CN106604335B - Cell switching method - Google Patents

Abstract

The invention discloses a method for switching cells, which comprises the following steps: the source base station reserves a special random access resource for the user equipment and configures the reserved special random access resource to the user equipment; after the user equipment is switched to the target base station, the target base station does not request a core network to switch a downlink GTP tunnel within the preset waiting time; when the user equipment needs to be switched back to the source base station, the user equipment initiates random access by using the stored special random access preamble, synchronizes the random access to the source base station and switches back to the source base station; and after the user equipment is switched back to the source base station, the source base station releases the reserved special random access resource, performs admission control and configures the allocated wireless resource information to the user equipment. By using the cell switching method provided by the invention, the switching time delay can be reduced, the risk of UE call drop in the switching process can be reduced, and the signaling processing overhead of a base station and a core network can be reduced.

Description

A method of cell handover

technical field

The present invention relates to the technical field of wireless communication, and in particular, to a method for cell handover.

Background technique

In order to ensure the service continuity of the user equipment (UE) in the radio resource control (RRC) connected state RRC_CONNECTED, the long-term evolution (LTE) system adopts the network-controlled UE-assisted method to perform cell handover. The entire handover process includes three stages: handover preparation, handover execution, and handover completion. The specific switching process is as follows:

In the handover preparation stage, the source base station (for example, the base station in the LTE system is an evolved Node B) makes a handover decision, and selects a handover candidate cell; the source base station interacts with the target base station to which the handover candidate cell belongs, and obtains the information prepared by the target base station for the UE Switch resources.

In the handover execution stage, the source base station sends a handover command to the UE, instructing the UE to hand over to the designated target cell (ie, the handover candidate cell); the source base station performs data back transmission; the UE successfully accesses the target cell and establishes uplink synchronization, and sends the data to the target base station. A handover confirmation is sent, and the handover completion phase is performed.

In the handover completion stage, the target base station interacts with the core network to complete the downlink General Packet Tunneling Protocol (GTP) tunnel conversion; the target base station sends the fronthaul and newly received data in sequence, and releases the UE context of the source base station. The GTP tunnel refers to a communication tunnel between two GTP nodes, and is used to divide services into different communication flows. GTP tunnels are identified by a Tunnel Endpoint Identifier (TEID), an Internet Internet Protocol (IP) address, and a User Datagram Protocol (UDP) port number; carrying the encapsulation between a given pair of GTP user plane GTP-U tunnel endpoints Transport Protocol Data Units (T-PDUs) and signaling messages.

FIG. 1 is a schematic diagram of a macro-micro heterogeneous network scenario in the prior art. In the macro-micro heterogeneous network scenario shown in FIG. 1 , the UE moves between the macro base station and the micro base station, and the coverage of the micro base station is much smaller than that of the macro base station. When the UE is handed over from the macro base station to the micro base station, in the existing handover method, after the UE reports the measurement report, it needs to go through two stages of handover preparation and handover execution to establish an air interface connection with the target cell. The risk of dropped calls; in addition, when the UE switches from the macro base station to the micro base station and then back to the macro base station in a short time, the traditional handover process requires two downlink GTP tunnel conversions, which increases the signaling between the base station and the core network. processing overhead.

SUMMARY OF THE INVENTION

In view of this, the present invention provides a method for cell handover, which can reduce the handover delay, reduce the risk of UE dropped calls during the handover process, and also reduce the signaling processing overhead of the base station and the core network.

The technical scheme of the present invention is specifically realized in this way:

A method for cell handover, the method comprising:

The source base station reserves dedicated random access resources for the user equipment, and configures the reserved dedicated random access resources to the user equipment; the dedicated random access resources include: a random access preamble and the preset random access resources Lead time of life;

After the user equipment is switched to the target base station, the target base station does not request the core network to convert the downlink general packet radio service tunneling protocol GTP tunnel within the preset waiting time;

When the user equipment needs to switch back to the source base station, the user equipment initiates random access using the saved dedicated random access preamble, synchronizes with the source base station, and switches back to the source base station;

After the user equipment switches back to the source base station, the source base station releases the reserved dedicated random access resources, performs admission control, and configures the allocated radio resource information to the user equipment.

Preferably, the source base station reserving dedicated random access resources for the user equipment includes:

The source base station reserves the random access preamble for the user equipment, and presets the life time of the reserved random access preamble; sets and starts a first timer whose duration is the life time.

Preferably, the source base station sends a radio resource control connection reconfiguration message to the user equipment;

The radio resource control connection reconfiguration message carries a handover command and a dedicated random access resource configured for the user equipment.

Preferably, the method further includes:

the user equipment saves the reserved dedicated random access resource, and starts a second timer whose duration is the lifetime;

When the second timer expires, the user equipment clears the reserved reserved dedicated random access resources.

Preferably, the target base station does not request the core network to convert the downlink GTP tunnel within the preset waiting time, including:

The target base station starts the third timer of the preset time; or, the target base station determines whether to start the third timer of the preset time according to the base station type, and if the target base station is a micro base station, the target base station starts the preset time a third timer of time;

If the user equipment switches from the target base station to the source base station, the target base station stops the third timer;

If the user equipment is still at the target base station, when the third timer expires, for X2 handover, the target base station sends a path switch message to the mobility management entity; for S1 handover, the target base station sends a path switch message to the mobile The sex management entity sends a handover notification message.

Preferably, when the user equipment determines that it needs to switch back to the source base station, the user equipment sends a handover instruction message to the target base station; the target base station stops the third timer;

Or, when the user equipment determines that it needs to be handed back to the source base station, if the user equipment does not send the handover instruction message, the target base station determines whether the user equipment initiates handover to the source base station by detecting the data transmission situation of the air interface.

Preferably, for X2 handover, when the user equipment does not decide to switch back to the source base station within the preset time, the life time of the random access resources reserved by the source base station ends, and the source base station releases the reserved random access resources;

The target base station determines whether the third timer times out;

When the third timer times out, the target base station sends a path switch request message to the mobility management entity, requesting the downlink GTP tunnel to switch to a new GTP tunnel endpoint;

Mobility management entity, service gateway and packet data gateway realize the conversion of downlink GTP tunnel to a new GTP tunnel endpoint by modifying the bearer process;

The serving gateway sends an end marker packet to the source base station, and forwards it to the target base station through the source base station, indicating the end of data forwarding;

The mobility management entity sends a path switching request response message to the target base station to confirm that the path switching is successful;

The target base station sends a user equipment uplink release message to the source base station to release resources.

Preferably, for S1 handover, when the user equipment does not decide that it needs to be handed back to the source base station within the preset time, the life time of the random access resources reserved by the source base station ends, and the source base station releases the reserved random access resources;

The target base station determines whether the third timer times out;

When the third timer times out, the target base station sends a handover notification message to the mobility management entity, indicating that the user equipment has been handed over to the target cell and the S1 handover is successfully completed;

The mobility management entity, the first serving gateway and the second serving gateway realize the conversion of the downlink GTP tunnel to a new GTP tunnel endpoint by modifying the bearer process;

When one of the conditions listed in "Trigger tracking area update" is satisfied, the user equipment initiates the tracking area update process;

The mobility management entity releases the logical connection associated with the target base station and the user equipment through the user equipment context release process.

As can be seen above, in the cell handover method provided by the present invention, when the user equipment is handed over from the source base station (or macro base station) to the target base station (or micro base station), the source base station reserves dedicated random access resources for the user equipment (including: random access preamble and its preset lifetime), and configure it to the user equipment, so that when the user equipment moves from the target base station back to the source base station, it can use the reserved random access resources to achieve fast handover. Through the above method of reserving random access resources for the UE and controlling the handover of the UE, the time for measurement report reporting, handover preparation and handover command issuance is saved, the handover delay is reduced, and the call drop of the UE during the handover process is reduced. Moreover, after the user equipment switches to the target base station, the target base station does not request the core network to switch the downlink GTP tunnel within the preset waiting time, so as to prevent the user equipment from performing GTP twice when switching back to the source base station in a short time. Tunnel conversion processing greatly reduces the signaling processing overhead of the base station and the core network.

Description of drawings

FIG. 1 is a schematic diagram of a macro-micro heterogeneous network scenario in the prior art.

FIG. 2 is a schematic diagram of an overall flow of a method for cell handover in an embodiment of the present invention.

FIG. 3 is a schematic flowchart of a method for cell handover in Embodiment 1 of the present invention.

FIG. 4 is a schematic flowchart of a method for cell handover in Embodiment 2 of the present invention.

FIG. 5 is a schematic flowchart of a method for cell handover in Embodiment 3 of the present invention.

FIG. 6 is a schematic flowchart of a method for cell handover in Embodiment 4 of the present invention.

FIG. 7 is a schematic flowchart of a method for cell handover in Embodiment 5 of the present invention.

FIG. 8 is a schematic diagram of a reserved random access preamble configuration process in an embodiment of the present invention.

FIG. 9 is a schematic diagram of path conversion processing in an embodiment of the present invention.

FIG. 10 is a schematic diagram of handover notification processing in an embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

This embodiment provides a method for cell handover.

FIG. 2 is a schematic flowchart of a method for cell handover in an embodiment of the present invention. As shown in FIG. 2 , the method for cell handover in the embodiment of the present invention mainly includes the following steps:

Step 101, the source base station reserves dedicated random access resources for the user equipment, and configures the reserved dedicated random access resources to the user equipment.

Before the user equipment performs handover, the source base station can reserve dedicated random access resources for the user equipment, and configure the dedicated random access resources to the user equipment.

In addition, preferably, in a specific embodiment of the present invention, the dedicated random access resource includes: a random access preamble and a preset life time of the random access preamble.

In addition, preferably, in a specific embodiment of the present invention, the dedicated random access resource can be configured to the user equipment through a radio resource control connection reconfiguration message.

For example, as shown in FIG. 8 , the source base station sends a RRC connection reconfiguration message to the user equipment, and the RRC connection reconfiguration message carries a handover command and a dedicated random access resource ( the random access preamble and the lifetime of the random access preamble).

Further, in a preferred embodiment of the present invention, after the dedicated random access resource is configured to the user equipment, the user equipment can save the reserved dedicated random access resource, and start a time with a duration of life time. the second timer. When the second timer expires, the user equipment will clear the reserved reserved dedicated random access resources.

Step 102, after the user equipment is handed over to the target base station, the target base station does not request the core network to switch the downlink GTP tunnel (ie, does not request the core network to switch the user plane path) within a preset waiting time.

In the technical solution of the present invention, when the handover command is configured to the user equipment, the user equipment can perform handover to the target base station.

However, after the user equipment is switched to the target base station, the target base station does not request the core network to switch the downlink GTP tunnel within the preset waiting time.

In the technical solution of the present invention, the duration of the above-mentioned waiting time can be preset according to the needs of the actual application. For example, it can be considered that the duration of the above-mentioned waiting time is preset to be equal to or less than the life time of the random access preamble preset in the source base station in step 101; of course, it can also be considered that the duration of the above-mentioned waiting time is preset to be greater than the above life time.

In addition, in the technical solution of the present invention, the above-mentioned step 102 can be implemented in various ways. The following will take one of the implementation manners as an example to introduce the technical solution of the present invention.

For example, preferably, in a specific embodiment of the present invention, the target base station does not request the core network to convert the downlink GTP tunnel within a preset waiting time, which may include:

The target base station starts a third timer for a preset time; or, the target base station determines whether to start a third timer for a preset time according to the base station type, and if the target base station is a micro base station, the target base station starts a third timer for preset time;

If the user equipment switches from the target base station to the source base station, the target base station stops the third timer;

If the user equipment is still at the target base station, when the third timer expires, for X2 handover, the target base station sends a path switch message to the mobility management entity; for S1 handover, the target base station sends a path switch message to the mobile The sex management entity sends a handover notification message.

In addition, preferably, in the specific embodiment of the present invention, when the user equipment determines that it needs to be handed back to the source base station, the user equipment sends a handover instruction message to the target base station. At this time, the target base station will stop the third timer.

Alternatively, when the user equipment determines that it needs to be handed back to the source base station, if the user equipment does not send the above handover instruction message, the target base station can determine whether the user equipment initiates handover to the source base station by detecting the data transmission situation of the air interface. For example, if the target base station no longer receives uplink data from the user equipment, and the downlink data cannot reach the user equipment, it can be determined that the user equipment initiates handover to the source base station at this time.

In addition, preferably, in a specific embodiment of the present invention, the handover indication message may be a dedicated indication message, or may be a measurement report message carrying indication information.

Step 103, when the user equipment needs to switch back to the source base station, the user equipment initiates random access by using the saved dedicated random access preamble, synchronizes with the source base station, and switches back to the source base station.

Step 104, after the user equipment is switched back to the source base station, the source base station releases the reserved dedicated random access resources, performs admission control, and configures the allocated radio resource information to the user equipment.

For example, preferably, in a specific embodiment of the present invention, the source base station may configure information such as the allocated radio resources to the user equipment through the radio resource control connection reconfiguration process.

In addition, in the technical solution of the present invention, the radio resource connection reconfiguration (RRCConnectionReconfiguration) message in the above-mentioned RRC connection reconfiguration process can carry a lot of information, for example, information such as measurement configuration, mobility control, and radio resource configuration information. . The base station may configure part or all of the specified information to the user equipment according to the actual situation. Therefore, further, in this step 104, the base station can configure only the allocated radio resource information for the user equipment through the radio resource connection reconfiguration message, and can also combine the information related to the radio resource configuration, measurement configuration and mobility control into one. and configure it to the user device.

Through the above steps 101 to 104, the cell handover of the user equipment can be realized, and the user equipment that has been handed over to the target base station can use the reserved random access resources within a preset time to quickly switch back to the source The base station saves the time for measurement report reporting, handover preparation and handover command issuance, reduces the handover delay, reduces the risk of UE dropping calls during the handover process, and prevents the user equipment from switching back to the source in a short time. The base station performs two GTP tunnel conversion processing to reduce the signaling processing overhead between the base station and the core network.

The technical solutions of the present invention will be described in detail below by taking several specific embodiments as examples.

Embodiment 1: An implementation manner of switching back to the source base station within a preset time during handover based on X2.

3 is a schematic flowchart of a method for cell handover according to Embodiment 1 of the present invention, wherein the source base station is a macro base station, and the target base station is a micro base station. As shown in FIG. 3 , the method for cell handover in the first embodiment may include the following steps:

Step 201, the source base station interacts with the target base station to obtain the resources required for handover.

In this step 201, the source base station will prepare for handover with the target base station. Therefore, the source base station will interact with the target base station to obtain the resources required for handover. For example, the source base station interacts with the target base station to which the handover candidate cell belongs, and obtains handover resources prepared by the target base station for the UE.

Step 202, the source base station reserves random access resources for the user equipment, including the random access preamble and the reserved life time of the random access preamble; and sets and starts a first timer whose duration is the life time.

In addition, in a subsequent step, when the first timer expires, the source base station will release the random access resource reserved for the user equipment.

Step 203, the source base station configures the handover command and the reserved random access resources to the user equipment through the radio resource control connection reconfiguration message; the user equipment saves the reserved random access preamble and its life time, and the activation time is the life time the second timer.

In the above step 202, the source base station starts a timer (ie, the first timer), and in step 203, the user equipment also starts a timer (ie, the second timer). The duration of these two timers is the preset life time. The source base station and the user equipment jointly maintain the reserved random access resources by starting a timer respectively. For example: when the life of the random access resource (that is, the random access preamble) reserved by the source base station ends (that is, the first timer expires), the source base station can allocate the random access resource to other user equipments for use; and When the second timer of the user equipment expires, the user equipment discards the reserved reserved random access resources (ie, the random access preamble).

Step 204, the source base station sends a sequence number state transfer message to the target base station to migrate the uplink and downlink Packet Data Convergence Protocol (PDCP) sequence number and super frame number (HFN) during switching; the received downlink data from the serving gateway (S-GW) forwarded to the target base station;

Step 205, the user equipment performs handover to the target base station.

The specific implementation manner of the handover is as follows: the user equipment synchronizes with the target base station, and then guides the target base station to perform non-contention-based random access with the random access preamble carried in the handover command, and sends a radio resource control connection reconfiguration to the target base station. Completion (handover confirmation) message.

Step 206, the target base station starts a third timer with a preset duration.

In this step, the target base station may start a third timer, and the duration of the third timer may be preset according to actual application requirements. For example, preferably, in a specific embodiment of the present invention, the duration of the third timer may be set to the preset life time. Of course, other values can also be set.

Step 207, optionally, when the user equipment determines within a preset time (for example, before the first timer expires) that it needs to switch back to the source base station, the user equipment sends a handover instruction message (for example, this The handover indication message may also be a measurement report carrying indication information); or, if the user equipment does not send the above handover indication message, the target base station can determine whether the user equipment initiates a handover to the source base station by detecting the data transmission situation of the air interface.

Preferably, the specific implementation is as follows: if the target base station no longer receives uplink data from the user equipment, and the downlink data cannot reach the user equipment, it can be determined that the user equipment initiates handover to the source base station at this time.

Step 208, the target base station stops the third timer, and sends a sequence number state transition message to the source base station, instructing to stop forwarding data to the target base station.

Step 209, the user equipment performs random access using the reserved random access preamble, switches back to the source base station, and sends a radio resource control connection reconfiguration complete (handover confirmation) message to the source base station.

Step 210, the source base station stops the first timer and releases the dedicated random access resources reserved for the user equipment.

In steps 211 to 213, the source base station performs admission control and air interface reconfiguration.

For example, a specific implementation manner is as follows: the source base station performs admission control and allocates radio resources; and then configures the allocated radio resource information to the user equipment through the radio resource control connection reconfiguration process.

Step 214, the source base station sends a user equipment context release message to the target base station to release the resources allocated by the target base station for the user equipment.

Through the above steps 201 to 214, the processing method of switching back to the source base station within the preset time during the X2-based switching can be implemented.

Embodiment 2: An implementation manner of not switching back to the source base station within a preset time during handover based on X2.

4 is a schematic flowchart of a method for cell handover in Embodiment 2 of the present invention, wherein the source base station is a macro base station, and the target base station is a micro base station. As shown in FIG. 4 , the method for cell handover in the second embodiment may include the following steps:

Steps 301 to 306 are the same as steps 201 to 206 of the first embodiment, and are not described again here.

Step 307, when the user equipment does not decide within a preset time (for example, before the first timer expires) that it needs to switch back to the source base station, the life time of the random access resources reserved by the source base station ends, and the source base station is deactivated. Reserved random access resources.

Step 308, the target base station determines whether the third timer has timed out.

When the third timer times out, step 309 can be executed.

Step 309, when the third timer expires, the target base station sends a path switching request message to the mobility management entity, requesting that the downlink GTP tunnel be switched to a new GTP tunnel endpoint.

In steps 310 to 313, the mobility management entity, the serving gateway and the packet data gateway realize the conversion of the downlink GTP tunnel to a new GTP tunnel endpoint by modifying the bearer process.

Step 314, the serving gateway sends an end marker packet to the source base station, and forwards the packet to the target base station through the source base station, indicating the end of data forwarding.

Step 315: The mobility management entity sends a path switching request response message to the target base station to confirm that the path switching is successful.

Step 316, the target base station sends a user equipment uplink release message to the source base station to release resources.

Through the above steps 301 to 316, the processing method when the handover based on X2 is not switched back to the source base station within the preset time can be realized.

Embodiment 3: An implementation manner of switching back to the source base station within a preset time during handover based on S1.

5 is a schematic flowchart of a method for cell handover according to Embodiment 3 of the present invention, wherein the source base station is a macro base station, and the target base station is a micro base station. As shown in FIG. 5 , the method for cell handover in Embodiment 3 may include the following steps:

Step 401, the source base station interacts with the target base station to obtain the resources required for handover

In this step 401, the source base station will prepare for handover with the target base station. For example, the source base station will interact with the target base station through the mobility management entity to obtain the resources required for handover.

Step 402, the source base station reserves the random access preamble for the user equipment, and presets the life time of the reserved random access preamble; sets and starts a first timer whose duration is the life time.

Step 403, the source base station sends the handover command, the reserved random access preamble and the life time of the random access preamble to the user equipment through the radio resource control connection reconfiguration message; the user equipment saves the reserved random access preamble and its life time, and start a second timer whose duration is the life time.

In steps 404 to 405, data reverse transmission is performed.

For example, preferably, in a specific embodiment of the present invention, the specific implementation of the data back transmission is:

The source base station sends a base station state transfer message to the mobility management entity to transfer the PDCP sequence number receiving and sending states;

The mobility management entity sends a mobility management entity state transfer message to the target base station, and transfers the PDCP sequence number receiving and sending states;

The source base station transmits the downlink data from the S-GW back to the target base station.

Step 406, after the user equipment performs handover to the target base station and the handover is successful, it sends a radio resource control connection reconfiguration complete (handover confirmation) message to the target base station.

Step 407, the target base station starts a third timer for a preset time.

Step 408 is the same as step 207 in the first embodiment, and is not repeated here.

In steps 409 to 410, the target base station stops the third timer and sends a base station state transition message to the mobility management entity; the mobility management entity sends a mobility management entity state transition message to the source base station, instructing to stop forwarding data to the target base station.

Step 411, the user equipment performs random access using the reserved random access preamble, switches back to the source base station, and sends a radio resource control connection reconfiguration complete (handover confirmation) message to the source base station.

Step 412, the source base station stops the first timer and releases the dedicated random access resources reserved for the user equipment.

Step 413, the source base station performs admission control and air interface reconfiguration.

The step 413 is the same as the steps 211 to 213 in the first embodiment, and details are not repeated here.

Step 414: Release the logical connection associated with the target base station and the user equipment through the user equipment context release process.

Through the above-mentioned steps 401 to 414, the processing method of switching back to the source base station within the preset time during the handover based on S1 can be realized.

Embodiment 4: An implementation manner of not switching back to the source base station within a preset time during handover based on S1.

FIG. 6 is a schematic flowchart of a method for cell handover in Embodiment 4 of the present invention. As shown in FIG. 6 , the method for cell handover in Embodiment 4 may include the following steps:

Steps 501 to 507 are the same as steps 401 to 407 of the first embodiment, and are not repeated here.

Step 508, when the user equipment does not decide within a preset time (for example, before the first timer expires) that it needs to switch back to the source base station, the life time of the random access preamble reserved by the source base station ends, and the source base station is deactivated. Reserved random access resources.

Step 509, the target base station determines whether the third timer has timed out.

Step 510, when the third timer expires, the target base station sends a handover notification message to the mobility management entity, indicating that the user equipment has been handed over to the target cell and the S1 handover is successfully completed.

In steps 511 to 514, the mobility management entity, the first serving gateway and the second serving gateway implement the conversion of the downlink GTP tunnel to a new GTP tunnel endpoint by modifying the bearer process.

Step 515 , when one of the conditions listed in "Trigger Tracking Area Update" is satisfied, the user equipment initiates a tracking area update process.

In steps 516 to 517, the mobility management entity releases the logical connection associated with the target base station and the user equipment through the user equipment context release process.

For example, preferably, in the specific embodiment of the present invention, the specific implementation manner is:

The mobility management entity sends a user equipment uplink release command message to the target base station;

The target base station releases the logical connection associated with the user equipment, and replies the user equipment context release complete message to the mobility management entity.

Through the above-mentioned steps 501 to 517 , the processing method when the handover is not performed back to the source base station within the preset time during the handover based on S1 can be realized.

Embodiment 5: When handover is based on X2, the user equipment is handed over from the source base station to the target base station, and the target base station receives the measurement report of the user equipment when the third timer expires and switches back to the source base station.

FIG. 7 is a schematic flowchart of a method for cell handover according to Embodiment 5 of the present invention, wherein the source base station is a macro base station, and the target base station is a micro base station. As shown in FIG. 7 , the method for cell handover in the fifth embodiment may include the following steps:

Steps 601 to 606 (not shown in FIG. 7 ) are the same as steps 201 to 206 of the first embodiment, and are not described again here.

Step 607, the third timer of the target base station times out.

Step 608, the user equipment sends a measurement report to the target base station.

Step 609, the target base station makes a handover decision, and the decision result is that the user equipment is handed back to the source base station; the target base station and the source base station obtain handover resources through interaction.

Step 610, the target base station sends a radio resource control connection reconfiguration message to the user equipment, which carries a handover command.

Step 611, the target base station sends a sequence number state transfer message to the source base station, carrying the uplink and downlink PDCP sequence numbers and HFN state.

Step 612, the user equipment initiates random access to the source base station and establishes uplink synchronization, and then replies to the source base station with a radio resource control connection reconfiguration complete message carrying a handover confirmation.

Step 613, the source base station sends a user equipment uplink release message to the target base station; the target base station releases resources.

In addition, in the technical solution of the present invention, when the user equipment is handed over based on S1, the user equipment is handed over from the source base station to the target base station, and the target base station receives the measurement report of the user equipment when the third timer expires. The processing methods based on X2 handover in the above-mentioned Embodiment 5 are similar, and the differences are:

During handover preparation, the target base station interacts with the source base station to obtain handover resources through the mobility management entity, as shown in the above step 401;

When performing data reverse transmission, the target base station forwards the state transfer message to the source base station through the mobility management entity, as shown in the above steps 409 to 410;

When releasing the resources of the user equipment in the target base station, the mobility management entity is used to notify the target base station to release the resources, as shown in step 414 above.

In addition, preferably, FIG. 8 is a schematic diagram of a reserved random access preamble configuration process in an embodiment of the present invention. As shown in step 701 in FIG. 8 , in a specific embodiment of the present invention, the source base station sends wireless A resource control connection reconfiguration message, the radio resource control connection reconfiguration message carries a handover command and a dedicated random access resource configured for the user equipment (random access preamble and the life time of the random access preamble) .

In addition, in the technical solution of the present invention, steps 306 , 308 , 309 and 315 may also have multiple implementations.

For example, FIG. 9 is a schematic diagram of path conversion processing in an embodiment of the present invention. As shown in FIG. 9 , the steps 306 , 308 , 309 , or 315 may include the following steps:

Step 801: The target base station determines the type of the target base station according to the configuration. If the target base station is a micro base station, the target base station starts a third timer with preset waiting time until the third timer times out; otherwise, does not start the third timer. timer, go to step 802.

Step 802: The base station sends a path switching request message to the mobility management entity.

Step 803: After the mobility management entity completes the processing, it returns a path switching request response message to the base station.

In addition, in the technical solution of the present invention, steps 507, 509 and 510 may also have various implementation manners.

For example, FIG. 10 is a schematic diagram of handover notification processing in an embodiment of the present invention. As shown in FIG. 10 , the steps 507, 509, or 510 may include the following steps:

Step 901: The target base station determines the type of the target base station according to the configuration. If the target base station is a micro base station, the target base station starts a third timer with preset waiting time until the third timer times out; otherwise, does not start the third timer. timer, go to step 902;

Step 902: The target base station sends a handover notification message to the mobility management entity, indicating that the mobility management entity user equipment has been handed over to the target cell and the S1 handover has been successfully completed.

To sum up, in the cell handover method of the present invention, when the user equipment switches from the source base station (or macro base station) to the target base station (or micro base station), the source base station reserves dedicated random access resources (or micro base station) for the user equipment. Including: random access preamble and its preset life cycle), and configure it to the user equipment, so that when the user equipment moves from the target base station back to the source base station, it can use the reserved random access preamble to achieve fast handover. The above-mentioned method of reserving the random access preamble for the UE and controlling the handover by the UE saves the time for measurement report reporting, handover preparation and handover command issuance, reduces the handover delay, and reduces the UE dropped calls during the handover process. Moreover, after the user equipment switches to the target base station, the target base station does not request the core network to switch the downlink GTP tunnel within the preset waiting time, so as to prevent the user equipment from performing GTP twice when switching back to the source base station in a short time. Tunnel conversion processing greatly reduces the signaling processing overhead of the base station and the core network.

In addition, by optimizing the path switching process, the downlink GTP tunnel conversion is not performed when the UE is switched from the macro base station to the micro base station and then back to the macro base station within the preset time, which reduces the signaling processing overhead of the base station and the core network. , especially suitable for macro and micro heterogeneous network scenarios.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the present invention. within the scope of protection.

Claims (8)

1. A method for cell handover, characterized in that the method comprises: The source base station reserves dedicated random access resources for the user equipment, and configures the reserved dedicated random access resources to the user equipment; the dedicated random access resources include: a random access preamble and the preset random access resources Lead time of life; After the user equipment is switched to the target base station, the target base station does not request the core network to convert the downlink general packet radio service tunneling protocol GTP tunnel within the preset waiting time; When the user equipment needs to switch back to the source base station, the user equipment initiates random access using the saved dedicated random access preamble, synchronizes with the source base station, and switches back to the source base station; After the user equipment switches back to the source base station, the source base station releases the reserved dedicated random access resources, performs admission control, and configures the allocated radio resource information to the user equipment. 2. The method according to claim 1, wherein the source base station reserving dedicated random access resources for the user equipment comprises: The source base station reserves the random access preamble for the user equipment, and presets the life time of the reserved random access preamble; sets and starts a first timer whose duration is the life time. 3. method according to claim 2, is characterized in that: The source base station sends a radio resource control connection reconfiguration message to the user equipment; The radio resource control connection reconfiguration message carries a handover command and a dedicated random access resource configured for the user equipment. 4. The method according to claim 3, wherein the method further comprises: the user equipment saves the reserved dedicated random access resource, and starts a second timer whose duration is the lifetime; When the second timer expires, the user equipment clears the reserved reserved dedicated random access resources. 5. The method according to claim 4, wherein the target base station does not request the core network to convert the downlink GTP tunnel within a preset waiting time, comprising: The target base station starts the third timer of the preset time; or, the target base station determines whether to start the third timer of the preset time according to the base station type, and if the target base station is a micro base station, the target base station starts the preset time a third timer of time; If the user equipment switches from the target base station to the source base station, the target base station stops the third timer; If the user equipment is still at the target base station, when the third timer expires, for X2 handover, the target base station sends a path switch message to the mobility management entity; for S1 handover, the target base station sends a path switch message to the mobile The sex management entity sends a handover notification message. 6. The method according to claim 5, wherein: When the user equipment determines that it needs to be handed back to the source base station, the user equipment sends a handover instruction message to the target base station; the target base station stops the third timer; Alternatively, when the user equipment determines that it needs to be handed back to the source base station, if the user equipment does not send a handover instruction message, the target base station determines whether the user equipment initiates handover to the source base station by detecting the data transmission situation of the air interface. 7. The method according to claim 6, wherein: For X2 handover, when the user equipment does not decide to switch back to the source base station within the preset time, the life time of the random access resources reserved by the source base station ends, and the source base station releases the reserved random access resources; The target base station determines whether the third timer times out; When the third timer times out, the target base station sends a path switch request message to the mobility management entity, requesting the downlink GTP tunnel to switch to a new GTP tunnel endpoint; Mobility management entity, service gateway and packet data gateway realize the conversion of downlink GTP tunnel to a new GTP tunnel endpoint by modifying the bearer process; The serving gateway sends an end marker packet to the source base station, and forwards it to the target base station through the source base station, indicating the end of data forwarding; The mobility management entity sends a path switching request response message to the target base station to confirm that the path switching is successful; The target base station sends a user equipment uplink release message to the source base station to release resources. 8. The method according to claim 5, wherein: For S1 handover, when the user equipment does not decide to switch back to the source base station within the preset time, the life time of the random access resources reserved by the source base station ends, and the source base station releases the reserved random access resources; The target base station determines whether the third timer times out; When the third timer times out, the target base station sends a handover notification message to the mobility management entity, indicating that the user equipment has been handed over to the target cell and the S1 handover is successfully completed; The mobility management entity, the first serving gateway and the second serving gateway realize the conversion of the downlink GTP tunnel to a new GTP tunnel endpoint by modifying the bearer process; When one of the conditions listed in "Trigger tracking area update" is satisfied, the user equipment initiates the tracking area update process; The mobility management entity releases the logical connection associated with the target base station and the user equipment through the user equipment context release process.

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