GPRS – Architecture
Serving GPRS Support Node (SGSN):
SGSN is one the same hierarchic level as an MSC and handles many functions comparable to a Visited MSC (VMSC):
- Is the node serving GPRS mobile stations in a region assigned to it.
- Traces the location of the respective GPRS MSs (Mobility Management functions).
- Is responsible for the paging of MS.
- Performs security functions and access control authentication cipher setting procedures).
- Has a routingitraffic-management function.
- Collects data connected with fees charges.
- Realizes the interfaces to GGSN (Gn), PCU(Gb), other PLMNs (Gp), HLR (Gr), VLR (Gs),SMS-GSMC (Gd),EIR (Gf)
Gateway GPRS Support Node (GGSN):
GGSN realizes functions comparable to those of a gateway MSC.
- Is the node allowing contact interworking between a GSM PLMN and a packet data network PDN (realization Gi-interface).
- Contains the routing information for GPRS subscribers available in the PLMN.
- Has a screening function.
- Can inquire about location information‘s from the HLR via the optional Gc interface.
- Transfers data signaling to SGSN via Gn interface.
HLR (GPRS Register GR) :
HLR includes the GPRS subscriber information (GPRS Register GR) and routing information.
Access to HLR is possible from SGSN via Gr and from GGSN via interface.
Packet Control Unit PCU:
In the BSS, the PCU serves
- For the management of GPRS radio channels (Radio Channel Management functions), e.g. power control, congestion control, and broadcast control information.
- For the temporal organization of the packet data transfer for uplink and downlink it has channel access control function, e.g. access request and grants.
- It serves for converting protocols from the Gb interface to the radio interface Um.
Channel Codec Unit CCU:
The CCU has the following functions:
- Channel coding, including forward error correction FEC and interleaving.
- Radio channel measurements, including received quality and signal level, timing advance measurements.
Terminal Equipment (TE):
TE is the computer terminal on which the end-user works. This is the component used for the GPRS system to transmit and receive end-user packet data. For example, the TE could be a laptop computer. The GPRS system provides IP connectivity between the TE and an Internet Service Provider or Corporate LAN (Local Area Network) connected to the GPRS system. From the point of view, you would compare the Mobile Terminal to a modem, connecting the GPRS system.
Mobile Terminal (MT):
The MT communicates with a TE, and over the air with a BTS. The MT must be equipped with software for GPRS functionality when used in conjunction with the GPRS system.
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