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ITU-T Focus Group IMT-2020 Deliverables 5

A.3 2G/3G

SMS-GMSC
SMS-IWMSC SM-SC

E C CAMEL GSM-
Gd SCF

MSC/VLR HLR
D Ge
Gs
A Iu Gr Gc
R Uu Iu Gi
TE MT UTRAN SGSN GGSN PDN TE
Gn
Gb Ga Ga
TE MT BSS Gn Gp
R Um CGF Billing
System
GGSN
SGSN Gf EIR
Other PLMN

Signalling Interface
Signalling and Data Transfer Interface

Figure A-3 – 2G/3G Logical Architecture
The architecture of 2G/3G Logical Architecture is described in Figure A-3. The 2G/3G Packet Switched
Network functionality is logically implemented on two network nodes, the SGSN (Serving GPRS Support
Node) and the GGSN (Gateway GPRS Support Node).

A GPRS Support Node (GSN) contains functionality required to support GPRS functionality for GERAN and/or
UTRAN. The GGSN is the node that is accessed by the packet data network. It contains routeing information
for PS-attached users. The routeing information is used to tunnel N PDUs to the MS's current point of
attachment, i.e. the Serving GPRS Support Node. The GGSN is the first point of PDN interconnection with a
PLMN supporting GPRS. GGSN functionality is common for all types of RANs.

The SGSN is the node that is serving the MS. The SGSN supports GPRS for A/Gb mode and/or Iu-mode. At PS
attach, the SGSN establishes a mobility management context containing information pertaining to e.g.
mobility and security for the MS. At PDP Context Activation, the SGSN establishes a PDP context, to be used
for routing purposes, with the GGSN that the subscriber will be using.
When the SGSN and the GGSN are in different PLMNs, they are interconnected via the Gp interface. The Gp
interface provides the functionality of the Gn interface, plus security functionality required for inter-PLMN
communication. The security functionality is based on mutual agreements between operators.

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