# US 11,452,012 B2 · Method, apparatus for cell handover and user equipment

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- Number: US 11,452,012 B2
- Document ID: US11452012B2
- Status: Granted
- Kind: B2
- Application number: 16/597,843
- Filed: 2019-10-09
- Published: 2020-02-06
- Granted: 2022-09-20
- Earliest claimed: 2017-04-14
- Assignees: Beijing Xiaomi Mobile Software Co., Ltd.
- Applicants: Beijing Xiaomi Mobile Software Co., Ltd.
- Inventors: Xiaowei Jiang
- Web page: https://patentgrep.com/patent/US11452012B2

## CPC

- H04W 36/302: {due to low signal strength}
- H04W 36/0058: {Transmission of hand-off measurement information, e.g. measurement reports}
- H04W 36/0079: {in case of hand-off failure or rejection}
- H04W 36/305: {Handover due to radio link failure (control signalling for hand-off failure H04W36/0079)}
- H04W 36/00835: {Determination of neighbour cell lists}
- H04W 36/00837: {Determination of triggering parameters for hand-off}
- H04W 36/08: Reselecting an access point
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)

## Abstract

A method of cell handover includes: when receiving a preset handover command transmitted by a base station for indicating a conditional handover command, determining a handover decision parameter corresponding to each target cell; when determining a target cell that meets a handover condition based on the handover decision parameter corresponding to each target cell, starting a preset timer and executing a cell handover operation from a current serving cell to the target cell that meets the handover condition; and when unsuccessfully executing the cell handover operation, recording first handover information in a radio link failure-report for reporting to the base station.

## Claims

### Claim 1

A method of cell handover, comprising:
upon receiving a preset handover command transmitted by a base station, determining a handover decision parameter corresponding to each target cell, wherein the preset handover command indicates a conditional handover command;
upon determining a target cell that meets a handover condition based on the handover decision parameter corresponding to each target cell, starting a T304 timer and executing a cell handover operation from a current serving cell to the target cell that meets the handover condition; and
upon unsuccessfully executing the cell handover operation, recording first handover information in a radio link failure-report, wherein the first handover information at least indicates a time interval between a time when starting the T304 timer and a time when unsuccessfully executing the cell handover operation.

### Claim 2 (depends on 1)

The method according to claim 1, further comprising:
when a radio link failure occurs before determining the target cell that meets the handover condition based on the handover decision parameter corresponding to each target cell, recording second handover information in the radio link failure-report.

### Claim 3 (depends on 2)

The method according to claim 2, wherein the second handover information comprises:
a time interval between a time when receiving the preset handover command and a time when the radio link failure occurs.

### Claim 4 (depends on 1)

The method according to claim 1, wherein the first handover information further comprises one or more of:
a type of connection failure being a conditional handover failure,
a time interval between a time when receiving the preset handover command and a time when unsuccessfully executing the cell handover operation, and
cell identity information of the target cell that executes the cell handover operation.

### Claim 5 (depends on 4)

The method according to claim 4, wherein the unsuccessfully executing the cell handover operation comprises one of the following two cases:
the T304 timer has expired when user equipment has not successfully switched to the target cell, or
a radio link failure occurs in a process of the cell handover operation.

### Claim 6 (depends on 1)

The method according to claim 1, further comprising:
obtaining a measurement result corresponding to each target cell by performing measurement for a signal from each target cell in real time; and
determining whether each target cell meets the handover condition based on the measurement result corresponding to each target cell and the handover decision parameter corresponding to each target cell.

### Claim 7 (depends on 1)

The method according to claim 1, further comprising:
when successfully executing the cell handover operation, stopping the T304 timer.

### Claim 8 (depends on 1)

The method according to claim 1, further comprising:
receiving a request message for obtaining the radio link failure-report transmitted by the base station; and
transmitting a report message carrying the radio link failure-report to the base station.

### Claim 9

A user equipment, comprising:
a processor; and
a memory for storing processor executable instructions;
wherein, the processor is configured to:
upon receiving a preset handover command transmitted by a base station, determine a handover decision parameter corresponding to each target cell, wherein the preset handover command indicates a conditional handover command;
upon determining a target cell that meets a handover condition based on the handover decision parameter corresponding to each target cell, start a T304 timer and execute a cell handover operation from a current serving cell to the target cell that meets the handover condition; and
upon unsuccessfully executing the cell handover operation, record first handover information in a radio link failure-report, wherein the first handover information at least indicates a time interval between a time when starting the T304 timer and a time when unsuccessfully executing the cell handover operation.

### Claim 10 (depends on 9)

The user equipment according to claim 9, wherein the processor is further configured to:
when a radio link failure occurs before determining the target cell that meets the handover condition based on the handover decision parameter corresponding to each target cell, record second handover information in the radio link failure-report.

### Claim 11 (depends on 10)

The user equipment according to claim 10, wherein the second handover information comprises:
a time interval between a time when receiving the preset handover command and a time when the radio link failure occurs.

### Claim 12 (depends on 9)

The user equipment according to claim 9, wherein the first handover information further comprises any one or more of:
a type of connection failure being a conditional handover failure,
a time interval between a time when receiving the preset handover command and a time when unsuccessfully executing the cell handover operation, and
cell identity information of the target cell that executes the cell handover operation.

### Claim 13 (depends on 9)

The user equipment according to claim 9, wherein the processor is further configured to:
obtain a measurement result corresponding to each target cell by performing measurement for a signal from each target cell in real time; and
determine whether each target cell meets the handover condition based on the measurement result corresponding to each target cell and the handover decision parameter corresponding to each target cell.

### Claim 14 (depends on 9)

The user equipment according to claim 9, wherein the processor is further configured to:
when successfully executing the cell handover operation, stop the T304 timer.

### Claim 15 (depends on 9)

The user equipment according to claim 9, wherein the processor is further configured to:
receive a request message for obtaining the radio link failure-report transmitted by the base station; and
transmit a report message carrying the radio link failure-report to the base station.

### Claim 16 (depends on 9)

The user equipment according to claim 9, wherein the handover decision parameter corresponding to each target cell comprises at least one of Reference Signal Receiving Power (RSRP), Received Signal Strength Indicator (RSSI), or Reference Signal Receiving Quality (RSRQ).

### Claim 17 (depends on 16)

The user equipment according to claim 16, wherein the handover decision parameter corresponding to different target cell is different.

### Claim 18 (depends on 17)

The user equipment according to claim 17, wherein the handover decision parameter corresponding a first target cell is the RSSI greater than −75 dBm, and the handover decision parameter corresponding to a second target cell is the RSSI greater than −85 dBm.

### Claim 19 (depends on 18)

The user equipment according to claim 18, wherein the user equipment is configured to perform measurement for each target cell in real time to obtain a measurement result of each target cell to thereby determine whether the measurement result of the each target cell matches the corresponding handover decision parameter, and wherein the measurement result comprises a measured RSSI of the each cell.

### Claim 20

A non-transitory computer-readable storage medium storing instructions, wherein the instructions are executed by a processor to implement operations including:
upon receiving a preset handover command transmitted by a base station, determining a handover decision parameter corresponding to each target cell, wherein the preset handover command indicates a conditional handover command;
upon determining a target cell that meets a handover condition based on the handover decision parameter corresponding to each target cell, starting a T304 timer and executing a cell handover operation from a current serving cell to the target cell that meets the handover condition; and
upon unsuccessfully executing the cell handover operation, recording first handover information in a radio link failure-report, wherein the first handover information at least indicates a time interval between a time when starting the T304 timer and a time when unsuccessfully executing the cell handover operation.