04 - UMTS Traffic Management

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SYSTEM TRAINING

3G/UMTS Traffic Management

Training Document

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UMTS Traffic Management

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ontent!

ontent!

" Mo#u$e o%&ecti'e!

2 Intro#uction to UMTS traffic management*

3 Su%!cri%er information an# #ata%a!e!+

Net,or- traffic an# ra#io connection"2

* Mo%i$it. management2

6 Se!!ion management3

+ ommunication management**

Re'ie, 0ue!tion!*1

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" Mo#u$e o%&ecti'e!

The aim of this module is to give the student the conceptual knowledge needed

for explaining how traffic management is visualised in a UMTS network.Topics to be covered in this module include understanding the network

databases and the information stored within them. At an overview level, we will

look at the different management layers in the network.

After completing the module, the participant should be able to

• !ist and identify the databases used within the UMTS network

• "dentify the subscriber addressing information

• #ame the characteristics of a bearer

• $escribe how the connection moves with the subscriber when a bearer is

in use

• %xplain what is meant by the term U&A

• !ist the procedures used to maintain mobility management in the network

• !ist the procedures done when the mobile gains access to the network.

Also, identify how the network selection is made

• 'ith the help of the material, describe how the session management of

real time and non(real time bearers are handled through the network

without using any references )if not otherwise stated*.

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Se!!ion management

2 Intro#uction to UMTS trafficmanagement

'hen visualising a UMTS network, there are three ways to approach this. The

first view is from the point of view of the architecture and the functions of the

elements within the &AS and the core network subsystem. The second approach

is through the different interfaces between the mobile, &AS, and the core

network. The third approach is to look at how the data and signalling are carried

through the network )management layers*.

6i!er 6i!er

B8

ATM Acce!!

Internet

RAN (UTRAN GERAN) ore Net,or-

ontro$ $ane

Gate,a. $ane

STN2G

SGSN3G

SGSN GGSNRN

4S

No#e 4

No#e 4

No#e 4

5R

Au

3GMS

SE

SMS

4TS

i"ure 1. 3;C9:T net#ork arhiteture

The above figure illustrates the UMTS &elease ++ architecture, which is divided

into two planes. The control plane is responsible for the control of the

information through the network, whereas the gateway plane manages the user

data or bearer through the network.

'hen thinking of managing the subscriber within a network, there are many

procedures used for locating and paging, as well as for control activities such as

moving and charging. 'e can think of all these activities as management

functions that the network is performing. The functions and procedures are

clearly defined in the specifications.

The functions can be divided into management layers. %ach management layer

is responsible for certain procedures. The following figure illustrates the four

management layers in the network. The higher layers reuire the functions and

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procedures that are used on the lower layers. -or example, you must have a

connection to the mobile before you can send or receive signalling messages.

"n UMTS networks, we can identify four network(wide layers of functionality.

Mobility Management (MM)

Session Management (SM)

Communication Management (CM)

Radio Resource Management (RRM)

UE RAN CN

i"ure @. 3;-net#ork mana"ement $ayers

The radio resource management )&&M* is completely covered between the

radio access network )&A#* and the user euipment )U%*, and it involves

managing how the channels are allocated. The mobility management, session

management and call control are maintained by the core network )#* domains.

There the function depends on whether the domain is S )circuit switched* or

/S )packet switched*. The higher(layer functions performed between the U%

and # are often called as communication management )M*. The M entitycovers the topics like call control )*, supplementary services )SS* and short

message service )SMS*.

The radio resource management is the lowest level and it is responsible for the

network communication with the mobile over the air interface. 'e will discuss

&&M only briefly in this module.

"n this module we will first look at how the subscriber0s information is stored.

Also the structure of the cellular network and the functions of the management

layers will be explained.

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Se!!ion management

3 Su%!cri%er information an# #ata%a!e!

"nformation about the subscriber is stored in several parts of the network. This

information is used to identify the location of the subscriber when transmittingthe paging signal. The network uses uniue information to identify a subscriber,

and there are different types of databases throughout the network. Most of the

procedures are similar compared with 1SM and 1/&S. 2ence, this chapter is

mainly of a repetitive nature.

3" Net,or- #ata%a!e!

The databases are used all the time to control activities such as paging, channel

set(up and authentication. 3ther information about the subscriber may include,

for example, rights to services, security data, and identification numbers. The

figure below summarises the databases that are found within the network.

i"ure 3. Net#ork re"isters

Since the core network will not change dramatically in the first release of

UMTS, the registers are similar to those in 1SM and 1/&S.

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-iber -iber

A4.

ATM access

Internet

Mobility CoreRAN

Control Plane

Gateway Plane

PSTN2G

SGSN

3G

SGSN GGSNRNC

SC

!"R

AuC

#IR

3G

MSC

SMSC

Used as anintermediate store

for SMS

Contains subscriber IDs, serviceinformation and location

attributes. In AuC subscribersecurity information and insome implementations EIR

Used to supportsubscriber services

Contains temporaryinformation on

subscriber

Contains temporaryinformation on the

subscriber

SC#P

Mo#e4TS

Tri7$eMo#e 4TS

Mo#e4TS

8DMA4TS

Mo#e4TS

GSM 4TS




The $isitor "ocation Register )5!&* is considered to be an integral part of the

Serving MS. The 5!& maintains mobility management related procedures

like location update, location registration, paging, and security activities. The

5!& database contains temporary copies of the active subscribers, who have

performed a location update in its area.

The !ome "ocation Register )2!&* contains permanent data of the

subscribers. 3ne subscriber can always be in only one 2!&. The 2!& is

responsible for mobility management related procedures in both the circuit

switched and packet switched domains.

The Authentication Centre )A6Au* is a database handling the

Authentication 5ectors. These contain the parameters that the 5!& uses for

security activities performed over the "u interface. The #%ui&ment I'entity

Register )%"&* maintains the security information related to the user euipment

)U%* hardware.

The Short Message Ser(ice Centre )SMS* is an intermediate store for thereceived6sent short messages. Thus, it has signalling connections with the 5!&,

1/&S Support #odes, and 1ateway6"nterworking MS.

The "# Ser(ice Control Point )S/* nowadays has "#A/ )"ntelligent #etwork

Application /art* and6or A/ )amel Application /art* connections towards the

core network circuit switched )#(S* domain elements. The #(S domain

elements having the "# connection is called Service Switching /oints )SS/s*.

"n the packet switched domain, the 2!& is still a centralised source of

information. 2owever, two service nodes are used to supply the reuired "/

access information the)omain Name Ser(er

)$#S* and*irewalls

. The $#S

is used for "/ address translation. As an example, when the subscriber enters an

"nternet address )for example, http66www.nokia.com*, the Serving 1/&S

Support #ode )S1S#* needs to find out which 1ateway 1/&S Support #ode

)11S#* that supports access to this address )access point*. The role of the $#S

is therefore to give the S1S# the "/ address to the 11S#. After this, the 11S#

is able to route the user0s reuest further. The 71 core network packet switched

)71 #(/S* domain with its "/ backbone network actually forms an intranet

having its own facilities available for the mobile subscribers. The border

between the corporate networks, public "/, and 71 #(/S domain is

maintained by the -irewall Server controlling the inter(network connections and

their access.

3ther nodes )such as voice mail systems and application servers* can alsocontain subscriber and network information.

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http://www.something.com/

http://www.something.com/




The MS"S$# consists of three parts

MSISDN = CC + NDC + SN

'here

• 9 ountry ode ): to 7 digits*

• #$ 9 #ational $estination ode ): to 7 digits*

• S# 9 Subscriber #umber.

This number format follows the %.:<= numbering specification. 5ery often this

number is called >directory number? or @ust simply >subscriber number?.

$ue to security reasons it is very important that the uniue identity

)"MS"6"MU"* is transferred in non(ciphered mode as less as possible. -or this

purpose, the UMTS system uses TMSI )Temporary Mobile Subscriber "dentity*

number, which is also called TM+I )Temporary Mobile User "dentity*. The

packet switched domain of the core network allocates similar temporaryidentities for the same purpose. "n order to separate this type from the

TMS"6TMU", it is named P,TMSI )/acket Temporary Mobile Subscriber

"dentity*.

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B8

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ontro$ $ane

Gate,a. $ane

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3G

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4S

No#e 4

No#e 4

No#e 4

56R

Au

3G

MS

SE

SMS

4TS

!"MSI is allocatedfor pac#et

transactions by theS$S%.

"he "MSI&"MUI is'enerated by the ()R

and used for CStransactions

i"ure 5. Tem%orary information stored in the net#ork

TMS"6TMU" and /(TMS" are random(format numbers, which have limited

validity time and validity area. The TMS"6TMU" numbers are allocated by the

5!& and they are valid until the U% performs the next location update

procedure. The TMS"6TMU" may also change earlier, and the network controls

this pace of change. The /(TMS" is allocated by the S1S# and it is valid over

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Se!!ion management

the S1S# area. The /(TMS" is changed when the U% performs routing area

update.

IM#I )"nternational Mobile %uipment "dentity* is a number uniuely

identifying the user euipment0s hardware. There is a separate register called%"& )%uipment "dentity &egister* handling these identities. The network may

or may not ask the U% to identify itself with "M%" number either in context of

every transaction or occasionally in the cases defined by the network operator.

6i!er 6i!er

B8

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Internet


ontro$ $ane

Gate,a. $ane

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4S

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56R

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EIR

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MS

SE

SMS

4TS

RAN"he IMEI is used to trac#le'al mobile e*uipment

+optional

i"ure 6. /nsurin" termina$ e*ui%ment seurity

All the "M%" numbers are handled in three categories within the core network.

These categories are called lists, that is, 'hite !ist, 1rey !ist and lack !ist.

'hite listed "M%" numbers are normal identities, which do not have any

troubles. The grey listed "M%" numbers are under observation, and every time a

U% having grey listed "M%" used, the network produces an observation report

about the transaction. "f the accessing U% is on the black list, the network

re@ects the transaction, except in case of an emergency call.

There are several other addresses that are used. 3ne is the MSRN )Mobile

Subscriber &oaming #umber*, which is used for call routing purposes. Theformat of the MS&# is the same than MS"S$#, that is, it consists of three parts

), #$, and S#* and it follows %.:<= numbering specification. The MS&#

is used during a call set(up between the network and a subscriber on another

MS. The implementation of this explanation is beyond the scope of this

module.

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Net,or- traffic an# ra#io connection

"n the previous chapter we looked at the type and location of information that is

stored about a subscriber within the network. "n this chapter, the focus is onhow the user traffic )also known as the user plane* is visualised in the network

and how the connection is managed in the air interface.

The first concept to clarify is the bearer. The figure below illustrates that a

bearer is like a tunnel that goes through the different network elements and is

carried on the different network interfaces.

UE Node B RNC

Uu Iub/Iur Iu

Core Networ

i"ure 7. Thinkin" in terms of a net#ork !earer

The application )such as video* in the mobile has a point(to(point connection to

a remote application )such as video on another terminal*. -rom the physical

network0s point of view, the UMTS radio access network )UT&A#* must

ensure that the bearer is maintained over the air interface and is correctly routed

to the core network.

The core network ensures that the bearer is either connected into the service

platform, "nternet, external network or, in the case of a voice6video call, onto

the /ST# )see the figure below*. "n the case of the /ST#, the information in the

bearer pipe must be converted to a form that is understood by the outside world.

UE Node B RNC

Uu Iub/Iur Iu

Core Network

Data/Wireless Protocols are transparent to surrounding network

MG8

The !W "or #!$%C per"or&s speech transcoding

i"ure 8. ata and s%eeh throu"h the !earer

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Se!!ion management

" 9aracteri!tic of a net,or- %earer

"f you think in terms of 1SM, you probably consider the traffic channel to be

the same as a bearer in the air interface. A traffic channel does share some samecharacteristicsB for example, it can carry different types information )such as

speech and circuit switched data*. The fundamental difference between 1SM

and UMTS is that in UMTS, the bearer is fle-ible. The type of the bearer

reserved and the way it is routed through the network depends on the

subscriber0s service need. To better understand this concept, let us take two

examples.

E:am7$e "; <oice traffic

5oice reuires a data speed of, for instance, :8.8 kb6s. )The bit rate depends of

course on which speech coding method we use.* "f we add error correction

information )to ensure uality*, the total amount of data needed in the airinterface is approximately 8= kb6s. -or the interfaces within the radio access

network )"ub, "ur* and towards the circuit switched core network )"u*, the bit

rate reuired is around :<(:+ kb6s, including overhead. Therefore, we need a

connection from the mobile to the Media 1ateway that can support these bit

rates. Also, we have to take the 'elay factor into account. As subscribers we

are not tolerant of delays in our speech or video conversations.

• 8on(ersationa$ $ass

• 5oie and (ideo

• treamin" $ass

• treamin" (ideo

• Interati(e $ass

• ,e! !ro#sin"

• ak"round $ass

• :ai$ do#n$oadin"

i"ure D. The different air interfae $assifiations

E:am7$e 2; Internet connection

The first characteristic to remember is that "nternet traffic is often bursty and

asymmetric )there is usually more to download than to upload*. Also, the delay

factor is not as significant as for conversation, which means that we can tolerate

more variable bit rates. 3n the other hand, the data may be very sensitive to

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errors, compared with, for instance, voice transmission. "t means that we may

need to apply more ambitious error correction.

As a conclusion from these two cases, the network will allocate the bearer based

upon the reuest of the subscriber0s need. To be more precise, it is the radionetwork controller )&#* that makes the decision about the bearer allocation.

T.7e! an# configuration of %earer!

As with all mobile systems, the largest bottlenecks in allocating resources to a

mobile subscriber is in the air interface. This is the reason why the &# is

responsible for the bearer allocation. The air interface is limited in terms of the

maximum amount of subscribers, the maximum data rates, the coverage area,

and uality. "n UMTS, all of these factors are linked together. "f you introduce

more people to a cell, then the siCe and bit rate reduces.

The UMTS specification defines four classifications of bearers. These were

summarised in the previous figure. The below figure illustrates typical services

and their reuired data rates. 3f course the transmission and core networks must

be capable to support the different needsB one of the important tasks for the

network planners is to dimension the accurate capacity in the network beyond

the air interface.

$oice$oice Messages

MessagingTransactionalInfoser(ices

... browsingIntranet access)ownloa'ing

Au'io Streaming

; D :< 78 =D <= D; +< ::8 :8D :== :<; /bit0s

$i'eo Streaming$i'eotele&hony

UE Node B RNC

Uu Iub/Iur Iu

Core Network

i"ure 10. Ty%ia$ data s%eeds needed for ommon 3; ser(ies

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Se!!ion management

!et us assume that a video call is to be made through the network. A dedicated

traffic channel for the air interface must then be reuested. The U% must also

inform the network about the needed classification and data speed. "t is then the

&#0s responsibility to allocate an air interface channel and to establish the

connections through to the core network.

2 4earer tran!mi!!ion in t9e net,or-

3n its @ourney throughout the network, the bearer 0sits0 in a physical channel. 3n

the connection between the TS and the &# and towards the MS6S1S#, a

frame-structure protocol )typically ATM* is used.

3G

SGSN

GGSN

RNC

!"R

AuC

#IR 3G

MSC

Channels from the air interface alongthe Iub interface

Physical channels in theair interface are se&arate' by co'es

ATM lin/ to the MG. at the MSC

Pac/ets tunnelle' to theSGSN

Pac/ets tunnelle' from theSGSN to the GGSN

Pac/et )ata

)e'icate' circuit

PSTN

Internet

i"ure 11. Transmission throu"h the net#ork

The air interface also has physical channels, which are used to carry signalling

messages and data between the terminal and the network.

The above figure shows that between elements we have pipes. The networkelements ensure that the right information is moved from one pipe to another. "n

the circuit switched core network )S(#* domain, there is always a dedicated

circuit for the connection and it is only released at the end of the call.

"n the packet switched core network )/S(#*, we use tunnelling to make a

virtual connection between "/ network elements. Although tunnelling ensures a

semi(dedicated channel in an "/ network, it is still not the same as having a

dedicated circuit in the network. asically, the tunnel enables a virtual circuit

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between the &# via the Serving 1/&S Support #ode )S1S#*, and towards

the 1ateway 1/&S Support #ode )11S#*.

Stu#ent E:erci!e;,hy do you think the N makes the deision on the ty%e of !earer that isa$$oated to a su!sri!erE

4earer! an# t9e #ifferent $e'e$! of =oS

#etwork services are considered end(to(end, this means from terminal

euipment )T%* to another T%. An end(to(end service may have a certain EoS,which is provided for the user of a network service. "t is the user that decides

whether he6she is satisfied with the provided EoS or not.

To realise a certain network EoS, a bearer service with clearly defined

characteristics and functionality is to be set up from the source to the destination

of a service.

A bearer service includes all aspects to enable the provision of a contracted

EoS. These aspects are among others the control signalling, user plane

transport, and EoS management functionality. UMTS bearer service layered

architecture is depicted in the below figure )taken from the specifications*. %ach

bearer service on a specific layer offers its individual services and uses services

provided by the layers below.

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Se!!ion management

T/ :T 9T0N 8N Iu/7;/NO7/

8N;ate#ay

T/

/nd-to-/nd er(ie

T/C:T oa$earer er(ie

9:T earer er(ie /+terna$ earer er(ie

9:T earer er(ie

0adio ess

earer er(ie

8N earer er(ie

ak!oneearer er(ie

Iu earer er(ie

0adio earer er(ie

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earer er(ie

'

(

#)

i"ure 1@. ayered arhiteture of the !earer ser(ies in 9:T

3" T9e en#>to>en# !er'ice an# UMTS %earer !er'ice

:3n its way from the terminal euipment )T%* to another, the traffic has to pass

different bearer services of the network)s*. A T% is connected to the UMTS

network by use of a mobile terminal )MT*. The end(to(end service on the

application level uses the bearer services of the underlying network)s*. As the

end(to(end service is conveyed over several networks )not only UMTS*, it is not

sub@ect for further elaboration in the present document.

The end(to(end(service used by the T% will be realised using a T%6MT local

bearer service, a UMTS bearer service, and an external bearer service.

T%6MT local bearer service is not further elaborated here as this bearer service is

outside the scope of the UMTS network.

"t is the various services offered by the UMTS bearer service that the UMTS

operator offers. "n other words, it provides the UMTS EoS.

The external bearer service is not further elaborated here as this bearer may be

using several network services, such as another UMTS bearer service.

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T9e ra#io acce!! %earer !er'ice an# t9e core net,or- %earer !er'ice

8The UMTS bearer service consists of two parts the radio access bearer service

and the core network bearer service. oth services reflects the optimised way to

realise the UMTS bearer service over the respective cellular network topologytaking into account such aspects as, for example, mobility and mobile subscriber

profiles.

The radio access bearer service provides confidential transport of signalling and

user data between MT and # "u %dge #ode with the EoS adeuate to the

negotiated UMTS bearer service or with the default EoS for signalling. This

service is based on the characteristics of the radio interface and is maintained for

a moving MT.

T9e ra#io %earer !er'ice an# t9e Iu>%earer !er'ice

3The radio access bearer service is realised by a radio bearer service and an

"u(bearer service.

The role of the radio bearer service is to cover all the aspects of the radio

interface transport. This bearer service uses the UT&A -$$6T$$. UMTS

Terrestrial &adio Access6-reuency $ivision $uplex will be forming the

physical layer in the first phase of UMTS. !ater also Time $ivision $uplex is

expected to be implemented.

To support uneual error protection, UT&A# and MT shall have the ability to

segment and reassemble the user flows into the different subflows reuested by

the radio access bearer service. The segmentation6reassemble is given by theS$U payload format signalled at radio access bearer establishment. The radio

bearer service handles the part of the user flow belonging to one subflow,

according to the reliability reuirements for that subflow.

The "u(bearer service together with the physical bearer service provides the

transport between UT&A# and #. "u(bearer services for packet traffic shall

provide different bearer services for variety of EoS.

T9e %ac-%one net,or- %earer !er'ice

= The core network bearer service uses a generic backbone network service. The backbone network service covers the !ayer :6!ayer 8 functionality and is

selected according to operator0s choice in order to fulfil the EoS reuirements of

the core network bearer service. The backbone network service is not specific to

UMTS but may reuse an existing standard.

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Se!!ion management

Managing t9e %earer t9roug9 t9e net,or-

The UMTS network is responsible to establish a flexible bearer for user data

transport between the Mobile Terminal )MT* and the external networks. "n the bearer set(up phase, the EoS parameters must be known, so that the individual

network elements within the UMTS network FknowG, how to set(up the bearer.

TEe*ternalnetwork #!$ +!,%C/!!%NT UTR-N #!$ %C/%!%N

UT% B%anager

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ocalB%

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Trans$lation

i"ure 13. <o mana"ement in the ontro$ %$ane

As can be seen, a hierarchical approach is used for bearer establishment "n

order to establish a bearer in accordance to the EoS reuirements of the user?s

circuit switched application, a peer(to(peer bearer service )S* signalling

between the MT, MS, and )1*MS takes place. "n case of a packet orientated

service reuest, bearer related signalling and control information must be

exchanged between the MT, S1S#, and 11S#. )"n the next lines, we refer to

MT, S1S#, and 11S#. /lease note, that there is no significant difference for

the circuit switched case.* The peer(to(peer signalling is necessary, so that the

affected network elements can determine the reuired EoS parameters for theend(to(end bearer. "f one network element is not capable to establish the bearer,

a re(negotiation can be initiated to find an alternative bearer H if the user?s

application permits it H or the UMTS /!M# is not capable to offer the

reuested service.

"f the UMTS bearer service )S* manager use the 1/&S Tunnelling /rotocol

)1T/* for EoS negotiation between each other. "f they have agreed on the EoS

parameters for the bearer, the UMTS S manager of the # inform the # S

manager about the EoS parameters for the bearer between S1S# and 11S#. "t

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lies then in the responsibility of the # S manager to negotiate on how to

make the bearer available, which route to take between the S1S# and 11S#. "f

they have agreed on the EoS parameter on their level, they inform then the

ackbone network service ) #S* manager about the set EoS parameter.

'ithin the backbone, "/ over ATM may be applied, "/ over -rame &elay, etc.$epending on the underlying transmission technology and signalling protocols

used, the network elements must conduct signalling to step by step establish the

bearer between S1S# and 11S#.

A bearer also must be established between the MT and the S1S#. The &# is

responsible for the resource management within UT&A#. The &# is

managing so(called &adio Access earer )&A*. A &A stand for one bearer6

connection between a MT and a core network edge element )S1S#, MS*.

The &# must establish the bearer on Uu, "ub, "u, and H if reuired H on "ur.

After determining the EoS parameter internally used from the EoS parameters

set by the bearer service manager in the S1S#, it informs its "u bearer service

manager to negotiate and establish the bearer between itself and the S1S#. The&A manager also informs the &adio S manager about the reuired EoS

parameterB the &adio S manager then determines the radio EoS parameters.

The physical parameters for the transmission via the radio interface are then

determined in the underlying UT&A physical S manager, parameters such as

spreading codes, spreading factor, type of convolutionary coding.

The whole process is conducted to establish on every physical link within the

UMTS operator?s network a bearer in accordance to the EoS reuired for the

subscriber?s application.

earers for signalling can be negotiated, too. ut often, they are made available

during operation and maintenance.

Managing t9e %earer o'er UTRAN

"n UMTS there may be a number of connections between the core network and

the mobile. As an example, a subscriber may have a video, voice, and "nternet

connection bearer open. This means that the subscriber will be using multiple

bearers to support each service. %ach of this connection is known as a RA,

)radio access bearer*.

The &As for an individual subscriber are grouped together into a RRC )radioresource connection*. && is a stack structure, in which the &As are located.

Therefore, if we need to move the && )in the case of a handover from one

TS to another*, then we need to move the whole &&.

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Se!!ion management

8N0N

0N2 8onnetion

0adio ess earer

0N2 8onnetion

0 a d i o

3 e s

s . e a

r e r

008 8onnetion

:

2aketNet#ork

8iruit #ithedNet#ork

2aket 7ata er(ie

%eeh er(ie

5ideo er(ie

0adio ess earer

i"ure 1A. The re$ationshi% !et#een the and in the 9TN

As the above figure illustrates, the different &As are received by the &# and

combined together to form a single RRC connection. The 71 Specifications

make provision for procedures that allow for the &A to be added, modified,

and removed. This would happen if the subscriber needed an additional service

)for example, downloading email*.

To control the connection between the network and the mobile, a signalling

protocol called ra'io resource control is used. y use of the protocol, the

network can carry messages that are reuired to set up, modify and release radio

resource connection.

Stu#ent E:erci!e;an you think of an e+am%$e #here it may !e neessary to modify the radioresoure onnetionE

*" E:am7$e; Sim7$ifie# %earer e!ta%$i!9ment for a ca$$

The UMTS bearer service manager in the S1S# reuests a bearer set(up

between the MT and itself. "t send a &A Assignment reuest to the radio

resource control unit &#. The bearer control messages are exchanged between

S1S# and &# with &A#A/ messages. &A#A/ stands for &adio Access

#etwork Application /rotocol.

-ollowing the UMTS specific &A Assignment &euest message, the "ub

bearer between S1S# and &# can be set up in accordance to the reuired

uality of service parameter. etween S1S# an &# the "ub bearer is

nowadays a AA!I virtual channel.

Then, a "ub bearer between #ode and &# can be established. This bearer

will be later on used for user data transport and is an AA!8 virtual channel.

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A signalling connection already exists between the U% and the &#. This

connection is used to send the &adio Set(up earer message to the U%. The U%

is informed about the physical layer characteristics, MA layer characteristics

)e.g. puncturing, data rate*, &# modus )e.g. acknowledged6unacknowledged

mode*, etc.

The &adio !ink &econfiguration message informs the #ode among others

about the physical and MA layer characteristics of the Uu interface

transmission.

The #ode confirms this message by returning a &adio !ink onfiguration

omplete message.

The U% confirms the &adio earer Set(up message with the &adio earer Set(

up omplete message.

#ow the bearer between the U% and the &# exists. The &# returns the &A

Assignment omplete message to the S1S#, with which the UMTS bearer

between U% and S1S# is established.

/lease note, that this example is highly simplified. The bearer establishment

within UT&A# is very complex and allows a wide range of different options.

Uu Iub Iu

RAB Assignment Request

RAB Assignment Complete

SGSNRNC

Node B

Iub bearer set!up+AA) - virtual channel

Iub bearer set!up+AA) virtual channel

Radio Bearer Set- up Complete

Radio Bearer Set-up

Radio Link Reconfiguration

Radio Link Reconfiguration Complete

i"ure 15. esta!$ishment =sim%$ified>

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Se!!ion management

*2 Managing t9e %earer ,9en t9e !u%!cri%er i! mo'ing

As a subscriber moves through the network, the radio resource connection must

follow. The below figure illustrates a network with the path of a bearer being

connected from end to end )U% to MS and U% to S1S#*. As the mobilemoves, the signal it receives from the serving TS will change )possibly

decrease as in the below example* and the signal received from a neighbouring

TS will increase.

"t makes sense that the mobile should receive the signal from the TS with the

best signal uality and strength. 3ne characteristic of a $MA network is that

there could be simultaneous connections between different base stations and the

mobile. "t is the same information, @ust being transmitted and received by

different sources.

3GSGSN

RN

3GMS

RN

RN

Mo%i$e 9a! a !ing$e

RR

i"ure 16. The initia$ situation of an end-to-end !earer onnetion

The base stations that have simultaneous radio resource connections to the same

terminal are known to belong to an acti(e set. As the mobile moves, the base

stations are constantly being added and removed from the active set.

3ne common uestion that students ask is why use the extra resources, surely itwould be better to @ust use the one connectionJ "n principle this is true, but by

transmitting the signal from different sources there are advantages in gain that

can be achieved. "n theory, we are able to decrease the interference and power

in the radio network, therefore increasing capacity.

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* Mo%i$it. management

Note for !e$f>!tu#.ingKou will notice that this chapter uite much repeats the concepts from 1SM and

1/&S. ut, please be aware that some new concepts are introduced in this

chapter too.

As the user terminals are not fixed to certain positions, the network must keep

track on where the mobile is located. The system must at least be capable of

knowing the geographical area in which the subscriber is located. As in 1SM

networks, UMTS has a cellular architecture that allows the network to identify

the subscriber. As discussed in the previous section, the network maintains

information about the location of a subscriber, and the procedures are specified

to allow a constant updating of these databases as the subscriber moves aroundthe network, and also from one network to another.

3G

SGSN GGSN

RNC

3G

MSC

3G

SGSN

GGSN

RNC

3G

MSC

3G

MSC

Core Networ/

*oreign Networ/

Ra'io Access!"R

AuC

#IR Su&&lementary Ser(ices

"ocation +&'ating

"ocating the Subscriber

Ser(ice Information

i"ure 17. The ro$e of the ) as the entra$ised data!ase

The 2ome !ocation &egister )2!&* is the central database that stores

information on the subscriber, such as the "MS" and MS"S$#. The 2!& also

stores information on which serving MS and S1S# the subscriber can be

found.

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Se!!ion management

Also in the 2!& we store information on the subscriber0s service profile. "n

other words, we have a record of the different services )teleservices,

supplementary and packet services* that the subscriber can6cannot use.

Therefore, if the network needs to locate the subscriber in the case of a mobileterminated call, or if the network needs to check if the subscriber is valid, then

all reuests are sent to the 2!&.

*" e$$u$ar arc9itecture

The smallest entity within the radio network is known as a cell, which is being

served by a base station. The operating siCe of the cell )CI* can change

geographically depending on the parameters used. The cells are grouped

together geographically into location areas )"A*, routing areas )RA*, andUT&A# registration areas )+RA*.

!A 9 !ocation Area )MS.*&A 9 &outing Area )S1S#*U&A 9 UT&A# &egistrat ion Area )&#.*.ell 9 .ell )&#.*

CE)) URA CE))

URA

R/U"I%$

AREA +RA

CE))

/osition 9 /ositioningService )UT&A#*

CE))

CE))

CE))

CE))

CE))

CE))

CE))

CE))

R/U"I%$

AREA +RA

)ocation Area +)A

i"ure 18. 9:T e$$u$ar arhiteture

The above figure illustrates the structure of the network. This may look

confusing and overly complex. The reasoning behind the structure is to make

UMTS backward compatible with 1SM and 1/&S. The location areas are used

in the circuit switched domain as the routing areas are used in the packet

switched domain. A single cell can belong to both a !A and &A and this

information is used by the core network for routing information to the radio

access network )&A#*.

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"n 1SM, two separate connections are made for circuit and packet switched

data. "n UMTS, there is a single connection that can carry multiple bearers.

Therefore, to reduce the excessive amount of signalling that may occur, an

UT&A# registration area )U&A* is introduced to more intelligently monitor the

location of a subscriber in the &A#.

Stu#ent Re'ie,;One : an ha(e many s' !ut an annot ross :s. an rosss' !ut not :s. e$$ annot !e$on" to different or F they must !euni*ue. e$$ an !e$on" to more than one 9.

Net,or- $ocation area!

The location area )!A* is used in the circuit switched domain. The !A consists

of cellsB minimum is one cell and the maximum is all the cells under one 5!&.

Thus, the maximum siCe of one !A could be the same than 5!& area.

"n the location u&'ate procedure the location of the U% is updated in the 5!&

with !A accuracy. This information is needed in case of mobile terminated callB

the 5!& pages the desired U% from the location area it has performed the latest

location update.

"t should be noted that in other respects than the 5!&, the !A does not have any

other hardware bindings. -or instance, one &# may have several location

areas or one location area may cover several &#s.

Code LA MNC MCC LAI ++=

'here the M and M# ) see previous section* is the same as in "MS"

number. The !A code is @ust a number identifying !A. !A" is uniue number

throughout the world.

To globally separate cells from each other, the identity must be expanded and in

this case it is called cell global i'entity )1"*

The 1" value covers the country of the network )M*, the network within a

country )M#*, location area in the network, and finally the cell number within

the network.

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CI LACode MNC MCC CGI +++=



Se!!ion management

*"2 Net,or- routing area!

The packet switched domain has its own location definitions based on a routing

area )&A*. A routing area is definition(wise very similar than the !A, that is, it

is the area where the U% may move without performing the routing area update.

3n the other hand, the &A is kind of a 0subset0 of !A one !A may have several

&As within it, but not vice versa. "n addition, one &A cannot belong to two

!As. The reason why these two definitions co(exist is the possibility to have a

U% supporting either circuit or packet traffic, but not both. At the core network

side the 5!& and the S1S# can have a common optional interface, 1s, through

which these nodes may change location information. -or example, if the U%

performs a location update, the 5!& may inform S1S# through the 1s

interface that the U% should also perform routing area update in order to

guarantee packet traffic.

*"3 UTRAN regi!tration area!

As mentioned before, the reasoning for having the "s, !As and &As is to

ensure compatibility to 1SM and 1/&S networks. "n 716UMTS, an additional

grouping of cells is introduced, the +TRAN registration area )U&A*.

As the &# has greater mobility management functions, and it controls

handovers between &#s, it must identify which cells belong to which &#.

As a subscriber moves into the geographical range of the &#s serving area,

the subscriber is allocated into the ser(ing +RA. 3nly when the subscriber

moves from the control or supervision of one &# to another, the information

has to be updated.

'hen transmitting the paging signal, the &# can limit the paging to the U&A

area, thus reducing the amount of signalling in the network. S1S# uses the

&# address when routing packets for a designated user. 'ith U&A, it is also

possible to create more accurate demographic areas within the network. "t

means that we can define an U&A more flexibly than !A6&A with respect to

where people are located )and what patterns of movement they have*.

6-65758Issue 3.0





3G

SGSN

5R

Au

RN RN RN

URA URA URAURAURAURA

3G

MS

If t9e A an#/or RAc9ange!? RN ,i$$ en!uret9atu7#ate# informationi! !entto t9e core net,or-

A! t9e !u%!cri%er mo'e! from oneURA to anot9er? a

URA u7#ate i! 7erforme#

i"ure 1D. N and 9 arhiteture in the net#ork

Note! on GSM e'o$ution of UMTS

The MS and the 5!& still use the !A(based method for mobility management

functions for circuit switched operations such as S call set(up. As for 1/&S,

the 71(S1S# still works on the basis of &As. Therefore, the only new entities

are the U&A and UT&A# positioning services. Unlike in 1SM, the &# can

handle inter(&# handovers via the "ur interface. "n 1SM, the MS is alwaysresponsible for inter(S handovers. As UMTS networks are designed to work

with different types of core network, the only way that the network can identify

which cells belong to which &# is based upon the use of U&A.

ocation %a!e# information !er'ice!

Another characteristic of a 716UMTS network is that it is possible to determine

a more accurate position of the subscriber by using the +TRAN &ositioning

ser(ice. Unlike the U&A, !A and &A, which are used for controlling mobility

management )that is, subscriber location for call set(up*, the future for UT&A# positioning service is for the provisioning of services that are based upon the

subscriber0s exact location. %xamples of such services could be emergency

calls, viewing maps, and locating the nearest doctor.

The aim is to be capable of locating the subscriber within a I; ( L; m range.

There are different techniues that can be used, such as 1/S )1lobal

/ositioning System*. 2owever, this may have limitations due to line of sight,

indoor coverage, and even political reasons. 3ther techniues exist, which use

the triangulation between base stations to measure the delay in signals.

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Se!!ion management

i"ure @0. er(ie %ossi!i$ities

*2 Mo%i$it. 7roce#ure > ocation u7#ating

As the network maintains three layers of information on the subscriber0s

location )!A, &A and U&A*, there are multiple procedures used to track the

subscriber0s movements. "n practice, there are three basic types of location

update procedures• !ocation registration )power on 6 cell attach*

• Movement between area

• /eriodic update

These are explained in more detail in the forthcoming pages. "n a 1SM network

the S took no responsibility for mobility managementB instead the mobile

would contact the core networks directly to inform about a change in location.

"n UMTS, the situation is different as the &# not only keeps information on

which subscribers are in which U&A, but is also responsible for the location

updating to the core network.

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'hen location updating is active

)option that the subscriber can

enable with the exception of law

enforcement*, then the mobile isconstantly informing the network

of its current location.

This information can then be

accesses by different types of

service applications. -or example,

if an emergency call is made, the

mobile0s location can be given to

the police 6 ambulance services.




3G

SGSN

3GMS

RN

RN

56R

89en !,itc9ing on/off

IMSI Attac9/Detac9

89en mo'ing from area to area >

@n a ce$$/6A/RA/URA $e'e$

If the 50 is not informed

a!out the user then the

data is remo(ed

<6R

The 0N8 kee%s trak of the

mo!i$es #ithin the 90s. It a$so

informs the ore net#ork #hen

the su!sri!er han"es andCor

0

The ;N kee%s a trak

of the mo!i$es

erio#ica$$. o'er time if mo%i$e

#oe! 7erform an u7#ate

i"ure @1. oation u%date "eneri %roedures and information in thenet#ork

As the &# receives a location updating message, it takes responsibility for

informing the core network. The &# will update its own information about thesubscriber within the U&A and inform the S1S# and 5!&, respectively, if the

routing area 6 location area also change.

'hy bother to keep updating a locationJ The reason is that the network0s 5!&

and S1S# databases are only temporary. $epending on the parameters that the

operator use, the information is only stored for a certain time. "f there has been

no updating, it is assumed that the information is old. Therefore, to stop having

a huge amount of useless data in the network, the information is removed.

ocation area %a!e# 7roce#ure!

!ocation registration )"MS" attach* takes place when a user euipment )U%* is

turned on and it informs the 5!& that it is now back in service and is able to

receive calls. &elated to this process, the network sends the U% two numbers

that are stored in the US"M )Subscriber "dentity Module* card of the U%.

These two numbers are the current !ocation Area "dentity )!A"* and the

Temporary Mobile Subscriber "dentity )TMS"*. The network, via the control

channels of the air interface, sends the !A". The TMS" is used for security

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Se!!ion management

purposes, so that the "MS" of a subscriber does not have to be transmitted over the

air interface. The TMS" is a temporary identity, which regularly changes.

%very time the mobile receives data through the control channels, it reads the

!A" and compares it with the !A" stored in its US"M card. A generic locationu&'ate is performed if they are different. The mobile starts a location update

process by accessing the MS65!& that sent the location data.

A channel reuest message is sent that contains the subscriber identity )that is,

"MS"6TMS"* and the !A" stored in the US"M card. 'hen the target MS65!&

receives the reuest, it reads the old !A", which identifies the MS65!& that

has served the mobile up to this point. A signalling connection is established

between the two MS65!&s and the subscriber0s "MS" is transferred from the

old MS to the new MS. Using this "MS", the new MS reuests the

subscriber data from the 2!& and then updates the 5!& and 2!& after

successful authentication.

Perio'ic location u&'ate is carried out when the network does not receive anylocation update reuest from the mobile in a specified time. Such a situation is

created when a mobile is switched on but no traffic is carried, in which case the

mobile is only reading and measuring the information sent by the network. "f

the subscriber is moving within a single location area, there is no need to send a

location update reuest.

A timer controls the periodic updates and the operator of the 5!& sets the timer

value. The network broadcasts this timer value so that a U% knows the periodic

location update timer values.

The location registration procedure is similar for both circuit and packet

switched domains. "n case of packet switched domain the MS65!&s are

replaced with S1S#s.

'hen the 5!&6S1S# is changed, the new 5!&6S1S# sends information about

this change to the 2!&. The 2!& responds by sending the subscriber

information to the 5!&6S1S#. "f the subscriber had earlier location

information present in the 2!&, the 2!& cancels the previous location.

IMSI attac9/#etac9 (circuit !,itc9e#)

"n the circuit switched domain the U% may have two states, attached and

detached. "n the attache' state the U% is able to handle transactions and it is

active in the network. The U% continuously analyses its radio environment,

!A and cell identities being 0visible0. 'hen the U% is switched off, 'etache',

it stores the latest radio environment information into its memory and informs

the network that it is now being switched off. The 5!& stores this state change

and the U% is not tried to be reached in case of mobile terminated transaction.

'hen the U% is switched on again, it first checks whether the radio

environment matches to the one it has in its memory. "f it matches, the U% @ust

informs the 5!& that it is now attached again and able to handle transactions. "f

not, the U% performs a location area update.

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Routing area u7#ate (7ac-et !,itc9e#)

As a procedure, the routing area u&'ate is very similar to the location update

and it is performed for the same purpose. /eriodic routing area update is used

for checking that a U% that has not performed any routing area updates for some period of time is still reachable.

The U% performs a cell u&'ate )also cell reselection* when it changes cell

within a routing area in &eady mode. This could be compared to a handover in

UMTS61SM for circuit switched connections. ell update and routing area

updates halt possible reception or sending of data. The possibility of buffering

data in the Serving 1/&S Support #ode )S1S#* can be in such cases.

SGSN,1

RNC,1

RA,1

l' cell New cell

i"ure @@. The routin" area u%date

'hen the U% changes cells between the different routing areas, it performs a

routing area update. There are two types of routing area updates the intra,

SGSN routing area u&'ate and the inter,SGSN routing area u&'ate. 3ne

S1S# can manage many routing areas.

"f the new routing area is managed by the same S1S# as the old one, an intra(

S1S# routing area update is performed.

"f the new routing area is managed by a different S1S#, an inter(S1S# routingarea update is performed. The old S1S# then forwards user packets to the new

S1S#.

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Se!!ion management

e$$ attac9/#etac9

"n the core network packet domain the MM(state changes during the packet

switched connection, and it can be said that the MM(state mostly depends on

the activity of the connection. That is, when there are packets to send or receive,

the MM(state of the connection is MM,connecte'. 'hen there is nothing to

transfer, the MM(state of the connection is MM,i'le. The MM,'etache' state

has the same meaning in both of the # domains.

D e t a c h D e t a c hP a c k e tA t t a c h

P a c k e tA t t a c h

P a c k e t R e c e i v e d P a c k e t R e c e i v e d

R a d i o L i n k R e l e a s e I u C o n n e c t i o n R e l e a s e

M M S t a t e s i n U E : M M S t a t e s i n S G S N :

i"ure @3. :o!i$ity mana"ement state dia"ram in %aket domain

"n order to utilise the 71 network resources )such as radio bandwidth* as

effectively as possible, the MM(state management is as such not enough for the

packet switched )/S* traffic. "n /S traffic, the traffic delivered can be presented

as occasional packet bursts. etween these bursts the connection is not used.

This leads to the situation where it is reasonable to 0cut0 the connection through

the network in order to make the network resources available for other active

connections. The way to suppress the packet connection, but still remain the

necessary information in both ends of the connection, is called cell attach 0

'etach.

Note! on GRS e'o$ution to UMTS

"f you are familiar with 1/&S, the above figure about the different states may

seem confusing. "n UMTS, the &# has different RRC states depending on the

traffic situation. Therefore, the two figures are purely from the point of view of

the U% and the S1S#. -rom the point of view of S1S#, it is in MM(connected

state when there is a packet attach6received message. Signalling may be opened

to the &#, but the MM(connected state is only used when there is actual

traffic.

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ocation info retrie'a$ (circuit an# 7ac-et !,itc9e#)

"n case of mobile terminated transaction, the 1ateway MS )the first MS to

realise that this transaction is to be terminated to the same network the called

subscriber belongs to* performs the location info retrieval procedure.

In ca!e of t9e circuit !,itc9e# #omain;

This procedure starts when a MS reuests routing information for the called

subscriber from the 2!&. The 2!& checks its database and finds out the

destination MS65!& where the called subscriber has performed the location

update. The 2!& then asks the destination 5!& to provide MS&# for call path

connection purposes. The 5!& responds by giving a MS&#, which the 2!&

forwards to the reuesting MS. #ow the MS may start the activities for call

path connection towards the target MS65!&. 'hen the call path is established

up to the MS65!&, the called subscriber can be paged.

In ca!e of t9e 7ac-et !,itc9e# #omain;

This procedure starts when the 11S# reuests routing information for the

called packet data subscriber from the 2!&. The 2!& checks its database and

finds out the latest S1S# where the subscriber has performed the routing area

update. The address of this S1S# is submitted to the 11S# for the data

connection establishment. #ow the 11S# has address information, with which

it is able to establish the GTP tunnel between itself and the S1S#. )1T/ 9

1/&S Tunnelling /rotocol.* 'hen the 1T/ tunnel is established up to the

S1S#, the paging of the called subscriber can be started.

Management of t9e UTRAN regi!tration area!

"n UMTS the &# can handle simultaneous S and /S connections to the

subscriber. oth domains use the !A and &A respectively to track the

subscriber0s location. The &#, however, must track which +RA the subscriber

is within. "n networks where the &#s are connected through "ur interfaces )as

opposed to the MS controlling handovers*, the subscribers drift through the

radio network passing from one &# to another. Therefore, the serving &#

must identify in which U&A a subscriber is located when it receives traffic for

him6her )that is, for a circuit switched connection*.

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Se!!ion management

*3 Mo%i$it. management > aging t9e !u%!cri%er

-rom the 2!&, the network is able to determine at the very least in which

location area6routing area the subscriber is located. The network )e.g. MS*will contact the MS6S1S# serving that area and reuest contact to the mobile.

The 5!&6S1S# will then send a paging message, which contains the "$ of the

subscriber on a dedicated channel in the air interface. A mobile in idle mode is

always listening to this channel.

TS TS

Paging

TS

Mobile res&on's

to &aging

&outing Area

Paging

Paging

i"ure @A. 2a"in" in the net#ork

"f the mobile is able to detect that the network is trying to contact it, the mobile

will reuest access to the network to gain a signalling channel to determine

what the network is asking )such as set up a call, or receive the SMS*.

"n 1SM, the 5!&6S1S# would ask every cell in a certain location area to send

the same paging message. "n UMTS, if the subscriber is known to be located in

a certain U&A )UT&A# registration area*, the &# can intelligently page for

the subscriber in the U&A, therefore re'ucing the signalling in the network.

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Mo%i$it. management > Roaming in anot9er net,or-

'hen a subscriber is in a foreign network, the procedures are the same. 'hen

the subscriber registers in the visiting network, it will in turn contact the homenetwork )remember that part of the IMSI code specifies the home network*. "f

the two operators have a roaming agreement and the subscriber is valid, the

subscriber information is copied into the ser(ing 5!& of the MS and the

information on the subscriber is stored in the 2!&.

%very 5!& in the world has a uni%ue a''ress. As a subscriber moves from one

network to another, the location updating proceeds as normal. The 2!& is

always informed of the uniue 5!&, in which the subscriber was last seen.

3G

SGSN

!"R

3G

SGSN

3G

MSC

RNC

!"R

3GMSC

RNC

SC

SC

!ome Networ/

$isitor Networ/

International Networ/

3 Networ/ Confirm access

1 +ser re%uests access 4IMSI Attach5

2 If o&erators ha(e a roaming agreement6 information isco&ie' to (isitor networ/ 4from $"R0!"R5

i"ure @5. oamin" in another net#ork

!et us take one example A subscriber is roaming in another network. 'hen the

network needs to contact him6her )for example to receive a video call*, the

subscriber0s location is always checked from the !"R . The 2!& will thencontact the serving MS to check that the subscriber is still located in the 5!&

)!"R re%uest*. This information is returned to the MS and a call is routed to

the foreign MS. So, the paging process can begin.

%ven if the calling subscriber is located in the foreign network, the call still has

to be initially placed back to the home MSC.

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Se!!ion management

** Mo%i$it. management 7roce#ure!

There are several different mobility management procedures, some of which

have been mentioned in this module. The following is a short list of UMTSspecified procedures. "n the following chapter we will look at some of the

procedures in their context of the session management layer

• !ocation registration )S and /S*

• !ocation update )S*

• "MS" attach6detach )S*

• &outing area update )/S*

• ell attach6detach )/S*

• !ocation info retrieval )S and /S*

• /aging )S*

• /aging )/S*

• Authentication procedure )S6/S*

• iphering procedure )S6/S*

• U% identity checking )S6/S*

• U% hardware )"M%"* checking )S6/S*

This chapter has given the initial first look at how mobility management is

achieved in a 71 network. "f you reuire more information and a detailed lookat different scenarios, please check the specifications.

The specification contains the so(called S$! figures. The figures illustrate how

signalling messages are passed from one element to another, in the seuence of

time and condition )that is, what happens in case of a failure*. Also, the

specifications give detailed information on the content of such messages.

6-65758Issue 3.0





6 Se!!ion management

"n the previous chapter we looked at the mobility management and how the

network keeps track of the location of the subscriber and the procedures it performs. "n this chapter we look at how the mobile is able to access the

network and to obtain a bearer. 'e will also cover two simplified cases of how

real time and non,real time bearers are set up in the network.

!ike the previous two chapters, the aim is to give an overall picture of the

procedures used to set up a session. More details on these procedures can be

found from the specifications.

Mobility Management (MM)

Session Management (SM)

Communication Management (CM)

Radio Resource Management (RRM)

! RA" C"

6i!er 6i!er

B8

ATM Acce!!

Internet


ontro$ $ane

Gate,a. $ane

STN2G

SGSN

3G

SGSN GGSNRN

4S

No#e 4

No#e 4

No#e 4

56R

Au

EIR

3G

MS

SESMS

4TS

i"ure @6. ession mana"ement re*uires %roedures from : and ::

As this chapter will look at the procedures used to obtain a bearer through thenetwork, the first concept to clarify is how a terminal is capable of determining

one network from another. "f you remember, each country has its own MCC

)mobile country code* and each operator within a country has a uniue MNC

)mobile network code*. This information is broadcasted by every cell in the

network. Therefore, when the mobile is activated, it is able to distinguish

between operators by checking this information.

Through co(operation between operators, the network planning of freuencies

and codes used6shared in inter(boarder areas are selected to reduce conflict.

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IMSI attac9 for an e:i!ting !u%!cri%er

"f the subscriber is already registered in the network and is still registered in the

same 5!&, the information is updated. Also the 2!& is informed of the new

information.

3G

SGSN

RNC

5R

AC

#IR 3G

MSC

3G

MSC

0N8 a$so kee%s information

a!out su!sri!ers #ithin

the 90.

" Re0ue!t ocation U7#ate (IMSI Attac9)

2 Ne, <R re0ue!t! an# recei'e! aut9entication

information an# IMSI from 7re'iou! <R

Ne, MS/<R u7#ate! 5R ,it9 ne, $ocation 5R

!en#! ac-no,$e#gement an# !u%!cri%er information

3 Aut9entication re0ue!t an# re!7on!e

6 TMSI/TMUI a$$ocation/ac-no,$e#gement

an# $ocation u7#ate ac-no,$e#gement

* 5R cance$! t9e o$# $ocation?

o$# <R !en#! ac-no,$e#gement

16

26

36

86

96

:6

i"ure @8. :o(in" the su!sri!er&s information !et#een s

!et us now assume that the mobile has moved between to 5!& areas while

being switched off. The figure above shows such a case. 'hen the user

switches on the mobile again, a location update reuest will be transmitted to

the new 5!& ):*. Then the authentication and "MS" information is copied

between the old and the new 5!& )8*. )Similar steps would take place between

the U% and the S1S# in case of a routing area update.* After a successful

authentication )7*, the 2!& is updated with the new location information, after

which the 2!& sends the subscriber information to the new 5!& )=*, and

cancels the old 5!& )I*. -inally, an acknowledge message is sent to the mobile,together with the TMS"6TMU" number )<*. The packet core domain is also

updated with the new location information.

Moreover, the &# is constantly keeping track of all the connected subscribers0

current +RAs.

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5o, to gain acce!! ,it9out interfering ,it9 ot9er mo%i$e! too muc9

Technically, when the mobile attempts to gain access to the network, it is not

aware of the power level to use. 2ence, it estimates an appropriate level. Then

the mobile sends a short burst of information, which includes a random

seuence to the random access channel. 'hen the network receives the reuest,

it will re(transmit the random part of the initial burst on a separate channel. "f

the mobile detects this signal, it assumes that the network has heard it. "f not,

the mobile must re(transmit again, but using more power. This process

continues until either the power level set by the network is reached or the

network responds. Then, the network will transmit on a different channel

information about the channel that the mobile can use, given that one is

available.

Acce!! !ecurit. in UMTS

"n UMTS reuirements for access security are not changed. "t is reuired that

end users of the system are authenticated , i.e. identity of each subscriber is

verifiedB nobody wants to pay for calls that are made by a cheating impostor.

The confidentiality of voice calls is protected in radio access network, as well as

the confidentiality of transmitted user data. This means that the user has control

of choosing the parties with whom he6she wants to communicate. Users also

want to no! that the confidentiality protection is really applied visi"ility of

applied security mechanisms is needed. #rivacy of the user0s whereabouts is

generally appreciated. Most of the time an average citiCen does not care whether

anybody can trace where he6she is. ut if a persistent tracking of users would

occur, he6she would be uite irritated. Similarly, exact information aboutlocation of people would be useful, e.g., for burglars. Also, privacy of the user

data is a critical issue when data is transferred through the network. /rivacy and

confidentiality are largely synonymous in this presentation.

Availa"ility of the UMTS access is clearly important for a subscriber who is

paying for it. #etwork operators consider relia"ility of the network functionality

to be important they want control inside network to function effectively. This is

guaranteed by inte$rity of all radio network signallingB it is checked that all

control messages have been created by authorised elements of the network. "n

general, integrity checking protects against any manipulation of a message, e.g.,

insertion, deletion or substitution.

The most important ingredient in providing security for network operators andsubscribers is crypto$raphy. That consists of various techniues which all have

roots in the science and art of secret !ritin$ . "t is sometimes useful to make

communication deliberately incomprehensive, i.e. to use ciphering )or,

synonymously, encryption*. This is the most effective way to protect

communications against malicious purposes.

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Se!!ion management

3G

SGSN

3G

MSC

RNC

!"R The IMSI an' IM#I are chec/e' 4o&tionalan' at a changeable inter(al5

"he 1)R contains information on thesubscriber, terminal, locat ion and

services. Authenti cation codes and#eys are stored and 'enerated in the

AuC

"he SIM and terminalcontain authenticat ion

#eys

Information is chec/e' from the !"R

i"ure 30. Net#ork authentiation

UMTS !ecurit. feature!

The most important security features in the access security of UMTS are thefollowing

• Mutual authentication of the user and the network

• Use of temporary identities

• &adio access network encryption

• /rotection of signalling integrity inside UT&A#

#ote that publicly available cryptographic algorithms are used for encryption

and integrity protection. Algorithms for mutual authentication are operator(

specific.

%ach of these features are described in the following subsections.

6"" Mutua$ Aut9entication

There are three entities involved in the authentication mechanism of the UMTS

system being

• 2ome network

• Serving network )S#*

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• Terminal, more specifically US"M )typically in a smart card*

The basic idea is that the serving network checks subscriber?s identity )as in

1SM* by a so(called challenge(and(response techniue while the terminal

checks that serving network has been authorised by the home network to do so.The latter part is a new feature in UMTS )compared to 1SM* and through it the

terminal can check that it is connected to a legitimate network.

The cornerstone of the authentication mechanism is a master ey K that is

shared between the US"M of the user and the home network database. This is a

permanent secret with the length of :8D bits. The key K is never transferred out

from the two locations. -or instance, the user has no knowledge of her6his

master key.

At the same time with mutual authentication, keys for encryption and integrity

checking are derived. These are temporary keys with the same length of :8D

bits. #ew keys are derived from the permanent key K during every

authentication event. "t is a basic principle in cryptography to limit the use of permanent keys to minimum and instead derive temporary keys from it for

protection of bulk data.

'e describe now the Authentication and ey Agreement )AA* mechanism at

general level. The authentication procedure can be started after the user is

identified in the serving network. The identification occurs when the identity of

the user, i.e. permanent identity "MS" or temporary identity TMS", has been

transmitted to 5!& or S1S#. Then 5!& and S1S# send an authentication

data re%uest to the Authentication enter )Au* in the home network.

The Au contains master keys of the users and based on the knowledge of "MS"

the Au is able to generate authentication vectors for the user. The generation

process contains executions of several cryptographic algorithms. The generatedvectors are sent back to 5!&6S1S# in the authentication data response& This

process is depicted in figure below These control messages are carried on the

MA/ protocol.

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Se!!ion management

V L R A u C

0 3 N 7 ? 1 < N

B 0 / 1 3 9 T N 8 ? I ?

I : 1 I

0 3 N 7 ' 3 9 T N ' B 0 / 1 ' 8 ? ' I ?

S G S N

i"ure 6.31 uthentiation ata e*uest and uthentiation ataes%onse

"n the serving network, one authentication vector is needed for each

authentication instance, i.e. for each run of the authentication procedure. This

means the )potentially long distance* signalling between S# and the Au is not

needed for every authentication event and it can in principle be done

independently of the user actions after the initial registration. "ndeed, the

5!&6S1S# may fetch new authentication vectors from Au well before the

number of stored vectors runs out.

The serving network )5!& or S1S#* sends a user authentication re%uest to the

terminal. This message contains two parameters from the authentication vector,

called &A#$ and AUT#. These parameters are transferred into the US"M that

exists inside a tamper(resistant environment, i.e. in UMTS " card )U"*. The

US"M contains the master key K , and using it with the parameters &A#$ and

AUT# as inputs, US"M carries out a computation that resembles the generation

of authentication vectors in Au. This process also contains executions of

several algorithms, as is the case in the corresponding Au computation. As the

result of the computation US"M is able to verify whether the parameter AUT#

was indeed generated in Au and, in the positive case, the computed parameter

&%S is sent back to 5!&6S1S# in the user authentication response. #ow the5!&6S1S# is able to compare user response &%S with the expected response

4&%S which is part of the authentication vector. "n the case of match,

authentication ends positively. This part of the process is depicted below.

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V L R

0 3 N 7 ' 3 9 T N

0 / 1

0 3 N 7 ? 3 9 T N

0 / 1 1 < N 8 ? I ?

U ES G S N

5 - 0 C 1 ; 1 N h e k s# h e t h e r 0 / 1 G B 0 / 1

9 / h e k s # h e t h e r t h e1 < N i s ! i " e n o u " h

i"ure 6.3@ 9ser uthentiation e*uest and 9ser uthentiationes%onse

The keys for radio access network encryption and integrity protection, namely

and ", are created as a by(product in the authentication process. Thesetemporary keys are included in the authentication vector and, thus, are

transferred to the 5!&6S1S#. These keys are later transferred further into the

&# in the radio access network when the encryption and integrity protection

are started. 3n the other side, the US"M is able to compute and " as well

after it has obtained &A#$ )and verified it through AUT#*. Temporary keys

are subseuently transferred from US"M to the mobile euipment where the

encryption and integrity protection algorithms are implemented.

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Se!!ion management

3G

SGSN

3G

MSC

RNC

!"R

Authentication codes are used tocreate a si'nal 0hich is

scrambled 0ith the data. It is

almost impossible to decode thesi'nal 0ithout #no0in' the #eys

Cipherin' is performed inthe R%C and the mobile

In UM"S, multiple air!interfacechannels are used in theconnection to the mobile

i"ure 33. i%herin" in 9:TC9TN

62 Managing a rea$ time (circuit !,itc9e#) %earer

The following section describes how a real time bearer is allocated. The whole

process is summarised in a figure at the end of this chapter, with brief

descriptions of the steps. The next two pages discuss the process in more detail.

At the first stage of any mobile originated action, a signalling channel needs to

set up between the mobile and the &#. This channel is used to verify the

US"M, to identify the subscriber, to find out what the subscriber needs, and to

perform the authentication procedures.

The mobile will reuest a connection ):*, the &# will then instruct a TS to

reserve a signalling channel )8*, and through a common channel )that is, all

mobiles in the area can share*, inform the mobile which channel to use )7*. The

mobile can then use the signalling channel to communicate with the &#.

The mobile will now inform the &# what are its service or bearer

reuirements. "f the mobile @ust wishes to perform signalling, the already

dedicated channel will be sufficient )that is, location update*.

A subscriber wishing to access the "nternet will be discussed in the next section.

Should the subscriber wish a EoS assured service )such as voice*, the &#

forwards the call set(up message to the S(# )I*. $epending how the network

is configured, the subscriber0s identity is checked before any bearer set(up

6-65758Issue 3.0





proceeds. These transactions are usually performed not by using the subscribers

"MS", but by the TMS". "f this is not available, then the "MS" is used.

The network will check if the subscriber is allowed to use the service. Also, it is

possible that the user euipment can be crosschecked to ensure that it is valid."n the case of a call, the &# informs the S(# )MS* that a traffic channel

is needed.

The MS will respond to the &# with information about the bearer it should

provide )<*. "n return, the &# will allocate the correct bearer service to mobile

in the radio network )L*. 3nce the connection is made, the &# informs the

MS that the connection is complete and the transaction can start )D*.

The system knows that a voice6video call is reuired, so the MS or Media

1ateway )M1'* understands where the end point should be.

"n this case, the subscriber wants to call to another mobile. The procedure is the

same as in 1SM, where the 2!& enuiry is sent from the MS65!& )+*. The

2!& will now reuest the MS&# )Mobile Station &oaming #umber* from the

target 5!& ):;*. The 2!& will also inform the reuesting MS of the MS&#

of the target subscriber )::*. The serving MS will now contact the target MS

in order to make the final connection to the subscriber ):8*.

The target MS will now page the called party. As the 5!& only knows the

location area of the subscriber, then all the cells in the target !A are reuested

to send a paging message ):7*. The mobile will then answer by reuesting a

signalling channel.

"f the call terminates in a UMTS network, a similar bearer assignment

procedure will happen as described in steps : ( D above. The set(up procedure

for the target subscriber starts with the allocation of a bearer for a signalling

channel. The subscriber identity is checked and a bearer for the traffic channel

is allocated. 3nce the radio access bearer is in place, the &# will respond with

a confirmation of the set(up. #ow, the two parties can start the conversation.

This process provides a basis for UMTS to add easily into an existing 1SM

network. "n case of services such as video, the core network will either have a

direct connection via an ATM network, or through a server that supports video

streaming.

"n the next figure, a simplified UMTS originated ( 1SM terminated call set(up

case is shown. This case clearly shows that specifications have as much as

possible been based on the 1SM procedures.

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Se!!ion management

U% S S&# TS MSMS65!& MS65!& 2!&

2. 1)R En*uiry

34. Send Routin' Information +MSR%

33. Call Setup Continues

35. a'in' Response

36. Setup

3-. Call Confirmed&Alert37. Conversation

-. Call Setup

8. RA9 Setup & Radio )in# Modification

7. 9earer Assi'nment Re*uest +Create ! 9earer arameters and 9indin' ID

:. 9earer Assi'nment Complete

6. RRC Setup Complete

. Radio )in# Setup

5. Radio Resource Connection Setup

3. Radio Resource Connect ion Re*uest

3. a'in'

i"ure 3A. im%$ified 9:T ori"inated H ;: terminated a$$ set-u%

Summary of the steps in the figure

:. A ra'io resource connection reuest for a signalling channel is reuested.

8. The &# sets up the ra'io lin/ between the base station and itself.

7(=. RRC set,u& )downlink* and RRC set,u& com&lete )uplink* messages.

I. Call set,u& message to the MS65!&. Security procedures are also

performed )not shown in the figure above*.

<. earer assignment re%uest. "n this step, the bearer parameters

are definedB also a binding identification number is allocated. inding "$ is

used to tie together control information with user data for a certain

connection.

L. Ra'io access bearer set,u& and ra'io lin/ mo'ification. 1iven the inputs

from the MS65!& concerning the bearer, the &# allocates an

appropriate radio access bearer )&A* in the air interface. Also the radio link between the TS and the &# is modified in accordance with the

bearer need.

D. The &# informs the MS65!& that the bearer has been assigne'.

+(:L. Since the circuit switched core network )S(#* is common for UMTS

and 1SM, the call set(up procedures within the # are the same, including

2!& enuiry, MS&# allocation, etc. #ote also that for calls terminating in

a UMTS network, a bearer and a radio link in the terminating side should

be allocated in a similar way as in the originating side.

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Note! on GSM e'o$ution in t9e No-ia !o$ution

The function of the MS is the same as in 1SM. The new element Me'ia

Gateway 4MG.5 for 3G,MSC is responsible for converting the "u )UMTS*

messages to be compatible with the MS )A(interface*. The effect is that the

MS recognises and treats UMTS calls in a similar way than 1SM calls.

The M1' for 71(MS )71("'U* also has to convert the ATM connection

into /M to make it compatible with the MS. The "u interfaces offer more

service possibilities than the A(interface. Therefore M1' also supports these

services. Unlike in 1SM, the voice transcoders )which are based upon adaptive

multi(rate codecs, AM&* are located in the Media 1ateway.

-urthermore, the 71// Specifications have finally stated that the transcoding

function also logically belongs to the core network, which is the most logical

solution, as it allows more cost(efficient transmission.

Managing a non>rea$ time (7ac-et) %earer

This chapter describes the /$/ context activation and the allocation of a non(

real time bearer. The whole process is shown in figures at the end of the next

page. &eferences to the different steps are found in the text below. The /$/

context terminology and the 1T/ )1/&S tunnelling protocol* are discussed

after that. The last part of the chapter shows the signalling when the user uits

the connection.

The same way as the circuit switched )S* management is based upon 1SM,

the management of packet switched )/S* bearers is based upon 1/&S. The process also starts in the similar way, as the mobile first reuests a signalling

channel from the network ):*. At this stage the &# is not yet aware what

service the subscriber wishes to use, therefore it will allocate a dedicated

signalling channel )8(7* and inform the mobile which channel to use. An

acknowledgement is also sent from the mobile.

#ow it is time for the mobile to reuest a bearer. "n this reuest are, for

example, access point name )A/# ' and the "/ address )if the field is empty,

then a dynamic "/ address needs to be allocated*. The A/# is a symbolic name

for a network interface in the 11S#. The interface leads to an external packet

network. 3ne 11S# could have several different access points to different

networks )=*.

Then, the S1S# checks the subscription data. %arlier, when the subscriber

made a routing area update, the S1S# received the subscriber information from

the 2ome !ocation &egister )2!&*. Also, security information for

authentication and encryption is stored in the S1S#. "t is thus possible to

authenticate the U% )US"M* )I*. Also "M%" checking may be performed. "f

"M%" checking is performed, then the %uipment "dentity &egister )in 2!&* is

interrogated )not shown in the figure*.

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Se!!ion management

The next step of context activation is to find the reuested 11S# and send the

reuest for context creation to it. The S1S# gets the 11S# "/ address from the

$omain #ame Server )$#S* )<(L*. The $#S finds the correct 11S# "/

address based on the access point name )A/#*.

The S1S# now sends a 0reate /$/ ontext &euest0 message to the 11S#

)D*. The reuest includes the A/# and the proposed tunnel identification )T"$*.

T"$ consists of the "MS" number and the network service access point identifier

)#SA/"*. #SA/" is used as a reference number of the /$/ context.

The 11S# now selects the access point it will use )not shown in the figure*.

The A/# is associated with the external network the subscriber wants to use. "t

is a physical or logical interface in the 11S#. 3ne could say that the access

point is similar to the default gateway defined for a normal "/(subnetwork − it

is a point out from the subnetwork. -or the U%, the access point is its >default

gateway?. "n the case of a dynamic address, the 11S# or an external network

element can issue the "/ address. The external element may be a $ynamic 2ost

onfiguration /rotocol )$2/* server, which issues dynamic addressing

information. The external element might alternatively be a &emote Access $ial

"n User Service )&A$"US* server, whose primary function is user

authentication.

"n )+* the 11S# sends a 0reate /$/ ontext &esponse0 back to the 71(S1S#,

which includes given "/ address, T"$ confirmation, and a charging "$.

This is followed by ):;* the 71(S1S# sending a bearer assignment reuest

)reate* to the &#.

The &# will then modify the radio link and set up the bearer over the air

interface )::*.

'hen this is done, the &# will send a message to 71(S1S# to notify that the

bearer assignment is completed ):8*.

-inally, the 71(S1S# can send an 0Activate /$/ ontext Accept0 message to

the U% ):7*. The 71(S1S# is now ready to route user traffic between the user

euipment and the 11S#.

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+. reate /$/ ontext &esponseB $yn. "/(address, harging "d

D. reate /$/ ontext &euestB A/#, $ynamic "/ Address

U% S &# 71(S1S# $#S 11S#(:

:8. earer Assignment omplete

:. &adio &esource onnection reuest

8. &adio !ink Setup

7. &adio &esource onnection Setup 6 omplete

=. /$/(ontext Activation &euest ( )Access /oint #ame, EoS, "/ address if available*

::. &A Setup 6 &adio !ink Modification

:7. /$/ ontext Activation Accept #SA/", given dynamic "/(address, offered EoS

:;. earer Assignment &euest )reate* #SA/", offered EoS

I. Authentication

<. 11S# address resolution &euest )A/#*

L. 11S# address resolution &esponse

GTP P)+P)P P)+ GTP P)+

/$/ /acket $ata /rotocolA/# Access /oint #ame1T/ 1/&S Tunneling /rotocol

i"ure 35. 22 onte+t ati(ation

A very important concept of the packet switched session management is /$/

context )/$/ 9 /acket $ata /rotocol*. The /$/ context is used for two

purposes for /$/ address allocation to the user and to make a logical

connection with the reuired6desired EoS )Euality of Service* level through the

71 network. The /$/ context is an entity defining all reuired information for

the U% H network connection establishment. -rom the session management

)SM* point of view, the /$/ context has two states, acti(e and inacti(e.

The inacti(e state means that the packet data services related to a certain /$/

address are not activeB the network does not have any routing information

available for that /$/ address and thus it is not possible to transfer any data. "f

the location of the U% changes, the /$/ context information is not updated.

"n SM acti(e state the network has routing information available and it is possible to transfer data between the U% and the network. Also the U% location

information is updated in the /$/ context.

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# P D P C o n t e $ t A c t i v a t i o n # P D P C o n t e $ t D e a c t i v a t i o n ( l a s t )# P a c k e t D a t a D e t a c h

# P D P C o n t e $ t A c t i v a t io n R e % e c t e d

# P D P C o n t e $ t A c t i v a t io n# P D P C o n t e $ t M o d i & ic a t i o n# P D P C o n t e $ t D e a c t i v a t i o n

i"ure 36. 22 onte+t states

The figure illustrates how the different /$/ context procedures are used in

different session management states. 3ne allocated /$/ address may have

many /$/ contexts and one /$/ context always has one EoS class )EoS

profile*. This makes it possible to have many packet data connections, each of

them simultaneously having a different EoS. The U% may, for instance, be used

for software downloading and web browsing at the same time.

As the network connection is established, packets of data in the /$U are

transferred through the network by using different types of protocols.

etween the mobile and the radio network controller )&#*, the packet data

protocol is used. etween the &#, 71(S1S#, and the 11S# the packet of

"nternet data is transferred in the GPRS tunnelling &rotocol )GTP*.

U ! e r

7 a c - e tU!er

3 ac - e t U!er

7ac-etU!er

7ac-et

GGSN

T9e !tream of container!formin a tunne$

U!er 7ac-et

3G,

SGSN

RNC

i"ure 37. The ;T2 tunne$

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The user data packets are carried from &# to 11S# via 71(S1S# in

>containers?. 'hen a packet from an external packet network arrives at the

11S#, it is inserted into a container and sent to the S1S#. The container is

then opened and packed into a new container towards the &#. The stream of

containers from &# all the way to the 11S# is totally transparent to the user."t seems as if the user is connected directly via a router to an external network,

or to an application. "n data communications this type of virtual stream of

containers is called a tunnel H the 1S#s and &# perform tunnelling of user

packets.

9/ 0N8 3;-;N

1. 272 8onte+t 7eati(ation 0e*uest

@. 272 8onte+t 7eati(ation e%t

3. earer ssi"nment 0e*uest=0e$ease>

A. 0adio -ink 0e$ease

5. earer ssi"nment 8om%$ete=0e$ease>

i"ure 38. The user *uits the onnetion

Although the connection may remain active for some time, the mobile may

deactivate the /$/ context. This is shown in the figure above. A reuest is sent

from the mobile, through the &# to the 71(S1S# to release the resources

):(8*. 3nce the mobile is deactivated, the radio resources are then released

)7(=*. -inally, the &# sends an acknowledgement to the 71(S1S# )I*.

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+ ommunication management

A UMTS network is a platform to give the operator0s the best solution to

provide a varied amount of services. The subscriber0s applications and controlcomponents sit upon the bearer. Therefore, communication management in

UMTS is all about managing mobility, security and charging of a bearer.

The below figure illustrates the services and control of the services that sit upon

the physical connection. "t is the role of communication management to route

the bearer to the high application layers, manage the connection through

mobility management, and handle the bearer security and charging for the

session.

Networ/ A&&licationIntelligence

Connection

Ser(ice an' customer

a&&lication control

N Subscriber;s ser(ice &rofile

, location information

, billing of ser(ice

, &ush control

, &ersonalisation, etc

N Security

N Mobility

N Charging information collection

#n' user a&&lication N #mailN M,MT SMS

N etc

i"ure 3D. untions of ommuniation mana"ement

The communication management needs the services of the lower layers, as

these maintain the bearer.

This chapter exemplifies the high level functions in terms of the call control

process for circuit switched calls. Also, there are a few notes about emergencycalls and charging.

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a$$ contro$ for circuit !,itc9e# (rea$ time) ca$$!

all control is a high(level name describing the functions reuired for incoming

and outgoing call handling within a switch. 1enerally speaking, the switchshould perform three activities before a call can be connected through. Those

activities are number analysis, routing, and charging. all control can

functionally be divided into three phases, which the call attempt must pass in

order to perform through connection.

#umber analysis is a collection of rules how the incoming call should be

handled. #umber analysis investigates both the calling and called numbers and

makes decisions based on the rules defined. #umber analysis is performed both

in call control /hase " and /hase "". "n /hase " the switch checks whether the

called number is reasonable at all and if any restriction such as call barring is to

be applied with the calling number.

I I I I I I

' a i l # n s u c c e s s & u l S e t u # R e s t r i c t i o n s# n r e a s o n a b l e " u m b e r s

' a i l # * r o n g D i a l l i n g# I n t e r * o r k i n g ' a i l u r e

' a i l # C i r c u i t s " o t A v a i l a b l e# S e r v i c e " o t S u o r t e d

" u m b e r A n a l y s i s R o u t i n g

C h a r g i n g

A c a l l c o m i n g i n A c a l l g o i n g o u t

i"ure A0. a$$ ontro$ %rini%$es

"n call control /hase "" the system concentrates on the called number. The

nature of the call is investigated "s it an international or national call and is

there any routing rule defined for the called number at allJ "n addition, the

system checks if the call reuires any inter(working euipment )like a modem*

to be connected and if the call is chargeable or not. Also statistics for this call is

initiated in this phase.

As a successful result of call control /hase "", the system knows where the call

attempt should be routed. 'hen the correct destination for the call is known, the

system starts to set up channel)s*6bandwidth towards the desired destination by

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Se!!ion management

using, for instance, "SU/ signalling protocol. $uring the call, the switch stores

statistical information about the call and its connection and collects charging

information )if the call was @udged to be chargeable*. 'hen the call is finished,

call control /hase """ takes care of releasing all the resources related to the call.

+2 Generation an# co$$ection of c9arging #ata

The 71// Specifications give a detailed list of reuirements for the type of

$& )charging data record* to collect. The harging 1ateway, MS, 2!& and

many elements within the service platform generate $&s, which describe

different events in the network. An event could be a call, SMS, data usage,

location update, and in fact almost any different type of network activity.

3perators select what causes a $& to be generated. The $&s are transferredto the illing entre where the information is collected and priced.

RNC

illing Centre

Charging Gateway

!"R

3G

SGSN

3G

MSC

GGSN

CDR +Char'in' DataRecords are sent to the

9illin' Centre

i"ure A1. o$$etion of har"in" data

As part of the evolution from 1SM61/&S towards UMTS, the amount ofinformation contained in the $& has been increased to include details of the

service uality and the network elements used.

Also, the UMTS Specifications describe features that allow the subscriber to see

more information on the cost of a service. This network feature is called Ao

)Advice of harge* and is a supplementary service, which give the subscriber

details of the service cost almost immediately.

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Note on 9an#$ing emergenc. ca$$!

"n UMTS )and in the evolved 1SM*, when location based servers are in place,

it will be possible to actually specifically locate the subscriber within I;(L; m.'hen an emergency call is received, the operator can check in which location

the subscriber is based and hence direct the emergency services to the scene

more uickly than today.

RNC

!"R

3G

MSC

"he MSC defines if calls areallo0ed and 0here they

should be routed to, basedupon location

3G

SGSNGGSN

To 'ifferentregional call

centres

%o chec#in' is done +alsoSIM does not need to be

active to ma#e emer'encycall

"ocation ase' Ser(er

I" location based ser0ices areused1 then the e&ergenc2 ser0ices can gain accurate

in"or&ation on thesubscriber3s location

i"ure A@. )and$in" emer"eny a$$s

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Se!!ion management

Re'ie, 0ue!tion!

/lease spend some time to complete the following review uestions. The aim of

the review is for you to reflect and apply what you have studied.

:. "n which network elements is security related information locatedJ

a. US"M

b. &#

c. Au

d. S1S#

e. #ode

f. non of all above

8. 'hich parameter identifies the subscriberJ

a. "MS"

b. "M%"

c. M

d. /(TMS"

e. TMS"

f. /"#

7. 'hich location information is known in the U%J

a. !A

b. &A

c. U&A

d. 71(MS supply area

e. 71(S1S# supply area

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=. 'hich of the following is6are characteristic)s* of a UMTS bearerJ

a. 5ariable data rate

b. Transparent through the &A#

c. $ifferent lengths of delay

d. Asymmetric connection

e. #one of the above.

I. "n the following figure, fill in the missing names of the cellular network

architecture.

<. 'hich of the following sentences about location update is not trueJ

a. "MS" attach is always made when the terminal is switched on.

b. !ocation6routing area update takes place when a subscriber moves

between !As and6or &As.

c. /eriodic location updates are not used in UMTS.

d. #one of the above.

L. The U&A )UT&A# registration area* is used by the core network to keep

track of subscribers in the network.

True ο -alse ο

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9sed !y the 8N 8 7omain

IIIIIIIIIIIIIIIIIIIIII



9sed in the 0N8


,hat other information is ke%tE

IIIIIIIIIIIIIIIIII

IIIIIIIIIIIIIIIIII

IIIIIIIIIIIIIIIIII

IIIIIIIIIIIIIIIIII





9sed in the 0N8


,hat other information is ke%tE

IIIIIIIIIIIIIIIIII

IIIIIIIIIIIIIIIIII

IIIIIIIIIIIIIIIIII

IIIIIIIIIIIIIIIIII



Se!!ion management

D. 'hich of the following sentences about the && )radio resource

connection* is trueJ

a. "t is only used in 1/&S networks.

b. "t is a collection of radio access bearers over the air interface.

c. "t is a wireless protocol.

d. All of the above.

+. The operation of reuesting a subscriber to contact the network is called

a. "MS" attach

b. !ocation update

c. /aging

d. earer allocation

:;. 'hich of the following sentences best describes authenticationJ

a. Security of the user information on the air interface

b. "MS" and "M%" checking

c. Supplementary service status checking )by the subscriber*

d. A process used by the 11S# to determine firewall access

::. "n UMTS a terminal has two states, i'le and connecte'. "n the followinglist, identify which state the mobile is in.

a. The mobile is in OOOOOOOOOOOO mode when it is camping on a cell.

b. The mobile is in OOOOOOOOOOOO mode when it does not have any

connection state.

c. "f data is being transferred from the packet core to the mobile, then

the state is OOOOOOOOOOOOO .

:8. $uring a /$/ context activation process, which information us

transmitted from the U% to the S1S#J

a. A/#

b. /$/

c. 11S# address

d. $#S address

e. T"$

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:7. 'hen a subscriber triggers an event in the network )for example a call*,

a $& is generated. 'hat is a $&J

a. harging data record which is sent to a illing6harging entre

b. aller digital reset to the MS

c. ustomer data receipt, which is a bill that is sent to the customer

d. All of the above.

:=. SMS messages can be sent via the S1S#.

True ο -alse ο

04 - UMTS Traffic Management

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