This presentation covers: 1. Evolution of UMTS core network 2. Different 3GPP releases up gradation to UMTS architecture 3. UMTS Core network elements 4. Protocols used in UMTS core networks 5. MSC server and MGW 6. IMS architecture

1. UMTS CORE
NETWORK and its
EVOLUTION
By: Naveen Jakhar, ITS

2. 3G Vision
 Multimedia (voice, data & video)
 Increased data rates
384 kbps while moving
2 Mbps when stationary at specific locations
 Increased capacity (more spectrally efficient)
 IP architecture
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3. Core Network
 The Core Network is divided in circuit switched and packet switched
domains.
 Some of the circuit switched elements are Mobile services Switching
Centre(MSC), Visitor location register (VLR) and Gateway MSC. Packet
switched elements are Serving GPRS Support Node (SGSN) and Gateway
GPRS Support Node (GGSN).
 Some network elements, like EIR, HLR, VLR and AUC are shared by both
domains

4. 3GPP Release 99

5. • Figure shows the UMTS architecture as specified in 3GPP Release
99.
• The system architecture is based on the enhanced GSM Phase 2+
core network with GPRS and a new radio network called UMTS
terrestrial radio access network (UTRAN). UTRAN is connected
with the core network by the Iu interface.
• UTRAN consists of several radio network subsystems (RNSs).
An RNS is supported by the core network.
• Each RNS consists of base stations, termed as Node B in UMTS, and
a radio network controller (RNC). The RNC is a BSC equivalent and
controls several Node Bs.
• The 3G terminals (UE) interface with UTRAN using the Uu
interface, which is a WCDMA-based radio link

6.  The core network consists of network elements to support
subscriber control and circuit and packet switching.
 The core network also supports interfaces to the external network.
 The RNCs are connected to a 3G MSC by the Iu-CS interface, which
supports circuit-switched services. Iu-CS is equivalent to the A
interface in GSM.
 The RNCs are also connected to a 3G SGSN by the Iu-PS interface,
which supports packet-switched data services. Iu-PS is equivalent to
the Gb interface in GPRS. All the new interfaces, i.e., Iub, Iur, Iu-
CS, and Iu-PS, are based on ATM.
 In UMTS, the user equipment (UE) or mobile station (MS)
comprises mobile equipment (ME) and a UMTS subscriber identity
module (USIM)

7. 3GPP Release 4
Architecture
The MSC server uses ITU-T H.248 to control the media gateway. The
ITU-T BICC (bearer-independent call control) protocol is used between
the MSC and the GMSC server The core network supports coexistence
of both UTRAN and GSM/GPRS radio access network (GERAN).

8. Figure illustrates the Release 4 architecture. As can be noticed,
the core network is evolved further and introduces changes in the CS
domain. The 3G MSC functions are divided into two parts, i.e., MSC
server and media gateways.
The MSC server contains call control and mobility management logic.
The MSC server also contains a VLR to hold mobile subscriber service
data.
The media gateway contains the switching function and is controlled
by the MSC server. MGW terminates the bearer channels from the
circuit-switched network. The same applies to the GMSC server,
which is split into GMSC server and media gateway.

9. Separating the call control and physical interfaces has distinct
advantages.
 It offers scalability and lower cost. Moreover, the information
transfer between MS server, media gateways and other
components are IP based. Therefore, many components in the
core network, including SGSN, GGSN, and MSC server, can be
hooked up on the intra PLMN IP backbone, taking advantage of
shared and cheaper IP transport.
The basic principle is that the MSC is split into an MSC server and a
(Circuit - Switched) Media Gateway (CS-MGW), the external
interfaces remaining the same as much as possible as for a
monolithic MSC. The MSC server provides the call
control and mobility management functions, and the CS-MGW
provides the stream manipulating functions, i.e. bearer control
and transmission resource functions.

10. The Fig. explains the Bearer Independent
Call Control Architecture

11. The MSC Server comprises all the call control and mobility control parts of
an MSC. As such, it is responsible for the control of mobile originated and
mobile terminated CS domain calls .
It terminates the network signaling and translates it into the relevant
network to network signaling. It also contains the VLR. The MSC Server
controls the parts of the call state that pertain to connection control for
media channels in a CS-MGW.
A GMSC Server is to a GMSC as an MSC Server is to an MSC CS-MGW.A
GMSC Server is to a GMSC as an MSC Server is to an MSC.
Circuit Switched -Media Gateway (CS- MGW) The CS-MGW interfaces the
transport part of the UTRAN/BSC with the one of the core network, over
Iu or the A interface.

12.  It interacts with the (G) MSC server for resource control. A CS-MGW may
also terminate bearer channels from a circuit switched network and
media streams from a packet network (e.g., RTP streams in an IP
network).
 As the entity interfacing the access and the core network, the CS-MGW
operates the requested media conversion (it contains e.g. the TRAU), the
bearer control and the payload processing (e.g. codec, echo canceller,
conference bridge). It supports the different Iu options for CS services
(AAL2/ATM based as well as RTP/UDP/IP based).
 The CS-MGW bearer control and payload processing capabilities also
need to support mobile specific functions such as SRNS
relocation/handover and anchoring. Current H.248 standard
mechanisms are applied to enable this.
 Further tailoring (i.e packages) of the H.248 may be required to support
additional codecs and framing protocols, etc

13. 3GPP Release 5 Architecture

14. The salient point for this architecture is that it is all IP based. The voice is
over IP, and hence there is no need of circuit switching within PLMN. At
the gateway, appropriate conversion is required to
interconnect to legacy systems.
The SGSN and the GGSN are enhanced to support
circuit-switched services such as voice. The new roaming signaling
gateway (RSGW) and transport signaling gateway (T-SGW) are needed to
provide interworking with the external system over legacy SS7 and SS7-
over-IP.
The call state control function (CSCF) provides call control functions for
multimedia sessions. The media gateway control function (MGCF)
controls media gateways, which are IP multimedia subsystems. The
media resource function (MRF) supports features such as multiparty
conferencing and "meet me."

15. The objective of release 5 Architecture was to support applications involving
multiple media components per session in such a way that the network is able to
dissociate different flows with potentially different QoS characteristics associated
to the multimedia session. These applications are called IP Multimedia
applications (or "services").
Examples of such applications are multimedia session
offering the possibility to add and drop component(s) such as video, audio, end
users, or tools as shared online whiteboards. The impact on the network is the
creation of a set of new entities dedicated to the handling of the signalling and
user traffic flows related to these applications. This set is called the "IP
Multimedia CN subsystem" (IMS).
All IMS entities are located in the Core
Network. The fixed Internet multimedia call control "Session Initiated Protocol"
(SIP) defined by IETF is chosen as IMS main protocol for its flexible syntax and as
to facilitate development and interconnectivity between 3GPP networks and fixed
IP networks.

16. IMS architecture
RNC
P-CSCF
I-CSCF
MRF
IMS
S-CSCF
MSC(Server)
SGSN
GGSN
CN
MGW
BSC
GSM/GPRS/WCDMA/HSDPA
WLAN
Corporate
SIP Application
ServersSIP Application
Servers
HSS
CDMA 2000
Fixed
IMS – a cornerstone for Convergence
HLR

17. IMS paved an evolutionary path towards an all-IP core and is the
core controller of choice for long term evolution (LTE) networks
offering VoLTE and multimedia services. IP Multimedia Subsystem
(IMS) offers a standardized, futureproof
network architecture with open interfaces, guaranteeing
interoperability in multivendor environments with maximum
reuse of existing network gear.
IMS Key Elements:
Proxy-Call State Control Function (P-CSCF):this is the
“first contact point” of IMS. It is located in the same
network as the GGSN (visited or home network,
shown as being in the visited network in the figure above).
Interrogating-CSCF (I-CSCF): this is the “main entrance”
of the home network. it
selects (with the help of HSS) the appropriate S-CSCF
Serving-CSCF (S-CSCF): it performs the actual Session
Control:

18. R6 Architecture
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CS-Domain
-or-
PSTN
-or-
Legacy
-or-
External
PS-Domain
CSCF
MRF-C
CAP
Mr
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Mm
Mw
Mn
Gc
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Gn
Iu
BGCF
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Dx
„Mb/Gi-Cloud“
PDF MRF-P
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ISC
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Operator 2
Si
IMS Terminal
UTRAN /
GERAN
Multimedia
IP
Networks
MGCF
MGW
IP Multimedia
Subsystem (IMS)
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Applications
Services
AS
OSA-SCS
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Dh
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WLAN
Access,
WAG
AAA
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WLAN
(Home)
Wu, Wp
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19. 3G Network Components
 Circuit Core ( Voice Services)
 MSC Server
 Media Gateway
 Home Location Register (HLR)
 Packet Core ( Data Services)
 GGSN
 SGSN
 Radio ( Coverage &
connectivity)
 RNC
 Node B
– Transmission
▪ IP/ MPLS
▪ SDH
▪ E1
– Value Added Services
▪ SMSC ( Short Message Service
Centre )
▪ VMS ( Voice Mail Service )
▪ Streaming etc……
– Subscriber Equipment
▪ Handset
▪ USIM

20. Core Network
Elements
Circuit Switched
Mobile Switching Centre-Server (MSC-S)
Media Gateway (MGW)
GMSC-S and GMGW
Home Subscriber Server (HSS)
Equipment Identity Register (EIR)
Packet Switched
Gateway GPRS Support Node (GGSN)
Serving GPRS Support Node (SGSN)
Border Gateway Router (BGR)
GPRS Roaming Exchange (GRX)
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21. Interfaces and Protocols
C/ D interface: It is the interface between MSC – HLR/FNR
and protocol used is MAP.
F interface: It is the interface between MSC – EIR and protocol
used is MAP.
MSC
server
HSS
HLR AuC FNR
HSS
HLR AuC FNRHLR EIR FNR
C/D/F
NTIPRIT

22. Interfaces and Protocols
MSC
server
Media
Gateway
Mc
WCDMA
Radio
Network Iu- RANAP
GSM
Radio
Network
A -
BSSAP
HSS
HLR AuC FNR
HSS
HLR AuC FNRHLR EIR FNR
C/D/F
IN
L-INAP/CAP
NTIPRIT

23. Interfaces and Protocols
L interface: It is the interface between MSC – IN
nodes and protocol used is INAP/ CAP.
Iu interface: It is the interface between MSC –
RNC and protocol used is RANAP.
A interface: It is the interface between MSC –
BSC and protocol used is BSSAP.
NTIPRIT

24. PSTN
ISDN
Internet
Intranet
Packet Backbone Network
MGw
Mgw
SGSN
CSCF
GMSC
Server
MSC
Server
MSC
Server
HSS
HLR AuC FNR
MAP
MAP
BICC
H.248
RANAP
MGCF
SIP
RNC
BSC
BICC
Gn
BSSAP
RANAP
Q.AAL2
GGSN
PSTN
ISDN
Internet
Intranet
Packet Backbone Network
MGwMGw
MGW
SGSNSGSN
CSCF
GMSC
Server
GMSC
Server
MSC
Server
MSC
Server
MSC
Server
MSC
Server
HSS
HLR AuC FNR
HSS
HLR AuC FNR
MAP
MAP
BICC
RANAP
MGCF
SIP
RNCRNC
BSC
BICC
Gn
BSSGP
RANAP
Q.AAL2
Core Network Protocols
NTIPRIT

25. Circuit Switched Domain
Protocols
Just as the horizontally integrated network
model demands the splitting of nodes into
Servers and Media Gateways, there is also
need for separation of control protocols into
call control and bearer control
Control Protocols
Call Control
Protocols
Bearer Control
Protocols
NTIPRIT

26. At the control layer, there are two main
requirements:
•The control servers (MGC) must be
able to control remote MGWs
• Control servers must be able to
communicate call requirements to each
other so that calls may be set up end-to
end.
Circuit Switched Domain
Protocols
NTIPRIT

27. MSC GMSC
HLR
MGW
MGW
MGW
MGW
Control Layer
Connectivity Layer
H.248
H.248
H.248
BICC
Call Control
MAP MAP
Q.2630 Bearer Control
AAL2 bearer/connectivity network
Protocols used in Mobile core
Network
NTIPRIT

28. Access Control Protocol
Circuit Switched Domain
Protocols
The control servers in the core network are responsible
for various aspects of communication with UE, Radio
network controllers and external networks.
BSSAP, RANAP, DTAP and ISUP are used.
NTIPRIT

29. Access Control Protocol
Circuit Switched Domain Protocols
•For GSM radio access the Core Network re-uses Base
Station System Application Part (BSSAP) to allow the
MSC servers to control BSCs.
•For WCDMA, the Core Network uses Radio Access
Network Application Part (RANAP) to allow the MSC
servers to control RNCs.
NTIPRIT

30. Access Control Protocol
Circuit Switched Domain Protocols
MSC GMSC
HLR
MGW
MGW
MGW
MGW
Control Layer
Connectivity Layer
H.248
H.248
H.248
BICC
Call Control
MAP MAP
AAL2 bearer/connectivity network
BSC
BSSAP
RNC
RANAP
ISUP
ISDN/PSTN
NTIPRIT