PMM-CONNECTED状态下，MS发生了位置变化,监测什么信令可以获得UE的小区级位置？

蓉城喜鹊

手机与SGSN的通信时，NAS层信令不会上报CID。RNC与SGSN之间使用RANAP信令时，只会通过LAC/RAC/SAI （service area identifier）来标识手机的位置信息。
因此在SGSN上看不到手机的CID，只能看到服务区标识SAI。

不过在RNC上可以看到手机所处的小区，因此只能监测Radio Bearer的空口信令才能找到小区ID。

部分参考信息如下：

SAC即Service Area Code，是基于一些服务义务来定义的位置区域，SAC可以包含一个或多个cell，跟LAC没有必然联系。

SAC:Service Area Code
SAI:Service Area Identifier

SAI=PLMNID+LAC+SAC

有一个用途是标识终端位置，用于Location Service。

The Service Area Identifier (SAI) is used to identify an area consisting of one or more cells belonging to the same Location Area. Such an area is called a Service Area and can be used for indicating the location of a UE to the CN.

The Service Area Code (SAC) together with the PLMN-Id and the LAC will constitute the Service Area Identifier.

- SAI = PLMN-Id + LAC + SAC

The SAC is defined by the operator, and set in the RNC via O&M. For syntax description and the usage of this identifier in RANAP signalling, see 3GPP TS 25.413. 3GPP TS 25.423 and 3GPP TS 25.419 define the usage of this identifier in RNSAP and SABP signalling.

A cell may belong to one or two Service Areas. In the case that it belongs to two Service Areas, one is applicable in the BC domain and the other is applicable in both the CS and PS domains.

The broadcast (BC) domain requires that Service Area consist of one cell. This does not limit the usage of Service Area for other domains. Refer to 3GPP TS 25.410 for a definition of the BC domain.