P-TMSI signature的作用

heropoet

请问P-TMSI signiture的作用是什么?
根据24.008 4-7-1-3 有以下介绍:
The network may assign a P-TMSI signature to an MS in an attach, routing area update, or P-TMSI reallocation procedure. Only in combination with a valid P-TMSI, this P-TMSI signature is used by the MS for authentication and identification purposes in the subsequent attach, routing area update or detach procedure.
这里说P-TMSI signature是MS用于在随后的att或rau等中鉴权和识别的目的,但具体是怎么使用这个P-TMSI signature?还是不解,望请各位解答.