Data transmission methods and communication device

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 the indication information indicates whether the uplink early data is retransmission data.

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, the indication information indicates whether 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.