What is SGSN? What is the corresponding physical medium?

SGSN is the abbreviation of English Serving GPRS SUPPORT NODE. As an important part of the packet domain equipment of GPRS/TD-SCDMA(WCDMA) core network, SGSN mainly completes the functions of packet routing and forwarding, mobility management, session management, logical link management, authentication and encryption, and ticket generation and output.

SGSN is a GPRS service support node, which provides connection with PCU through Gb interface and manages mobile data, such as user identification, encryption, compression and other functions. Connect with HLR through Gr interface to access and control user database; It is also connected with GGSN through Gn interface, which provides transmission path and protocol conversion between IP packets and wireless units. SGsN can also provide GS interface connection with MSC and Gd interface connection with SMSC to support the cooperative work of data service and circuit service as well as the short message receiving and sending function.

SGSN cooperates with GGSN to undertake PS function of TD-SCDMA(WCDMA). As a basic part of GPRS network, it is connected with BSS through Gb interface. Its main function is to manage the mobility of the MS in the service area of the SGSN and forward input/output IP packets, which is similar to VMSC in GSM circuit network. In addition, the function similar to VLR in GSM network is integrated in SGSN. When the user is in GPRS connection (GPRS state), the user information and location information related to the data packet are stored in SGSN. As the PS domain function node of TD-SCDMA(WCDMA) core network, SGSN is connected with UTRAN through Iu_PS interface, which mainly provides the functions of routing and forwarding, mobility management, session management, authentication and encryption in PS domain. GGSN98 1 1 mainly provides the interface between PS and external PDN (packet data network) and assumes the function of gateway or router. SGSN and GGSN are collectively referred to as GSN(GPRS Support Node).

I only found these for you, but I don't know about physical media. sorry