message comprises:transmitting, by the new slave base station, the user plane handover message to the MME;the method further comprising:receiving a UE context deletion response message transmitted from the master base station after the second base station receives the user plane handover acknowledge message transmitted from the MME and the source slave base station transmits a UE context deletion request message to the master base station.
A handover system, comprising:a first base station, to transmit a request message to a second base station, wherein the request message carries information of a source signaling gateway, the second base station comprises a target master base station or a new slave base station;a second base station, to transmit a response message to the first base station, wherein the response message indicates whether there is a direct connection between the second base station and the source signaling gateway, or indicates whether the second base station selects a target signaling gateway; after receiving a Radio Resource Control (RRC) reconfiguration complete message or a bearer establishment complete message, transmit a user plane handover message to the source signaling gateway when there is the direct connection between the second base station and the source signaling gateway, transmit the user plane handover message through at least one way at follows when there is not the direct connection between the second base station and the source signaling gateway: transmitting the user plane handover message to a mobility management entity (MME) corresponding to the second base station or a target signaling gateway, or forwarding the user plane handover message to the source signaling gateway through the first base station; and receive a user plane handover acknowledge message, wherein the user plane handover acknowledge message is transmitted from one of the first base station, the source signaling gateway, the target signaling gateway and the MME.