GPRS learning-sgsn, ggsn, PCU

To implement GPRS services, three new logical network entities need to be introduced in the existing GSM network: Service GPRS Support Node (sgsn) and Gateway GPRS Support Node (ggsn) and Group Control Unit (PCU)
Sgsn: Service GPRS Supporting Node
Ggsn: Gateway GPRS Supporting Node
PCU: Packet Control Unit
GSN (GPRS Supporting Node) is the GPRS Support contact, which is the mostImportant. GSN has the mobile Routing Management function. It can connect to various types of data networks and connect to GPRS registers. GSN can complete data transmission and format conversion between mobile platforms and various data networks. GSN can be an independent device similar to a router or integrated with MSC in GSM.

There are two types of GSN: sgsn (serving GSN) and ggsn (Gateway GSN ). The main function of sgsn is to record the current location information of the Mobile Station, and send and receive the Mobile Group data between the mobile station and ggsn. Ggsn serves as a gateway and can be connected to different data networks, such as ISDN, pspdn, and LAN. In some documents, ggsn is called a GPRS router. Ggsn can convert the GPRS packet packets in the GSM network to send the packets to the remote TCP/IP or X.25 network.

In the BSS (Base Station Subsystem), the BSC (Base Station Controller) includes a group control unit (PCU packet control unit) that supports communication protocols for all GPRS air interfaces. PCU functions include creating, monitoring, and removing group and exchange calls, manages grouping, segmentation and planning, wireless channels, transmission error detection, automatic resend, channel coding scheme, quality control, and power control, it also supports cross-region switchover, radio resource configuration, and channel pointing. PCU can be used as a BSc plug-in card or independently. Since there is no common interface protocol between PCU and BSC, it is necessary for various manufacturers to install PCU on the BSC to implement GPRS.