The H interface is used for communicating
with the Short Message Service Center (SMSC), used for managing short
messaging services in the network.
Figure 1.9 IMS reference points in wireline and wireless
P-CSCF P-CSCF
I-CSCF
HSS
SLF
HSS
SLF
MGCF BGCF
MG MG
SWT SWT
S-CSCF S-CSCF
I-CSCF
STP
SG
MRFP MRFC MRFC MRFP
MSC
HLR
VLR
GGSN
SGSN
SGSN
BSS
Mp Mp
Cx
Cx
Dx
Dx
Gm
AS
ISC
Mg
Mi
Mj
Mr
Mw
Mw Mw
Mw
Sh Mr
24 Chapter 1
The GPRS interfaces are identified by a G followed by a lowercase letter. The GPRS
protocol is used over these interfaces. Basically, the GPRS overlay adds two additional
functions to the network for the purpose of packet switching. The Serving GPRS
Support Node (SGSN) provides packet connections from the BSC via the Gs interface,
connecting to other SGSNs in the same network via the Gn interface.
When connecting to packet services outside of the network (such as another GPRS
network, or the public Internet), the SGSN interfaces to a Gateway GPRS Support Node
(GGSN) via the Gp interface. The GGSN interfaces to other wireless GPRS networks
via the Gp interface. The Gi interface provides access into another packet network. The
Gm interface provides access to a P-CSCF in the IMS domain.
The UMTS interfaces identify additional radio bandwidth for supporting broadband
cellular services. All UMTS reference points begin with the letter I followed by a lowercase
u and one or two additional letters.
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