Umts

2

Evolution of GSM towards UMTS explained in terms of “generations”:

The entire cellular systems since introduced has

effectively been replaced at times.

These major changes are referred to as a new

“generation” of cellular systems.

The Dream (intention)

› 2G and 2.5G systems are incompatible around the

world.

Worldwide devices need to have multiple technologies

inside of them, i.e. tri-band phones, dual-mode phones

› To develop a single standard that would be

accepted around the world

One device should be able to work anywhere !

› Increased data rate Maximum 2048Kbps

3

“Access to Information from Anyplace, Anytime”

The reality

› Different standards with some operators in

America and the rest of the world

Difficulties

World wide identical available spectrum

Agreement on the encoding/decoding

technique used

4

3G UMTS (Universal Mobile Telecommunications Service) is

a third-generation (3G): broadband, packet-based

transmission of text, digitized voice, video, multimedia at

data rates up to 2 Mbps .

UMTS is based on the Global System for Mobile (GSM)

communication standard. It is also endorsed by major

standards bodies and manufacturers as the planned

standard for mobile users around the world.

Once UMTS is fully available, computer and phone users

can be constantly attached to the Internet wherever they

travel and, as they roam will have the same set of

capabilities. Users will have access through a combination

of terrestrial and satellite transmissions. 5

6

Major difference

– GSM: TDMA and FDMA

– UMTS: Wide-band code division multiple access

(WCDMA)

7

Traffic channels: different

users are assigned

unique code and

transmitted over the

same frequency band,

for example, WCDMA

and CDMA2000

Traffic channels: different frequency

bands are allocated to different users ,

for example, AMPS and TACS

Traffic channels: different time

slots are allocated to different

users, for example, DAMPS and

GSM

Power

Power

Power

FDMA

TDMA

CDMA

8

Defect

1. Simple Implementation 1. Frequency Reuse

2. privacy

1. Need synchronized of

frame

1. Reduction the interference

2. Diversity Hand-over

3. Privacy

1. Sophisticated power

control for mobile

1.Privacy

Advantage

FDMA

TDMA

CDMA

AMPS, TACS

GSM, PDC

IS95,

W-CDMA

Defect

9

Multiple access method DS-CDMA (DS: Direct Spread)

Duplexing methodFDD/TDD (Frequency Division Duplex/Time Division

Duplex)

Inter-cell synchronization Asynchronous

Bandwidth 5 MHZ

Chip rate 3.84 Mcps

Carrier spacing Flexible with 100/200kHz

Frame length Unit 10 ms

Data modulation Downlink: QPSK, Uplink: BPSK

Multi-rate concept Variable spreading factor

Maximum data rate 2 Mbps (indoor)/384 kbps (mobile)

Channel codingConvolution coding

Turbo code for High data rate

BPSK: Binary phase shift keying QPSK: Quadrature phase shift keying

10

UMTS

UMTS-FDD UMTS-TDD

11

FDD (Frequency Division Duplex)

TDD (Time Division Duplex)Base stationMobile Terminal

Base stationMobile TerminalUp Down

TS TS

TS: Time slot

Intended Data Rates

› Actual data rates will be effected by

Interference (other devices, background, buildings)

Amount of other traffic

The speed that the device is moving

Maximum movement speed for high date rate

is 10 Kmph

a fast walker will lose this rate.

12

› Macro Cell These cover a large area and will give slow access.

144 Kbps – max speed of 500 Km/h.

Low data rate.

› Micro Cell These should cover a medium area.

384 Kbps max speed 120 Km/h.

Medium data rate.

› Pico Cell Less than 100 metres.

2 Mbps – max speed of 10 Km/h.

High data rate.

Difficult to predict› Actual distances and bandwidth depend on local conditions

13

Types of Cells and Base station to use them

› Cells will operate in a hierarchy overlaying each

other

14

Satellite

Macro-CellMicro-Cell

Urban

In-Building

Pico-Cell

Global

Suburban

15

Cell breathing

16

17

In UMTS cell size is tightly interrelated with its capacity› Cell breathing describes a constant change of the range of a

geographical area covered by a Node B cell based on the amount of traffic currently using that transmitter. When a cell becomes heavily loaded, it shrinks. Subscriber traffic is then redirected to a neighboring cell that is more lightly loaded, which is called load balancing.

Interference increases noise in signal

› UE on the cell edge is transmitting with max power

› Another UE becomes active – results in increased interference

› The received signal from the UE on the cell edge is too weak and communication becomes impossible

› Restriction of participants needed

› Effective cell size decreases with increasing number of users

› There is a trade-off between capacity and coverage› Results in cell breathing and imposes greater difficulties on

network planning

18

19

FDD

20

General Core Network ArchitectureThe UMTS Core Network (CN) can be seen as the basic platform for all communication services provided to the UMTS subscribers

The CN is functionally further divided into two domains:circuit switched domain(CS) and packet switched domain (PS)

1-Circuit Switched CN:The CS domain refers to the set of all CN entities offering a “CS type

connection”.

2-Packet-Switched CN:the PS domain offers "PS type connection", which transports the user information using autonomous concatenation of bits called packets. The information is split into separated but related packets before being transmitted and is reassembled at the receiving end.

21

USIM

ME

Node B

Node BRNC

Node B

Node B

RNC

MSC/VLR

GMSC

SGSN GGSN

HLR

UTRAN CNUE

Exte

rn

al N

etw

orks

Cu

Uu

Iu

IubIur

General Core Network Architecture

22

Mobile switching center

Serves ME at its current location for circuit switch service

MSC

Gateway MSC

Serves UMTS where it is connected to ext .CS NW

GMSC

Home Location Register

The database storing the master copy of a users profile

HLR

Visitor Location Register

The database holding a copy of a visiting users profile .

VLR

Gateway serving GPRS support node

the node that is accessed by the packet data network it contains routing

information for PSattached users.

GGSN

Serving GPRS Support Node (SGSN)

Router for Packet Switched Services .

SGSN

3G base station

Handles radio channel,multiplexing,demultilexing of data & voice

Node B

Radio RN controller

Controls & manages multiple base stations

RNC

23

There are four major new interfacesdefined in UMTS:

• Iu

The interface between UTRAN and the CN

• Iur

The Interface between different RNCs

• Iub

The interface between the Node B and the RNC

• Uu

The air interface

• Logical channel: an information stream dedicated to the transfer of a specific type of information

• Transport channel: described by how data are transferred

• Physical channel: defined by the frequency, phase (I,Q) and code

24

• Control channels (C-plane information)

– Synchronisation Control Channel (DL)

– Broadcast Control Channel (DL)

– Paging Control Channel (DL)

– Common Control Channel (UL&DL)

– Dedicated Control Channel (UL&DL)

– Shared Control Channel

– ODMA Dedicated Control Channel

• Traffic channels (U-plane information)

– Dedicated Traffic Channel (DL&UL)

– ODMA Dedicated Traffic Channel

– Common Traffic CHannel

25

Physical layer provides data transport support to

higher layers via Transport Channels

› Rate Matching/ Dematching.

› Multiplexing/ Demultiplexing different Transport Channels into/from a Coded Composite Transport Channel (CCTRCH).

› Mapping/ Demapping of CCTRCH into/from Physical Channels.

› Modulation and Spreading / Demodulation and Despreading.

› Power Weighting and combining of physical channels.

› RF Processing.

› Error detection.

› Encoding/decoding.

26

1st Step: Channelization Variable Rate Spreading ( According to user data rate)

Transmissions from a single source are separated by Channelization codes:

• Based on OVSF technique (Orthogonal Variable Spreading Factor)

• Allows spreading to be changed while maintaining orthogonality

between codes

› 2nd Step: Scrambling Code

Gold sequence code of length : 2^(24)-1

needed to separate terminals or base stations from each other27

S

Channelization

Code

Scrambling

Code

3840 KcpsCoding

&

Interleaving

DATA

28

Downlink (Node B to UE ) Scrambling Code: Identifies cell (sector).

Channelization Code: Identifies user channels in cell (Sector).

Scrambling Code A

Scrambling Code B

Scrambling Code C

ChannelizationCode 1

ChannelizationCode 2 Channelization

Code 3

ChannelizationCode 1 Channelization

Code 2

ChannelizationCode 2

ChannelizationCode 1

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Up Link (UE to Node B )Scrambling Code: Identifies user terminal.

Channelization Code: Identifies channels in user terminal.

Scrambling Code A

Scrambling Code B

Scrambling Code C

ChannelizationCode 1

ChannelizationCode 1

ChannelizationCode 1

30

31

User-A

A

Code 1

User-B

B

Code 2

User-C

C

Code 3

User-A

A

Code 1

User-B

B

Code 2

User-C

C

Code 3

De-spreading

Code

Narrow BandSignal

Wide BandSignal

(Multiple Signal)Spreading DespreadingNarrow Band

Signal

C

B

A

(Receiver A)

(Receiver B)

(Receiver C)

001encoder

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

010encoder

11-1-1 -1-111 11-1-1 -1-111

110encoder

1-1-11 1-1-11 1-1-11 -111-1 -1 -1 -1 3 1 1 -3 1 -1 -1 3 -1

32

decoder

11-1-1

1-1-11

1-11-1-4 -4 4

-4 4 -4

4 4 -4

001

010

110

decoder

decoder

-1-1-13 11-31 -1-13-1

-1-1-13 11-31 -1-13-1

-1-1-13 11-31 -1-13-1

-1 -1 -1 3 1 1 -3 1 -1 -1 3 -1

33

A B C

A B C

ABC

Rake

34

RX

Searcher

Combiner

Calculation

Combined Signal

RAKE Receiver

Electric PowerElectric

Power

Delay Profile

Delay Time

Multiple Signal 1

Multiple Signal 2

Multiple Signal 3

Delay Time

Finger Circuit

Finger Circuit

Finger Circuit

Output Power

35

36

Open loop techniques are used during the initial access before communication between the UE and node B has

been fully established. It simply operates by making a

measurement of the received signal strength and thereby

estimating the transmitter power required. As the transmit

and receive frequencies are different, the path losses in

either direction will be different and therefore this method

cannot be any more than a good estimate.

Closed loop techniques Once the UE has accessed the system and is in communication with the node B, closed loop

techniques are used. A measurement of the signal strength is

taken in each time slot. As a result of this a power control bit

is sent requesting the power to be stepped up or down. This

process is undertaken on both the up and downlinks. 37

The basic mean of handover is to provide

the continuous connection when moving

among cells.

Any failures within the UMTS handover (or

UMTS handoff) procedure will lead to

dropped calls which will in turn result in user

dissatisfaction and ultimately it may lead to

users changing networks.

There are three types :

› Hard handover

› Soft handover

› Softer handover 38

Hard handover is applied when the user’s

equipment communicates with only just one

Node B. Connection with the old Node B is broken

before the new connection is established.

Handover is executed after the signal strength

from neighbor’s cell exceeding the signal strength

from the current cell

39

Soft handover occurs when a UE is in the

overlapping coverage area of two cells. Links to the

two base stations can be established simultaneously

and in this way the UE can communicate with two

base stations. By having more than one link active

during the handover process.

40

In the downlink direction. In the mobile station the

signals received from the two different base

stations are combined using Rake receiver. In the

uplink direction the received signals are routed to

the RNC. in the RNC the two signals are compared

on a frame-by-frame basis and the best candidate

is selected.

after each interleaving period; i.e. every 10, 20, 40

or 80ms. As the outer loop power control algorithm

measures the SNR of received uplink signals at a

rate between 10 and 100Hz, this information is used

to select the frame with the best quality during the

soft handover

41

similar to soft handover. The main difference

between these two handovers that a UE is located

in the coverage area of two sectors of one Node B

.the Node B combines the data from more than

one cell to obtain good quality data from the UE.

42

in the uplink, the signals received by the Node B,

the signals from the two sectors can be routed to

the same RAKE receiver and then combined to

provide an enhanced signal.

In the downlink, the different sectors of the Node B

use different scrambling codes. To overcome this,

different fingers of the RAKE receiver apply the

appropriate de-spreading or de-scrambling codes

to the received signals. Once this has been done,

they can be combined as before.

43

What is QOS?

› Quality of Service (QOS) is the mechanism insuring that a service

can be delivered to the end user in an acceptable time-frame

and that the service properties are stable over time within

predefined boundaries.

› QOS a the total outcome of the service performance,

measured in terms of speed, accuracy and reliability.

› From the network point of view QOS refers to the capability to

provide different network services to different network traffic.

› Different services translate into different characteristics for the

network flows, for example: bandwidth, error ratio, delay

› QOS does not create additional network resource - it does not

create additional bandwidth for example - but allow for the existing network resources to be managed in order to provide

predictable parameters for network resource

44

Figure 1: End-to-end connectivity

possibilities.

Two Terminal Equipment (TE) could use

just the Wireless and UMTS domain to

communicate, like in case [A], or the

external network domain could be

involved, like in case [B] .

45

• The end user could be a terminal or even another 3G network. The end-to-end QOS UMTS requirement implies that QOS management is needed in all involved domains: wireless domain, IP core, external IP network.