WO2018214273A1

WO2018214273A1 - Communication handover method and apparatus

Info

Publication number: WO2018214273A1
Application number: PCT/CN2017/094502
Authority: WO
Inventors: Xiang Chen; Eddy Chiu
Original assignee: Jrd Communication Inc.
Priority date: 2017-05-26
Filing date: 2017-07-26
Publication date: 2018-11-29
Also published as: CN113825190B; CN108934049A; CN113825190A; CN108934049B

Abstract

A communication handover method and apparatus are disclosed. The communication handover method includes: receiving by a source base station a measurement report from a user equipment; selecting by the source base station a candidate base station for the user equipment according to the measurement report; sending by the source base station an autonomous handover command to the user equipment; wherein the autonomous handover command comprises information of the candidate base station and handover conditions; detecting by the source base station whether a first handover acknowledge message is received from the user equipment; and stopping ongoing transmission and performing a subsequent handover procedure by the source base station when receiving the first handover acknowledge message. In this way, resource waste and handover interruption time can be reduced.

Description

COMMUNICATION HANDOVER METHOD AND APPARATUS

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to communication technology, and in particular relate to a communication handover method and apparatus.

BACKGROUND

Handover (HO) is one of the most fundamental and important procedures in mobility management. In the LTE/LTE-A, the HO of a user equipment (UE) is controlled by a base station (BS) . In NR, as in high frequencies in beamforming technology, channel conditions change rapidly, causing a failure of a HO command delivery to the UE from a source base station (SBS) , with which the UE is currently connected. Once the failure occurs, the control signaling between the UE and the BS is gone, the UE may go radio link failure (RLF) and get a RRC-reestablishment, which takes more latency.

As to resolve this difficulty, an autonomous handover procedure is proposed, during which an early HO command comprising information of several candidate base stations (CBSs) and handover condition can be sent by the SBS to the UE when the channel quality is stable, and the UE execute the handover procedure when the handover condition is satisfied.

In prior art, the SBS fails to know in time whether the UE has executed the autonomous handover procedure, then a case probably happens: the UE has been handed over to a selected target base station (TBS) autonomously. However, the SBS still transmits user data to the UE while the UE has already detached from the SBS, as the SBS is unaware of a message that the UE has handed over to the TBS in time. And the user data cannot be received by the UE. After the UE has been handed over to the TBS successfully, the TBS needs to re-transmit the unsuccessfully-received user data, thus the resources to transmit the user data by the SBS will be wasted, and handover interruption time (which is a time that the UE fails to receive the user data during the handover procedure) will be increased.

SUMMARY

The technical problem to be solved by the present disclosure is to provide a communication handover method and apparatus, such that the problem in the prior art may be solved, in which the source base station fails to know whether or not the UE has executed an autonomous handover such that it brings about resource waste and long handover interruption time.

In order to solve the above-mentioned problems, in accordance with a first aspect, the present disclosure provides a communication handover method, comprising: receiving by a source base station a measurement report from a user equipment； selecting by the source base station a candidate base station for the user equipment according to the measurement report； sending by the source base station an autonomous handover command to the user equipment； wherein the autonomous handover command comprises information of the candidate base station and handover conditions； detecting by the source base station whether a first handover acknowledge message is received from the user equipment； and stopping ongoing transmission and performing a subsequent handover procedure by the source base station when receiving the first handover acknowledge message.

In order to solve the above-mentioned problems, in accordance with a second aspect, the present disclosure provides a communication handover method, comprising: sending by a user equipment a measurement report to a source base station； receiving by the user equipment an autonomous handover command from the source base station, wherein the autonomous handover command comprises information of a candidate base station and handover condition, and the candidate base station is selected by the source base station for the user equipment according to the measurement report； monitoring by the user equipment signal quality of the candidate base station and determining whether the handover condition is satisfied thereby； and choosing the candidate base station of which signal quality satisfies the handover condition as the target base station to hand over to, sending a first handover acknowledge message to the source base station and performing a handover procedure when the signal quality satisfies the handover condition.

In order to solve the above-mentioned problems, in accordance with a third aspect, the present disclosure provides a communication handover method, comprising: receiving by a candidate base station a handover request signaling from a source base station, wherein the handover request signaling comprises information of a user equipment, and the candidate base station is selected by the source base station for the user equipment according to a measurement report from the user equipment； performing admission control by the candidate base station and determining whether it has adequate resources to take over the user equipment； sending by the candidate base station a handover preparation acknowledge message to the source base station when it has adequate resources, wherein the handover preparation acknowledge message is configured to indicate that the admission control is successful； establishing by the candidate base station a connection with the user equipment； and sending by the candidate base station a second handover acknowledge message to the source base station.

In order to solve the above-mentioned problems, in accordance with a fourth aspect, the present disclosure provides a communication handover method, comprising: receiving by a source base station a measurement report from the user equipment； and selecting by the source base station a candidate base station for a user equipment according to the measurement report, wherein the candidate base station is divided into at least two grades, different candidate base stations with different grades have different likelihoods to be chosen by the user equipment as the target base station to hand over to, the grades of information for handover preparation and/or handover procedures corresponding to the different candidate base stations with different grades are different, and the higher likelihood the candidate base station is to be chosen as the target base station, the higher the corresponding grade of information for handover preparation is and/or the simpler the corresponding handover procedure is.

In order to solve the above-mentioned problems, in accordance with a fifth aspect, the present disclosure provides a communication handover method, comprising: sending by a user equipment a measurement report to a source base station； and receiving by the user equipment an autonomous handover command from the source base station, wherein the autonomous handover command comprises information of a candidate base station and handover condition, the candidate base station is selected by the source base station for the user equipment according to the measurement report, and the candidate base station is divided into at least two grades, different candidate base stations with different grades have different likelihoods to be chosen by the user equipment as a target base station to hand over to, the grades of information for handover preparation and/or handover procedures corresponding to the different candidate base stations with different grades are different, and the higher likelihood the candidate base station is to be chosen as the target base station, the higher the corresponding grade of information for handover preparation is and/or the simpler the corresponding handover procedure is.

In order to solve the above-mentioned problems, in accordance with a sixth aspect, the present disclosure provides a communication handover method, comprising: receiving by a candidate base station a handover request signaling from a source base station, wherein the handover request signaling comprises information of a user equipment, the candidate base station is selected by the source base station for the user equipment according to a measurement report from the user equipment, and the candidate base station is divided into at least two grades, different candidate base stations with different grades have different likelihoods to be chosen by the user equipment as a target base station to hand over to, the grades of information for handover preparation and/or handover procedures corresponding to the different candidate base stations with different grades are different, and the higher likelihood the candidate base station is to be chosen as the target base station, the higher the corresponding grade of information for handover preparation is and/or the simpler the corresponding handover procedure is.

In order to solve the above-mentioned problems, in accordance with a seventh aspect, the present disclosure provides a communication handover apparatus, comprising a processor and a communication circuit connected with the processor； wherein the processor is configured to perform programs to achieve any one aforementioned method.

The subsequent advantages of the present disclosure may be achieved: the source base station may determine whether the UE has executed the autonomous handover through detecting whether it receives the first handover acknowledge message from the UE. The source base station can confirm this case in time to perform the subsequent handover procedure when the UE has executed the autonomous handover. During the handover procedure, the source base station stops transmitting user data to the UE and forwards the user data to the target base station, reducing resource waste and handover interruption time.

In addition, the candidate base station is classified. Different candidate base stations with different grades have different likelihood to be chosen by the UE to as the target base station to hand over to. Higher the likelihood of the candidate base station to as the target base station is, higher grade of information for handover preparation is and/or simpler the handover procedure is. Low grade of the information for handover preparation of the candidate base station indicates that there is less information needed to be transmitted during the handover preparation process and the handover preparation process is simple. However, when the candidate base station is chosen as the target base station, it will be needed to compensate for missing actions during the handover preparation process in the subsequent handover procedure. Thus it will also bring about extra latency and signaling overhead. As the grade of the information for handover preparation of the candidate base station and/or the handover procedure are/is determined according to the likelihood of the candidate base station to be chosen as the target base station, it is highly probable for the UE to autonomously hand over to the candidate base station whose grade of the information for handover preparation is high and/or the handover procedure is simple. It can reduce signaling overhead during the handover preparation procedure of the autonomous handover. Meanwhile it can reduce the probability to bring about extra latency and signaling overhead during the handover procedure. Therefore, it ensures that it reduces signaling overhead of the autonomous handover.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart diagram of a communication handover method according to a first embodiment of the present disclosure.

FIG. 2 is a flow chart diagram of a communication handover method according to a second embodiment of the present disclosure.

FIG. 3 is a flow chart diagram of which the autonomous handover is executed by UE within a period of validity and a first handover acknowledge message is received successfully according to the second embodiment of the present disclosure.

FIG. 4 is a flow chart diagram of which the autonomous handover is executed by UE within a period of validity and a first handover acknowledge message is received successfully according to the second embodiment of the present disclosure.

FIG. 5 is a flow chart diagram of which the autonomous handover is not executed by UE within a period of validity according to the second embodiment of the present disclosure.

FIG. 6 is a flow chart diagram of a communication handover method according to a third embodiment of the present disclosure.

FIG. 7 is a flow chart diagram of which UE hands over to a first-grade candidate base station according to a fourth embodiment of the present disclosure.

FIG. 8 is a flow chart diagram of which UE hands over to a second-grade candidate base station according to a fourth embodiment of the present disclosure.

FIG. 9 is a flow chart diagram of which UE hands over to a third-grade candidate base station according to a fourth embodiment of the present disclosure.

FIG. 10 is a flow chart diagram of a communication handover method according to a fifth embodiment of the present disclosure.

FIG. 11 is a flow chart diagram of a communication handover method according to a sixth embodiment of the present disclosure.

FIG. 12 is a flow chart diagram of a communication handover method according to an eighth embodiment of the present disclosure.

FIG. 13 is a flow chart diagram of a communication handover method according to a ninth embodiment of the present disclosure.

FIG. 14 is a flow chart diagram of a communication handover method according to an eleventh embodiment of the present disclosure.

FIG. 15 is a flow chart diagram of a communication handover method according to a twelfth embodiment of the present disclosure.

FIG. 16 is a flow chart diagram of which UE autonomously hands over to a first-grade candidate base station according to one embodiment of the present disclosure.

FIG. 17 is a flow chart diagram of which UE autonomously hands over to a second-grade candidate base station according to one embodiment of the present disclosure.

FIG. 18 is a flow chart diagram of which UE autonomously hands over to a third-grade candidate base station according to one embodiment of the present disclosure.

FIG. 19 is a flow chart diagram of a communication handover method according to a thirteenth embodiment of the present disclosure.

FIG. 20 is a flow chart diagram of a communication handover method according to a fourteenth embodiment of the present disclosure.

FIG. 21 is a flow chart diagram of a communication handover method according to a fifteenth embodiment of the present disclosure.

FIG. 22 is a schematic view of a communication handover apparatus according to a first embodiment of the present disclosure.

FIG. 23 is a schematic view of a communication handover apparatus according to a second embodiment of the present disclosure.

FIG. 24 is a schematic view of a communication handover apparatus according to a third embodiment of the present disclosure.

DETAILED DESCRIPTION

The execution subject of the communication handover method in accordance with a first embodiment may be a base station. And the base station may treated as a source base station (abbreviation: SBS) during a handover procedure, to which a user equipment (abbreviation: UE) is currently connected. The base station may be connected to a core network, and has a wireless communication with the user equipment, providing communication coverage for a corresponding region. The base station may be a macro base station, a micro base station, a pico base station or femtocell. In some embodiments, the base station may be called as the wireless base station, access point, B node, long term B node (eNodeB, eNB) , gNB or other suitable terms. As shown in FIG. 1, the method may include the following blocks in this embodiment.

In block S11: the source base station may receive a measurement report from the UE.

The measurement report may be sent by the UE in periodic and also in non-periodic such as by event-triggered. The source base station may send a measurement configuration message to the UE before the block S11. The measurement configuration message is configured to indicate when to measure and send the measurement report.

In block S12: the source base station may select candidate base stations for the UE according to the measurement report.

The measurement report may comprise signal quality of a measuring object of the UE. The source base station selects several measuring objects therefrom as the candidate base stations according to the signal quality in the measurement report. Except for the measurement report, the source base station may also refer to other information, such as current location of the UE, moving direction and traffic load of the candidate base stations, during a process to select the candidate base stations.

The source base station may select measuring objects whose signal quality is greater than a preset threshold as the candidate base stations. The source base station may also sort the measuring objects in the order of signal quality from the largest to the smallest, and select best N measuring objects as the candidate base stations. N is the number of specified candidate base station. The measuring objects may be base stations which are close to the source base station in geographical location, and may also be base stations from which the source base station can directly obtain information via interfaces therebetween.

In block S13: the source base station may send an autonomous handover command to the UE.

The autonomous handover command may include information of the candidate base stations and handover condition. The UE received the autonomous handover command may perform handover preparation for an autonomous handover.

The handover condition in the autonomous handover command may be a threshold of reference signal receiving power (RSRP) . Different candidate base stations may have same handover condition in one embodiment, and they may also have different handover conditions in another embodiment.

In block S14: the source base station may detect whether it receives a first handover acknowledge message from the UE.

In block S15: the source base station may stop ongoing transmission and perform a subsequent handover procedure when receiving the first handover acknowledge message.

After choosing a target base station, the UE may firstly send the first handover acknowledge message to the source base station, and then execute the autonomous handover to detach from the source base station and be connected to the target base station. The target base station may be a handover target chosen by the UE from the candidate base stations. The first handover acknowledge message may include an identifier of the target base station. In the subsequent handover procedure, the source base station will not transmit the user data to the UE but forward it to the target base station if the source base station receives user data which is to be transmitted to the UE from the core network.

With the implementation of the aforementioned embodiment, the source base station may determine whether the UE has executed the autonomous handover through detecting whether it receives the first handover acknowledge message from the UE. The source base station can confirm this case in time to perform the subsequent handover procedure when the UE has executed the autonomous handover. During the handover procedure, the source base station stops transmitting user data to the UE and forwards the user data to the target base station, reducing resource waste and handover interruption time.

Referring to FIG. 2, which illustrates a communication handover method according to a second embodiment, the source base station may explicitly/implicitly confirm whether or not the UE has executed the autonomous handover, which is based on the communication handover method according to the first embodiment. The same details as that in the first embodiment will not be described again herein. As shown in FIG. 2, the communication handover method in the second embodiment may include the following blocks.

In block S101: the source base station may receive a measurement report from the UE.

In block S102: the source base station may select candidate base stations for the UE according to the measurement report.

In block S103: the source base station may send an autonomous handover command to the UE.

The autonomous handover command may further include a period of validity. The period of validity means the period of validity of the autonomous handover command.

During the period of validity, if the UE has executed the autonomous handover, the UE will send a first handover acknowledge message to the source base station and hand over to a target base station, and if the UE hasn’t executed the autonomous handover, the UE will send a handover non-execution notification to the source base station upon the expiration of the validity of the autonomous handover command. The first handover acknowledge message may include information of a target base station. The autonomous handover command may further include uplink resources allocated for the handover non-execution notification.

In block S104: the source base station may detect whether it receives a first handover acknowledge message from the UE within the period of validity.

If the source base station receives the first handover acknowledge message from the UE with the period of validity, it means that the UE has executed the autonomous handover, which belongs to an explicit indication for the source base station, the source base station will perform block S105. If the source base station still doesn’t receive the first handover acknowledge message from the UE when the period of validity expires, the source base station will perform block S106.

The source base station may adopt a timer to determine whether the period of validity expires. That is to say, the source base station initiates a timer after sending the autonomous handover command to the UE. An initial value of the timer may be 0/period of validity, corresponding to forward timing and reverse timing respectively. The source base station may determine whether the period of validity expires through determining whether a current value of the timer is greater than or equal to the period of validity/less than or equal to 0. The source base station may also determine whether the period of validity expires via the size between a current moment at which the source base station sends the autonomous handover command and the moment at which the period of validity expires. The UE may determine whether the period of validity expires in the same way, in which the difference therebetween lies in that the UE receives the autonomous handover command, rather than the source base station sends the autonomous handover command.

In the block S105: the source base station may stop ongoing transmission and perform a subsequent handover procedure.

In the block S106: the source base station may determine whether it receives a handover non-execution notification from the UE when the period of validity expires.

The handover non-execution notification may include a non-handover message and/or an updated measurement report.

When the source base station doesn’t receive the handover non-execution notification, it means that the UE has executed the autonomous handover within the period of validity, but the UE doesn’t send the first handover acknowledge message or the source base station doesn’t receive the first handover acknowledge successfully as radio environment between the source base station and the UE changes, which implicitly indicates that the autonomous handover has been executed, the source base station will perform block S107. When receiving the handover non-execution notification, it means that the UE hasn’t executed the autonomous handover within the period of validity, and the source base station will evaluate subsequent actions such as preparing for a new autonomous handover command and/or re-selecting candidate base stations.

In the block S107: the source base station may stop ongoing transmission and buffer user data, and wait for a second handover acknowledge message from one target base station to perform the subsequent handover procedure.

The target base station may generally send the second handover acknowledge message to the source base station after establishing a connection with the UE. As the source base station doesn’t receive the first handover acknowledge message, the source base station fails to directly confirm the target base station. Therefore, the source base station may just buffer the received user data and then forward it after receiving the second handover acknowledge message.

Examples will now be described in accordance with the drawings.

FIG. 3 illustrates an example of which the UE has executed the autonomous handover within the period of validity, and the source base station receives the first handover acknowledge message successfully. As shown in FIG. 3, the specific process comprises the following blocks.

In block S111: the source base station receives a measurement report from the UE.

In block S112: the source base station selects a candidate base station for the UE according to the measurement report.

In block S113: the source base station sends a handover request signaling to the candidate base station.

The handover request signaling comprises information of the UE. The candidate base station performs admission control, and determines whether it has adequate resources to take over the UE. The candidate base station sends a handover preparation acknowledge message to the source base station when it has. The handover preparation acknowledge message is configured to indicate that the admission control is successful. The candidate base station sends a handover preparation deny message to the source base station when it doesn’t have adequate resources. The handover preparation deny message is configured to indicate the admission control is failed.

In block S114: the candidate base station sends the handover preparation acknowledge message to the source base station.

The candidate base station performs the admission control in response to the handover request signaling. The candidate base station pre-reserves resources for the UE and sends the handover preparation acknowledge message to the source base station when the admission control is successful.

In block S115: the source base station sends an autonomous handover command to the UE.

The autonomous handover command comprises a period of validity thereof, information of the candidate base station, and handover condition. When the source base station receives the handover preparation deny message from one candidate base station, the autonomous handover command doesn’t comprise information of this candidate base station. The period of validity may match with the periodicity of the measurement report from the UE.

In block S116: the source base station and the UE respectively initiate a timer.

The dashed line in Fig. 3 indicates the period of validity. Timers of the source base station and UE are both configured to timing for the period of validity. The timing durations in theory are both equal to the period of validity. In actual application, the timing durations of both timers may be fine-tuned on basis of the period of validity, as it generally takes time for the UE to receive the autonomous handover command and send the first handover acknowledge. The period of validity is t₀, the time for the UE to receive the autonomous handover command is t₁, and the time for the UE to send the first handover acknowledge message is t₂, then the value range of the timing duration T₁ of the timer at the source base station is [t₀, t₀+t₁+t₂] , the value range of the timing duration T₂ of the timer at the UE is [t₀-t₁-t₂, t₀] , and T₁-T₂＝ t₁+t₂.

In block S117: the UE sends the first handover acknowledge message to the source base station.

The UE sends the first handover acknowledge message after deciding to execute the autonomous handover and having chosen the target base station. The block S117 is executed within the period of validity.

In block S118: the UE hands over to the target base station.

One candidate base station is depicted in Fig. 3, which is chosen as the target base station by the UE. In fact, there may be more candidate base stations.

FIG. 4 illustrates an example of which the UE has executed the autonomous handover within the period of validity, and the source base station receives the first handover acknowledge message unsuccessfully. The same details with that in the previous example will not be described again herein. As shown in FIG. 4, the specific process comprises the following blocks.

In block S121: the source base station receives a measurement report from the UE.

In block S122: the source base station selects a candidate base station for the UE according to the measurement report.

In block S123: the source base station sends a handover request signaling to the candidate base station.

In block S124: the candidate base station sends a handover preparation acknowledge message to the source base station.

In block S125: the source base station sends an autonomous handover command to the UE.

In block S126: the source base station and the UE respectively initiate a timer.

The dashed line in Fig. 4 indicates the period of validity.

In block S127: the UE sends a first handover acknowledge message to the source base station, but the source base station fails to receive the first handover acknowledge message.

The block S127 is executed within the period of validity.

In block S128: the source base station stops ongoing transmission and buffers user data when the period of validity expires.

As not receiving a handover non-execution notification, the source base station confirms that the UE has executed the autonomous handover, then stops transmitting user data to the UE, and buffers user data as failing to know which one is the target base station chosen by the UE.

In block S129: the UE performs synchronization and random access to the selected target base station.

In block S130: the target base station sends a second handover acknowledge message to the source base station.

The target base station may also send the second handover acknowledge message to the source base station after receiving a random access request from the UE.

In block S131: the source base station completes the handover procedure.

The handover procedure comprises forwarding the buffered user data to the target base station.

FIG. 5 illustrates an example of which the UE hasn’t executed the autonomous handover within the period of validity. As shown in FIG. 5, the specific process comprises the following blocks.

In block S133: the source base station receives a measurement report from the UE.

In block S134: the source base station selects a candidate base station for the UE according to the measurement report.

In block S135: the source base station sends a handover request signaling to the candidate base station.

In block S136: the candidate base station sends a handover preparation acknowledge message to the source base station.

In block S137: the source base station sends an autonomous handover command to the UE.

In block S138: the source base station and the UE respectively initiate a timer.

As shown in FIG. 5, the dashed line indicates the period of validity, and the UE hasn’t executed the autonomous handover within the period of validity.

In block S139: the UE sends a handover non-execution notification to the source base station when the period of validity expires.

The source base station may evaluate subsequent actions such as preparation for a new autonomous handover command and/or re-selection of a candidate base station, when determining that the UE hasn’t executed the autonomous handover.

If the UE has executed the autonomous handover within the period of validity, but the source base station doesn’t receive the first handover acknowledge message, the source base station may still transmit user data to the UE as not knowing that the UE has executed the autonomous handover, when there is no period of validity and handover non-execution notification from the UE. With the implementation of the aforementioned embodiment, the source base station can determine whether the UE has executed the autonomous handover to perform subsequent handover procedure according to not-receiving the handover non-execution notification upon the expiration of the period of validity, even if the source base station fails to receive the first handover acknowledge message (for example, in a deteriorated radio environment) . In the handover procedure, the source base station stops transmitting user data to the UE and forwards it to the target base station. In this way, resource waste and handover interruption time may be further reduced.

FIG. 6 is a flow chart diagram of a communication handover method according to a third embodiment of the present disclosure, which is based on that in the first or second embodiment. The communication handover method may comprise the following block, after the source base station receives the first/second handover acknowledge message.

In block S15: the source base station may send a release resource message to un-chosen candidate base stations such that the un-chosen candidate base stations release resources pre-reserved for the UE.

The source base station may confirm which one candidate base station chosen by the UE to as the target base station according to the first/second handover acknowledge message. As the UE may need to hand over to the target base station, other candidate base stations un-chosen by the UE won’t need to prepare for the handover of the UE again. The source base station may inform those candidate base stations to release resources pre-reserved for the UE.

A communication handover method according to a fourth embodiment of the present disclosure is based on that in the first embodiment. In this embodiment, the candidate base stations may be divided into at least two grades.

Different candidate base stations with different grades have different likelihoods to be chosen by the user equipment as a target base station to hand over to. The grades of information for handover preparation and/or handover procedures corresponding to different candidate base stations with different grades are different. When the candidate base station has higher likelihood to be chosen as the target base station, the corresponding grade of information for handover preparation is higher and/or the corresponding handover procedure is simpler.

The information for handover preparation may include at least one of the following: information of the UE in the handover request signaling, information of the candidate base stations in the autonomous handover command, information of the candidate base stations in the handover preparation acknowledge message sent by the candidate base station in response to the handover request signaling. When the information for handover preparation corresponding to the candidate base stations is incomplete, there is less information needed to be transmitted as preparing for the handover, and the handover preparation process is simple. However, during the subsequent handover procedure, the UE/the candidate base station chosen as the target base station may need to compensate for the missing actions in the handover preparation process, which may include allocating resources by the target base station for the UE and/or acquiring supplementary information by the target base station from the source base station. Lower grade of the information for handover preparation of a candidate base station is, more actions are needed to be implemented when the UE hands over to the candidate base station, and then more complicate the handover procedure is.

The source base station needs to evaluate the likelihood of each candidate base station to be chosen as the target base station, so as to classify the candidate base station. Except for signal quality of a measuring object in the measurement report, the source base station may also evaluate the likelihood with the reference to factors such as a current location of the UE, moving direction, traffic load of the candidate base stations and the like.

The source base station may firstly select a plurality of candidate base stations from measuring objects according to the signal quality in the measurement report, and then evaluate a likelihood of each candidate base station to be chosen as the target base station. The source base station may also directly evaluate a likelihood of each measuring object to be chosen as the target base station and select candidate base stations according to the likelihood. The source base station may select measuring objects, of which signal quality is greater than a preset threshold or the likelihood to be chosen as the target base station is larger than a preset threshold, as the candidate base stations. The source base station may also sort the measuring objects in the order of signal quality from the largest to the smallest, and select best N measuring objects as the candidate base stations. N is the number of specified candidate base stations. The measuring objects may be base stations which are close to the source base station in geographical location, and may also be base stations from which the source base station can directly obtain information via interfaces therebetween.

The handover request signaling and/or autonomous handover command may explicitly/implicitly indicate the grades of the candidate base stations. In an explicit case, the handover request signaling and/or autonomous handover command may further include a grade identifier of the candidate base station, which is configured to indicate the grade of the candidate base station. In an implicit case, the UE/candidate base station may determine the grade of the candidate base station according to information of the counterpart in the received autonomous handover command/handover request signaling.

In the prior art, to perform the autonomous handover, the source base station needs to perform the handover preparation along with the UE and all candidate base stations, which includes sending to the candidate base stations the needed information of the UE for the handover to inform the candidate base stations to pre-reserve resources for the UE, sending to the UE the needed information of the candidate base stations for the handover, and the like. In this way, it may bring about large signaling overhead.

With implementation of the aforementioned embodiments, the candidate base station is classified. Different candidate base stations with different grades have different likelihood to be chosen by the UE to as the target base station to hand over to. Higher the likelihood of the candidate base station to as the target base station is, higher grade of information for handover preparation is and/or simpler the handover procedure is. Low grade of the information for handover preparation of the candidate base station indicates that there is less information needed to be transmitted during the handover preparation process and the handover preparation process is simple. However, when the candidate base station is chosen as the target base station, it will be needed to compensate for missing actions during the handover preparation process in the subsequent handover procedure. Thus it will also bring about extra latency and signaling overhead. As the grade of the information for handover preparation of the candidate base station and/or the handover procedure are/is determined according to the likelihood of the candidate base station to be chosen as the target base station, it is highly probable for the UE to autonomously hand over to the candidate base station whose grade of the information for handover preparation is high and/or the handover procedure is simple. It can reduce signaling overhead during the handover preparation procedure of the autonomous handover. Meanwhile it can reduce the probability to bring about extra latency and signaling overhead during the handover procedure. Therefore, it ensures that it reduces signaling overhead of the autonomous handover.

Now the information for handover preparation and the autonomous handover procedure of different candidate base stations with different grades will be described with reference to the accompanying drawings. In one embodiment of the present disclosure, the candidate base stations may be divided into a first grade, a second grade and a third grade, which are respectively indicated with a candidate base station A, a candidate base station B and a candidate base station C in Fig. 7. The same detail with that in aforementioned embodiments will not be described herein again.

As shown in FIG. 7, the UE autonomously hands over to the first-grade candidate base station (that is the candidate base station A) . The process thereof may include the following block.

In block S141: the source base station sends a measurement configuration message to the UE.

In block S142: the source base station receives a measurement report from the UE.

In block S143: the source base station selects candidate base stations A, B and C.

The candidate base station A is the first-grade candidate base station, the candidate base station B is the second-grade candidate base station, and the candidate base stations C is the third-grade candidate base station.

In block S144: the source base station respectively sends a handover request signaling to the candidate base stations A, B and C.

The handover request signaling may include information of the UE. The grades of information of the UE sent to the candidate base stations A, B and C are different.

The information for handover preparation of the candidate base station A is complete. The information of the UE in the handover request signaling sent to the candidate base station A may include necessary information to execute a normal handover at the target side by the first-grade candidate base station, such as full UE context, radio bearer information, target cell ID, eNB/gNB handover transition Key (KeNB*/KgNB*) , RRC context of C-RNTI (Cell Radio Network Temmporary Identify) of the UE at the source base station, AS (Access Stratum) configuration, physical layer ID of a source cell, short MAC-I (Message Authentication Code-Integrity) for possible RLF (Radio Link Failure) recovery and the like. Wherein the full UE context at least includes UE X2/Xn signaling context reference at source eNB, and UE S1/NG signaling context reference. The X2/Xn is an interface among base stations, and the S1/NG is an interface between a base station and the core network.

The information for handover preparation of the candidate base station B is incomplete. The information of the UE in the handover request signaling sent to the candidate base station B may include full UE context, radio bearer information and other a portion of necessary information such as target cell ID.

The grade of the information for handover preparation of the candidate base station C is lower than that of the candidate base station B. The handover request signaling sent to the candidate base station C may only include minimum information of the UE, such as ID of the UE (C-RNTI in a source cell) .

In block S145: the candidate base stations A, B and C respectively send a handover preparation acknowledge message to the source base station.

The candidate base station A prepares a handover with L1/L2 after performing admission control successfully, and sends the handover acknowledge message to the source base station after allocating resources for the UE. The information for handover preparation of the candidate base station A is complete. Information of resources allocated for the UE by the candidate base station A, for instance, a new C-RNTI allocated for the UE, a dedicated random access sequence and the like, may be a portion of information of the candidate base station A to be included in the handover preparation acknowledge message, and may also be independently sent to the source base station and then sent to the UE by the source base station.

The candidate base stations B and C may not allocate resources for the UE but directly send the handover preparation acknowledge message to the source base station after performing admission control successfully. Information for handover preparation of the candidate base stations B and C is incomplete, which doesn’t include information of resources allocated for the UE.

In block S146: the source base station sends an autonomous handover command to the UE.

The autonomous handover command may include information of the candidate base stations A, B and C, handover condition and a period of validity thereof.

The information for handover preparation of the candidate base station A is complete. Information of the candidate base station A in the autonomous handover command may include necessary information to execute a normal handover by the UE, such as target cell ID, handover condition, a new C-RNTI, security algorithm identifiers of the candidate base station A. In addition, information of the candidate base station A may further include a dedicated random access sequence, access parameters, system information, etc. At least a part of those information, for example, the new C-RNTI allocated for the UE by the candidate base station A and the dedicated random access sequence, may be included in the handover preparation acknowledge message sent by the candidate base station A to the source base station. In general, information of resources allocated for the UE by the candidate base station A may be included in the handover preparation acknowledge message sent to the source base station by the candidate base station A.

The information for handover preparation of the candidate base station B is incomplete. The information of the candidate base stations B and C in the autonomous handover command may only include minimum information of the candidate base stations, such as target cell ID and handover condition.

Its own information about a candidate base station, such as target cell ID, security algorithm identifiers and the like, may be included in the handover preparation acknowledge message sent to the source base station by the candidate base station. Also, it may be sent to the source base station periodically or non-periodically.

In one embodiment, the handover condition of each candidate base station may be included in the information thereof. In other embodiments, for example, in which handover conditions of all candidate base stations are same, the handover condition may also be independent with the information the candidate base station.

In block S147: the UE chooses the candidate base station A as the target base station to hand over to.

The UE monitors signal quality of a candidate base station and determines whether it meets the handover condition. When the monitoring result indicates that the signal quality of the candidate base station A meets the handover condition, the UE choose the candidate base station A as the target base station. Generally, the handover condition is similar to trigger condition of the measurement report during a traditional handover process.

In block S148: the UE sends a first handover acknowledge message to the source base station.

The first handover acknowledge message may include an identifier of the target base station which is the candidate base station A. The blocks S147 and S148 are executed within the period of validity (shown in dash-line box of Fig. 7) .

In block S149: the source base station sends a SN (Sequence Number) status transfer message to the candidate base station A.

The SN status transfer message may be configured to transfer sequence number of PDCP (Packet Data Convergence Protocol) to inform the candidate base station A the status of data transmission of the source base station.

In block S150: the source base station forwards user data to the candidate base station A.

The user data are received by the source base station from the core network and transmitted to the UE. The UE has executed the autonomous handover, and detached from the source base station. Therefore, the source base station fails to transmit the user data to the UE, then stops ongoing user data transmission and forwards user data.

When the source base station hasn’t received the user data, the block S150 may not be executed.

In block S151: the source base station sends a release resource message to the candidate base stations B and C.

The candidate base stations B and C are not chosen to as the target to hand over to. Therefore, the source base station informs them to release resources pre-reserved for the UE. Although the candidate base stations B and C don’t allocate resources for the UE, they may probably still store the UE context, UE ID, etc., which also need to be released.

The executed sequence of the blocks S151, S149 and S152 is only schematic. In fact, they may be executed in other orders, and also be executed simultaneously.

In block S152: the UE performs synchronization and random access.

In block S153: the UE sends a first handover complete message to the candidate base station A.

In block S154: the candidate base station A sends a second handover complete message to the source base station.

In block S155: the source base station releases resources.

The blocks S149-S155 (except for S151) are same with that in the traditional handover process. Of course, other handover processes may also be used.

As shown in FIG. 8, the UE autonomously hands over to the second-grade candidate base station (that is the candidate base station B) . The process thereof may include the following block.

In block S161: the source base station sends a measurement configuration message to the UE.

In block S162: the source base station receives a measurement report from the UE.

In block S163: the source base station selects candidate base stations A, B and C.

In block S164: the source base station respectively sends a handover request signaling to the candidate base stations A, B and C.

In block S165: the candidate base stations A, B and C send a handover preparation acknowledge message to the source base station.

In block S166: the source base station sends an autonomous handover command to the UE.

In block S167: the UE chooses the candidate base station B as the target base station to be handed over.

In block S168: the UE sends a first handover acknowledge message to the source base station.

In block S169: the source base station sends a SN status transfer message to the candidate base station B.

In block S170: the source base station forwards user data to the candidate base station B.

When the source base station hasn’t received the user data, the block S170 may not be executed.

In block S171: the source base station sends a release resource message to the candidate base stations A and C.

The candidate base stations A and C are not chosen by the UE to as the target to be hand over to. Therefore, the source base station informs them to release resources pre-reserved for the UE. Pre-reserved resources for the UE released by the candidate base station A in response to the resource release message may include resources allocated for the UE and information such as the stored UE context, UE ID. Although the candidate base station C does not allocate resources for the UE, it may probably still store the UE context, UE ID, etc., which also need to be released.

The executed sequence of the blocks S171, S169 and S172 is only schematic. In fact, they may be executed in other orders, and also be executed simultaneously.

In the block S172: the UE performs synchronization and random access to the candidate base station B.

In block S173: the UE performs a RRC connection re-establishment with the candidate base station B.

In block S174: the candidate base station B sends a handover complete message to the source base station.

In block S175: the source base station releases resources.

The same or similar details with that in the case in which the UE hands over to the candidate base station A will not be described herein.

As handover information of the candidate base station B is incomplete, the block S173 after the block S172 needs to be executed to compensate for the missing actions during the handover preparation process. Although the handover information of the candidate base station B is incomplete, the candidate base station B has received full UE context and radio bearer information, such that the candidate base station B completes the access of the UE without acquiring supplementary information from the source base station.

As shown in FIG. 9, the UE autonomously hands over to the third-grade candidate base station (that is the candidate base station C) . The process thereof may include the following block.

In block S181: the source base station sends a measurement configuration message to the UE.

In block S182: the source base station receives a measurement report from the UE.

In block S183: the source base station selects candidate base stations A, B and C.

In block S184: the source base station respectively sends a handover request signaling to the candidate base stations A, B and C.

In block S185: the candidate base stations A, B and C respectively send a handover preparation acknowledge message to the source base station.

In block S186: the source base station sends an autonomous handover command to the UE.

In block S187: the UE chooses the candidate base station C as the target base station to be handed over.

In block S188: the UE sends a first handover acknowledge message to the source base station.

In block S189: the source base station sends a SN status transfer message and supplementary information to the candidate base station C.

The supplementary information may at least include necessary information for synchronization and random access between the candidate base station C and the UE, such as full context of the UE and radio bearer information.

The SN status transfer message and supplementary information can be sent simultaneously or successively, which is not limited herein.

In block S190: the source base station forwards user data to the candidate base station C.

When the source base station hasn’t received the user data, the block S190 may not be executed.

In block S191: the source base station sends a release resource message to the candidate base stations.

The candidate base stations A and B are not chosen to as the target to be hand over. Therefore, the source base station informs them to release resources pre-reserved for the UE. Pre-reserved resources for the UE released by the candidate base station A in response to the resource release message may include resources allocated for the UE and information such as the stored UE context, UE ID. Although the candidate base station B does not allocate resources for the UE, it may probably still store the UE context, UE ID, etc., which also need to be released.

The executed sequence of the blocks S191, S189 and S192 is only schematic. In fact, they may be executed in other orders, and also be executed simultaneously.

In block S192: the UE performs synchronization and random access to the candidate base station C.

In block S193: the UE completes a RRC connection re-establishment with the candidate base station C.

In block S194: the candidate base station C sends a handover complete message to the source base station.

In block S195: the source base station releases resources.

The same or similar details with that in the case in which the UE hands over to the candidate base station A/B will not be described herein.

As the handover information of the candidate base station C is incomplete, the candidate base station C fails to directly complete an access of the UE. Therefore, the candidate base station C further needs to acquire supplementary information from the source base station before the access, except to perform a RRC re-establishment after the access.

In the aforementioned examples, the source base station has successfully received the first handover acknowledge message from the UE. In fact, the source base station may also receive unsuccessfully, then the subsequent handover procedure (such as sending the SN status transfer message and supplementary information to the target base station, and forwarding user data) at the source base station may be executed after the source base station receives the second handover acknowledge message sent by the target base station.

In this embodiment, the candidate base stations are divided into three grades. In fact, the number of grades of the candidate base station may be any one integer which is greater than 1. For instance, the candidate base stations may be divided into two grades. The information for handover preparation of one grade is complete, and the information for handover preparation of the other grade is incomplete. The candidate base station with the incomplete handover information at least needs to allocate resources for the UE during the handover process.

FIG. 10 is a flow chart diagram of a communication handover method according to a fifth embodiment of the present disclosure. The execution subject in this embodiment may be a base station, which is treated as a candidate base station during a handover procedure. As shown in FIG. 10, the communication handover method may include the following blocks.

In block S21: the candidate base station may receive a handover request signaling from a source base station.

The handover request signaling may include information of the UE. The candidate base station is selected for the UE by the source base station according to a measurement report from the UE.

In block S22: the candidate base station may perform admission control, and determine whether it has adequate resources to take over the UE.

In block S23: the candidate base station may send a handover preparation acknowledge message to the source base station when it has adequate resources.

The handover preparation acknowledge message is configured to indicate successful admission control. In addition, the candidate base station may also have choice to allocate resources for the UE. At this time, the handover preparation acknowledge message may include information of the allocated resources, such as new C-RNTI, dedicated random access sequence.

In block S24: the candidate base station may establish a connection with the UE.

In this embodiment, the UE has executed an autonomous handover, and the candidate base station has been chosen by the UE to as a target base station.

The candidate base station establishes the connection with the UE, which may mean that the candidate base station completes synchronization and random access with the UE, and also may mean that the candidate base station has received a random access request from the UE.

In block S25: the candidate base station may send a second handover acknowledge message.

The second handover acknowledge message is used to inform the source base station which one candidate base station is chosen by the UE to as the target base station. The UE will send a first handover acknowledge message to the source base station when executing the autonomous handover. The first handover acknowledge message may include an identifier of the target base station. When the source base station receives the first handover acknowledge message unsuccessfully, although it may confirm that the UE has executed the autonomous handover according to un-receiving a handover non-execution notification from the UE upon the expiration of a period of validity of the autonomous handover command sent to the UE, the source base station fails to know which one candidate base station chosen by the UE to as the target base station. Therefore, the target base station is needed to inform the source base station.

FIG. 11 is a flow chart diagram of a communication handover method according to a sixth embodiment of the present disclosure, which is based on that in the fifth embodiment. In this embodiment, the candidate base station sends the second handover acknowledge message only when confirming that the source base station hasn’t received the first handover acknowledge message. The same details as that in the fifth embodiment will not be described again herein. As shown in FIG. 11, the method may include the following blocks in this embodiment.

In block S211: the candidate base station may receive a handover request signaling from the source base station.

In block S212: the candidate base station may perform admission control, and determine whether it has adequate resources to take over the UE.

Block S213 will be executed when it has, and block S217 will be executed when it hasn’t.

In the block S213: the candidate base station may send a handover preparation acknowledge message to the source base station.

Then, the source base station will send information of the candidate base station to the UE.

In block S214: the candidate base station may establish a connection with the UE.

In block S215: the candidate base station may determine whether it has received a SN status transfer message and/or user data sent by the source base station.

When the source base station has successfully received the first handover acknowledge message from the UE, it may directly perform a subsequent handover procedure which includes sending the SN status transfer message to the target base station which is the candidate base station in this embodiment, and forwarding user data to the target base station as receiving user data from the core network.

The candidate base station has received the SN status transfer message and/or user data, meaning that the source base station has successfully received the first handover acknowledge message and executed the subsequent handover procedure, and there is no need for the candidate base station to send the second handover acknowledge message again. The candidate base station hasn’t received the SN status transfer message and/or user data, meaning that the source base station may has probably unsuccessfully received the first handover acknowledge message, and then block S216 will be executed.

In the block S216: the candidate base station may send the second handover acknowledge message to the source base station.

In the block S217: the candidate base station may send a handover preparation deny message to the source base station.

This process ends, and then the source base station will remove the execution subject in this embodiment from the list of candidate base stations. The handover preparation deny message is used to indicate unsuccessful admission control.

A communication handover method according to a seventh embodiment of the present disclosure is based on that in the fifth embodiment. In this embodiment, the candidate base stations may be divided into at least two grades.

Different candidate base stations with different grades have different likelihoods to be chosen by the user equipment as a target base station to hand over to. The grades of information for handover preparation and/or handover procedures corresponding to different candidate base stations with different grades are different, and the candidate base station has higher likelihood to be chosen as the target base station, higher corresponding grade of information for handover preparation is and/or simpler corresponding handover procedure is.

When the information for handover preparation corresponding to the candidate base stations is incomplete, there is less information needed to be transmitted as preparing for the handover, and the handover preparation process is simple. However, during the subsequent handover procedure, the UE/the candidate base station chosen as the target base station may need to compensate for missing actions in the handover preparation process, which may include allocating resources by the target base station for the UE and/or acquiring supplementary information by the target base station from the source base station. Lower grade of the information for handover preparation of a candidate base station is, more actions are needed to be implemented when the UE hands over to the candidate base station, and then more complicate the handover procedure is.

The information for handover preparation and handover procedures of different candidate base stations with different grades may be referred to the communication handover method in the fourth embodiment and examples thereof, which will not be described herein again.

FIG. 12 is a flow chart diagram of a communication handover method according to an eighth embodiment of the present disclosure, of which the execution subject may be a UE. The UE may be fixed and also mobile, such as cellular phones, personal digital assistants (PDA) , wireless modems, tablet PCs, laptops, cordless phones, etc. The communication handover method may include the following blocks in this embodiment.

In block S31: the UE may send a measurement report to a source base station.

The measurement report may be sent by the UE in periodic and also in non-periodic such as by event-triggered. The UE may receive a measurement configuration message from the source base station before the block S31. The measurement configuration message is configured to indicate when to measure and send the measurement report.

In block S32: the UE may receive an autonomous handover command from the source base station.

The autonomous handover command may include information of candidate base stations and handover condition. The candidate base stations may be selected by the source base station for the UE according to the measurement report. The handover condition in the autonomous handover command may be a threshold of reference signal receiving power (RSRP) . Different candidate base stations may have same handover condition in one embodiment. And they may also have different handover conditions.

In block S33: the UE may monitor signal quality of the candidate base stations and determine whether the handover condition is satisfied thereby.

In block S34: the UE may choose one candidate base station whose signal quality satisfies the handover condition as a target base station to hand over to, send a first handover acknowledge message to the source base station and perform a handover procedure, when the handover condition is satisfied.

If there is one candidate base station whose signal quality satisfies the handover condition, the UE may directly choose it as the target base station. If there are one or more candidate base stations whose signal quality satisfies the handover condition, the UE may choose one of them as the target base station according to a preset principle such as best signal quality.

The first handover acknowledge message may include an identifier of the target base station.

FIG. 13 is a flow chart diagram of a communication handover method according to a ninth embodiment of the present disclosure, which is based on that in the eighth embodiment. In this embodiment, the UE sends a handover non-execution notification when it doesn’t execute the autonomous handover. The same details as that in the eighth embodiment will not be described herein again. The communication handover method may include the following blocks in this embodiment.

In block S301: the UE may send a measurement report to a source base station.

In block S302: the UE may receive an autonomous handover command from the source base station.

The autonomous handover command further includes a period of validity which means the period of validity of the autonomous handover command. The autonomous handover command may further include uplink resources allocated for the handover non-execution notification.

In block S303: the UE may monitor signal quality of candidate base stations within the period of validity and determine whether the handover condition is satisfied thereby.

The UE may adopt a timer to determine whether the period of validity expires. That is to say, the UE initiates a timer after receiving the autonomous handover command. An initial value of the timer may be 0/period of validity, corresponding to forward timing and reverse timing respectively. The UE may determine whether the period of validity expires through determining whether a current value of the timer is greater than or equal to the period of validity/less than or equal to 0. The UE may also determine whether the period of validity expires via the size between a current moment at which the UE receives the autonomous handover command and the moment at which the period of validity expires.

Block S304 will be executed when the UE finds one candidate base station whose signal quality satisfies the handover condition within the period of validity. And block S305 will be executed when it doesn’t.

In the block S304: the UE may choose one candidate base station whose signal quality meets the handover condition as the target base station to hand over to, send a first handover acknowledge message to the source base station and perform a handover procedure.

In the block S305: the UE may send the handover non-execution notification to the source base station.

The source base station may evaluate subsequent actions according to the handover non-execution notification, such as preparing a new autonomous handover command and/or re-selecting candidate base stations.

In addition, if the autonomously handover fails, the UE may re-evaluate signal quality of cells of the source base station and candidate base stations, and select one cell with optimal signal quality therefrom.

If the selected cell is a source cell which the UE is originally connected, as the source base station still stores the context of the UE, the UE may try to continue the RRC connection with the source cell. If the selected cell is a cell of the candidate base stations, the UE may try to adopt RRC connection re-configuration or re-establishment to connect to the cell according to the grades of the candidate base stations. When the cell with optimal signal quality cannot meet access requirement of the UE, the UE may transit to idle state to perform cell re-selection and then try to connect to one re-selected cell.

Specific examples may be seen in description of the second embodiment, and not described herein again.

A communication handover method according to a tenth embodiment of the present disclosure is based on that in the first embodiment. In this embodiment, the candidate base stations may be divided into at least two grades.

FIG. 14 is a flow chart diagram of a communication handover method according to an eleventh embodiment of the present disclosure. In this embodiment, the execution subject may be a base station, and the base station may be treated as a source base station during a handover procedure. The communication handover method may include the following blocks.

In block S41: the source base station may receive a measurement report from the UE.

The measurement report may be sent by the UE in periodic and also in non-periodic such as by event-triggered. The source base station may send a measurement configuration message to the UE before the block S41. The measurement configuration message is configured to indicate when to measure and send the measurement report.

In block S42: the source base station may select candidate base stations for the UE according to the measurement report, wherein the candidate base stations may be divided into at least two grades.

FIG. 15 is a flow chart diagram of a communication handover method according to a twelfth embodiment of the present disclosure, which is based on that in the eleventh embodiment. The communication handover method may further include the following blocks after the block S42.

In block S43: the source base station may send a handover request signaling to the candidate base stations.

The handover request signaling may include information of the UE. The candidate base stations may perform admission control, and determine whether it has adequate resources to take over the UE. The candidate base stations may send a handover preparation acknowledge message to the source base station when it has, which is configured to indicate successful admission control. The candidate base station may send a handover preparation deny message to the source base station, which is configured to indicate unsuccessful admission control.

In block S44: the source base station may receive the handover preparation acknowledge message sent by the candidate base stations in response the handover request signaling.

In block S45: the source base station may send an autonomous handover command to the UE.

The autonomous handover command may include information of candidate base stations and handover condition. The handover condition in the autonomous handover command may be a threshold of RSRP. Different candidate base stations may have same handover condition. And they may also have different handover conditions.

The information for handover preparation may include at least one of the following: information of the UE in the handover request signaling, information of the candidate base stations in the autonomous handover command, information of the candidate base stations in the handover preparation acknowledge message sent by the candidate base station in response to the handover request signaling. The UE/ candidate base station may perform the handover preparation for the autonomous handover when receiving the autonomous handover command/handover request signaling. Different candidate base stations with different grades may perform different handover preparation. Higher likelihood of one candidate base station chosen to as the target base station is, higher grade of handover preparation it performs.

Now the information for handover preparation and the autonomous handover procedures of different candidate base stations with different grades will be described with reference to the accompanying drawings. In one embodiment of the present disclosure, the candidate base stations may be divided into a first grade, a second grade and a third grade, which are respectively indicated with a candidate base station A, a candidate base station B and a candidate base station C in Fig. 16. The same detail with that in aforementioned embodiments will not be described herein again.

As shown in FIG. 16, the UE autonomously hands over to the first-grade candidate base station (that is the candidate base station A) . The process thereof may include the following block.

In block S411: the source base station sends a measurement configuration message to the UE.

In block S412: the source base station receives a measurement report from the UE.

In block S413: the source base station selects candidate base stations A, B and C.

The candidate base stations A is the first-grade candidate base station, the candidate base station B is the second-grade candidate base station, and the candidate base stations C is the third-grade candidate base station.

In block S414: the source base station respectively sends a handover request signaling to the candidate base stations A, B and C.

The information for handover preparation of the candidate base station A is complete. The information of the UE in the handover request signaling sent to the candidate base station A may include necessary information to execute a normal handover at the target side by the first-grade candidate base station, such as full UE context, radio bearer information, target cell ID, KeNB*/KgNB*, RRC context of C-RNTI of the UE at the source base station, AS configuration, physical layer ID of a source cell, short MAC-I for possible RLF recovery and the like. Wherein the full UE context at least includes UE X2/Xn signaling context reference at source eNB, and UE S1/NG signaling context reference. The X2/Xn is an interface among base stations, and the S1/NG is an interface between a base station and the core network.

In block S415: the candidate base stations A, B and C respectively send a handover preparation acknowledge message to the source base station.

In block S416: the source base station sends an autonomous handover command to the UE.

The autonomous handover command may include information of the candidate base stations A, B and C, handover condition and the period of validity.

The information for handover preparation of the candidate base stations B and C is incomplete. The information of the candidate base stations B and C in the autonomous handover command may only include minimum information of the candidate base station, such as target cell ID and handover condition.

In one embodiment, the handover condition of each candidate base station may be included in the information thereof. In other embodiments, the handover condition may also be independent with the information the candidate base station. For example, handover conditions of all candidate base stations are same.

In block S417: the UE chooses the candidate base station A as the target base station to hand over to.

In block S418: the UE sends a first handover acknowledge message to the source base station.

The first handover acknowledge message may include an identifier of the target base station which is the candidate base station A.

In block S419: the source base station sends a SN (Sequence Number) status transfer message to the candidate base station A.

The SN status transfer message may be configured to transfer sequence number of PDCP to inform the candidate base station A the status of data transmission of the source base station.

In block S420: the source base station forwards user data to the candidate base station A.

When the source base station hasn’t received the user data, the block S420 may not be executed.

In block S421: the source base station sends a release resource message to the candidate base stations B and C.

The candidate base stations B and C are not chosen to as the target to be hand over to. Therefore, the source base station informs them to release resources pre-reserved for the UE. Although the candidate base stations B and C don’t allocate resources for the UE, they may probably still store the UE context, UE ID, etc., which are also needed to be released.

The executed sequence of the blocks S421 and S419 is only schematic. In fact, they may be executed in other orders, and also be executed simultaneously.

In block S422: the UE performs synchronization and random access.

In block S423: the UE sends a first handover complete message to the candidate base station A.

In block S424: the candidate base station A sends a second handover complete message to the source base station.

In block S425: the source base station releases resources.

The blocks S419-S425 (except for S421) are same with that in the traditional handover process. Of course, other handover processes may also be used.

In this embodiment, the source base station confirms that the UE has executed the autonomous handover via receiving the handover acknowledge message from the UE. In fact, the source base station can confirm that the UE has executed the autonomous handover in other ways.

As shown in FIG. 17, the UE autonomously hands over to the second grade candidate base station (that is the candidate base station B) . The process thereof may include the following block.

In block S431: the source base station sends a measurement configuration message to the UE.

In block S432: the source base station receives a measurement report from the UE.

In block S433: the source base station selects candidate base stations A, B and C.

In block S434: the source base station respectively sends a handover request signaling to the candidate base stations A, B and C.

In block S435: the candidate base stations A, B and C respectively send a handover preparation acknowledge message to the source base station.

In block S436: the source base station sends an autonomous handover command to the UE.

In block S437: the UE chooses the candidate base station B as the target base station to hand over to.

In block S438: the UE sends a first handover acknowledge message to the source base station.

In block S439: the source base station sends a SN status transfer message to the candidate base station B.

In block S440: the source base station forwards user data to the candidate base station B.

When the source base station hasn’t received the user data, the block S440 may not be executed.

In block S441: the source base station sends a release resource message to the candidate base stations A and C.

The candidate base stations A and C are not chosen to as the target to be hand over to. Therefore, the source base station informs them to release resources pre-reserved for the UE. Pre-reserved resources for the UE released by the candidate base station A in response to the resource release message may include resources allocated for the UE and information such as the stored context, UE ID. Although the candidate base station C does not allocate resources for the UE, it may probably still store the UE context, UE ID, etc., which are also needed to be released.

The executed sequence of the blocks S441, S439 and S442 is only schematic. In fact, they may be executed in other orders, and also be executed simultaneously.

In the block S442: the UE performs synchronization and random access to the candidate base station B.

In block S443: the UE performs a RRC connection re-establishment with the candidate base station B.

In block S444: the candidate base station B sends a handover complete message to the source base station.

In block S445: the source base station releases resources.

As the handover information of the candidate base station B is incomplete, the block S443 after the block S422 is needed to be executed to acquiring supplementary information. Although the handover information of the candidate base station B is incomplete, the candidate base station B has received full UE context and radio bearer information, such that the candidate base station B completes the access of the UE without acquiring supplementary information from the source base station.

In other embodiments, the UE and candidate base station B may acquire supplementary information and then perform a traditional handover procedure.

As shown in FIG. 18, the UE autonomously hands over to the third-grade candidate base station (that is the candidate base station C) . The process thereof may include the following block.

In block S451: the source base station sends a measurement configuration message to the UE.

In block S452: the source base station receives a measurement report from the UE.

In block S453: the source base station selects candidate base stations A, B and C.

In block S454: the source base station respectively sends a handover request signaling to the candidate base stations A, B and C.

In block S455: the candidate base stations A, B and C respectively send a handover preparation acknowledge message to the source base station.

In block S456: the source base station sends an autonomous handover command to the UE.

In block S457: the UE chooses the candidate base station C as the target base station to hand over to.

In block S458: the UE sends a first handover acknowledge message to the source base station.

In block S459: the source base station sends a SN status transfer message and supplementary information to the candidate base station C.

In block S460: the source base station forwards user data to the candidate base station C.

When the source base station hasn’t received the user data, the block S460 may not be executed.

In block S461: the source base station sends a release resource message to the candidate base stations A and B.

The candidate base stations A and B are not chosen to as the target to hand over to. Therefore, the source base station informs them to release resources pre-reserved for the UE. Pre-reserved resources for the UE released by the candidate base station A in response to the resource release message may include resources allocated for the UE and information such as the stored context, UE ID. Although the candidate base station B doesn’t allocate resources for the UE, it may probably still store the UE context, UE ID, etc., which are also needed to be released.

The executed sequence of the blocks S461, S459 and S462 is only schematic. In fact, they may be executed in other orders, and also be executed simultaneously.

In the block S462: the UE performs synchronization and random access to the candidate base station C.

In block S463: the UE completes a RRC connection re-establishment with the candidate base station C.

In block S464: the candidate base station C sends a handover complete message to the source base station.

In block S465: the source base station releases resources.

In this embodiment, the candidate base stations are divided into three grades. In fact, the number of grades of the candidate base station may be any one integer which is greater than 1. For instance, the candidate base stations may be divided into two grades. The information for handover preparation of one grade is complete, and the information for handover preparation of the other grade is incomplete. The candidate base station with incomplete information for handover preparation at least needs to obtain supplementary information from the UE during the handover procedure.

FIG. 19 is a flow chart diagram of a communication handover method according to a thirteenth embodiment of the present disclosure, of which the execution subject may be a base station, and the base station is treated as a candidate base station during a handover procedure. The method may include the following blocks in this embodiment.

In block S51: the candidate base station may receive a handover request signaling from the source base station.

The handover request signaling may include information of the UE, and the candidate base station is selected by a source base station for the UE according to a measurement report from the UE. Candidate base stations may be divided into at least two grades. Different candidate base stations with different grades have different likelihoods to be chosen by the user equipment as a target base station to hand over to. The grades of information for handover preparation and/or handover procedures corresponding to different candidate base stations with different grades are different, and the candidate base station has higher likelihood to be chosen as the target base station, higher corresponding grade of information for handover preparation is and/or simpler corresponding handover procedure is.

The handover request signaling may explicitly/implicitly indicate the grade of the candidate base station. The information for handover preparation and handover procedures of different candidate base stations with different grades may be referred to the communication handover method in the twelfth embodiment and examples thereof, which will not be described herein again.

FIG. 20 is a flow chart diagram of a communication handover method according to a fourteenth embodiment of the present disclosure, which is based on that in the thirteenth embodiment. The communication handover method may include the following blocks after the block S51.

In block S52: the candidate base station may perform admission control, and determine it has adequate resources to take over a UE.

Block S53 will be executed when it has, and block S54 will be executed when it hasn’t.

In the block S53: the candidate base station may send a handover preparation acknowledge message to the source base station.

The handover preparation acknowledge message is configured to indicate successful admission control. The candidate base station may pre-reserve resources for the source base station according to its own grade.

In the block S54: the candidate base station may send a handover preparation deny message to the source base station.

The handover preparation deny message is used to indicate unsuccessful admission control. Then the source base station will not send information of the candidate base station to the UE.

FIG. 21 is a flow chart diagram of a communication handover method according to a fifteenth embodiment of the present disclosure, of which the execution subject may be a UE. The UE may be fixed and also mobile, such as cellular phones, personal digital assistants (PDA) , wireless modems, tablet PCs, laptops, cordless phones, etc. The communication handover method may include the following blocks in this embodiment.

In block S61: the UE may send a measurement report to a source base station.

The measurement report may be sent by the UE in periodic and also in non-periodic such as by event-triggered. The UE may receive a measurement configuration message from the source base station before the block S61. The measurement configuration message is configured to indicate when to measure and send the measurement report.

In block S62: the UE may receive an autonomous handover command from the source base station.

The autonomous handover command may include information of a candidate base station and handover condition. The candidate base station is selected by the source base station for the UE according to the measurement report. The candidate base stations may be divided into at least two grades. Different candidate base stations with different grades have different likelihoods to be chosen by the user equipment as a target base station to hand over to. The grades of information for handover preparation and/or handover procedures corresponding to different candidate base stations with different grades are different, and the candidate base station has higher likelihood to be chosen as the target base station, higher corresponding grade of information for handover preparation is and/or simpler corresponding handover procedure is.

In addition, if the autonomous handover fails, the UE may re-evaluate signal quality of cells of the source base station and the candidate base stations, and select one cell with optimal signal quality therefrom.

If the chosen cell is a source cell to which the UE is originally connected, as the source base station still store the context of the UE, the UE may try to continue the RRC connection with the source cell. If the chosen cell is a cell of the candidate base stations, the UE may try to adopt RRC connection reconfiguration or re-establishment to connect to the cell according to the grades of the candidate base stations. When the cell with optimal signal quality cannot meet access requirement of the UE, the UE may transit to idle state to perform cell re-selection and then try to connect to one re-selected cell.

The handover request signaling may explicitlyimplicitly indicate the grade of the candidate base station. The information for handover preparation and handover procedures of different candidate base stations with different grades may be referred to the communication handover method in the twelfth embodiment and examples thereof, which will not be described herein again.

FIG. 22 illustrates a communication handover apparatus according to a first embodiment, which may include a processor 110 and a communication circuit 120. The processor 110 may be connected to the communication circuit 120.

The communication circuit 120 may be configured to transmit and receive data, which is an interface for communication between the communication handover apparatus and other communication devices.

The processor 110 may be configured to perform programs to achieve any one of the communication handover methods in accordance with the first to seventh embodiment or the eleventh to fourteenth embodiment, or a method provided with arbitrary and non-conflicting combination of the communication handover methods therein.

The communication handover apparatus in the present embodiment may be a base station, and also be a separate component integrated in a base station, such as a base band board.

FIG. 23 illustrates a communication handover apparatus according to a first embodiment, which may include a processor 210 and a communication circuit 220. The processor 210 may be connected to the communication circuit 220.

The communication circuit 220 may be configured for transmitting and receiving data, which is an interface for communication between the communication handover apparatus and other communication devices.

The processor 210 may be configured for performing programs to achieve any one of the communication handover methods in accordance with the eighth to tenth embodiment or the fifteenth embodiment, or a method provided with arbitrary and non-conflicting combination of the communication handover methods therein.

The communication handover apparatus in the present embodiment may be a UE, and also be a separate component integrated in a UE, such as a base band chip.

FIG. 24 shows a communication handover apparatus according to a third embodiment, which may include a memory 310. The memory 310 is used to store instructions therein. When the instructions are performed, any one of the communication handover methods in accordance with the first to seventh embodiment, the eleventh to fourteenth embodiment, the eighth to ninth embodiment, or the fifteenth embodiment, or a method provided with arbitrary and non-conflicting combination of the communication handover methods therein may be achieved. The memory 310 may include a Read-Only Memory (ROM) , a Random Access Memory (RAM) , a Flash Memory, hard disk, optical disk, etc.

The functions of each part of each communication handover apparatus and the feasible expansion can be referred to the description of the corresponding communication handover method according to embodiments of the present disclosure, and be no longer repeated to describe herein.

The above description depicts merely some exemplary embodiments of the disclosure, but is not meant to limit the scope of the disclosure. Any equivalent structure or flow transformations made to the disclosure, or any direct or indirect applications of the disclosure on other related fields, shall all be covered within the protection of the disclosure.

Claims

A communication handover method, comprising:

receiving by a source base station a measurement report from a user equipment；

selecting by the source base station a candidate base station for the user equipment according to the measurement report；

sending by the source base station an autonomous handover command to the user equipment； wherein the autonomous handover command comprises information of the candidate base station and handover conditions；

detecting by the source base station whether a first handover acknowledge message is received from the user equipment； and

stopping ongoing transmission and performing a subsequent handover procedure by the source base station when receiving the first handover acknowledge message.
The method of claim 1, wherein the autonomous handover command further comprises a period of validity thereof；

the detecting whether the first handover acknowledge message is received from the user equipment by the source base station comprises:

detecting whether the first handover acknowledge message is received from the user equipment by the source base station within the period of validity； and

after the detecting by the source base station whether the first handover acknowledge message is received from the user equipment, the method further comprises:

determining whether a handover non-execution notification is received upon the period of validity expires when not receiving the first handover acknowledge message； and

stopping ongoing transmission and buffering user data by the source base station, and waiting for a second handover acknowledge message from a target base station chosen by the user equipment from the candidate base station so as to perform a subsequent handover procedure, when not receiving the handover non-execution notification.
The method of claim 2, wherein the handover non-execution notification comprises an updated measurement report.
The method of claim 2, wherein the autonomous handover command further comprises uplink resources allocated for the handover non-execution notification.
The method of claim 2, after receiving the first or second handover acknowledge message by the source base station, further comprising:

sending by the source base station a release resource message to an un-chosen candidate base station by the UE, such that the un-chosen candidate base station releases pre-reserved resources for the user equipment.
The method of any one of claims 1-5, before sending the autonomous handover command to the user equipment by the source base station, further comprising:

sending by the source base station a handover request signaling to the candidate base station, wherein the handover request signaling comprises information of the user equipment； and

receiving by the source base station a handover preparation acknowledge message sent by the candidate base station in response to the handover request signaling.
The method of claim 6, wherein at least portion of the information of the candidate base station comprised in the autonomous handover signaling comes from the handover preparation acknowledge message.
The method of claim 6, wherein the candidate base station is divided into at least two grades, different candidate base stations with different grades have different likelihoods to be chosen by the user equipment as the target base station to hand over to, the grades of information for handover preparation and/or handover procedures corresponding to the different candidate base stations with different grades are different, and the higher likelihood the candidate base station is to be chosen as the target base station, the higher the corresponding grade of information for handover preparation is and/or simpler the corresponding handover procedure is.
The method of claim 8, wherein the candidate base station is classified as at least a first-grade candidate base station or a second-grade candidate base station, information for handover preparation corresponding to the first-grade candidate base station is complete, and the corresponding handover procedure doesn’t comprise obtaining supplementary information by the target base station； and information for handover preparation corresponding to the second-grade candidate base station is incomplete, and the corresponding handover procedure comprises allocating resources for the user equipment by the target base station.
The method of claim 9, wherein the candidate base station is further classified as a third-grade candidate base station, and the handover procedure corresponding to the third-grade candidate base station comprises obtaining supplementary information from the source base station and allocating resources for the user equipment by the target base station.
The method of claim 10, wherein the obtaining supplementary information from the source base station by the target base station comprises:

sending by the source base station the supplementary information to the target base station after receiving the first or second handover acknowledge message.
The method of claim 9, wherein the allocating resources for the user equipment by the target base station comprises:

performing by the target base station a RRC connection re-establishment with the user equipment.
The method of claim 8, wherein the information for handover preparation comprises at least one of the following: information of the user equipment in the handover request signaling, information of the candidate base station in the autonomous handover command and information of the candidate base station in the handover preparation acknowledge message.
The method of claim 8, wherein the handover request signaling and/or the autonomous handover command further comprises a grade identifier of the candidate base station.
A communication handover method, comprising:

sending by a user equipment a measurement report to a source base station；

receiving by the user equipment an autonomous handover command from the source base station, wherein the autonomous handover command comprises information of a candidate base station and handover condition, and the candidate base station is selected by the source base station for the user equipment according to the measurement report；

monitoring by the user equipment signal quality of the candidate base station and determining whether the handover condition is satisfied thereby； and

choosing the candidate base station of which signal quality satisfies the handover condition as the target base station to hand over to, sending a first handover acknowledge message to the source base station and performing a handover procedure when the signal quality satisfies the handover condition.
The method of claim 15, wherein the autonomous handover command further comprises a period of validity thereof；

monitoring by the user equipment the signal quality of the candidate base station and determining whether the handover condition is satisfied thereby comprises:

monitoring by the user equipment the signal quality of the candidate base station within the period of validity and determining whether the handover condition is satisfied thereby； and

after the monitoring by the user equipment the signal quality of the candidate base station within the period of validity and determining whether the handover condition is satisfied thereby, the method further comprises:

sending by the user equipment a handover non-execution notification to the source base station when the target base station is still not chosen upon the period of validity expires.
The method of claim 16, wherein the handover non-execution notification comprises an updated measurement report.
The method of claim 16, wherein the autonomous handover command further comprises uplink resources allocated for the handover non-execution notification.
The method of any one of claims 15-18, wherein the candidate base station is divided into at least two grades, different candidate base stations with different grades have different likelihoods to be chosen by the user equipment as the target base station, the grades of information for handover preparation and/or handover procedures corresponding to the different candidate base stations with different grades are different, and the higher likelihood the candidate base station is to be chosen as the target base station, the higher the corresponding grade of information for handover preparation is and/or the simpler the corresponding handover procedure is.
The method of claim 19, wherein the candidate base station is classified as at least a first-grade candidate base station or a second-grade candidate base station, information for handover preparation corresponding to the first-grade the candidate base station is complete, and the corresponding handover procedure doesn’t comprise obtaining supplementary information by the target base station； information for handover preparation corresponding to the second-grade candidate base station is incomplete, and the corresponding handover procedure comprises allocating resources for the user equipment by the target base station.
The method of claim 20, wherein allocating resources for the user equipment by the target base station comprises:

performing by the user equipment a RRC connection re-establishment with the target base station after having access to the target base station.
The method of claim 19, wherein the autonomous handover command further comprises a grade identifier of the candidate base station.
A communication handover method, comprising:

receiving by a candidate base station a handover request signaling from a source base station, wherein the handover request signaling comprises information of a user equipment, and the candidate base station is selected by the source base station for the user equipment according to a measurement report from the user equipment；

performing admission control by the candidate base station and determining whether it has adequate resources to take over the user equipment；

sending by the candidate base station a handover preparation acknowledge message to the source base station when it has adequate resources, wherein the handover preparation acknowledge message is configured to indicate that the admission control is successful；

establishing by the candidate base station a connection with the user equipment； and

sending by the candidate base station a second handover acknowledge message to the source base station.
The method of claim 23, before the sending by the candidate base station the second handover acknowledge message to the source base station, further comprising:

determining by the candidate base station whether a SN status transfer message and/or user data is received； and

sending by the candidate base station the second handover acknowledge message to the source base station when not receiving the SN status transfer message and/or user data.
The method of claim 23, after the performing the admission control by the candidate base station, further comprising:

sending by the candidate base station a handover preparation deny message to the source base station when it hasn’t adequate resources, wherein the handover preparation deny message is configured to indicate that the admission control is failed.
The method of any one of claims 23-25, wherein the candidate base station is divided into at least two grades, different candidate base stations with different grades have different likelihoods to be chosen by the user equipment as a target base station to hand over to, the grades of information for handover preparation and/or handover procedures corresponding to the different candidate base stations with different grades are different, and the higher likelihood the candidate base station is to be chosen as the target base station, the higher the corresponding grade of information for handover preparation is and/or the simpler the corresponding handover procedure is.
The method of claim 26, wherein the candidate base station is classified as at least a first-grade candidate base station or a second-grade candidate base station, information for handover preparation corresponding to the first-grade candidate base station is complete, and the corresponding handover procedure doesn’t comprise obtaining supplementary information by the target base station； and information for handover preparation corresponding to the second-grade candidate base station is incomplete, and the corresponding handover procedure comprises allocating resources for the user equipment by the target base station.
The method of claim 27, wherein the candidate base station is further classified as a third-grade candidate base station, and the handover procedure corresponding to the third-grade candidate base station comprises obtaining supplementary information from the source base station and allocating resources for the user equipment by the target base station.
The method of claim 28, wherein the obtaining by the target base station the supplementary information from the source base station comprises:

receiving by the target base station the supplementary information sent by the source base station after receiving the first handover acknowledge message from the user equipment or the second handover acknowledge message.
The method of claim 28, wherein if the target base station is the third-grade candidate base station, the information of the user equipment in the handover request signaling doesn’t comprise a full context and radio bearer information of the user equipment.
The method of claim 27, wherein the allocating resources for the user equipment by the target base station comprises:

performing by the target base station a RRC connection reestablishment with the user equipment.
The method of claim 27, wherein if the candidate base station is classified as the first-grade candidate base station, the corresponding handover preparation acknowledge message comprises at least portion of information of the candidate base station, and the method further comprises the following before sending the handover preparation acknowledge message to the source base station:

performing handover preparation by the candidate base station to allocate resources for the user equipment in response to the handover request signaling.
The method of claim 27, wherein if the candidate base station is classified as the second-grade candidate base station, the corresponding handover preparation acknowledge message doesn’t comprise the information of the candidate base station.
The method of claim 26, wherein the handover request signaling further comprises a grade identifier of the candidate base station.
A communication handover method, comprising:

receiving by a source base station a measurement report from the user equipment； and

selecting by the source base station a candidate base station for a user equipment according to the measurement report, wherein the candidate base station is divided into at least two grades, different candidate base stations with different grades have different likelihoods to be chosen by the user equipment as the target base station to hand over to, the grades of information for handover preparation and/or handover procedures corresponding to the different candidate base stations with different grades are different, and the higher likelihood the candidate base station is to be chosen as the target base station, the higher the corresponding grade of information for handover preparation is and/or the simpler the corresponding handover procedure is.
The method of claim 35, wherein the candidate base station is classified as at least a first-grade candidate base station or a second-grade candidate base station, information for handover preparation corresponding to the first-grade candidate base station is complete, and the corresponding handover procedure doesn’t comprise obtaining supplementary information by the target base station； and information for handover preparation corresponding to the second-grade candidate base station is incomplete, and the corresponding handover procedure comprises allocating resources for the user equipment by the target base station.
The method of claim 36, wherein the candidate base station is further classified as a third-grade candidate base station, and the handover procedure corresponding to the third-grade candidate base station comprises obtaining supplementary information from the source base station and allocating resources for the user equipment by the target base station.
The method of claim 37, wherein the obtaining supplementary information from the source base station by the target base station comprises:

sending by the source base station the supplementary information to the target base station.
The method of claim 36, wherein the allocating resources for the user equipment by the target base station comprises:

performing by the target base station a RRC connection re-establishment with the user equipment.
The method of any one of claims 35-39, after selecting the candidate base station by the source base station for the user equipment according to the measurement report, further comprising:

sending a handover request signaling to the candidate base station, receiving a handover preparation acknowledge message sent by the candidate base station in response to the handover request signaling, and sending an autonomous handover command to the user equipment, wherein the handover request signaling comprises information of the user equipment, the autonomous handover command comprises information of the candidate base station and handover condition, and the handover preparation information comprises at least one of the following: information of the user equipment in the handover request signaling, information of the candidate base station in the autonomous handover command and information of the candidate base station in the handover preparation acknowledge message.
The method of claim 40, wherein the handover request signaling and/or the autonomous handover command further comprises a grade identifier of the candidate base station.
The method of claim 40, wherein at least portion of the information of the candidate base station in the autonomous handover command comes from the handover preparation acknowledge message.
The method of claim 40, after sending by the source base station the autonomous handover command to the user equipment, further comprising:

confirming by the source base station the candidate base station chosen by the user equipment as the target base station； and

sending a release resource message by the source base station to an un-chosen candidate base station, such that the un-chosen candidate base station releases pre-reserved resources for the user equipment.
A communication handover method, comprising:

sending by a user equipment a measurement report to a source base station； and

receiving by the user equipment an autonomous handover command from the source base station, wherein the autonomous handover command comprises information of a candidate base station and handover condition, the candidate base station is selected by the source base station for the user equipment according to the measurement report, and the candidate base station is divided into at least two grades, different candidate base stations with different grades have different likelihoods to be chosen by the user equipment as a target base station to hand over to, the grades of information for handover preparation and/or handover procedures corresponding to the different candidate base stations with different grades are different, and the higher likelihood the candidate base station is to be chosen as the target base station, the higher the corresponding grade of information for handover preparation is and/or the simpler the corresponding handover procedure is.
The method of claim 44, wherein the candidate base station is classified as at least a first-grade candidate base station or a second-grade candidate base station, information for handover preparation corresponding to the first-grade candidate base station is complete, and the corresponding handover procedure doesn’t comprise obtaining supplementary information by the target base station； information for handover preparation corresponding to the second-grade candidate base station is incomplete, and the corresponding handover procedure comprises allocating resources for the user equipment by the target base station.
The method of claim 45, wherein the allocating resources for the user equipment by the target base station comprises:

performing by the user equipment a RRC connection re-establishment with the target base station after having access to the target base station.
The method of any one of claims 44-46, wherein the autonomous handover command further comprises a grade identifier of the candidate base stations.
A communication handover method, comprising:

receiving by a candidate base station a handover request signaling from a source base station, wherein the handover request signaling comprises information of a user equipment, the candidate base station is selected by the source base station for the user equipment according to a measurement report from the user equipment, and the candidate base station is divided into at least two grades, different candidate base stations with different grades have different likelihoods to be chosen by the user equipment as a target base station to hand over to, the grades of information for handover preparation and/or handover procedures corresponding to the different candidate base stations with different grades are different, and the higher likelihood the candidate base station is to be chosen as the target base station, the higher the corresponding grade of information for handover preparation is and/or the simpler the corresponding handover procedure is.
The method of claim 48, wherein the candidate base station is classified as at least a first-grade candidate base station or a second-grade candidate base station, information for handover preparation corresponding to the first-grade candidate base station is complete, and the corresponding handover procedure doesn’t comprise obtaining supplementary information by the target base station； information for handover preparation corresponding to the second-grade candidate base station is incomplete, and the corresponding handover procedure comprises allocating resources for the user equipment by the target base station.
The method of claim 49, wherein the candidate base station is further classified as a third-grade candidate base station, and the handover procedure corresponding to the third-grade candidate base station comprises obtaining supplementary information from the source base station and allocating resources for the user equipment by the target base station.
The method of claim 50, wherein the obtaining supplementary information from the source base station by the target base station comprises:

receiving by the target base station the supplementary information from the source base station.
The method of claim 50, wherein if the target base station is the third-grade candidate base station, the information of the user equipment in the handover request signaling doesn’t comprise a full context and radio bearer information of the user equipment.
The method of claim 49, wherein the allocating resources for the user equipment by the target base station comprises:

performing by the target base station a RRC connection re-establishment with the user equipment.
The method of claim 49, wherein if the candidate base station is classified as the first-grade candidate base station, the method further comprises the following after receiving a handover request signaling from the source base station:

performing admission control by the candidate base station and determining whether it has adequate resources to take over the user equipment； and

performing handover preparation by the candidate base station to allocate resources for the user equipment in response to the handover request signaling and sending a handover preparation acknowledge message to the source base station when it has adequate resources, wherein the handover preparation acknowledge message comprising at least portion of information of the candidate base station is configured to indicate that the admission control is successful； and sending by the candidate base station a handover preparation deny message to the source base station when it doesn’t have adequate resources, wherein the handover preparation deny message is configured to indicate that the admission control is failed.
The method of claim 49, wherein if the candidate base station is classified as the second-grade candidate base station, and the method further comprises the following after receiving the handover request signaling from the source base station:

performing admission control by the candidate base station and determining whether it has adequate resources to take over the user equipment； and

sending by the candidate base station a handover preparation acknowledge message to the source base station when it has adequate resources, wherein the handover preparation acknowledge message is configured to indicate that the admission control is successful； and sending by the candidate base station a handover preparation deny message to the source base station when it doesn’t have adequate resources, wherein the handover preparation deny message is configured to indicate that the admission control is failed.
The method of any one of claims 48-55, after receiving the handover request signaling from the source base station, further comprising:

receiving by the candidate base station a release resource message from the source base station； and

releasing by the candidate base station pre-reserved resources for the user equipment in response to the release resource message.
The method of any one of claims 48-55, wherein the handover request signaling further comprises a grade identifier of the candidate base station.
A communication handover apparatus, comprising a processor and a communication circuit connected with the processor； wherein the processor is configured to perform programs to achieve a method in any one of claims 1-57.
A communication handover apparatus, storing programs, wherein the programs are performed to achieve a method in any one of claims 1-57.