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Lehrstuhl für Rechnernetze und InternetWilhelm-Schickard-Institut für InformatikUniversität Tübingen

UMTS Networks

Leo Petrak, Dr. Christian Hoene und Prof. Georg Carle

UMTS Networks and Internet Telephony – Sommersemester 2006 2

Course Overview

MotivationStandardization issuesUMTS architecture basicsUMTS radio link

Physical layerSignaling

UE, UTRAN, PS Domain, CS Domain Basic functionalities:

Accessing the networkTransferring dataDetaching from the networkInformation storage

MobilityQoSSecurity

ChargingUMTS Evolution: from R99 to Rel7Beyond UMTS

UMTS Networks and Internet Telephony – Sommersemester 2006 3

Radio Communication FundamentalsDividing Radio ResourcesFrequency Licensing

UMTS Radio Link – Physical Layer

UMTS Networks and Internet Telephony – Sommersemester 2006 4

Modulation QPSK Modulation used in UMTS

Fourier AnalysisWave PropagationScarcity of Radio Resources

Radio Communication Fundamentals

UMTS Networks and Internet Telephony – Sommersemester 2006 5

Radio communication uses electromagnetic waves as thetransmission medium

UEs / Base Stations emit and receive waves of the carrierfrequency f

Signal strength of a waveP(t) = P0 cos (2πft - ϕ)

Radio Communication Fundamentals I

-P0

P(t)

2πft

UMTS Networks and Internet Telephony – Sommersemester 2006 6

Information is encoded by modulating (change midway) a wave of the carrier frequency f

P(t) = P0 cos (2πft + ϕ)Phase ϕ - Phase Shift Keying

Frequency f - Frequency Shift Keying

modulate Amplitude P0 - Amplitude Shift Keying

Radio Communication Fundamentals II - Modulation

UMTS Networks and Internet Telephony – Sommersemester 2006 7

Modulation in UMTS: QPSK

UMTS uses Quaternary Phase Shift Keying (aus 4-er bestehende…)

Four possible sequences of two bits are coded:• 0 0 - phase shift of 1/4 π• 1 0 - phase shift of 3/4 π• 1 1 - phase shift of 5/4 π• 0 1 - phase shift of 7/4 π

P(t)

1/4 πphase shift: 3/4 π 5/4 π 7/4 π

Bit sequence: 0 0 1 0 1 1 0 1

UMTS Networks and Internet Telephony – Sommersemester 2006 8

Fourier Analysis: Each signal can be described as an integral (sum) of sine waves

⇒ The modulated wave is a superposition of manywaves of different frequencies of a frequencyband ∆ f It can be shown that∆ f ≥ r (bandwidth ≥ data rate)

Radio Communication Fundamentals III - Fourier Analysis

1 2 3 4 5 6 7 8 9 10110

1 2 3 4 5 6 7 8 9 1011

1 2 3 4 5 6 7 8 9 10110

0 1 1 0 0 0 1 0

T 1 2 3 4 5 6 7 8 9 1011

Signal Harmonics n

1 1. Harm.

2. Harm.

4. Harm.

8. Harm.

∑∞

n 2sin(P)(n

tP π nf t+ ϕn)

Density D(f)

f0Carrier Frequency

Bandwidth ∆ f

(f0 +1/2r)

2/r

UMTS Networks and Internet Telephony – Sommersemester 2006 9

Radio Communication Fundamentals IV - Wave Propagation

The intensity of electromagnetic waves emitted by a „point source“(e.g. antenna) decreases with distanceElectromagnetic waves add linearly

Interference of waves emitted by different sources• When waves of same frequency interfere, extraction of information difficult

– Because a modulated wave occupies a frequency band of bandwidth ∆ f , interferencemay be a problem in mobile communications

UMTS Networks and Internet Telephony – Sommersemester 2006 10

Radio Communication Fundamentals V - Scarcity of radio resources

Radio spectrum is a scarce resourceShared by many systems

⇒ It is necessary to clearly separate radio resources used by different entities, e.g.- Technologies- Users of the same technology "Multiple Access"- "user -> network" (uplink) from

"network -> user" (downlink): "Duplex"⇒ it is necessary to efficiently use radio resources

Possibilities for separating radio resources- Frequency division- Time division- Space division- Code division- Combinations thereof

UMTS Networks and Internet Telephony – Sommersemester 2006 11

Radio Communication FundamentalsDividing Radio ResourcesFrequency Licensing

UMTS Radio Link – Physical Layer

UMTS Networks and Internet Telephony – Sommersemester 2006 12

Frequency divisionTime divisionSpace division

Cellular networksCode divisionExamples: GSM and UMTS

Dividing Radio Resources

UMTS Networks and Internet Telephony – Sommersemester 2006 13

Frequency Division

Radio Spectrum is divided into frequencybands

Power emitted outside these bands must bestrictly below a certain level

To be on the safe side, unused guard bandslimit interference between frequency bands

Receivers use filtering to receive carrierfrequency of interest

Already introduced in 1900 to organizeusage of radio transmitters, e.g. on ships

Usually used in combination with otherdivision techniques

time

frequency

Frequency band 3

Frequency band 2

Frequency band 1

Guard band

UMTS Networks and Internet Telephony – Sommersemester 2006 14

Time Division

Radio Spectrum usage is divided into time slotsEach sender is assigned a time slot

To avoid collisions, all participating entities needto be synchronized

network needs to periodically synchronizeterminalsneed to consider finite traveling time of synchronization signal, depending on distance between terminal and synchronizing entity!

Guard times between slots prevent collisionsdue to imperfect synchronization

Usually used in combination with other divisiontechniques

Guard

time

frequency

Guard

time

Time slot1

Time slot2

Time slot3

UMTS Networks and Internet Telephony – Sommersemester 2006 15

Space Division

Usage of radio resources restricted to certain geographic areas (cells)

Transmission power is limiteddue to decrease of power with distance to sender, interference is limited

Re-use of same radio resource only at appropriate distance

In combination with e.g FrequencyDivision, very large areas can be covered

reuse frequency band only in distant cells

New antenna techniques (adaptive antenna arrays / MIMO) allow forming"beam" towards specific mobile

UMTS Networks and Internet Telephony – Sommersemester 2006 16

Space Division - The Cellular Concept

Space Division is today the technique of choice

patented in 1972 by Bell Labs

Instead of each antenna illuminating an area as big as possible(1G Systems), each antenna covers onlysmall area

lower transmission powermore efficient use of the spectrum => bettercoveragehigher infrastructure costsneed technique for switching moving usersfrom cell to cell: "Handover"

UMTS Networks and Internet Telephony – Sommersemester 2006 17

Code Division I

time

frequency

□ Several signals are sent in the same(wide) frequency band and the same time slot

□ Each signal is created by spreading a narrowband signal through the use of a unique user code to a multiple of theoriginal bandwidth (spreading) [Spreizung]

□ The receiver correlates the sum of thereceived signal with the (time-shifted) usercode, and thereby re-obtains the original narrowband signal (de-spreading)

□ power level of different signal needs to bealigned

□ codes need to be uncorrelated, otherwise interference

□ replanning cells becomes easier with thistechnique

code

Code 1

Code 2

Code 3

UMTS Networks and Internet Telephony – Sommersemester 2006 18

Code Division II - What are these codes?

Sequences S of 1 and -1 (chips)S = {S1, S2 , ... , Sn}, Si {-1,1}

Correlation: C(j) = Σi Si Ti+j• measures how "different" two codes S and T are• uncorrelated codes result in little interference• e.g. S = {-1, 1, 1, 1, -1, -1, 1, -1}T = {-1, -1, 1, -1, 1, -1, -1, -1}C(0) = 0, C(1) = 2, C(3) = 0,...but Autocorrelation A(j) e.g. of S:A(0) = 8, A(1) = 0, A(2) = 4,...

– Autocorrelation only high if synchronized!∋

UMTS Networks and Internet Telephony – Sommersemester 2006 19

Code Division III - Coding and Decoding

Data D(t)

-1 1 1 1 1 -1 -1 -1

Code S(t)

D(t) ·S(t)

Coding at sender

Decoding at receiverwith correct code

D(t) ·S(t) ·S(t - τ) = D(t)

Decoding at receiverwith wrong code

D(t) ·S(t) ·T(t - τ) = no data signal

Code T(t - τ)

-1 -1 1 -1 -1 -1 -11

UMTS Networks and Internet Telephony – Sommersemester 2006 20

Code Division III - Spreading

Chip rate greater bit rate • therefore bandwidth becomes higher after spreading [Spreizung]

D(f)

Bandwidth ∆ f

f0+TD

1/TD

Data D(t)

D(t) ·S(t)

TDS

D(f)

Bandwidth ∆ f

f0+TDS

1/TDS

UMTS Networks and Internet Telephony – Sommersemester 2006 21

Code Division IV- near-far effect

De-spreading at receiver works best whenpower levels of different signals are aligned. However:When senders A and B emit with same power, the signal of B at the Antenna is stronger

⇒ power control is applied constantlyAntenna Controller tells sender with what power to send

UMTS Networks and Internet Telephony – Sommersemester 2006 22

Dividing Radio Resources: Summary

Uplink / downlink (D – Duplex)

Different users (MA – Multiple Access)

Frequency Division (FD) FDD FDMA

Time Division (TD) TDD TDMA Code Division (CD) - CDMA

Space Division (SD) - SDMA

The different techniques for dividing radio resources can be combined, e.g.

• pick one technique for separating uplink / downlink• pick one technique for separating different users

e.g. FDD - CDMA

UMTS Networks and Internet Telephony – Sommersemester 2006 23

GSM: FDD + TDMA + FDMA

GSM uses a both Frequency Division and Time DivisionUplink and Downlink use different frequencies: FDDUplink and Downlink frequency band is subdivided into frequency channels, each of thesechannels is divided into time slots:

each user sends on a particular frequency band, on a particular time slotIn GSM 900 have

25 MHz per direction124 frequency channels à 200 kHz per directioneach frequency band has 8 time slots

time

frequency

UMTS Networks and Internet Telephony – Sommersemester 2006 24

Flash OFDM: FDD + TDMA + FDMA + Frequency Hopping

Uses both Frequency Division and Time Division as GSM plus frequency hopping

Allows flexible assignement of bandwidthSimplifies frequency planningResults in spread spectrum, just as CDMA

time

frequency

UMTS Networks and Internet Telephony – Sommersemester 2006 25

UMTS: WCDMA I

UMTS uses two different methods for separating radio resourcesFDD + CDMA (UTRA FDD) (most popular method)TDD + TDMA + CDMA (UTRA TDD)

FDD + CDMA for UMTS is called WCDMA(Wideband CDMA), because compared to cdmaOne it uses a higher chip rate

chip rate is 3,84 Mega chips / s• chip rate is fixed• in cdma2000, chip rate can vary

Qualcomm owns key patents in UTRA FDD and cdma2000They managed to standardize them

UMTS Networks and Internet Telephony – Sommersemester 2006 26

UMTS: WCDMA II - why CDMA?

Very resource efficientpossibly more efficient than FDMA and TDMA

Resistance against interference and noise:any undesired signal will be spread when decodingInterception by adversary more difficult

signal strength can be lower than thermal noise => hide signal• Because total power in signal spread out over more frequencies

needs to know code

Can reuse frequencies in neighboring cellssimplifies network planningsimplifies introduction of more antennas

Allows flexible bandwidth assignementby varying spreading factor (chips per bit)

UMTS Networks and Internet Telephony – Sommersemester 2006 27

UMTS: WCDMA III - Orthogonal Codes

Constructed from a "tree", called OVSF Code TreeSequences on same hierarchical level or originating from different branches areorthogonalHigher bandwidth (larger bitrate) sessions are assigned shorter code Cshort

such that the overall chiprate does not exceed maximum chip ratethis blocks usage of all codes branching off code Cshort

• they would not be orthogonali.e. (quite logically) a high bandwidth session occupies more resources (codes) and thus reducesbandwidth available to other sessionsUse between 1 to 256 chips per bit

SF = 1 SF = 2 SF = 4

Cch,1,0 = (1)

Cch,2,0 = (1,1)

Cch,2,1 = (1,-1)

Cch,4,0 =(1,1,1,1)

Cch,4,1 = (1,1,-1,-1)

Cch,4,2 = (1,-1,1,-1)

Cch,4,3 = (1,-1,-1,1)

SF - Spreading Factor

UMTS Networks and Internet Telephony – Sommersemester 2006 28

UMTS: WCDMA IV – Orthogonal Codes cont’

Two types of codesOrthogonal codes

• Generated from code tree• Orthogonal correlation

– High autocorrelation if synchronized» Autocorrelation mediocre if unsynchronized

– Zero correlation between different codes if synchronized» Non-zero correlation if unsynchronized

Pseudo Noise codes• “Randomly generated” with particularly properties• “Quasi orthogonal” correlation

– High autocorrelation if synchronized– Almost zero correlation between different codes even if unsynchronized

UMTS Networks and Internet Telephony – Sommersemester 2006 29

UMTS: WCDMA V - Code Distribution

Uplink Direction Downlink DirectionScrambling Codes (Pseudo Noise Code)

User separation Cell separation

Channelization Codes(Orthogonal Code)

Data and control channels from same UE

Users within a cell

Spreading Code Channelization code x scrambling code

Problem: Synchronization between cells and between UEs hard to achieveEach signal is spread with the spreading code, i.e.channelization code x scrambling codeChannelization codes spread all user data to same bandwidth

Have different lengthDownlink (Network -> UE):

Neighboring cells use different scrambling codes ("cell ID")Each UE is assigned a different channelization code

=> UE receives data with unique spreading codeUplink (UE -> Network):

Each UE is assigned a different scrambling codeEach UE may use any channelization codeThis allows UE to manage bandwidth of its sessions independently

UMTS Networks and Internet Telephony – Sommersemester 2006 30

UMTS: WCDMA VI - Macrodiversity

SF - Spreading Factor

WCDMA support multipath propagationSignals can take different path from sender to receiver

• Due to reflection, diffraction,...• Signal may be picked up by more than one antenna

Signals are collected and aggregated at receiverImproves reception qualityThis is called Diversity

Utilizing multipath propagation via more than one antenna is calledMacrodiversity […Mehrfachverbindungen]

Usually the further away from the antenna, the stronger the signal a UE has to emit (near-far effect)This leads to interference with neighboring cellsMacrodiversity allows reducing emission power

UMTS Networks and Internet Telephony – Sommersemester 2006 31

Radio Communication FundamentalsDividing Radio ResourcesFrequency Licensing

UMTS Radio Link – Physical Layer

UMTS Networks and Internet Telephony – Sommersemester 2006 32

IMT 2000 Worldwide Frequency Plans

1850 1900 1950 2000 2050 2100 2150 2200 2250 MHz

1850 1900 1950 2000 … 2100 2150 2200 2250

2010 MHzITU allocations

IMT 2000 IMT 2000

JapanKorea (w/o PHS) IMT 2000 MSSMSSIMT 2000PHS

1885 MHz 1980 MHz

1885 MHz 2025 MHz 2110 MHz 2170 MHz

Europe UMTS MSSDECT UMTS MSSGSM 1800

1880 MHz 1980 MHz

UMTS MSSChina UMTS MSSGSM 1800

North America

2160 MHz

Reserved MSS1895 1918 MHz

MSSA D B E F C A D B E F CPCS

DECTGSM 1800

UMTS FDDUMTS TDD

20 20 60 30 15 60 3060

MSSMobile Satellite System

UMTS Networks and Internet Telephony – Sommersemester 2006 33

IMT-2000 Licences in Germany

FDD Frequencies

TDD Frequencies

Source: www.regtp.deLicences oblige operator to cover 25% of the population by end of 2003, and 50% by end of 2005Licences expire end of 2020Mannesmann became Vodafone, VIAG became O2, Group 3G became QuamMobilCom returned licence

UMTS Networks and Internet Telephony – Sommersemester 2006 34

Summary

UMTS uses QPSK (Quaternary Phase Shift Keying) as modulation technique

UMTS employs WCDMASignal is spread using orthogonal codes

The higher the bit rate of a signal, the less it is spread

Because of near-far effect, power control is important

Multiple propagation paths of signal can be combined to improve receptionquality

• Reception with different antennas: Macrodiversity

Lehrstuhl für Rechnernetze und InternetWilhelm-Schickard-Institut für InformatikUniversität Tübingen

Warum ist das Handy-Telefonierenso teuer?

Warum ist UMTS so teuer?

UMTS Networks and Internet Telephony – Sommersemester 2006 36

UMTS Auktion – Kosten für jedermann!

Gesamterlöß war 100 Milliarden DM = 50,5 Milliarden €(August 2000)Jährlich Zinsen für diesen Betrag50.000.000.000 * 4% = 2 Milliarden € pro Jahr

Monatliche Tilgung über 15 Jahre sind 395,40 Mio € pro Monat

“Vodafone D2 übertrifft Marke von einer Million UMTS-KundenJahresziel bereits jetzt erreicht”, 21. November 2005

Ungefähr 2,5 Mio (UMTS) oder 45 Mio (Handy) Kunden zur Zeit

394,40/2,5 = 157,76 € pro UMTS-Kunde pro Monat

Oder 394,40/45 = 8,76 € pro Handy pro Monat

UMTS Networks and Internet Telephony – Sommersemester 2006 37

Wirtschaftspolitische Einschätzung

Kommentar des finnische Kommunikationsministers Kimmo Sasi18.09.2002, Tageszeitung "Kauppalehti"

"Ich rate Deutschland zu überdenken, ob man zum Rückkauf derLizenzen von den Unternehmen bereit ist, die sie wieder abgeben

wollen. Und man sollte sie für denselben Preis zurückkaufen, der von den Unternehmen bezahlt wurde." Der finnische Minister begründete

seinen Vorschlag damit, dass "die gesamte Telekommunikations-branche nur auf diese Weise wieder auf die Füße kommen kann".

"Deutschland und Großbritannien könnten damit die führende Position Europas gegenüber den USA in der Telebranche zerstören“

“größter industriepolitischen Fehler seit dem Zweiten Weltkrieg“

UMTS Networks and Internet Telephony – Sommersemester 2006 38

Kosten bezahlen nicht nur die UMTS-Kunden:DTAG und DAXDAX Kurse seit dem 1.1.2000:

DAX

UMTS Networks and Internet Telephony – Sommersemester 2006 39

Layer Model for the Radio Link (Uu Interface)Protocols on Uu Interface Channels

Logical ChannelsTransport ChannelsPhysical Channels

Usage Example

Radio Link Signaling

UMTS Networks and Internet Telephony – Sommersemester 2006 40

Layer Model for the Radio Link

Logical Channels

Control-plane signalling User-plane data

PHY L1

MAC

BMC

controlRRC

RLC

PDCP

Transport Channels

Legend see next slidesPhysical Channels

UMTS Networks and Internet Telephony – Sommersemester 2006 41

Layer Model for the Radio Link (Uu Interface)Protocols on Uu Interface Channels

Logical ChannelsTransport ChannelsPhysical Channels

Usage Example

Radio Link Signaling

UMTS Networks and Internet Telephony – Sommersemester 2006 42

Protocols on Uu Interface I

PHYTasks that are directly related to the air interface

ModulationError protection of type FEC (Forward Error Correction)

• Data transmitted somewhat redundantly by means of Channel Coding– „Channel Coding“ is not the same as „Channelization Codes“ (Slide Set IV)!

Messaging on synchronization, macrodiversity, fast power controlMeasurements of conditionson radio interface (handover necessary?)(de)Multiplexing of transport channels to physical channelsProviding transport channels to the layer above…

Control plane signaling

UMTS Networks and Internet Telephony – Sommersemester 2006 43

Protocols on Uu Interface II

MACMultiplexing of channels

Multiplex different flows of the same user onto the same dedicated transportchannelMultiplex flows of several users onto a shared transport channelpacket scheduling / priority controlpossibly encryption (unless done on RLC)

RLC - Radio Link Control LayerTasks related to protected transmission of data

error protection and error free data transmissionsegmentation / reassemblyflow controldirectly used by CS domain L3 functions

UMTS Networks and Internet Telephony – Sommersemester 2006 44

Protocols on Uu Interface III

PDCP - Packet Data Control ProtocolEnables independence of L3 and lower layers

• adaptations to facilitate IP on L3 (for PS domain) • Makes possible independent development of lower layers and L3

(and above)– E.g. transition from IPv4 to IPv6

header compression

BMC - Broadcast and Multicast Controlscheduling and delivery of cell broadcast and multicast messages

UMTS Networks and Internet Telephony – Sommersemester 2006 45

Protocols on Uu Interface IV

RRC - Radio Resource ControlControl and configuration of protocol stack on Uu Interface

one RRC connection for each UE, which controls the radio link for all sessions of this UE

• convenient in case of handoverhas control interfaces to all other radio link protocolsFDD frequency managementmobility managementouter loop power controlcollection of measurement from lower layersbroadcast of system informationtunneling of core network control information

• Session management, mobility management,…

UMTS Networks and Internet Telephony – Sommersemester 2006 46

Layer Model for the Radio Link (Uu Interface)Protocols on Uu Interface Channels

Logical ChannelsTransport ChannelsPhysical Channels

Usage Example

Radio Link Signaling

UMTS Networks and Internet Telephony – Sommersemester 2006 47

Channels

(sub)layers use Channels to transmit dataEach channel has specific properties

allows decoupling of functionality -> greater flexibilitye.g. one transport channel can carry several types of logical channels

Transport Channel 1

Logical Channel 1

Logical Channel 2

Transport Channel 2Logical Channel 3

Transport Channel 3

Logical Channel 4

Logical Channel 5

Logical Channel 6

CCTrCH

Physical Channel 1

Physical Channel 2

CCTrCH:Coded Composite Transport Channel(Connection between Transport Channeland Physical Channel)

PHY

UMTS Networks and Internet Telephony – Sommersemester 2006 48

Channels

Logical channels between RLC and MACspecific to type of information

• logical control channels for control plane signaling• logical transport channels for user plane data

Transport channels between MAC and PHYspecific to how information is transferred (quality level)

Physical channels used by PHYactual transmission on physical layer

UMTS Networks and Internet Telephony – Sommersemester 2006 49

Logical Channels ILogical Control Channels for control plane signaling

BCCH Broadcast Control Channel• distributes information that allows UEs to attach to network

– information about radio environment: power levels, network identity..

CCCH Common Control Channel• for exchange of first messages with attaching UE

– no specific (dedicated) control channel has been assigned yet

DCCH Dedicated Control Channel• for exchange of control information with attached UE

– e.g. power control

PCCH Paging Control Channel• for paging UEs

– when a UE receives a call it needs to be located

UMTS Networks and Internet Telephony – Sommersemester 2006 50

Logical Channels II

Logical Transport Channels for user plane dataCTCH Common Transport Channel

• unidirectional downlink channel• for broadcasting information to all, or a group of UEs

DTCH Dedicated Transport Channel• exchange of user data

UMTS Networks and Internet Telephony – Sommersemester 2006 51

Transport Channels ITransport Channels

Specific to how information is transferredProvide specific service quality, e.g.

• bit rate, error protection• power level, access method, etc

Data packets that are transmitted over Transport Channels are called„Transport Blocks“

• Several are transmitted simultaneously in „Transport Block Sets“Each Transport Channel is described by a set of „Transport Formats“, i.e.

• Transport Block size• Transport Block Set size• Transmission time interval

– How long does it take to transmit a Transport Block Set• Type of error protection (Channel Coding and Cyclic Reduncancy Check)

– Channel Coding: redundant transmission of information• Efficiency of Channel Coding

For each Transport Block Set transmission, a suitable Transport Format ischosen from the Transport Format Set

UMTS Networks and Internet Telephony – Sommersemester 2006 52

Transport Channels II

e.g.BCH Broadcast Channel

• downlink, fixed bit rate, high power level (needs to be audible to all)• used for BCCH

RACH Random Access Channel• uplink, random access• mostly used by CCCH and DCCH (also DTCH)

DCH Dedicated Channel• uplink and downlink, dedicated to a particular UE• one DCH may carry several DCCH and DTCH

DSCH Downlink Shared Channel• dedicated user traffic but shared by several users• very important for data traffic (no dedicated bandwidth for one user)• optional to implement

Note there is no Uplink Shared Channel• At the time of standardization no use was anticipated

UMTS Networks and Internet Telephony – Sommersemester 2006 53

Physical Channels

Transmission on physical layere.g.

P-SCH Primary Synchronization Channel (for FDD)• P-SCH sends known, invariant signaling sequence of 256 chips• allows UE to synchronize

CPICH Common Pilot Channel• a signaling sequence known to network and UE is spread with the code used in

the P-CCPCH, in which further information is available• allows UE to "backengineer" the code

P- CCPCH Primary Common Control Physical Channel• used by BCCH / BCH• uses code diseminated by CPICH so UE can always listen in

DPDCH Dedicated Physical Data Channel• physical channel dedicated to a user

UMTS Networks and Internet Telephony – Sommersemester 2006 54

Mapping of Channels onto each other

BCCH PCCH DCCH CCCH CTCH DTCH

BCH PCH RACH FACH DSCH DCH

P-CCPCH S-CCPCH PRACH PDSCH DPDCH

Control Plane User Plane

Logical Channels

Transport Channels

PhysicalChannels

UMTS Networks and Internet Telephony – Sommersemester 2006 55

Layer Model for the Radio Link (Uu Interface)Protocols on Uu Interface Channels

Logical ChannelsTransport ChannelsPhysical Channels

Usage Example

Radio Link Signaling

UMTS Networks and Internet Telephony – Sommersemester 2006 56

Usage Example: voice transmission I*

In the Core Network / UE, a voice call is (trans)codedto 4 – 12 kb/s

Bit rate depends on current transmission quality on radio link• High bit rate when transmission quality is good• Lower bitrate when transmission quality bad

-> need more bits for error protectionTranscoded voice bits come in 3 classes A, B and C

Class A most sensitive to transmission errors• Needs more error protection than classes B and C

Hence Class A bits are transmitted in different Transport Channel Transmission attributes described in Transport Format

All Transport Channels for this voice call are multiplexed onto same Physical Channel

* Example taken from “UMTS” by Pierre Lescuyer

UMTS Networks and Internet Telephony – Sommersemester 2006 57

Usage Example: voice transmission II*

* Example taken from “UMTS” by Pierre Lescuyer

DTCH Logical Channel

DCH ATransport Block

DCH B DCH C

Transport Channels

Physical ChannelTFCI A B C

Radio Link Frame

Channel CodingIndicates Transport Formats used to allow decoding

DPDCH

UMTS Networks and Internet Telephony – Sommersemester 2006 58

Summary

Protocols used on UuMAC and RLC on L2 for both control and user plane

PDCP and BMC on L2 additionally for user plane to PS Domain

RRC on L3 for control plane

Each Layer uses Channel to transport dataLogical Channels, Transport Channels, Physical Channels

UMTS Networks and Internet Telephony – Sommersemester 2006 59

Course Overview

MotivationStandardization issuesUMTS architecture basicsUMTS radio link

Physical layerSignaling

UE, UTRAN, PS Domain, CS Domain Basic functionalities:

Accessing the networkTransferring dataDetaching from the networkInformation storage

MobilityQoSSecurity

ChargingUMTS Evolution: from R99 to Rel7Beyond UMTS

UMTS Networks and Internet Telephony – Sommersemester 2006 60

ArchitectureUSIMUE Tasks

User Equipment (UE)

UMTS Networks and Internet Telephony – Sommersemester 2006 61

UE Architecture

UICC (Universal Integrated Circuit Card)User subscription dependent part of the UEContains one or both of

• USIM (Universal Subscriber Identity Module)• ISIM (IMS Subscriber Identity Module)

MT (Mobile´Termination)Terminates radio transmissionAdapts TE capabilities to those of radio transmissionCouples TE and UICC

TE (Terminal Equipment)Provides end-user application functionsTerminates upper layersCommunicates with peer TE on the other end of the communication sessionMay be „non-UMTS entity“ coupled via TAF (Terminal Adaptation Function)

• E.g. Laptop, printer,…

towardsUTRAN

UE Mobile Termination (MT)

RTAF

Terminal Equipment(TE)

USIM ISIMUICC

UMTS Networks and Internet Telephony – Sommersemester 2006 62

UICC

Same concept as SIM card in GSMLittle „plastic card“Identifies User

Identifies how to bill this userUser subscription-dependent part of the UE

Separated from rest of UE • allows separate selling and management of physical equipment and user

subscriptionUnaccessible to user⇒ Creates trusted environment⇒ Key to many commercial applications

Without UICC only emergency calls are possibleTerminal may hold slots for several UICCs

Allows several subscribers to use same terminal• Separate private / business use of one UE• In the future may allow (ad-hoc) networks to access UMTS network

UMTS Networks and Internet Telephony – Sommersemester 2006 63

USIM

USIM contains all user-specific data to enter PS / CS domainIdentities

• USIM identity (IMSI - International Mobile Subscriber Identity)– Unique USIM number

• temporary USIM identities(TMSI for CS Domain, P-TMSI for PS Domain)

– assigned after initial registration– used to protect user identity against eavesdroppers

• users phone number(MSISDN - Mobile Station International ISDN number)

– There can be more than one MSISDN per IMSI

preferred language• used for displaying information

security keyscurrent locationlist of unaccessable networks

UMTS Networks and Internet Telephony – Sommersemester 2006 64

UE Tasks: technology relatedWith Node B

Rate matchingSpreading and modulationPower controlError Correction

With RNCSignaling for connection set-up and releaseSignaling for handoverEncryption / DecryptionMeasurements to detect necessity for handover

• S/N ratio, error rate, signal strength,... Power control

With Core Networkmobility managementsession management

• Connection set-up maintainance and tear-down• Port negotiation• QoS negotiation• …

location managementidentity management

Sending data…

UMTS Networks and Internet Telephony – Sommersemester 2006 65

UE features: user-related

Large displaycamera with MPEG codeclong battery lifetimegaming-capable

fast processor, substantial memory

other user software (web browser,…)small and lightUser API

UMTS Networks and Internet Telephony – Sommersemester 2006 66

Summary

UE is composed of UICC with USIM/ISIM, TE, MT

UICC contains all subscriber-related information

Uu interface towards the UTRAN

UE has to perform a high number of complex tasks

communicating with Node B, RNC and Core Network

UMTS Networks and Internet Telephony – Sommersemester 2006 67

ArchitectureNode BRNC

cf. TS 25.401 "UTRAN overall description",TS 25.301 "Radio Interface Protocol Architecture"

UMTS Radio Access Network (UTRAN)

UMTS Networks and Internet Telephony – Sommersemester 2006 68

UTRAN ArchitectureNode B

responsible for radio transmission / reception in one or more cellsRNC - Radio Network Controller

controls use and integrity of radio resourcescontrols one or more Node Bs

RNS - Radio Network Subsystemcontains one RNC and a set of cells

RNS

RNC

RNS

RNC

Core Network (PS Domain and CS Domain)

Node B Node B Node B Node B

Iups / Iucs

Iur

Iub IubIub Iub

UTRAN

UEUu

Iups / Iucs

cell

UMTS Networks and Internet Telephony – Sommersemester 2006 69

UMTS Radio Access Network (UTRAN)

ArchitectureNode BRNC

cf. TS 25.401 "UTRAN overall description"

UMTS Networks and Internet Telephony – Sommersemester 2006 70

Node B Functionality

Spreading and Modulationcode generationsupports FDD, TDD or both, and CDMA

Terminates Physical Channelsand Transport Channels

Logical Channels terminate at RNCTransport / Physical Channels include error correction

Fast power control ("Inner Loop")Node B measures strengths of received signals and informs UE if it needsto adjustTarget value set by RNC

measures connection quality and strength• handover necessary?

Forwards user traffic

UMTS Networks and Internet Telephony – Sommersemester 2006 71

UMTS Radio Access Network (UTRAN)

ArchitectureNode BRNC

cf. TS 25.401 "UTRAN overall description"

UMTS Networks and Internet Telephony – Sommersemester 2006 72

RNC Functionality I

Radio Resource Managementguarantees stability and „Quality of Service“ (QoS) of radio connection(radio bearer)

Power control ("outer loop")Handover control

• should there be a handover?• decide based on measurements by UE and Node B• signals with UE about handover realization

Admission control and packet scheduling• can a new session be established on the UTRA

without compromising the quality of existing sessions?• Plan channel use, calculate interference and utilisation levels• Configure radio resources accordingly

Code managementMacrodiversity management

UMTS Networks and Internet Telephony – Sommersemester 2006 73

RNC Functionality II

UTRA Controlset-up, maintainance and release ofradio connection (radio bearer)

System information broadcasting• e.g. radio measurement criteria, ...

Initial Access and Signaling Connection set-up and management• synchronization, broadcast of initial scrambling code,...

UTRAN security functions• protects user and control data by encryption and integrity protection

UTRAN level mobility management• informing new cell (Node B) and UE about handover, new channel, etc• Serving RNS relocation

Database handling• stores cell information, and sends it to corresponding Node Bs and UEs

– cell identity, power levels, connection qualities, neighboring cell information (needed for handover)

UE positioning• selects and controls UE positioning method

– using cell ID, round-trip times, "angle-of-arrival", GPS,...

Forwards user traffic

UMTS Networks and Internet Telephony – Sommersemester 2006 74

RNC Functionality III - Relocation

For each UE, one RNC is responsible - Serving RNC (SRNC) typically this is the RNC controlling the cell in which the UE is located

If the UE moves to a cell controlled by a different RNC, this becomes the Drift RNC (DRNC)

control stays with SRNCAlso Macrodiversity may introduce DRNCsSRNC may relocate control to DRNC via Iur

now former DRNC becomes SRNCuseful for optimizing routing (data always travels via SRNC)

SRNC

Core Network

DRNC Iur

Cells

UMTS Networks and Internet Telephony – Sommersemester 2006 75

Illustration

Node Bs RNC

UMTS Networks and Internet Telephony – Sommersemester 2006 76

Summary

UTRAN is home to Node B

• radio transmission / reception in one or more cells

• terminates physical and transport channels

RNC• controls use and integrity of radio resources

• controls one or more Node Bs

• terminates logical channels

• UE controlled by SRNC, however data may also travel via DRNC

Interfaces Uu, Iu, Iub, Iur

UMTS Networks and Internet Telephony – Sommersemester 2006 77

Course OverviewMotivationStandardization issuesUMTS architecture basicsUMTS radio link

Physical layerSignaling

UE, UTRAN, PS Domain, CS Domain Basic functionalities:

Accessing the networkTransferring dataDetaching from the networkInformation storage

MobilityQoSSecurity

ChargingUMTS Evolution: from R99 to Rel7Beyond UMTS

UMTS Networks and Internet Telephony – Sommersemester 2006 78

Packet-switched Domain

ArchitectureSGSN FunctionsGGSN FunctionsProtocols

cf. TS 23.002 "Network Architecture", TS 23.060 "General Packet Radio Service (GPRS)"

UMTS Networks and Internet Telephony – Sommersemester 2006 79

PS Domain Architecture I

Logical architectureSGSN and GGSN perform

• Mobility management• Session management• Location management• Identity management• Service negotiation• User data transport

GfUu Gi

IuGc

Signalling and Data Transfer InterfaceSignalling Interface

UE UTRAN External networks

HLR

Other PLMN

SGSN

GGSN

EIR

SGSN

GnGb

GSM Radio Access

PS Domain

HLR Home Location Register• Subscription information• Master security keys• Location information

EIR Equipment Identity Register• Equipment information

– list of stolen or lost equipment

IMS

UMTS Networks and Internet Telephony – Sommersemester 2006 80

Possible physical architectures

Duplicate nodes for reliabilitySGSN and GGSN may or may not be colocated, there doesn‘t need be a 1:1 relationship

SGSNs and GGSNs of one operatorare connected by an IP-based network

When CS-Domain IP-based can attach MGWs and MSC Servers to samephysical IP backbone as PS domain

PS Domain Architecture II

IP Network

SGSN

GGSN

SGSNSGSN

IP Network

SGSN

GGSNGGSN

MGWSGSN

MSC Sv.

SGSN/GGSN

SGSN

GGSNGGSN

SGSN

UMTS Networks and Internet Telephony – Sommersemester 2006 81

SGSN Functions

Authentication and Authorizationbased on data in HLR

Admission controldoes PS domain have enough resources for supporting a new session?Can negotiate lower QoS

Charging data collectionMobility Management

SGSN may change due to mobilitytemporary storage of data on subscribers attached

e.g. locationRouting

finding the appropriate GGSN through which session leaves for externalnetworks / the IMSestablishes a tunnel (PDP context) to GGSN

UMTS Networks and Internet Telephony – Sommersemester 2006 82

GGSN Functions

Gateway to other packet-based networksprotocol conversionmay act as Policy Enforcement Point (PEP) for the IMSblocking undesired data flows

Routingof data packets to corresponding SGSN / packet-based network

UMTS Networks and Internet Telephony – Sommersemester 2006 83

Protocols - User Plane

RLC

PDCP

MAC

E.g., IP,PPP

Application

RLC

PDCP

MAC

UDP/IP

GTP-U

Relay

UDP/IP

GTP-U

E.g., IP,PPP

SGSNUTRANUEIu-PSUu Gn Gi

GGSN

UDP/IP

GTP-U

UDP/IP

GTP-U

Relay

End-to-end IP layer

IP layer terminating at GGSN

GTP-U: GPRS Tunneling Protocol - User Planetunnels data between SGSN and GGSNs

• hides mobility to upper IP layer• gives network owner control over where traffic leaves its network

UMTS Networks and Internet Telephony – Sommersemester 2006 84

Protocols - Control Plane I

RLC

RRC

GMM /SM / SMS

RRC

MAC

RANAP

Relay

SGSNUTRANUE Iu-PsUu

RLC

SCCP

SignallingBearer

MAC

SignallingBearer

RANAP

SCCP

GMM /SM / SMS

Control Plane between UE and SGSNGMM / SM GPRS Mobility Management / Session Management

• attaching and detaching of UEs, security, location managementRANAP RAN Application Protocol (see CS Domain)SCCP / RANAP part of SS7 protocol stack (see CS Domain)„Signaling Bearer“ either is rest of SS7 protocol stack or an adaptation to run SCCP on top of ATM or IP

UMTS Networks and Internet Telephony – Sommersemester 2006 85

Protocols - Control Plane II

Control Plane for SGSN - GGSN or SGSN-SGSN interfaceGTP-CGPRS Tunneling Protocol for the control plane

• tunnels signaling messages between SGSNs and GGSNs and between SGSNs

UDP

Gn or GpGSN GSN

GTP-C GTP-C

UMTS Networks and Internet Telephony – Sommersemester 2006 86

Protocols - Control Plane III

Control Plane for SGSN - HLR interface (SS7 signaling)MAP (Mobile Application Part)TCAP for managing control connections between two nodes (from GSM)Runs over SCCP / signaling bearer just as RANAP

SCCP SCCP

GrSGSN HLR / EIR

TCAP

MAP

TCAP

MAP

SignallingBearer

UMTS Networks and Internet Telephony – Sommersemester 2006 87

Summary

PS Domain is home to SGSN and GGSN• mobility management• session management• location management• identity management• service negotiation• GGSN is gateway to other packet-based networks• Important interfaces Gi, Gn and Iu

Protocols used on user planeone end-to-end IP layer, and a tunneled IP layer local to thePS domain

tunneling protocol is GTP-U

Protocols used on control planeGMM / SM, SMS, RANAP and SCCP

UMTS Networks and Internet Telephony – Sommersemester 2006 88

Course OverviewMotivationStandardization issuesUMTS architecture basicsUMTS radio link

Physical layerSignaling

UE, UTRAN, PS Domain, CS DomainBasic functionalities:

Accessing the networkTransferring dataDetaching from the networkInformation storage

MobilityQoSSecurity

ChargingUMTS Evolution: from R99 to Rel7Beyond UMTS

UMTS Networks and Internet Telephony – Sommersemester 2006 89

Architecture R99 Architecture Post - Rel4Protocols and SGW

cf. TS 23.002 "Network Architecture", TS 23.205 "Bearer-independent circuit-switched core network"

Circuit-switched Domain

UMTS Networks and Internet Telephony – Sommersemester 2006 90

Logical architectureMSC and GMSC perform

• Mobility management• Session management• Location management• Identity management• Service negotiation• Transcoder control• User data transport

VLR stores• Subscription information• Currently used security keys• Location information

FUu

IuC

Signalling and Data Transfer InterfaceSignalling Interface

UE UTRAN External networks

C, D

HLR/ AuC

MSC / VLR GMSC

EIR

MSC / VLR

E, GA

GSM Radio Access

CS Domain

HLR Home Location Register / AuC• Subscription information• Master security keys• Location information

EIR Equipment Identity Register• Equipment information

– List of stolen or lost equipment

CS Domain Architecture R99

UMTS Networks and Internet Telephony – Sommersemester 2006 91

MSC split into control node and user traffic transport nodeMSC Server

• All MSC signaling functions– Mobility management– Session management– Location management– Identity management– Service negotiation– Transcoder control

• Control of MGW• VLR functionality

FUu

IuC

Signalling and Data Transfer InterfaceSignalling Interface

UE UTRAN

Externalnetworks

C, D

HLR/ AuC

MSC Server GMSC Sv.

EIR

MSC / VLRE, G

AGSM Radio Access

CS Domain

CS Domain Architecture Post-Rel4

NbMGW MGW

McMc IP or

ATM

Media Gateway (MGW)• All MSC transport functions

– User data transport

Signaling Gateway (SGW)• Translates SS7 protocol stack

into IP/ATM-based protocol stack– Location as need be

SGW

UMTS Networks and Internet Telephony – Sommersemester 2006 92

Protocols – User Plane

MGW – MGW and MGW - RNCTwo possibilities depending on transport network technology

• IP – based– RTP Real Time Transport Protocol (accompanied by RTCP (RTP Control Protocol)

• ATM – based– AAL2 offers real-time transport to small packets

NbMGW MGW / RNC

UDP

RTP

Payload

UDP

RTP

Payload

ATM

NbMGW MGW / RNC

AAL2

Payload

ATM

AAL2

Payload

UMTS Networks and Internet Telephony – Sommersemester 2006 93

Protocols – Control Plane, SS7 I

CS Domain to a large extent relies on SS7 protocolsSS7 – Signaling System No. 7

Standard signaling system in telecommunication networksSeparates control signaling network and user network

• E.g. ISDN B-Channels (user) / D- Channel (control)Performs e.g. call set-up / mgmt / tear-down, resource reservation, mobile subscriber authentication, toll-free numbers, call forwarding, conference calls,…

UMTS Networks and Internet Telephony – Sommersemester 2006 94

Protocols – Control Plane, SS7 II

Architectural ElementsSSP – Service Switching Point

• Originate, terminate or tandem calls• Communicates with other SSPs via STPs

STP – Service Transfer Point• Routes signaling messages, e.g. based on “addresses” contained in the message

– Dialed number, mobile subscriber number,…

SCP – Service Control Point• Database

SSPSSP

SSP

STP STP

STP

SCP SCPSCP

UMTS Networks and Internet Telephony – Sommersemester 2006 95

Protocols – Control Plane, SS7 III

SS7 protocol stack in fixed networksMTP Message Transfer Part (Layers 1 – 3)

• reliable message routing between all SS7 nodes – Rerouting around failed links, congestion control, error checking,…

• Offers service to User Parts and Application PartsSCCP Signaling Connection Control Part

• Translates from “user addresses” (telephone numbers etc) into destination point addressTCAP – Transaction Capabilities Application Part

• Non-circuit related signaling, e.g. SCP queriesTUP - Telephone User Part

• Analog call handlingISUP – ISDN User Part

• Set-up, manage and release calls

For mobile networks additional Application Parts are defined

MAP, RANAP, BICC, ALCAP

MTP 1

MTP 2

MTP 3

TUP

SCCP

TCAP ISUP

L5-7

UMTS Networks and Internet Telephony – Sommersemester 2006 96

Protocols - Control Plane IV

Control Plane for MSC (Server) – HLR/EIR/AuC interfaceMAP (Mobile Application Part)

SCCP SCCP

B,C,D,E,F,GMSC (Server) HLR / EIR / AuC

TCAP

MAP

TCAP

MAP

MTP 1-3 MTP 1-3

UMTS Networks and Internet Telephony – Sommersemester 2006 97

Protocols – Control Plane VRNC – MSC / MSC Server

Three possibilities depending on transport network technology• „Full SS7“ / MTP- based (see previous slides)• IP – based

– SCTP / M3UA enable running „SS7“ over IP– RANAP – RAN Application Part

» establishes separate logical connection to each UE for control traffic• ATM – based

– AAL5 offers transport to variable-sized packets– „Signaling Bearer“is an adaptation to run SCCP on top of ATM– ALCAP controls AAL2 of user plane

IucsRNC MSC Sv. IucsRNC MSC Sv.

L2IP

SCTP

M3UASCCP

L2IP

SCTP

M3UA

SCCP

ATMAAL5

Sign. Bearer

ATMAAL5

Sign. Bearer

RANAP RANAP

SCCP

RANAP

SCCP

RANAP

ALCAP ALCAP

UMTS Networks and Internet Telephony – Sommersemester 2006 98

Protocols - Control Plane VI

MSC- MSC and MSC Server – MSC ServerMSC – MSC protocol stack as in ISDNMSC Server – MSC Server protocol stack migrates to „SS7 over IP or ATM“ (ATM not shown)

• BICC - Bearer Independent Call Control

MTP2 MTP2

EMSC MSC

MTP3

ISUP

MTP3

ISUP

MTP1 MTP1

L2 L2

NcMSC Server MSC Server

SCTP

L1 L1

M3UA

BICC

M3UA

BICC

UMTS Networks and Internet Telephony – Sommersemester 2006 99

Summary

CS Domain is home to MSC and GMSC in R99„SS7 Network“

With Rel4 split (G)MSC into MSC Server and MGWSeparation control / user plane Introduce IP or ATM based transport networkControl signaling with „SS7 top“ and IP/ATM baseSGWs translate between pure SS7 signaling and SS7 over IP/ATM

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