在3G网络中，CN在3gpp里是这样定义的：The PLMN infrastructure is logically divided into a Core Network (CN) and an Access Network (AN) infrastructures, as defined in TS 23.101 [11a] and TS 23.110 [11b]. The CN is logically divided into a CS domain, a PS domain and an IM subsystem。
CN 英文Core Network 中文解释：核心网
CS 英文Circuit Switched中文解释：电路交换
PS 英文Packet Switched 中文解释：数据交换
IMS 英文IP Mulitmadia Subsystem 中文解释：IP多媒体子系统
The CS domain refers to the set of all the CN entities offering “CS type of connection” for user traffic as well as all the entities supporting the related signalling. A “CS type of connection” is a connection for which dedicated network resources are allocated at the connection establishment and released at the connection release.
The entities specific to the CS domain are: MSC, GMSC, VLR. All the other CN entities defined in clause “4 The basic entities of the mobile system” and not defined as PS domain specific entities (see following subclause) are common to the CS and to the PS domains.
