Early data transmission methods and communication device for early data transmission using a message 3 (MSG3)

A communication device, comprising:

• a processor;
• a transceiver;
• and
• a memory configured to store computer programs, wherein
• the processor is configured to invoke and execute the computer programs stored in the memory to:
• cause the transceiver to transmit an uplink message, wherein the uplink message comprises a first message 3 (MSG3) for accessing a first cell, and the first MSG3 comprises uplink early data stored in non-access stratum (NAS) information, or the uplink message comprises the first MSG3 for accessing the first cell and the uplink early data;
• wherein the first MSG3 carries indication information, and in a case where a serving cell of a terminal device is reselected from a second cell to the first cell and the terminal device has transmitted a second MSG3 for accessing the second cell and fails to receive a reply message 4 (MSG4) for the second MSG3, the indication information indicates that the uplink early data is retransmission data, wherein
• wherein the uplink message is used to cause an access network device to transmit a first message to a core network device to cause the core network device to reserve or discard the uplink early data based on the indication information and a determination of whether the uplink early data is stored before the uplink early data is received, and the first message comprises the uplink early data and the indication information.

A data transmission method, comprising:

• receiving, by a core network device, a first message, wherein the first message comprises uplink early data and indication information, and in a case where a serving cell of a terminal device is reselected from a second cell to a first cell and the terminal device has transmitted a second message 3 (MSG3) for accessing the second cell and fails to receive a reply message 4 (MSG4) for the second MSG3, the indication information indicates that the uplink early data is retransmission data;
• determining, by the core network device, whether the uplink early data is stored before the uplink early data is received, when the indication information indicates that the uplink early data is retransmission data;
• and
• reserving or discarding, by the core network device, the uplink early data based on a determination of whether the uplink early data is stored.