Register method in cell and terminal device

A registration method implemented by a terminal device, comprising:

• sending a first request requesting to register in a first cell;
• receiving, in response to the first request, a first message indicating that the terminal device is successfully registered in the first cell;
• sending, in response to the first message, a second request requesting to register in a second cell when the first message does not carry a first network slice identifier or when the first message carries the first network slice identifier and the terminal device cannot establish a protocol data unit (PDU) session on a first network slice corresponding to the first network slice identifier, wherein the second cell is different from the first cell;
• receiving, in response to the second request, a second message carrying a second network slice identifier;
• and
• establishing, in response to the second message, the PDU session on a second network slice corresponding to the second network slice identifier.