Method for handover to relay node, related device, and system
A method for handover to a relay node, a related device, and a system, where the method includes sending, by a base station of a target cell in an initial random access procedure initiated by a terminal device for the target cell, indication information to the terminal device using a random access message to instruct the terminal device to report information about a candidate relay device corresponding to the terminal device, receiving the information about the candidate relay device from the terminal device determining, in the candidate relay device according to the information about the candidate relay device, a target relay node used for relay communication between the terminal device and the base station, and handing over the terminal device to the target relay node.
1. A network device, comprising:
a transmitter;
a receiver; and
a processor coupled to the transmitter and the receiver and configured to:
send, using the transmitter in an initial random access procedure initiated by a terminal device for a target cell, indication information to the terminal device using a first random access message to instruct the terminal device to report information about a candidate relay device corresponding to the terminal device;
receive, using the receiver, the information about the candidate relay device from the terminal device;
determine, in the candidate relay device according to the information about the candidate relay device, a target relay node used for relay communication between the terminal device and the network device; and
hand over the terminal device to the target relay node.
2. The network device of claim 1 , wherein the indication information is carried in at least one of the following messages:
a random access response; or
a contention resolution message.
3. The network device of claim 2 , wherein the information about the candidate relay device is carried in at least one of the following messages:
a random access message 3, a Radio Resource Control (RRC) connection setup complete message, or an uplink message following the RRC connection setup complete message when the indication information is carried in the random access response or is carried in the random access response and the contention resolution message; and
the RRC connection setup complete message or the uplink message following the RRC connection setup complete message when the indication information is carried in the contention resolution message.
4. The network device of claim 2 , wherein the indication information is carried in at least one of the random access response or the contention resolution message, and wherein the processor is further configured to:
receive, using the receiver, a random access preamble; and
identify a device type of the terminal device by using the random access preamble.
5. The network device of claim 4 , wherein the processor is further configured to identify the device type of the terminal device using a Physical Random Access Channel (PRACH) resource carrying the random access preamble.
6. The network device of claim 2 , wherein the indication information is carried in the contention resolution message, and wherein the processor is further configured to:
receive, using the receiver, a message 3; and
identify a device type of the terminal device using a message 3, wherein the message 3 carries information about the device type of the terminal device.
7. The network device of claim 4 , wherein the processor is further configured to send, using the transmitter, the indication information to the terminal device using a second random access message under a condition that the device type of the terminal device is a specified device type.
8. The network device of claim 1 , wherein the information about the candidate relay device comprises identification information of the candidate relay device corresponding to the terminal device and a measurement result of the candidate relay device corresponding to the terminal device.
9. A terminal device, comprising:
a transmitter;
a receiver; and
a processor coupled to the transmitter and the receiver and configured to:
receive, using the receiver in an initial random access procedure for a target cell, indication information from a base station corresponding to the target cell using a first random access message, wherein the indication information instructs the terminal device to report information about a candidate relay device corresponding to the terminal device; and
send, using the transmitter, the information about the candidate relay device to the base station in response to the indication information to enable the base station to determine a target relay node in the candidate relay device and to hand over the terminal device to the target relay node.
10. The terminal device of claim 9 , wherein the indication information is carried in at least one of the following messages:
a random access response; or
a contention resolution message.
11. The terminal device of claim 10 , wherein the information about the candidate relay device is carried in at least one of the following messages:
a random access message 3, a Radio Resource Control (RRC) connection setup complete message, or an uplink message following the RRC connection setup complete message when the indication information is carried in the random access response or is carried in the random access response and the contention resolution message; and
the RRC connection setup complete message or the uplink message following the RRC connection setup complete message when the indication information is carried in the contention resolution message.
12. The terminal device of claim 10 , wherein the indication information is carried in at least one of the random access response or the contention resolution message, and wherein the processor is further configured to indicate a device type of the terminal device using a random access preamble sent using the transmitter.
13. The terminal device of claim 12 , wherein the processor is further configured to:
indicate the device type of the terminal device using a Physical Random Access Channel (PRACH) resource carrying the random access preamble;
indicate the device type of the terminal device using a preamble format of the random access preamble; or
indicate the device type of the terminal device using a group to which the random access preamble belongs.
14. The terminal device of claim 10 , wherein the indication information is carried in the contention resolution message, wherein the processor is further configured to indicate a device type of the terminal device using a message 3 sent using the transmitter, and wherein the message 3 carries information about the device type of the terminal device.
15. The terminal device of claim 12 , wherein the indication information is received from the base station under a condition that the device type of the terminal device is a specified device type.
16. The terminal device of claim 9 , wherein the information about the candidate relay device comprises identification information of the candidate relay device corresponding to the terminal device and a measurement result of the terminal device for the candidate relay device.
17. The network device of claim 4 , wherein the processor is further configured to identify the device type of the terminal device using a format of the random access preamble.
18. The network device of claim 4 , wherein the processor is further configured to identify the device type of the terminal device using a group to which the random access preamble belongs.
19. The network device of claim 1 , wherein the information about the candidate relay device comprises identification information of a relay device having a preset pairing relationship with the terminal device.
20. The terminal device of claim 9 , wherein the information about the candidate relay device comprises identification information of a relay device that has a preset pairing relationship with the terminal device.