2G/3G Network Nodes
The following graph shows the 2G/3G Network Architecture. It includes the SGSN, GGSN, HLR, CG, PDN, RNC, and BSC.
- The SGSN refers to (Serving GPRS Support Node), and it keeps track of the location of the user equipment (UE). Also, it manages its mobility between different locations without affecting its data session.
- In addition, the SGSN performs security functions and access control for the users. This means it prevents unauthorized users from accessing the network.
- The GGSN refers to (Gateway GPRS Support Node), it provides inter-networking between the GPRS network and the packet data network (PDN).
- The HLR refers to (Home Location Register).
- The HLR contains subscription information of the users, like which networks the user should be able to access, and the QoS the user has subscribed.
- The CG refers to (Charging Gateway). It collects charging records from the SGSN and the GGSN. Those charging records are named the CDRs, which refers to 'Call Detail Records'.
- Then, the CG uses those CDRs in order to charge the users depending on their usage.
- The PDN refers to (Public Data Network). the PDN is the network the users connect to, whether it is the internet or any other network.
- The GPRS network transfers data transparently between the user equipment (UE), and the packet data network (PDN).
- The RNC refers to (Radio Network Controller), and it controls the 3G sites.
- The 'NodeB' is the name of the 3G sites.
- The BSC refers to (Base Station Controller). The BSC controls the 2G sites.
- The 'BTS' is the name of the 2G sites.
2G/3G Network Interfaces
Now we know the nodes that exist in the 2G/3G network. Let's learn the interface names that exist between those nodes. Every interface between two network nodes has a unique interface name, and this interface represents the protocols that the nodes are using in the communication between each other.
- The Gn interface is the interface between the SGSNs and the GGSNs, that exist within the same network.
Later, we will go deeper into Gn interface.
- The Ga interface is the interface between the GSNs (the SGSNs and the GGSNs), and the CG.
- The GSNs use the Ga interface to send the CDRs to the CG, in order for the CG to start charging the users.
- The Gi interface is the interface between the GGSN and the PDN.
- The Gr interface is the interface between the SGSN and an HLR.
- The SGSN uses the Gr interface to get the subscription data of a certain user from the HLR, and to update the HLR with the location information of the user.
Later, we will go deeper into Gr interface.
- The Gb interface is the interface between the SGSN and the BSC.
Later, we will go deeper into Gb interface.
- The Iu interface is the interface between the SGSN and the RNC.
Later, we will go deeper into Iu interface.