UMTS System Architecture

and Protocol Architecture

Overview on overall system architecture
UMTS network architecture and elements
Mobile station
High-level functions
UMTS domains and strata
UMTS/GPRS protocol architecture
References:
Kaaranen, Ahtiainen, Laitinen, Naghian, Niemi: UMTS Networks Architecture, Mobility and
Services. 2nd edition, Wiley 2005
Ch 5.1: Core Network Architecture Release 3
Ch 5.4&5.5: Core Network Architecture Release 4 and 5
Ch 6: UMTS Terminal
3GPP TS 23.002: UMTS network architecture (CN and AN entities) and procedures
3GPP TS 23.101: General UMTS architecture
3GPP TS 23.060: GPRS, Service Description
3GPP TS 21.101/21.102/21.103: List of standards for Release 3, 4 and 5, respectively
3GPP TR 21.905: UMTS vocabulary and abbreviations
UMTS Networks

Andreas Mitschele-Thiel, Jens Mckenheim

Oct-12

UMTS/GSM Network Architecture

Base station

Base station

ISDN

Base station
controller

Base station

MSC

GSM Core
(Circuit
switched)

GSM
RAN

GMSC

HLR
AuC
EIR

node B
node B

node B

UMTS Networks

Radio network
controller

UTRAN

Andreas Mitschele-Thiel, Jens Mckenheim

SGSN

Internet
GPRS Core
(Packet
Switched)
Oct-12

GGSN

UMTS System Architecture

Mobile Station (MS):
radio interface
service control and user interface

Radio Access Network (RAN):

radio-specific functions

data
networks
ISDN
network

USIM

mobile
network

UMTS Subscriber Identity Module (USIM):

subscriber-specific data
support of authorized access to network
UMTS Networks

Andreas Mitschele-Thiel, Jens Mckenheim

Core Network (CN):

radio-independent functions
transport
mobility management
subscriber data
service control
Oct-12

Gi

Circuit switched CN

GGSN

AuC
C
PSTN

VLR

Gr

Gf
Gs

MSC

Gn

EIR
F

Gc

HLR

PSTN

VLR

SGSN

MSC
E

CN
Source: 3GPP 23.002-3.4.0

Basic Configuration, Release 3

GMSC

Gp

Packet switched CN

UMTS Network Architecture

PSTN

GSM
RAN

Gb

RNS

BSS

Iur

BSC

RNC

Abis

BTS

RNC

Iub

BTS

Node B
cell

Um
UMTS Networks

IuPS

IuCS

Andreas Mitschele-Thiel, Jens Mckenheim

Uu

Oct-12

Node B

UTRAN
4

Mobile-services Switching Centre (MSC)

Source: 3GPP 23.002-3.5.0

An exchange performing all the switching and signalling functions (CS

only) for mobile stations
MSC controls mobile-originated and mobile-terminated CS calls
Functions

call management
mobility management (handling attach and authentication)
subscriber administration
maintenance of charging data (for radio network usage)
CS data services (FAX, modem)
supplementary call services (call forwarding, etc.)
SS7-based signaling

Main difference to an exchange in a fixed network: deal with mobility (e.g.

location registration, handover)
Gateway MSC (GMSC)
Provides interconnection between the UMTS core network and external
PSTN/ISDN networks
UMTS Networks

Andreas Mitschele-Thiel, Jens Mckenheim

Oct-12

GPRS Support Node (GSN)

Source: 3GPP 23.002-3.5.0

GSNs constitute the interface between the radio access network and the
fixed networks for packet switched services (similar to MSC for CS calls)
Serving GSN (SGSN)

session management
mobility management
subscriber database management (interface with HLR)
maintenance of charging data (for radio network usage)
IP-based transport of user data between SGSN and the UTRAN
IP- or SS7-based signaling transport

Gateway GSN (GGSN)

gateway for UMTS packet service to external data networks (e.g. the
Internet)
IP interface towards SGSN
performs user data screening and security
maintenance of charging data (for external data network usage)
UMTS Networks

Andreas Mitschele-Thiel, Jens Mckenheim

Oct-12

Home Location Register (HLR)

Source: 3GPP 23.002-3.5.0

Home (primary) data base in charge of the management of

mobile subscribers
Basic information:
International Mobile Subscriber Identity (IMSI)
CS subscription information
one or more Mobile Subscriber International ISDN number(s)
(MSISDN)
PS subscription information
zero or more Packet Data Protocol (PDP) address(es)
permission for GGSN to dynamically allocate PDP addresses for a
subscriber
location information enabling the charging and routing of calls towards
the MSC or SGSN where the MS is registered (e.g. VLR Number)
Other information:
teleservices and bearer services subscription information
service restrictions (e.g. roaming limitation)
parameters attached to supplementary services
UMTS Networks

Andreas Mitschele-Thiel, Jens Mckenheim

Oct-12

Visitor Location Register (VLR)

Source: 3GPP 23.002-3.5.0

(Secondary) data base supporting the management of mobile

subscribers currently located within its VLR area
Motivation: minimize load for HLR (i.e. of the primary data base)
Tasks:
control MSs roaming in an MSC assigned to it
exchange information with HLR to allow the proper handling of calls
Information maintained by VLR (for call handling):

International Mobile Subscriber Identity (IMSI)

Mobile Station International ISDN number (MSISDN)
Mobile Station Roaming Number (MSRN)
Temporary Mobile Station Identity (TMSI), if applicable
location area where the mobile station has been registered
the last known location and the initial location of the MS
supplementary service parameters attached to the mobile subscriber
(received from the HLR)

UMTS Networks

Andreas Mitschele-Thiel, Jens Mckenheim

Oct-12

Authentication Centre (AuC)

Source: 3GPP 23.002-3.5.0

Stores data for each mobile subscriber

to authenticate the International Mobile Subscriber Identity (IMSI)
to support ciphering of the communication over the radio path
The AuC transmits the data needed for authentication and ciphering via
the HLR to the VLR, MSC and SGSN which need to authenticate a mobile
station
AuC is associated with an HLR, and stores an identity key for each mobile
subscriber
The AuC communicates solely with its associated HLR (H-interface)

UMTS Networks

Andreas Mitschele-Thiel, Jens Mckenheim

Oct-12

Equipment Identity Register (EIR)

Source: 3GPP 23.002-3.5.0

Logical entity storing the International Mobile Equipment Identities (IMEIs)

Equipment is classified as
white listed: serie number of equipment
grey listed: equipment tracked by network
black listed: barred equipment
unknown to EIR

UMTS Networks

Andreas Mitschele-Thiel, Jens Mckenheim

Oct-12

10

Other CN entities

Source: 3GPP 23.002-3.5.0

SMS Gateway MSC (SMS-GMSC)

gateway between Short Message Service Center and PLMN
deliver SMSs from service center to MS
SMS Interworking MSC (SMS-IWMSC)
gateway between PLMN and Short Message Service Center
deliver SMSs from MS to service center
Interworking Function (IWF)
associated with MSC
supports interworking of PLMN with fixed networks, e.g. ISDN, PSTN,
PDN (protocol conversion)
Border Gateway (BG)
PS gateway to other PLMNs
firewall functionality
Charging Gateway Functionality (CGF)
collects charging records from SGSNs and GGSNs
UMTS Networks

Andreas Mitschele-Thiel, Jens Mckenheim

Oct-12

11 o

Radio Network System (RNS)

Provide access to the UMTS terrestrial radio interface
Radio Network Controller (RNC)
(Radio) mobility management
Management of radio resources

Core Network

Iu

Iu
RNS

RNS

UTRAN

Iur
RNC
Iub
Node B

RNC
Iub

Iub

Node B

Node B

Iub
Node B

Base Station (Node B)

Radio coverage of cells
Physical layer processing
UMTS Networks

Andreas Mitschele-Thiel, Jens Mckenheim

Oct-12

12

Mobile Station (MS)

Mobile station (MS)/
User Equipment (UE)
physical equipment used by
a PLMN subscriber

Mobile Equipment (ME)

radio transmission
and application
Mobile Termination (MT)
functions for radio transmission
and management of the radio
interface, e.g. the handset

ITU-T Recommendyer

Terminal Equipment (TE)

support for end-to-end
application
functions necessary for
the operation of the
access protocols by the
user, e.g. a laptop

UE

Mobile Equipment (ME)

Terminal
Equipment
(TE)

Mobile
Termination
(MT)

Uu

T
A
F

Access
Network

Cu

UMTS Subscriber Identity

Module (USIM)
user identity
contains data and procedures
to unambiguously and securely
identify itself
UMTS Networks

USIM

Andreas Mitschele-Thiel, Jens Mckenheim

Terminal Adaptation Functions (TAF)

(service dependent)
mapping of terminal requests on
network capabilities
flow control/rate adaptations
Oct-12

13 o

UMTS High-level Functions (PS Domain)

Network Access Control
Provide means by which a user is
connected to a telecommunication
network
Registration
Association of Mobile ID with the
user's packet data protocol(s) and
address(es) within the PLMN, and
with the user's access point(s) to the
external PDP network
Authentication and Authorisation
Identification and authentication of
the service requester, and the
validation of the service request type
Admission Control
Check available network resources
required to provide the quality of
service (QoS)

UMTS Networks

Andreas Mitschele-Thiel, Jens Mckenheim

Message Screening
A screening function with filtering out
unauthorised or unsolicited messages
(firewall)
Charging Data Collection
Collection of data necessary to
support subscription and/or traffic
fees
Operator Determined Barring
Limitation of the service provider's
financial risk with respect to new
subscribers or to those who have not
promptly paid their bills by restricting
a particular packet-switched service

Oct-12

14

UMTS High-level Functions (PS Domain)

Packet Routing and Transfer
Determining and using the route
for transmission of a message
within and between the PLMN(s)
Forwarding
Forwarding of data received from
one node to the next node in the
route
Routing
Selection of the transmission path
for the "next hop" in the route
using the destination address of
the message
Address Translation and Mapping
Conversion of one address to
another address of the same or
different type, i.e. to convert an
external network protocol
address into an internal network
address

UMTS Networks

Encapsulation/Decapsulation
Addition/removal of address and control
information to a data unit for routing
packets within and between the PLMN(s)
and between the SGSN and the MS
Tunneling
Transfer of encapsulated data units
within and between the PLMN(s) from
the point of encapsulation to the point of
decapsulation
A tunnel is a two-way point-to-point path
Compression
Optimisation of radio path capacity
Ciphering
Preservation of the confidentiality of user
data and signalling across the radio
channels

Mobility Management
Keep track of location of MS
...

Andreas Mitschele-Thiel, Jens Mckenheim

Oct-12

15

UMTS Functional Entities: Domains

Domain: grouping of physical entities of the system

Air Interface

Radio Access
Network (RAN)

Home
Network
Domain
[Zu]

Cu

Uu

Iu

[Yu]

Serving Network
(SN) Domain

USIM
Domain

Mobile
Equipment
Domain

User Equipment (UE) Domain

Access Network
(AN) Domain

Transit
Network
Domain

Core Network
(CN) Domain

Infrastructure Domain
Source: 3GPP 23.101-4.0.0

UMTS Networks

Andreas Mitschele-Thiel, Jens Mckenheim

Oct-12

16

Functions of the UMTS Domains

Infrastructure domain
Access network (AN) domain: functions specific to access technique
Core network (CN) domain: functions independent of access technique
Access network domain
physical entities managing the resources of the access network
provides the user with a mechanism to access the core network domain
Serving network (SN) domain
part of the CN domain to which the AN domain that provides the users
access is currently connected
responsible for routing calls and transport user data/information from source
to destination
provides CN functions that are local to the users access point (i.e. SN
changes when the user moves)
Home network (HN) domain
provides CN functions that are conducted at a permanent location regardless
of the location of the users access point (i.e. does not change due to user
mobility)
contains user-specific data and is responsible for management of
subscription information
handle home-specific services, not offered by the serving network domain
User Services Identity Module domain (USIM)
related to the home network domain by subscription
UMTS Networks

Andreas Mitschele-Thiel, Jens Mckenheim

Oct-12

17

Functional Communication between

UMTS domains
Protocols and functions related to the
handling and storage of
subscription data and
possibly home network
specific services

Home Stratum
USIM - HN
USIM - MT

MT - SN

SN - HN

Protocols and functions to

Serving Stratum
USIM - MT

route and transmit

data/information (user

MT - SN

or network generated) from

source to destination

Transport of user data and

network control signalling

Transport Stratum
Access Stratum
MT - AN

USIM

MT/ME

AN - SN

Access
Network
Domain

Strata concept:
grouping of functions
grouping of
respective protocols
UMTS Networks

functions related to subscription

data management, customer care,
including billing and charging,
mobility management and
authentication
functions to allow domains other
than the home network domain to
act on behalf of the home network

Serving
Network
Domain

Home
Network
Domain

error correction and recovery

encrypt data over the radio interface
and in the infrastructure part
adaptation of data to use the supported
physical format
transcoding of data to make efficient
use of, e.g. the radio interface

Parts of infrastructure, user equipment and

protocols specific to the access technique
provides services related to the transmission

of data over the radio interface and

the management of the radio
interface

Andreas Mitschele-Thiel, Jens Mckenheim

Source: 3GPP 23.101-4.0.0

Oct-12

18 o

ow1

Functional Communication between

UMTS domains

End-to-end protocols and

Application Stratum

functions which make use of services

provided by the home, serving and
transport strata and infrastructure to
support services and/or value added
services.

Application

The functions and protocols within the

application stratum may adhere to
GSM/UMTS standards such as MExE or
may be outside the scope of the UMTS
standards.

Serving Stratum
TE - MT

MT - SN

Transport Stratum
Access Stratum
MT - AN

AN - SN

MT

TE
Mobile
Equipment
Domain

Access
Network
Domain

Serving
Network
Domain

Transit
Network
Domain

Remote
Party

Source: 3GPP 23.101-4.0.0

UMTS Networks

Andreas Mitschele-Thiel, Jens Mckenheim

Oct-12

19 o

Folie 19
ow1

Hier ist das Serving Stratum seltsam!

Oliver Waldhorst; 17.10.2011

UMTS Protocol Architecture

We will focus on the packet switched mode here

References:
Kaaranen, Ahtiainen, Laitinen, Naghian, Niemi: UMTS Networks Architecture, Mobility
and Services. Wiley 2001, Ch. 5.1
Walke, et al: UMTS ein Kurs, Ch. 5 (air interface only)
3G TS 23.060: GPRS, Service Description
UMTS Networks

Andreas Mitschele-Thiel, Jens Mckenheim

Oct-12

20

User Plane Bearer Services Overview

UMTS
TE

MT

UTRAN

CN
Gateway

CN Iu
EDGE
NODE

TE

End-to-End Service

TE/MT Local
Bearer Service

External Bearer
Service

UMTS Bearer Service

CN Bearer
Service

Radio Access Bearer Service

UMTS Networks

Radio Bearer
Service

Iu Bearer
Service

UTRA
FDD/TDD
Service

Physical
Bearer Service

Backbone
Bearer Service

Andreas Mitschele-Thiel, Jens Mckenheim

Oct-12

21

Bearer Services Analogy with Public

Transportation
UMTS
TE

MT

UTRAN
CNtaxi
Iu
Combo ticket:
bus and
EDGE
NODE

Taxi, bus and train combo:

singleCNticket, single
TE reservation,
Gateway
same
service everywhere

End-to-End Service

TE/MT Local
Bearer Service

External Bearer
Service

UMTS Bearer Service

CN Bearer
Service

Radio Access Bearer Service

Walk to taxi

Taxi:
Flat bus stop

Radio Bearer
Service

Iu Bearer
Service

UTRA
FDD/TDD
Service

Physical
Bearer Service

Taxi with driver

UMTS Networks

Train:
Station station

Backbone
Bearer Service

Bus:
Bus stop railway station

Bus with driver

Andreas Mitschele-Thiel, Jens Mckenheim

For each bearer:

specific attributes (delay,
bandwidth, guarantees, etc.
specific reservation
mechanism
22
Oct-12

MS-RNS-SGSN-GGSN User Plane

Application

E.g., IP,
PPP

E.g., IP,
PPP
Relay

Relay

PDCP

PDCP

GTP-U

GTP-U

GTP-U

GTP-U

RLC

RLC

UDP/IP

UDP/IP

UDP/IP

UDP/IP

MAC

MAC

AAL5

AAL5

L2

L2

L1

L1

ATM

ATM

L1

L1

Uu

MS

Iu-PS

UTRAN

Gn

Gi

3G-GGSN

3G-SGSN

Source: 3GPP 23.060-4.1.0

UMTS Networks

Andreas Mitschele-Thiel, Jens Mckenheim

Oct-12

23

MS-RNS-SGSN-GGSN User Plane

Application

E.g., IP,
PPP

E.g., IP,
PPP
Relay

Relay

PDCP

PDCP

GTP-U

GTP-U

GTP-U

GTP-U

RLC

RLC

UDP/IP

UDP/IP

UDP/IP

UDP/IP

MAC

MAC

AAL5

AAL5

L2

L2

L1

L1

ATM

ATM

L1

L1

Uu

Iu-PS

GTP-U
(GPRS Tunneling
plane):
MS
UTRAN Protocol for User
3G-SGSN
tunneling of user data between UTRAN and the 3G-SGSN
tunneling between the GSNs in the backbone network
Source: 3GPP 23.060-4.1.0
encapsulation of all PDP PDUs
UMTS Networks

Andreas Mitschele-Thiel, Jens Mckenheim

Oct-12

Gn

Gi

3G-GGSN

24

MS-RNS-SGSN-GGSN User Plane

Application

E.g., IP,
PPP
Relay
PDCP

PDCP

GTP-U

RLC

RLC

UDP/IP

MAC

MAC

AAL5

L1

L1

ATM

Uu

MS

UTRAN

PDCP (Packet Data Convergence

Protocol):
E.g., IP,
PPP(wrt
provides protocol transparency
the underlying radio-interface
Relay
protocols)
for higher-layer protocols
support
forGTP-U
e.g., IPv4, PPP and
IPv6
GTP-U
GTP-U
(easy introduction of new higherlayer protocols)
UDP/IP UDP/IP
UDP/IP
compression of control information
L2
AAL5 compression)
L2
(header
no ATM
user data L1
compression in Iu
L1 mode
Iu-PS (because the data compression
Gn
Gi
3G-GGSN
3G-SGSN
efficiency
depends on the type
of
user data)

Source: 3GPP 23.060-4.1.0

UMTS Networks

Andreas Mitschele-Thiel, Jens Mckenheim

Oct-12

25

MS-RNS-SGSN-GGSN User Plane

Application

E.g., IP,
PPP

E.g., IP,
PPP
RelayControl):
RLC (Radio Link
RLC GTP-U
protocol GTP-U
provides logical GTP-U
link
GTP-U
control over the radio interface
There may be several simultaneous
UDP/IP
UDP/IP UDP/IP
UDP/IP
RLC links per MS; each link is identified
L2
AAL5
by a AAL5
Bearer Id L2

Relay
PDCP

PDCP

RLC

RLC

MAC

MAC

L1

L1

ATM

Uu

MS

Source: 3GPP 23.060-4.1.0

UMTS Networks

UTRAN

ATM

L1

L1

Iu-PS
Gn
MAC
(Medium Access Control):
3G-GGSN
3G-SGSN
MAC protocol controls the access
signaling (request and grant)
procedures for the radio channel

Andreas Mitschele-Thiel, Jens Mckenheim

Oct-12

Gi

26

MS-RNS-SGSN-GGSN Control Plane

GMM /
SM / SMS

GMM /
SM / SMS

Relay
RRC

RRC

RANAP

RANAP

GTP-C

GTP-C

RLC

RLC

SCCP

SCCP

UDP

UDP

MAC

MAC

Signalling
Bearer

Signalling
Bearer

IP

IP

AAL5

AAL5

L2

L2

ATM

ATM

L1

L1

L1

L1
Uu

MS

UMTS Networks

Gn or Gp

Iu-Ps

RNS

3G SGSN

Andreas Mitschele-Thiel, Jens Mckenheim

GSN

Oct-12

GSN

27 o

MS-RNS-SGSN Control Plane

GMM (GPRS Mobility Management):
GMM supports mobility management functionality such as attach, detach,
security, and routing area update
SM (Session Management):
SM supports PDP context activation and deactivation
SMS supports short message service
GTP-C (GPRS Tunneling Protocol for Control plane):
establish, manage and release GTP tunnels
RANAP (Radio Access Network Application Protocol):
transport of higher-layer signalling
handling of signalling between the 3G-SGSN and UTRAN
management of the GTP connections on the Iu interface
RRC (Radio Resource Control):
Information Broadcast (AS and NAS)
RRC connection management (setup, release, reconfiguration)
Radio Bearers management (setup, release, reconfiguration)
Management of radio resources for the RRC connection
RRC connection mobility functions
Paging/notification
Source: 3GPP 23.060-4.1.0
UMTS Networks

Andreas Mitschele-Thiel, Jens Mckenheim

Oct-12

28

UMTS Protocol Architecture:

The Complete Picture (Packet Switched)
Uu

Node B

Iub

Iups

RNC

SM
SM

SM
MM

IP

PMM
MM

PMM
SM

PDCP

RRC
RRC

RRC
RRC

RLC
codec
RLC

RLC
RLC

MAC
MAC
ALCAP

ALCAP

STC.2
NBAP
ALCAP
NBAP
FP
FP
PHY
PHY

AAL2
AAL2

UDP

Phy-up
Phy-up

STC.2
ALCAP

SSCF-UNI
SSCF
SSCF

SSCOP
SSCOP SSCOP

SSCOP
SSCOP SSCOP

AAL5
AAL5
AAL5

AAL5
AAL5
AAL5

IP
GTP-U

RANAP
FP

RANAP

SCCP
SCCP

GTP-C

Q2150.1
UDP

Q2150.1
GTP-U

GTP-C

UDP

FP

AAL2
AAL2
AAL2

User Plane

MTP3-b
MTP3B

SSCF-N
SSCF

SSCF-N
SSCF

SSCF

SSCOP

SSCOP
SSCOP

SSCOP

AAL5
AAL5
AAL5

Andreas Mitschele-Thiel, Jens Mckenheim

MTP3BIP

AAL5
AAL5
AAL5

Q2150.1
Iu UP
MTP3BIP
SSCFQ2150.1
SSCOP
L2
AAL2

AAL5

L2

ATM
ATM

STM-1
E1

Transport Plane

Q2150.1

MTP3-b
IP
FP

SCCP
SCCP

ATM
ATM

E1/ STM-1
E1

UMTS Networks

NBAP
NBAP

SSCF-UNI
SSCF
SSCF

ATM
ATM

Control Plane

GTP-U

GGSN

MAC
MAC

Phy-up
Phy-up

PHY
PHY

PDCP

Gn

SGSN

STM-1

L1

L1

E1

Common

Oct-12

29 o

UMTS Protocol Architecture:

The Complete Picture (Circuit Switched)
Uu

codec

Iub

Node B

CM
SM
MM
MM
RRC
RRC

MM
SM

RANAP

RLC
RLC
MAC
MAC
ALCAP
AA

FP

ALCAP
NBAP

SSCF-UNI
SSCOP

PHY
AAL2

AAL5

Phy-up
Phy-up

SSCF-UNI
SSCF
SSCF
SSCOP
SSCOP SSCOP
AAL5
AAL5
AAL5

SCCP

Iu UP

MTP3-b
FP
FP

SSCF-NNI

SSCOP
AAL2
AAL2
AAL2

AAL5

ATM
ATM
STM-1
E1

E1

User Plane

STC.1

Transport Plane

Andreas Mitschele-Thiel, Jens Mckenheim

RANAP
ALCAP

ALCAP

NBAP
STC.2
NBAP ALCAP

ATM

UMTS Networks

codec

RRC
RRC

STC.2

Control Plane

3G-MSC

CM
MM

RLC
codec
RLC
MAC
MAC
Phy-up
Phy-up

PHY
PHY

Iucs

RNC

Iu UP
SCCP STC.1
SCCP Q2150.1 Iu UP
MTP3B
MTP3B
MTP
SSCF-NNI
SSCF
SSCF
SSCOP
SSCOP
AAL5
AAL2
AAL5
AAL5
AAL2
ATM
ATM
STM-1
E1

Common

Oct-12

30 o