GPRS uses several interfaces to connect its core network elements and allow communication with external networks. The key interfaces include Um between the mobile station and GPRS network, Gb between the SGSN and BSS, Gn between SGSNs in the same network, Gp between SGSNs in different networks, and Gi between the GGSN and external data networks like the Internet. GPRS interfaces allow packet-switched connectivity and use protocols like GTP for tunneling within the core network.

1. GPRS INTERFACES
Presented By-
Ritayan Bandyopadhyay. (ECE-3B-
85)

2. General Packet Radio Service (GPRS)
What is GPRS?
 Bearer service for GSM.
 Packet-switched.
 Can inter-operate with other packet-switched
networks. (e.g. IP, X.25)
 Higher data-rates and lower connection times
than conventional GSM.

4. GPRS INTERFACE
 Within the GPRS core network standards there are a number
of interfaces and reference points (logical points of connection
which probably share a common physical connection with
other reference points). Connections from the GPRS system to
the NSS part of the GSM network are implemented through the
SS7 network. The GPRS element interfacing with the NSS is
SGSN. The important interfaces to the NSS are the SGSN-
HLR (Gr), SGSN-EIR (Gf) and SGSN-MSC/VLR (Gs). The
other interfaces are implemented through the intra-PLMN
backbone network (Gn), the inter-PLMN backbone network
(Gp), or the external networks (Gi).The next slide will show the
logical architecture with the interfaces and reference points of
the combined GSM/GPRS network.

6. The interfaces used by the GPRS system
 Um between an MS and the GPRS fixed network part.
The Um is the access interface the MS uses to access the
GPRS network. The radio interface to the BTS is the
same interface used by the existing GSM network with some
GPRS specific changes.
 Gb between a SGSN and a BSS. The Gb interface carries
the GPRS traffic and signalling between the GSM radio
network (BSS) and the GPRS network. Frame Relay
based network services is used for this interface.

7.  Gn between two GSNs within the same PLMN. The
Gn provides a data and signalling interface in the Intra-
PLMN backbone. The GPRS Tunnelling Protocol
(GTP) is used in the Gn (and in the Gp) interface over
the IP based backbone network.
 Gp between two GSNs in various PLMNs. The Gp
interface provides the same functionality as the Gn
interface, but it also provides, together with the BG and
the Firewall, all the functions needed for inter-PLMN
networking, that is, security, routing, etc.
The interfaces used by the GPRS system

8.  Gr between an SGSN and the HLR. The Gr gives the
SGSN access to subscriber information in the HLR.
The HLR can be located in a different PLMN than
the SGSN (MAP).
 Ga between the GSNs and the CG inside the same
PLMN. The Ga provides a data and signalling
interface. This interface is used for sending the charging
data records generated by GSNs to the CG. The protocol
used is GTP', an enhanced version of GTP.
The interfaces used by the GPRS system

9.  Gs between a SGSN and a MSC. The SGSN can send
location data to the MSC or receive paging requests from
the MSC via this optional interface. The Gs interface will
greatly improve the effectiveness of the radio and network
resources in the combined GSM/GPRS network. This
interface uses BSSAP+ protocol.
 Gd between the SMS-GMSC and an SGSN, and
between SMS-IWMSC and an SGSN. The Gd
interface is available for more efficient use of the SMS
services (MAP).
The interfaces used by the GPRS system

10.  Gf between an SGSN and the EIR. The Gf gives the
SGSN access to GPRS user equipment information.
The EIR maintains three different lists of mobile
equipment: black list for stolen mobiles, grey list for
mobiles under observation and white list for other mobiles
(MAP).
 Gc between the GGSN and the HLR. The GGSN
may request the location of an MS via this optional
interface. The interface can be used if the GGSN needs
to forward packets to an MS that is not active.
The interfaces used by the GPRS system

11.  Gs Interface between the SGSN and the MSC (VLR).
Uses the BSSAP+ protocol. This interface allows
paging and station availability when it performs data
transfer. When the station is attached to the GPRS
network, the SGSN keeps track of which routing area
(RA) the station is attached to. An RA is a part of a
larger location area (LA). When a station is paged this
information is used to conserve network resources. When
the station performs a PDP context, the SGSN has the
exact BTS the station is using.
The interfaces used by the GPRS system

12.  Ge The interface between the SGSN and the service
control point (SCP); uses the CAP protocol.
 Gi IP based interface between the GGSN and a public
data network (PDN) either directly to the Internet or
through a WAP gateway.
 Gmb The interface between the GGSN and the
Broadcast-Multicast Service Center (BM-SC), used for
controlling MBMS bearers.
The interfaces used by the GPRS system

13.  Lg The interface between the SGSN and the Gateway
Mobile Location Center (GMLC), used for location
based services.
 S6d The interface between SGSN and Home
Subscriber Server (HSS).It is a diameter based
interface which is used for transferring subscription and
authentication data of the user to HSS for authenticating
and authorizing user access.
 Iu Interface between the Radio Network Controller and
the SGSN. The interface exchanges signaling and
payload.
The interfaces used by the GPRS system

14.  Gx The on-line policy interface between the GGSN and
the charging rules function (CRF). It is used for
provisioning service data flow based on charging rules.
Uses the diameter protocol.
 Gy The on-line charging interface between the GGSN
and the online charging system (OCS). Uses the diameter
protocol (DCCA application).
 Gz The off-line (CDR-based) charging interface between
the GSN and the CG. Uses GTP'.
The interfaces used by the GPRS system