3 g core nw

© Copyright 2000 Wireless facilities, Inc. Page 1
3G Core Network
Technology Trends

Story so far
MobileMobile InternetInternet

Growth in Mobile
Communication Services
120
240
360
480
600
720
840
960
1080
1,200
0
1995 1996 1997 1998 1999 2000 2001 2002 2003
Subscribers(inmillion)
Japan
(excl. PHS)
Asia Pacific
(excl. Japan)
Latin America
Rest of the
world
North
America
Western
Europe

The New Telecom World
…. Beyond Voice

Bundling of ServicesBundling of Services
TELECOMMUNICATIONSTELECOMMUNICATIONSCOMPUTERCOMPUTER
CONVERGENCECONVERGENCE
Information ContentInformation Content
Information ServersInformation Servers
Access NetworksAccess Networks
Information AppliancesInformation Appliances
COMMERCE & BROADCATERSCOMMERCE & BROADCATERS
DELIVERY TO A WIDE RANGE OF DEVICES
OVER A COMMON CORE NETWORK

Converging industries
Computers
& Datacom
Consumer
electronics
Entertainment
& Publishing
Business
multimedia
Information
gadgets
Telecom
Home
multimedia
Information &
work support
IP

CS vs PS
Today: you go through a
circuit switch to get to a packet switch.
Tomorrow: you’ll use a packet switch
to emulate to a circuit switch.

The strategic direction
Telecom Datacom
M
obility
2G mobile
voice
Wireline
telephony
Mobile
data
WAN/LAN
data
Voice over IP
3G
(UMTS)
2G Internet
1G mobile Internet
1G Internet
3G Internet

Three important steps
Voice goes Mobile
– Home / Office Zone, GSM on the Net, Number Portability
– Separation of private / business usage and roles
Mobile Data kick-off
– WAP (SMS/USSD), SIM TK,...
– GPRS, GSM on the Net, Virtual Office,
WebOnAir, ...
New Business Concepts
– GPRS - always connected, client-server, content v.s. time
– UMTS Virtual Home Environment - networks opening up
– Bluetooth - bridging technology, e-services
– Mobile eCommerce - real time charging/billing, triple-A

Cerf’s Prediction:
By 2010, 100% of all traffic
will be packetized!
Are we ready?!

IP on Everything

It’s All About DATA!
• KEY FACTORS:
- Data Access
- Data Delivery
- Data Integration
• WIRELESS IS JUST HOW IT GETS THERE
• THE FOCUS IS THE END-TO-END SOLUTION
Services that offer Value Added Applications and
Content are of interest to the user!...

Vision 2003!
IP Virtual Private Network (VPN)IP Virtual Private Network (VPN)
PLATFORM FOR A WIDE RANGE OFPLATFORM FOR A WIDE RANGE OF
COMMUNICATIONS-BASED SERVICESCOMMUNICATIONS-BASED SERVICES
CAPACITYCAPACITY
SERVICES
SERVICES
M
O
B
ILITY
M
O
B
ILITY

The Future
The Battle of the access network is over, it is know called:
“Harmonized single global standard with several modes”
The new cry for revolution is:
“All IP-based core networks!!!”

Internet Protocol (IP)
• Routes information packets through
islands of networks
• Provides addressing information to
identify the source and destination

0 7 15 23 31
Version Type of service Total length
Identification Fragment offset
IP Datagram
IHL
D
F
M
F
Time to live Protocol Header checksum
Source address
Destination address
Options

What will IP offer?
• The convergence interface for data, voice and
multimedia applications as well as fixed and mobile
networks
• Opportunity for third party developers to add value to
a system
• Single system architecture for residential, office, fixed,
mobile environments

The Famous Questions
• Which one is better, IP or ATM?
• Wireless IP or Mobile IP? What about
Cellular IP?

How does IP work?
Physical
Network
Access
IP
Transport
(host-to-host)
Application
Physical
Network
Access
IP
Transport
(host-to-host)
Application
Communication
Networks

Future Challenges for IP
“32 bits should be enough address space for Internet”
-- Vint Cerf, 1977
• QoS
•Addressing
• Wireless
• Mobility

Once we have advanced IP,
what do we want to do with it?
• Establish a flexible service creation environment
• Enable quick service/application creation
• Ensure independence of access type
• Provide open interfaces to ensure a multi-vendor
environment
• Maintain and enhance Global Roaming

How do we get there?
• Hybrid CS and PS networks will exist in near term
• Backward compatibility is critical
• Service transparency must exist across domains
for common services

Again ...
IT’S ALL ABOUT
DATA!
WIRELESS IS JUST HOW
IT GETS THERE
• Broadband Wireless
• Cellular mobile
• Wireless LAN
+
IP +

Clients
Multi-Service Next Generation
Networks
Today
Single-service networks
LAN(Data)LAN(Data)
MobileMobile
FixedTelephonyFixedTelephony
Broadband
Wireless
Broadband
Wireless
Servers
Clients
IP Backbone Network
Access
Access
Future
Multi-service networks
Communcationi Control
Content Content
Access
Services

Evolution
HLRHLRPSTN/
ISDN
MAP
HLR Internet
GPRS
Node
BTSBTS
BSC
Voice Data
A Gb
MSCMSC
BROADBAND /
IP NETWORK
Node
B
Node
B
RNC
Data
IWUIWU
PSTN/
ISDN
LEGACY
NETWORKS
Voice
ALL-IP BASEDALL-IP BASED
NETWOKSNETWOKS
Today: You go through a CS to get to a PS
Tomorrow: You’ll go through a PS to get to a CS
2.5 G2.5 G 3 G3 G

What is GPRS?
• GSM is now in phase 2+, which consists of a large number of projects
including improved voice coding and advance data transmission
services such as high speed circuit switched data (HSCSD) and the
General Packet Radio Service (GPRS).
• The General Packet Radio Service (GPRS) is a new non-voice value
added service introduced in order to provide more efficient access to
packet data networks from cellular networks.
• It supplements today's Circuit Switched Data and Short Message
Service in GSM networks.

What is GPRS?
• Theoretical maximum speeds of up to 171.2 kbps
• Immediacy (no dial-up connection is necessary)
• Enable the Internet applications not available previously on GSM
networks
• GPRS shares GSM frequency bands with telephone and circuit
switched data traffic, and makes use of many properties of the
physical layer of the original GSM system such as
multiple access scheme (TDMA)
frame structure
modulation technique and
slot structure

Tendency toward mobile IP
IP
convergence
Telecommunication
• Transportation
• ISDN - Services
• Video calls
• Larger bandwith
Computer
• Internet
access
• Pictures
• Remote LAN
• e-mail
• voice over IP
Media
• Music
• Video on
Demand
• Animation
• Infotainment
• Advertisement
Mobility
and
individual
services
Mobile
IP
Why GPRS?

• GSM packet mode
• A new entity called GPRS Support Node (GSNs) is introduced to
create end to end packet transfer mode within PLMN. There are two
types of GSNs:
the Serving GPRS support node (SGSN)
the Gateway GPRS support node (GGSN)
• Designed to minimize hardware modifications on existing network
elements :
addition of a new hardware component in the BSS, the PCU, which
integrates most of the BSS new functions and manages RLC/MAC
layers
BSC and BTS are impacted as few as possible
entirely new core network with many functions
The HLR is enhanced with GPRS subscriber data and routing
information
GPRS: Architecture

• Provides an access to packet data networks
Internet
X.25
• This has driven to choices which are not « natural »
e.g. ciphering is between MS and SGSN (LLC layer), standard GSM
BTS are not capable to handle ciphering with several keys for
multiplexed MS on the same physical channel
• Two types of services are provided
Point to point (PTP)
Point to multi-point (PTM)
GPRS: Architecture

• Consists of packet wireless access network and IP-based backbone
• Shares mobility databases with circuit voice services and adds new
packet switching nodes (SGSN & GGSN)
• Will support GPRS, EDGE & WCDMA airlinks
• Provides services to different mobile classes ranging from 1-slot to
8-slot capable
• Radio resources shared dynamically between speech and data
services
GPRS: Architecture

VLR External
Data
Network
GGSNSGSN
Signalling
User data
Gb
Gn
Gr
Abis
Gs
Gateway
Mobility Management
Routing
Encapsulation
Mobility Management
Authentication Ciphering
Routing Other
PLMNs
Gp
Gi
New nodes
GSM nodes
MSC
GGSN
BSCBTS
HLR
Mobile data solution built upon the existing GSM Infrastructure and Mobility
Management. The packet oriented transport is obtained through a modified use
of GSM RF and the addition of packet switched nodes ( IP routers with addition
features like GPRS specific control and SS7 interfaces) in the backbone.
GPRS Architecture
Um

GPRS Architecture
Gf
D
Gi
Gn
Gb
Gc
CE
Gp
Gs
Signalling and Data Transfer Interface
Signalling Interface
MSC/VLR
TE MT BSS TEPDN
R Um
Gr
A
HLR
Other PLMN
SGSN
GGSN
Gd
SM-SC
SMS-GMSC
SMS-IWMSC
GGSN
EIR
SGSN
Gn

GPRS Architecture, The GGSN
• The Gateway GPRS support node (GGSN) acts as a
logical interface to the GPRS network and to external
public data networks such as IP and X.25
• GGSN is connected to with SGSNs via an IP GPRS
backbone network
• Routing. GGSN contains routing information for attached
GPRS users.
• Mobility Management. GGSN also performs mobility
management functions requesting location information
from the HLR.
• Encapsulation. GGSN performs routing functions to “tunnel”
Protocol Data Units (PDUs)

GPRS Architecture, The SGSN
• The SGSN is at the same hierarchical level as the MSC
and is responsible for the delivery of packets to the MSs
within its service area.
• Mobility Management. SGSN Keeps track of the individual
MS’s location.
• Authentication. SGSN does access control
• Ciphering. Performs security functions
• Routing. Provides packet routing to and from the SGSN
service area for all users in that service area.

GPRS Protocol Architecture
Relay
Network
Service
GTP
Application
IP / X.25
SNDCP
LLC
RLC
MAC
GSM RF
SNDCP
LLC
BSSGP
L1bis
RLC
MAC
GSM RF
BSSGP
L1bis
Relay
L2
L1
IP
L2
L1
IP
GTP
IP / X.25
Um Gb Gn Gi
MS BSS SGSN GGSN
Network
Service
UDP /
TCP
UDP /
TCP
Relay

• Above the network layer, widespread standardized
protocols may be used.
• Between two GSNs:
The GPRS Tunneling Protocol (GTP) tunnels packet data units (PDU)
through the backbone network by adding routing information;
TCP/UDP and IP are used as the GPRS backbone network layer
protocols. Ethernet, ISDN or asynchronous transfer mode (ATM)-based
protocols may be used below IP;
• Between the SGSN and the MS
The SNDCP maps network level protocol characteristics onto the
underlying logical link control and provides functionalities like
multiplexing of network layer messages onto a single virtual logical
connection, encryption, segmentation and compression;

• Between the MS and BSS
The DLL is divided into the LLC and the RLC/MAC sublayers.
The LLC provides a logical link between the MS and the SGSN. Protocol
functionality is based on LAP-D
The RLC/MAC provides services for information transfer over the
physical layer of the GPRS radio interface.
– The RLC is responsible for the transmission of data blocks and the backward
error correction
– The MAC is derived from a slotted ALOHA protocol.
The Physical layer is split up into a PLL and RFL.
– The PLL is responsible for FEC, rectangular interleaving, and procedures for
detecting physical link congestion
– The RFL conforms to the GSM 05 series of recommendations.

• In the Network
The LLC is split between the BSS and the SGSN. The BSS functionality
is called LLC relay.
Between the BSS and the SGSN, the BSS GPRS Protocol (BSSGP)
conveys routing and QoS related information, and operates above frame
relay.
• Between the MS, BSS and the SGSN,
The same protocols are used for data transmission up to the SNDCP
protocol. At the network layer, a specific mobility management protocol is
required within the MS and SGSN.

GPRS in the GSM Evolution
• GPRS is part of the GSM data services evolution
GSM
Data
HSCSD
GPRS
EDGE
EGPRS
WCDMA
1998 1999 2001
WCDMA
Phase I
Evolution
9.6 kbps
9.6 - 28.8 kbps
9 - 53.6 kbps
384 kbps
144 - 384 kbps
384 - 2048 kbps
2000
Time

BSC
SGSN
GGSN
GPRS Mobility: Session Setup
PSTN/ISDN
BTS
IP
I want to do packet
Radio link established
Set up a context
Tunnel created
IP Address exists!
HLR
MSC
GMSC

GMSC
MSC
BSC
GGSN
SGSN
GPRS Mobility: Packet Forwarding
PSTN/ISDN
BTS
IP
163.43.42.143
Inbound packet
Allocate a few bursts and send it!
This tunnel!
This radio link!
Where is the mobile?
?
Where is the mobile?
?
HLR

GMSC
MSC
BSC
GGSN
SGSN
GPRS Mobility: Cell Reselection
PSTN/ISDN
BTS
IP
Tunnel created
Radio link established
I’m here now
OK, new link and tunnel
Still same IP address!
HLR

• A GPRS MS can operate in one of three modes of operation. The mode of
operation depends on the services that the MS is attached to, i.e., only GPRS
or both GPRS and other GSM services, and upon the MS's capabilities to
operate GPRS and other GSM services simultaneously;
• An MS in class A mode‑ of operation operates GPRS and other GSM services
simultaneously;
• An MS in class B mode‑ of operation monitors control channels for GPRS and
other GSM services simultaneously, but can only operate one set of services
at one time;
• An MS in class C mode‑ of operation exclusively operates GPRS services;
GPRS, Types of Mobile Station

But in fact … by end 2003
• 1 billion fixed IP nodes;
• 1 billion mobile nodes;
• 1 billion circuit switched high bandwidth nodes;
and:
• Millions of Bluetooth machine-to-machine communications;
• Millions of xDSL nodes with n>10 users per node.

ISP
Intranet
Internet
Packet Data Network with various
radio technologies
GGSN
PSTN
SGSN-
GSM
W-ATM
SGSN-
W-ATM
URAN SGSN-
UMTS
PSTN
GW
IP -
backbone
Modular, main
parts are
independent of
radio access
SGSN-
D-AMPS
GGSN-
corporate
IS-136
BSS

Network Evolution time plan
(also as 3GPP,ETSI,etc evolve..finally)
GPRS
Best effort packet data
EDGE
No voice
EDGE UMTS
Real time spectrum efficient multimedia
1999 2000 2001 2002 2003
GPRS with IPv4
GSM voice
EDGE
Best effort v4 packet data
GSM voice
UMTS with IPv4+v6
Circuit switched voice
EDGE UMTS
Real time IPv6 voice and data
Phase1
Phase2

Common architecture 2003
3G Network based on the same Server/Gateway architecture
for wireline & for wireless
Backbone
MGW MGW
Wireless Wireline
Media Gateway

GMSC
MSC
UTRAN
BSC
GGSN
SGSN
UMTS network overview
PSTN/ISDN
UTRAN: UMTS Terrestrial Radio Access Network
RNC: Radio Network Controller
Node
B
CS core network
UTRAN transport: ATM
New tricks: Soft Handover using IP
IP
Packet core network
HLR

Multiple Levels of Mobility
• Access level
classical cellular
• Network level
Mobile IP
• Application level
H.323 mobility and WAP gateways

Mobility Concepts for Users
• The user does not care about it!
They just want to have access at anytime, to anything and anywhere;
• True mobility (always the best access)
Depends on subscription, coverage and terminal capacity;
• The way to get there
Hidden and seamless across different access technologies

UMTS Basic Configuration
BSS
BSC
RNS
RNC
CN
Node B Node B
A IuPS
Iur
Iubis
USIM
ME
MS
Cu
Uu
MSC
SGSN
Gs
GGSNGMSC
Gn
HLR
Gr
Gc
C
D
E
AuC
H
EIR
F Gf
GiPSTN
IuCSGb
VLR
B
Gp
VLR
G
BTSBTS
Um
RNC
Abis
SIM
SIM-ME i/f or
MSC
B
PSTNPSTN
cell
• The basic configuration is a PLMN
supporting GPRS and the
interconnection to the PSTN/ISDN and
PDN;
• Interface Iu, Iur and Iubis are defined in
the UMTS 24.4xx series;
• Interfaces B, C, D, E, F and G need the
support of the support of the Mobile
application Part of the signaling system
No 7 to exchange the data necessary to
provide the mobile service.

Working Assumptions
The phase 1 UMTS/Release ‘99 standards should provide the capability to support:
• a core network based on an evolved 2G MSC and an evolved SGSN;
• an optionally evolved Gs interface;
• mobile IPv4 with Foreign Agent care-of address to end users over the UMTS/GPRS
network, where the Foreign-Agent is located in the GGSN;
• UMTS/IMT2000 phase 1 (release 99) network architecture and standards shall the
operator to choose between Integrated and Separated core network for transmission
(including L2);
• the UMTS standard shall allow for both separated and combined MSC/VLR and SGSN
configurations;
• separate the L3 control signaling from the L2 transport (do not optimize L3 for one L2
technology);
• future evolution may lead to the migration of some services from CS-domain to the PS-
domain without changes to the associated higher-layer protocols of functions.

Iu Interface
Iu-PS
AAL5
ATM
UDP/IP
GTP
User plane
AAL5
ATM
UDP/IP
GTP
User plane
• UTRAN shall support two logically separate
signaling flows via Iu to combined or
separate network nodes of different types
(MSC and SGSN);
• the protocol architecture for the User Plane
of the Iu interface towards the IP domain
shall be based on the same principles as
for the (evolved) Gn interface;
• One or several AAL5/ATM Permanent VCs
may be used as the common L2 resources
between the UTRAN and the ‘IP domain’ of
the CN.
Protocol architecture for the Iu user
plane toward the IP domain

Charging Functionality
Charging functionality is located at the 3G-SGSN, on the other hand only RNC can
identify the actual packet volume successfully transferred to a UE. In order for 3G-
SGSN to provide the volume based charging for IP domain, the system shall
support the following procedure over Iu interface:
• RNC indicates the volume of all not transferred downlink data (discarded or forwarded to
2G-SGSN) to the 3G-SGSN so that the 3G-SGSN can correct its counter. Partially
transferred packets are handled as not transferred;
• RNC delivers to the 3G-SGSN the discarded of forwarded volume accumulated over an
implementation dependent time and not per discarded or forwarded packet;
• the 3G-SGSN can ask RNC to provide the volume of buffered downlink data to correct its
counter at any time the 3G-SGSN wants.

Iu Control Plane
RANAP
MTP-3b
CTP
(module SCCP/MTP3 users)
SAAL-NNI IP
SCCP
RANAP protocol stack option
• for transport of RANAP messages over Iu
an SCCP protocol shall be used for both
packet and circuit switched domains;
• in the circuit switched domain SCCP
messages shall be transported on a
broadband SS7 stack comprising MTP3b
on top of SAAL-NNI;
• in the packet switched domain the UMTS
standard shall allow operators to chose one
out of two standardized protocol suites for
transport of SCCP messages:
broadband SS7 stack comprising MTP3b
on top of SAAL-NNI;
IETF CTP protocol suite for MTP3b users
with adaptation to SCCP, fully compatible
with IP.

Iu User Plane
RLC
MAC
L1
GTP-U
BSSGP
ATM
L2
L1
UDP/IP
L2
L1
UDP/IP
Uu Iu Gn Gi
UE RNS 3G-SGSN 3G-GGSN
GTP-UGTP-U
UDP/IP
RLC
L1
AAL5
ATM
UDP/IP
GTP-U
MAC
AAL5
• the standard shall support that the user data flows transported over the Iu reference point
to/from the ‘IP domain’ shall be multiplexed on top of common L2 resources;
• if the Iu data transport bases on ATM PVCs then the Iu IP layer provides the Iu network
layer services;
• a tunneling protocol is used on top of the common L2, this tunneling protocol
corresponds to an evolution of the user plane part of the GTP protocol used in GPRS put
on top of UDP/IP;
• the user data plane in the UMTS network is made up of two tunnels:
a first IP/UDP/GTP tunnel between RNC and 3G SGSN on Iu;
a second IP/UDP/GTP tunnel between GGSN and 3G SGSN on Gn.

Data Retrieve Between GPRS and UMTS
GGSN
2G-
SGSN
SRNC
U
E
RLCLLC
3G-
SGSN
Data retrieve via 3G-
SGSN via two GTP
pipes
Data Retrieve
In the user plane
GPRS/UMTS
Handover
Signalling
RANAP
GTP-c
• since some parameters transported by GTP-c
are CN related only, it is necessary to
terminate GTP-c signaling exchanged with the
2G-SGSN in the 3G-SGSN and to use
RANAP signaling on Iu between 3G-SGSN
and SRNC;
• as charging of the retrieved data is to be
carried out at 3G-SGSN, data exchanged
between SRNC and 2G-SGSN are handled
by the 3G-SGSN to ensure that:
3G-SGSN can increment charging counters
for user data sent from 2G-SGSN to SRNC;
3G-SGSN can decrement charging counters
for user data sent from SRNC to 2G-SGSN
avoiding that such data are charged twice.

GTP-u
AAL5
IP
UDP
ATM
GTP-u
L2
IP
UDP
L1
SRNC 3G-SGSN 2G-SGSN
GTP-u
L2
IP
UDP
L1
GTP-u
AAL5
IP
UDP
ATM
Iu Gn
User Plane Protocol Stack for Data
Retrieve Between GPRS and UMTS

SRNC
GGSN
SRNC
UE
RLCRLC
3G-SGSN 3G-SGSN
data retrieve via 3G-SGSN
User data stream
RNSAP
Signalling
SRNS
Relocation
Signalling
GTP-c
RANAPRANAP
User Data Retrieve in UMTS
• there are two kind of signaling:
core network: corresponds to signaling
exchanged on Gn between 3G-SGSNs during
the first phase of resources for the SRNC
relocation;
access network: corresponds to signaling
for RLC protocol between SRNC and UE. This
can be done over Iur when the source SRNC
actually hands-over the role of SRNC;
• the user plane for data retrieve between two
RNCs is based on GTP-u/UDP/IP, the GTP
connections are terminated in the source
SRNC and the target SRNC.

User Plane Protocol Stack for Data
Retrieve in UMTS
GnIu Iu
GTP-u
AAL5
IP
UDP
ATM
L2
IP
L1
GTP-u
AAL5
IP
UDP
ATM
Source
SRNC
3G-SGSN 3G-SGSN Target
SRNC
L2
IP
L1
AAL5
IP
ATM
AAL5
IP
ATM

Two Iu signalling connections
(“two RANAP instances”)
UTRAN
3G SGSN
HLR
3G MSC/VLR
UE
CS service
domain
Two CN service domains
One RRC connection
UTRAN with
distribution
functionality
PS service
domain
Common subscription
data base
CS state PS state
PS stateCS state
CS location PS location
Separate Core Network Architecture
for UMTS

Integrated Core Network Architecture
for UMTS
Two Iu signalling connections
“two RANAP instances”
UTRAN
HLR
UMSC
UE
CS service
domain
Two CN service domains
One RRC connection
UTRAN with
distribution
functionality
PS service
domain
Common subscription
data base
CS state PS state
PS stateCS state
CS location PS location

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