Handover method and device in ultra-dense network

1. A handover method, comprising:

receiving, by a terminal, a command message sent by a source base station, wherein the command message carries a granted resource that is allocated by a target base station to the terminal, wherein the command message further carries a maximum quantity of transmission times that is configured for the granted resource by the target base station, and wherein a value of the maximum quantity of transmission times is set to 1;

sending, by the terminal, a radio resource control (RRC) connection reconfiguration complete message to the target base station on the granted resource, wherein the RRC connection reconfiguration complete message is used to indicate to the target base station that the terminal is successfully handed over to, dual-linked to, or multi-linked to the target base station; and

after sending, by the terminal, the RRC connection reconfiguration complete message to the target base station on the granted resource, initiating, by the terminal, a random access process to the target base station when the configured maximum quantity of transmission times for the granted resource is reached and the terminal receives a negative feedback message indicating that signaling transmission on the granted resource fails.

2. The method according to claim 1 , further comprising:

before the sending, by the terminal, an RRC connection reconfiguration complete message to the target base station on the granted resource:

performing, by the terminal, a synchronization process with the target base station; and

confirming, by the terminal, that synchronization with the target base station succeeds.

3. The method according to claim 1 , further comprising:

after the receiving, by a terminal, a command message sent by a source base station, initiating, by the terminal, a random access process to the target base station before occupying the granted resource.

4. A handover device, comprising:

a transceiver, the transceiver configured to:

send a first message to a target base station, wherein the first message carries an arrival time indication of a terminal, and wherein the arrival time indication is used to indicate a time at which or a time range in which the terminal is to access the target base station; and

receive a second message fed back by the target base station, wherein the second message carries a granted resource that is allocated for the arrival time indication of the terminal; and

at least one processor, the at least one processor configured to:

add the granted resource to a command message; and

send the command message to the terminal by using the transceiver wherein the second message and the command message further carry a maximum quantity of transmission times that is configured for the granted resource by the target base station, and wherein a value of the maximum quantity of transmission times is set to 1.

5. The device according to claim 4 , wherein the first message is a handover request message, and wherein the second message is a handover request acknowledgement message.

6. The device according to claim 4 , wherein the first message is a secondary base station addition request message, and wherein the second message is a secondary base station addition request acknowledgement message.

7. The device according to claim 6 , wherein at least one of:

the secondary base station addition request message is a dual-link addition request message, and the secondary base station addition request acknowledgement message is a dual-link addition request acknowledgement message; and

the secondary base station addition request message is a multi-link addition request message, and the secondary base station addition request acknowledgement message is a multi-link addition request acknowledgement message.

8. The device according to claim 4 , wherein the arrival time indication is obtained by the at least one processor by performing handover decision, dual-link addition decision, or dual-link addition decision after the transceiver receives a measurement report sent by the terminal.

9. The device according to claim 4 , wherein the arrival time indication is obtained by the at least one processor by a prediction based on a synchronization delay of the terminal in relation to the target base station and configuration information of the device and the target base station.

10. The device according to claim 4 , wherein when adding the granted resource to the command message, the at least one processor is configured to:

add the granted resource to an RRC connection reconfiguration message.

11. The device according to claim 4 , the at least one processor is further configured to, before the transceiver sends the first message to the target base station:

add a resource grant cancellation indication to the first message in response to determining that the terminal has at least two target base stations, wherein the resource grant cancellation indication is used to instruct the target base station not to allocate any granted resource for the arrival time indication.

12. The device according to claim 4 , wherein the granted resource comprises an available uplink resource block.

13. User equipment comprising at least one processor and a transceiver connected to the at least one processor, wherein

the at least one processor is configured to process a message received or transmitted by the transceiver; and

the transceiver is configured to:

receive a command message sent by a source base station, wherein the command message carries a granted resource that is allocated by a target base station to the user equipment, wherein the command message further carries a maximum quantity of transmission times that is configured for the granted resource by the target base station, and wherein a value of the maximum quantity of transmission times is set to 1;

send a radio resource control (RRC) connection reconfiguration complete message to the target base station on the granted resource, wherein the RRC connection reconfiguration complete message is used to indicate to the target base station that the user equipment is successfully handed over to, dual-linked to, or multi-linked to the target base station; and

after sending the RRC connection reconfiguration complete message to the target base station on the granted resource, initiate a random access process to the target base station when the configured maximum quantity of transmission times for the granted resource is reached and the user equipment receives a negative feedback message indicating that signaling transmission on the granted resource fails.

14. The user equipment according to claim 13 , wherein the at least one processor is further configured to:

before the transceiver sends the RRC connection reconfiguration complete message to the target base station on the granted resource:

perform a synchronization process with the target base station; and

confirm that synchronization with the target base station succeeds.

15. The user equipment according to claim 14 , wherein the at least one processor is further configured to:

after the transceiver receives the command message carrying the granted resource and sent by the source base station, initiate a random access process to the target base station before the granted resource is occupied.