Patent Description:
Under heterogeneous networks, in a network covered by a macro base station (Macro eNodeB), there is a plurality of small cellular base stations, which perform wired communication or wireless communication with the macro base station. When a terminal moves in the network covered by the macro base station, inevitably, the terminal needs to change a control plane unceasingly, resulting in handovers.

Currently, an existing handover method includes: transmitting, by a UE, a measurement report to a source eNodeB; making, by the source eNodeB, a handover decision based on the measurement report and other information, and selecting a target cell for the UE; transmitting, by the source eNodeB, a handover request message to a target eNodeB, so that the target eNodeB performs an admission control after receiving the handover request message; then, transmitting, by the target eNodeB, a handover acknowledge message to the source eNodeB, if the target eNodeB agrees with a handover of the serving eNodeB for the terminal; the handover request message including configuration information of the target cell; transmitting, by the source eNodeB, a handover command message to the UE; transmitting, by the source eNodeB, an SN status transfer message to the target base station to inform the target base station of uplink PDCP SN reception status (uplink PDCP SN receiver status) of the UE and downlink packet data convergence protocol PDCP sequence number transmission status (PDCP SN, the downlink PDCP SN transmitter status) of the UE, so that the target eNodeB knows data transfer status of the current UE; then, transmitting, by the UE, a random access preamble to the target eNodeB, after the handover command message is received; transmitting, by the target eNodeB, a random access response message to the UE; transmitting, by the UE, a handover complete message to the target eNB; subsequently, performing, by the target eNodeB, a path selection procedure, i.e. acquiring path information from a gateway via a mobility management entity (MME), since the gateway do not know that the control plane has been switched, the gateway will transmit the path information to the source eNodeB and the target eNodeB via the MME generally.

In a current implementation, when a UE moves in the network covered by the macro base station, the control plane needs to be changed unceasingly and, thereby resulting in the handover described above, during the handover, data transfer may be interrupted, and thus affecting the usage of a user, therefore, the technical problem that remains to be solved at present lies in communication interruptions caused by frequently switching a control plane by a UE when moving in a macro network.

<CIT> discloses a method for accessing a base station, including: establishing, by a current macro base station, a control-plane-connection with a user equipment according to an access request of the UE, and allocating a first cell-radio network temporary identity (C-RNTI) to the user equipment; and when receiving a measurement report of micro base stations reported by the user equipment, selecting a micro base station for the user equipment according to a preset strategy so that the user equipment establishes a data-plane-connection with the micro base station, and notifying context information of the user equipment to the micro base station, wherein the context information includes the first C-RNTI allocated to the user equipment.

Embodiments of the present invention provide a handover control method and apparatus, so as to solve the technical problem of communication interruptions caused by frequently switching a control plane by a UE when moving in a macro network.

Advantageous features are defined in the dependent claims.

It can be known from the above technical solutions that, a source base station transmits indication to a target base station, so that the target base station, after acquiring the indication, does not reserve resources used for data scheduling for a handover of the UE, or release resources used for data scheduling which are reserved for a handover of the UE. Therefore, in a case where a user plane remains unchanged and a control plane is switched, a normal communication is ensured for the UE.

In order to make technical solutions in embodiments of the present invention or the prior art more clearly, the accompanying drawings used in the embodiments are briefly described hereunder. Obviously, the described drawings are merely some embodiments of the present invention. For persons skilled in the art, other drawings may also be obtained based on these drawings without any inventive efforts.

Technical solutions in embodiments of the present invention are hereinafter described clearly and completely with reference to accompanying drawings in embodiments of the present invention. Obviously, the described embodiments are only a part of embodiments of the present invention, rather than all embodiments of the present invention. All the other embodiments obtained by persons of ordinary skill in the art based on embodiments of the present invention without any inventive efforts shall fall within the protection scope of the present invention.

Reference may be made to <FIG> which is a flow chart of a handover control method according to an embodiment of the present invention; the method includes:
Step <NUM>, transmitting indication to a target base station, where the indication includes: first indication indicating that a user plane (User Plane) of a user equipment (UE) remains unchanged, and a control plane (Control Plane) of the UE is switched to the target base station; or second indication indicating that a control plane for the UE is switched to the target base station, and user data of the UE is transmitted by a small cell base station; or third indication indicating that both a user plane and a control plane for the UE are switched to the target base station;.

In this embodiment, there is a plurality of ways for a source base station to transmit the indication to a target base station, any message capable of carrying the indication is fine, two implementations are taken as examples in the following, which is not limited thereto, specifically including:.

One way is that: a source base station may transmit indication to the target base station via a handover request message, i.e. the indication is carried in the handover request message; the indication includes the first indication, the second indication or the third indication;.

Another way is a negotiation way that: before transmitting the indication to the target base station,.

These ways enable the target base station to know that the user plane remains unchanged and the control plane is switched or know that the control plane is switched and all user data of the UE is transmitted by the small cell base station, and it is no need to reserve a resource used for data scheduling for a handover of the UE.

Step <NUM>, receiving a handover acknowledge message that is transmitted by the target base station in response to the indication;.

In this step, after the source base station transmits the handover command to the UE, the UE initiates a random access to the target base station, and accesses to the target base station.

In embodiments of the present invention, a source base station notifies a target base station of indication indicating that a user plane remains unchanged and a control plane is switched; or indication indicating that a control plane is switched and all user data of a UE is transmitted by a small cell base station, so that the target base station, after acquiring the indication, does not reserve a resource used for data scheduling for a handover of the UE. Therefore, in a case where a user plane remains unchanged and a control plane is switched, a normal communication is ensured for the UE during a handover. Or, in a case where both a user plane and a control plane are switched, a normal communication is ensured for the UE.

Alternatively, in the embodiments, before transmitting the indication to the target base station, the method may further include: receiving a measurement report transmitted by a user equipment UE; selecting a target base station for the UE according to the measurement report; where, the measurement report may include: a measurement result of a cell covered by a small cell base station and/or measurement results of a cell covered by a candidate for target base station of handover, and so on. Specifically, the measurement result include {a cell identity of a small cell base station, a measurement result} and/or {a cell identity under a base station, a measurement result} respectively;
Alternatively, in this embodiment, a value of the indication may be set to <NUM> or <NUM> or <NUM>, certainly, may also be set to other values, for example, <NUM>, <NUM> or <NUM>, or <NUM>. As long as values set for the first indication, the second indication and the third indication in the indication are different from each other, it will be fine. This embodiment will not make a limitation.

Alternatively, in order to facilitate the target base station to know in which base station user data of the UE is transmitted, the handover request message may also include: an identity of a small cell base station, or a cell identity of a small cell base station.

Alternatively, the handover request message also includes: an identity of a small cell base station, or a cell identity of a small cell base station; or, also includes indication indicating that the control plane for the UE is separated from the user plane.

Alternatively, when or after receiving the handover acknowledge message transmitted by the target base station, the method may also include: transmitting information to the small cell base station for stopping transmitting data to the UE; and after the UE accesses to the target base station, transmitting, by a source base station or the target base station information to the small cell base station for continuing transmitting data to the UE. In this embodiment, the transmitted data may be encrypted using the original key, and the transmitted data may also be encrypted using an acquired new key. This embodiment will not make a limitation.

A process for acquiring the new key is: after the UE accesses to the target base station, and before transmitting the information to the small cell base station for continuing transmitting data to the UE, the method may also include: acquiring a new next hop key (NH, Next HOP key) and a next hop chaining counter (NCC, Next Hop Chaining Counter), and generating a new access stratus (AS, Access Stratum) key according to the NH; and transmitting the new AS key, the NCC and an evolved universal terrestrial radio access network radio access bearer identity (E-RAB ID, E-UTRAN Radio Access Bearer) to the small cell base station.

The acquiring the NH and the NCC specifically includes: receiving the NH and the NCC transmitted by the target base station; or, initiatively acquiring the NH and the NCC from the target base station; where, the NH and the NCC are acquired by the target base station from an MME during a path selection.

In embodiments of the present invention, a source base station may transmit indication to a target base station via a single message, may also notify the target base station of the indication via a plurality of messages (through negotiations), may also transmit an indication message (a single message, a plurality of messages/a negotiation way, etc.) to the target base station before the UE switches, and may also transmit an indication message to the target base station during a switching procedure of the UE (e.g., transmit the indication in a handover request message. ), hence, the target base station, after acquiring the indication, may not reserve a resource used for data scheduling for a handover of the UE; thus, in a case where a user plane remains unchanged and a control plane is switched, a normal communication is ensured for the UE and user satisfaction is improved.

Furthermore, in embodiments of the present invention, the source base station may also transmit information to the small cell base station for stopping transmitting data to the UE; and after the UE accesses to the target base station, the source base station or the target base station transmits information to the small cell base station for continuing transmitting data to the UE. The information for continuing transmitting data to the UE may use the original key to encrypt the data, and may also acquire a new key and use the new key to encrypt the data, so as to ensure security of the data transfer.

Reference may also be made to <FIG> which is a second flow chart of a handover control method according to an embodiment of the present invention, the method includes:.

Certainly, in this embodiment, the first indication, the second indication or the third indication may also be acquired through negotiations, reference may be made to the above embodiments for details of a specific negotiation procedure, which will not be repeated herein.

Step <NUM>, transmitting a handover command to the UE, so as to indicate the UE to access to the target base station.

In embodiments of the present invention, after receiving or acquiring first indication or second indication or third indication from the target base station, the source base station can know that the target base station does not reserve a resource used for data scheduling for a handover of the UE according to the first indication or the second indication or the third indication; and then, transmit the handover command to the UE, so as to indicate the UE to access to the target base station, thereby ensuring that in a case where the user plane remains unchanged and the control plane is switched, a normal communication is ensured for the UE during its handover procedure.

Alternatively, before step <NUM>, the method may also include: receiving a measurement report transmitted by a user equipment (UE); selecting a target base station for the UE according to the measurement report; acquiring configuration information of the target base station from the target base station.

Alternatively, in this embodiment, values set for the first indication, the second indication and the third indication are different from each other, for example, a value of the first indication may be set to <NUM>, a value of the second indication may be set to <NUM>, and a value of the third indication can be set to <NUM>; certainly, they are not limited thereto, and may also be set to other values, for example, <NUM>, <NUM> or <NUM>, etc..

Alternatively, in order to facilitate the target base station to know in which base station user data of the UE is transmitted, before acquiring the indication transmitted by the target base station, the method further includes: transmitting a handover request message to the target base station, where the handover request message may include: an identity of a small cell base station, or a cell identity of a small cell base station.

Alternatively, when or after receiving the handover acknowledge message transmitted by the target base station, the method may also include: transmitting, by the source base station, information to the small cell base station for stopping transmitting data to the UE; and after the UE access to the target base station, transmitting, by the source base station or the target base station, information to the small cell base station for continuing transmitting data to the UE.

Alternatively, after the UE accesses to the target base station, and before the source base station (or the target base station) transmits the information to the small cell base station for continuing transmitting data to the UE, the method may also include: acquiring a new NH and an NCC, and generating a new AS key according to the NH; and transmitting the new AS key, the NCC and an E-RAB ID to the small cell base station.

The acquiring the new NH and the NCC specifically includes: receiving the NH and the NCC transmitted by the target base station; or, initiatively acquiring the NH and the NCC from the target base station; where, the NH and the NCC are acquired by the target base station from an MME during a path selection.

Reference may also be made to <FIG> which is a third flow chart of a handover control method according to an embodiment of the present invention, the method includes:.

Alternatively, before step <NUM>, the method may also include: receiving a measurement report transmitted by a user equipment (UE); selecting a target base station for the UE according to the measurement report; transmitting a handover request to the target base station; acquiring configuration information of the target base station from the target base station.

Alternatively, the handover request message may include: an identity of a small cell base station or a cell identity of a small cell base station, but is not limited thereto.

Alternatively, when or after receiving the handover acknowledge message transmitted by the target base station, the method may also include: transmitting, by the source base station, information to the small cell base station for stopping transmitting data to the UE;
Alternatively, the method may also include: after the UE accesses to the target base station, transmitting, by the source base station or the target base station, information to the small cell base station for continuing transmitting data to the UE.

Alternatively, after the UE accesses to the target base station and before the source base station or the target base station transmits the information to the small cell base station for continuing transmitting data to the UE, the method may also include: acquiring a new NH and an NCC, and generating a new AS key according to the NH; and transmitting the new AS key, the NCC and an E-RAB ID to the small cell base station. The acquiring the new NH and the NCC specifically includes:
Receiving, by the source base station, the NH and the NCC transmitted by the target base station; or, acquiring, by the source base station, the NH and the NCC from the target base station initiatively; where, the NH and the NCC are acquired by the target base station from an MME during a path selection.

Reference may also be made to <FIG> which is a first flow chart of a resource control method according to an embodiment of the present invention, the method includes:.

In embodiments of the present invention, the target base station, after receiving the indication transmitted by the source base station, will not reserve resources used for data scheduling for a handover of the UE, thereby ensuring a normal communication for the UE during its handover procedure.

Reference may also be made to <FIG> which is a second flow chart of a resource control method according to an embodiment of the present invention, the method includes:.

In embodiments of the present invention, the target base station, after receiving the SN status transfer message carrying the indication, will release the resources used for data scheduling which are reserved for a handover of the UE, thereby ensuring that in a case where the user plane remains unchanged and the control plane is switched, a normal communication is ensured for the UE during its handover procedure.

Based on implementation procedures of the methods above, embodiments of the present invention also provide a handover control apparatus, and its first schematic structural diagram is as shown in <FIG>, the apparatus includes: a first transmitting unit <NUM>, a receiving unit <NUM> and a second transmitting unit <NUM>. The first transmitting unit <NUM> is configured to transmit indication to a target base station, where the indication includes: first indication indicating that a user plane for a user equipment (UE) remains unchanged, and a control plane for the UE is switched to the target base station; or second indication indicating that a control plane for the UE is switched to the target base station, and user data of the UE is transmitted by a small cell base station; or third indication indicating that both a user plane and a control plane for the UE are switched to the target base station; the receiving unit <NUM> is configured to receive a handover acknowledge message that is transmitted by the target base station in response to the indication; and the second transmitting unit <NUM> is configured to transmit a handover command to the UE, so as to indicate the UE to access to the target base station.

The apparatus may be a processor, where each internal unit may be implemented by a logic integrated circuit, and the processor is integrated in an eNodeB.

The first transmitting unit includes: a first indication transmitting unit and/or a first indication transmitting unit, where the first indication transmitting unit is configured to transmit the indication to the target base station via a handover request message; or, the second indication transmitting unit is configured to acquire the indication by negotiating with the target base station before transmitting the indication to the target base station.

Alternatively, the apparatus may also include: a third transmitting unit and a fourth transmitting unit, where the third transmitting unit is configured to transmit information to the small cell base station for stopping transmitting data to the UE when or after the receiving unit receives the handover acknowledge message transmitted by the target base station; and the fourth transmitting unit is configured to transmit information to the small cell base station for continuing transmitting data to the UE after the third transmitting unit transmits the information for stopping transmitting data to the UE and after the UE accesses to the target base station.

Alternatively, the apparatus may also include: an acquiring unit, a generating unit and a key transmitting unit, where the acquiring unit is configured to acquire a new NH and an NCC after the UE accesses to the target base station and before the fourth transmitting unit transmits the information for continuing transmitting data to the UE; the generating unit is configured to generate a new AS key according to the NH; and the key transmitting unit is configured to transmit the new AS key, the NCC and an E-RAB ID to the small cell base station.

Alternatively, the apparatus may be integrated in a base station, and may also be deployed in a network independently. Embodiments of the present invention will not make a limitation.

Reference may be made to corresponding implementation procedures in the methods described above for implementation procedures of functions and roles of all units in the apparatus, which will not be repeated herein.

Reference may also be made to <FIG> which is a second schematic structural diagram of a handover control apparatus according to an embodiment of the present invention, the apparatus includes: a first acquiring unit <NUM> and a first transmitting unit <NUM>, the first acquiring unit <NUM> is configured to acquire indication transmitted by a target base station, where the indication includes: first indication indicating that a user plane for a user equipment (UE) remains unchanged, and a control plane for the UE is switched to the target base station; or second indication indicating that a control plane for the UE is switched to the target base station, and user data of the UE is transmitted by a small cell base station; or third indication indicating that both a user plane and a control plane for the UE are switched to the target base station; and the first transmitting unit <NUM> is configured to transmit a handover command to the UE, so as to indicate the UE to access to the target base station.

The apparatus may be a processor, where each internal units may be implemented by a logic integrated circuit, and the processor is integrated in an eNodeB.

The first acquiring unit includes: a receiving unit and/or an initiative acquiring unit, the receiving unit is configured to receive a handover acknowledge message transmitted by the target base station in response to the handover request message of the source base station, where the handover acknowledge message includes the indication; the initiative acquiring unit is configured to initiatively acquire the indication from the target base station.

Alternatively, the apparatus may also include: a second transmitting unit and a third transmitting unit, the second transmitting unit is configured to transmit information to the small cell base station for stopping transmitting data to the UE before the first transmitting unit transmits the handover command to the UE; and the third transmitting unit is configured to transmit information to the small cell base station for continuing transmitting data to the UE after the second transmitting unit transmits the information for stopping transmitting data to the UE and after the UE accesses to the target base station.

Alternatively, the apparatus may also include: a second acquiring unit, a generating unit and a key transmitting unit, the second acquiring unit is configured to acquire a new NH and an NCC after the UE accesses to the target base station and before the third transmitting unit transmits the information for continuing transmitting data to the UE; the generating unit is configured to generate a new AS key according to the NH; and the key transmitting unit is configured to transmit the new AS key, the NCC and an E-RAB ID to the small cell base station.

Reference may also be made to <FIG> which is a third schematic structural diagram of a handover control apparatus according to an embodiment of the present invention, the apparatus includes: a first transmitting unit <NUM> and a second transmitting unit <NUM>, the first transmitting unit <NUM> is configured to transmit a handover command to a UE, so as to indicate the UE to access to a target base station; and the second transmitting unit <NUM> is configured to transmit a packet data convergence protocol (PDCP) sequence number (SN) status transfer message of the UE to the target base station, where the SN status transfer message includes: a UL COUNT Value and a DL COUNT Value, and values of the UL COUNT Value and the DL COUNT Value are set to <NUM>, so as to indicate that a control plane for the UE is switched to the target base station, and a user plane and data are transmitted by a small cell base station, so that the target base station releases a resource used for data scheduling which is reserved for a handover of the UE according to the SN status transfer message.

Alternatively, the apparatus may also include: a third transmitting unit and a fourth transmitting unit, the third transmitting unit is configured to transmit information to the small cell base station for stopping transmitting data to the UE before the first transmitting unit transmits the handover command to the UE; and the fourth transmitting unit is configured to transmit information to the small cell base station for continuing transmitting data to the UE after the third transmitting unit transmits the information for stopping transmitting data to the UE and after the UE accesses to the target base station.

Alternatively, the apparatus may also include: an acquiring unit, a generating unit and a key transmitting unit, the acquiring unit is configured to acquire a new NH and an NCC after the UE accesses the target base station and before the fourth transmitting unit transmits the information for continuing transmitting data to the UE; the generating unit is configured to generate a new AS key according to the NH; and the key transmitting unit is configured to transmit the new AS key, the NCC and an E-RAB ID to the small cell base station.

Reference may also be made to <FIG> which is a first schematic structural diagram of a resource control apparatus according to an embodiment of the present invention, the apparatus includes: a receiving unit <NUM> and a resource control unit <NUM>, the receiving unit <NUM> is configured to receive indication transmitted by a source base station, where the indication includes: first indication indicating that a user plane for a user equipment (UE) remains unchanged, and a control plane for the UE is switched to the target base station; or second indication indicating that a control plane for the UE is switched to the target base station, and user data of the UE is transmitted by a small cell base station; or third indication indicating that both a user plane and a control plane for the UE are switched to the target base station; and the resource control unit <NUM> is configured to omit an operation of reserving a resource used for data scheduling for a handover of the UE according to the indication, and prepare to provide a control plane service for the UE when the UE accesses to the target base station;
The apparatus may be a processor, where each internal unit may be implemented by a logic integrated circuit, and the processor is integrated in an eNodeB.

Reference may also be made to <FIG> which is a second schematic structural diagram of a resource control apparatus according to an embodiment of the present invention, the apparatus includes: a receiving unit <NUM> and a resource releasing unit <NUM>, the receiving unit <NUM> is configured to receive a packet data convergence protocol (PDCP) sequence number (SN) status transfer message of a UE transmitted by a source base station, where the SN status transfer message includes: a UL COUNT Value and a DL COUNT Value, and values of the UL COUNT Value and the DL COUNT Value are set to <NUM>, so as to indicate that a control plane for the UE is switched to the target base station, and a user plane and data are transmitted by a small cell base station; and the resource releasing unit <NUM> is configured to release a resource used for data scheduling which is reserved for a handover of the UE according to the SN status transfer message, and prepare to provide a control plane service for the UE when the UE accesses to the target base station. The apparatus may be a processor, where each internal unit may be implemented by a logic integrated circuit, and the processor is integrated in an eNodeB.

In order to facilitate persons skilled in the art to understood, specific application examples are described hereunder.

Reference may be made to <FIG> which is a flowchart of a first application example of a handover control method according to the present invention; in this embodiment, an example is taken where indication is carried in a request message, but is not limited thereto, the method specifically includes:.

Alternatively, it can be indicated by adding <NUM>-bit indication in the handover request message, certainly, a value of the indication may also be set to <NUM> or <NUM> to represent the indication indicating that the UP remains unchanged and the CP is switched, or that the CP is switched and all user data of the UE is transmitted by the small cell base station; or represent the third indication indicating that both the user plane and the control plane are switched. Certainly, a value of the indication may also be set to other values, the values can be set arbitrarily according to needs, for example, <NUM> or <NUM>, etc., and this embodiment will not make a limitation.

Alternatively, the handover request message may also include: an identity of a small cell base station (Pico), and/or a cell identity (Cell ID) of a Pico, and/or include indication indicating that the control plane for the UE is separated from the user plane.

Step <NUM>, performing, by the target eNodeB, an admission control after receiving the handover request message transmitted by the source base station; i.e. the target eNodeB does not reserve a resource used for service scheduling for a handover of the UE.

Step <NUM>, transmitting, by the target eNodeB, a handover acknowledge message to the source eNodeB;
Alternatively, when or after receiving the handover acknowledge message transmitted by the target base station, the source base station or the target base station may transmit a message to the Pico, where the message includes information for stopping transmitting data to the UE; specifically, the information may include an identity of the UE to represent stopping all data transfer related to the UE, or may include information about a data radio bearer (data radio bear, DRB) of the UE transmitted by the Pico. The data radio bearer (data radio bear, DRB) specifically includes one or more of the following, but is not just limited to: an E-RAB ID (E-UTRAN Radio Access Bearer ID, an E-UTRAN Radio Access Bearer ID), a Transport Layer Address (Transport Layer Address), a GTP-TEID (GTP Tunneling Protocol -Tunnel Endpoint Identifier, GTP Protocol-Tunnel UE Identifier).

Step <NUM>, transmitting, by the source eNodeB, a handover command message to the UE so as to indicate the UE to initiate a random access to the target base station;
After step <NUM>, the prior art also requires to perform step A: transmitting, by the source eNodeB, an SN status transfer message to the target base station to inform the target base station of uplink PDCPSN reception status (uplink PDCP SN receiver status) and downlink PDCPSN (the downlink PDCP SN transmitter status) of the UE, so that the target base station knows data transfer status of the current UE.

While in this embodiment, after step <NUM>, there is no need to perform step A, this is because, in step <NUM>, the source base station has informed the target base station of the indication via the handover request message, there is no need to switch the UP, the target base station, after receiving the indication, agrees this type of handover and switch the UE to the target cell. Thus, in embodiments of the present invention, the target base station does not need to know data reception situation of the UE, and will be clear about start number of forwarded data.

Step <NUM>, initiating, by the UE, an access to the target eNodeB after receiving the handover command message, and accessing to the target base station;
Where, a procedure for the UE to access to the target eNodeB is: transmitting, by the UE, a random access preamble to the target eNodeB. The specific access procedure is well-known techniques for persons skilled in the art, and will not be repeated herein.

Step <NUM>, transmitting, by the target eNodeB, a random access response message to the UE;
Step <NUM>, transmitting, by the UE, a handover complete message to the target eNB.

Alternatively, if an optional step after step <NUM> is performed, then after step <NUM>, i.e. after the UE completes the handover, the source/target base station transmits information to the small cell base station (Pico) for continuing transmitting data to the UE; specifically, the information includes: an identifier of the UE which is provided to indicate the service belongs to which terminal, or provided information about a data radio bearer (data radio bear, DRB) of the UE. The data radio bearer (data radio bear, DRB) specifically includes one or more of the following, but is not just limited to: an E-RAB ID (E-UTRAN Radio Access Bearer ID, an E-UTRAN Radio Access Bearer ID), a Transport Layer Address (Transport Layer Address), a GTP-TEID (GTP Tunneling Protocol -Tunnel Endpoint Identifier, GTP Protocol-Tunnel UE Identifier).

Certainly, the transmitting the information to the Pico for continuing transmitting data to the UE is not limited to be performed after this step, and may be performed after any one of steps after this step, for example, after step <NUM> and before the step of requesting a path selection, certainly, the transmitting the information to the Pico for continuing transmitting data to the UE may also be performed after the NCC and the new NH are acquired, this embodiment will not make a limitation.

Alternatively, after the UE accesses to the target base station, and before the information for continuing transmitting data to the UE is transmitted to the small cell base station, the embodiments may include: acquiring, by the target base station, a new NH and an NCC from an MME side, and generating a new AS key according to the NH; and transmitting the new AS key, the NCC and an E-RAB ID to the small cell base station.

That is to say, in a path switch process (path switch process) of the UE, since the UP of the UE remains unchanged at this time, it does not need to notify a gateway to change a data transfer target. However, since this process also includes acquiring a new NH and an NCC at the MME side by the target base station, the target eNB can initiate an intra-cell handover procedure immediately after a handover is completed, and uses the new NH to generate the new AS key. Thus, the small cell base station (Pico) needs to acquire a new NH and an NCC to perform data transfer, which specifically includes:.

Although downlink transport point address (Transport layer address) is still the transport point address of the Pico providing data transfer for the UE, the MME also provides a new NCC and a new NH for the target base station.

Alternatively, parallel to <NUM>), or after <NUM>), the method may also include: transmitting, by the target eNodeB, a message to the Pico to provide a new NCC and a new NH; furthermore, in order to identify that the service belongs to which UE, an E-RAB ID also needs to be provided particularly.

Reference may also be made to <FIG> which is a flowchart of a second application example of a handover control method according to the present invention; in this embodiment, an example is taken where indication indicating that a UE remains unchanged and a CP is switched is carried in a handover acknowledge message transmitted by a target base station to a source base station, but is not limited thereto, the method specifically includes:.

That is to say, the indication is added in the handover request message to indicate that the UP remains unchanged and the CP is switched.

Alternatively, it can be indicated by adding <NUM>-bit indication in the handover acknowledge message, certainly, a value of the indication may also be set to <NUM> or <NUM> to represent the first indication indicating that the UP remains unchanged and the CP is switched, or represent the second indication indicating that the CP is switched and all user data of the UE is transmitted by the small cell base station; or represent the third indication indicating that both the user plane and the control plane are switched. Certainly, a value of the indication may also be set to other values, the values can be set arbitrarily according to needs, for example, <NUM> or <NUM>, etc., and this embodiment will not make a limitation, as long as values of the three types of indication are set different from each other, it will be fine.

Alternatively, when or after receiving the handover acknowledge message transmitted by the target base station, the source base station or the target base station may transmit a message to the Pico, where the message includes information for stopping transmitting data to the UE; specifically, the information may include an identity of the UE to represent stopping all data transfer related to the UE, or may include information about a data radio bearer (data radio bear, DRB) of the UE transmitted by the Pico. The data radio bearer (data radio bear, DRB) specifically includes one or more of the following, but is not just limited to: an E-RAB ID (E-UTRAN Radio Access Bearer ID, an E-UTRAN Radio Access Bearer ID), a Transport Layer Address (Transport Layer Address), a GTP-TEID (GTP Tunneling Protocol -Tunnel Endpoint Identifier, GTP Protocol-Tunnel UE Identifier).

Step <NUM>, transmitting, by the source eNodeB, a handover command message to the UE to indicate the UE to initiate a random access to the target base station;
Step <NUM>, initiating, by the UE, an access to the target eNodeB after receiving the handover command message, and accessing to the target base station;.

Reference may be made to the embodiments described above for the access procedure, which will not be repeated herein.

Step <NUM>, transmitting, by the target eNodeB, a random access response message to the UE;
Step <NUM>, transmitting, by the UE, a handover complete message to the target eNodeB.

Certainly, the transmitting the information for continuing transmitting data to the UE is not limited to be performed after this step, and may be performed after any one of steps after this step, for example, after step <NUM> and before the step of requesting a path selection, certainly, the transmitting the information to the Pico for continuing transmitting data to the UE may also be performed after the NCC and the new NH are acquired, this embodiment will not make a limitation.

Reference may be made to the procedures as described in <FIG> for subsequent procedures of this embodiment, which will not be repeated herein.

Reference may also be made to <FIG> which is a flowchart of a third application example of a handover control method according to the present invention; in this embodiment, an example is taken where indication indicating that a UE remains unchanged and a CP is switched is carried in a packet data convergence protocol (PDCP) sequence number (SN) status transfer message of the UE transmitted by a source eNodeB to a target eNodeB, but is not limited thereto, the method specifically includes:.

Alternatively, the handover request message may also include: an identity of a small cell base station (Pico) and a cell identity (Cell ID) of the Pico, or a cell identity (Cell ID) of Pico, or also include one or more of indication indicating that the control plane for the UE is separated from the user plane.

A COUNT Value is:
This information element indicates the <NUM> bit PDCP sequence number and the corresponding <NUM> bit Hyper frame number.

Step <NUM>, receiving, by the target base station, the SN status transfer message of the source base station, since indication is carried in the message, then, releasing, by the target base station, a resource used for data scheduling which is reserved for the switched UE.

Step <NUM>, after step <NUM>, i.e. after receiving the handover command message, initiating, by the UE, an access to the target eNodeB, and accessing to the target base station.

In embodiments of the present invention, a source base station transmits indication to a target base station, so that the target base station, after acquiring the indication, does not reserve resources used for data scheduling for a handover of the UE, or release resources used for data scheduling which are reserved for a handover of the UE. Therefore, in a case where a user plane remains unchanged and a control plane is switched, a normal communication is ensured for the UE during its handover.

In embodiments of the present invention, a UE may be any one of the following, it may be stationary, and may also be mobile, a stationary UE may specifically include: a terminal (terminal), a mobile station (mobile station), a subscriber unit (subscriber unit), a station (station), or the like; a mobile UE may specifically include: a cellular phone (cellular phone), a personal digital assistant (PDA, personal digital assistant), a wireless modem (modem), a wireless communication device, a handheld (handheld) device, a laptop computer (laptop computer), a cordless phone (cordless phone), a wireless local loop (WLL, wireless local loop) station, or the like, the UEs described above may be distributed through the overall wireless network.

In order to facilitate the understanding of persons skilled in the art, specific application examples are described hereunder. It should be noted that, in this embodiment, a mobility management network element can be any one of an MME (Mobility Management Entity, mobility management entity) and an SGSN (Serving GPRS Support Node, serving GPRS support node). For convenience of descriptions, specific illustrations are made by taking the mobility management network element in the following application examples as the MME.

It should be noted that, in the description herein, the terms like "first" and "second" are used to differentiate one entity or operation from another, but is not necessarily construed as any practical relationship or order between the entities or operations. Moreover, the terms "include", "comprise" and any variation thereof refer to "including but not limited to". Therefore, in the context of a process, method, object or device that includes a series of elements, the process, method, object or device not only includes such elements, but also includes other elements not specified explicitly, or may include inherent elements of the process, method, object or device. Unless otherwise specified, in the context of "include" or "comprise", the process, method, object or device that includes or comprises the specified elements may include other identical elements.

Claim 1:
A handover control method, comprising:
receiving (<NUM>), by a target base station, a handover request message from a source base station, wherein the handover request message comprises an identity of a small cell base station or a cell identity of the small cell base station; and
transmitting (<NUM>), by the target base station, a handover acknowledge message to the source base station, wherein the handover acknowledge message comprises indication that occupies a bit, a value of the indication being used to represent that user data of an user equipment, UE, continues to be transmitted by the small cell base station after the UE accessing the target base station, wherein the target base station provides a control plane service for the UE.