WO2019136827A1

WO2019136827A1 - Communication handover method and apparatus

Info

Publication number: WO2019136827A1
Application number: PCT/CN2018/080260
Authority: WO
Inventors: Yuling OUYANG; Ting Zhou; Zhenhong Li; Xin XIA
Original assignee: Jrd Communication (Shenzhen) Ltd
Priority date: 2018-01-11
Filing date: 2018-03-23
Publication date: 2019-07-18
Also published as: CN110035451B; CN110035451A

Abstract

A communication handover method and apparatus are disclosed. The method may include: a source base station receiving a measurement report from a user equipment; determining whether a pre-handover condition is satisfied based on the measurement report; sending a pre-handover command to the UE when the pre-handover condition is satisfied; receiving a random access channel (RACH) successful message from the target base station; monitoring whether signal quality of the UE side satisfies a configured actual handover condition; and executing an actual handover when the signal quality of the UE side satisfies the configured actual handover condition.

Description

COMMUNICATION HANDOVER METHOD AND APPARATUS

TECHNICAL FIELD

The described embodiments 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 LTE and NR mobility management. In LTE, mobility management of the Radio Resource Control (RRC) state is controlled by network, that is, the network determines the connection between the user equipment (UE) and the cells.

In general, in the process of network controlling handover, the UE disconnects from the source base station first, and then connects to the target base station. However, at the time after the UE disconnects from the source base station and before the UE connects to the target base station, the UE connects to neither the source base station, nor the target base station, therefore uplink or downlink user data packets of the UE cannot be transmitted, which results in a long-time interruption during handover.

SUMMARY

The technical problem to be solved by the present disclosure is to provide a communication handover method and apparatus, such that the interruption is reduced during handover.

In order to solve the above-mentioned problems, in accordance with a first aspect, the present disclosure provides a communication method, the communication method may include: receiving by a source base station a measurement report from a user equipment (UE) , determining by the source base station whether a pre-handover condition is satisfied based on the measurement report, sending by the source base station a pre-handover command to the UE when the pre-handover condition is satisfied, wherein the pre-handover command is configured to indicate the UE to connect a target base station and maintain a connection with the source base station, receiving by the source base station a random access channel (RACH) successful message from the target base station, wherein the RACH successful message is configured to indicate that the UE connects to the target base station successfully, monitoring by the source base station whether signal quality of the UE side satisfies a configured actual handover condition; and executing by the source base station an actual handover when the signal quality of the UE side satisfies the configured actual handover condition.

In order to solve the above-mentioned problems, in accordance with a second aspect, the present disclosure provides a communication method. The communication method may include: sending by a user equipment (UE) a measurement report to a source base station, receiving by the UE a pre-handover command from the source base station, wherein the pre-handover command is configured to indicate the UE to connect to a target base station and maintain a connection with the source base station, connecting by the UE to the target base station and maintaining the connection with the source base station in response to the pre-handover command, and executing or not executing by the UE an actual handover according to a notification of whether to execute the actual handover from the source base station or the target base station.

In order to solve the above-mentioned problems, in accordance with a third aspect, the present disclosure provides a communication method. The communication method may include: receiving by a target base station a pre-handover request from a source base station, wherein the pre-handover request comprises information of a user equipment (UE) , the target base station is selected by a source base station according to a measurement report from the UE, sending by the target base station a pre-handover response message to the source base station, connecting by the target base station to the UE, sending by the target base station a Random Access Channel (RACH) successful message to the source base station, wherein the RACH successful message is configured to indicate that the UE connects to the target base station successfully, and executing or not executing by the target base station an actual handover according to a notification of whether to execute the actual handover from 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 apparatus. The communication handover apparatus may include a processor and a communication circuit coupled to the processor, the processor is configured to perform the method described above.

In order to solve the above-mentioned problems, in accordance with a fifth aspect, the present disclosure provides a communication handover apparatus having program data stored therein, the program data is executable to perform the method described above.

The subsequent advantages of the present disclosure may be achieved: compared with the related art, since the source base station sends the pre-handover command to the UE of the present disclosure, the UE could connect to the target base station in parallel to keep the connection with the source base station after responding to the pre-handover command, and execute the actual handover when the signal quality of the source base station of the UE side satisfies the actual handover conditions. The UE could disconnect from the source base station during the actual handover procedure, at this time, the UE has connected to the target base station already, which could reduce the interrupt time during the handover.

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

FIG. 3 is a flow chart of an actual handover after the source base station receives a random access channel successful message from the target base station.

FIG. 4 is a flow chart of a communication method according to a third embodiment of the present disclosure.

FIG. 5 is a flow chart of a communication method according to a fourth embodiment of the present disclosure.

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

FIG. 7 is a flow chart of a communication method according to a sixth embodiment of the present disclosure.

FIG. 8 is a flow chart of a communication method according to a seventh embodiment of the present disclosure.

FIG. 9 is a structural view of a communication handover apparatus according to a first embodiment of the present disclosure.

FIG. 10 is a structural view of a communication handover apparatus according to a second embodiment of the present disclosure.

FIG. 11 is a structural view of a communication handover apparatus according to another embodiment of the second embodiment of the present disclosure.

DETAILED DESCRIPTION

The detailed description set forth below is intended as a description of the subject technology with reference to the appended figures and embodiments.

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

The communication handover method in this embodiment may be executed by a base station. The base station may be a source base station in a handover procedure, that is, the base station that a user equipment (UE) is connecting to currently. The base station may connect to a core network, and communicate to the UE through radio communication. The base station may provide a communication coverage to a corresponding geographic area. The base station may be a macro base station, a micro base station, a pico base station or a femtocell. In some embodiments, the base station may also be named as radio base station, access point, a B node, an evolving B node (eNodeB, eNB) , gNB or other appropriate terms. The communication handover method of this embodiment may include the following blocks.

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

Before the block S101, the source base station may send a measurement configuration message to the UE. The measurement configuration message may be configured to indicate the UE that when to start to measure and when to send the measurement report. For instance, the measurement configuration message may indicate the UE to send the measurement report in a preset period, or send the measurement report when a preset condition is satisfied, such as when signal quality of the source base station is lower than a preset threshold.

In this embodiment, the measurement report may include at least one of: signal quality of objects measured by the UE, a current location of the UE, a movement direction of the UE and load of the target base station. The measured objects may include a source cell and/or a target cell.

In some embodiments, the UE may send the measurement report periodically or non-periodically.

In this embodiment, a non-periodic measurement report may be sent to the source base station after the UE receives the measurement configuration message from the source base station. In another embodiment, the non-periodic measurement report may be sent in an adaptive period according to the signal quality of the source base station. For example, the UE may build a list of signal quality of the source base station corresponding to the sending period, when the signal quality of the source base station is good (a signal quality value of the source base station is great) , the UE may send the measurement report at a lower sending period, and when the signal quality of the source base station is bad (the signal quality value of the source base station is low) , the UE may send the measurement report at a higher sending period.

At block S102: the source base station may determine whether the measurement report satisfies a pre-handover condition.

In this embodiment, the pre-handover condition may include at least one of: a signal quality value of a source cell of the UE side is smaller than a first threshold, a signal quality value of a target cell of the UE side is greater than a second threshold and a difference value between the signal quality value of the target cell of the UE side and the signal quality value of the source cell of the UE side (the signal quality value of the target cell of the UE side minuses the signal quality value of the source cell of the UE side) is greater than a third threshold.

If the pre-condition is satisfied based on the measurement report, go to the block S103. If the pre-condition is not satisfied based on the measurement report, the source base station may wait for another measurement report from the UE to make a determination again, that is, go back to the block S101.

At block S103: the source base station may send a pre-handover command to the UE, the pre-handover command may be configured to indicate the UE to connect to a target base station in parallel to keep a connection with the source base station.

Optionally, before the block S103, the source base station may send a pre-handover request to the target base station, and execute the block S103 when a pre-handover response message received by the source base station from the target base station is an acknowledgement (ACK) .

Since the measurement report includes the signal quality of the measured objects, the source base station may select one of the measured objects as the target base station according to the signal quality of the measured objects. In another embodiment, the source base station may select the target base station through synthetically considering the signal quality of the measured objects, the current location of the UE, the movement direction of the UE and load of the measured objects.

Optionally, the source base station may select a measured object having a signal quality value greater than a preset threshold to be a target base station. In another embodiment, the source base station may arrange the measured objects in an order of the signal quality value from great to small, and take the measured object having a greatest signal quality value as the target base station. The measured objects may be base stations near the source base station, or the base stations whose information could be obtained by the source base station from the interfaces between the base stations directly.

The pre-handover command in this embodiment may be an RRC connection reconfiguration configured to control the UE to connect to the target base station and keep the connection with the source base station at the same time. Configuration parameters of the pre-handover command in this embodiment may be different from those in related art, the configuration parameters of the pre-handover command in this embodiment may be specific configuration parameters, which could control the UE to connect to the target base station in parallel to keep the connection with the source base station. In another embodiment, the pre-handover command may be the same as that of the related art, while a handover mode may be indicated in an advanced handover configuration. When receiving the pre-handover command, the UE under different handover modes may operate in different ways. For example, under an advanced handover mode, the UE may connect to the target base station and maintain the connection with the source base station at the same time when receiving the pre-handover command.

At block S104: the source base station may receive a random access channel (RACH) successful message from the target base station, the RACH successful message is configured to indicate that the UE connects to the target base station successfully.

Although the UE has connected to the target base station already, in order to reduce the load of the interfaces between the source base station and the target base station, the source base station may not forward the user data packets to the target base station temporarily, and no user data packets are transmitted between the UE and the target base station.

At block S105: the source base station may monitor whether signal quality of the UE side satisfies a configured actual handover condition.

Optionally, the signal quality value of the source base station of the UE side under the configured actual handover condition may be smaller than that under the pre-handover condition. The signal quality value of the target base station of the UE side under the configured actual handover condition may be greater than that under the pre-handover condition. The difference value between the signal quality value of the target base station of the UE side and the signal quality value of the source base station of the UE side under the configured actual handover condition may be greater than that under the pre-handover condition. Therefore, the pre-handover procedure could be started when the signal quality of source base station of the UE side is better, thereby avoiding a radio link failure (RLF) , which may occur when the UE disconnects from the source base station before the UE completes the connection to the target base station, especially in high frequency/densely deployed cells.

At block 106: the source base station may execute an actual handover when the signal quality of the UE side satisfies the configured actual handover condition.

Before the actual handover is completed, if the source base station receives the user data packets from the core network, the source base station may forward the user data packets to the target base station instead of sending the user data packets to the UE.

Optionally, when the signal quality of the UE side does not satisfy the configured actual condition, a block S107 could be executed, that is, the source base station may not execute the actual handover.

Since the source base station sends the pre-handover command to the UE, the UE could connect to the target base station in parallel to keep the connection with the source base station after responding to the pre-handover command, and execute the actual handover when the signal quality of the source base station of the UE side satisfies the actual handover conditions. The UE could disconnect from the source base station during the actual handover procedure, at this time, the UE has connected to the target base station already, which could reduce the interrupt time during the handover procedure.

Referring to FIG. 2, a flow chart of a communication method according to a second embodiment of the present disclosure is depicted. The second embodiment is an expanding of the first embodiment of the present disclosure, details of the blocks the same as those of the first embodiment would be not recited herein. The communication handover method of the second embodiment may include the following blocks.

At block S201: the source base station may receive the measurement report from the UE.

At block S202: the source base station may determine whether the pre-handover condition is satisfied based on the measurement report.

In this embodiment, the source base station may determine whether the pre-handover condition is satisfied according to at least one of: the signal quality of the measured objects, the current location of the UE, the movement direction of the UE and the load of the target base station in the measurement report.

In another embodiment, the source base station communicates with the UE by Time Division Multiplexing (TDM) technology. The source base station may estimate the uplink channel conditions based on uplink reference signal. Since frequency of the uplink or the downlink in TDM are the same, the source base station may obtain downlink signal quality of the UE side (i.e. the signal quality of the source cell) as the signal quality of the UE side according to the uplink channel conditions, and then determine whether the signal quality of the UE side satisfies the pre-handover condition.

At block A203: the source base station may select the target base station for the UE based on the measurement report.

In this embodiment, the source base station may select the measured object having a signal quality value greater than the present threshold as the target base station. In another embodiment, the source base station may arrange the measured objects in an order of the signal quality value from great to small, and take the measured object having a greatest signal quality value as the target base station. The measured objects may be base stations near the source base station, or the base stations whose information could be obtained by the source base station from the interfaces between the base stations directly.

In other embodiments, the source base station may select the target base station according to channel conditions in the measurement report. Optionally, the way of selecting the target base station according to the channel conditions may be similar to that according to the signal quality.

Optionally, when the source base station determines that the preset condition is not satisfied, go back to the block S201, the source base station may continue to receive the user measurement report from the UE.

At block S204: the source base station may send the pre-handover request to the target base station.

Optionally, the pre-handover request may include information of the UE.

Information of the UE may include all information needed when a routine handover is completed. For example, information of the UE may include at least one of: the whole contexts of the UE, radio bearer information, an ID of the target cell, eNB/gNB handover transition Key (KeNB*/KgNB*) , the Access Stratum (AS) configuration, a physical layer ID of the source cell and a Message Authentication Code-Integrity (MAC-I) configured to recover a possible Radio Link Failure (RLF) . The whole contexts of the UE may at least include an UE X2/Xn signaling context reference at the source base station and an UE S1/NG signaling context reference. The X2/Xn may be an interface between the base stations. The S1/NG may be an interface between the base station and the core network.

In some embodiments, after the source base station sends the pre-handover request to the target base station, the target base station may execute an admittance control to determine whether the target base station has enough resources to serve the UE. If the target base station has enough resources to serve the UE, the target base station may send an acknowledgement (ACK) of the pre-handover to the source base station, which indicates that the admittance control is successful. If the target base station does not have enough resources to serve the UE, the target base station may send a non-acknowledgement (NACK) of the pre-handover to the source base station, which indicates that the admittance control is failed.

At block S205: the source base station may receive the pre-handover response message from the target base station, and determine whether the pre-handover response message is an ACK.

Optionally, the pre-handover response message may be an ACK or an NACK.

At block S206: the source base station may send the pre-handover command to the UE when receiving the ACK from the target base station, wherein the pre-handover command may be configured to indicate the UE to connect to the target base station and keep the connection with the source base station at the same time.

Optionally, when the source base station receives the NACK, go to a block S207, that is, the source base station may select another target base station for the UE till the ACK is received by the source base station from the selected target base station. In some embodiments, the source base station may select another target base station according to the signal quality or channel conditions in the measurement report. The way of selecting another target base station may be the same as that of selecting the target base station mentioned above, the details are not recited herein.

At block S208: the source base station may receive the RACH successful message from the target base station, wherein the RACH successful message may be configured to indicate that the UE connects to the target base station successfully.

At block S209: the source base station may monitor whether signal quality of the UE side satisfies the configured actual handover condition.

In some embodiments, the block S209 may further include: the source base station may start a switch timer, and monitor whether the signal quality of the UE side satisfies a first condition before the switch timer is expired, if the signal quality of the UE side satisfies the first condition, then determine that the signal quality of the UE side satisfies the configured actual handover condition. After the switch timer is expired, the source base station may monitor whether the signal quality of the UE side satisfies a second condition, if the signal quality of the UE side satisfies the second condition, determine that the signal quality of the UE side satisfies the configured actual handover condition.

It should be understood that, if the signal quality of the UE side monitored by the source base station satisfies the first condition, the source base station could determine that the signal quality of the UE side satisfies the configured actual handover condition directly, and there is no need to determine whether the signal quality satisfies the second condition. Furthermore, if the signal quality of the UE side monitored by the source base station dose not satisfy the first condition before the switch timer is expired but do satisfy the second condition, the source base station could determine that the signal quality of the UE satisfies the configured actual handover condition.

In this embodiment, an initial value of the switch timer may be “0” or a validity period. “0” may correspond to reckoning by time, while the validity period may correspond to counting down. The source base station may determine whether the validity period is over according to whether the current value of the switch timer is bigger than or equal to the validity period, or whether the current value of the switch timer is smaller than or equal to “0” . For example, if the switch timer has an initial value of “0” and a validity period of A, the validity period may be determined to be over when the current value of the switch timer is bigger than or equal to A. Similarly, if the switch timer has an effective value as the initial value, the validity period may be determined to be over when the current value of the switch timer is smaller than or equal to “0” .

There may be many ways for the source base station to monitor whether the signal quality of the UE side satisfies the first condition. For instance, in this embodiment, the source base station may obtain the signal quality of the UE side based on the measurement report from the UE before the switch timer is expired, then determine whether the signal quality of the UE side satisfies the first condition. In another embodiment, the source base station may communicate with the UE through TDM technology. The source base station may estimate the uplink channel conditions based on uplink reference signal. Since frequency of the uplink or the downlink in TDM are the same, the source base station may obtain downlink signal quality of the UE side (i.e. the signal quality of the source cell) as the signal quality of the UE side according to the uplink channel conditions, and then determine whether the signal quality of the UE side satisfies the first condition.

The source base station monitors that whether the signal quality of the UE side satisfies the second condition may further include: the source base station may receive an update measurement report from the UE, and then determine whether the signal quality of the UE side satisfies the second condition. Optionally, the UE may be preseted to send the measurement report to the source base station periodically, such that the source base station could receive the measurement reports from the UE periodically. In other embodiments, the UE may send the measurement report to the source base station after receiving the measurement control message from the source base station.

Optionally, the first condition may include at least one of: the signal quality value of the source cell of the UE side is smaller than a fourth threshold, the signal quality value of the target cell of the UE side is greater than a fifth threshold and the difference value between the signal quality value of the target cell of the UE side and the signal quality value of the source cell of the UE side is greater than a sixth threshold.

The second condition may include at least one of: the signal quality value of the source cell of the UE side is smaller than a seventh threshold, the signal quality value of the target cell of the UE side is greater than an eighth threshold and the difference value between the signal quality value of the target cell of the UE side and the signal quality value of the source cell of the UE side is greater than a ninth threshold.

In some embodiments, the first threshold may be greater than the fourth threshold, and/or the second threshold may be smaller than the fifth threshold, and/or the third threshold may be smaller than the sixth threshold.

In some embodiments, the seventh threshold may be greater than the fourth threshold, and/or the eighth threshold may be smaller than the fifth threshold, and/or the ninth threshold may be smaller than the sixth threshold.

At block S210: the source base station may execute the actual handover when the signal quality of the UE side satisfies the configured actual handover condition.

The block S210 may further include: the source base station may inform the UE to disconnect from the source base station, send a sequence number (SN) status transfer message to the target base station, and forward the user data packets to the target base station.

In this embodiment, the source base station may inform the UE to disconnect from the source base station by sending a connection terminating message to the UE. The connection terminating message is configured to inform the UE to disconnect from the source base station.

In another embodiment, the source base station may inform the UE to disconnect from the source base station by sending a last user data packet to the UE. The last user data packet may include a handover identification configured to indicate starting the actual handover to inform the UE to disconnect from the source base station. Specifically, the user data is divided into a plurality of user data packets based on a preset number of bytes. The user data packets may be sent to the UE one by one, and the last user data packet may be the last one that the source base station sends to the UE. Furthermore, the handover identification of this embodiment may be hidden in the last user data packet, which could reduce a signal overhead between the source base station and the UE. For example, there may be an identification bit in the head of the last user data packet, which is configured to indicate that the last user data packet includes a handover identification. A handover indicator having a length of 1bit in the data packet may be used as the handover identification. In this embodiment, the handover identification having a value of “1” may represent executing the actual handover, while “0” may represent cancelling handover. In another embodiment, the handover identification having a value of “0” may represent executing the actual handover, while “1” may represent cancelling handover.

Optionally, if the signal quality of the UE side does not satisfy a configured actual condition, go to block S211, that is, the source base station may not execute the actual handover.

Referring to FIG. 3, a flow chart of an actual handover after the source base station receives a random access channel successful message from the target base station is depicted. The communication handover method of this embodiment may include the following blocks.

At block S221: the source base station may receive the RACH successful message from the target base station.

The RACH successful message may be configured to indicate that the UE connects to the target base station successfully.

Optionally, in this embodiment, a RACH successful indicator having a length of 1bit may be used as an identification of the target base station connecting to the UE successfully. The RACH successful indicator having a value of “1” may represent accessing successfully, while “0” may represent accessing failed. Of course, in other embodiments, it could be the reverse.

At block A222: the source base station may start a switch timer.

In this embodiment, time of the switch timer may be determined based on at least one of: the signal quality of the source base station, the signal quality of the target base station, movement state of the UE (including movement speed and movement direction, etc. ) and application scenarios in the measurement report. The application scenarios may include using state of the UE, such as dump energy of the UE, service type of the UE and noise around the UE, etc.

At block S223: the source base station may monitor the signal quality of the UE side before the switch timer is expired.

At block S224: the source base station may determine whether the signal quality of the UE side satisfies the first condition before the switch timer is expired.

When the signal quality of the UE side satisfies the first condition, go to block S228 to execute the handover procedure. When the signal quality of the UE side does not satisfy the first condition, go to block S225.

At block S225: the source base station may determine whether the switch timer is expired.

When the switch timer is expired, go to block S226. When the switch timer is not expired, go back to the block S223 such that the source base station continues to monitor the signal quality of the UE side.

At block S226: the source base station may monitor whether the signal quality of the UE side satisfies the second condition.

The block S226 may further include: the source base station may send the measurement control message to the UE, such that the UE may send the update measurement report to the source base station after receiving the measurement control message. The source base station may further determine whether the signal of the UE side satisfies the second condition based on the update measurement report.

In another embodiment, the block S226 may further include: the source base station may receive the measurement report from the UE periodically, and determine whether the signal quality of the UE side satisfies the second condition based on the measurement report sent from the UE periodically.

When the source base station monitors that the signal quality of the UE side satisfies the second condition, go to block S228. When the source base station monitors that the signal quality of the UE side does not satisfy the second condition, go to block S227.

At block S227: the source base station may inform the UE and/or the target base station to cancel the handover.

Optionally, after informing the UE and/or the target base station to cancel the handover, the source base station may continue to receive the measurement report from the UE, so as to determine and execute the next handover.

At block S228: the source base station may inform the UE to disconnect from the source base station, send the SN status transfer message to the target base station, and forward user data packets of the UE to the target base station.

At block S229: the source base station may release the UE resources.

In this embodiment, the source base station may complete the handover after the target base station receives the SN status transfer message and the user data packets of the UE. Then the UE may communicate with the target base station.

The SN status transfer message may be configured to transfer a sequence number of the packet data convergence protocol (PDCP) to inform the target base station data transmission status of the source base station.

The user data may be the user data of the UE received by the source base station from the core network. After the UE executes the actual handover and disconnects from the source base station, the source base station could not send the user data to the UE, therefore the source base station may forward the user data to the target base station rather than transmitting the user data to the UE.

Furthermore, the target base station may send a notification of releasing the UE contexts to the source base station. After receiving the notification of releasing the UE contexts, the source base station may release the UE resources.

Referring to FIG. 4, a flow chart of the communication method according to a third embodiment of the present disclosure is depicted. Executing object of the communication handover method in this embodiment is a user equipment (UE) . The communication handover method in the third embodiment may include the following blocks.

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

Before the block S301, the UE may receive a measurement configuration message from the source base station, which is configured to indicate the UE that when to start measuring and when to send the measurement report.

Optionally, the UE may be a mobile phone, a car desk, a tablet or a smart watch, etc.

The UE may send the measurement report to the source base station periodically or non-periodically, such as an event-triggered type, that is, the UE may send the measurement report to the source base station after receiving the measurement configuration message.

At block S302: the UE may receive a pre-handover command configured to indicate the UE to connect to a target base station and maintain a connection with the source base station.

At block S303: the UE may connect to the target base station and maintain the connection with the source base station in response to the pre-handover command.

Optionally, the UE may send the measurement report to the source base station periodically or in response to a measurement control message from the source base station. The measurement report is used for the source base station to determine whether to execute the handover. How the source base station determines whether to execute the handover may be similar to that mentioned above.

At block S304: the UE may execute or not execute an actual handover according to a notification of whether to execute the actual handover from the source base station or the target base station.

In this embodiment, the UE may execute the actual handover according to the notification of executing the handover from the source base station or the target base station. For example, the UE may disconnect from the source base station when receiving the disconnecting notification from the source base station or the target base station.

Optionally, the UE may disconnect from the source base station when receiving a connection terminating message from the source base station. The connection terminating message may be configured to inform the UE to disconnect from the source base station.

Optionally, the UE may disconnect from the source base station after receiving a last user data packet from the source base station. The last user data packet may include a handover identification configured to indicate starting the actual handover to inform the UE to disconnect from the source base station.

Optionally, the UE may receive a cancel handover message from the source base station or the target base station. The cancel handover message may be configured to indicate the UE not to execute the actual handover. The UE may disconnect from the target base station in response to the cancel handover message.

Referring to FIG. 5, a flow chart of a communication method according to a fourth embodiment of the present disclosure is depicted. The handover method of the fourth embodiment may be executed by the target base station and may include the following blocks.

At block S401: a target base station may receive a pre-handover request from a source base station.

The target base station may be selected for a user equipment (UE) by the source base station according to a measurement report from the UE.

For example, in this embodiment, the source base station may select a measured object having a signal value greater than a preset threshold to be the target base station. In another embodiment, the source base station may arrange the measured objects in an order of the signal quality value from great to small, and take the measured object having a greatest signal quality value as the target base station. The measured objects may be base stations near the source base station, or the base stations whose information could be obtained by the source base station from the interfaces between the base stations directly.

At block S402: the target base station may send a pre-handover response message to the source base station.

The target base station may execute an admittance control to determine whether the target base station has enough resources to serve the UE. If the target base station has enough resources to serve the UE, the target base station may send an acknowledgement (ACK) of the pre-handover to the source base station, which indicates that the admittance control is successful. If the target base station does not have enough resources to serve the UE, the target base station may send a non-Acknowledgement (NACK) of the pre-handover to the source base station, which indicates that the admittance control is failed.

At block S403: the target base station may connect to the UE.

The target base station may connect to the UE, while the UE may maintain the connection with the source base station.

At block S404: the target base station may send a random access channel (RACH) successful message to the source base station, the RACH successful message may be configured to indicate that the UE connects to the target base station successfully.

At block S405: the target base station may execute or not execute an actual handover according to a notification of whether to execute the actual handover from the source base station.

Optionally, the target base station may execute the actual handover according to the notification of executing the actual handover from the source base station. Specifically, the target base station may receive a sequence number (SN) status transfer message from the source base station and forward user data packets of the UE received from the source base station to the UE, then complete the handover and inform the source base station to release UE contexts.

Optionally, the target base station may not execute the handover according to the notification of not executing the actual handover from the source base station. Specifically, the target base station may receive a cancel handover message from the source base station, and disconnect from the UE in response to the cancel handover message.

In some embodiments, the target base station may forward the cancel handover message to the UE, such that the UE releases the connection between the UE and the target base station.

It should be understood that before the actual handover is completed, although the UE has connected to the target base station already, the source base station may not forward the user data to the target base station temporarily in order to reduce load of interfaces between the source base station and the target base station.

Referring to FIG. 6, a flow chart of a communication method according to a fifth embodiment of the present disclosure is depicted.

In the communication handover method of this embodiment, handover may be executed before the switch timer is expired, details of blocks the same as the embodiments above may be not recited herein. The communication handover method of the fifth embodiment may include the following blocks.

At block S501: a source base station may send a measurement configuration message to a user equipment (UE) .

At block S502: the source base station may receive a measurement report from the UE.

At block S503: the source base station may decide to start a pre-handover procedure according to the measurement report and select a target base station for the UE.

At block S504: the source base station may send a pre-handover request to the target base station.

At block S505: the target base station may send an acknowledgement (ACK) of a pre-handover preparation to the source base station.

The target base station may execute the pre-handover preparation in L1 (Physical Layer) /L2 (Data Link Layer) after a admittance control is successful and send the ACK of the pre-handover preparation to the source base station after allocating resources for the UE. Information of allocating resources for the UE by the target base station, such as a new C-RNTI allocated for the UE and a dedicated random access sequence etc., may be included in the ACK of the pre-handover preparation as part of target base station information, or sent to the source base station independently, and then sent to the UE by the source base station.

At block S506: the source base station may send a pre-handover command to the UE.

At block S507: the UE may start a random access to connect to the target base station.

It should be noted that, in this embodiment, the UE may connect to the target base station in parallel to keep the connection with the source base station.

At block S508: the target base station may send a message of the UE connecting to the target base station successfully.

At block S509: the source base station may start a switch timer after receiving the message of the UE connecting to the target base station successfully.

At block S510: the source base station may monitor that the signal quality of the UE side satisfies a first condition before the switch timer is expired.

At block S511: the source base station may send a sequence number (SN) status transfer message to the target base station.

Optionally, the source base station may not forward the user data packets to the UE before executing the actual handover, that is, the source base station may not forward the user data packets to the UE before the block S511, thereby not only avoiding a radio link failure (RLF) between the source base station and the UE, but also reducing the signaling overhead between the source base station and the target base station.

It should be understood that the user data is only transmitted between the UE and the source base station before the block S511.

At block S512: the source base station may forward the user data packets of the UE to the target base station.

At block S513: the source base station may inform the UE to disconnect from the source base station.

The handover method of this embodiment does not limit the order of S511, S512, and S513. For example, the source base station may firstly inform the UE to disconnect from the source base station, then send the SN status transfer message to the target base station and forward the user data packets of the UE to the target base station. In another embodiment, the source base station may inform the UE to disconnect from the source base station, send the SN status transfer message to the target base station and forward the user data packets of the UE to the target base station at the same time.

After the UE completes the handover, the user data packets could be transmitted between the UE and the target base station.

At block S514: the target base station may send a message of releasing the UE contexts to the source base station.

At block S515: the source base station may release the UE resources after receiving the message of releasing the UE contexts.

Referring to FIG. 7, a flow chart of a communication method according to a sixth embodiment of the present disclosure is depicted.

In the communication handover method of this embodiment, handover may not be executed before the switch timer is expired, details of the blocks the same as the embodiments above may be not recited herein. The communication handover method of the sixth embodiment may include the following blocks.

At block S601: a source base station may send a measurement configuration message to a UE.

At block S602: the source base station may receive a measurement report from the UE.

At block S603: the source base station may decide to start a pre-handover procedure according to the measurement report and select a target base station for the UE.

At block S604: the source base station may send a pre-handover request to the target base station.

At block S605: the target base station may send an acknowledgement (ACK) of a pre-handover preparation to the source base station.

At block S606: the source base station may send a pre-handover command to the UE.

At block S607: the UE may start a random access to connect to the target base station.

At block S608: the target base station may send a message of the UE connecting to the target base station successfully.

At block S609: the source base station may start a switch timer after receiving the message of the UE connecting to the target base station successfully.

At block S610: the source base station may monitor that the signal quality of the UE side does not satisfy a first condition before the switch timer is expired.

At block S611: the source base station may send a measurement control message to the UE.

The measurement control message may be the same as or different from the measurement control message in the block S601. The measurement control message may be configured to control the UE such that the UE sends an update measurement report to the source base station. Optionally, the measurement control message may be configured to control the UE to send an update measurement report, or send a plurality of update measurement reports in different time, which is not limited herein.

At block S612: the UE may send the update measurement report to the source base station after receiving the measurement control message from the source base station.

Optionally, the UE may obtain at least one of the signal quality of the source base station, the signal quality of the target base station, movement state of the UE (including movement speed and movement direction, etc. ) and application scenarios after receiving the measurement control message from the source base station to form the update measurement report.

At block S613: the source base station may decide to not execute the handover according to the received update measurement.

At block S614: the source base station may send a cancel handover message to the target base station.

In other embodiments, the source base station may send the cancel handover message to the UE, or inform the UE and the target base station to cancel the handover at the same time.

In this embodiment, a cancel handover indicator having a length of 1bit may be used as identification of cancel handover of the UE and the target base station. In this embodiment, the handover identification having a value of “1” may represent executing the actual handover, while “0” may represent cancelling handover. In another embodiment, the handover identification having a value of “0” may represent executing the actual handover, while “1” may represent cancelling handover.

At block S615: the target base station may disconnect from the UE and release UE resources after receiving the cancel handover message.

In other embodiments, the source base station may send the cancel handover message to the UE, such that the UE disconnects from the target base station.

Referring to FIG. 8, a flow chart of a communication method according to a seventh embodiment of the present disclosure is depicted.

In the communication handover method of this embodiment, handover may be executed after the switch timer is expired, details of the blocks the same as the embodiments above may be not recited herein. The communication handover method of the seventh embodiment may include the following blocks.

At block S701: a source base station may send a measurement configuration message to a UE.

At block S702: the source base station may receive a measurement report from the UE.

At block S703: the source base station may decide to start a pre-handover procedure according to the measurement report and select a target base station for the UE.

At block S704: the source base station may send a pre-handover request to the target base station.

At block S705: the target base station may send an acknowledgement (ACK) of a pre-handover preparation to the source base station.

At block S706: the source base station may send a pre-handover command to the UE.

At block S707: the UE may start a random access to connect to the target base station.

At block S708: the target base station may send a message of the UE connecting to the target base station successfully.

At block S709: the source base station may start a switch timer after receiving the message of the UE connecting to the target base station successfully.

At block S710: the source base station may monitor that the signal quality of the UE side does not satisfy a first condition before the switch timer is expired.

At block S711: the source base station may send a measurement control message to the UE.

At block S712: the UE may send an update measurement report to the source base station after receiving the measurement control message from the source base station.

At block S713: the source base station may decide to execute the handover according to the received update measurement.

At block S714: the source base station may send a sequence number (SN) status transfer message to the target base station,

At block S715: the source base station may forward user data packets of the UE to the target base station,

At block S716: the source base station may inform the UE to disconnect from the source base station.

It should be noted that the handover method of this embodiment may not limit the order of blocks S714, S715, and S716.

At block S717: the target base station may send a notification of releasing UE contexts to the source base station.

At block S718: the source base station may release the UE resources after receiving the notification of releasing UE contexts.

Referring to FIG. 9, a structural view of a communication handover apparatus according to a first embodiment of the present disclosure is depicted.

In this embodiment, the communication handover apparatus 10 may include a processor 11 and a communication circuit 12 coupled to the processor 11.

The processor 11 may be configured to perform the communication handover method of any embodiment mentioned above.

Referring to FIG. 10, a structural view of a communication handover apparatus according to a second embodiment of the present disclosure is depicted.

In this embodiment, the communication handover apparatus 20 may store program data executable to perform the communication handover method of any embodiment mentioned above.

Referring to FIG. 11, a structural view of a communication handover apparatus according to another embodiment of the second embodiment of the present disclosure is depicted. Optionally, in this embodiment, the communication handover apparatus 30 may include a storage device 31. The storage device 31 may be various mediums for storing program codes, such as a U disk, a mobile hard disk, a ROM (Read-Only Memory disk) , a disc, or a server or the like. The communication handover apparatus 30 may be the same as the communication handover apparatus 20 above.

Compared with the related art, since the source base station sends the pre-handover command to the UE of the present disclosure, the UE could connect to the target base station in parallel to keep the connection with the source base station after responding to the pre-handover command, and execute the actual handover when the signal quality of the source base station of the UE side satisfies the actual handover conditions. The UE could disconnect from the source base station during the actual handover procedure, at this time, the UE has connected to the target base station already, which could reduce the interrupt time during the handover.

The above description depicts merely some exemplary embodiments of the disclosure, and is not intended 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 (UE) ;

determining, by the source base station, whether the measurement report satisfies a pre-handover condition ;

sending, by the source base station, a pre-handover command to the UE when the pre-handover condition is satisfied, wherein the pre-handover command is configured to indicate the UE to connect a target base station and maintain a connection with the source base station;

receiving, by the source base station, a random access channel (RACH) successful message from the target base station, wherein the RACH successful message is configured to indicate that the UE connects to the target base station successfully;

monitoring, by the source base station, whether signal quality of the UE side satisfies a configured actual handover condition; and

executing, by the source base station, an actual handover when the signal quality of the UE side satisfies the configured actual handover condition.
The communication handover method of claim 1, before the sending the pre-handover command to the UE when the pre-handover condition is satisfied, further comprising:

selecting, by the source base station, the target base station for the UE based on the measurement report;

sending, by the source base station, a pre-handover request to the target base station; and

receiving, by the source base station, a pre-handover response message from the target base station.
The communication handover method of claim 1, wherein the monitoring the signal quality of the UE side satisfies the configured actual handover condition comprises:

starting, by the source base station, a switch timer;

monitoring, by the source base station, whether the signal quality of the UE side satisfies a first condition before the switch timer is expired, and when the signal quality of the UE side satisfies the first condition, determining the signal quality of the UE side satisfies the actual handover condition;

monitoring, by the source base station, whether the signal quality of the UE side satisfies a second condition after the switch timer is expired, and when the signal quality satisfies the second condition, determining the signal quality of the UE satisfies the actual handover condition.
The communication handover method of claim 3, wherein the monitoring whether the signal quality of the UE side satisfies the first condition before the switch timer is expired comprises:

obtaining, by the source base station, the signal quality of the UE side based on the measurement report from the UE before the switch timer is expired; and

determining, by the source base station, whether the signal quality of the UE side satisfies the first condition.
The communication handover method of claim 3, wherein the source base station communicates with the UE through time division multiplexing (TDM) technology, the monitoring whether the signal quality of the UE satisfies the first condition before the switch timer is expired comprises:

estimating, by the source base station, uplink channel conditions of the UE;

obtaining, by the source base station, the signal quality of the UE side according to the uplink channel conditions; and

determining, by the source base station, whether the signal quality of the UE side satisfies the first condition.
The communication handover method of claim 3, wherein the monitoring whether the signal quality satisfies the second condition comprises:

receiving, by the source base station, an updated measurement report from the UE; and

determining, by the source base station, whether the second condition is satisfied based on the updated measurement report.
The communication handover method of claim 6, before the receiving the updated measurement report from the UE, further comprising:

sending, by the source base station, a measurement control message to the UE.
The communication handover method of claim 3, wherein the pre-handover condition comprises at least one of: a signal quality value of a source cell of the UE-side is smaller than a first threshold, a signal quality value of a target cell of the UE side is greater than a second threshold and a difference value between the signal quality value of the target cell of the UE side and the signal quality value of the source cell of the UE side is greater than a third threshold;

the first condition comprises at least one of: the signal quality value of the source cell of the UE side is smaller than a fourth threshold, the signal quality value of the target cell of the UE side is greater than a fifth threshold and the difference value between the signal quality value of the target cell of the UE side and the signal quality value of the source cell of the UE side is greater than a sixth threshold; and

the second condition comprises at least one of: the signal quality value of the source cell of the UE side is smaller than a seventh threshold, the signal quality value of the target cell of the UE side is greater than an eighth threshold and the difference value between the signal quality value of the target cell of the UE side and the signal quality value of the source cell of the UE side is greater than a ninth threshold.
The communication handover method of claim 8, wherein the first threshold is greater than the fourth threshold, the second threshold is smaller than the fifth threshold and/or the third threshold is smaller than the sixth threshold.
The communication handover method of claim 8, wherein the seventh threshold is greater than the fourth threshold, the eighth threshold is smaller than the fifth threshold and /or the ninth threshold is smaller than the sixth threshold.
The communication handover method of any one of claims 1-10, wherein the executing the actual handover further comprises:

informing, by the source base station, the UE to disconnect from the source base station, sending a sequence number (SN) status transfer message to the target base station, and forwarding user data packets of the UE to the target base station.
The communication handover method of claim 11, wherein the informing the UE to disconnect from the source base station further comprises:

sending, by the source base station, an connection terminating message to the UE, wherein the connection terminating message is configured to inform the UE to disconnect from the source base station; or

sending, by the source base station, a last user data packet to the UE, wherein the last user data packet comprises a handover identification configured to indicate starting the actual handover to inform the UE to disconnect from the source base station.
The communication handover method of claim 11, wherein the source base station does not forward the user data packets until executing the actual handover.
The communication handover method of any one of claims 1-10, after the monitoring whether signal quality of the UE side satisfies the configured actual handover condition, further comprising:

informing, by the source base station, the UE and/or the target base station to cancel the handover when the signal quality of the UE side does not satisfy the configured actual handover condition.
A communication handover method, comprising:

sending, by a user equipment (UE) , a measurement report to a source base station;

receiving, by the UE, a pre-handover command from the source base station, wherein the pre-handover command is configured to indicate the UE to connect to a target base station and maintain a connection with the source base station;

connecting, by the UE, to the target base station and maintaining the connection with the source base station in response to the pre-handover command; and

executing or not executing, by the UE, an actual handover according to a notification of whether to execute the actual handover from the source base station or the target base station.
The communication handover method of claim 15, wherein the executing or not executing the actual handover according to the notification of whether to execute the actual handover from the source base station or the target base station comprises:

receiving, by the UE, from the source base station, a notification of disconnecting from the source base station, the notification is configured to indicate the UE to execute the actual handover; and

disconnecting, by the UE, from the source base station in response to the notification of disconnecting from the source base station.
The communication handover method of claim 16, wherein the receiving from the source base station the notification of disconnecting from the source base station comprises:

receiving, by the UE, a connection terminating message from the source base station, or

receiving, by the UE, a last user data packet from the source base station, wherein the last user data packet comprises a handover identification, the handover identification is configured to indicate starting the actual handover to inform the UE to disconnect from the source base station.
The communication handover method of claim 16, before the receiving from the source base station the notification of disconnecting from the source base station, further comprising:

receiving, by the UE, user data packets from the source base station.
The communication handover method of claim 15, wherein the executing or not executing by the UE the actual handover according to the notification of whether to execute the actual handover from the source base station or the target base station comprises:

receiving, by the UE, a cancel handover message from the source base station or the target base station, the cancel handover message is configured to indicate the UE not to execute the actual handover; and

disconnecting, by the UE, from the target base station in response to the cancel handover message.
The communication handover method of any one of claims 15-19, after the connecting to the target base station and maintaining the connection with the source base station in response to the pre-handover command, further comprising:

sending, by the UE, a measurement report to the source base station periodically or in response to a measurement control message from the source base station, wherein the measurement report is used for the source base station to determine whether to execute the handover.
A communication handover method, comprising:

receiving, by a target base station, a pre-handover request from a source base station, wherein the pre-handover request comprises information of a user equipment (UE) , the target base station is selected by a source base station according to a measurement report from the UE;

sending, by the target base station, a pre-handover response message to the source base station;

connecting, by the target base station, to the UE;

sending, by the target base station, a random access channel (RACH) successful message to the source base station, wherein the RACH successful message is configured to indicate that the UE connects to the target base station successfully; and

executing or not executing, by the target base station, an actual handover according to a notification of whether to execute the actual handover from the source base station.
The method of claim 21, wherein the executing or not executing the actual handover according to the notification of whether to execute the actual handover from the source base station comprises:

receiving, by the target base station, a sequence number (SN) status transfer message from the source base station, and forwarding user data packets received from the source base station to the UE;

completing, by the target base station, the handover; and

informing, by the target base station, the source base station to release UE contexts.
The method of claim 21, wherein the executing or not executing the actual handover according to the notification of whether to execute the actual handover from the source base station further comprises:

receiving, by the target base station, a cancel handover message from the source base station; and

disconnecting, by the target base station, from the UE in response to the cancel handover message.
The method of claim 23, further comprising:

forwarding, by the target base station, the cancel handover message to the UE.
A communication handover apparatus, comprising:

a processor and a communication circuit coupled to the processor, the processor is configured to perform the method of any one of claims 1-24.
A communication handover apparatus, having program data stored therein, wherein the program data is executable to perform the method of any one of claims 1-24.