# US 12,004,033 B2 · Method for switching between access network devices, terminal device, and network device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,004,033 B2 - Document ID: US12004033B2 - Status: Granted - Kind: B2 - Application number: 17/525,508 - Filed: 2021-11-12 - Published: 2022-03-03 - Granted: 2024-06-04 - Earliest claimed: 2019-05-14 - Assignees: Guangdong Oppo Mobile Telecommunications Corp., Ltd. - Applicants: Guangdong Oppo Mobile Telecommunications Corp., Ltd. - Inventors: Xin You - Web page: https://patentgrep.com/patent/US12004033B2 ## CPC - H04W 36/0077: {of access information of target access point} - H04W 76/30: Connection release - H04L 1/08: by repeating transmission, e.g. Verdan system {(H04L1/1858 and H04L1/189 take precedence)} - H04W 36/0058: {Transmission of hand-off measurement information, e.g. measurement reports} - H04W 74/0833: Random access procedures, e.g. with 4-step access - H04W 36/0064: {of control information between different access points} - H04W 36/185: {using make before break} - H04W 36/302: {due to low signal strength} - H04W 74/0838: using contention-free random access [CFRA] - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract Disclosed are a method for switching between access network devices, a terminal device, and a network device. The method includes the terminal device initiating a random access to a target access network device while maintaining a connection with a source access network device. The method also includes the terminal device releasing the connection with the source access network device, after successfully accessing to the target access network device and in response to channel quality of the source access network device meeting a preset condition. ## Claims ### Claim 1 A method for switching between access network devices, comprising: initiating, by a terminal device, a random access to a target access network device while maintaining a connection with a source access network device; determining, by the terminal device, that the channel quality of the source access network device meets the preset condition, after successfully accessing to the target access network device; sending, by the terminal device, auxiliary information to the target access network device, wherein the auxiliary information is configured to indicate that the channel quality of the source access network device meets the preset condition; receiving, by the terminal device, response information of the auxiliary information, wherein the response information is configured to instruct the terminal device to release the connection with the source access network device; and releasing, by the terminal device, the connection with the source access network device according to the response information, wherein indication information is sent by the target access network device to the source access network device in response to receiving the auxiliary information, and the indication information is configured to indicate at least one of that: scheduling of downlink data is stopped by the source access network device; or data forwarding information is sent to the target access network device by the source access network device. ### Claim 2 (depends on 1) The method according to claim 1, wherein the determining, by the terminal device, that the channel quality of the source access network device meets the preset condition, comprises: determining, by the terminal device, that a measured value of the channel quality of the source access network device is lower than a pre-configured threshold. ### Claim 3 (depends on 1) The method according to claim 1, wherein the determining, by the terminal device, that the channel quality of the source access network device meets the preset condition, comprises: determining, by the terminal device, that a radio link failure (RLF) occurs on a link between the terminal device and the source access network device. ### Claim 4 (depends on 3) The method according to claim 3, wherein the RLF occurring on the link between the terminal device and the source access network device comprises at least one of the following situations: retransmissions of a radio link control (RLC) automatic repeat-request (ARQ) reaching a maximum number of times, multiple out-of-synchronization indications being continuously received by the terminal device, and expiry of timer T310 or timer T312. ### Claim 5 (depends on 1) The method according to claim 1, further comprising: before initiating the random access to the target access network device, receiving, by the terminal device, a handover command, wherein the handover command is configured to instruct the terminal device to switch from the source access network device to the target access network device while maintaining the connection with the source access network device. ### Claim 6 A terminal device comprising: a processor; and a memory, wherein the memory is configured to store a computer program, and the processor is configured to call and run the computer program stored in the memory to execute operations of: initiating, by the terminal device, a random access to a target access network device while maintaining a connection with a source access network device, determining, by the terminal device, that the channel quality of the source access network device meets the preset condition, after successfully accessing to the target access network device; sending, by the terminal device, auxiliary information to the target access network device, wherein the auxiliary information is configured to indicate that the channel quality of the source access network device meets the preset condition; receiving, by the terminal device, response information of the auxiliary information, wherein the response information is configured to instruct the terminal device to release the connection with the source access network device; and releasing, by the terminal device, the connection with the source access network device according to the response information, wherein indication information is sent by the target access network device to the source access network device in response to receiving the auxiliary information, and the indication information is configured to indicate at least one of that: scheduling of downlink data is stopped by the source access network device; or data forwarding information is sent to the target access network device by the source access network device. ### Claim 7 (depends on 6) The terminal device according to claim 6, wherein the determining, by the terminal device, that the channel quality of the source access network device meets the preset condition, comprises: determining, by the terminal device, that a measured value of the channel quality of the source access network device is lower than a pre-configured threshold. ### Claim 8 (depends on 6) The terminal device according to claim 6, wherein the determining, by the terminal device, that the channel quality of the source access network device meets the preset condition, comprises: determining, by the terminal device, that a radio link failure (RLF) occurs on a link between the terminal device and the source access network device. ### Claim 9 (depends on 8) The terminal device according to claim 8, wherein the RLF occurring on the link between the terminal device and the source access network device comprises at least one of the following situations: retransmissions of a radio link control (RLC) automatic repeat-request (ARQ) reaching a maximum number of times, multiple out-of-synchronization indications being continuously received by the terminal device, and expiry of timer T310 or timer T312. ### Claim 10 (depends on 6) The terminal device according to claim 6, wherein the processor is further configured to call and run the computer program stored in the memory to execute an operation of: before initiating the random access to the target access network device, receiving, by the terminal device, a handover command, wherein the handover command is configured to instruct the terminal device to switch from the source access network device to the target access network device while maintaining the connection with the source access network device. ### Claim 11 A network device comprising: a processor; and a memory, wherein the memory is configured to store a computer program, and the processor is configured to call and run the computer program stored in the memory to execute operations of: after a target access network device is successfully accessed by a terminal device while maintaining a connection with a source access network device, receiving, by the network device, auxiliary information; and sending, by the network device, response information of the auxiliary information, wherein the response information is configured to instruct the terminal device to release the connection with the source access network device, wherein the network device is the target access network device, and the processor is further configured to call and run the computer program stored in the memory to execute an operation of: sending, by the target access network device, indication information to the source access network device in response to receiving the auxiliary information, wherein the indication information is configured to indicate at least one of that: scheduling of downlink data is stopped by the source access network device; or data forwarding information is sent to the target access network device by the source access network device. ### Claim 12 (depends on 11) The network device according to claim 11, wherein the receiving, by the network device, the auxiliary information, comprises: receiving, by the network device, the auxiliary information, wherein the auxiliary information is configured to indicate that channel quality of the source access network device meets a preset condition. ### Claim 13 (depends on 12) The network device according to claim 12, wherein the auxiliary information is configured to indicate that a measured value of the channel quality of the source access network device is lower than a pre-configured threshold. ### Claim 14 (depends on 12) The network device according to claim 12, wherein the auxiliary information is configured to indicate that a radio link failure (RLF) occurs on a link between the terminal device and the source access network device. ### Claim 15 (depends on 14) The network device according to claim 14, wherein the radio link failure (RLF) occurring on the link between the terminal device and the source access network device comprises at least one of the following situations: retransmissions of a radio link control (RLC) automatic repeat-request (ARQ) reaching a maximum number of times, multiple out-of-synchronization indications being continuously received by the terminal device, and expiry of T310 or T312.